SPINAL CORD MALFORMATIONS
Apart from major neural tube defects, e.g. meningomyelocele (Chapter 18.9.1), other important malformations of spinal cord, which usually present in later life, are as follows:
Syringomyelia, i.e.
cystic dilatation of the central canal, may be congenital or acquired after cord tumors, trauma or infections. Congenital syrinomyelia is frequently associated with Arnold-Chiari malformation and communicates with CSF pathway, while acquired lesions are generally non-communicating. Syringobulbia is the similar lesion in medulla.Clinically, most cases present beyond childhood due to slowly progressive dilatation of central canal with -
(a) dissociate anesthesia, i.e. loss of pain and temperature sense without light touch, due to spinothalamic tract involvement and (b) spastic motor lesions below the lesion due to compression of corticospinal tracts.
Diagnosis rests on MRI or Metrizamide CT scan and management includes surgical decompression of cystic cavity, depending on the site and etiology.
Diastematomyelia is a neural tube defect due to vertical division of the spinal cord into two halves by a fibrocartilagenous or bony projection from the posterior vertebral body, commonly at L1-3 levels. These cases may be asymptomatic or present with low backache and progressive sensory/motor lesions in lower limbs.
Diagnosis rests on CT/MRI and symptomatic cases need surgical intervention with excision of bony spur/ septum and lysis of adhesions.
Tethered cord syndrome: In utero, spinal cord occupies the entire vertebral canal, but postnatal differential growth leads to regression of distal end, i.e. conus medullaris till L1 level. Normally, this conus is attached to coccyx with a slender thread like filum terminale.
A tethered cord denotes persistence of a thick rope like filum terminale that anchors the conus at or below L2, leading to abnormal traction and vascular compromise during spinal bending movements.
Clinically, these cases are asymptomatic or present at any age with diffuse pains and muscle wasting in lower limbs, bladder/bowel dysfunction with overflow incontinence and progressive scoliosis. Midline skin lesions, e.g. pits or tuft of hair, are common over spine.
Diagnosis may be confirmed on MRI and treatment involves surgical transaction offilum terminale.
18.16.4