Critical risk factors for intellectual impairment in children with posterior fossa tumors: the role of cerebellar damage.

Object. Intellectual impairment is a major concern after treatment of malignant posterior fossa tumors in children. The effects of age at diagnosis and radiotherapy have been widely documented. Little is known, however, about perioperative factors, especially neurological damage to the cerebellum, the role of which in cognition and learning has been recently indicated. The authors studied the effects in 76 children treated for a malignant posterior fossa tumor in a cross-sectional study. Methods. Two thirds of the tumors were medulloblastoma. Neuropsychological evaluation was performed at least 6 months after the end of treatment, and findings were correlated with clinical risk factors for intellectual impairment. The mean verbal intelligence quotient (VIQ) score was 87 19 (+/- standard deviation) and the mean performance IQ (PIQ) score was 76 +/- 17.5. A single neuropsychological test measuring hand skills (the Purdue Pegboard) was the strongest predictor of low IQ scores including items testing higher cognitive functions. A low VIQ was associated with impaired hand skills (p < 0.0001) and the presence of preoperative hydrocephalus (p = 0.02), whereas a low PIQ was associated with impaired hand skills (p < 0.0001) and incision of the vermis (p = 0.02). Impaired hand skills were associated with postoperative cerebellar mutism, oculomotor deficits, cerebellar syndrome, and therapeutic requirements. Conclusions. When treatment schedules are adapted to risk of disease and age, surgery-related risk factors then become critical for predicting intellectual impairment. Children with cerebellar damage are particularly at risk for long-term neuropsychological dysfunction and require active rehabilitation measures. Reducing surgery-related morbidity should be the next goal to reduce posterior fossa surgery-specific deficits.