Spina bifida occulta

Spina bifida occulta is the mildest form of spina bifida/spinal dysraphism and is a type of neural tube defect.

Terminology

While typically referring to asymptomatic posterior fusion defects, some authors use it as a broad term that encompasses closed spinal defects such as:

diastematomyelia
diplomyelia
dorsal dermal sinus
spinal lipoma
posterior neural arch defects, namely spinous and paraspinal clefts

Epidemiology

Spinda bifida occulta is the commonest form of spina bifida and is estimated to affect between 10-20% of the population in most western countries.

Clinical presentation

As there is overlying skin covering the vertebral defect and no associated developmental abnormalities of the cord or nerve roots, there are no usually no accompanying neurological symptoms found.

Pathology

Spina bifida occulta is a congenital defect which occurs in the neural tube when the bony plates that form the bony spine covering the spinal cord do not form completely resulting in a defect of the spinous process (spinous cleft) or laminae (paraspinal cleft) . This usually involves the lower lumbosacral spine.

Radiographic features

Plain radiograph

Appears as a midline or para-midline bony defect at the posterior arch.

MRI

This is the test of choice to assess for suspected spina bifida and determine its extent.