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[Intracranial arachnoidal cysts--some neuropsychological experiences].

Arachnoid cysts may cause neurological symptoms. The aim of this study was to investigate whether they also affect cognition. 31 patients (26 males and five females) underwent decompressive surgery for a symptomatic cyst in the left temporal fossa, with craniotomy and fenestration or with a cystosubdural shunt. The patients were tested for asymmetries in verbal perception and verbal memory before and after surgery, using dichotic listening techniques with different auditory stimuli presented simultaneously to the two ears. In the preoperative perception (dichotic listening-DL) test, the patients failed to show the normal advantage for auditory input to the right ear. After decompression, their DL performance normalised, as they now had a right ear advantage. In the preoperative dichotic memory test, the patients differed significantly from a normal reference group in two respects: they remembered fewer words, and they exhibited a clear left ear advantage, in contrast to the normal right ear advantage seen in the reference group. Postoperatively, overall memory performance was enhanced, and the preoperative superiority of the left ear had changed to a normal right ear advantage. The results indicate that arachnoid cysts in the left temporal fossa impair cognition, that neuropsychological tests are required to disclose such impairments, and that decompressive surgery improves cognition.