ultrasound of spinal cord in neonates dr. muhammad bin zulfiqar

Ultrasound of Spinal Cord in Neonates

DR. Muhammad Bin ZulfiqarPGR IV New Radiology Department SHL/[email protected]

Facts• Sonography can characterize nearly all spinal anomalies sufficiently in

the first days of life.• MRI is the study of choice when surgical therapy is required.

Lowe et al. Sonography of the Neonatal Spine: Part 1, Normal Anatomy, Imaging Pitfalls, and Variations That May Simulate Disorders. AJR 2007; 188:733–738

Agenda• Part I:• Lumbar spine embryology, • Sonography techniques• Indications• Normal anatomy• Developmental variations and pitfalls

• Part 2• abnormal entities.


Part 1

Embryology

• CNS starts to form during the third gestational week, beginning with the process known as neurulation


Embryology

• Canalization occurs at the distal end of the neural tube in the caudal cell mass, resulting in an ependyma-lined neural tube that unites with the rest of the spinal cord to form the conus medullaris and ventriculus terminalis.


Embryology• Finally, at 38 days of gestation,

retrogressive differentiation occurs forming the filum terminale.


Technique of Ultrasound

• Images are obtained in the longitudinal and transverse planes using a linear 5–12-MHz transducer.


• A, Transverse lumbar sonogram shows normal anatomy as labeled. V = vertebra, transverse process (arrowhead).• B, Longitudinal lumbar sonogram shows normal anatomy as labeled. Note central

echoic complex (arrowheads), a normal finding that results from interface of central end of anterior median fissure and not central spinal canal.


Technique of Ultrasound• The vertebral level• Determined by counting down from the 12th rib• Confirmed by counting up from the L5–S1 junction or the tip of

coccyx. • If the vertebral level is unclear, correlation with radiographs (possibly

with a marker) may help.


Indications of Spinal Ultrasound• Multiple congenital anomalies placing an infant at increased risk.• Complicated sacral dimple (location above the gluteal crease, bottom

of pit not seen, possible drainage from dimple, and presence of skin stigmata), • Soft tissue mass suspected of being spina bifida occulta.• Determination of reason for failed lumbar puncture• Location of CSF that may be tapped.


Indications of Spinal Ultrasound• Low-risk lesions • Simple midline dimples (< 5 mm in diameter, within 2.5 cm of the

anus, no other cutaneous stigmata).


Indications of Spinal Ultrasound• High-risk lesions• Atypical dimples (> 5 mm in diameter, > 2.5 cm above the anus)• Hemangiomas• Cutis aplasia • Hairy patches• Skin tags


Normal Variants That May Simulate Disorders

• Ventriculus terminalis• Filar cyst• Prominent filum terminale• Cauda equina pseudomass• Pseudosinus tract• Dysmorphic coccyx.


Ventriculus Terminalis

• The ventriculus terminalis, often seen on sonography and MRI in children younger than 5 years, is due to incomplete fetal regression of the embryonic terminal ventricle in the conus medullaris.


Ventriculus Terminalis

• A, Longitudinal sonogram of spine reveals distention of distal lumbar spinal canal just above conus medullaris (arrowhead). Size smaller than 5 mm and stability over time distinguish this normal variant from small syrinx. B, Sagittal T2-weighted MR image at age 7 months shows stable distention of distal spinal canal (arrowhead), excluding syrinx.


• Ventriculus terminalis in a healthy 7- week-old infant. Sagittal US scan of the lumbar spinal canal shows a ventriculus terminalis (arrowheads). 1 = conus medullaris with central echo complex.

Filar Cyst• Origin:• Normal arachnoid reflections form a pseudocyst like structure or that

it is a true ependyma-lined cystic embryonic remnant (possibly indistinguishable from the ventriculus terminalis).• Regardless of its origin, it is a normal variant


Filar Cyst• Imaging criteria for filar cyst• Location midline• Within filum Just below conus • Fusiform shape • Well-defined • Hypoechoic appearance of a simple cyst


Filar Cyst

• A, Transverse sonogram of proximal cauda equina shows well-defined, midline, cystic collection (arrow). Note normal ventral and dorsal nerve root bundles (arrowheads).• B, Longitudinal sonogram reveals well-defined fusiform “cyst” in midline

(arrow) just below conus medullaris. Also note prominent echogenic central spinal canal (arrowhead), a normal variant seen in some children.


• A, Longitudinal sonogram of filum and cauda equina (arrowhead) shows unusually long filar cyst (calipers). Despite its length, it meets criteria for filar cyst: location just below conus medullaris, fusiform shape, well defined, thin walled, and hypoechoic.• B, Longitudinal T2-weighted MR image shows ill-defined filar cyst

(arrows) that is better seen on sonography.Lowe et al. Sonography of the Neonatal Spine: Part 1, Normal Anatomy, Imaging Pitfalls, and Variations That May Simulate Disorders. AJR 2007; 188:733–738

Prominent Filum Terminale

• A prominent filum terminale may cause concern when it stands out as particularly echogenic in comparison with other nerve roots. • It is distinguished as normal by its thickness and typical midline

course.


• Prominent filum terminale in 2-week-old boy with asymmetric gluteal crease. Longitudinal sonogram shows hyperechoic filum of normal size (< 1 mm) (arrow) at L5–S1.


“Pseudomass” due to Positional Nerve Root Clumping

• Positional clumping of the nerve roots occurs when an infant is scanned in the decubitus position. • Rescanning the child prone will cause the “mass” to disappear as the

nerve roots return to their normal position


• A, Transverse sonogram shows clumping of nerve roots (arrows) on left due to left decubitus position.• B, Longitudinal sonogram also reveals masslike appearance of nerve

roots (arrows). Prone images (not shown) were normal.Lowe et al. Sonography of the Neonatal Spine: Part 1, Normal Anatomy, Imaging Pitfalls, and Variations That May Simulate Disorders. AJR 2007; 188:733–738

Pseudosinus Tract

• Pseudosinus tract seen on sonography as a residual cordlike region composed of fibrous tissue extending from a skin dimple to the coccyx. • True dermal sinus tracts rarely occur at the tip of the coccyx• Typically found in a more cranial location.

• If CSF is draining via a dimple, then a true sinus tract is likely, and MRI is the imaging technique of choice.


• Pseudosinus tract in 12-day-old infant with dimple in gluteal crease. Longitudinal sonogram shows cartilaginous, hypoechoic, dorsally curving tip of coccyx (arrowhead), from which hypoechoic cordlike structure (curved arrow) extends caudally and terminates at base of skin dimple (straight arrow).


Dysmorphic Coccyx

• The tip of the coccyx can vary widely in shape, and in some cases may mimic a mass when palpated on physical examination


• Misshapen coccyx in two neonatal girls, each with palpable “lump” beneath sacral dimple in gluteal crease.

• A, Longitudinal sonogram of coccyx in 2-week-old girl shows hypoechoic cartilaginous tip (arrowheads), which is acutely angulated dorsally as it extends toward skin surface. Palpated “lump” was tip of coccyx.

• B, Longitudinal sonogram of coccyx in 2-week-old girl reveals it is straightened, with loss of its normal ventral curve. Hypoechoic cartilaginous tip (arrowhead) extends dorsally toward skin surface, causing clinically palpable “lump.”


Conclusion

• Neonatal spinal sonography is a useful screening technique for occult spinal anomalies;• it can characterize normal anatomy and normal variants that may

simulate disorders.• Familiarity with these findings will prevent misinterpretation and

inappropriate referrals.


Part 2 Congenital Anomalies

Pathomechanism1. premature separation of the skin ectoderm from the neural tube

can lead to entrapment of mesodermal elements, such as fat. 2. Second, failed neurulation leads to dysraphisms, such as

myelomeningocele.3. Anomalies of the filum terminale, such as fibrolipomas and caudal

regression syndrome, are caused by disembryogenesis of the caudal cell mass.

Lowe et al. Sonography of the Neonatal Spine: Part 2, Spinal Disorders. AJR 2007; 188:739–744

Classification• Classified on the basis of the presence or absence of a soft-tissue

mass and skin covering.•Without a mass• Tethered cord• Diastematomyelia • Anterior sacral meningocele• Spinal lipoma.


Classification•With a skin covered soft-tissue mass:

1. Lipomyelomeningocele2. Myelocystocele.

•With a back mass but without skin covering1. Myelomeningocele2. Myelocele.


Tethered Cord• Tethered cord, or low-lying conus medullaris, is caused by incomplete

regressive Differentiation and failed involution of the terminal cord.• Symptoms occur because of traction on the abnormally anchored

filum terminale and adjacent nerve roots.


Tethered Cord•Sonographic Diagnostic Criteria1. low-lying conus (below the L2–L3 disk space)2. Lack of normal nerve root motion during real-time Sonography


Tethered Cord•Associated spinal findings 1. A thickened filum terminale, 2. Fibrolipoma3. Spinal dysraphisms4. Syringomyelia5. Scoliosis,6. Congenital spinal masses (lipomas, dermoids), cysts (myelocele)7. Sinus tracts that contain fluid .• Other nonneurologic anomalies are common as well, including tracheoesophageal

fistula, congenital heart disease, and renal anomalies (VATER syndrome).


• Tethered cord in 2-day-old boy with multiple congenital anomalies.• A, Longitudinal sonogram shows low-lying conus

(arrowhead) at L5 vertebra and thickened, echogenic fatty filum (arrow).• B, Sagittal T1-weighted MR image confirms thick, fatty filum

(arrow) overlapping tethered cord from L4 to S1 level.


• Syrinx and tethered cord in 1-week-old girl with imperforate anus and scoliosis.• A, Longitudinal sonogram reveals low-lying conus at L4

vertebra with hypoechoic cystic space (arrow) expanding lumbar spinal cord.• B, Sagittal T2-weighted MR image confirms conus is tethered

at S1 level (arrowhead) and lumbar spinal cord contains large, hyperintense, fusiform syrinx (arrow).


Spinal Lipoma

• Premature disjunction (embryologic separation of neural ectoderm from cutaneous tissue elements) that allows mesenchyme to be trapped between the neural folds and remain in contact with the neural canal.• They may be intradural, extradural, or a combination of both. In

addition to fat, 84% of lipomas also contain neural tissue or meninges [2, 3].


Spinal Lipoma• Associations: • Tethered cord, • Dysraphism (4%), • Fatty filum or lipoma of filum (12%), and • Vertebral anomalies


• Intradural lipoma and tethered cord in 2-week-old girl with hairy patch on lower back.• A, Longitudinal sonogram reveals typical features of hyperechoic lipoma (calipers)

attached to dorsal aspect of thoracolumbar spinal cord. Conus is tethered to mass at L3–L4 disk space (arrow).

• B, Transverse sonogram at L3 vertebra shows conus (arrow) tethered to dorsal lipoma (arrowhead).


Spina Bifida Occulta with Lipomyelomeningocele

• Spina bifida occulta is defined as any skin covered osseous defect of posterior elements through which various combinations of neural elements (neural placode), meninges, CSF, and adipose tissue protrude.• The cause is defective disjunction and neurulation with entrapped

mesenchyma in contact with the incompletely closed neural tube.


• Lipomyelomeningocele in 1-day-old girl with soft-tissue swelling on lower back. A and B, Longitudinal (A) and transverse (B) sonograms show lumbosacral dysraphism through which spinal cord (straight arrow), hyperechoic fatty tissue (curved arrow), and hypoechoic CSF (arrowhead, B) pass. C, T1-weighted sagittal MR image confirms lumbosacral dysraphism with intra- and extradural adipose tissue (arrows), neural tissue (arrowhead), and tethered cord.


Fatty Filum and Filar Fibrolipoma• Fatty filum and filar lipomas are due to a minor anomaly of

canalization and retrogressive differentiation with persistent or dedifferentiated fatty tissue.• It is considered a normal variant when it is an isolated finding in a

normal size filum (< 1–2 mm). When the fatty tissue forms a mass, a filar lipoma is diagnosed.• Associated anomalies 1. Myelomeningocele 2. Tethered cord.


• Fatty filum in 23-week-old boy with sacral dimple who is otherwise developmentally normal. A, Longitudinal sonogram shows focus of segmental increased echogenicity within filum (arrowhead) posterior to L4 vertebral body. B, Axial T1-weighted MR image confirms fat in filum as localized area of increased signal intensity (arrowhead).


Caudal Regression Syndrome

• Caudal regression syndrome, which is thought to be due to abnormal mesodermal formation of the caudal cell mass (possibly from hyperglycemia).

• It occurs most often in children of diabetic mothers • Associations:

1. Genitourinary2. Anal3. Vertebral4. Limb anomalies.

• The presentation and imaging appearance vary with the degree of deformity, ranging from minimal to severe regression of the coccyx, sacrum, and lumbar spine.

• Progressive absence of bone structures occurs in a caudal to cranial direction.


• Caudal regression syndrome in 3-day-old girl of diabetic mother. A, Longitudinal sonogram shows blunted distal cord (arrow), typical of caudal regression syndrome. B, Sagittal T1-weighted MR image confirms blunted conus medullaris and associated fat in filum (arrow) as well as absence of sacrum and coccyx (arrowhead).


Subdural Hematoma

• Subdural hematoma is uncommon in neonates;• it may be iatrogenic after failed attempts at neonatal lumbar

puncture.• Sonography is useful to determine whether the thecal sac is

compressed by a hematoma.

• Sonography can be used to determine the best timing and level for a potential reattempt at lumbar puncture.


• Fig. 7—Subdural hematoma in febrile 2-month-old boy after multiple attempts at lumbar puncture. A, Longitudinal sonogram identifies hemorrhage as circumferential, echogenic material in subdural space (straight arrow) that displaces dura (curved arrows) from posterior elements (arrowhead) and collapses normal CSF-containing thecal sac. B, Transverse sonogram also reveals circumferential echogenic subdural blood (arrows) obliterating normal CSF, which contains thecal sac.


Conclusion

• Modern sonography technology allows• Accurate screening• Characterization of spinal abnormalities during the first few days of

life. • It is useful for determining the type of lesion present in order to guide

the type and timing of intervention.


THANK YOU

ultrasound of spinal cord in neonates dr. muhammad bin zulfiqar

Health & Medicine