Lipomyelomeningocele

Meningocele is an out pouching of leptomeninges through a developmental defect in the dura. The arches of the vertebrae at one or more levels are involved with protruded meningeal sac covered with only a layer of skin. The presence of spinal cord or cauda equina within the meningocele is termed myelomeningocele. This deformity mostly occurs at the stage of neuralation that prevents the neural groove from closing dorsally. One theory suggests that excessive overgrowth of neural tissue in the region of the spina bifida prevents the neural groove from fusing. Anterior sacral meningoceles are anomalies characterized by a focal erosion or hypogenesis of segments of the sacrum and coccyx with herniation of a CSF filled meningeal sac through the defect into the pelvis. They account for around 5% of retrorectal tumors and both sexes are equally affected. Lateral meningoceles have been described in the thoracic and lumbar region. They are extensions of dura and arachnoid through an enlarged neural foramen. They commonly present during fourth and fifth decade of life. Neurofibromatosis is present in approximately 85% of patients with lateral thoracic meningoceles. The position of the cord with respect to the meningocele sac is variable. They often occur in a setting of Marfan's syndrome or neurofibromatosis but may also be seen as isolated anomalies.
Lipomyelomeningoceles are lipomas that are tightly attached to the dorsal surface of a neural placode and extend dorsally through a spina bifida to be continuous with the subcutaneous fat. These lesions constitute approximately 20% of skin covered lumbosacral masses. Lipomyelomeningoceles usually occur in the lumbosacral region of the cord and tether the cord at the level. The dorsal surface of the placode, adjacent to the lipoma, has no ependymal lining and is covered by a relatively thick layer of connective tissue mixed with islands of glial and smooth muscle fibres. The lipoma lies immediately external to the connective tissue in the extradural space. Patients are typically female and present before the age of six months but occasionally the condition goes undetected into childhood. The clinical presentation can be with a soft mass, sensory or motor loss or bladder dysfunction. Symptoms are progressive if untreated.