Bilateral Abductor Pollicis Brevis Research Articles

Association of joint hypermobility with range of cervical motion and its impact on the motor unit loss in patients with Hirayama disease.

Some patients with Hirayama disease (HD) may have generalized joint hypermobility (GJH), which may excessively increase cervical range of motion (ROM) and then worsen the HD. The purpose of this study was to identify the frequency of GJH in HD patients and to analyze the effect of GJH on cervical ROM and the severity of HD. The Beighton scoring system (≥4) was used to diagnose GJH in 84 HD patients. All patients underwent assessments of cervical-flexion/extension ROM; motor unit number estimation in bilateral abductor pollicis brevis (APB) muscles; handgrip strength; and the disabilities of the arm, shoulder, and hand assessments. Concomitant GJH was identified in 20 (23.8%) HD patients. The HD patients with GJH exhibited greater cervical-flexion (P < .001) and cervical-extension (P = .033) ROM than those without GJH. Both greater single motor unit potential amplitudes (symptomatic side: P = .005; less-symptomatic side: P = .011) and lower motor unit numbers (symptomatic side: P = .008; less-symptomatic side: P = .013) in bilateral APB, along with lower compound muscle action potential amplitudes on the symptomatic-side APB (P = .039), were observed in patients with GJH than those without GJH. There was a mild negative correlation between motor unit number and cervical-flexion ROM in HD patients (symptomatic side: r = -0.239, P = .028; less-symptomatic side: r = -0.242, P = .027). The frequency of GJH in HD patients may be higher than in the general population. Importantly, GJH may exacerbate excessive cervical-flexion ROM, thereby worsening motor unit loss in HD patients. A cautious approach should be taken when treating HD due to possible comorbid GJH.

Factors Affecting Transcranial Motor-Evoked Potential Measurements Using Single-Train Stimulation with an Increased Number of Pulses during Adolescent Scoliosis Surgery: A Prospective Observational Study.

Measurement of transcranial motor-evoked potentials (TcMEPs) during scoliosis surgery helps detect postoperative new neurological defects. However, TcMEP interpretation is difficult owing to the influence of intraoperative physiological, pharmacological, and time-related factors as well as stimulation conditions. In this study, we aimed to investigate the effect of the abovementioned factors on TcMEP amplitude using single-train stimulation with an increased number of pulses (STS-INP) during adolescent scoliosis surgery; moreover, we evaluated the complications of TcMEP measurement. We included 50 patients and 706 TcMEP measurements. A total of 1412 TcMEP waveforms were analyzed, each on the bilateral abductor pollicis brevis, tibialis anterior, and abductor hallucis muscles. We estimated the mean difference (95% confidence interval (CI)) and predicted mean difference (95% CI) evaluated using the interquartile range of each factor, based on a mixed-effect model with random intercepts for TcMEP amplitude. The predicted mean differences in TcMEP amplitude were clinically small compared with the actual TcMEP amplitude, suggesting that each factor had a limited effect on TcMEP amplitude. No intraoperative bite injuries or seizures were observed. Using STS-INP during adolescent scoliosis surgery may enable accurate measurement of TcMEP amplitude with neither complications nor the influence of various intraoperative factors.

Transcranial electrical stimulation technique for induction of unilateral motor evoked potentials

ObjectiveTranscranial electrical stimulation motor evoked potentials (TES-MEP) are widely used to monitor motor function; however, broad current spread and induced body movement are limitations of this technique. We herein report a localized stimulation technique for TES-MEP that induces unilateral MEP responses. MethodsThe stimulation of C1(+)-C4(-) or C2(+)–C3(-) was performed to induce right- or left-sided muscle contraction, respectively, in 70 patients. Electromyography was recorded by placing electrodes on the bilateral abductor pollicis brevis (APB) and abductor hallucis (AH) muscles. Stimulation conditions were regulated in the range to induce unilateral muscle contractions contralateral to the anodal stimulation. The thresholds and amplitudes of TES-MEP were retrospectively analyzed. ResultsThe thresholds of APB were lower than those of AH in 47 patients, AH thresholds were lower than those of APB in 6 patients, and both APB and AH started to respond at the same intensity in 15 patients. This technical stimulation induced contralateral limb contractions with a suprathreshold stimulation of 129.4 ± 35.6 mA (mean ± standard deviation) in 68 patients (97%). Amplitudes in the suprathreshold stimulation of APB and AH responses were 727.5 ± 695.7 and 403.3 ± 325.7 μV, respectively. ConclusionsThe C1(+)–C4/C2(+)–C3(-) stimulation in TES-MEP enables a localized stimulation to induce unilateral MEP responses. SignificanceOur stimulation technique enables the stable and safe monitoring of unilateral limbs, and contributes to the reliable monitoring of motor function in neurosurgery.

Loss of cervical sagittal alignment worsens the cervical spinal lesions in patients with Hirayama disease.

To quantify the cervical sagittal alignment in patients with Hirayama disease (HD) and to investigate the effect of loss of cervical sagittal alignment upon the cervical spinal lesions in HD. Cervical sagittal alignments were measured in 253 HD patients and 63 healthy subjects by C2-C7 Cobb and a modified method of Toyama et al. Motor unit number estimation (MUNE) was performed in bilateral abductor pollicis brevis (APB) in all HD patients, and 31 patients further underwent cervical diffusion tensor imaging (DTI). Compared with healthy subjects, HD patients showed lower C2-C7 Cobb (P < 0.05), and 83.4% patients showed loss of cervical lordosis (cervical straight or kyphosis), which was greater than healthy subjects (55.6%, P < 0.05). Compared with lordotic/straight group, patients with cervical kyphosis showed lower MUNE values and greater single motor unit potential (SMUP) in bilateral APB, and higher apparent dispersion coefficient (ADC) and lower fractional anisotropy were observed at C4/C5 level in the latter than the former (P < 0.05). C2-C7 Cobb was associated with both C4/C5 ADC and bilateral SMUP (P < 0.05). Most HD patients showed loss of cervical sagittal alignments, and both MUNE and DTI detections demonstrated a positive correlation between loss of cervical sagittal alignments and cervical spinal lesions in HD. These findings supported that loss of cervical sagittal alignments may worsen motor impairments in HD. Therefore, it is necessary for clinicians to be aware of restoring cervical sagittal alignments during HD treatment.

Comparison of the electrophysiological characteristics of tight filum terminale and tethered cord syndrome.

This study aims to characterize tight filum terminale (TFT) in motor evoked potential (MEP) testing by comparing TFT patients with both tethered cord syndrome (TCS) patients and healthy subjects. Fifty TFT patients, 18 TCS patients, and 35 healthy volunteers participated in this study. We recorded MEPs following transcranial magnetic stimulation from the bilateral abductor hallucis muscles as well as compound muscle action potentials and F-waves evoked by electrical stimulation of the tibial nerve from the bilateral abductor pollicis brevis muscles. The peripheral conduction time (PCT) was calculated from the latency of the compound action potential and F-wave. Furthermore, the central motor conduction time (CMCT) was calculated by subtracting PCT from MEP latency. TFT and TCS patients had a significantly longer MEP latency than healthy subjects. PCT in TFT patients was significantly longer than those in TCS patients or healthy subjects. Using the cutoff values for PCT, we were able to diagnose patients with TFT patients with a sensitivity of 72.0% and a specificity of 91.4%. Prolonged PCT in the MEP test may be a useful indicator for TFT and suggests that MEP may be used as an adjunct diagnostic tool for TFT.

Observation on the Effect of Rehabilitative Physical Training on Sports Injuries under Ultrasound Image Examination.

In order to observe the effect of rehabilitative physical training on sports injuries under ultrasound examination, this study firstly carried out experiments, induction and analysis of ultrasound examination, and evaluation-related content, especially the diagnosis of ultrasound examination in muscle and tendon injuries caused by various reasons. And the clinical application of treatment (clinical research) is reviewed, in order to provide reference data for clinical stage summary. Then, by determining the fasciculation and location of the tendon rupture injury by ultrasound, the clinic can decide whether or not to proceed with surgery. Small Achilles tendon tears only require conservative treatment to avoid the development of complete Achilles tendon rupture. Finally, 26 patients and 10 healthy adults were examined by ultrasonography, and each subject was segmented to examine 11 muscles, including the tongue muscle. The bilateral trapezius, bilateral biceps brachii, bilateral abductor pollicis brevis, bilateral quadriceps femoris, and bilateral tibialis anterior muscles were evaluated by ultrasound and statistical methods. The experimental results show that if the fasciculation of the Achilles tendon injury does not reach more than 3/11, it indicates that no surgical treatment is required; for those with a complete tear of the Achilles tendon, the distance between the broken ends should be further measured in the toe flexion state to evaluate whether surgical treatment is required. It effectively solves the problem of visual diagnosis of sports injuries.

Abstract WMP37: Differential Montage Effect On Cortical Excitability In Ischemic Stroke Patients By Single Session Of High Amperage Transcranial Direct Current Stimulation

Background and Objective: We aim to assess the cortical excitability under three montages with single session of transcranial direct current stimulation (tDCS) at 4 mA on ischemic stroke patients. Methods: Adult subjects with first-ever unilateral ischemic stroke ≥6 months and inducible motor evoked potentials (MEP) underwent 3 sessions (washed out ≥2 days apart) of 30 minutes 4 mA tDCS in anodal, cathodal or bihemispheric montage (in pseudorandom order) combined with t upper extremity repetitive task training administered by an Occupational Therapist. We collected MEP responses to transcranial magnetic stimulation (TMS) single pulse, short intracortical inhibition (SICI, 3 ms) and intracortical facilitation (ICF, 15 ms) on bilateral abductor pollicis brevis (APB) muscles at baseline and four post-stimulation timepoints 12 minutes apart. We also monitored safety by recording adverse events, surveying subjects with a questionnaire on tolerability issues and collecting biometric measures (body resistance, skin temperature under the tDCS electrode). Results: Eighteen subjects completed 54 tDCS sessions in total. We observed montage ( P &lt;0.0001) and time ( P &lt;0.01) effects only on the lesioned hemisphere, with bihemispheric tDCS showing relatively higher peak-to-peak MEP. Lack of montage effect in baseline ( P &gt;0.949) suggested sufficient washout interval across the visits. No subjects experienced any adverse events. Biometric measures and tolerability were comparable across the three montages. The most common tolerability issue was transient redness under the tDCS electrodes (70% at anode, 48% at cathode). Conclusions: The bihemispheric montage increased ipsilateral cortical excitability the most in a single session of 4 mA tDCS in chronic ischemic stroke patients. Additionally, a current level of 4 mA is safe and tolerable over multiple sessions.

Low-dose Droperidol Reduces the Amplitude of Transcranial Electrical Motor-evoked Potential: A Randomized, Double-blind, Placebo-controlled Trial.

Low-dose droperidol has been reported to suppress the amplitude of transcranial electrical motor-evoked potentials (TCE-MEPs), but no randomized controlled trials have been conducted to assess this. This randomized, double-blinded, placebo-controlled trial aimed to test the hypothesis that low-dose droperidol reduced TCE-MEP amplitudes. Twenty female patients with adolescent idiopathic scoliosis, aged between 12 and 20 years, and scheduled to undergo corrective surgery were randomly allocated to receive droperidol (20 µg/kg) or 0.9% saline. After recording baseline TCE-MEPs, the test drug was administered, following which TCE-MEP recordings were carried out every 2 minutes for up to 10 minutes. The primary outcome was the minimum relative TCE-MEP amplitude (peak-to-peak amplitude, percentage of baseline value) recorded in the left tibialis anterior muscle. Secondary outcomes included minimum relative MEP amplitudes recorded from all other muscle groups monitored in the study. Data are expressed as medians (interquartile range). The TCE-MEP amplitude of the left tibialis anterior muscle was significantly reduced following droperidol administration compared with saline (37% [30% to 55%] vs. 76% [58% to 93%], respectively, P <0.01). In the other muscles, the amplitudes were reduced in the droperidol group, except for the bilateral abductor pollicis brevis and the left quadriceps femoris muscles. The relative amplitude of the bilateral F waves recorded from the gastrocnemius was decreased in the droperidol group. Low-dose droperidol (20 µg/kg) reduced TCE-MEP amplitudes. Anesthesiologists should pay attention to the timing of droperidol administration during intraoperative TCE-MEP recordings, even if used in a low dose.

Low-dose droperidol suppresses transcranial electrical motor-evoked potential amplitude: a retrospective study.

Low-dose droperidol has been widely used as an antiemetic during and after surgery. Although high-dose droperidol affects motor-evoked potential, the effects of low-dose droperidol on motor-evoked potential amplitude are unclear. The aim of this study was to investigate whether low-dose droperidol affects motor-evoked potential amplitude. We retrospectively reviewed the data of patients who underwent spine surgery under general anesthesia with motor-evoked potential monitoring from February 2016 to 2017. The outcome was the motor-evoked potential amplitude of the bilateral abductor pollicis brevis muscle, tibialis anterior muscle, and abductor hallucis muscle within 1 and 1-2 h after droperidol administration, compared with the baseline motor-evoked potential value. Thirty-four patients were analyzed. The median dose of droperidol was 21 µg/kg. The motor-evoked potential amplitudes of all muscles were significantly reduced after droperidol administration and recovered to baseline values within 2 h. The reduction of all motor-evoked potential amplitudes after droperidol administration was 37-45% of baseline values. There were no significant differences in other drugs administered. There were no serious adverse effects of droperidol administration. Motor-evoked potential amplitude was suppressed by low-dose droperidol. During intraoperative motor-evoked potential monitoring in spine surgery, anesthesiologists should pay careful attention to the timing of administration of droperidol, even at low doses. Based on the results of this study, we are conducting a randomized controlled trial.

Abstract TMP43: Differential Cortical Effect Modulated by Anodal, Cathodal and Bihemispheric Transcranial Direct Current Stimulation (tDCS) in Patients With Ischemic Stroke

Introduction: The differential brain modulatory effects across hemispheres from different montages in stroke patients is not well established. We aimed to investigate the cortical excitability on lesional and contra-lesional hemisphere modulated by anodal, cathodal and bihemispheric montage at 4 mA tDCS strengths. Hypothesis: Bihemispheric tDCS montage induces more cortical excitability on the lesional hemisphere. Methods: Eighteen aging stroke patients with unilateral ischemic stroke of 6 or more months and inducible motor evoked potentials (MEP) underwent 3 sessions of 30 minutes 4 mA tDCS combined with occupational therapy. Each session was at least 2 days apart and consisted of one of the 3 different montages: anodal (Anode: lesional C3/C4, Cathode: non-lesional FP1/FP2), cathodal (Anode: lesional FP1/FP2, Cathode: non-lesional C3/C4), or bihemispheric (Anode: lesional C3/C4, Cathode: non-lesional C3/C4). We collected MEP size, short intracortical inhibition (SICI, 3 ms) and intracortical facilitation (ICF, 15 ms) on bilateral abductor pollicis brevis (APB) muscles using single or paired pulse TMS at 5 timepoints (baseline and four post-tDCS 12 minutes apart sessions). Results: All 18 subjects had comparable resting motor threshold (rMT) across 3 montages (see A). Bihemispheric tDCS montage offered significantly larger peak-to-peak MEP responses on the lesioned cortex (ANOVA, F=8.97, P&lt;0.01) but not on the non-lesioned cortex (ANOVA, F=0.86, P=0.42). These differences were apparent in single pulse, SICI and ICF (see B). Conclusion: Our findings support that bihemispheric montage is better suited in post-stroke motor recovery tDCS applications.

Median neuropathy at the wrist in patients with systemic sclerosis: two-year follow-up study.

ObjectivesTo determine the incidence and factors associated with median neuropathy at the wrist (MNW) in systemic sclerosis (SSc) patients using an electrodiagnostic (EDX) study.Material and methodsSSc patients who attended the scleroderma clinic, Srinagarind Hospital, were prospectively evaluated by questionnaire, physical examination, and EDX study. The questionnaire consisted of the baseline characteristics, type of scleroderma, clinical signs and symptoms associated with scleroderma, and the Boston questionnaire. The physical examinations were the Modified Rodnan Skin Score, motor power grading of bilateral abductor pollicis brevis muscle, and pinprick sensation of median nerve distribution of both hands. Moreover, the EDX study, which was composed of median and ulnar sensory and motor nerve conduction studies of both hands and electromyography of the abductor pollicis brevis muscles, was evaluated at baseline and following two years.ResultsOut of 75 systemic sclerosis patients, 50 individuals participated in the study. Diffuse cutaneous type of SSc is the most common type (72%). The common SSc associated symptoms were Raynaud phenomenon, skin tightness and hand deformity. Incidence of MNW was 90 cases per 1000 person-years. Following a two-year interval, the percentages of mild, moderate and severe MNW were 28%, 22% and 6% respectively. Most of those with MNW were still particularly asymptomatic in a mild degree. Moreover, 12 out of 50 patients (24%) had a worse EDX result. There was no statistically significant association between MNW occurrence and studied factors.ConclusionsMNW commonly has high incidence in SSc patients. Therefore, SSc patients should be followed up in both clinical and EDX studies for MNW screening. SSc patients with asymptomatic MNW might need clinical follow-up for early diagnosis.

Post-tetanic transcranial motor evoked potentials augment the amplitude of compound muscle action potentials recorded from innervated and non-innervated muscles

Background ContextTranscranial electrical stimulation used to produce motor evoked potentials (TES-MEPs) and subsequent compound muscle action potential (CMAP) recording is widely used to monitor motor function during surgery when there is risk of damaging the spinal cord. Nonetheless, some muscles do not produce CMAP amplitudes sufficient for intraoperative monitoring. PurposeThis study aimed to investigate the utility of tetanic stimulation at single and multiple peripheral nerve sites for augmenting CMAP amplitudes recorded from innervated and non-innervated muscles. Study Design/SettingA retrospective study was carried out. Patient SampleThe study sample comprised 24 patients with cervical myelopathy who underwent decompression surgery at our department between November 2005 and March 2007. Outcome MeasuresCompound muscle action potential amplitude was a physiological measure. MethodsWe used two patterns of tetanic peripheral nerve stimulation for each patient. The first pattern consisted of tetanic stimulation of the left tibial nerve only (Pattern 1), and the second pattern consisted of tetanic stimulation of the bilateral median nerves and left tibial nerve (Pattern 2). ResultsCompound muscle action potential amplitudes from all muscles were augmented by both tetanic stimulation patterns compared with conventional TES-MEP recording; however, Pattern 2 elicited the greatest augmentation of CMAP amplitudes, especially for CMAPs recorded from the bilateral abductor pollicis brevis muscles. ConclusionsAlthough tetanic stimulation of a single peripheral nerve increased CMAP amplitudes recorded from both innervated and non-innervated muscles, CMAP amplitudes were best augmented when the corresponding nerve received tetanic stimulation. Additionally, tetanic stimulation of multiple nerves rather than a single nerve appears to provide better augmentation.

Compound Muscle Action Potential Decrement to Repetitive Nerve Stimulation Between Hirayama Disease and Amyotrophic Lateral Sclerosis

To compare repetitive nerve stimulation (RNS) between Hirayama disease (HD) and amyotrophic lateral sclerosis (ALS). The 3-Hz RNS test was performed on bilateral abductor pollicis brevis, abductor digiti minimi, middle deltoid, and upper trapezius muscles in 33 HD patients and 37 ALS patients. In HD patients, none of tested muscles showed any abnormal decrements (≥10%). Significant decrements were observed in 73% of the ALS patients, and decrements were more frequently observed in proximal muscles (deltoid: 70.3%; trapezius: 48.6%). Illness duration did not correlate with decrement percentage in either patient group, and there was no relationship between decrement incidence and ALS diagnostic category (P > 0.05). The significantly different RNS results between ALS and HD patients support the application of RNS, especially performing RNS in proximal muscles, as a supplementary test in distinguishing these two diseases, even in the early stages. These results may also imply a difference in underlying pathophysiology between ALS and HD.

Comparison of a special designed high intensity coil to a standard round coil-TMS-setting

BackgroundRoutine diagnostic Transcranial Magnetic Stimulation (TMS) is performed with a round coil (RC) for cranial and spinal root stimulation, being less successful for motor evoked potentials (MEP) of lower limb muscles. MEP elicited with a special configured flat figure-of-eight coil designed for high intensity stimulation (HI-coil) were compared to RC with regard to handling, efficiency, and physiological properties of MEP. New methodsMEP elicited with HI-coil and 9-cm diameter RC for cortical, spinal and peripheral stimulation (PES) were compared for Motor threshold (MT), latencies and amplitudes of bilateral Abductor pollicis brevis (APB) and Abductor hallucis muscles (AH). Results and comparison with existing methodsMT for HI-coil were significantly lower for cortical and spinal root stimulation compared to RC (APB: 37% vs. 48%; AH: 58% vs. 72%). MEP-latencies elicited with HI-coil and RC were without significant difference. AH-MEP amplitudes were significantly larger for HI-coil cortical (705±980μV vs. 370±280μV) and root stimulation (260±210μV vs. 151±100μV). Amplitudes elicited by PES compared to HI-coil were always significantly larger. ConclusionResults for cortical and spinal root stimulation with regards to latencies and amplitudes for APB were equivalent between HI-coil and RC. PES was superior in achieving supramaximal stimulation in terms of amplitudes. The use of the HI-coil might be advantageous for MEP of lower extremity muscles with emphasis on pathologic conditions requiring higher stimulation intensities.

Cortical Motor Circuits after Piano Training in Adulthood: Neurophysiologic Evidence.

The neuronal mechanisms involved in brain plasticity after skilled motor learning are not completely understood. We aimed to study the short-term effects of keyboard training in music-naive subjects on the motor/premotor cortex activity and interhemispheric interactions, using electroencephalography and transcranial magnetic stimulation (TMS). Twelve subjects (experimental group) underwent, before and after a two week-piano training: (1) hand-motor function tests: Jamar, grip and nine-hole peg tests; (2) electroencephalography, evaluating the mu rhythm task-related desynchronization (TRD) during keyboard performance; and (3) TMS, targeting bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM), to obtain duration and area of ipsilateral silent period (ISP) during simultaneous tonic contraction of APB and ADM. Data were compared with 13 controls who underwent twice these measurements, in a two-week interval, without undergoing piano training. Every subject in the experimental group improved keyboard performance and left-hand nine-hole peg test scores. Pre-training, ISP durations were asymmetrical, left being longer than right. Post-training, right ISPAPB increased, leading to symmetrical ISPAPB. Mu TRD during motor performance became more focal and had a lesser amplitude than in pre-training, due to decreased activity over ventral premotor cortices. No such changes were evidenced in controls. We demonstrated that a 10-day piano-training was associated with balanced interhemispheric interactions both at rest and during motor activation. Piano training, in a short timeframe, may reshape local and inter-hemispheric motor cortical circuits.

101. Functional changes of cortical motor circuits after piano training in adults: TMS and EEG evidence

We aimed to study short-term effects of keyboard training in music-naive subjects on motor cortex activity and interhemispheric interactions, using electroencephalography and transcranial magnetic stimulation (TMS). Twelve subjects underwent, before and after a two week-piano training: (1) hand-motor function tests: Jamar, grip and nine-hole peg tests (NHPT); (2) electroencephalography, evaluating the mu rhythm task-related desynchronization (TRD) during keyboard performance, and (3) TMS, targeting bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM), to obtain duration and area of ipsilateral silent periods (ISP). We included ten controls who also underwent these measurements twice, without training. Trained subjects improved keyboard performance and left-hand NHPT scores. Pre-training, ISP durations were asymmetrical (left ISP > right ISP). Post-training, right ISP APB increased, leading to symmetrical ISP APB . Mu TRD during bimanual performance also became symmetric, more focal and with a lower amplitude than in pre-training, owing to decreased activity over the ventral premotor cortices. These bilateral modifications correlated with keyboard performance and NHPT scores. No performance or neurohysiological changes were evidenced in controls. A 10-day piano-training was associated with rebalanced interhemispheric interactions both at rest and during motor activation. Piano training, in a short timeframe, may reshape local and inter-hemispheric motor cortical circuits.

ID 261 – Motor cortex plasticity after short-term piano training in adults

To study short-term effects of keyboard training in music-naive subjects on motor cortex activity and interhemispheric interactions, using electroencephalography and transcranial magnetic stimulation (TMS). Twelve subjects underwent, before and after a two week-piano training: (1) hand-motor function tests: Jamar, grip and nine-hole peg tests (NHPT); (2) electroencephalography, evaluating the mu rhythm task-related desynchronization (TRD) during keyboard performance, and (3) TMS, targeting bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM), to obtain duration and area of ipsilateral silent periods (ISP). We included ten controls who also underwent these measurements twice, without training. Trained subjects improved keyboard performance and left-hand NHPT scores. Pre-training, ISP durations were asymmetrical (left ISP > right ISP). Post-training, right ISPAPB increased, leading to symmetric ISPAPB. Mu TRD during bimanual performance also became symmetric, more focal and of lower amplitude than in pre-training, owing to decreased activity over ventral premotor cortices. These bilateral modifications correlated with keyboard performance and NHPT scores. No performance or neurohysiological changes were evidenced in controls. A 10-day piano-training was associated with rebalanced interhemispheric interactions both at rest and during motor activation. Piano training, in a short timeframe, may reshape local and inter-hemispheric motor cortical circuits.

ID 21 – Riche–Cannieu anastomosis: A case report

Riche–Cannieu anastomosis (RCA) is a rare type of anomalous innervation. It is characterized as innervation of medial and lateral part of palm involving the deep branch of the ulnar nerve crossover to the recurrent branch of the median nerve in the hand. A 44 years old woman who has numbness and pain her hands evaluated by nerve conduction studies and needle electromyography. In neurological examination, there was no wasting or weakness of the hand muscles, nor sensory impairment. Nerve conduction studies showed dual innervation (mainly ulnar nerve) of abductor pollicis brevis muscle bilaterally. Median nerve motor conduction studies recorded from APB muscles obtained by stimulating the nerve at the wrist and elbow showed responses with very low amplitude bilaterally. Needle electromyography of bilateral abductor pollicis brevis and abductor digiti minimi muscles are found as normal. Ulnar to median anastomosis in the palm should be kept in mind in patient with unexpected electrophysiological results. If the hand muscles are clinically intact but electrophysiological examination shows a severe median nerve lesion, RCA should be suspected.

114. Physiological aging is associated with reorganization of map motor cortical representation and interhemispheric interactions: A TMS mapping study

Several functional studies suggest a more bilateral movement-related recruitment of motor areas during voluntary movement associated with physiological aging. To investigate the changes of motor cortical excitatory and inhibitory balance during physiological aging, using transcranial magnetic stimulation (TMS). We recruited right-handed 31 healthy volunteers, divided into two groups: one younger group (15 subjects, 6 females, age 25.4 ± 1.9 y) and one older group (16 subjects, 7 females, age 61.1 ± 5.1 y). Motor abilities were tested using Nine Hole Peg Test (NHPT) and finger tapping (FT). Surface electromyography (EMG) of the bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM) muscles was recorded. TMS was delivered with a Magstim 200 simulator connected to a figure-of-eight coil (Magstim 2nd generation, 70 mm of external diameter). Resting motor threshold (RMT) on each side and cortical mapping of APB and ADM muscles were analyzed. We also registered ipsilateral silent period (ISP) in both APB muscles, during maximal contraction. Older subjects showed worse motor performances (in terms of NHPT and FT of both hands) than younger ones ( p p p = 0.03). In older group, APB map on the right hemisphere was significantly reduced vs the younger group ( p = 0.021) and vs its homologous ( p = 0.042). For ADM, no significant map differences were found between elderly and young subjects, even on the right hemisphere. ISP was significantly reduced in the elderly on both sides, in terms of duration ( p = 0.025), peak ( p = 0.033) and area ( p = 0.008). Physiological aging is associated with disruption of interemispheric specialization both concerning motor cortical representation and interhemispheric interactions. This may have consequences on recovery from pathological processes and suggests that age has to be taken into account when planning therapeutic intervention aimed at restoring hand motor function.

Age-related changes in motor cortical representation and interhemispheric interactions: a transcranial magnetic stimulation study.

To better understand the physiological mechanisms responsible for the differential motor cortex functioning in aging, we used transcranial magnetic stimulation to investigate interhemispheric interactions and cortical representation of hand muscles in the early phase of physiological aging, correlating these data with participants’ motor abilities. Right-handed healthy subjects were divided into a younger group (n = 15, mean age 25.4 ± 1.9 years old) and an older group (n = 16, mean age 61.1 ± 5.1 years old). Activity of the bilateral abductor pollicis brevis (APB) and abductor digiti minimi (ADM) was recorded. Ipsilateral silent period (ISP) was measured in both APBs. Cortical maps of APB and ADM were measured bilaterally. Mirror movements (MM) were recorded during thumb abductions. Motor abilities were tested using Nine Hole Peg Test, finger tapping, and grip strength. ISP was reduced in the older group on both sides, in terms of duration (p = 0.025), onset (p = 0.029), and area (p = 0.008). Resting motor threshold did not differ between groups. APB and ADM maps were symmetrical in the younger group, but were reduced on the right compared to the left hemisphere in the older group (p = 0.008). The APB map of the right hemisphere was reduced in the older group compared to the younger (p = 0.021). Older subjects showed higher frequency of MM and worse motor abilities (p < 0.001). The reduction of right ISP area correlated significantly with the worsening of motor performances. Our results showed decreased interhemispheric interactions in the early processes of physiological aging and decreased cortical muscles representation over the non-dominant hemisphere. The decreased ISP and increased frequency of MM suggest a reduction of transcallosal inhibition. These data demonstrate that early processes of normal aging are marked by a dissociation of motor cortices, characterized, at least, by a decline of the non-dominant hemisphere, reinforcing the hypothesis of the right hemi-aging model.