Lateral spread response elicited by double stimulation in patients with hemifacial spasm

In patients with hemifacial spasm (HFS), a lateral spread response (or abnormal muscle response) is recorded from facial muscles after facial nerve stimulation. The origin of this response is not completely understood. We studied the lateral spread responses elicited by double stimulation in 12 patients with HFS during microvascular decompression. The response was recorded from the mentalis muscle by electrical stimulation of the temporal branch of the facial nerve or from the orbicularis oculi muscles by stimulation of the marginal mandibular branch. The interstimulus intervals (ISIs) of double stimulation ranged from 0.5 to 7.0 ms. R1 was defined as the response elicited by the first stimulus, and R2 as the response elicited by the second stimulus. R1 had a constant latency and amplitude regardless of the ISI, whereas R2 appeared after a fixed refractory period without facilitation or depression in a recovery curve of latency and amplitude. From these findings, we consider that the lateral spread response is due to cross-transmission of facial nerve fibers at the site of vascular compression rather than arising from facial nerve motor neurons.     

Altered response to repetitive transcranial magnetic stimulation in patients with chronic primary insomnia

BackgroundWe aimed at evaluating the amplitude changes of the motor evoked potentials (MEPs) induced by of low-frequency (LF) repetitive transcranial magnetic stimulation (rTMS) over the primary motor cortex (M1) in10 patients with primary insomnia (PI) and in 10 age-matched healthy controls.MethodsMedian peak-to-peak MEP amplitudes were assessed in all subjects at three times: at baseline (T₀), after the first train of a single rTMS session (T₁), and after the whole rTMS procedure (T₂). This consists of 20 trains of 1 Hz stimulation with 50 stimuli per train and an intertrain interval of 30 s.ResultsResting motor threshold (RMT) and MEPs amplitude did not differ between the two groups at T₀. A reduction of MEP size was observed at both T₁ and T₂ in all subjects, but this was significantly less pronounced in patients than in control subjects.ConclusionsThe lack of MEP inhibition reflects an altered response to LF rTMS in patients with PI. These rTMS findings are indicative of an altered cortical plasticity in inhibitory circuits within M1 in PI. Subjects with PI exhibited an impairment of the LTD-like mechanisms induced by inhibitory rTMS, thus providing further support to the involvement of GABA neurotransmission in the pathophysiology of PI.     

Corticospinal direct response to transcranial magnetic stimulation in humans

The corticospinal motor evoked potential (MEP) response to transcranial magnetic stimulation of the motor cortex was investigated in comparison with the direct (D) response to electrical stimulation of the exposed motor cortex from the spinal epidural space in 7 neurologically normal patients during brain tumor surgery. The D response during operation was obtained by transcranial magnetic stimulation of the scalp over the areas of the cerebral motor cortex, the hand or arm areas. The magnetic induced D response showed a conduction velocity of 50.5–72.7 m/sec and was resistant to anesthesia and unaffected by muscle relaxants and tolerant to high frequency (500 Hz) paired magnetic stimulus, and the latencies of magnetic MEPs corresponded to those with direct electrical stimulation. Thus, recording of the D response by transcranial magnetic stimulation are useful for not only identifying the location of the motor cortex during intracranial surgery but also for non-invasive recording of pyramidal tract activity during extracranial surgery under general anesthesia.     

Electroencephalographic connectivity predicts clinical response to repetitive transcranial magnetic stimulation in patients with insomnia disorder

BackgroundAccumulating evidence suggests that low frequency repetitive transcranial magnetic stimulation (rTMS), which generally decreases cortical excitability and remodels plastic connectivity, improves sleep quality in patients with insomnia disorder. However, the effects of rTMS vary substantially across individuals and treatment is sometimes unsatisfactory, calling for biomarkers for predicting clinical outcomes.ObjectiveThis study aimed to investigate whether functional connectivity of the target network in electroencephalography is associated with the clinical response to low frequency rTMS in patients with insomnia disorder.MethodsTwenty-five patients with insomnia disorder were subjected to 10 sessions of treatment with 1 Hz rTMS over the right dorsolateral prefrontal cortex. Resting-state electroencephalography was collected before rTMS. Pittsburgh Sleep Quality Index, Hamilton Depression Rating Scale, Hamilton Anxiety Rating Scale, and Mini-Mental State Exam were performed before and after rTMS treatment, with a follow-up after one month. Electroencephalographic connectivity was measured by the power envelope connectivity at the source level. Partial least squares regression identified models of connectivity that maximally accounted for the rTMS response.ResultsScores of Pittsburgh Sleep Quality Index, Hamilton Depression Rating Scale, and Hamilton Anxiety Rating Scale were decreased after rTMS and one-month later. Baseline weaker connectivity of a network in the beta and alpha bands between a brain region approximating the stimulated right dorsolateral prefrontal cortex and areas located in the frontal, insular, and limbic cortices was associated with a greater change in Pittsburgh Sleep Quality Index and Hamilton Depression Rating Scale following rTMS.ConclusionsLow frequency rTMS could improve sleep quality and depressive moods in patients with insomnia disorder. Moreover, electroencephalographic functional connectivity would potentially be a robust biomarker for predicting the therapeutic effects.     

Taste sense in patients with hemifacial spasm

In the cerebellopontine angle cistern, the nervus intermedius (NI) runs close to the motor division of the facial nerve (FN). A vascular loop compressing the FN in patients with hemifacial spasm (HFS) can thus also affect the NI. However, to our knowledge, taste has not been investigated in patients with HFS. In this pilot study, we assessed the sense of taste quantitatively in 10 female patients with HFS using filter paper strips impregnated with four taste qualities (sweet, sour, salty, and bitter) at four concentrations. The taste score did not differ between the ipsilateral and contralateral sides. The taste score for salty on the ipsilateral side increased with disease duration. Our findings suggest that a vascular loop compressing the FN does not affect the function of the NI. Further studies with greater numbers of patients are needed to confirm our results.     

Tremor in hemifacial spasm patients

Tremor often accompanies dystonia and some other movement disorders. There are no reports describing tremor in patients with hemifacial spasm (HFS). The aim of the study was to assess the occurrence, type and parameters of tremor in HFS patients. The study included 47 HFS patients (mean age: 58.6 ± 10.7-years-old) and 48 healthy volunteers matched by sex and age. Tremor was assessed clinically and objectively using a triaxial accelerometer and EMG. A load test with 500 g weight was performed in order to identify physiological tremor. The Clinical Global Impression-Severity scale (CGI-S) was used to assess the severity of HFS. Neurological examination revealed tremor in 19 patients and 5 control subjects, and the objective methods postural and kinetic hand tremor was confirmed. Among the patients we identified: one case of psychogenic tremor, two patients were diagnosed with essential tremor, six patients had essential tremor in one hand and enhanced physiologic tremor in the other, seven patients had essential tremor in both hands and three patients had physiological tremor in both hands. Five control subjects revealed enhanced the physiological tremor type. The occurrence of hand tremor was associated with higher severity of HFS, as assessed by CGI score. Tremor accompanies HFS in 40% of cases and 10% of control subjects. The aetiology of hand tremor in patients with HFS is unknown. However, it may be associated with compression of the tremor oscillator located in the medulla.     

Worry facilitates corticospinal motor response to transcranial magnetic stimulation

Like other forms of emotion, anxiety has been theoretically linked to preparation for action. Worry is a type of anticipatory anxiety and the hallmark of generalized anxiety disorder. Research has shown that worry is associated with vigilance to threat cues and increased muscle tension, which may in part be explained by motor facilitation that accompanies preparation for action. This study assessed corticospinal motor responses during worry using transcranial magnetic stimulation (TMS). Participants received TMS during a worry induction, during motor imagery, and during mental arithmetic, while electromyography and force were measured. TMS over the primary motor cortex elicited larger corticospinal motor responses during worry than mental arithmetic and smaller responses than motor imagery of maximum voluntary contraction of targeted muscles. These findings suggest that the association between worry and motor preparation cannot be explained by high cognitive load and provide further support for theoretical accounts emphasizing the role of action preparation in anxiety.     

Sternocleidomastoid muscle responses to transcranial magnetic stimulation in patients with cervical dystonia

Ten cervical dystonia (CD) patients, with involuntary head rotation to one side and contralateral sternocleidomastoid muscle (SCM) hypertrophy, were investigated with transcranial magnetic stimulation, and the results were compared to those of 10 healthy subjects. Monopolar needle electrodes with isolated shafts were used for bilateral electromyographic recordings in the SCMs of the motor evoked potentials (MEPs) elicited by the magnetic stimulator. The latencies of ipsilateral SCM MEPs were shorter in the CD patients than in the control subjects (P<0.001). The latencies of SCM activity suppression by TMS were longer in the CD patients than in the control group when stimuli were given on the contralateral side (P<0.05). Both the clinically dystonic and the contralateral SCM of the CD patients exhibited significantly abnormal latencies of the ipsilateral SCM MEPs (P<0.01) and of the SCM suppression (P<0.05). Three CD patients also had consistent activity in the SCM counteracting the direction of head rotation during the suppression experiments. The latencies of the suppression of this abnormal activation were shorter (P<0.05), than the latencies of the suppression in the SCM during normal voluntary activation by these CD patients (i.e. rotation of the head in the contrary direction). The results suggest bilaterally enhanced motoneuronal excitability and disturbed inhibitory regulation in patients with CD.     

Ventrolateral medullary compression in hypertensive patients with hemifacial spasm

In a patient-controlled study, the authors demonstrated a significantly higher prevalence of rostral ventrolateral medulla (VLM) compression in hypertensive patients with hemifacial spasm (HFS) compared with age-, sex-, race-, disease duration-, and disease severity-matched normotensive patients with HFS (p = 0.02). Hypertensive HFS patients were more likely to have a greater severity of neurovascular compression at the VLM compared with normotensive HFS patients (p = 0.008). VLM compression is associated with risk of hypertension in this study population.     

Resting motor threshold changes and clinical response to prefrontal repetitive transcranial magnetic stimulation in depressed patients

Aims: Several variables are able to influence the antidepressant effects of repetitive transcranial magnetic stimulation (rTMS), particularly the intensity of stimulation, which is generally expressed according to the resting motor threshold (RMT). The aim of our study was to investigate whether or not RMT changes during the treatment of resistant depression by rTMS and whether these fluctuations could alter treatment outcome. Methods: Seventy‐five inpatients suffering from unipolar or bipolar treatment‐resistant depression and who had been antidepressant‐free or taking a stable antidepressant drug and a daily dose of benzodiazepine for at least a month received a left prefrontal rTMS session once a day for 10 days at 10 Hz and 95% RMT. Results: For the whole group, no significant fluctuation of RMT was observed between the first and the second week of rTMS treatment. However, RMT increased, decreased or remained constant throughout treatment depending on the patient. These RMT changes influenced the outcome of the 10 sessions concerning the severity of depressive and anxiety symptoms, measured by the Beck Depression Inventory and State Trait Anxiety, respectively. Conclusions: Our results justify calculating RMT regularly, and suggest that its variations play a role in treatment outcome.     

Repetitive transcranial magnetic stimulation reveals abnormal plastic response to premotor cortex stimulation in schizophrenia.

BACKGROUND: Schizophrenia may be characterized by abnormal plastic modulation in cortical neuronal circuits. Activation of premotor cortex using repetitive transcranial magnetic stimulation (rTMS) produces suppression of cortical excitability in primary motor cortex. We hypothesized that premotor rTMS would cause less suppression of motor cortical excitability in patients with schizophrenia than in control subjects. METHODS: Twelve patients diagnosed with schizophrenia and twelve healthy control subjects underwent subthreshold rTMS to the premotor area in a 15-min conditioning train. Measurements of primary motor cortical excitability (motor evoked potential; MEP), the resting motor threshold (RMT), and cortical inhibition (CI) were taken before and after the rTMS. RESULTS: There was no difference in RMT between groups at baseline, although the patient group had less CI than the control group at baseline. Following rTMS, the change in both MEP size and RMT between groups was significant. After rTMS, MEP size was suppressed in the control group and increased in the patient group, whereas RMT increased in the normal control group and decreased in the patient group. CONCLUSIONS: Patients with schizophrenia demonstrate abnormal brain responses to rTMS applied to the premotor cortex that appear to relate to reduced motor cortical inhibition.     

Clinical applications of transcranial magnetic stimulation in patients with movement disorders

Transcranial magnetic stimulation (TMS) is a method of non-invasive brain stimulation that affects the cerebral cortex but not deep structures. In patients with movement disorders the most common application of TMS has been to test the excitability of connections within and among motor areas of the cortex, which has provided useful information on pathophysiology; however, inter-individual variability in the responses has resulted in difficulties in translating this method into a clinically applicable diagnostic use. Repeated stimulation (eg, 1 Hz for 20 min) can result in long-term plastic changes in the motor system, which has led to increased interest in possible therapeutic applications. In this Review, we describe the theoretical background to TMS techniques and discuss the uses of TMS as a potential diagnostic tool in movement disorders. The difficulties in bringing the technique into regular clinical diagnostic practice will be discussed and the evidence for the potential of repetitive TMS as a therapeutic tool in patients with movement disorders will be reviewed.     

侧方扩散反应监测在面肌痉挛微血管减压术中的应用

目的 探讨侧方扩散反应（LSR）监测在面肌痉挛（HFS）微血管减压术（MVD）中的应用价值。方法 回顾性分析2016年6月至2018年8月MVD治疗的70例HFS的临床资料,术中均监测LSR。术后1周、1年根据Cohen分级评估术后疗效,0级为治愈。结果 70例均监测到LSR,其中LSR消失65例（消失组）,确认充分减压后LSR仍持续存在5例（未消失组）。术后1周,消失组治愈率[92.3%（60/65）]明显高于未消失组[40.0%（2/5）;P<0.05]。术后1年,消失组治愈[96.9%（63/65）与未消失组[80.0%（4/5）]无统计学差异（P>0.05）。结论 MVD治疗HFS,术中监测LSR可以帮助确定责任血管,尽可能减少责任血管的遗漏;术中LSR消失提示近期疗效较好,但对长期疗效的预测价值有限。     

88例面肌痉挛显微血管减压术临床研究

目的探讨微血管减压术治疗面肌痉挛的临床疗效。方法 2017年12月至2018年11月期间本院神经外科收治的面肌痉挛患者88例,均采用微血管减压术治疗,术中采用脑干听觉诱发电位监测。术后随访1年,统计临床疗效及不良反应发生情况。结果 88例患者中,49例(56.0%)即刻治愈;32例(36.0%)延迟愈合;4例(5%)未愈;3例(3%)复发;本组总有效率为92.05%(81/88)。术后并发症发生率为11.36%(10/88)。结论微血管减压术治疗面肌痉挛的临床疗效确切。术中应注意小脑保护、责任血管的成功判断、减压材料的大小与放置方式,同时严密缝合硬膜。