Chiari malformation in adults: relation of morphological aspects to clinical features and operative outcome.

To determine whether clinical features attributed to cerebellar ectopia could be related to the severity of the malformation, and if morphological features could be related to operative outcome, a retrospective study of 141 patients with the adult Chiari malformation was carried out, 81 receiving operative treatment. Morphological parameters derived from preoperative clinical imaging were compared with presenting clinical features and postoperative outcomes. Patients with the most severe cerebellar malformation, defined as descent of the cerebellar tonsils to or below the axis, had disabling ataxia and nystagmus more frequently. Those with brainstem compression had limb weakness and muscle wasting more frequently. Operative outcome was significantly less favourable in patients with severe cerebellar ectopia (12% improved, 69% deteriorated) than in those with minor ectopia (50% improved, 17% deteriorated). Patients with a distended cervical syrinx had a more favourable outcome than those without. Morphological features help predict operative risk.