Adult rhombencephalosynapsis. Case report.

Rhombencephalosynapsis (RS) is a relatively rare developmental disorder of the cerebellum in which the cerebellar hemispheres are fused across the midline without being separated by a cleft or the vermis. The condition may be associated with hydrocephalus and other intracranial and extracranial abnormalities. The authors report on the case of a symptomatic adult who was successfully treated with suboccipital decompression and duraplasty. A 39-year-old woman presented with intractable pain radiating from the thoracolumbar column to the occiput. A general examination yielded normal findings and a neurological examination revealed only subtle ataxia of tandem gait. The patient underwent magnetic resonance (MR) imaging, the results of which revealed an absent cerebellar vermis with fusion of the cerebellum and mild hydrocephalus. A cine-MR image obtained to evaluate her cerebrospinal fluid flow (CSF) revealed attenuated flow in the posterior fossa and cerebral aqueduct. Preoperative intracranial pressure (ICP) monitoring demonstrated no elevation of ICP (mean 4.3 mm Hg). The patient consented to undergo suboccipital craniectomy and duraplasty. Despite an increase in postoperative ICP (mean 10.77 mm Hg; difference from preoperative level according to a t-test, p = 0.002), the patient experienced symptomatic relief, which has persisted for 3 years. One year postoperatively, a cine-MR image was obtained, which revealed improvement in the patient's CSF dynamics. The authors conclude that, although RS may cause altered flow in the adult, their patient has experienced symptomatic relief, suggesting that her pain was related to local pressure in the posterior fossa.