Spina Bifida Occulta

In Spina Bifida Occulta, though there is failure of the neural arches to unite, and a small gap exists in one of the vertebral arches, usually in the lumbar or sacral regions, yet there is no protrusion of the cord or membranes. Frequently only one vertebra is affected. Te gap is filled with fibrous tissue.

As a rule, there is no projection on the surface to indicate this defect, though a local patch of hair, a naevo-lipoma or a depression in the skin may suggest the underlying bony deficiency.

A fibrous band, the membrana reunions connects the skin to the spinal theca. At one stage the spinal cord reaches the distal end of the vertebral column. Gradually the cord lags behind in growth in comparison to the vertebral column in intrauterine life, so that at birth the distal end of the cord lies at the third lumbar vertebra.

Later on due to more development of the vertebral column, the distal end of the cord lies at the lower end of the first lumbar vertebra in adults. With the growth of the body the membrana reunions pull on the theca and nerve roots. This causes some neurological deficiencies e.g. foot drop, nocturnal enuresis or backache. Such symptoms appear late in childhood or in adult life.

Many cases of spinal bifida occulta are symptomaless. Either they remain undiagnosed or diagnosed by accident when an x-ray taken for some other reasons.

Clinical Features

1. Present since birth
2. There is some abnormality in the local skin either a skin dimple or a local patch of hair or a naevo-lipoma or simple lipoma.
3. Neurological examinations must be performed, as in adolescent or in adult life manifestations of such deficiency may be revealed in the form of backache, nocturnal enuresis, local anaesthesia, local paresis or even foot drop.
4. X-ray is often confirmatory as it will show the bony defect.

Treatment

If there is any symptom, operation may be performed

1. Presence of tuft of hair or lipoma may lead to cosmetic complaint and this is treated by excision of these lesion.
2. If there are neurological symptoms due to membrana reunions, the membrana reunions is excised in its whole length from the skin though the vertebral gap to the spinal meninges.
3. Orthopaedic, urological or neurological symptoms may not be due to traction by the membrana reuniens alone, but are more likely to be due to compression of the cord by extradural or intradural lipomas. Such lesions should be excised. Sometimes a condition called diastematomyelia, in which the cord is split in the midline by a bony spur may be seen. This abnormality is usually associated with presence of tuft of hair on the overlying skin. Myelography should always be performed before the operation.

Related posts:

1. Spina Bifida-An Overview
2. Meningomyelocele
3. Syringomyelocele and Myelocele
4. What Is Cauda Equina?
5. Understanding Spinal injury – Vertebral level and Spinal Level