Transcranial cortical stimulation in disorders of the central motor pathways (original) (raw)
Related papers
1987
The complexities of interpreting results of electrical stimulation of the motor cortex in pathological states are discussed and illustrated by reference to results from a variety of patients with diseases affecting the upper motor neurone (multiple sclerosis, cervical spondylosis and myelopathy, motor neurone disease, hemiparesis due to cerebral infarction, and hereditary spastic paraplegia). The abnormalities of the electromyographic (EMG) responses after anodal cortical stimulation consisted of delay in the latency to onset, dispersion or reduction in response size or even absence of EMG responses. These changes were not confine6 to any specific condition or pathology. Previous work has suggested that the sequence of events that follow anodal cortical stimulation involves repetitive excitatory inputs to spinal motoneurones and transmission across at least one central synapse. Accordingly, delayed latencies may not exclusively indicate slowing of motor conduction, while the absence of any response may not indicate complete failure of conduction in corticomotoneurone pathways.
A clinical study of motor evoked potentials using a triple stimulation technique
Brain, 1999
Amplitudes of motor evoked potentials (MEPs) are usually much smaller than those of motor responses to maximal peripheral nerve stimulation, and show marked variation between normal subjects and from one stimulus to another. Consequently, amplitude measurements have low sensitivity to detect central motor conduction failures due to the broad range of normal values. Since these characteristics are mostly due to varying desynchronization of the descending action potentials, causing different degrees of phase cancellation, we applied the recently developed triple stimulation technique (TST) to study corticospinal conduction to 489 abductor digiti minimi muscles of 271 unselected patients referred for possible corticospinal dysfunction. The TST allows resynchronization of the MEP, and thereby a quantification of the proportion of motor units activated by the transcranial stimulus. TST results were compared with those of Keywords: collision technique; corticospinal tract; magnetic transcranial stimulation; transcranial cortical stimulation; quantification of central motor conduction defects Abbreviations: ADM ϭ abductor digiti minimi; ALS ϭ amyotrophic lateral sclerosis; CMAP ϭ compound muscle action potential (evoked by peripheral stimulation); CMAP Erb ϭ CMAP evoked by Erb's point stimulation; CMAP wrist ϭ CMAP evoked by wrist stimulation; CMCT ϭ central motor conduction time; MEP ϭ motor evoked potential (evoked by transcranial stimulation); MRV ϭ mean rectified voltage (of maximal voluntary isometric EMG activity); TST ϭ triple stimulation technique
Stimulation of motor tracts in motor neuron disease
Journal of Neurology, Neurosurgery & Psychiatry, 1987
The muscle responses evoked by cortical and cervical stimulation in 11 patients with motor neuron disease were studied. The muscle potential in the abductor pollicis brevis, evoked by median nerve stimulation and the somatosensory potential evoked by wrist stimulation were also studied. In eight of 11 patients there was absence or increased central delay of the responses evoked by cortical stimulation. In four patients muscle responses on cervical stimulation and muscle action potentials on median nerve stimulation were also altered, indicating peripheral abnormalities. Somatosensory responses evoked by wrist stimulation were normal. Electrophysiological techniques are helpful in estimating the site of motor involvement in motor neuron disease.
Electroencephalography and clinical neurophysiology, 1988
Motor evoked potentials (MEPs) to transcranial stimulation (TCS) and somatosensory evoked potentials to median nerve stimulation (MN-SEPs) were examined in 74 patients affected by multiple sclerosis (MS = 49 cases), amyotrophic lateral sclerosis (ALS = 9 cases), cervical cord lesions (7 cases), Parkinson's disease (PD = 5 cases), Huntington's chorea (HC = 2 cases), Wilson's disease (WD = 1 case), subacute combined degeneration (SCD = 1 case). MN-SEPs were altered in 38% of arms in MS with a higher incidence in clinically affected than in clinically 'silent' arms (= 77.8% vs. 27.5%). MEP alterations were found in 54% of examined arms, mostly because of a prolongation of the motor CCT. This index was invariably altered in the affected arms, whilst it was involved in 40% of the 'silent' ones. Twelve out of 18 arms displayed abnormal MEPs in ALS. These were mainly due to an absent response, even if moderate motor CCT prolongation and 'giant' MEPs were...
Far-field and cortical somatosensory evoked potentials in motor neuron disease
Muscle & Nerve, 1990
We examined median somatosensory evoked potentials (SEPs) in 26 patients with sporadic motor neuron disease (MND). SEPs were recorded with multiple scalp derivations, using both the midfront and the earlobe as references for each subject. Central conduction time (CCT) was abnormal in three patients, but only when using the midfront reference. Moreover, an exclusive alteration of the early prerolandic potentials (absent or delayed P20 and/or P22) was noted using the earlobe reference in amyotrophic lateral sclerosis and in progressive bulbar palsy (54% and 50% of patients, respectively) but not in progressive muscular atrophy. These findings correlated with clinical evidence of upper motor neuron signs and with the severity of the disease. In agreement with recent views regarding the sources of the early anterior cortical responses, neuronal loss in the motor cortex may be considered as affecting the generator sites of these potentials.
Central motor conduction is abnormal in motor neuron disease
Journal of Neurology, Neurosurgery & Psychiatry, 1987
Conduction in the central motor pathways of the brain and spinal cord was studied in 12 patients with motor neuron disease. Six healthy volunteers served as controls. Transcutaneous electrical stimulation of the cortex, cervical cord, thoracic cord and conus medullaris was used to determine motor latencies to the biceps brachii, thenar eminence and tibialis anterior muscles. Prominent, and often asymmetrical, slowing of central motor conduction was demonstrated in seven of the 12 patients; these findings were most marked in the spinal cord and in most cases correlated with clinical features of corticospinal involvement. In general it was more difficult to excite motor pathways in the central nervous system in the patients with motor neuron disease than in control subjects. Evidence of subclinical involvement of central motor pathways was found in five patients.
Assessment of Motor Evoked Potentials in Multiple Sclerosis
Sensors
Transcranial magnetic stimulation (TMS) is a noninvasive technique mainly used for the assessment of corticospinal tract integrity and excitability of the primary motor cortices. Motor evoked potentials (MEPs) play a pivotal role in TMS studies. TMS clinical guidelines, concerning the use and interpretation of MEPs in diagnosing and monitoring corticospinal tract integrity in people with multiple sclerosis (pwMS), were established almost ten years ago and refer mainly to the use of TMS implementation; this comprises the magnetic stimulator connected to a standard EMG unit, with the positioning of the coil performed by using the external landmarks on the head. The aim of the present work was to conduct a narrative literature review on the MEP assessment and outcome measures in clinical and research settings, assessed by TMS Methodological characteristics of different TMS system implementations (TMS without navigation, line-navigated TMS and e-field-navigated TMS); these were discusse...