Intrathoracic meningocele. Its development and association with neurofibromatosis.

An antero-lateral meningocele is a protrusion of the spinal meninges through an intervertebral foramen. It contains an extension of the subarachnoid space, filled with cerebrospinal fluid, and this gives rise to a paravertebral cystic swelling, usually spherical in shape. Theoretically such a swelling could occur in the neck, or in the thoracic, abdominal, or pelvic cavities, but practically all the recorded cases (and we have discovered only 66 in literature) have occurred in the thoracic cavity and are there referred to as intrathoracic meningoceles. A feature of the abnormality is that nearly twothirds of the recorded cases have occurred in association with neurofibromatosis. It has thus been of especial interest to neurological and thoracic surgeons because of the differential diagnosis from dumb-bell neurofibroma-that is, a neurofibroma beginning on a spinal nerve root, enlarging in the vertebral canal, extending out through the intervertebral foramen and enlarging again in the paravertebral space. Indeed the original observation by Pohl (1933) concerned a 47-year-old woman with von Recklinghausen's disease who was mistakenly thought to have an intrathoracic neurofibroma. The majority of the recorded cases have come into the hands of thoracic surgeons, and the increasing practice of mass radiography of the chest may be expected to provide more cases in the future. Because of their rarity, little is known about the natural history of intrathoracic meningoceles and, that being the case, the indications for treatment and the most effective methods of treatment are by no means clear. We have not encountered a comprehensive review of the literature. We present below a report of four cases seen in the Department of Neurological Surgery, Radcliffe Infirmary, Oxford, during the past 18 years, together with a review of the literature, a discussion of the