Cognitive function has not been well studied after neurosurgery for posterior fossa lesions despite its potential importance in determining surgical indications and approaches. The present study evaluated changes in cognitive functions after posterior fossa surgery to detect any differences between the mid- dle cranial fossa and lateral suboccipital approaches in 50 patients with posterior fossa lesions such as tumors and vascular diseases. Twenty-five patients underwent surgery via the middle fossa and 25 via the lateral suboccipital approaches. Computerized test battery (CogState™) and conventional neuropsy- chological tests (serial seven-word learning test and mini-mental state examination) were examined be- fore, 1 month after, and 3 months after surgery. All scores of the neuropsychological tests remained wi- thin normal limits after surgery. However, the scores of one computerized test battery and serial seven- word learning tests decreased significantly 1 month after surgery and recovered within 3 months, in- dicating temporary deterioration of short-term memory in the middle fossa group. The computerized tests detected significantly larger numbers of patients with worsened results than the conventional tests. The middle fossa approach and operation time showed correlations with the postoperative neu- ropsychological declines. The computerized tests could be performed easily and were beneficial for de- tecting subtle changes of the cognitive function after surgery. Cognitive function, especially short-term memory, may decline temporarily with the middle fossa approach and long operation time.
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