Positive Repetitive Nerve Stimulation Research Articles

Ocular Myasthenia gravis: determining the predictive factors of secondary generalisation.

Myasthenia gravis (MG) can be classified according to clinical features into ocular MG (OMG) and generalised MG (GMG). However, OMG carries the risk of conversion to GMG. In this study, we aimed to determine the predictive factors for the secondary generalisation of OMG patients. OMG patients followed-up in our hospital from January 1999 to November 2023 were retrospectively reviewed. Demographic and clinical characteristics data were collected from medical records. OMG patients with follow-up of < 2 years were excluded. Of the 122 patients included, 87 (71.3%) remained as OMG and 35 (28.7%) had converted to GMG. The median time taken for generalisation was 12 months (IQR 6-30). 73.5% of patients had converted to GMG within 2 years. In univariate analysis, a significantly higher proportion of patients with positive anti-AChR antibodies (94.1% vs. 67.1%, p = 0.002), higher antibody titre (8.0 vs. 1.6 nmol/L, p < 0.001), positive repetitive nerve stimulation (RNS) (54.5% vs. 15.9%, p < 0.001), positive single-fibre electromyography (96.7% vs. 76.0%, p = 0.013) and the presence of thymic abnormalities (35.3% vs. 3.5%, p < 0.001), specifically thymoma (29.4% vs. 1.2%, p < 0.001) were associated with secondary generalisation. Conversely, higher percentage of patients who were treated with corticosteroid remained as OMG (37.9% vs. 17.1%, p = 0.026). However, in multivariate analysis, only positive anti-AChR antibodies (ORadj 9.6, 95% CI 1.7-56.1), positive RNS (ORadj 4.0, 95% CI 1.3-12.5) and the presence of thymoma (ORadj 29.5, 95% CI 2.5-351.1) were independently associated with secondary generalisation. The presence of anti-AChR antibodies and thymoma with positive RNS were the predictive factors of secondary generalisation in OMG.

Analysis of the characteristics of patients with amyotrophic lateral sclerosis with neuromuscular junction dysfunction prior to motor neuron degeneration

Objective: To investigate the clinical and electrophysiological characteristics of patients with amyotrophic lateral sclerosis (ALS) with positive repetitive nerve stimulation (RNS) test results on the accessory nerve and negative needle electromyography (EMG) test results on the sternocleidomastoid with the goal to enrich the knowledge of disease progression in patients with ALS. Methods: The clinical data of 612 patients diagnosed with ALS at the Neurology Department of the First Medical Center, Chinese PLA General Hospital from June 2016 to August 2022 were collected. In total, 267 cases had undergone EMG tests on the sternocleidomastoid following a positive 3 Hz RNS test result on the accessory nerve, who were selected as the study subjects. The differences in clinical indicators were compared between RNS (+)/EMG (-) group and RNS (+)/EMG (+) group. A binomial distribution model with multiple variables was built to quantitatively analyze the major factors and their effects. Results: At the initial visit, 15.8% of patients with ALS were 3 Hz RNS (+) on the accessory nerve and EMG (-) on the ipsilateral sternocleidomastoid, accounting for 36.3% of RNS (+) patients. The decremental range of the 3 Hz RNS test delivered to the accessory nerve in these patients [-14% (-19%, -12%)] was lower than that in patients with RNS (+)/EMG (+) [-17% (-23%, -13%)] (P<0.05), while the ratio of upper limb onset (64.9%) and non-definite diagnosis (28.9%) were higher [54.7% and 13.5% for patients with RNS (+)/EMG (+), P<0.05]. Furthermore, the Revised Amyotrophic Lateral Sclerosis Functional Rating Scale (ALSFRS-R) score [40 (37, 42)], body mass index (BMI) [23.8 (22.0, 25.4) kg/m2] and forced vital capacity (FVC) [92.8% (76.6%, 103.8%)] were higher in patients with RNS(+)/EMG(+) (P<0.05). The multivariate model suggested that, in patients with RNS (+)/EMG (-), the ratio of upper limb onset to lower limb onset was 1.04, while that of upper limb onset to bulbar onset was 2.02, and that of lower limb onset to bulbar onset was 1.94. The ratio of non-definite ALS to definite ALS was 1.13. The ALSFRS-R score, BMI, and FVC had a protective contribution to the electrophysiological function of the motor neurons. The ratio of the effect size of the ALSFRS-R or BMI to that of FVC was 3.37 and 1.14, respectively. Conclusions: Patients with ALS that were 3 Hz RNS (+) on the accessory nerve and EMG (-) on the ipsilateral sternocleidomastoid had a smaller decremental range of the compound muscle action potential amplitude, and a higher proportion of upper limb onset and non-definite ALS. A higher ALSFRS-R score, BMI, and FVC have a protective effect to the electrophysiological function of motor neurons. The effect size of the ALSFRS-R score is the largest, followed by BMI and FVC.

Utility of Repetitive Nerve Stimulation in the Diagnosis of Myasthenia Gravis in the Inpatient Setting.

Sensitivity and specificity of Repetitive Nerve Stimulation (RNS) is typically reported from outpatient centers, and we hypothesized that these values might not apply to hospitalized patients with higher grades of weakness. RNS may be helpful in rapidly confirming diagnosis of myasthenia gravis (MG) in the inpatient setting, as results from confirmatory antibody testing are often delayed. We sought to characterize the sensitivity and specificity of RNS in the inpatient setting to assist in the early diagnosis of MG. We performed a retrospective analysis of all adult patients who had inpatient RNS at our center from 2016 to 2021. Inclusion criteria included RNS performed at least at one site and a neurological evaluation which prompted an electrodiagnostic study to evaluate for neuromuscular junction (NMJ) pathology. Descriptive statistics and Fisher exact analysis were performed. Of the 32 identified hospitalized patients, 6 had greater than 10% decrement on slow RNS, confirming NMJ dysfunction. Five were diagnosed with MG, and 1 with Lambert-Eaton myasthenic syndrome. Of the 26 patients with normal RNS, 25 ultimately had alternative causes of weakness. One was later diagnosed as seronegative MG based on clinical improvement with acetylcholinesterase inhibitors. In our inpatient population, the overall sensitivity and specificity of RNS were 83.3% and 96.2% respectively. There was a statistically significant association between a positive RNS and diagnosis of MG (P = .0002). RNS is a highly sensitive and specific test for the diagnosis of MG in an inpatient setting, and these results are likely more rapidly available compared to antibody testing.

Myasthenia gravis coexisting with HINT1-related motor axonal neuropathy without neuromyotonia: a case report

BackgroundHINT1 mutations cause an autosomal recessive axonal neuropathy with neuromyotonia. This is a first case report of coexistence of myasthenia gravis (MG) and HINT1-related motor axonal neuropathy without neuromyotonia.Case presentationA 32-year-old woman presented with recurrent ptosis for 8 years, diplopia for 2 years and limb weakness for 1 year and a half. Neostigmine test, elevated AChR antibody level and positive repetitive nerve stimulation supported the diagnosis of MG. Electroneurography (ENG) and electromyography (EMG) examinations revealed a motor axonal neuropathy without neuromyotonic or myokymic discharges. Next-generation sequencing and Sanger sequencing were performed to identify the gene responsible for suspected hereditary neuropathy. Genetic testing for a HINT1 mutation was performed and revealed a homozygous mutation at c.278G>T (p. G93V). The patient was treated with pyridostigmine, oral prednisolone and azathioprine. Her ptosis and diplopia have significantly improved at 6-month follow-up.ConclusionsConcurrence of MG and hereditary motor axonal neuropathy without neuromyotonia is quite rare. Detection of ptosis with or without ophthalmoplegia, distribution of limb weakness, and reflex can help in recognizing the combination of MG and peripheral neuropathy. Early diagnosis is important for initial treatment and prognosis. The novel homozygous variant c.278G>T(p.G93V) contributes to the pathogenic variants spectrum of the HINT1 gene.

Lack of Immunotherapy as the Only Predictor of Secondary Generalization in Very-Late-Onset Myasthenia Gravis With Pure Ocular Onset.

During the past two decades, an increasing number of patients with very-late-onset myasthenia gravis (v-LOMG) with an onset age of 65 years or older have been identified. However, few studies explore the predictors of secondary generalization in patients with v-LOMG with pure ocular onset. In this retrospective cohort study, 69 patients with v-LOMG were divided into ocular MG (OMG) and generalized MG (GMG), and the clinical characteristics and outcomes were compared. Cox regression analysis was performed to explore the predictors of generalization. The average onset age of the study population was 73.1 ± 4.2 years and the median disease duration was 48.0 months (interquartile range, 32.5–64.5 months). Serum acetylcholine receptor (AChR) antibody was detected in up to 86% of patients and concomitant diseases in approximately half of the patients. Male predominance was seen in OMG group while female predominance in GMG group (p = 0.043). Patients with OMG showed a lower positive rate of repetitive nerve stimulation (RNS) than those with GMG (p = 0.014), and favorable outcomes were obtained in more patients with OMG than those with GMG (p < 0.001). Of the 51 patients with pure ocular onset, 25 (49.0%) underwent secondary generalization. A higher probability of generalization was found in patients with positive RNS results and without immunotherapy (p = 0.018 and <0.001). Upon Cox regression analysis, immunotherapy was negatively associated with secondary generalization [HR (hazard ratio) 0.077, 95%CI [0.024–0.247], p < 0.001]. Altogether, compared to the patients with very-late-onset GMG, the counterparts with OMG exhibit a significantly higher female predominance and a lower positive rate of RNS tests, especially on facial and accessory nerves. Lack of immunotherapy is the only predictor of secondary generalization in those with pure ocular onset.

Characteristics of low frequency repetitive nerve stimulation in patients with myasthenia gravis and its correlation with clinical features

Objective: To investigate the characteristics of low frequency repetitive nerve stimulation (RNS) in patients with myasthenia gravis (MG) and analyze the correlation between RNS results and clinical characteristics. Methods: The clinical and electrophysiological data of 107 MG patients who were admitted to Guangdong Provincial People's Hospital and underwent electromyography (EMG) between September 2015 to September 2020 were retrospectively reviewed. The characteristics of low frequency RNS in ocular MG and generalized MG patients were analyzed. Patients were divided into RNS-negative group and RNS-positive group according to the RNS results. The clinical features, serological and thymic CT findings, thymic pathology were collected and compared. Binary logistic regression analysis was used to analyze the related factors of low frequency RNS. Results: Generalized MG (73.0%, 46/63) showed a lower positive rate of low frequency RNS compared to ocular MG (34.1%, 15/44) (P<0.001). In generalized MG, the positive rate of low frequency RNS in accessory nerve (68.3%, 43 cases) and facial nerve (52.4%, 33 cases) was higher than that in ulnar nerve (14.3%, 9 cases) (P<0.001). The decrease rate of compound muscle action potential (CMAP) in facial nerve (32%±11%) was higher than that in ocular muscle type (22%±7%) in RNS-positive group (P=0.011). Patients with positive facial nerve RNS were more likely to involve the throat muscles than those with negative result [22 cases (52.4%) compared with 17 cases (26.2%), P=0.006]. RNS-positive group showed a significantly higher quantitative myasthenia gravis (QMG) score than that of negative group (P<0.001). In ocular MG, patients with positive RNS showed a later onset (P=0.021), higher acetylcholine receptor (AChR) antibody-positive rate (P=0.03) and QMG score (P<0.001). Additionally, In generalized MG, patients with positive RNS showed a significantly higher AChR antibody-positive rate (P=0.023) and QMG score (P<0.001). The logistic regression analysis showed that QMG score [OR(95%CI)=1.66(1.36-2.03), P<0.001] and positive AChR antibody [OR(95%CI)=5.45(1.28-23.14), P=0.022] were independently related to abnormal RNS. Conclusions: Low frequency RNS is more sensitive in generalized MG. The stimulation of facial and accessory nerves increases the positive rate of RNS in MG patients. Abnormal results of low frequency RNS tend to be combined with positive AChR antibody and higher QMG score, reflecting the severity of muscle weakness. Therefore, serological examination and early intervention are required for those with abnormal RNS.

Neuromuscular Junction Disorders (NMJ) O-NJ001. Electrodiagnostics profile in Myasthenia gravis

Introduction . Repetitive Nerve Stimulation (RNS) has a sensitivity of 50-80% in predicting Myasthenia Gravis (MG). This wide range is affected by type and severity of MG, muscle tested, frequency of stimulation and exercise. There has been a previous study describing these factors but did not confirmed it with the result of Single Fiber (SF) and Acetylcholine Receptor antibody (AChR). Methods . This was a cross-sectional study. Data was from RNS results of MG patients in Electromyography laboratories, Cipto Mangunkusumo National Hospital January to December 2019. Muscle tested on RNS were abductor digiti minimi (ADM) muscle, trapezius (Tr) muscle and orbicularis occuli (OrbOc) muscle. Slow RNS used 3, 5, 7 and 10 Hz stimulation followed by 3 Hz stimulation immediate, 1 minute (min) and 2 min post exercise. Decrease of Compound Muscles Action Potential (CMAP) amplitude > 10% is considered as positive RNS. Results . As much as 47 patients were included in this study. The average age of patients is 43 years old. As much as 44.7% had a positive RNS test, and 70% of the case was positive from OrbOc, followed by Tr (60%) and ADM (30%). Frequency of stimulation that obtained the positivity the most is at 5 Hz, and the 4th wave revealed the lowest point of decreament, followed by the 5th wave. Single Fiber was positive in 57.4% of the case, and AChR was positive in 51.1%. There are 11 patients (23.4%) that has a mismatch results between SF and AChR. Conclusion . RNS without confirmation of SF and AChR may yield a false negative result. Orbicularis Oculi shows the most sensitive muscle tested in RNS, with stimulation of 5 Hz and the 4th waveform the lowest decrement. SF and AChR are still important in confirming strong suspicion patients with MG despite negative results in RNS.

P-PN018. The co-occurrence of myasthenia gravis and Guillain-Barré Syndrome: A case report

Introduction . Myasthenia gravis (MG) is an autoimmune disease of neuromuscular junction with a prevalence of approximately 20 per 100,000 in the US and between 15 and 179 per million worldwide. Guillain-Barre Syndrome (GBS) is an autoimmune-related disease leading to generalized paralysis, characterized by acute severe ascending weakness. The co- occurrence of myasthenia gravis (MG) is uncommon with a few reported cases in the literature. Case report: A 34-year-old male with history of bilateral ophthalmoplegia, bilateral ptosis, areflexia and lower motor neuron tetraparesis. The symptoms seemed to be fluctuating in the early phase and progressive within 3 weeks. Patient was diagnosed with myasthenia gravis. The Acetylcholine Receptor Antibody (AChR) was positive. The Pyridostigmine therapy was administered but did not improve the symptoms fully. The repetitive nerve stimulation was positive and nerve conduction study showed axonal degeneration. Cerebrospinal fluid (CSF) analysis showed cytoalbuminergic dissociation. The patient was diagnosed with GBS Miller Fisher variant. The clinical symptoms improved after being administered with intravenous immunoglobulin (IVIg) therapy. A month later, the patient readmitted with worsening symptoms that was triggered by respiratory tract infection. These symptoms improved after administration of pyridostigmine, intravenous corticosteroid, and intravenous antibiotic. Results . This patient admitted to our hospital with symptoms fit with relapsing myasthenia gravis, and the course of the disease was also fit with Miller Fisher variant of Guillain Barre Syndrome. In this case, the MG diagnosis was confirmed with the presence of AChR antibody and positive repetitive nerve stimulation test. While, GBS diagnosis was supported by the CSF analysis profile, and nerve conduction study results. Conclusion . Although extremely rare, MG and GBS may present in the same patient with various characteristics. This case is unique and rarely occur, additional research needs to be conducted to understand the mechanism.

Prediction of generalization of ocular myasthenia gravis under immunosuppressive therapy in Northwest China

BackgroundIt is well demonstrated that immunosuppressants can reduce, but not eliminate the risk of generalized development in ocular myasthenia gravis (OMG). In this study, we aimed to explore the predictive factors of generalized conversion of OMG patients who received immunosuppressive treatments.MethodsOMG patients under immunosuppressive treatments in Tangdu Hospital from June 2008 to June 2012 were retrospectively reviewed. Baseline clinical characteristics were documented. Patients were followed up regularly by face-to-face interview and the main outcome measure was generalized conversion. The logistic regression analysis was performed to determine the predictive factors of generalization of OMG.ResultsTwo hundred twenty-three eligible OMG patients completed the final follow-up visit and 38 (17.0%) progressed to generalized MG (GMG) at a median time to generalization of 0.9 year. Patients with adult onset and positive repetitive nerve stimulation (RNS) of facial or axillary nerve had higher conversion rate than those with juvenile onset and negative RNS (p = 0.001; p = 0.019; p = 0.015, respectively). Adult-onset patients converted earlier than juvenile-onset OMG patients (p = 0.014). Upon multivariate logistic regression analysis, age of onset (Odds ratio [OR] 1.023, 95% confidence interval [CI] 1.006–1.041, p = 0.007) and positive facial nerve RNS (OR 2.826, 95%CI 1.045–5.460, p = 0.038) were found to be positively associated with generalized development. Moreover, an obviously negative association was found for disease duration (OR 0.603, 95%CI 0.365–0.850, p = 0.019).ConclusionsAge of onset, disease duration and facial nerve RNS test can predict generalized conversion of OMG under immunosuppressive therapy. Adult-onset, shorter disease duration and facial nerve RNS-positive OMG patients have a higher risk of generalized development.

P89-F Neurophysiological findings in 11 cases of dropped head syndrome

Background Dropped head syndrome (DHS) is a rare disorder characterized by weakness of the cervical paraspinal muscles with inability to extend the neck. It can be a part of several generalized neuromuscular processes or secondary to local conditions. Also, a restricted myopathy, “isolated neck extensor myopathy” (INEM), has been described. Material and methods 11 cases of DHS were referred to our Neurophysiology department in the period 2015–2018 for evaluation, with suspected neuromuscular etiology. ENG/EMG, repetitive nerve stimulation, sfEMG or all of them were performed according to the clinical suspicion and findings. Results In 4 patients, neurophysiological studies were compatible with neuromuscular junction disorder (one of them with overlapping myopathic features): findings showed clearly positive repetitive nerve stimulation in facial and spinal nerves. sfEMG mean consecutive difference (MCD) was above 80 μs, with some blocking, in these cases. In 6 patients, EMG proved myopathic changes: mild spontaneous activity in all of them (positive waves, mainly), and short, small motor unit action potentials in 5. Of particular interest, in the myopathic group, sfEMG showed increased jitter in few pairs of fiber, but normal mean jitter and without blocking. In 2 cases, the evaluation could not be concluded. The final diagnosis in 4 cases was myasthenia gravis, and myopathy in 7 (inflammatory myopathy or isolated neck extensor myopathy). All patients improved with specific treatment. Conclusions In our series, miastenia gravis and myopathy (INEM or inflammatory) were the main etiologies. Neurophysiological studies revealed distinctive features in both groups, with high diagnostic yield.

Study on variation trend of repetitive nerve stimulation waveform in amyotrophic lateral sclerosis.

Background:Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease involving both upper and lower motor neurons with no effective cure. Electrophysiological studies have found decremental responses during low-frequency repetitive nerve stimulation (RNS) except for diffused neurogenic activities. However, the difference between ALS and generalized myasthenia gravis (GMG) in terms of waveform features is unclear. In the current study, we explored the variation trend of the amplitudes curve between ALS and GMG with low-frequency, positive RNS, and the possible mechanism is discussed preliminarily.Methods:A total of 85 ALS patients and 41 GMG patients were recruited. All patients were from Peking Union Medical College Hospital (PUMCH) between July 1, 2012 and February 28, 2015. RNS study included ulnar nerve, accessory nerve and facial nerve at 3 Hz and 5 Hz stimulation. The percentage reduction in the amplitude of the fourth or fifth wave from the first wave was calculated and compared with the normal values of our hospital. A 15% decrease in amplitude is defined as a decrease in amplitude.Results:The decremental response at low-frequency RNS showed the abnormal rate of RNS decline was 54.1% (46/85) in the ALS group, and the results of different nerves were 54.1% (46/85) of the accessory nerve, 8.2% (7/85) of the ulnar nerve and 0% (0/85) of the facial nerve stimulation, respectively. In the GMG group, the abnormal rate of RNS decline was 100% (41/41) at low-frequency RNS of accessory nerves. However, there was a significant difference between the 2 groups in the amplitude after the sixth wave.Conclusions:Both groups of patients are able to show a decreasing amplitude of low-frequency stimulation RNS, but the recovery trend after the sixth wave has significant variation. It implies the different pathogenesis of NMJ dysfunction of these 2 diseases.

Myasthenia gravis as one of paraneoplastic neurological syndromes associated with small cell lung cancer. Case report

Myasthenia gravis associated with extrathymic malignancies is a rarely diagnosed pathology in clinical practice. We report a case of myasthenia gravis-like syndrome associated with small cell lung cancer. A male patient has been diagnosed with 3 different paraneoplastic neurological syndromes: sensorimotor polyneuropathy, limbic encephalitis and myasthenia gravis-like syndrome which was confirmed by positive repetitive nerve stimulation test. The causal association between small cell lung cancer and myasthenia gravis as a paraneoplastic neurological syndrome (PNS) has not been officially confirmed yet. However, there is increasing evidence in the literature, that myasthenia gravis could be one of the PNS phenotypes of non-thymomatous malignancies.

Low conversion rate of ocular to generalized myasthenia gravis in Singapore.

Ocular myasthenia gravis (OMG) is a common condition of the neuromuscular junction that may convert to generalized myasthenia gravis (GMG). Our aim in this study was to determine the conversion rate and predictive factors for generalization in OMG, in an Asian population. The investigation consisted of a retrospective study of OMG patients with a minimum 2 years of follow-up. Among 191 patients with OMG, 155 had the minimum 2-year follow-up. The conversion rate at median follow-up (40.8 months) was 10.6% (95% confidence interval 7.9%-13.3%), and at the 2-year follow-up it was 7.7% (95% confidence interval 5.6%-9.8%). At baseline, the predictive factors for generalization were positive acetylcholine receptor antibodies (hazard ratio 3.71, P = 0.024), positive repetitive nerve stimulation (RNS) studies (hazard ratio 4.42, P = 0.003), and presence of radiologically presumed or pathologically confirmed thymoma (hazard ratio 3.10, P = 0.013). The conversion rate of OMG to GMG in Asian patients is low, as predicted by presence of acetylcholine receptor antibodies, presence of thymoma, and positive RNS studies. Muscle Nerve 57: 756-760, 2018.

Myasthenia gravis complicated with polymyositis: a report of three cases and literature review

Three female patients admitted with elevated creatine kinase, impaired muscle on electromyogram, and positive repetitive nerve stimulation and neostigmine tests were diagnosed as polymyositis (PM) with myasthenia gravis (MG). Twenty five more cases were retrieved by literature search, and the clinical data of total 28 cases were analyzed. There were 10 males and 18 females with an average age of 56 years. The clinical manifestations include dyspnea(43%), dysphagia(43%), ptosis(43%), dysarthria(29%), diplopia(18%), cough after drinking(14%), myalgia(11%). Thirteen out of 26 cases (50%) had positive results in repetitive nerve stimulation (RNS) and 10/11 showed positive reaction in neostigmine test. Serum positive anti-acetylcholine receptor was detected in 21 out 23 patients (91%). Key words: Polymyositis; Myasthenia Gravis

Myasthenia gravis as a presenting feature in a patient with SCLC: A case report

Small cell lung cancer (SCLC) is the most frequent cancer histology associated with paraneoplastic syndromes. These syndromes are typically caused by ectopic hormone production or immune-mediated tissue destruction caused by neural antigen expression from cancer cells. Lambert-Eaton myasthenic syndrome is well known to be a classical paraneoplastic syndrome of small cell lung carcinoma (SCLC).Only a few cases of myasthenia gravis (MG) and SCLC were previously reported. The causal association between lung cancer and non-thymomatous myasthenia gravis has not been clarified yet. To date, there has been no evidence supporting the speculation that association of myasthenia gravis with lung cancer might be one of the phenotypes of paraneoplastic syndrome. We present a case of a 47-year-old male ex-smoker with SCLC associated with myasthenia gravis evidenced by the clinical findings of ptosis, dysphagia, proximal weakness, and positive repetitive nerve stimulation (RNS) test.&#x0D; Bangladesh Journal of Neuroscience 2015; Vol. 31 (1): 50-55

56.: Phenotypic variation in Miller Fisher syndrome

This study aims to describe the diverse clinical presentations associated with anti-GQ1b antibody positivity. We report four patients with Miller Fisher Syndrome (MFS) admitted over a period of 3 months to a single tertiary hospital in Sydney, NSW, Australia. Only one patient presented with the classical clinical triad of ataxia, areflexia and ophthalmoplegia. The three other patients presented with a range of signs including blepharoptosis, pseudo-internuclear opthalmoplegia and pseudo-proptosis. Two patients had positive repetitive nerve stimulation and were mistaken for ocular myasthenia gravis. All patients had strongly positive immunoglobulin G anti-GQ1b antibodies detected. While the diversity of clinical presentations delayed formal diagnosis, treatment with intravenous immunoglobulin therapy prompted a complete recovery in all patients. Our patients highlight the spectrum of clinical features associated with GQ1b antibodies. While the classic triad of acute ophthalmoplegia, ataxia, and areflexia is a highly recognisable clinical entity, anti-GQ1b antibody-related disease should also be suspected in patients with limited or atypical forms of Miller Fisher syndrome.

Predictive Value of Electrophysiology for Presence of Thymic Pathology in Myasthenia Gravis

Single fibre electromyography (SFEMG) and repetitive nerve stimulation (RNS) are routinely performed investigations in evaluation of patients with myasthenia gravis (MG). Significant number of MG patients have a thymic pathology. We aimed to explore the relationship between the SFEMG and RNS findings with the presence of thymic pathology. We studied 159 consecutive patients with MG over a 10 year period. The SFEMG parameters - mean jitter (MJ) and percentage of abnormal fibres (POAF) and the RNS result were correlated with the thymic findings. As compared to patients with normal thymus (MJ:58.3 μsec; POAF:63.5%), patients with thymic pathology had a significantly higher MJ (80.9 μsec; p &lt; 0.0005) and POAF (83.5%; p &lt; 0.0005). MG patients with thymic hyperplasia had the highest MJ (87.6 μsec) and POAF (84.4%) followed by patients with thymoma (MJ:78.6 μsec; POAF:83.2%). The MJ and POAF did not correlate with the stage of thymoma. Mean jitter values above 34.9 μsec and POAF above 31% had 100% sensitivity for the presence of thymic pathology. A positive RNS increased the risk of thymic pathology (OR = 3.9, CI = 1.8-8.5) and thymoma. (OR = 3.5; CI = 1.5-8.1). Electrophysiology could be valuable complimentary tool to identify MG patients at high risk for thymic pathology. However, it does not aid us to identify the exact thymic pathology and does not correlate with the stage of thymoma. All OMG patients with higher MJ and PAOF values should also be screened for thymoma. The results reinforce the immunological role of thymic pathology in neuromuscular transmission interference.

Repetitive hypoglossal nerve stimulation in myasthenia gravis.

To assess the diagnostic efficacy of repetitive nerve stimulation (RNS) of the hypoglossal nerve in patients with myasthenia gravis (MG) and bulbar symptoms (dysphagia, dysarthria). Twenty patients with MG and 25 normal controls had RNS of the hypoglossal nerve. All patients also had single fibre electromyography (SFEMG) of the orbicularis oculi and RNS with recordings of the nasalis, trapezius and abductor pollicis brevis muscles. All patients had positive SFEMG studies. Nine patients with bulbar symptoms had positive hypoglossal RNS, including 3 with negative RNS recordings in other muscles. Eleven patients with no bulbar symptoms showed negative hypoglossal RNS, including two with positive RNS recordings from other muscles. Abnormal RNS of the hypoglossal nerve correlates well with bulbar dysfunction and further characterises the extent of neuromuscular transmission defect in MG patients.

Masseteric repetitive nerve stimulation in the diagnosis of myasthenia gravis

Objective: (1) to develop a method for masseteric repetitive nerve stimulation (RNS) and to obtain normative data for amplitude and area decrement of the muscle (M) response. (2) To investigate myasthenia gravis (MG) patients with masseteric RNS. Masticatory muscles are frequently affected in MG, but no RNS test is available to investigate this district. Methods: Fifteen healthy subjects and 17 MG patients were examined. The masseteric nerve was stimulated by a monopolar needle (cathode), inserted between the mandibular incisure and the zygomatic arch, and a surface electrode (anode), on the contralateral cheek. Masseteric M response was recorded using surface electrodes on the muscle belly and below the mandibular angle. Stimuli were delivered at 3 Hz in trains of 9, at rest and after isometric effort. Results: Normal subjects: mean amplitude decrement was 0.3±1.2% at rest, and 1.9±1.3% after isometric effort. Patients: 15 patients (88%) were positive on masseteric RNS; in 3 of these it was the only positive RNS test. The extent of decrement observed in masseter muscle was significantly greater than in trapezius muscle. Conclusions: Masseteric RNS is a simple and well-tolerated procedure; it offers a new possibility in testing the cranial muscles in disorders of neuromuscular transmission.