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<0.001) in picaCH pattern than other patterns. Dysarthria was less frequent in picaCH pattern than in other patterns (P=0.018) and less severe than in scaCH (P=0.0043) or CP (P=0.0047) pattern. No differences in nystagmus frequency or severity were observed across all four patterns. CONCLUSION: In PC stroke gait ataxia was almost always present, regardless of the lesion site. Limb ataxia and dysarthria were less frequent in the picaCH pattern, whereas nystagmus, when present, did not differ among the topographical patterns.