A I Weir

An improved automated method for the measurement of thermal thresholds. 1. Normal subjects.

Clinical tests of thermal sensation are poorly quantified and not strictly modality specific. Previous automated thermal testing systems have had limited usefulness with high intra-and inter-individual variability. This paper describes an automated thermal system (Glasgow system) which is an extensive modification of previous techniques to answer these criticisms. It comprises a microprocessor-driven Peltier element and utilises the forced choice method of psychophysical analysis to determine the thresholds to thermal stimulation. In a control group of 106 healthy subjects the mean heat threshold for the wrist was found to be 0.23 degree C (SD = 0.06 degree C) and the mean cold threshold 0.15 degree C (SD = 0.05 degree C). Repeated determinations showed a maximum of 5% intra-individual variation in comparison to previously reported values of up to 150%.

Thermal discrimination thresholds in normal subjects and in patients with diabetic neuropathy.

Using two identical thermostimulators which operated on the Peltier principle, thermal cutaneous sensation of the hand and the foot was investigated in 36 normal subjects and in 20 patients with diabetic neuropathy. Using a two-alternative forced-choice testing procedure, thermal discrimination thresholds were determined twice. The values found in normal subjects are comparable with data from the literature. It was confirmed that thermal discrimination of the foot decreased with increasing age. In patients with diabetic neuropathy the increased thresholds for the foot could be correlated with length-dependent degeneration of small nerve fibres.

Antenatal fetal magnetocardiography: a new method for fetal surveillance?

Objective To establish the reliability of fetal magnetocardiography as a method of measuring the time intervals of the fetal heart during the antenatal period.

An improved automated method for the measurement of thermal thresholds. 2. Patients with peripheral neuropathy.

Thermal thresholds were determined by a new technique, at wrists and ankles in 143 patients with peripheral neuropathies of diverse aetiologies. Ninety-nine percent of patients (141/143) had abnormalities of one or both thresholds. In only two patients with mild/early Friedreichs ataxia were thermal thresholds normal. Electromyography was performed and fastest motor nerve conduction velocities and sensory nerve action potential parameters were measured in all the patients using conventional techniques in ulnar, median and sural nerves. Eighty-nine percent of patients (127/143) had one or more abnormalities on these electrophysiological studies. However, 39 of 40 patients with completely normal sensory nerve studies had an abnormality of one or more thermal thresholds. Eighty-six percent of 48 patients with normal sural nerve studies had abnormal thermal thresholds at the ankle. Sixty percent of 70 patients with normal sensory median and ulnar nerve studies had abnormal wrist thermal thresholds. This improved technique for the determination of thermal thresholds reveals that disturbances of thermal sensibility are present in the majority of peripheral neuropathies irrespective of aetiology. In some patients disturbances of thermal thresholds antedate the appearance of abnormalities on conventional electrophysiological investigation. The findings suggest that this technique has considerable usefulness in the detection of small nerve fibre dysfunction in the context of generalised neuropathy.

Neurological involvement in legionellosis

A study of the clinical, electrophysiological and biochemical features of 16 patients with legionellosis has been performed. Evidence of central and peripheral nervous system involvement has been found in the majority of patients. This is characterised by confusion out of keeping with the degree of toxic or metabolic upset, signs of anterior midline cerebellar dysfunction, grossly elevated creatinine kinase of skeletal muscle origin, and a subclinical peripheral neuropathy.

Concentric and single fiber needle electrodes yield comparable jitter results in myasthenia gravis.

The single fiber needle electrode (SFNE), which is designed to isolate single muscle fiber action potentials, has played an important role in the diagnosis of myasthenia gravis (MG). However, the concentric needle electrode (CNE) has been recently adopted by some workers to study neuromuscular instability in MG, and reference data have also been obtained in healthy subjects. In this study we wanted to establish whether data acquired using the SFNE is comparable to that obtained using the CNE when studying patients with MG. We established reference data for our laboratory using the CNE for orbicularis oculi (OO) and extensor digitorum communis (EDC). We compared data from 24 MG patients using both SFNE and CNE and found no significant differences in mean jitter values for either muscles. We correlated the neurophysiological data obtained by either electrode with various clinical assessments, the ice pack test, OO and EDC strength measurement, and MGFA classification of disease, and we found no significant relation. We compared discomfort scores for the two needle electrodes for each muscle and found that the discomfort scores for CNE are significantly lower (P = 0.0004). We conclude that the CNE is a useful alternative electrode for studying single fiber potentials, but more reference data from normal control subjects is desirable. Muscle Nerve, 2008

Single fibre electromyographic jitter in multiple sclerosis.

Recent histological and electrophysiological reports have given evidence for peripheral nervous system (PNS) involvement in multiple sclerosis. We have applied the single fibre electromyography (SFEMG) technique to 15 patients with multiple sclerosis. Six patients had clearly abnormal jitter and two of these had previously undiagnosed coexistent peripheral neuropathy. A further five patients had borderline abnormalities of SFEMG. The mean jitter for each patient was abnormal in 10 patients. This was clear evidence for PNS involvement in this disease. Theoretically, the site of the abnormality could be in the terminal nerve network or at the neuromuscular junction, but this technique cannot distinguish between these sites.

Cerebral cortical potentials to pure non-painful temperature stimulation: an objective technique for the assessment of small fibre pathway in man.

In six healthy subjects cortical potentials were evoked by rapidly changing heating or cooling stimuli to the hand. Recordings were made from the contralateral scalp area overlying the sensori-motor cortex, referred to a frontal reference. The potential averaged from 25 stimuli comprised a large positive wave with a mean amplitude of 9.2, SD 1.1 microV for heat and 8.8 SD 1.2 micro V for cold stimulation. The heat evoked potentials had longer peak latencies (range: 280-350 ms) than those elicited by cold stimuli (range: 178-200 ms). A lower amplitude positive wave of a longer latency was also recorded to both modes of stimulation over the corresponding ipsilateral cortex. Cortical thermal evoked potentials were absent in two patients, one with severe selective small fibre neuropathy and the other with syringomyelia, both of whom had high thermal thresholds demonstrated by the technique of Jamal et al. Cerebral potentials evoked by thermal stimuli may represent an alternative approach to the investigation of the central projections of the human small fibre system with both clinical and research potential.

Open letter to prime minister David Cameron and health secretary Andrew Lansley

Neurologists and paediatricians call for action on “massive” rises in the prices of orphan drugs

Quantitative electrophysiological study of alcoholic neuropathy.

Thirty-one chronic alcoholic patients were investigated using quantitative electrophysiological techniques. Estimates of the numbers of functioning motor units in the extensor digitorum brevis muscles and measurements of the parameters of the potentials of these units are presented along with the values for motor nerve conduction velocities in the innervating lateral popliteal nerves. Motor conduction velocities and sensory nerve action potential amplitudes were also measured in the ulnar nerves. The results and their inter-relationships lead us to conclude that the slowing of motor nerve conduction and reduction in sensory nerve action potential amplitudes in alcoholic neuropathy are a consequence of axon loss. We found no evidence of pathological slowing of conduction in surviving axons. Reinnervation by functioning motor axons is poor compared to a number of other neuropathic conditions. In our patients there was no evidence of preferential involvement of sensory axons. The results support a predominant axonal dysfunction in alcoholic neuropathy.