Clinical study of chronic arachnoiditis in the posterior fossa.

A series of 12 cases of chronic arachnoiditis in the posterior fossa is reported. The diagnosis in six patients was established at suboccipital craniectomy whch brought about marked improvement in symptoms. The other six were diagnosed as having arachnoiditis in the posterior fossa from the facts that improvement in clinical symptoms was achieved by lumbar air insufflation, which has often been said to be effective in arachnoiditis, and no abnormal findings were revealed by pneumoencephalo-roulette tomography. By investigating the clinical features of these cases, we came to the following conclusions: many cases of this disease have had head trauma or chronic inflammatory disease in the past; the symptoms are apt to occur abruptly, and display repeated remission and aggravation; symptoms originating in the cranial nerves are diversified, and are often bilaterial; peripheral vestibular disturbances and retrocochlear hearing losses are observed on neuro-otological examination. In the caloric test especially the patients show canal paresis (CP) on the more impaired side, but none of them appeared to be nonresponsive to the test; lumbar air insufflation is often an effective treatment for this disease; pneumoencephalo-roulette tomography is very useful for diagnosing pathological changes in the posterior fossa.