Reduced surround inhibition in musicians.

To investigate whether surround inhibition (SI) in the motor system is altered in professional musicians, we performed a transcranial magnetic stimulation (TMS) study in 10 professional musicians and 15 age-matched healthy non-musicians. TMS was set to be triggered by self-initiated flexion of the index finger at different intervals ranging from 3 to 1,000 ms. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of the control TMS at rest and expressed as a percentage. Normalized MEP amplitudes of the abductor digiti minimi (ADM) muscles were compared between the musicians and non-musicians with the primary analysis being the intervals between 3 and 80 ms (during the movement). A mixed-design ANOVA revealed a significant difference in normalized ADM MEPs during the index finger flexion between groups, with less SI in the musicians. This study demonstrated that the functional operation of SI is less strong in musicians than non-musicians, perhaps due to practice of movement synergies involving both muscles. Reduced SI, however, could lead susceptible musicians to be prone to develop task-specific dystonia.

Enhanced spatial discrimination in paretic hands.

OBJECTIVE: Proper interaction between the sensory and motor system is essential for adequate control of voluntary movement. The influence of sensory alteration on motor activity is well known, while the effect of motor disturbance on sensory activity has yet to be clarified. We performed this study to investigate the influence of motor deactivation on sensory discrimination. METHODS: Using Johnson-Van Boven-Phillips domes, we evaluated tactile spatial discrimination (grating orientation threshold; GOT) in 62 patients with acute pure motor stroke and 75 age-matched healthy controls. RESULTS: In controls, the GOT was significantly lower in the dominant than in the non-dominant hands. The GOT was significantly reduced in patients' paretic hand, as compared to their unaffected hand and the hands of healthy controls in both the dominant and non-dominant side. The GOT of patients' paretic hand was significantly and inversely correlated to severity of their initial motor deficit in the non-dominant side (r=0.40, p<0.05), but not in the dominant side. CONCLUSIONS: These results suggest that motor deprivation enhances ascending sensory inputs. SIGNIFICANCE: This study provides additional information about the relationship between the motor and sensory system in humans.

Disturbed surround inhibition in preclinical parkinsonism.

OBJECTIVE: Surround inhibition in the motor system is an essential mechanism for selective execution of desired movements. To evaluate the functional operation of surround inhibition in Parkinson disease, we performed a transcranial magnetic stimulation (TMS) study in the asymptomatic hands of hemiparkinsonism patients. METHODS: TMS was set to be triggered by self-initiated flexion of the index finger at different intervals from 3 to 2000 ms. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of control TMS at rest. Normalized MEP amplitudes of the patients' self-triggered TMS sessions at different intervals were compared to those of the controls. RESULTS: During index finger flexion, MEP amplitudes from the little finger muscle were unchanged in normal subjects. However, they were enhanced in Parkinson patients, despite the absence of any motor disturbance. CONCLUSIONS: These results suggest that the functional operation of surround inhibition is impaired in Parkinson disease. This disturbance may precede motor disturbance in Parkinson disease. SIGNIFICANCE: Impaired surround inhibition can be useful to detect preclinical parkinsonism.

Levodopa-responsive parkinsonism in hereditary spastic paraplegia with thin corpus callosum.

Hereditary spastic paraplegia with thin corpus callosum is a rare degenerative disease, which is characterized by a progressive weakness of the lower limbs with a hypoplastic corpus callosum, and is often associated with other symptoms such as mental impairment, amyotrophy, sensory disturbances, dysuria, nystagmus and cataract. We describe two siblings (brother and sister) who showed a thin corpus callosum on MRI, one of whom showed the pure form of progressive spastic paraplegia, while the other showed predominant levodopa-responsive parkinsonism. The present cases are illustrative of a phenotypic heterogeneity in the same family of spastic paraplegia with a thin corpus callosum, despite the identical neuroimaging findings, and also presented another form of autosomal recessive juvenile levodopa-responsive parkinsonism.

Unilateral periodic limb movement in sleep after supratentorial cerebral infarction.

We report a patient with involuntary right leg movements during sleep, which developed after acute ischemic stroke in the corona radiata. Nocturnal polysomnography confirmed the diagnosis of periodic limb movement in sleep (PLMS). Although the pathogenesis of PLMS is still controversial, it has been proposed that the loss of cortical or subcortical inhibition resulting from the pyramidal tract lesion might cause PLMS. The present case provides evidence to support this hypothesis.

Exercise-induced strengthening of inter-digital connections in musicians.

OBJECTIVE: To investigate whether finger exercise affects surround inhibition in professional musicians as it was previously observed in non-musicians, we performed a transcranial magnetic stimulation (TMS) study in 13 healthy right-handed professional musicians. METHODS: TMS was set to be triggered by self-initiated flexion of the index finger at 3 ms after electromyography onset (self-triggered TMS). Motor evoked potentials (MEPs) of the abductor digiti minimi (ADM) were measured before and at 0, 10, 20 and 30 min after 'single' (little finger abduction) and 'dual' (both index finger flexion and little finger abduction) exercise at 0.5 Hz for 30 min. RESULTS: Control and self-triggered MEPs were not different between the two exercise sessions. MEP enhancements were significantly greater in self-triggered TMS than control TMS after single exercise as well as dual exercise. CONCLUSION: This result demonstrates that MEP enhancement in self-triggered TMS was comparable between two exercise sessions in professional musicians, a result different from that observed in healthy non-musicians. Enhanced self-triggered MEPs after isolated finger exercise suggest that inter-digital cortical connections are strengthened in musicians, presumably due to previous musical training. SIGNIFICANCE: Inter-digital cortical connections are strengthened in musicians and are not differently modulated by different types of short-term finger exercise.

Synchronized finger exercise reduces surround inhibition.

OBJECTIVE: To investigate whether hand muscle repetitive use reduces surround inhibition (SI) as observed in patients with focal hand dystonia, we performed a transcranial magnetic stimulation (TMS) study in 15 healthy right-handed volunteers. METHODS: TMS was set to be triggered by self-initiated flexion of the index finger at 3ms after movement onset. Motor evoked potentials (MEPs) of the abductor digiti minimi (ADM) were measured before and at 0, 10, 20 and 30min after 'single' (little finger abduction) and 'dual' (both index finger flexion and little finger abduction) exercise at 0.5Hz for 30min. SI was calculated as (mean control MEP - mean self-triggered MEP)×100/mean control MEP. RESULTS: Compared to single exercise, dual exercise produced significantly larger and longer-lasting enhancements of self-triggered MEPs, and greater reduction in calculated SIs. CONCLUSIONS: This result demonstrates that synchronized finger exercise can reduce SI between the involved muscles possibly due either to the strengthening of the excitatory connections or to the weakening of the inhibitory connections between them, and may illustrate the association between hand muscle repetitive use and disturbed SI observed in FHD. SIGNIFICANCE: The operation of surround inhibition can be reduced by practicing synchronous movements.

Extended surround inhibition in idiopathic paroxysmal kinesigenic dyskinesia.

OBJECTIVE: Paroxysmal kinesigenic dyskinesia (PKD) is characterized by recurrent attacks of dyskinesia, in which movement of one body part produces involuntary movements of other body parts. Surround inhibition (SI), a mechanism for suppression of unwanted movements, could be deficient in these patients. To test this idea, we performed a transcranial magnetic stimulation (TMS) study in drug-naive patients with PKD. METHODS: TMS was set to be triggered by self-initiated flexion of the index finger at different intervals. Average motor evoked potential (MEP) amplitudes obtained from self-triggered TMS were normalized to average MEPs of the control TMS at rest. Normalized MEP amplitudes of the patients' self-triggered TMS sessions at different intervals were compared to those of the controls. RESULTS: During index finger flexion, MEP amplitudes from the little finger muscle were unchanged in both the patients and normal subjects, however, post-movement MEP enhancement observed in the normal subjects was absent in patients with PKD. These results suggest that the functional operation of SI is itself preserved, but that post-movement excitation of surrounding muscles is deficient in PKD. CONCLUSIONS: This finding may represent that the operation of SI is extended to the post-movement period, perhaps as a compensatory mechanism for preventing unwanted movement in surrounding muscles. SIGNIFICANCE: While many types of impaired inhibition have been described previously in PKD, this is the first possible example of increased inhibition.

Anterior cerebral artery infarction: stroke mechanism and clinical-imaging study in 100 patients.

BACKGROUND: Stroke mechanisms and clinical features of anterior cerebral artery (ACA) territory infarction have rarely been investigated using MRI. OBJECTIVES: To verify stroke mechanisms and to make clinical imaging correlation. METHODS: Clinical, MRI, and angiographic findings of 100 consecutive patients with ACA infarction were studied. RESULTS: Motor dysfunction (n = 91) was the most common symptom, and severe motor dysfunction was related to supplementary motor area/paracentral lobule involvement (p = 0.016). Hypobulia/apathy (n = 43) was related to involvement of frontal pole (p = 0.002), corpus callosum/cingulate gyrus (p = 0.003), and superior frontal gyrus (p < 0.001), and occurred more frequently in patients with bilateral lesions followed by left lesions. Urinary incontinence (n = 30) was not related to any specific lesion locations. Grasp reflex (n = 25) was related to corpus callosum involvement (p = 0.035). Angiographic (mostly MR angiography) results showed that 68 patients had local ACA atherosclerosis, most often at A2 segment. The stroke mechanisms included cardiogenic embolism in 10, internal carotid artery-ACA embolism in 6, and ACA atherosclerosis in 61 patients. In the latter group, detailed stroke mechanisms included local branch occlusion (n = 20), in situ thrombotic occlusion (n = 20), artery-to-artery embolism (n = 12), and a combination (n = 9). Patients with intrinsic ACA disease more often had hypobulia (p = 0.077) and corpus callosal involvement (p = 0.016) than those with embolism either from the internal carotid artery or the heart. CONCLUSION: Anterior cerebral artery (ACA) atherosclerosis is the most important stroke etiology in our population, causing infarction with various mechanisms. Topographic lesion patterns and consequent clinical features of ACA infarction are determined by diverse pathogenic mechanisms and the status of collateral circulation.

Use of the Putamen/Caudate Volume Ratio for Early Differentiation between Parkinsonian Variant of Multiple System Atrophy and Parkinson Disease.

BACKGROUND AND PURPOSE: Neuropathological studies have demonstrated that multiple system atrophy (MSA) produces selective atrophy of the putamen with sparing of the caudate nucleus, while both structures are spared in idiopathic Parkinson's disease (PD). In this study we evaluated the clinical efficacy of using putaminal atrophy in brain MRI to differentiate MSA and PD. METHODS: We measured the putamen/caudate volume ratio on brain MRI in 24 patients with MSA and 21 patients with PD. Two clinicians who were blinded to the patients' diagnoses and to each other's assessments measured the volume ratio using a computer program. RESULTS: The measured volume ratios of the two investigators were highly correlated (r=0.72, p<0.0001). The volume ratio was significantly lower in MSA (1.29+/-0.28) than PD (1.91+/-0.29, p<0.0001). Setting an arbitrary cutoff ratio of 1.6 resulted in about 90% of patients with MSA falling into the group with a lower ratio, whereas more than 80% of patients with PD belonged to the other group. CONCLUSIONS: The present results demonstrate that putaminal atrophy in MSA as measured on brain MRI represents an effective tool for differentiating MSA from PD.

Electromyography patterns of propriospinal myoclonus can be mimicked voluntarily.

In order to investigate the clinical impact of polymyographic evaluation on the diagnosis of propriospinal myoclonus (PSM), we performed electromyography recordings of various truncal muscles in eight healthy volunteers while they mimicked PSM symptoms. Before the experiment, each volunteer learned how to mimic PSM by watching a videotape that showed typical PSM characteristics, i.e., brief symmetric flexion of the trunk. The recorded polymyographic patterns of all volunteers were quite compatible with those found in the previous reports. The present study demonstrates that previously known polymyographic patterns of PSM can be voluntarily mimicked. Additional studies, such as jerk-locked cortical potential, are required to confirm the diagnosis of true PSM.

Dopaminergic influence on disturbed spatial discrimination in Parkinson's disease.

Various sensory symptoms and disturbed sensory perception are often observed in patients with idiopathic Parkinson's disease (PD). The basis of sensory disturbance in PD is unknown but possibly reflects a role for the basal ganglia in sensory processing. To investigate the relationship between the sensory dysfunction and dopaminergic deficiency in PD, we measured spatial discrimination using the Grating Orientation Task in 21 drug-naive patients with PD, before and after long-term antiparkinson therapy, and 25 age-matched healthy controls. The grating orientation threshold was significantly higher in patients (3.03 +/- 0.84) than controls (2.03 +/- 0.79). After 3 to 10 months of antiparkinson therapy, the grating orientation threshold was significantly lowered (2.66 +/- 0.84), although it was still higher than that in controls. Improvement in the patients' sensory function was significantly correlated with motor improvement (r = 0.44). These results suggest that sensory dysfunction in Parkinson's disease is related at least in part to the dopaminergic deficit.

Corticospinal disinhibition during dual action.

When attempting to perform two tasks simultaneously, the human motor as well as the cognitive system shows interference. Such interference often causes altered activation of the cortical area representing each task compared to the single task condition. We investigated changes in corticospinal inhibition during dual action by transcranial magnetic stimulation (TMS). Single-pulse TMS was applied to the left motor cortex, triggered by right leg movement (tibialis anterior muscle) while the right abductor digiti minimi (ADM) muscle was moderately activated (10-20% of the maximal voluntary contraction). The background electromyography (EMG) activity of ADM was measured before and during the leg movement. The silent period (SP) and amplitude of motor evoked potential (MEP) following magnetic stimulation in active ADM were compared for the conditions with and without leg movement. The mean area of the rectified EMG activity of ADM did not alter, while the SP was significantly shortened during leg movement compared to that without leg movement. MEP amplitude was comparable between the two conditions. These results suggest that corticospinal inhibition tested by the SP duration is reduced during the movement of another body part, presumably in order to help maintain muscle force by compensating interference-related alteration in motor cortical activation.

Clinical implication of cerebral artery calcification on brain CT.

BACKGROUND AND PURPOSE: Arterial calcification is a process of atherosclerosis, usually taking place within advanced atheromatous plaque. In the coronary arteries, calcification seen on computed tomography (CT) often indicates severe stenosis, and is noted in almost all patients with coronary symptoms. Calcification of the cerebral arteries is also frequently observed on brain CT, but its clinical significance has yet to be clarified. To evaluate the clinical significance of cerebral arterial calcification on brain CT, we investigated the angiographic and transcranial Doppler ultrasonography (TCD) findings of calcified cerebral arteries. METHODS: The subjects were 57 patients with ischemic stroke, all of whom underwent brain CT, digital subtraction cerebral angiography and TCD. Stroke subtypes were defined according to TOAST classification. Two clinicians who were blinded in respect to the patients' clinical history and to each other's interpretation, determined the presence of cerebral arterial calcification and the degree of angiographic stenosis. RESULTS: Cerebral artery calcification was noted in 23 patients (40%) out of a total of 46 arteries, consisting of 23 internal carotid, 15 vertebral, 5 basilar, 2 middle cerebral and 1 anterior cerebral artery. The patients with calcification were significantly older and more hypertensive than those without calcification. All the patients with calcification showed either large artery atherosclerosis or lacunar stroke. Hemodynamic alterations measured by TCD were rarely observed in calcified arteries. The severity and extent of the atherosclerotic changes were significantly greater in the patients with calcification than those without calcification. CONCLUSION: These results suggest that cerebral arterial calcification does not directly indicate hemodynamically significant atherosclerotic stenosis involving calcified segments, but indicates the underlying etiology of either large artery atherosclerosis or lacunar stroke, and raises the possibility of a diffuse atherosclerotic process being present in the cerebral circulation.