J P Ballantyne

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.

A new method for the estimation of the number of motor units in a muscle: 1. Control subjects and patients with myasthenia gravis

A new method, incorporating on-line computer analysis, is described for the estimation of the numbers of motor units in human muscle. The results obtained in the extensor digitorum brevis muscle in normal subjects and patients with myasthenia gravis are presented. These indicate that the numbers of motor units in that muscle in patients with myasthenia gravis are within the normal range, in contrast with the reduction in numbers reported by other workers using a different technique. Evidence is presented to suggest that the discrepancy in these results is due to increased sensitivity and discrimination of the computerized method. Several hypotheses on the aetiology of a number of neuromuscular diseases, based on the results of the other method, may require reevaluation.

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.

New method for the estimation of the number of motor units in a muscle. 2. Duchenne, limb-girdle and facioscapulohumeral, and myotonic muscular dystrophies.

The results of the application of a computerized method for the estimation of motor unit numbers in the human extensor digitorum brevis are presented. In patients with Duchenne and limb-girdle and facioscapulohumeral muscular dystrophies, motor unit numbers are within the normal range, but are significantly reduced in myotonic muscular dystrophy.

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.

Regeneration of sutured human peripheral nerves: an electrophysiological study.

Electrophysiological and clinical assessment of recovery of function was undertaken on 34 median and 33 ulnar nerve which had been resutured after complete section three and a half months to 24 years previously. An evaluation of different methods of repair was attempted. Our results suggested that re-exploration of the site of suture is indicated in the absence of voluntary activity on needle EMG by seven months (12 months for grafts), of an electrically evoked muscle action potential, measurable distal motor latency, or motor nerve conduction velocity by 10 months (14 months for grafts), or of clinically detectable voluntary muscle movement by 10 months after suture. By present techniques of repair useful prognostic information cannot be obtained by a consideration of sensory parameters either clinical or electrophysiological.

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.

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.

Anterior horn cell dysfunction in Alzheimer's disease.

Electrophysiological studies were undertaken on 29 patients with Alzheimers Disease. A reduction in the number of functioning motor units was found in the extensor digitorum brevis muscle. The electrophysiological parameters of the motor unit potentials were increased compared to control values. Four of seven muscle biopsies showed abnormalities ranging from mild to severe. The results suggest dysfunction in the lower motor neurone in this disease.