D.A. Ingram

Central motor conduction in multiple sclerosis: evaluation of abnormalities revealed by transcutaneous magnetic stimulation of the brain.

Magnetic stimulation of the brain and spinal column was used to assess conduction in the descending central motor pathways controlling arm and leg muscles of 20 patients with multiple sclerosis, and 10 normal subjects. The multiple sclerosis patients had relapsing and remitting disease but all were ambulant and in stable clinical remission. Increased central motor conduction times (CMCTs), up to three times normal, were frequently encountered in multiple sclerosis patients and in leg muscles these correlated closely with clinical signs of upper motor neuron disturbance; in the upper limb muscles a higher proportion of subclinical lesions was present. Weak muscles were almost invariably associated with abnormal central conduction but increased CMCTs were also found for 52 of the 104 muscles with normal strength. CMCTs for lower limb muscles were directly related (p less than 0.005) to functional motor disability (Kurtzke and Ambulatory Index Scales). No patient developed clinical evidence of relapse during follow-up of at least 8 months. Magnetic brain stimulation is easy to perform, painless, and safe, and provides clinically relevant information in the diagnosis and monitoring of multiple sclerosis patients.

Motor nerve conduction velocity distributions in man: results of a new computer-based collision technique

A new computer-based collision technique for direct measurement of the human motor nerve conduction velocity distribution is described. In contrast to previous collision techniques, the test muscle response is progressively cancelled to a null using an arrangement of proximal and distal stimuli which eliminates distortion of the test response caused by transient changes in nerve and muscle fibre conduction. The increased sensitivity of this new technique permits accurate measurement of the slowest 1% of alpha motor nerve fibres. We have used our modified collision technique to determine motor nerve conduction velocity distributions for the median nerve in 20 normal subjects aged between 19 and 59 (mean 35) years. 150% maximal stimulus intensities were used, with a controlled limb temperature of 35 degrees C. Group mean velocities (+/- S.D.) for the fastest (95%), mean (50%) and slowest (5% and 1%) motor fibres were 59.1 +/- 3.0, 56.9 +/- 2.9, 52.7 +/- 3.1 and 51.2 +/- 3.7 m/sec respectively. Data are also presented for the ulnar and peroneal nerves.

The double collision technique: a new method for measurement of the motor nerve refractory period distribution in man ☆

A new, double collision, technique is described for non-invasive measurement of the motor nerve refractory period distribution for human peripheral nerves. In contrast to previous collision techniques, this method is independent of the transient changes in nerve and muscle fibre conduction which can distort test muscle responses. The end-point of the distribution is determined by a null response; this permits accurate identification of those nerve fibres with the longest refractory periods. We have used the double collision technique to measure the refractory period distributions for the median nerve at the wrist in 20 normal subjects aged between 22 and 58 (mean 35) years. 150% maximal stimuli were used with a controlled limb temperature of 35 degrees C. Following a conditioning stimulus, the mean latencies for recovery of 5%, 50%, 95% and 99% of motor nerve fibres were 0.94, 1.03, 1.12 and 1.23 msec respectively. Data are also presented for the ulnar and peroneal nerves. The results show that the human motor nerve refractory period distribution is much less dispersed than has been previously supposed.

Cancer-associated myasthenic (Eaton-Lambert) syndrome: distribution of abnormality and effect of treatment.

Treatment with plasma exchange, steroids, immunosuppressant drugs and cytotoxic chemotherapy was effective in two cases of cancer-associated Eaton-Lambert myasthenic syndrome. The clinical improvement noted during treatment was accompanied by improvement in the electrophysiological abnormality; this was much more marked in abductor digiti minimi and trapezius than in extensor digitorum brevis.

Paraneoplastic painful ulnar neuropathy

A 58‐year‐old woman developed painful, bilateral ulnar neuropathy in conjunction with small cell lung carcinoma and high serum titer of anti‐Hu antibody. An incidental stage I plasma cell dyscrasia, with immunoglobulin G kappa monoclonal protein, was also present. Electropysiological assessment excluded a generalized neuropathy, and nerve biopsy showed marked loss of myelinated and small unmyelinated fibers, without inflammatory changes or amyloid deposition. High titers of circulating anti‐Hu antibody can be associated with symptoms resembling a paraneoplastic mononeuropathy.

The effect of continuous voluntary activation on neuromuscular transmission: A SFEMG study of myasthenia gravis and anterior horn cell disorders

In normal subjects the neuromuscular jitter does not increase during continuous voluntary activation. In patients with myasthenia gravis, spinal muscular atrophy and motor neurone disease we have found that the neuromuscular jitter may increase during recordings of several minutes of continuous voluntary activation at steady innervation rates. In some units this led to impulse blocking, and in other units an initially normal jitter increased beyond the normal range. Measurement of jitter during continuous voluntary activation at steady innervation rates provides relevant information in the evaluation of neuromuscular transmission and fatigue in these disorders.