central nervous system radiographic pathology

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Cns radiographic PathologyBy:Yannick Ngerageze1

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Introduction

2The nervous system is a very complex system in the body. It has many, many parts. The nervous system is divided into two main systems, the central nervous system (CNS) and the peripheral nervous system.Generally, CT, MRI and nuclear medecine are imaging modalities of choice for brain diseases2Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Brain anatomy

CerebrumThe cerebrum is the largest part of the brain and contains two hemispheres. Each cerebral hemisphere contains four lobes; the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe

33Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

33The cerebrum is the largest part of the brain and contains two hemispheres. The right hemisphere controls the left side of the body, and the left hemisphere controls the right side of the body.

Each cerebral hemisphere contains four lobes; the frontal lobe, the parietal lobe, the occipital lobe, and the temporal lobe. The frontal lobe controls cognitive ability, memory, behavior, and the ability to speak and write. Symptoms caused by a frontal lobe tumor include seizures, impaired judgment, personality changes, and short-term memory loss. The parietal lobe controls sensory discrimination and body orientation. Spatial disorders, seizures, language disturbances, and the inability to do arithmetic are symptoms of a parietal lobe tumor. The occipital lobe controls the understanding of visual images.

Symptoms of a tumor in the occipital lobe include blindness in one direction and seizures. The temporal lobe controls hearing and the ability to understand the spoken word, and the most common symptom of a tumor in the temporal lobe is seizure.

Cerebellum

The cerebellum is the second largest area of the brain. The brain stem is at the bottom of the brain and connects the spinal cord to the cerebrum. The pons, midbrain, and medulla oblongata are part of the brain stem44Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

44The cerebellum is the second largest area of the brain. It is involved with muscle coordination, walking, and speech. Symptoms of a tumor in the cerebellum may include but are not limited to swaying, difficulty with coordination and walking, and difficulty with speech.

The brain stem is at the bottom of the brain and connects the spinal cord to the cerebrum. The pons, midbrain, and medulla oblongata are part of the brain stem. The brain stem controls blood pressure, heart beat, breathing, consciousness, and eating and sleeping patterns. Brain stem tumor symptoms may include but are not limited to vomiting, one-sided facial muscle weakness, swallowing difficulty, double vision, and headache just after waking.

Ventricular System

There are two lateral ventricles, one in each cerebral hemisphere. The third ventricle is located near the hypothalamusAnd the fourth ventricle between the medulla oblongata and the brain stem and the cerebellum.


55The ventricles are cavities within the brain that contain cerebrospinal fluid. There are two lateral ventricles, one in each cerebral hemisphere. The third ventricle is located near the hypothalamus and thalamus, and the fourth ventricle is located between the medulla oblongata and the brain stem and the cerebellum.

MeningesThe meninges are three membranes that cover the brain and spinal cord and protect the CNS. The dura mater is the tough outer membrane. The arachnoid is the middle web-like membrane. The pia mater is the inner most membrane and is delicate and highly vascular. The subarachnoid space is between the arachnoid and pia mater and contains cerebrospinal fluid (CSF). 66Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Meninges


77The meninges are three membranes that cover the brain and spinal cord and protect the CNS. The dura mater is the tough outer membrane. The arachnoid is the middle web-like membrane. The pia mater is the inner most membrane and is delicate and highly vascular. The subarachnoid space is between the arachnoid and pia mater and contains cerebrospinal fluid (CSF).

Symptoms of tumors of the meninges are usually caused by compression and pressure, not by growth into brain tissue. Seizures are the most common symptom.

Spinal Cord


88The spinal cord begins in the medulla oblongata, which is part of the brain stem. The central canal is a small canal that runs through the center of the spinal cord and is filled with cerebrospinal fluid. It represents the remainder of the neural canal in adults. The neural tube develops to become the brain stem and, expands dorsally and laterally to create the fourth ventricle. Generally, the unchanged neural canal in the spinal cord forms the central canal. It is an anatomic extension of the ventricles and is also referred to as the spinal foramen.A spinal cord is about 18 inches (about 45 cm) long and connects the peripheral nerves to the brain. It is the major nerve tract of the body. The central nervous system is compromised of the brain and spinal cord the central canal is at the very center of the spinal cord.The central canal runs from the conus medullaris in the lumbar spine to the end of the fourth ventricle, and is attached to the ventricle by the opex. Generally, the outermost part of the canal is the gray commissure, which is a thin strip of gray matter that surrounds the central canal of the spinal cord. The gray commissure, along with the anterior white commissure, connects the two parts of the cord. Ependymal cells that make the cerebrospinal fluid, the cilia, and the interior lumen can be found inside the gray commissure. It is made up of nerve fibers. Meninges cover and protect the spinal cord. Symptoms of spinal cord tumors depend on the nerves involved. Symptoms include pain in the chest with thoracic tumors and pain in the neck, arm, back or leg with lumbar or cervical tumors.

Diseases of the nervous system Edema, herniation and hydrocephalusVasular diseasesCentral Nervous System (CNS) traumaCongenital malformations and perinatal brain injuryInfections of CNS

Primary disease of myelinAcquired metabolic and toxic disturbancesDegenerative diseasesDiseases of the peripheral nervous systemNeoplasms


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Inceased ICP , herniation, Cerebral edema, and hydrocephalusSkull is rigid and nonexpandable.Increased fluid or additional tissue in intracranial space leads to increased ICPCauses of increased ICPSpace-occupying mass : tumor, abscess, hematomaDiffuse lesions : brain edema, encephalitis, subarachnoid hemorrhageIncreased volume of CSF : hydrocephalus


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Cerebral edemaAbnormal fluid accumulation in cerebral parenchymaTypes:Vasogenic edema: increased vascular permeabilityTumor, inflammationCytotoxic edema : altered cell regulation of fluidToxin


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CT ImageIt cause:Increased brain weightFlat gyriNarrow sulciMRI and CT can be used

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Cerebral herniationSutures for children accommodates to increased intracranial pressure.In adults it is poorly toleratedAs expanding brain parenchyma encounter, many different patterns of herniation may develop3 most common forms are: Subfalcine (cingulate); Transtentorial (uncal) Tonsillar (foramen magnum)


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CT and MRI Images

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HydrocephalusIs the dilatation of the ventricular system (accumulation of CSF) Dilated venticles compress white matterNoncommunicating: due to obstruction within the ventricular system, e.g. Tumor, aqueductal stenosisCommunicating: due to obstruction of CSF flow in the subarachnoid space with decreased reabsorption


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Cerebrovascular diseasesBrain is highly aerobic organ20% of total body oxygen consumption15% of resting cardiac outputAutoregulation of cerebral blood flowIrreversible damage of the brain 6-8 min causes of oxygen deprivationFunctional hypoxiaLow inspire of oxygenImpaired oxygen carrying capacityIschemiaDecreased perfusion pressure hypotensionOcclusion of vessels


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Cerebrovascular diseasesCerebral vascular diseases can be divided into three major category:Parenchymal injuries: those associated with generalized reduction in blood flow, including global hypoxic ancephalopathyInfarct : caused by local vascular obstructionHemorrhages : within the parenchyma or subarachnoid space1818Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Global cerebral ischemiaIschemic/hypoxic encephalopathyCause profound systemic hypotensionTransient :complete recoveryProlong : brain necrosisBrain death : brain stem damage which cause cardiovascular failure1919Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Cerebral infarctionThe major cause of infarct is strokeStroke: sudden neurologic deficit caused by abnormal blood supply (including intracerebral hemorrhage)EtiologyAtherosclerosis of bifurcation of carotid a., basilar a. Arteritis : infection (TB, syphilis), Others : aneurysm


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Hemorrhage Saccular aneurisms and subarachnoid hemorrhage (caused by a rupture of a saccular aneurism) are mostly located on arterial bifurcations. 21


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MRI image


Traumatic injuriesEpidural hematomaSubdural hematomaSubarachnoid hemorrhagelacerations2323Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Epidural hematomaSkull fracture at temporal bone may causes laceration of middle meningeal arteryDraw back of the skull may be the cause


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Subdural hematomaPotential space, subdural, contains bridging veins from cortical surface to empty into superior sagittal sinusBrain moves freely but venous sinus is fixedBrain displacement during trauma can tear the veins at the point they penetrate the dura


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Subdural hematomaClinically manifest at first 48 hrs.Most-nonlocalising signs : headache, confusionMay be focal signs : contralateral paralysis, seizures


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Acute epidural and Acute subdural

Acute epidural

Acute subdural


MRI images of chronic hematomaChronic epidural hematoma

Chronic subdural hematoma


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CT image of lacerations:Tearing of the frontal and temporal lobes or blood vessels of the brain The force of the blow causes the brain to rotate across the hard ridges of the skull, causing the tears


Spinal cord injuryDisplacement of vertebral column causes byStab wound BulletsVertebral fracture with dislocationNeurologic manifestation:Thoracic vertebra or below paraplegiaCervical vertebra (below C4) quadriplegiaCervical vertebra (upper C4) respiratory arrest


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31MRI image of traumatic spinal cordMRI is the best modality for spinal cord injuries as it is super in soft tissues differentiation


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Congenital malformationNeural tube defectCommonestDefective closure of the midline structure over the neural tubeRisk factor : folate deficiency in initial week of gestation3232Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Congenital malformationAnencephaly:No brain (linked with folate deficiency, age of mother over 40; more often affects girls)Fatal, spontaneous abortionEncephaloceleOssification defect in the skullHerniation of the brain & meningesOccipital, frontal, orbital & nasal


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AnencephalyEncephalocele34Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Ultrasound of an intrauterine foetuwith encephalocele


Neural tube defectSpina bifidaDefective development and closure of vertebral archMost common in lumbar region2 typesSpina bifida occultaSpina bifida cystica


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Neural tube defectSpina bifida occultaAsymptomaticNormal spinal cord and meningesMay have sinus tract of overlying skinSpina bifida cysticaMeningomyelocele (myelomeningocele)Extension of CNS tissue through a defectCommon in LS regionMeningoceleOnly meningeal extrusion


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Images ClinicalMotor & sensory deficit in lower extremityDisturbances of bowel & bladder controlSuperimposed infection from overlying skin

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Neural tube defect of a fetus


CNS infectionA CNS infection is an infection which involves the central nervous system in some way. Meningitis is one of the most common and well known types, involving the meninges, the coverings of the brain and spinal cord. Other types of infections involve the brain or spinal cord directly. For example, a cerebral abscess is a bacterial brain infection and encephalitis is typically a viral infection of the brain. 4040Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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MeningitisMeningitis is one of the most common forms of infection affecting the nervous system. It is characterized by infection of the membranes covering the brain and spinal cord, centered in the cerebrospinal fluid that surrounds the nervous system. There is types: bacterial, viral and fungal meningitis4141Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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CT and MRI Images

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V.3 Brain abscessIt is a bacterial brain infection. Also called a cerebral abscess, these infections are destructive lesions within the substance of the brain itself. 4343Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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CT with contrast and MRI image


Neoplasm of CNS

Glioma

It is a type of tumor that starts in the brain or spine. It is called a glioma because it arises from glial cells. The most common site of gliomas is the brain. The main types of gliomas are:Ependymomas: ependymal cells. Astrocytomas: astrocytesOligodendrogliomas : oligodendrocytes. Mixed gliomas, such as oligoastrocytomas, contain cells from different types of glia. The exact causes of gliomas are not known.


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46CT and MRI Image46Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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Diseases of myelinDemyelinating diseases: Acquired disorders of myelin, such as multiple sclerosis.Dysmyelinating diseases:Genetic disorders of myelin and its turnover, such as leukodystrophies


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Multiple sclerosisIt is known as disseminated sclerosis is an inflammatory disease in which the fatty myelin sheaths around the axons of the brain and spinal cord are damaged.Leading to demyelination and scarring as well as a broad spectrum of signs and symptoms. Most likely MS occurs as a result of some combination of genetic, environmental and infectious factors 4848Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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MRI Images


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Acquired metabolic and toxic disturbancesNutritional diseases: Thiamine deficiency is common in alcoholics (first cause of brain changes in alcoholics, other than traumatic lesions) hemorrhagic white matterB12 deficiency causes sub acute degeneration of spinal cord with myelin vacuolization, causing motor and sensory abnormalities, weakness, confusion


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Toxic disturbance

Cocaine encephalopathyCocaine can cause vasospasm and vasculitis leading to ischemic and hemorrhagic infarction.On MRI, lesions with increased signal intensity on T2 weighted images are reported in the globus pallidi, splenium, and cerebral white matter, with affected regions often showing restricted diffusion51


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Degenerative diseasesAlzheimers DiseaseMost common cause of dementiaDefective processing of amyloid precursor protein Affects hippocampus/parahippocampal cortex, cerebral cortex, tremor MR used to rule out other causes of dementia


T1 weighted MRControl

Alzheimers53Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

Alzheimers CTCT- Diffuse cerebral atrophy, enlarged ventricles and widened sulci


Parkinsons DiseaseHypokinetic disorderLoss of dopaminergic neurons in substantia nigra Pill-rolling tremor, cog-wheel rigidity, bradykinesia, shuffling gait, mask-like faciesOn MRI, there is a decreased pars compacta width (substantia nigra) may be evident on MR


T2 weighted MRControl

Parkinsons56Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

Conclusion

57The brain is totally made by soft tissue surrounded by bone tissuesAs bone are hyperdense tissues,cross sectional images are mostly needed to rule out brain tissues diseasesBoth MRI and CT are used in brain diseases diagnosis because both of them can produce sectional images but MRI is the best for soft tissue imagingSome times nuclear medicine is used mostly in functional studiesPlain radiography is rarely used


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ReferencesRobbins (2003),Basic Pathology 7th edition, Saunders USA .Kumar (2006) Clinical Medicine 6th edition Elsevier USA.http://www.health.com/health/library/mdp/0,,zm6056,00.html accessed on 19/02/125858Prepared by Yannick Ngerageze a radiographer at gihundwe hospital

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central nervous system radiographic pathology

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