Posterior fossa syndrome.

Transient mutism is a well-recognized sequela of posterior fossa tumor resection in children. A recent review from our institution indicated that 12 of 142 children undergoing such procedures (8.5%) exhibited transient speech impairment, the largest series of such patients reported to date. Each child had a vermian neoplasm that was approached by division of the inferior vermis (n = 10) and/or superior vermis (n = 3). Seven children had medulloblastomas, three had astrocytomas, and two had ependymomas. None of the affected children had cerebellar hemispheric lesions; in contrast, the incidence among children with vermian neoplasms was 13%. In general, mutism developed 1 to 4 days postoperatively and typically was associated with puzzling neurobehavioral abnormalities. All children had bizarre personality changes, emotional lability, and/or decreased initiation of voluntary movements; nine exhibited poor oral intake; and five had urinary retention. Detailed neuropsychological testing was performed in seven children and confirmed the presence of widespread impairments not only in speech, but also in initiation of other motor activities. These deficits generally resolved during a period of several weeks to months, although two children had residual impairment. Characteristically, affect and oral intake normalized before the speech began to improve. These deficits were noted to correlate with the presence of edema within the brachium pontis bilaterally, although this association was not absolute. The latter observation suggests that there was not a single locus underlying this disorder, but rather that the involved neural pathways may have been impaired at any one of a number of sites within the posterior fossa. Based on the results in our patients and in others described in the literature, we postulate an important role for the cerebellum and/or its afferent and efferent connections in initiating (rather than merely coordinating) speech and other complex motor activities and a potential role for these structures in influencing overall behavior and affective state.