|
|
| Images
below require Macromedia's Flash Player to view |
 |
Neuroradiology Case of the Week
Case 437
September 2009
Sara Ann Majewski, MD
Clinical
Presentation: Newborn female presented with large extra-thoracic mass. Evaluation was requested for mesenchymal cyst versus myelomeningocele.
Imaging Findings: See below
|
Figure 1: AP babygram radiograph shows absence of most of the right ribs, hypoplastic thoracic vertebral bodies, S-shaped thoracolumbar scoliosis and large soft tissue mass protruding from the patient's back in the thoracic region.
|
|
Figure 2: Sagittal T2-weighted MRI shows posterior herniation of a fluid-filled sac having cerebral spinal fluid signal containing stretched and elongated spinal cord. The spinal cord returns to the spinal canal, regains normal morphology and terminates at L2.
|
|
|
Figure 3: Axial T2-weighted MRI images again shows posterior herniation of a fluid-filled sac with CSF signal containing spinal cord. The posterior elements of the vertebral bodies are absent.
|
|
Figure 4: Sagittal T1-weighted image of the brain demonstrates a small posterior fossa and probable cerebellar tonsillar herniation likely representing a Chiari II malformation. |
Diagnosis: Myelomeningocele
Discussion: A myelomeningocele is a protrusion of the leptomeninges through a spinal canal defect containing cerebral spinal fluid and variable neural tissue. It is caused by nonclosure of the caudal neuropore. Elevated maternal serum alphafetoprotein is found in the majority of cases and most can be found on obstetrical ultrasound. Most myelomeningoceles are found in the lumbosacral, lumbar and thoracolumbar spines.
Common associations include hydrocephalus, Chiari II malformation, congenital or acquired kyphoscoliosis, vertebral anomalies, tethered spinal cord and hydromyelia. Diastematomyelia, duplicated spinal canal, hemimyelocele, chromosomal abnormalities and arachnoid cyst are less commonly found.
Motor and sensory loss are variable, many times asymmetric, and often do not correspond to the spinal level of the myelomeningocele. Paralysis is more commonly flaccid than spastic. Cranial nerve dysfunction can be associated with Chiari II malformation, hydrocephalus and brainstem dysplasia.
Thoracic myelomeningocele demonstrates variable innervation of the neck and superior trunk. There is typically no voluntary movement in the lower extremities. There is more severe central nervous system and cognitive deficits at the thoracic level than at lower levels.
Lateral thoracic meningocele can present in neurofibromatosis or kyphoscoliosis. The meningeal herniations typically protrude through the intervertebral foramina and extend anteriorly between the ribs into the thoracic cavity (unlike the case presented above). These are associated with arachnoid cysts and are not typically related to spinal dysraphic lesions.
Closure of the myelomeningocele is usually performed within the first 2 days of birth unless there is a cerebral spinal fluid leak which requires immediate surgery after birth. Ventriculoperitoneal shunting is used in patients with hydrocephalus and shunt complication can result in seizures or infection. Later in life, surgical release of tethered cord may need to be performed in the region of the myelomeningocele repair. Dural scarring and mass effect from a lipoma, dermoid or epidermoid cyst can also cause complications postoperatively. Orthopedic intervention may be needed for kyphosis and scoliosis as well as contracture release. Bladder dysfunction can require intermittent catheterization or vesicostomy. Patients also experience bowel dysfunction.
References:
- Dahnert W. Radiology Review Manual. Lippincott, Williams & Wilkins: Philadelphia, 2007.
- Khan A. Spinal dysraphism/myelomeningocele. E-medicine. February 20, 2007. http://www.emedicine.com/radio/topic643.htm
- Kolaski K. Myelomeningocele. E-medicine. April 20, 2006. http://www.emedicine.com/pmr/TOPIC83.HTM
|
