Epilepsy associated with a cerebellar arachnoid cyst: seizure control following fenestration of the cyst.

OBJECTIVE: The role of the cerebellum in the pathogenesis of seizures remains controversial. Cerebellar origin of seizures, albeit rare, has been described in the literature in association with intrinsic lesions of the cerebellum. We present a unique case of a patient with medically intractable, secondary generalized epilepsy, associated with a superior cerebellar quadrigeminal arachnoid cyst. CLINICAL
PRESENTATION: A 9-year-old child presented with medically refractory secondary generalized epilepsy associated with recurrent headaches since 6 months of age. The child also had moderate intellectual impairment and autism. On the magnetic resonance imaging (MRI) of the head, he was noticed to have a small superior cerebellar arachnoid cyst in the quadrigeminal area that had increased in size slightly. Interictal electroencephalograph (EEG) was unable to localize the site of the epilepsy. Neurological examination was unremarkable. INTERVENTION: A suboccipital craniotomy and supracerebellar infratentorial approach to the cyst was performed at 9 years of age. Intraoperative electrocorticography (ECOG) demonstrated epileptic activity from the cerebellar tissue adjacent to the cyst. The cyst was fenestrated, and the cyst wall was sent for histology. Seizure control improved dramatically after fenestration of the cyst.
CONCLUSION: This case provides strong evidence that, albeit rare, the cerebellum may be a source of epileptic activity due to compression by a lesion in the posterior fossa. Hence, in cases with intractable epilepsy of unknown supratentorial source, the differential diagnosis should include a posterior fossa lesion. The finding of a posterior fossa lesion in such cases, even if it is small and appears benign, should precipitate a discussion about the possible relationship between the posterior fossa lesion and the epilepsy.