Leg weakness due to stroke Site of lesions, weakness patterns and causes

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Abstract
SummaryAmong 1575 patients with an acute stroke, 63 (4%) were found to have a leg-predominant weakness. The cerebral lesions were situated in (i) the anterior cerebral artery (ACA) territory in 12 cases, including one patient with a thrombosis of the sagittal sinus; (ii) the middle cerebral artery (MCA) territory in nine cases; (iii) both territories (not watershed) in two cases; (iv) the internal capsule in 18 cases, of which six cases had lesions in the ponto-peduncular or pontine; (v) other brainstem regions in 10 cases; (vi) the thalamus in two cases. Four were not precisely classified. In short, 41 were hemispheric and 18 were in the brainstem or thalamus. Lesions restricted to the rear portion of the medial part of the precentral gyrus caused a contralateral predominantly distal leg weakness. The weakness was severe with little improvement. Lesions involving the medial part of the premotor cortex, the supplementary motor area (SMA) and the rear portion of the medial part of the precentral gyrus caused a contralateral, severe leg-predominant hemiplegia, distally predominant and a less severe proximal weakness of the arm. Recovery was much better for the arm than for the leg. Lesions affecting the medial part of the premotor cortex, the SMA and sparing the precentral gyrus caused a contralateral hemiparesis predominating on the leg but predominating proximally on both leg and arm. Recovery was good for leg and arm. There were 22 infarcts due to ACA or MCA occlusion, one due to superior sagittal sinus occlusion, 18 lacunes and five haemorrhages. Ten infarcts in the ACA territory were due to embolism and contrary to previous reports, there was only one case suggesting a haemodynamically determined infarction. Lesions in the internal capsule caused proportional weakness of the leg. Lesions in the brainstem caused mostly proportional leg weakness. They suggested a somatotopic organization of the pyramidal tract, the leg fibres being probably dorsolaterally situated and the arm fibres ventromedially. The somatotopic arrangement of the pyramidal fibres in the pons remains so far, poorly known. There were two cases of proximal limb weakness, one in the leg and one in the arm, due to a pontine lesion. They suggested an involvement of the cortico-reticular tract.

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