OBJECTIVE: To study data concerning the pathogenesis, frequency of occurrence, clinical manifestations and associated abnormalities of spina bifida occulta (SBO) and re-evaluate the clinical importance of the lesion.

DATA SOURCES: International journal articles indexed through Medline, and specific related texts, the majority of which were published after 1989. Key indexing terms used were spina bifida occulta, tethered cord syndrome and spondylolysis.

RESULTS: The reported frequency of occurrence of SBO varies widely, depending largely on the age groups included in a particular study. The most accurate estimate of occurrence rate is 17% of examined spines. There is a significant association of some cutaneous stigmata, most notably hypertrichosis, with midline posterior arch defects. An increasing amount of evidence links SBO with a number of specific anomalies and clinical syndromes, including intraspinal lipoma, tethered cord syndrome, genitourinary dysfunction, increased incidence of disc pathology, lumbar spondylolysis, foot deformities and syringomyelia. A questionable association exists with epilepsy. A supposed link between constipation and SBO is lacking sufficient data to support it.

CONCLUSIONS: SBO may be associated with pathology and significant sequelae, although the majority of lesions pose no clinical threat. The predictive value for adverse sequelae in a particular lesion is difficult to assess; however, multilevel occurrence and more expansive involvement in a given segment seem to be associated with higher risk of sequela. The treatment for SBO with progressive neurologic deficit is surgical intervention; however, reversal of the deficit is unusual and a halting of neurologic deterioration is a more realistic goal. Early diagnosis of this lesion, before the age of 3 yr, is associated with better surgical outcomes.

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