Visser, G.H.

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.

Electroencephalography during normotensive and hypertensive pregnancy: A systematic review (Article)

2010-12-01T00:00:00Z

The objective of this review was to evaluate the available medical literature concerning the electroencephalogram (EEG) during hypertensive disorders of pregnancy. All articles found during a MEDLINE and Embase database search on the subject of EEG differences associated with hypertensive disorders in pregnancy were screened for eligibility. In all, 22 articles which describe the EEG during preeclampsia (PE)/eclampsia were retrieved. Abnormal EEG findings were observed in the majority of the preeclamptic/eclamptic patients, consisting of slow waves most frequently localized in the occipital lobe, as well as spike discharges. The EEG abnormalities in PE/eclampsia were reversible in the majority of the cases. We conclude that these described abnormalities may be interpreted as a warning sign of deterioration of brain function in PE/eclampsia. However, some caution regarding this conclusion is advised because most of the retrieved articles were published in the 1950s and 1960s, and were not consistent with current clinical guidelines or medical terminology. Further research is needed to establish the clinical value of implementing EEGs in the assessment of the preeclamptic/eclamptic patient. Target Audience: Obstetricians & Gynecologists, Neurologists, Family Physicians Learning Objectives: After completion of this educational activity, the obstetrician, gynecologist and neurologist should be better able to evaluate whether the EEG is normal for pregnancy; distinguish EEG abnormalities in hypertensive disorders in pregnancy, and assess the value of EEG abnormalities in preeclampsia (PE)/eclampsia for the detection of early signs of ischemia. Copyright

Time varying neonatal seizure localization (Article)

2010-12-01T00:00:00Z

Background: A common cause for damage to the neonatal brain is a shortage in the oxygen supply to the brain or asphyxia. Neonatal seizures are the most frequent manifestation of neonatal neurologic disorders. Multichannel EEG recordings allow topographic localization of seizure foci. Objectives: We want to objectively determine the spatial distribution of the seizure on the scalp, the location in time and order the dominant sources in the brain based on their strength. Methods: In this paper we combine a method based on higher order CP-decomposition with subsequent singular value decomposition (SVD). Results: We illustrate the abilities of the method on simulated as well as on real neonatal seizure EEG. Conclusions: The proposed method provides reliable time and spatial information about the seizure, gives a clear overview of what is going on in the EEG and allows easy interpretation.

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.

Histological validation of ultrasound-guided neurography in early nerve regeneration (Article)

2009-12-01T00:00:00Z

Ultrasound-guided near-nerve neurography is a new tool that can be used to assess nerve regeneration before reinnervation occurs. In this study, ultrasound-guided near-nerve measurements were validated against axon diameter counts in rabbits during a 15-week regeneration period after a crush lesion of their peroneal nerve. The course of the nerve was determined ultrasonically, and the active near-nerve needle electrode was maneuvered just next to the nerve under ultrasound guidance. Measured action potentials were compared with axon diameter counts from histological sections of these same nerves. A moderate to good positive correlation was found, which reached a maximum of 0.7 at a cut-off of 3 μm, corresponding to the minimal size of the myelinated axons. Our results suggest that, following a similar validation study in humans, ultrasound-guided near-nerve neurography may be clinically useful when early evaluation of nerve activity is needed.

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

The electrophysiological muscle scan (Article)

2007-10-01T00:00:00Z

This study aims to assess the potential of the electrophysiological muscle scan or stimulus-response curve as a diagnostic instrument. If stimulus intensity is gradually increased from subthreshold to supramaximal values, all motor units in a muscle are successively activated. Thus, by plotting response size versus stimulus intensity, an impression (scan) of the entire muscle can be obtained. We recorded 54 detailed scans from 34 patients and 11 healthy subjects, and analyzed them visually and quantitatively. The scan summarized much diagnostic information in a single picture. Specific patterns in or properties of the scan (steps, maximum, variability, decrements, stimulus intensities used) provide clinically relevant information regarding motor unit number, size, and stability, and neuromuscular transmission and axonal excitability. The scan can be recorded noninvasively in about 5 minutes and is fairly easy to interpret. Because it is built up from contributions of all functioning motor units, the scan shows if and how many large motor units are present. There is no sample bias. For these reasons, further exploration and exploitation of this tool in the clinical setting are warranted.

Continuous noninvasive monitoring of barbiturate coma in critically ill children using the Bispectral™ index monitor (Article)

2007-09-27T00:00:00Z

Introduction: Traumatic brain injury and generalized convulsive status epilepticus (GCSE) are conditions that require aggressive management. Barbiturates are used to lower intracranial pressure or to stop epileptiform activity, with the aim being to improve neurological outcome. Dosing of barbiturates is usually guided by the extent of induced burst-suppression pattern on the electroencephalogram (EEG). Dosing beyond the point of burst suppression may increase the risk for complications without offering further therapeutic benefit. For this reason, careful monitoring of EEG parameters is mandatory. A prospective study was conducted to evaluate the usefulness of the bispectral index suppression ratio for monitoring barbiturate coma. Methods: A prospective observational pilot study was performed at a paediatric (surgical) intensive care unit, including all children with barbiturate-induced coma after traumatic brain injury or GCSE. The BIS™ (Bispectral™ index) monitor expresses a suppression ratio, which represents the percentage of epochs per minute in which the EEG was suppressed. Suppression ratios from the BIS monitor were compared with suppression ratios of full-channel EEG as assessed by quantitative visual analysis. Results: Five patients with GCSE and three patients after traumatic brain injury (median age 11.6 years, range 4 months to 15 years) were included. In four patients the correlation between the suppression ratios of the BIS and EEG could be determined; the average correlation was 0.68. In two patients, suppression ratios were either high or low, with no intermediate values. This precluded determination of correlation values, as did the isoelectric EEG in a further two patients. In the latter patients, the mean ± standard error BIS suppression ratio was 95 ± 1.6. Conclusion: Correlations between suppression ratios of the BIS and EEG were found to be only moderate. In particular, asymmetrical EEGs and EEGs with short bursts (less than 1 second) may result in aberrant BIS suppression ratios. The BIS monitor potentially aids monitoring of barbiturate-induced coma because it provides continuous data on EEG suppression between full EEG registrations, but it should be used with caution.