Diffusion weighted imaging in ataxic hemiparesis

Objective: Ataxic hemiparesis (AH) is a well recognised lacunar syndrome involving homolateral ataxia with accompanying corticospinal tract impairment. Most previous studies of lesion location in AH did not use diffusion weighted MRI (DW MRI). The purpose of this study was to use DW MRI to evaluate the radiological correlation in patients presenting with AH. Methods: Retrospectively, we studied 29 patients with AH using DW MRI. Results: All patients were scanned within 4 days of onset. Acute infarction was identified in 28 of 29 (97%) patients. A single lesion was identified in 26 patients: pons (n = 8), internal capsule (n = 6), corona radiata (n = 2), distended internal capsule from corona radiate (n = 7), frontal subcortical area (n = 1) and precentral with or without postcentral gyrus (n = 2). Two lesions were found in two patients: in the pons and corpus callosum of one patient, and in the corona radiata and subcortical white matter of the other. Conclusions: AH is mainly caused by pontine or internal capsule/corona radiata lesions. It also occurs in the precentral gyrus, including the precentral knob, with or without postcentral gyrus lesions. Fibres of the fronto-ponto-cerebellar system may originate from the frontal cortex, including the precentral gyrus, probably near the pyramidal tract. Damage at this location may cause AH.