Guillain-Barré syndrome mimicking botulism in early disease course.

A 42-year-old man, returning to Europe after a 2-month stay in China, reported cough and runny nose. Five days later, he developed neck discomfort and rapidly evolving weakness, spreading from his arms to the facial, bulbar and neck muscles, and then the legs. He developed dysphagia and breathlessness, and was intubated in the emergency department. Cerebrospinal fluid showed mildly elevated protein. On day 2 he had fixed dilated pupils, with absent oculocephalic reflexes, and a flaccid upper limb paralysis. MR scans of the brain and spinal cord were normal. The early features of descending weakness, bulbar involvement and fixed dilated pupils made it difficult to distinguish between Guillain-Barré syndrome and botulism, and early investigations were inconclusive. We initially gave both botulinum antitoxin and intravenous immunoglobulin, but initially delayed plasma exchange as this would have removed the botulinum antitoxin. Diagnostic testing for botulism has low sensitivity, so we urge pre-emptive treatment if it is clinically suspected.

Targeted mutation of mouse skeletal muscle sodium channel produces myotonia and potassium-sensitive weakness.

Hyperkalemic periodic paralysis (HyperKPP) produces myotonia and attacks of muscle weakness triggered by rest after exercise or by K+ ingestion. We introduced a missense substitution corresponding to a human familial HyperKPP mutation (Met1592Val) into the mouse gene encoding the skeletal muscle voltage-gated Na+ channel NaV1.4. Mice heterozygous for this mutation exhibited prominent myotonia at rest and muscle fiber-type switching to a more oxidative phenotype compared with controls. Isolated mutant extensor digitorum longus muscles were abnormally sensitive to the Na+/K+ pump inhibitor ouabain and exhibited age-dependent changes, including delayed relaxation and altered generation of tetanic force. Moreover, rapid and sustained weakness of isolated mutant muscles was induced when the extracellular K+ concentration was increased from 4 mM to 10 mM, a level observed in the muscle interstitium of humans during exercise. Mutant muscle recovered from stimulation-induced fatigue more slowly than did control muscle, and the extent of recovery was decreased in the presence of high extracellular K+ levels. These findings demonstrate that expression of the Met1592ValNa+ channel in mouse muscle is sufficient to produce important features of HyperKPP, including myotonia, K+-sensitive paralysis, and susceptibility to delayed weakness during recovery from fatigue.

Identifying lumbosacral plexus nerve root abnormalities in patients with sciatica using 3T readout-segmented echo-planar diffusion weighted MR neurography.

OBJECTIVES: To investigate the accuracy of Diffusion Weighted Imaging (DWI) using the Readout Segmentation of Long Variable Echo-trains (RESOLVE) sequence in detecting lumbosacral nerve abnormalities. METHODS: Following institutional ethics committee approval, patients with sciatica-type lower limb radicular symptoms (n = 110) were recruited and prospectively scanned using 3T MRI. Additional participants (n = 17) who underwent neurophysiological testing (EMG/NCV), were also prospectively studied. In addition to routine lumbar spine MRI, a DWI-RESOLVE sequence of the lumbosacral plexus was performed. Two radiologists, blinded to the side of patient symptoms, independently evaluated the MR images. The size and signal intensity changes of the nerves were evaluated using ordinal 4-point Likert-scales. Signal-to-noise ratio (SNR), apparent diffusion coefficient (ADC) and size were measured for affected and normal nerves. Inter-observer agreement was determined with kappa statistics; κ. RESULTS: In patients who did not undergo EMG/NCV testing (n = 110), the DWI-RESOLVE sequence detected lumbosacral nerve abnormalities that correlated with symptoms in 36.3% (40/110). This is a similar percentage to patients who underwent EMG/NCV testing, which was positive and correlated with symptoms in 41.2% (7/17). Inter-observer agreement for evaluation of lumbosacral nerve abnormalities was excellent and ranged from 0.87 to 0.94. SNR and nerve size measurements demonstrated statistically significant differences for the L5 and S1 nerves (p value < 0.05) for patients who did not undergo EMG/NCV testing. CONCLUSION: The DWI-RESOLVE sequence is a promising new method that may permit accurate detection and localization of lumbar nerve abnormalities in patients with sciatica.

Formative evaluation of a telemedicine model for delivering clinical neurophysiology services part I: utility, technical performance and service provider perspective.

BACKGROUND: Formative evaluation is conducted in the early stages of system implementation to assess how it works in practice and to identify opportunities for improving technical and process performance. A formative evaluation of a teleneurophysiology service was conducted to examine its technical and sociological dimensions. METHODS: A teleneurophysiology service providing routine EEG investigation was established. Service use, technical performance and satisfaction of clinical neurophysiology personnel were assessed qualitatively and quantitatively. These were contrasted with a previously reported analysis of the need for teleneurophysiology, and examination of expectation and satisfaction with clinical neurophysiology services in Ireland. A preliminary cost-benefit analysis was also conducted. RESULTS: Over the course of 40 clinical sessions during 20 weeks, 142 EEG investigations were recorded and stored on a file server at a satellite centre which was 130 miles away from the host clinical neurophysiology department. Using a virtual private network, the EEGs were accessed by a consultant neurophysiologist at the host centre for interpretation. The model resulted in a 5-fold increase in access to EEG services as well as reducing average waiting times for investigation by a half. Technically the model worked well, although a temporary loss of virtual private network connectivity highlighted the need for clarity in terms of responsibility for troubleshooting and repair of equipment problems. Referral quality, communication between host and satellite centres, quality of EEG recordings, and ease of EEG review and reporting indicated that appropriate organisational processes were adopted by the service. Compared to traditional CN service delivery, the teleneurophysiology model resulted in a comparable unit cost per EEG. CONCLUSION: Observations suggest that when traditional organisational boundaries are crossed challenges associated with the social dimension of service delivery may be amplified. Teleneurophysiology requires a governance and management that recognises its socio-technical nature.

Formative evaluation of a telemedicine model for delivering clinical neurophysiology services part II: the referring clinician and patient perspective.

BACKGROUND: Feedback from service users will provide insight into opportunities for improvement so that performance can be optimised. In the context of a formative evaluation referring clinician and patient satisfaction with a teleneurophysiology service was examined during a 20 week pilot period. METHODS: Questionnaire surveys of referring clinicians and patients were conducted. RESULTS: Fifteen (58%) clinicians responded to the first part of a postal survey which examined their satisfaction with traditional clinical neurophysiology services. Nine (35%) responded to a second part which assessed their experience with the teleneurophysiology service. Teleneurophysiology improved satisfaction with waiting times, availability of results and impact on patient management. There was unanimous support from the clinicians for the permanent development of a teleneurophysiology service, although 2 cautioned this could delay establishing a neurology service in their region.Eighty-two percent (116/142) of patients responded to a survey of their satisfaction with teleneurophysiology. This was compared to a previous report of 322 patients' experience with traditional CN services in Ireland. Waiting times for appointment were shorter for the former group who supported the telemedicine model recognising that it reduced the travel burden and need for overnight journeys. The two groups were equally anxious about the investigation although the teleneurophysiology patients received more prior information. CONCLUSION: This study illustrates that teleneurophysiology is an acceptable model of service delivery for its primary customers. Their feedback is important in informing appropriate design and governance of such innovative models of health service provision.

Transcranial magnetic stimulation.

Transcranial magnetic stimulation (TMS) is a noninvasive and painless method of stimulating the cerebral cortex that allows the study of cortical excitability and inhibition. This article describes the technique, the parameters most commonly studied, the clinical applications of TMS, and potential research applications.