blue boxes summary

8/13/2019 Blue Boxes Summary

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Anatomy Exam 1Blue Boxes

CRANIUM(822-842)

Head Injuries

Complications: hemorrhage, infection, injury to brain and cranial nerves Most common symptom: disturbance in level of consciousness Account for 10% of US deaths; 50% of traumatic deaths involve brain injury Occur mostly ages 15-24; vehicle and motorcycle accidents are prominent causes

Headaches and Facial Pain

Usually benign and associated with tension, fatigue, or mild fever May indicate more serious intracranial problem: brain tumor, subarachnoid hemorrhage, meningitis Neuralgiacharacterized by severe throbbing or stabbing pain in the course of a nerve

o caused by a demyelinating lesiono common cause of facial paino facial neuralgia diffuse painful sensations, as opposed to localized aches which have

specific names: odontalgiatoothache; otalgiaearache

Injury to Superciliary Arches

Blow to these relatively sharp bony ridges (e.g., boxing) may lacerate skin and cause bleeding Black eye- bruising of skin surrounding orbit causes tissue fluid and blood to accumulate in the

surrounding connective tissue

Malar Flush

Redness of skin covering the zygomatic prominence (malar eminence) Associated with fever and diseases such as tuberculosis and systemic lupus erythematosus disease

Fractures of the Maxillae and Associated Bones

Le Fort I fracturehorizontal fracture of maxillae, passing superior to maxillary alveolar process,crossing bony nasal septum and possibly pterygoid plates of sphenoid (i.e., horizontal line under noseand above maxillary tooth roots)

Le Fort II fracturefrom posterolateral parts of maxillary sinuses through the infra-orbital foramina,lacrimals, or ethmoids to the bridge of the nose (i.e., central part of face, including maxillary alveolar

processes, is separated from rest of cranium)

Le Fort III fracturehorizontal fracture through superior orbital fissures, ethmoid, and nasal bones andextends laterally through the greater wings of the sphenoid and the frontozygomatic sutures (i.e.,

maxillae and zygomatic bones separate from rest of cranium)

Fractures of the Mandible

Usually involves two fractures on opposite sides of the mandible Fractures of coronoid processuncommon and usually single Fractures of neck of mandibleusually transverse and associated with dislocation of TMJ on same side Fractures of angle of mandibleusually oblique and may involve the socket of the 3rdmolar Fractures of body of mandiblefrequently pass through the socket of the canine

Resorption of Alveolar Bone

Following extraction, the sockets begin to fill in with bone and the alveolar process begins to resorb Mental foramina may disappear in the process, exposing the mental nerves to injury or causing pain

when pressure is placed on the exposed nerve by a denture during eating

Edentulism results in decreased vertical facial dimension and mandibular prognathism(overclosure)


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Fractures of Calvaria

Depressed fracturesbone fragment is depressed inward, compressing the brain, as a result of a hardblow to the thin area of the calvaria

Linear calvarial fracturesmost frequent type, occur at point of impact but fracture lines radiate awayfrom it in two or more directions

Comminuted fracturesbone is broken into several pieces Contrecoup (counterblow) fractureno fracture occurs at point of impact (thicker calvaria) but

fracture occurs on the opposite side of cranium (force transmitted to thinner calvaria)Surgical Access to Cranial Cavity: Bone Flaps

Craniotomysection of neurocranium (bone flap) is elevated or removed Adult pericranium has poor osteogenic properties so little regeneration occurs after bone loss Reintegration of surgically produced bone flaps are most successful when bone is reflected with

overlying muscle and skin so it retains its own blood supply during the procedure and after

repositioning

Craniectomybone flap not replaced by bone but instead by plastic or metal plateDevelopment of Cranium

Intramembranous ossificationbones of calvaria and some parts of cranial base Endochondral ossificationmost parts of cranial base Newborns: facial skeleton forms 1/8 of cranium; Adults: facial skeleton forms 1/3 of cranium Sutures in newborn cranium:

o Frontal sutureseparates halves of frontal bone Metopic suturepersistence of remnant of frontal suture (beyond 8 years of age)

o Coronal sutureseparates frontal and parietal boneso Intermaxillary sutureseparates maxillaeo Mandibular symphysisseparates mandibles

No mastoid processes at birth: facial nerves are close to the surface when they emerge from thestylomastoid foramina and can be easily injured by forceps during difficult delivery

Fontanellesmembranous intervals separating the bones of the calvaria of a newborno Anterior fontanellelargest, diamond shaped, bounded by halves of frontal bone anteriorly

and parietal bones posteriorly (junction of sagittal, coronal, and frontal suturesthe future

site of bregma)o Posterior fontanelletriangular, bounded by parietal bones anteriorly and occipital bone

posteriorly (junction of lambdoid and sagittal suturesfuture site of lambda)

o Sphenoidal and Mastoid fontanellesoverlain by temporal muscle, fuse during infancy Halves of mandible fuse early in 2ndyear; two maxillae and nasal bones usually do not fuse Softness of cranial bones and their loose connections at sutures and fontanelles enable the shape of

the calvaria to change during passage through birth canal: halves of frontal bone flatten, occipital bone

drawn out, one parietal bone slightly overrides the other

Increase in size of calvaria is greatest during first two years (most rapid brain development)Age Changes in Face

Mandible is most dynamic of facial bones:o

Newborn mandible consists of two halves united by cartilaginous join (mandibular symphysis)o Fibrocartilage union begins during 1styear, halves are fused by end of 2ndyearo Body of mandible is a shell, lacking alveolar processes, enclosing deciduous teetho Body of mandible elongates to accommodate tooth development

Rapid growth of face during youth coincides with eruption of deciduous teeth, vertical growth of upperface results mainly from dentoalveolar development

Enlargement of frontal and facial regions associated with increase in size of paranasal sinusesObliteration of Cranial Sutures

Obliteration of sutures between calvarial bones usually begins between age 30-40 on the internalsurface and approximately 10 years later on the external surface

Obliteration begins at bregma and continues sequentially in sagittal, coronal, and lambdoid sutures


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Age Changes in Cranium

With age, cranial bones become progressively thinner and lighter Diplo gradually become filled with gray gelatinous material as bone marrow loses blood cells and fat

Craniosynostosis and Cranial Malformations

Primary craniosynostosispremature closure of cranial sutures that results in cranial malformations Occurs 1 in 2000 births, more common in males, cause is unknown but genetic factors important Prevailing hypothesis: abnormal development of the cranial base creates exaggerated forces on the

dura mater that disrupt normal cranial sutural development Scaphoncephalypremature closure of sagittal suture, anterior fontanelle small or absent, results in

long, narrow, wedge-shaped cranium

Plagiocephalypremature closure of coronal or lambdoid suture on one side only, results in twistedand asymmetrical cranium

Oxycephalypremature closure of coronal suture, results in a high, tower-like cranium (more commonin females)

VERTEBRAE(456-460 only those related to cervical vertebrae)

Vertebral Body Osteoporosis

Common metabolic bone disease detected during routine radiographs Results from net demineralization of bones caused by disruption of normal balance of calcium

deposition and resorption

Most affected areas: bodies of vertebrae (mostly thoracic), neck of femur, metacarpals, radius Especially affects the horizontal trabecule of spongy bone of vertebral body. Vertical striping results,

reflecting the loss of the horizontal supporting trabeculae and thickening of vertical struts

Later stages may reveal vertebral collapse and increased thoracic kyphosisLaminectomy

Surgical excision of one or more spinous processes and the adjacent supporting vertebral laminae Also denotes removal of most of the vertebral arch by transecting the pedicles Used to gain access to the vertebral canal, providing posterior exposure of spinal cord and/or roots of

specific spinal nerves

Often performed to relieve pressure on spinal cord or nerve roots as caused by a tumor, herniateddisc, or bony hypertrophy

Dislocation of Cervical Vertebrae

Cervical vertebrae less tightly interlocked than other vertebrae due to more horizontally orientedarticular facets and thus can be dislocated in neck injuries with less force than required for fracture

Because of large vertebral canal in cervical region, slight dislocation can occur without damage to thespinal cord (severe dislocations or fracture-dislocations will injure the spinal cord)

The dislocated cervical vertebra may self-reduce (slip back in place) if dislocation doesnt result infacet jumping with locking of the displaced articular processes

Fracture and Dislocation of Atlas

Because the taller side of the lateral mass of C1 is directed laterally, vertical forces (e.g., strikingbottom of pool when diving) compressing the lateral masses between the occipital condyles and the

axis drive them apart, fracturing one or both of the anterior or posterior arches Jefferson fracture- if force is sufficient, rupture of transverse ligament will also occur, not necessarily

causing spinal cord injury because the dimension of the bony ring actually increases

Fracture and Dislocation of Axis

Fractures of vertebral arch of axis are one of the most common injuries of the cervical vertebrae Traumatic spondylolysis of C2- fracture occurs in thepars interarticularis(bony column formed by

superior and inferior articular processes of the axis), as a result of hyperextension of head on the neck

(as opposed to combined hyperextension of head and neck which results in whiplash)

Such hyperextension of head on neck was used to execute by hanging and thus is also called ahangmans fracture


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More serious injuries may cause body of C2 to be displaced anteriorly with respect to the body of C3,with injury of the spinal cord and/or brainstem likely, sometimes resulting in quadriplegiaor death

Fractures of the densare also common axis injuries which may result from a horizontal blow to thehead or as a complication of osteopenia(pathological loss of bone loss)

Cervical Ribs

Developmental costal element of C7 which normally becomes a small part of transverse process thatlies anterior to the transverse foramen becomes abnormally enlarged in 1-2% of people

May be small protruberance or may be a complete rib Thoracic outlet syndrome- supernumerary rib or a fibrous connection extending from its tip to the first

thoracic rib may put pressure on structures that emerge from superior thoracic aperturesubclavian

artery or inferior trunk of brachial plexus

VERTEBRAL COLUMN(474-482 focus on cervical region)

Aging of Intervertebral Discs

Nuclei pulposi dehydrate, lose elastin and proteoglycans, and gain collagen, resulting in loss of turgor,increased stiffness, and increased resistance to deformation

As the nucleus dehydrates, the two parts of the disc appear to merge as the distinction betweennucleus pulposus and annulus fibrosis becomes increasingly diminished. Nucleus becomes dry and

granular, and may disappear altogether, thus placing increased load on the annulus fibrosis

Intervertebral discs actually increase in size with age, reason for slight loss of height with aging is dueto superior and inferior surfaces of vertebral bodies becoming shallow concavities (?)

Disc narrowing (especially if more narrow than a superior disc) suggests pathology, not normal agingHerniation of Nucleus Pulposus

Herniation of nucleus pulposus through the annulus fibrosis is well-recognized cause of lower backpain and lower limb pain

Discs are strong in young people (vertebrae often fracture before discs rupture) and have great turgordue to high water content

Flexion of vertebral column squeezes the nucleus pulposus further posteriorly toward the thinnest partof the annulus fibrosus, and may herniate into the vertebral canal and compress the spinal cord or the

nerve roots of the cauda equine

Herniations usually extendposterolaterallywhere the annulus fibrosus is not supported by anterior orposterior longitudinal ligaments

Acute painresults from pressure on longitudinal ligaments and local inflammation Chronic painresults from compression of spinal nerve roots and is usually referred to dermatome Hyperflexion of the cervical regionsuch as in head-on collision, may rupture the disc posteriorly

without fracturing the vertebral body, compressing the nerve exiting at that level (rather than the level

below as in the lumbar region) however, cervical spinal nerves exit superior to the vertebra of the

same number so the relationship is the same.

Most commonly ruptured cervical discs: C5-C6 and C6-C7, compressing spinal nerve roots C6 and C7Fracture of Dens

Transverse ligament of the atlas is stronger than the dens of the axis Most common dens fracture occurs at its base, which are often unstable because the transverseligament of the atlas becomes interposed between fragments and because the dens no longer has a

blood supplyresulting in avascular necrosis

Also common are fractures of the vertebral body inferior to base of dens, which heals more readilybecause of retained blood supply

Rupture of Transverse Ligament of Atlas

Atlanto-axial subluxationwhen transverse ligament of atlas ruptures, the dens is set free, resulting inincomplete dislocation of the median antlanto-axial joint

Pathological softening of the transverse and adjacent ligaments (usually disorders of connective tissue)may also cause atlanto-axial subluxation (20% of Down syndrome show laxity/agenesis of ligament)


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Dislocation due to transverse ligament rupture is more likely to cause spinal cord compression thanthat resulting from fracture of dens (in this case the dens is held to the atlas by the transverse

ligament)

Compression of the spinal cord between the posterior arch of the atlas and the dens can causequadriplegia or death

Steeles Rule of Thirdsapproximately 1/3 of atlas ring is occupied by dens, 1/3 occupied by spinalcord, and 1/3 occupied by fluid-filled space and tissues surrounded the cord

Rupture of Alar Ligaments Alar ligaments are weaker than transverse ligament of the atlas and combined flexion/rotation of the

head may tear one or both alar ligaments

Rupture of alar ligament results in 30% increase in range of movement to the contralateral sideFractures and Dislocations of Vertebrae

Crushor Compressionfracturefracture of body of one or more vertebrae caused by sudden forcefulflexion (e.g., car wreck, blow to back of head)

Hyperextension injury of the neckinjury caused by sudden forceful extension of neck (e.g.,headbutting, football illegal block)

Severe hyperextension of the neck(i.e., whiplash)anterior longitudinal ligament stretched or may betorn (e.g., rear-end collision), may also rupture annulus fibrosus of C2-C3, thus separating the cranium,

C1, and dens and body of C2 from the rest of the axial skeleton, usually severing the spinal cord

Hyperflexion injurymay occur as the head rebounds from severe hyperextension Most common causes of cervical region vertebral fractures: football, diving, falls from horses, vehicle

collisions

Injury and Disease of Zygapophyseal Joints

Zygapophyseal joints are close to the intervertebral foramina through which the spinal nerves emergefrom the vertebral canal

When these joints are injured or develop osteophytes(osteoarthritis), the spinal nerves are oftenaffected, causing pain along dermatomal distribution pattern and myotomal muscle spasms

Abnormal Curvatures of Vertebral Column

Excessive kyphosisabnormal increase in thoracic curvature (humpback) Excessive lordosisanterior tilting of pelvis (hollow back) Scoliosisabnormal lateral curvature

BONES OF NECK(985)

Cervical Pain

Several causes: inflamed lymph nodes, muscle strain, protruding intervertebral discs Enlarged cervical lymph nodes may be indicative of malignant tumors of head or thorax/abdomen

(e.g., lung cancer may metastasize through the neck to the cranium)

Most chronic cervical pain is caused by bony abnormalities (e.g., cervical osteoarthritis) or by traumaInjuries of Cervical Vertebral Column

Fractures and dislocations may injure the spinal cord and/or the vertebral arteries and sympatheticplexuses passing through the foramina transversaria

Fracture of Hyoid Bone Occurs in people who are manually strangled by compression of the throat, resulting in depression of

the body of the hyoid onto the thyroid cartilage

Inability to elevate the hyoid and move it anteriorly beneath the tongue makes swallowing andmaintenance of the separation of the alimentary and respiratory tracts difficult and may result in

aspiration pneumonia


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CRANIAL CAVITY AND MENINGES(874-877)

Fracture of Pterion

Can be life threatening because pterion overlies the anterior branches of themiddle meningeal vessels,which lie in grooves on the internal aspect of the lateral wall of the calvaria

Hard blow to the side of the head may fracture the thin bones forming the pterion, and the resultinghematomaexerts pressure on the underlying cerebral cortex

Untreatedmiddle meningeal artery hemorrhagemay cause death within a few hoursThrombophlebitis of Facial Vein

An infection of the face may spread to the cavernous sinus and pterygoid venous plexus, possible dueto the following connections of the facial vein:

o To the cavernous sinusthrough the superior ophthalmic veino To thepterygoid venous plexusthrough the inferior ophthalmic and deep facial veins

Because the facial vein has no valves, blood may pass through it in the opposite direction Thrombophlebitis of the facial veininflammation of the facial vein with secondary thrombus (clot)

formation, which may lead to pieces of the infected clot extending into the intracranial venous system,

producing thrombophlebitis of the cavernous sinus

Infection of the facial veins spreading to the dural venous sinuses may result fromlacerations of the nose or can be initated by squeezing pimples (seriously.) on the side

of the nose and upper lip

This triangular area from the upper lip to the bridge of the nose is considered thedanger triangle of the face, due to the risk of facial vein infection

Blunt Trauma to Head

Blow to the head can detach the periosteal layer of dura mater from the calvaria without fracturingthe cranial bones

Fracture of the cranial base usually tears the dura, resulting in leakage of CSF, because here the twodural layers are firmly attached and difficult to separate from the bones

Dural border cell layerinnermost part of the dura, composed of flattened fibroblasts that areseparated by large extracellular spaces, is a plane of weakness at the dura-arachnoid junction

Tentorial Herniation

Tentorial notch- opening in the tentorium cerebella for the brainstem Space-occupying lesions, such as tumors in the supratentorial compartment, can result in increased

intracranial pressure and may cause part of the adjacent temporal lobe of the brain to herniated

through the tentorial notch

During such tentorial herniation, the temporal lobe may be lacerated by the tough tentoriumcerebella, and the oculomotor nerve may be stretched and/or compressed

Oculomotor lesionsmay result in paralysis of extrinsic eye muscles supplied by CN IIIBulging of Diaphragma Sellae

Pituitary tumors may extend superiorly through the aperture in the diaphragma sellae or cause it tobulge, often expanding the diaphragma sellae which disturbs endocrine function

Superior extension of a tumor may cause visual symptoms owing to pressure on the optic chiasm,where the optic nerve fibers cross

Occlusion of Cerebral Veins and Dural Venous Sinuses May result from thrombi, thrombophlebitis, or tumors Most frequently thrombosed dural venous sinuses: transverse, cavernous, and superior sagittal Cavernous sinus thrombosisusually results from infections in the orbit, nasal sinuses, and superior

part of the face (i.e., the danger triangle)

Thrombophlebitis of the cavernous sinus(remember this is often caused by thrombophlebitis of thefacial vein) usually involves only one sinus but may spread to the opposite side through the

intercavernous sinuses

Thrombophlebitis of the cavernous sinus may affect the abducent nerve as it traverses the sinus andmay also affect the nerves embedded within the lateral wall of the sinus


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Acute meningitisoften develops as a result of septic thrombosis of the cavernous sinusMetastasis of Tumor Cells to Dural Venous Sinuses

The basilar and occipital sinuses communicate through the foramen magnum with the internalvertebral venous plexuses

Because these are valveless, compression of the thorax, abdomen, or pelvis (e.g., coughing or heavystrain) may force venous blood from these regions into the internal vertebral venous system, and from

it into the dural venous sinuses

Thus, this provides a pathway for tumor cells in these regions to spread to the brainFractures of Cranial Base Fractures of the cranial base risk tearing of the internal carotid artery, producing an arteriovenous

fistulawithin the sinus, in which case arterial blood rushes into the cavernous sinus, enlarging it and

forcing retrograde blood flow into its venous tributaries, especially the ophthalmic veins

Results in exophthalmos(the eyeballs can pulsate along with the radial pulse,pulsating exophthalmos)and chemosis(engorged conjunctiva)

CN III, IV, V, and VI lie in or close to the lateral wall of the cavernous sinus and thus may be affectedwhen the sinus is injured

Dural Origin of Headaches

Pulling on arteries at the cranial base or veins near the vertex where they pierce the dura can causepain (dura is pain sensitive)

Distension of the scalp or meningeal vessels may be a cause of headaches (many headaches appear tobe dural in origin, such as the headache after spinal puncture for CSF removal)

Leptomeningitis

Inflammation of the leptomeninges(arachnoid and pia) resulting from pathogenic microorganisms Infection and inflammation usually confined to subarachnoid space and the arachnoid-pia Bacteria may enter subarachnoid space through the blood (septicemia) or spread from an infection of

the heart, lungs, or other viscera; or from a compound cranial fracture or a fracture of nasal sinuses

Acute purulent meningitiscan result from infection with almost any pathogenic bacteriaHead Injuries and Intracranial Hemorrhage

Extraduralor epiduralhematomafollowing a blow to the head, blood from torn branches of a middlemeningeal artery may collect between the external periosteal layer of the dura and the calvaria

Typically a brief concussion occurs, followed by short lucid interval, drowsiness, and eventual coma Dural border hematomaaka subdural hematomausually caused by extravasated blood that splits

open the dural border cell layer, creating a blood-filled space at the dura-arachnoid junction

Dural border hemorrhageusually follows a blow to the head that jerks the brain inside the craniumand injures it, commonly resulting from tearing a superior cerebral vein

Subarachnoid hemorrhageextravasation of blood, usually arterial, into the subarachnoid space, mostlikely a result of rupture of a saccular aneurysm(sac-like dilation on side of artery such as the internal

carotid)

CRANIAL NERVES (1078-1082)

Cranial Nerve Injuries

Injury to the cranial nerves is a frequent complication of a fracture in the base of the cranium Excessive movement of the brain within the cranium may tear or bruise cranial nerve fibers, esp CN I Because of fixed positions and often close relationships to bony or vascular formations, intracranial

portions of cranial nerves are subject to compression from tumor or aneurysm, in which case the

symptom onset occurs gradually and the effects depend on the extend of the exerted pressure

Because of their close relationship to the cavernous sinus, CN III, CN IV, CN V1, and especially CN VI aresusceptible to compression or injury related to pathologies affecting the sinus

See Table 9.6 Summary of Cranial Nerve Lesions (though he will probably ask from the specificexamples given next)


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OLFACTORY NERVE

AnosmiaLoss of Smell

Elderly often have reduced sensation of smell, resulting from progressive reduction in the number ofolfactory receptor neurons in the olfactory epithelium

Most people with anosmia state their chief complaint is loss or alteration of taste Allergic rhinitisinflammation of the nasal mucous membrane, can cause transitory olfactory

impairment In severe head injuries, the olfactory bulbs may be torn away from the olfactory nerves, or someolfactory nerve fibers may be torn as they pass through afractured cribriform plate If all nerve bundles on one side are torn, a complete loss of smell will occur on that sideso anosmia

can signal fracture of the cranial base and CSF rhinorrhea(leakage through the nose) Tumor and/or abscess in the frontal lobe of the brain or a tumor of the meninges (meningioma) in the

anterior cranial fossa may also cause anosmia by compressing the olfactory bulb and/or tractOlfactory Hallucinations

False perceptions of smell that may accompany lesions in temporal lobe of the cerebral hemisphere Lesion that irritates the lateral olfactory area deep to the uncus may cause temporal lobe epilepsyor

uncinate fits characterized by imaginary disagreeable odors and involuntary lip/tongue movement

OPTIC NERVE

Demyelinating Diseases and Optic Nerves

Because the optic nerves are actually CNS tracts, the myelin sheath that surrounds the sensory fibersfrom the point at which the fibers penetrate the sclera is formed by oligodendrocytes rather than

Schwann cells

Consequently, the optic nerves are susceptible to the effects of CNS demyelinating diseases (e.g., MS)which usually do not affect other nerves of the PNS

Optic Neuritis

Lesions of the optic nerve that cause diminution of visual acuity Optic neuritis may be caused by inflammatory, degenerative, demyelinating, or toxic disorders Toxic substances that may injure optic nerve: methyl/ethyl alcohol, tobacco, lead, mercury

Visual Field Defects

Result from lesions that affect different parts of the visual pathway, where the type of defect dependsupon where the pathway is interrupted (Fig B9.1 p 1080):

o Section of an optic nerve results in blindness in the temporal and nasal visual fields of theipsilateral eye

o Section of the optic chiasm reduced peripheral vision and results in bitemporal hemianopsia,the loss of vision in half of the visual field of each eye

o Section of the right optic tract eliminates vision from the left temporal and right nasal visualfields (contralateral homonymous hemianopsiavisual loss is in similar fields) This is the most

common form of visual field loss and is often observed in patients with strokes.

Defects of vision caused by compression of the optic pathway (e.g., tumors of pituitary or aneurysmsof the internal carotid) may produced only part of the visual losses described above

OCULOMOTOR NERVE

Injury to the Oculomotor Nerve

Lesion of CN III results in ipsilateral oculomotor palsywhich affects most of the ocular muscles, thelevator palpebrae superioris, and the sphincter papillae:

o superior eyelid droops and cannot be raised voluntarily because of the unopposed activity ofthe orbicularis oculi

o pupil is fully dilated and non-reactive because of the unopposed dilator papillaeo pupil is fully abducted and depressed because of the unopposed activity of the lateral rectus

and superior oblique


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Compression of Oculomotor Nerve

Rapidly increasing intracranial pressure (e.g., extradural hematoma) often compresses CN III againstthe crest of the petrous part of the temporal bone

Superficial autonomic fibers in CN III are affected first, as a result the pupil dilates progressively on theinjured side

First sign of CN III compression: ipsilateral slowness of the papillary response to lightAneurysm of Posterior Cerebral or Superior Cerebellar Artery

May also exert pressure on CN III as it passes between these vessels Effects of the pressure depend on its severity

TROCHLEAR NERVE

CN IV is rarely paralyzed alone, lesions of this nerve or its nucleus cause paralysis of the superioroblique and impair the ability to turn the affected eyeball inferomedially

CN IV may be torn when there are severe head injuries because of its long intracranial course Trochlear nerve injury classically presents as diplopia(double vision) when looking down

TRIGEMINAL NERVE

Injury to Trigeminal Nerve

CN V may be injured by trauma, tumors, aneurysms, or meningeal infection. Isolated lesion of thespinal trigeminal tract may also occur with MS. CN V injury results in:

o Paralysis of muscles of mastication with deviation of mandible toward the side of the lesiono Loss of the ability to appreciate soft tactile, thermal, or painful sensations in the faceo Loss of corneal reflex and the sneezing reflex

Common causes of facial numbness: dental trauma, herpes zoster ophthalmicus(infection caused byherpes virus), cranial trauma, head and neck tumors, intracranial tumors, idiopathic trigeminal

neuropathy

Trigeminal neuralgiathe principal disease affecting the sensory root of CN VDental Anesthesia

CN V is the sensory nerve of the head, serving the teeth and mucosa of the oral cavity Because the superior alveolar nerves (CN V2branches) are not accessible, the maxillary teeth are

locally anesthetized by injecting the agent into the tissues surrounding the tooth roots and allowingthe solution to infiltrate the tissue to reach the terminal nerve branches that enter the roots

The inferior alveolar nerve(CN V3) is readily accessible and is most frequently anesthetizedABDUCENT NERVE

CN VI is often stretched when intracranial pressure rises, partly because of the sharp bend it makesover the crest of the petrous part of the temporal bone after entering the dura

Space occupying lesions (e.g., brain tumor) may compress CN VI, causing paralysis of the lateral rectus Complete paralysis of CN VI causes medial deviation of the affected eye, diplopia is also present Paralysis of CN VI may also result from:

o Aneurysm of cerebral arterial circle at base of the braino

Pressure from an atherosclerotic internal carotid artery in the cavernous sinuso Septic thrombosis of the sinus due to infection in the nasal cavities and/or paranasal sinuses

FACIAL NERVE

CN VII is the most frequently paralyzed of all the cranial motor nerves Injury to CN VII may cause paralysis of facial muscles without loss of taste on the anterior two thirds of

the tongue or altered secretion of the lacrimal and salivary glands

Lesion of CN VII near its originloss of motor, gustatory, autonomic function, motor paralysis ofsuperior and inferior facial muscles on the ipsilateral side

Central lesion of CN VIIparalysis of muscles in the inferior face on the contralateral side


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CN VII is vulnerable to compression when a viral infection produces inflammation (viral neuritis) andswelling of the nerve just before it emerges from the stylomastoid foramen

Because the branches of CN VII are superficial, they are subject to injury from knife and gunshotwounds, cuts, and birth injuries

CN VII damage is common with fracture of the temporal bone and by tumors of the brain and cranium,aneurysms, meningeal infections, and herpes viruses

Bell Palsyunilateral facial paralysis of sudden onset resulting from a lesion of CN VIIVESTIBULOCOCHLEAR NERVE

Injuries to the Vestibulocochlear Nerve

Although the vestibular and cochlear nerves are essentially independent, peripheral lesions oftenproduce concurrent clinical effects because of their close relationship

Lesions of CN VIII may cause tinnitus, vertigo, and impairment or loss of hearingDeafness

Two kinds of hearing loss:o Conductive deafnessinvolving the external or middle earo Sensorineural deafnessdisease of the cochlea or in pathway from the cochlea to the brain

Acoustic Neuroma

Slow-growing benign tumor of the neurolemma (Schwann cells) Tumor begins in the vestibular nerve while it is in the internal acoustic meatus Early symptom of acoustic neuroma is usually loss of hearing

Trauma and Vertigo

Dizziness, vertigo, and headache in association with head trauma are usually related to a peripheralvestibular nerve lesion

GLOSSOPHARYNGEAL NERVE

Lesions of Glossopharyngeal Nerve

Isolated lesions of CN IX or its nuclei are uncommon and are not associated with perceptible disability Taste is absent on the posterior third of tongue and the gag reflex is absent on the side of the lesion Injuries of CN IX resulting from infection or tumors are usually accompanied by signs of involvement of

adjacent nerves: because CN IX, X, and XI pass through the jugular foramen, tumors in this regionproduce multiple cranial nerve palsies (jugular foramen syndrome)

Pain in distribution course of CN IX may be associated with involvement of the nerve in a neck tumorGlossopharyngeal Neuralgia

Sudden intensification of pain is of a burning or stabbing nature, often initiated by swallowing,protruding the tongue, talking, or touching the palatine tonsil

Uncommon and cause is unknownVAGUS NERVE

Isolated lesions of CN X are uncommon Injury to pharyngeal branches of CN X results in dysphagia(difficulty swallowing)

Lesions of the superior laryngeal nerve produce anesthesia of the superior part of the larynx andparalysis of the cricothyroid muscle

Injury of recurrent laryngeal nerve may be caused by aortic arch aneurysm and causes hoarseness anddysphonia(difficulty speaking) due to paralysis of vocal cords

Paralysis of both recurrent laryngeal nerves causes aphonia(loss of voice) and inspiratorystridor(harsh, high pitched respiratory sound)

Because of its longer course, lesions of the leftrecurrent laryngeal nerve are more common than thoseof the right


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SPINAL ACCESSORY NERVE

Because of its nearly subcutaneous passage through the posterior cervical region, CN XI is susceptibleto injury during surgical procedures such as lymph node biopsy, cannulation of the internal jugular

vein, and carotid endarterectomy

HYPOGLOSSAL NERVE

Injury to CN XII paralyzes the ipsilateral half of the tongue and after some time, the tongue atrophies,making it appear shrunken and wrinkled

When the tongue is protruded, the apex deviates towards the paralyzed side because of theunopposed action of the genioglossus muscle on the normal side of the tongue

CERVICAL FASCIA (988-989)

Paralysis of Platysma

Results from injury to the cervical branch of the facial nerve and causes the skin to fall away from theneck in slack folds

During surgical dissections of the neck, extra care is necessary to preserve the cervical branch of thefacial nerve and, when suturing wounds of the neck, surgeons carefully suture the skin and edges of

the platysma, otherwise the skin wound will be distracted by the contracting platysma muscle fibersSpread of Infections in Neck

Investing layer of deep cervical fasciahelps prevent the spread of abscesses caused by tissuedestruction (if the infection occurs between investing layer and muscular part of pretracheal fascia

surrounding the infrahyoid muscles)

If the infection occurs between the investing fascia and the visceral part of the pretracheal fascia, itcan spread into the thoracic cavity anterior to the pericardium

Infection from abscess posterior to the prevertebral layer of deep cervical fascia may extend laterallyin the neck and form a swelling posterior to the SCM

Retropharyngeal abscesspus perforates prevertebral layer of deep cervical fascia, producing a bulgein the pharynx, causing dysphagiaand dysarthria(difficulty speaking)

Infections in the head may also spread inferiorly posterior to the esophagus and enter the posteriormediastinum or may spread anterior to the trachea and enter the anterior mediastinum

Air from a ruptured trachea, bronchus, or esophagus (pneumomediastinum) can pass superiorly in theneck

SUPERFICIAL STRUCTURES OF NECK: CERVICAL REGIONS (1007-1011)

Congenital Torticollis

Contraction or shortening of the cervical muscles that produces twisting of neck and slanting of head Most common type (wry neck) results from afibrous tissue tumorthat develops in the SCM before or

shortly after birth, often the abnormal position of the infants head usually requires a breech delivery

Muscular torticollisoccurs when the SCM fibers are torn when an infants head is pulled too muchduring a difficult birth

A hematomaoccurs that may develop into a fibrotic mass that entraps a branch of the spinal accessorynerve and thus denervates part of the SCM

Stiffness and twisting of the neck results from fibrosis and shortening of the SCMSpasmatic Torticollis

aka Cervical dystoniaabnormal tonicity of the cervical muscles that usually begins in adulthood May involve any bilateral combination of lateral neck muscles, especially SCM and trapezius Characterized by sustained turning, tilting, flexing, or extending of the neck, involuntarily shifting the

head laterally or anteriorly, and shoulder elevated and displaced anteriorly to side which chin turns


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Subclavian Vein Puncture

Point of entry for central line placement, such as Swan-Ganz catheter Central lines are inserted to administerparenteral(venous nutritional) fluids and medications and to

measure central venous pressure

If the needle is not inserted carefully, it may puncture the pleura and lung, resulting inpneumothorax If needle is inserted too far posteriorly, it may enter the subclavian artery

Right Cardiac Catheterization

Puncture of the internal jugular to insert a catheter through the right brachiocephalic vein and into thesuperior vena cava to take measurements of pressures in the right chambers of the heart Preferred route is through IJV or subclavian, but it may be necessary to use the external jugular which

is not ideal due to its angle of junction with the subclavian vein

Prominence of External Jugular Vein

EJV may serve as an internal barometer: when venous pressure is normal, the EJV is visible above theclavicle for only a short distance but when pressure rises (e.g., heart failure), the vein is prominent

throughout its course along the side of the neck

Examination of EJV may be diagnostic for: heart failure, SVC obstruction, enlarged supraclavicularlymph nodes, or increased intrathoracic pressure

Severance of External Jugular Vein

If EJV is severed along posterior border of SCM where it pierces the roof of the lateral cervical region,its lumen will be held open by the tough investing layer of deep cervical fascia and the negative

intrathoracic pressure will suck air into the vein

This produces a churning noise in the thorax and cyanosis(bluish discoloration of skin due to reducedhemoglobin in blood)

This venous air embolismwill fill the right side of the heart with froth, which nearly stops blood flowthrough it, resulting in dyspnea

Lesions of Spinal Accessory Nerve (CN XI)

Lesions of CN XI are uncommon but may be caused by:o Penetrating trauma (e.g., stab or bullet wound)o Surgical procedures in the lateral cervical regiono Tumors at cranial base or cancerous cervical lymph nodeso Fractures of the jugular foramen where CN XI leaves the cranium

People with CN XI damage usually have weakness in turning the head to the opposite side againstresistance due to weakness and atrophy of the trapezius

Unilateral paralysis of the trapezius is evident by the patients inability to elevate and retract theshoulder and by difficulty in elevating the upper limb above horizontal

Drooping of the shoulderis an obvious sign of CN XI injury Important to have awareness of its location during lateral cervical region surgical procedures (e.g.,

removing cancerous lymph nodes) because CN XI is the most commonly iatrogenic nerve injury

Severance of Phrenic Nerve, Phrenic Nerve Block, and Phrenic Nerve Crush

Severance of a phrenic nerveresults in paralysis of the corresponding half of the diaphragm Phrenic nerve blockproduces temporary paralysis of hemidiaphragm (e.g., during lung operation)

Surgical phrenic nerve crush(e.g., compressing nerve with forceps) produces a longer period ofparalysis. If an accessory phrenic nerve is present, it must also be crushed to produce complete

paralysis of the hemidiaphragm.

Nerve Blocks in Lateral Cervical Region

For regional anesthesia before neck surgery, a cervical plexus blockinhibits nerve impulse conduction Anesthetic is injected mainly at junction of SCM superior and middle thirds: the nerve point of the neck For anesthesia of upper limb, the anesthetic in a supraclavicular brachial plexus blockis injected

around the supraclavicular part of the brachial plexusInjury to Suprascapular Nerve

Suprascapular nerve is vulnerable to injury in fractures of the middle third of the clavicle Injury results in loss of lateral rotation of the humerus at the glenohumeral joint


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The relaxed limb rotates medially into the waiters tip positionLigation of External Carotid Artery

Sometimes this is necessary to control bleeding from on its less accessible branches Blood will then flow in a retrograde direction into the artery from the external carotid on the other

side through communications between its branches (face and scalp) and across the midline

When ligated, the descending branch of the occipital artery provides the main collateral circulation,anastomosing with the vertebral and deep cervical arteries

Surgical Dissection of Carotid Triangle Carotid triangle provides access to carotid system of arteries as well as IJV, vagus and hypoglossal

nerves, and the cervical sympathetic trunk

Damage or compression of vagus and/or recurrent laryngeal nerves during surgical dissection of thecarotid triangle may produce an alteration in the voice because these nerves supply laryngeal muscles

Carotid Occlusion and Endarterectomy

Atherosclerotic thickening of the intima of internal carotid may obstruct blood flow, causing stenosis A partial occlusion may cause a TIA, transient ischemic attack, a sudden focal loss of neurological

function that disappears within 24 hrs

May also cause a minor stroke, a loss of neurological function such as weakness or sensory loss on oneside of the body that exceeds 24 hrs but disappears within 3 weeks

Doppler color studiesare used to observe the obstruction of blood flow in arteries Carotid endarterectomyis a procedure in which the artery is opened at its origin and the

artherosclerotic plaque is stripped off

Because of the relation to the ICA, risk of cranial nerve injury during the procedure may involve CN IX,X, XI, or XII

Carotid Pulse

Easily felt by palpating the common carotid in the side of the neck, where it lies in a groove betweenthe trachea and the infrahyoid muscles

It is routinely checked during CPR, absence of carotid pulse indicates cardiac arrestCarotid Sinus Hypersensitivity

Exceptional responsiveness of the carotid sinus in various types of vascular disease External pressure on the carotid may cause slowing of the heart rate, decreased blood pressure, and

cardiac ischemia resulting in fainting (syncope) In all forms of syncope, symptoms result from a sudden and critical decrease in cerebral perfusion

Role of Carotid Bodies

Location is ideal to monitor the oxygen content of the blood before it reaches the brain Decrease in PO2activates the aortic and carotid chemoreceptors, increasing alveolar ventilation Carotid bodies also respond to increased CO2tension or free hydrogen ions in the blood Glossopharyngeal nerve conducts the information, resulting in increased depth and rate of breathing,

and increased pulse rate and blood pressure, thus taking in more O2and reducing [CO2]

Internal Jugular Pulse

Pulsations of IJV can provide info about heart activity IJV pulsations are transmitted through the surrounding tissue and may be observed beneath the SCM

superior to the medial end of the clavicle Pulsations are especially visible when a persons head is lower than legs (Trendelenburg position) IJV pulse increases in conditions such as mitral valve disease, which increases pressure in the

pulmonary circulation and the right side of the heart

Right IJV is examined because it runs a more direct course to the right atriumInternal Jugular Vein Puncture

Right IJV is preferable because it usually larger and straighter Clinician will palpate common carotid and insert needle into IJV just later to it, aiming at the apex of

the triangle between the sterna and clavicular heads of the SCM, the lesser supraclavicular fossa


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DEEP STRUCTURES OF NECK (1017)

Cervicothoracic Ganglion Block

Anesthetic injected around the large cervicothoracic ganglion blocks transmission of stimuli throughthe cervical and superior thoracic ganglia

This block may relieve vascular spasms involving the brain and upper limb, or when deciding if surgicalresection of the ganglion would be beneficial

Lesion of Cervical Sympathetic Trunk

Results in sympathetic disturbance called Horner Syndrome, characterized by: miosis(paralysis ofdilator pupillae),ptosis(paralysis of levator palpebrae superioris), enopthalmos(paralysis of orbitalmuscle in floor of orbit), and anhydrosis(lack of sympathetic nerve supply to blood vessels and sweat

glands)

FACE AND SCALP (860-864)

Facial Lacerations and Incisions

Facial lacerations tend to gape (skin must be carefully sutured to prevent scarring) due to absence ofany distinct deep fascia and looseness of subcutaneous tissue between the cutaneous attachments of

the facial muscles

Looseness of subcutaneous tissue also enables fluid and blood to accumulate (bruising)

With age, skin loses resiliency, ridges and wrinkles occur in the skin perpendicular to the direction offacial muscle fibers. Skin incisions along these wrinkle lines (Langer lines) heal with minimal scarring

Scalp Injuries

Partially detached scalp may be replaced as long as one of the vessels supplying scalp remains intact During an attached craniotomy, the superficial temporal artery is included in the tissue flap for this

purpose

The scalp proper (first three layers of scalp) is clinically regarded as single layer because they remaintogether when a scalp flap is made or scalp is torn off

Arteries of scalp supply little blood to calvaria, which is supplied by middle meningeal arteries,therefore loss of scalp does not produce necrosis of calvarial bones

Scalp Wounds

Because of the strength of the epicranial aponeurosis, superficial scalp wounds do not gape However, deep scalp wounds gape widely when the aponeurosis is lacerated in the coronal plane

because of the pull of the frontal and occipital bellies of the occipitofrontalis in opposite directions

Scalp Infections

Loose connective tissue layer (fourth layer of scalp) is the danger area of the scalp because pus orblood can spread easily in it

Infection of this layer can also pass into the cranial cavity through emissary veins, which pass throughparietal foramina in the calvaria and reach intracranial structures such as the meninges

Pus or blood can enter the eyelids and root of nose because the frontalis inserts into the skin andsubcutaneous tissue does not attach to the bone. Consequentlyperiorbital ecchymosis(black eyes) can

result from an injury to the scalp and/or forehead.

Sebaceous Cysts

Ducts of sebaceous glands associated with hair follicles may become obstructed, resulting in retentionof secretions and formations of sebaceous cysts

These cysts move with the scalp because they are in the skinCephalhematoma

After a difficult birth, bleeding may occur between the babys pericranium and calvaria, usually overone parietal bone

Blood becomes trapped in the area, causing cephalhematomaFlaring of Nostrils

True nasal breatherscan flare their nostrils distinctly, whereas habitual mouth breathershavediminished ability to flare the nostrils


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Children who are chronic mouth breathers often develop dental malocclusionbecause the alignment ofthe teeth is maintained to a large degree by normal periods of occlusion and labial closure

Anti-snoring devices have been developed that attach to the nose to flare the nostrils and maintain amore patent air passageway (Breathe-Right strips)

Paralysis of Facial Muscles

Injury to facial nerve or its branches produces paralysis of some or all facial muscles on the affectedside (Bell palsy)

The affected area sags, and facial expression is distorted, making it appear passive or sad Loss of tonus of orbicularis oculi causes the inferior eyelid to evert and lacrimal fluids are not

adequately spread across the cornea, making the cornea vulnerable to ulceration

If the injury weakens or paralyzes the buccinators, food will accumulate in the buccal vestibule When the sphincters or dilators of the mouth are affected, displacement of the mouth (drooping of

the corner) is produced by contraction of unopposed contralateral facial muscles and gravity (food and

saliva dribble out of side of mouth)

Weakened lip muscles affect speech and ability to whistle and blowInfra-Orbital Nerve Block

Local anesthesia of the inferior part of the face is achieved by infiltration of the infra-orbital nerve fortreating wounds of upper lip and cheek or for repair of maxillary incisors

Injection is made in the region of the infra-orbital foramen, by elevating the upper lip and passing theneedle through the junction of the oral mucosa and gingival at the superior aspect of the oral vestibule

To determine where the infra-orbital nerve emerges, pressure is exerted on the maxilla in the region ofthe infra-orbital foramen (too much pressure causes considerable pain)

Because companion vessels leave the infra-orbital foramen along with the nerve, aspiration of thesyringe during injection prevents inadvertent injection of anesthetic into a blood vessel

Careless injection could result in passage of anesthetic into the orbit, causing temporary paralysis ofthe extraocular muscles

Mental and Incisive Nerve Blocks

Injection of anesthetic into mental foramen will block the mental nerve that supplies the skin andmucous membrane of the lower lip from the mental foramen to the midline

Buccal Nerve Block

Anesthetic injection can be made into the mucosa covering the retromolar fossa, located posterior tothe 3

rdmandibular molar between the anterior border of the ramus and the temporal crest

This is used to anesthetize the skin and mucous membrane of the cheekTrigeminal Neuralgia

Sensory disorder of the sensory root of CN V that occurs most often in middle-aged and elderly Paroxysm (sudden sharp pain) can last for 15 minutes or more CN V2is most frequently involved, CN V1is least frequently involved In most cases, demyelination of axons in the sensory root occurs, caused by pressure of a small

aberrant artery

Simplest surgical procedure is avulsion or cutting of branches of the nerve at the infra-orbital foramen Other treatments have used radiofrequency selective ablation of parts of the trigeminal ganglionby a

needle electrode passing through the cheek and the foramen ovale Rhizotomy(sensory root cut between ganglion and brainstem) or tractotomy(sectioning the spinal

tract of CN V resulting in loss of sensation of the skin) are other treatment possibilities

Lesions of Trigeminal Nerve

Lesions of the entire CN V cause widespread anesthesia involving the:o Corresponding anterior half of the scalpo Face, except for an area around the angle of the mandible, the cornea, and the conjunctivao Mucous membranes of the nose, mouth, and anterior part of the tongueo Paralysis of muscles of mastication


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Herpes Zoster Infection of Trigeminal Ganglion

Infection is characterized by an eruption of groups of vesicles following the course of the affectednerve (any division of CN V may be involved, but ophthalmic is most common)

Usually the cornea is involved, resulting in painful corneal ulceration and subsequent scarring of thecornea

Injuries to Facial Nerve

Injury to branches of the facial nerve cause paralysis of facial muscles (Bell Palsy), with or without lossof taste on the anterior two thirds of the tongue or altered secretion of the lacrimal and salivary glands

Most common nontraumatic cause of facial nerve palsy is inflammation of the facial nerve near thestylomastoid foramen, often as a result of viral infection

Injury of facial nerve also occurs from fracture of temporal bone, surgical complication, dentalmanipulation, vaccination, pregnancy, HIV, Lyme disease, and infections of middle ear

o Lesion of zygomatic branchparalysis, including loss of tonus of the orbicularis oculi in theinferior eyelid

o Paralysis of buccal branchparaylysis of buccinators and superior portion of orbicularis orisand upper lip muscles

o Paralysis of marginal mandibular branchparalysis of inferior portion of orbicularis oris andlower lip muscles (occurs when an incision is made along inferior border of mandible)

Compression of Facial Artery

Facial artery can be occluded by pressure against the mandible where the vessel crosses it Compression of the artery on one side does not stop all bleeding from a lacerated facial artery or its

branches due to the numerous anastomoses

Pulses of Arteries of Face and Scalp

Pulses of superficial temporal and facial arteries may be used for taking pulseStenosis of Internal Carotid Artery

At the medial angle of the eye, an anastomosis occurs between the facial artery, a branch of theexternal carotid, and the cutaneous branches of the internal carotid

With age, the internal carotid may become stenotic but intracranial structures still receive blood dueto the anasomoses

Scalp Lacerations

Most common type of head injury requiring surgical care Bleed profusely because the arteries entering the periphery of the scalp bleed from both ends (due to

abundant anastomoses)

Also, these arteries do not retract in response to laceration because they are held open by the denseconnective tissue of the scalp (second layer of scalp)

Squamous Cell Carcinoma of Lip

Usually involves lower lip, with overexposure to sun or chronic irritation from pipe smoking commonfactors

Cancer cells from central part of lower lip, floor of mouth, and apex of tongue can spread to thesubmental lymph nodes

Cancer cells from lateral parts of the lower lip will spread to the submandibular lymph nodes

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