Ataxia in posterior circulation stroke: Clinical-MRI correlations.

OBJECTIVE: Ataxia is characterized clinically by four signs (gait and limb ataxia, dysarthria and nystagmus). Although ataxia has been described in posterior circulation (PC) stroke series, there are no prospective studies that have investigated a possible differential role of the cerebellum or its input/outputs in causing ataxia. METHODS: Ataxia was semi-quantified according to the International Cooperative Ataxia Rating Scale (ICARS) in 92 consecutive patients with acute PC stroke. Four topographical patterns based on magnetic resonance imaging (MRI) findings were identified: picaCH pattern (posterior inferior cerebellar artery infarct); scaCH pattern (superior cerebellar artery infarct); CH/CP pattern (infarct involving both the cerebellum and the brainstem cerebellar pathways); and CP pattern (infarct involving the brainstem cerebellar pathways). RESULTS: Gait ataxia was present in 95.7\%, limb ataxia in 76.1\%, dysarthria in 56.5\% and nystagmus in 65.2\% of patients. Gait ataxia frequency did not differ between the patterns, but was significantly more severe in the CH/CP pattern than in either picaCH (P=0.0059) or CP (P=0.0065) pattern. Limb ataxia was significantly less frequent (P<0.001) and less severe (P