Mutism and Cerebellar Dysarthria after Brain Stem Surgery

Abstract

Transient mutism resolving to cerebellar speech after posterior fossa surgery is a well-recognized phenomenon, particularly in pediatric patients. The anatomic basis for this postoperative functional change is unclear but may reside in the dominant superior cerebellar hemisphere or the medial deep cerebellar nuclei. We report a case of an 8-year-old girl who presented for surgical resection of a cavernous malformation of the right pons (at the level of the middle cerebellar peduncle) after hemorrhage. Preoperatively, her complaints consisted of contralateral motor deficits. She had normal speech. Her lesion was resected through a subtemporal approach to the pons. She awoke unable to speak. She was able to communicate through a variety of verbal cues, including sign language. Her mutism lasted 12 days after which she underwent a prolonged period of slowly resolving cerebellar dysarthria. Her preoperative motor deficits also slowly resolved. This is the first reported case of mutism resolving to cerebellar dysarthria after a supratentorial approach to the brain stem. We discuss the anatomic basis for postoperative mutism in light of previous observations combined with the unusual finding of mutism after pontine surgery. In particular, reports of mutism after bilateral cerebellar hemispheric injury, bilateral or unilateral medial deep nuclear injury, and, now, pontine tegmental injury implicate the superior cerebellar hemispheres, the deep cerebellar nuclei, and the nuclear outflow through the superior cerebellar peduncle as the anatomic bases for cerebellar participation in the production of human speech.