Symptomatic foramen of Magendie arachnoid cyst in an elderly patient.

Background: Arachnoid cysts (ACs) are congenital anomalies of the central nervous system and arise in virtually all locations where the arachnoid membrane exists. Posterior fossa ACs are considered to develop in the posterior aspect of the rhombencephalic roof plate and do not communicate freely with the fourth ventricle or perimedullary subarachnoid space. Although posterior fossa ACs have been reported a number of times, ACs arising from the foramen of Magendie are very rare.

Case Description: We report here on a 76-year-old female who presented with progressive gait disturbance. Magnetic resonance imaging of the head showed a large AC in the foramen of Magendie that was compressing the inferior vermis and medial aspects of the cerebellar hemisphere without causing hydrocephalus. Neurological examination revealed cerebellar ataxia without Romberg's sign. A nearly total excision of the cyst was safely performed via a median suboccipital approach. The patient's postoperative course was excellent and her neurological recovery was remarkable.

Conclusion: Most cases of ACs located in the foramen of Magendie are reported in children, and it is extremely rare to observe such ACs in the elderly. In fact, to our knowledge, a symptomatic foramen Magendie AC has never been reported previously in an elderly person. Our results indicate that proper surgical intervention can yield highly positive outcomes in such cases.