CONTRALATERAL AND IPSILATERAL EMC RESPONSES TO TRANSCRANIAL MAGNETIC STIMULATION DURING RECOVERY OF ARM AND HAND FUNCTION AFTER STROKE

We examined the relationship between the recovery of hand and arm func tion in a group of hemiplegic stroke patients and the presence of shor t-latency EMG responses to transcranial magnetic stimulation (TMS) in 4 different upper limb muscles (deltoid, biceps, extensor digitorum co mmunis and the first dorsal interosseous). Twenty-one patients were ex amined within 5 weeks of stroke (median 2 weeks), and then at regular intervals over the next 12 months. Some patients recovered rapidly (Gr oup A); in others, recovery was slow and incomplete (Group B). Even at the first test, Group A patients had responses to TMS in all muscles. Most Group B patients initially lacked responses in all tested upper limb muscles; in those that later were able to activate hand muscles, responses returned at or just before this stage of recovery. No such c lear correlation between the presence of responses to TMS and ability to activate more proximal arm muscles was evident. Response latency wa s initially long and declined in a manner that was highly correlated w ith muscle strength and hand function test scores. Ipsilateral respons es were elicited from both the affected and unaffected hemispheres. Ip silateral responses from the latter were most common in the proximal m uscles of the affected limb, and had latencies that were longer than t hose elicited in the contralateral (unaffected) arm. Nine cases of ips ilateral responses in hand muscles were found; such responses are not found in healthy subjects. Ipsilateral responses from the undamaged he misphere were more prevalent in the poorly recovered patients; the und erlying mechanisms may not be beneficial for recovery.