Drenthen, J.

The CMAP scan as a tool to monitor disease progression in ALS and PMA (Article)

2013-04-01T00:00:00Z

Amyotrophic lateral sclerosis (ALS) and progressive muscular atrophy (PMA) are characterized by a loss of motor units (MUs), reinnervation and, eventually, muscle fibre loss. These three aspects are all reflected in the compound muscle action potential scan (CMAP scan, a high-detail stimulus response curve), which visualizes large MU potentials as 'steps'. We explored changes in the CMAP scan over time, combined the information on steps and CMAP amplitude into a CMAP scan-based progression score (CSPS), and correlated this score with motor unit number estimates (MUNE). Ten patients (three PMA, seven ALS; age 37-77 years) were included. CMAP scan and MUNE measurements were performed five times during a three-month period. Nine patients had additional measurements. The follow-up period was 3-24 months. Results demonstrated that abnormalities in steps preceded a decline in maximum CMAP amplitude during follow-up. Usually, both steps and maximum CMAP amplitude changed between recordings. The correlation between the CSPS and MUNE was-0.80 (p < 0.01). In conclusion, the CMAP scan can be used to visualize and quantify disease progression in a muscle affected by MND. The CSPS is a measure of MU loss that is quick and easy to obtain and that, in contrast to MUNE, has no sample bias.

Multiplet discharges after electrical stimulation: New evidence for distal excitability changes in motor neuron disease (Article)

2012-10-01T00:00:00Z

We hypothesized that action potentials evoked by distal stimulation might trigger ectopic activity (multiplet discharges, MDs). By studying MDs, we investigated the involvement of the axonal part of the peripheral motor neuron in amyotrophic lateral sclerosis (ALS) and progressive muscular atrophy (PMA). We performed stimulated high-density surface EMG recordings of the thenar muscles in 10 ALS/PMA patients, five recordings per patient over a three-month period. Furthermore, motor unit number estimates (MUNE) and ALSFRS-R scores were obtained in sessions 1 and 5. MDs were found in all patients, in 21% of the sampled motor units, and in response to 2.4% of the stimulations. The interspike interval range of the MD components was 2.9-6.5 ms, which is compatible only with a distal MD origin. The number of MDs, as percentage of the number of applied stimuli, was correlated with a decline in ALSFRS-R (r = 0.80, p = 0.006) and MUNE (r = 0.72, p = 0.02). In conclusion, MDs can be elicited with electrical stimulation in ALS and PMA patients. Analysis of MD characteristics provides further indications for pathophysiological excitability changes in the most distal part of the motor neuron. MDs are associated with clinical deterioration.

Guillain-Barré syndrome subtypes related to Campylobacter infection (Article)

2011-03-01T00:00:00Z

Background: In Guillain-Barré syndrome (GBS), the diversity in electrophysiological subtypes is unexplained but may be determined by geographical factors and preceding infections. Acute motor axonal neuropathy (AMAN) is a frequent GBS variant in Japan and one study proposed that in Japan, Campylobacter jejuni infections exclusively elicit AMAN. In The Netherlands C jejuni is the predominant type of preceding infection yet AMAN is rare. This may indicate that not all Dutch GBS patients with C jejuni infections have AMAN. Objective: To determine if GBS patients with a preceding C jejuni infection in The Netherlands exclusively have AMAN. Methods: Retrospective analysis of preceding infections in relation to serial electrophysiology and clinical data from 123 GBS patients. C jejuni related cases were defined as having preceding diarrhoea and positive C jejuni serology. Electrophysiological characteristics in C jejuni related cases were compared with those in viral related GBS patients. In addition, eight GBS patients from another cohort with positive stool cultures for C jejuni were analysed. Results: 17 (14%) of 123 patients had C jejuni related GBS. C jejuni patients had lower motor and higher sensory action potentials compared with viral related cases. Nine (53%) C jejuni patients had either AMAN or inexcitable nerves. However, three (18%) patients fulfilled the criteria for acute inflammatory demyelinating polyneuropathy (AIDP). Also, two (25%) of eight additional patients with a C jejuni positive stool sample had AIDP. Conclusion: In The Netherlands, C jejuni infections are strongly, but not exclusively, associated with axonal GBS. Some patients with these infections fulfil current criteria for demyelination.

Guillain-Barré syndrome subtypes related to Campylobacter infection (Research Paper)

2011-01-01T00:00:00Z

Pain in Guillain-Barré syndrome: A long-term follow-up study (Article)

2010-10-19T00:00:00Z

Background: Pain in Guillain-Barré syndrome (GBS) may be pronounced and is often overlooked. Objectives: To obtain detailed information about pain in GBS and its clinical variants. Methods: This was a prospective cohort study in 156 patients with GBS (including 18 patients with Miller Fisher syndrome [MFS]). We assessed the location, type, and intensity of pain using questionnaires at standard time points during a 1-year follow-up. Pain data were compared to other clinical features and serology. Results: Pain was reported in the 2 weeks preceding weakness in 36% of patients, 66% reported pain in the acute phase (first 3 weeks after inclusion), and 38% reported pain after 1 year. In the majority of patients, the intensity of pain was moderate to severe. Longitudinal analysis showed high mean pain intensity scores during the entire follow-up. Pain occurred in the whole spectrum of GBS. The mean pain intensity was predominantly high in patients with GBS (non-MFS), patients with sensory disturbances, and severely affected patients. Only during later stages of disease, severity of weakness and disability were significantly correlated with intensity of pain. Conclusions: Pain is a common and often severe symptom in the whole spectrum of GBS (including MFS, mildly affected, and pure motor patients). As it frequently occurs as the first symptom, but may even last for at least 1 year, pain in GBS requires full attention. It is likely that sensory nerve fiber involvement results in more severe pain. Copyright

Size does matter: The influence of motor unit potential size on statistical motor unit number estimates in healthy subjects (Article)

2010-10-01T00:00:00Z

Objective: The statistical method of motor unit number estimation (MUNE) assumes that all motor unit potentials (MUPs) have the same size. The present study aims to evaluate the consequences of this assumption as well as its implications for the validity of statistical MUNEs. Methods: We performed statistical and multiple point stimulation (MPS) MUNE with an array of 120 electrodes on the thenar muscles of 15 healthy subjects. These recordings allow isolation and quantification of the effect of non-uniform MUP size on MUNE, because the differences in submaximal CMAP size (and, hence, in MUNE) between electrodes are due almost entirely to differences in (summed) MUP size. Results: We found no correlation between statistical and MPS MUNEs. Statistical MUNEs proved very sensitive to small variations in the "bandwidth" (variance) of the response series; MUNEs from electrodes only 8 mm apart could deviate by as much as 60%. This variation in bandwidth resulted from spatial (and, hence, size) differences between the contributing MUPs. Conclusions: Statistical MUNEs are very sensitive to violation of the uniform MUP-size assumption, to an extent that blurs any correlation with MPS MUNE in healthy subjects. Significance: Statistical MUNE cannot be used to detect mild to moderate motor unit losses.

Prediction of respiratory insufficiency in Guillain-Barré syndrome (Article)

2010-06-01T00:00:00Z

Objective: Respiratory insufficiency is a frequent and serious complication of the Guillain-Barré syndrome (GBS). We aimed to develop a simple but accurate model to predict the chance of respiratory insufficiency in the acute stage of the disease based on clinical characteristics available at hospital admission. Methods: Mechanical ventilation (MV) in the first week of admission was used as an indicator of acute stage respiratory insufficiency. Prospectively collected data from a derivation cohort of 397 GBS patients were used to identify predictors of MV. A multivariate logistic regression model was validated in a separate cohort of 191 GBS patients. Model performance criteria comprised discrimination (area under receiver operating curve [AUC]) and calibration (graphically). A scoring system for clinical practice was constructed from the regression coefficients of the model in the combined cohorts. Results: In the derivation cohort, 22% needed MV in the first week of admission. Days between onset of weakness and admission, Medical Research Council sum score, and presence of facial and/or bulbar weakness were the main predictors of MV. The prognostic model had a good discriminative ability (AUC, 0.84). In the validation cohort, 14% needed MV in the first week of admission, and both calibration and discriminative ability of the model were good (AUC, 0.82). The scoring system ranged from 0 to 7, with corresponding chances of respiratory insufficiency from 1 to 91%. Interpretation: This model accurately predicts development of respiratory insufficiency within 1 week in patients with GBS, using clinical characteristics available at admission. After further validation, the model may assist in clinical decision making, for example, on patient transfer to an intensive care unit.

Reproducibility of the CMAP scan (Article)

2010-01-01T00:00:00Z

Introduction: The CMAP scan is a surface EMG method based on the successive activation of motor units. It provides information about reinnervation processes, the number of functional motor units and nerve excitability. The CMAP scan has potential value as a follow-up tool in monitoring disease progression, recovery or aging of the peripheral nerves. In this study, we assessed its interobserver and different-day reproducibility. Methods: Two investigators recorded CMAP scans in ten healthy subjects, each on two different days. Intraclass correlation coefficients (ICCs) and coefficients of variation (CoVs) were calculated for the parameters extracted from the CMAP scan. Results: All CMAP scan parameters had a good different day (ICCs >0.8 and CoVs <15%) and interobserver reproducibility (ICCs >0.7 and CoVs ≤15%). Different-day reproducibility was better than interobserver reproducibility. Conclusion: CMAP scan test-retest variability is small, suggesting that as a follow-up tool it may be sensitive to fairly small (patho)physiological changes in the studied variables.

Motor unit tracking with high-density surface EMG (Article)

2008-12-01T00:00:00Z

Following (tracking) individual motor units over time can provide important new insights, both into the relationships among various motor unit (MU) morphological and functional properties and into how these properties are influenced by neuromuscular disorders or interventions. The present study aimed to determine whether high-density surface EMG (HD-sEMG) recordings, which use an array of surface electrodes over a muscle, can increase the yield of MU tracking studies in terms of the number of MUs that can be tracked. For that purpose, four HD-sEMG recording sessions were performed on the thenar muscles of ten healthy subjects. Decomposition of the recorded composite responses yielded a study total of 2849 motor unit action potentials (MUAPs). MUAPs that were found in both of the first two sessions, performed on the same day, were defined as trackable MUAPs. Our results show that 22 (median value; range, 13-34) MUAPs per nerve were trackable, which represented approximately 5% of the total MU population. Of these trackable MUAPs, 16 (11-26) could also be found in one or both of the third and fourth sessions, which were performed between 1 and 13 weeks after the initial studies. Nine (4-18) MUAPs were found in all four sessions. Many of the characteristic MUAP shapes matched well between sessions, even when these sessions were several weeks apart. However, some MUAPs seem very sensitive to changes in arm position or in the muscle's morphology (e.g., to changes in muscle fiber length due to variable degrees of thumb flexion or extension), particularly those from larger and/or superficial MUs. Standardization is, therefore, essential to detect even small MUAP changes, as may occur with pathology or interventions. If this is accomplished, MU tracking with HD-sEMG may prove to be a powerful tool for a promising type of neurophysiological investigation.

Limb temperature and nerve conduction velocity during warming with hot water blankets (Article)

2008-04-01T00:00:00Z

Electrodiagnostic assessments of the peripheral nervous system often require limb warming. The traditional warming method, the hot water bath, has several disadvantages. We present an alternative: hot water blankets containing circulating water of a constant temperature. In addition to having practical advantages, these blankets allow for accurate and continuous monitoring of limb temperature and nerve conduction velocity (NCV) during warming. We therefore aimed to determine (1) the temperature dependence of the NCV of the median motor and sensory nerve, deep peroneal nerve, and sural nerve during warming with blankets, and (2) the optimal warming strategy for clinical purposes. We warmed the limbs of 10 subjects for 90 minutes with blankets set at a temperature of 41°C. During warming, the NCV of the three nerves and distal motor latency of the two motor nerves were measured every 21/2 minutes. After 25 minutes of warming from an initial temperature of 28°C, the NCV and distal motor latency of all nerves were within the normal range. However, after median nerve warming until a predefined temperature of 34°C (i.e., for 17 minutes on average), two of nine subjects showed abnormal NCVs. We therefore conclude that for limb warming with hot water blankets, a fixed 25-minute warming period is optimal. Copyright