Ipsilateral responses after a stroke : an electrophysiological study by focal TMS

peer reviewe

Impairment of neuromuscular transmission in a subgroup of migraine patients

Neuronal voltage-dependent P/Q Ca2+ channels are genetically abnormal in many cases of familial hemiplegic migraine and possibly associated with the more common forms of migraine with and without aura. Besides the brain, these channels are found in motor nerve endings where they control stimulation-induced acetylcholine release. Using single fiber EMG recordings we were able to demonstrate subclinical abnormalities of neuromuscular transmission in a subgroup of patients suffering from migraine with aura. This could be related to genetic abnormalities of P/Q Ca2+ channels in certain patients suffering from migraine with aura, which needs to be explored by proper genetic analyses

Motor cortex excitability in Alzheimer's disease and in subcortical ischemic vascular dementia.

Twenty Alzheimer's disease (AD) patients, 20 subcortical ischemic vascular dementia (SIVD) patients and 20 neurologically and cognitively normal subjects underwent transcranial magnetic stimulation to study motor cortex excitability changes. Motor threshold (MT), amplitude of motor evoked potentials, silent period and the H/M ratio (amplitude of maximal Hoffman reflex vs. that of maximal motor response) were considered. MT was lower in SIVD patients when compared with AD patients (P = 0.003) and the control group (P < 0.001) and lower in AD patients when compared with the control group (P < 0.001). The increment of motor cortex excitability in AD and SIVD did not lead us to distinguish clearly the two types of dementia. It is likely that the electrophysiological similarity between AD and SIVD could represent another common mechanism shared from these forms of dementia

Ipsilateral Motor Responses to Focal Transcranial Magnetic Stimulation in Healthy Subjects and Acute-Stroke Patients

peer reviewedBACKGROUND AND PURPOSE: Prevalence and characteristics of ipsilateral upper limb motor-evoked potentials (MEPs) elicited by focal transcranial magnetic stimulation (TMS) were compared in healthy subjects and patients with acute stroke. METHODS: Sixteen healthy subjects and 25 patients with acute stroke underwent focal TMS at maximum stimulator output over motor and premotor cortices. If present, MEPs evoked in muscles ipsilateral to TMS were analyzed for latency, amplitude, shape, and center of gravity (ie, preferential coil location to elicit them). In stroke patients, possible relationships between early ipsilateral responses and functional outcome at 6 months were sought. RESULTS: With relaxed or slightly contracting target muscle, maximal TMS over the motor cortex failed to elicit ipsilateral MEPs in the first dorsal interosseous (FDI) or biceps of any of 16 normal subjects. In 5 of 8 healthy subjects tested, ipsilateral MEPs with latencies longer than contralateral MEPs were evoked in FDI muscle (in biceps, 6 of 8 subjects) during strong (>50% maximum) contraction of the target muscle. In 15 of 25 stroke patients, ipsilateral MEPs in the unaffected relaxed FDI (in biceps, 6 of 25 stroke patients) were evoked by stimulation of premotor areas of the affected hemisphere. Their latencies were shorter than those that MEPs evoked in the same muscle by stimulation of the motor cortex of the contralateral unaffected hemisphere. Such responses were never obtained in normal subjects and were mostly observed in patients with subcortical infarcts. Patients harboring these responses had slightly better bimanual dexterity after 6 months. CONCLUSIONS: Ipsilateral MEPs obtained in healthy individuals and stroke patients have different characteristics and probably different origins. In the former, they are probably conveyed via corticoreticulospinal or corticopropriospinal pathways, whereas in the latter, early ipsilateral MEPs could originate in hyperexcitable premotor areas

Ipsilateral motor responses to focal transcranial magnetic stimulation in healthy subjects and acute-stroke patients

peer reviewedBACKGROUND AND PURPOSE: Prevalence and characteristics of ipsilateral upper limb motor-evoked potentials (MEPs) elicited by focal transcranial magnetic stimulation (TMS) were compared in healthy subjects and patients with acute stroke. METHODS: Sixteen healthy subjects and 25 patients with acute stroke underwent focal TMS at maximum stimulator output over motor and premotor cortices. If present, MEPs evoked in muscles ipsilateral to TMS were analyzed for latency, amplitude, shape, and center of gravity (ie, preferential coil location to elicit them). In stroke patients, possible relationships between early ipsilateral responses and functional outcome at 6 months were sought. RESULTS: With relaxed or slightly contracting target muscle, maximal TMS over the motor cortex failed to elicit ipsilateral MEPs in the first dorsal interosseous (FDI) or biceps of any of 16 normal subjects. In 5 of 8 healthy subjects tested, ipsilateral MEPs with latencies longer than contralateral MEPs were evoked in FDI muscle (in biceps, 6 of 8 subjects) during strong (>50% maximum) contraction of the target muscle. In 15 of 25 stroke patients, ipsilateral MEPs in the unaffected relaxed FDI (in biceps, 6 of 25 stroke patients) were evoked by stimulation of premotor areas of the affected hemisphere. Their latencies were shorter than those that MEPs evoked in the same muscle by stimulation of the motor cortex of the contralateral unaffected hemisphere. Such responses were never obtained in normal subjects and were mostly observed in patients with subcortical infarcts. Patients harboring these responses had slightly better bimanual dexterity after 6 months. CONCLUSIONS: Ipsilateral MEPs obtained in healthy individuals and stroke patients have different characteristics and probably different origins. In the former, they are probably conveyed via corticoreticulospinal or corticopropriospinal pathways, whereas in the latter, early ipsilateral MEPs could originate in hyperexcitable premotor areas