Meningocele

Conversely, spinal meningoceles do represent independent entities and are further classified into simple meningocele, lateral meningocele and anterior sacral meningocele.

By simple meningocele is meant a herniation of the meninges into the subcutaneous tissue of the back with overlying intact skin. Simple meningocele is more frequently observed in the sacral region and is usually associated with relatively mild bony defects such as the absence of a single spinous process or a uni- or multifocal spina bifida. Its embryogenetic origin is unexplained. Sometimes a nerve root may loop into the sac and may also adhere to the sac wall, whereas the filum terminale may attach to the neck of the sac.

Lateral meningoceles are protrusions of the meninges through dilated neural foramina. 85% of cases occur in the context of neurofibromatosis type I. Lateral meningoceles are more frequently thoracic, they may vary in size from small almost undetectable protrusions to enormous cysts filling an entire hemithorax and compromising ventilation of the neonate. Scoliosis is often associated and is convex with respect to the meningocele that lies at its apex. In neurofibromatosis meningoceles are often multiple. Lumbar meningoceles are less frequent, they also usually occur in a setting of neurofibromatosis or Marfans syndrome and only occasionally they are incidental. Lateral meningoceles are most frequently asymptomatic and do not tend to enlarge.

Anterior sacral meningocele is an anterior protrusion of the meninges through a focal erosion or hypogenesis of a segment of the sacrum and coccyx. They must be borne in mind in the differential diagnosis of retrorectal tumours of which they represent around 5% of cases. They are usually diagnosed in the second or third decade of life following symptoms produced as the result of pressure on the pelvic viscera such as constipation, urinary frequency and incontinence, dysmenorrhoea, dyspareunia, or pain in the lower back or pelvis. They may also cause radicular pain.

FS