R. Arunachalam

Critical illness myopathy: further evidence from muscle-fiber excitability studies of an acquired channelopathy.

Recent studies have demonstrated acquired muscle inexcitability in critical illness myopathy (CIM) and have used direct muscle stimulation (DMS) techniques to distinguish neuropathy from myopathy as a cause of weakness in the critically ill. The mechanisms underlying weakness in CIM are incompletely understood and DMS is only semiquantitative. We report results from a series of 32 patients with CIM and demonstrate significant slowing of muscle‐fiber conduction velocity (MFCV) and muscle‐fiber conduction block during the acute phase of CIM, which correlates with prolonged compound muscle action potential (CMAP) duration, clinical severity, and course. We also used a paired stimulation technique to explore the excitability of individual muscle fibers in vivo. We demonstrate altered muscle‐fiber excitability in CIM patients. Serial studies help define the course of these pathophysiological changes. Parallels are made between CIM and hypokalemic periodic paralysis. Our findings provide further evidence for muscle membrane dysfunction being the principal underlying abnormality in CIM. Muscle Nerve, 2007

Differences in motor activation of voluntary and reflex cough in humans

Objectives: To study motor activation patterns of voluntary and reflex cough adjusted for cough flow rates. Methods: Surface electromyography (EMG) and cough flow rate were measured in 10 healthy volunteers. Voluntary cough was assessed for 20 efforts in each quintile of increasing cough flow rate. Reflex cough was assessed for 25 efforts produced by nebulised l-tartaric acid. EMG was recorded over the expiratory (rectus abdominis, obliques, lower intercostals) and accessory (trapezius, pectoralis major, deltoid, latissimus dorsi) muscles. EMG activity, burst duration and onset were compared for each quintile of voluntary cough, and between voluntary and reflex cough matched for cough flow rate. Results: EMG activity and burst duration of expiratory and accessory muscles during voluntary cough increased in proportion to cough flow. Expiratory muscles had longer EMG burst duration (difference 68 ms (95% CI 34 to 102), p<0.01) and earlier onset of EMG activity (difference 44 ms (95% CI 20 to 68), p<0.0001) compared with accessory muscles. EMG activity in all muscles was increased (mean 110.2% v 56.1%, p<0.001) and burst duration (mean 206 ms v 280 ms, p = 0.013) decreased in reflex cough compared with voluntary cough of equal flow rate. There were no differences in EMG onset (difference 8 ms (95% CI 25 to −9) or burst duration (difference 27 ms (95% CI 58 to −4) between expiratory and accessory muscles. Conclusions: Functional organisation of motor activity differs between voluntary and reflex cough. Voluntary cough is characterised by sequential activation whereas reflex cough is associated with early and simultaneous activation of expiratory and accessory muscles.

Late EEG responses triggered by transcranial magnetic stimulation (TMS) in the evaluation of focal epilepsy

Purpose: To evaluate the use of EEG responses to transcranial magnetic stimulation (TMS‐EEG responses) as a noninvasive tool for the diagnosis of focal epilepsy.

Transcutaneous cervical root stimulation in the diagnosis of multifocal motor neuropathy with conduction block

Objectives: To determine if transcutaneous electrical stimulation of the cervical roots can be used to diagnose proximal conduction block (CB) in multifocal motor neuropathy (MMN) and whether it can reliably distinguish MMN from amyotrophic lateral sclerosis (ALS). Methods: Compound muscle action potentials (CMAPs) over the abductor digiti minimi (ADM) were evoked by supramaximal stimulation of the ulnar nerve at the wrist, below elbow, above elbow, axilla, Erb’s point, and C8/T1 cervical roots in three groups of patients: 31 patients with ALS, nine patients with MMN, and 31 controls. Supramaximal stimulation at Erb’s point and the C8/T1 roots was carried out using a transcutaneous high voltage electrical stimulator. The negative peak amplitude, area, and duration of the CMAP were measured and normalised to that from the wrist. The percentage change in each segment in these parameters was calculated and compared between the different groups. Results: At stimulation sites proximal to the elbow, there were no significant differences in relative CMAP amplitude, area, or duration between controls, ALS patients, and MMN patients with clinically unaffected ulnar nerves. Similarly, the percentage segmental change between adjacent stimulation sites showed no significant differences. In six studies of MMN patients with weakness in ulnar hand muscles, the decrease in CMAP amplitude between the C8/T1 roots and Erb’s point exceeded the mean + 2 SD of the control data. Conclusion: Cervical root stimulation can quantify CB in the most proximal segment of the ulnar nerve, a fall in CMAP amplitude if greater than 25%, indicating block, and should be used routinely in the evaluation of patients suspected of having MMN, especially when distal stimulation has proved unhelpful.

A treatable muscle disease

A 70-year-old woman presented with increasing weakness and fatigue over 4 years. She had suffered motor problems from birth with hypotonia and delayed motor milestones. She walked abnormally in childhood but appeared to show some improvement at the age of 10 years, remaining ambulant throughout her life. She was seen by an eminent neurologist at the age of 15 years who documented a waddling gait, and after investigation she was given a diagnosis of “amyotonia congenita”. At the age of 43 years she was reviewed; there had been no significant progression but she reported being intermittently worse during menstruation. Examination at that point revealed mild weakness of eye closure, mild right-sided ptosis, weakness and some wasting of the periscapular muscles and hip flexors. Investigations revealed mildly raised serum creatine kinase (CK) level (twice normal) and a myopathic electromyogram (EMG). Mild fibre hypertrophy and absence of type 2B fibres were noted on muscle biopsy and she was thought to have a form of congenital myopathy. However, from the age of 66 years she had increasing difficulty climbing stairs and could only walk for 60 m. She was unable to lift heavy objects or use her arms above her head, she had difficulty holding her head up, occasional choking and breathlessness on exertion and when lying flat. Examination revealed bilateral ptosis with little fatigability (fig 1), mild facial and neck weakness, and her tongue was weak and had a central furrow. There was no ophthalmoplegia. She had marked shoulder girdle weakness with some wasting and scapular winging. There was also marked weakness around the pelvic girdle; she walked with a waddling lordotic posture, was just about able to get out of a chair without using her arms and she could stand on her heels and toes. Her vital capacity was 80% of …

Facial muscle contraction in response to mechanical stretch after severe facial nerve injury: Clapham's sign

INTRODUCTION Following the onset of facial palsy, physiotherapists routinely inspect the inside of the patients mouth and cheek for complications such as ulceration or trauma. In several patients with complete facial nerve palsy, it was noticed that when the cheek was stretched there was subsequent spasm of the muscles of facial expression. This also occurred in patients whose facial nerve had been transected. CASE REPORTS We present four patients in whom this response was demonstrated. We consider the mechanism of this response and its relevance in the management of patients with facial paralysis. CONCLUSION Following severe or complete denervation, contraction of the facial muscles following mechanical stretch provides evidence of preservation of activity in the facial muscles excitation-contraction apparatus. Further research will investigate the clinical significance of this sign and whether it can be used as an early predicator of the development of synkinesis, as well as its relevance to facial nerve grafting and repair.

Re: A handheld nerve conduction measuring device in carpal tunnel syndrome. Tolonen U et al., Acta Neurol Scand 2007;115:390-397.

Dear Editor-in-chief, Re: A handheld nerve conduction measuring device in carpal tunnel syndrome. Tolonen U et al., Acta Neurol Scand 2007;115:390–397. We read with interest the paper from Tolonen et al. (Acta Neurol Scand 2007;115:390–397). Carpal tunnel syndrome (CTS) is the commonest upper limb nerve entrapment. Diagnosis can be suspected clinically to variable degrees and can be further supported by nerve conduction studies (NCS) of the sensory and motor function of the median nerve across the carpal tunnel segment. The authors agree that logically the shorter segment tested in palm–wrist segment studies means that they are more sensitive than ring finger studies for assessment of mild CTS. There is, however, variability in the clinical presentation and other conditions can mimic CTS. The sensitivity of clinical diagnosis and neurophysiological diagnosis is unknown. NCS allow the clinical diagnosis to be confirmed (when positive), allow grading of severity and allow for other conditions to be actively excluded. New methods and technologies are always welcomed to enhance the diagnosis of CTS. Simpler methods and equipment, however, should always be weighed up against potential risks in terms of misdiagnosis and missed diagnosis. We praise the authors for their efforts and encourage their continued work in this important area. The authors sought to assess the diagnostic utility of a device that they themselves have developed. The paper was at times confusingly written, making it difficult to follow through what exactly happened to subjects. We have attempted to understand the results as best we can. The fact that the authors funded, performed and wrote the study, by means of the EMG Technologies Ltd, does raise concern; although this fact is openly disclosed in the paper. There are, however, also methodological and statistical aspects to the paper, which we feel make it flawed. First, although the paper seeks to compare the new device and method with traditional NCS in patients with suspected CTS, it is not explicitly stated how the diagnosis of CTS is made, clinically or neurophysiologically. We have presumed that this was clinically suspected and then confirmed by conventional NCS. They have not compared patients with suspected CTS as would be encountered in the clinic but have excluded certain patients from the study. They have excluded those with prior CTS surgery and more importantly those with a history or with NCS findings of any other neurological disorder that may produce numbness or paresthesia in the hand. If we have understood this correctly, the subjects studied are a highly selected group. This does not make a direct comparison of NCS and the new device invalid per se, but it does invalidate any attempt to extrapolate the findings to a clinical setting, where the case mix would be far different, and where initial NCS screening would not be undertaken. It would be anticipated that two machines performing the same function, that is sensory NCS, in a highly selected patient group, would needless to say, result in a high level of concordance between results. Despite this, the new device is neither as specific nor as sensitive as traditional NCS. Its use also raises concerns regarding potential patient misdiagnosis. For example, the device, as the authors state, would miss ulnar neuropathies, a condition not infrequently referred to clinics as CTS . This diagnosis would be picked up by a traditional dynamic, clinically driven NCS ⁄EMG examination, which would respond and alter the course according to the findings as they were found. In the case of the new device performed by non-neurophysiologically, nonmedically trained personnel, the patient would be classed as not having CTS, which would necessitate possibly two further appointments, one for a further clinical examination and then further NCS. This would clearly be uneconomical. There are several statistical and data analysis points that we feel require clarification. First, the terms sensitivity and specificity are incorrectly used (1). The authors report (p. 393) that the sensitivity of the new device is 97.3% . But sensitivity is actually the proportion of patients with CTS who are correctly diagnosed by using the new device. They are referring to the specificity. The sensitivity of the device therefore appears Acta Neurol Scand 2008: 118: 203–205 DOI: 10.1111/j.1600-0404.2007.00946.x Copyright 2007 The Authors Journal compilation 2007 Blackwell Munksgaard

W1.5 Clapham's sign; stretch sensitive contraction in the muscles of facial expression after complete denervation

Methods: We restrospectively revised patients with MMN diagnosed in our EMG laboratory during last 15 years with a follow-up higher than 5 years and analyze clinical and electrophysiological findings in 3 stages of the disease evolution. We quantified the number and sites of definite conduction blocks (CB), probable CB, anomalous temporal dispersion (ATD), and axonal degeneration (AD). We established the diagnosis of definite MMN, probable MMN and MADSAM according to AANEM criteria at the moment of diagnosis, after 2 years and 5 or more years of monitoring. Results: We found 11 patients (7 male:4 female, mean age of 43 years) with MMN followed between 5 and 11 years. A significant decrease of definite and probable CB and increase of nerves with AD has been found. Sensory involvement appeared in 3 patients, one of them with worst clinical and electrophysiological evolution. Five patients changed the diagnosis during the follow-up. Conclusions: In the follow-up of patients with MMN during more than 5 years there are changes in the pathophysiology of nerve injury (definite and probable CB, ATD and AD), in sensory involvement and diagnosis according to criteria of AANEM. This fact complicates the diagnosis and monitoring of this disease.

TP1.3 Single pulse transcranial magnetic stimulation in the evaluation of partial epilepsy

correlation between the mean FA index and the magnitude of IHI (r = 0.70; p = 0.02). Discussion: This significant positive correlation between FA index of callosal motor fibres and IHI strongly suggests that structural information (directionality of fibre bundles in the corpus callosum) closely links to function (inhibitory interaction between the motor cortices of the two hemispheres). Therefore, FA indices might be useful to predict variability of function in healthy individuals, and potentially, abnormality of function in neurological patients.

FC21.2 Usefulness of early EEG in predicting outcome in term neonates with hypoxic ischaemic encephalopathy

Background: Carpal tunnel syndrome (CTS) is a common disorder requiring electrodiagnosis (EDX). A reliable test protocol is needed. Aim(s)/Objectives(s): To carry out an audit of the EDX CTS protocol used in Oxford, UK. Methods: Data were prospectively collected from 200 consecutive patients: 133 women, 67 men (mean age 51.6 ± 14.4 years, range 18–93). Patients referred for a diagnosis of idiopathic CTS were assigned into a 3 grade clinical category scale using the validated hand symptom questionnaire (HSQ). Results: Using the HSQ, 148 patients were classified as definite CTS. Using a seven-scale (0–6) EDX grading system, 15% had normal EDX (grade 0), 7% showed abnormalities exclusively in the palm-to-wrist median, ulnar onset latency (OL) difference >0.32 ms (grade 1), 32% had abnormalities in the digit 3(D3)-to-wrist OL conduction velocity (CV) <45 m/s with distal latency (DL) to the abductor pollicis brevis (APB) <4.5 ms (grade 2), 22% showed prolonged but present D3-towrist response with DL-to-APB >4.5 ms (grade 3), 8% had absent D3-to-wrist responses with a DL-to-APB between 4.5 and 6.5 ms (grade 4), 12% showed DL-toAPB >6.5 ms (grade 5), 3% had either no response to the APB or an amplitude of the waveform <0.2 mv (grade 6). From the 25 clinically not-possible CTS group, 84% showed normal EDX. The minimum D5to-wrist OL CV was 46 m/s. Conclusions: In suspected CTS start by looking for median digital sensory conduction slowing (orthodromic D3-to-wrist, OL CV <45 m/s and D5-to-wrist OL CV >45 m/s). If D3-to-wrist OL CV >45 m/s and <56 m/ s, check mixed nerve palm-to-wrist median and ulnar responses for a latency difference >0.32 ms. Very severe CTS was defined by a DL-to-APB >6.5 ms, as 80% of the hands examined above this cut-off point had absent D3 sensory responses. Our protocol allows a 7-scale (0–6) EDX grading that correlated significantly with the 3-grade clinical grouping (correlation coefficient 0.33, 95% CI = 0.21–0.44, p < 0.0001, using Kendall’s tau-b test).