Transcranial magnetic stimulation as a diagnostic and prognostic test in amyotrophic lateral sclerosis.

Corticospinal stimulus conduction was investigated after transcranial magnetic stimulation of the motor cortex in 63 patients (20 female, 43 male, 59 +/- 12 years) with amyotrophic lateral sclerosis (ALS) and progressive bulbar palsy. Recordings were made bilaterally from the Abductor digiti minimi muscle (ADM) in the hand and the Tibialis anterior muscle (TA) in the leg. Thirteen patients were re-examined after 250 +/- 125 days. Eight patients were examined a third time after 552 +/- 165 days. At the first investigation central motor conduction time was abnormal to one or more target muscles in 51% (n = 32) of all patients. No significant delay in CMCT developed during follow-up. The average time of survival of patients with normal CMCT at the first investigation was 16.5 +/- 7.5 months, and 14.7 +/- 8.8 months in patients with abnormal CMCT. This is not a significant difference. It is therefore concluded that transcranial magnetic stimulation is not a sensitive tool in the diagnosis of ALS. Furthermore, CMCT does not provide significant prognostic information.

[Effect of temperature on clinical electrophysiology]. / Einfluss der Temperatur in der klinischen Elektrophysiologie.

Body temperature has a considerable impact on neurophysiological results. This influence of temperature is often undervalued. Abnormal findings even in healthy subjects can be caused by cold extremities only. Low surface temperature for example may lead to longer distal latencies and slower motor and sensory nerve conduction velocities. In patients with neuromuscular diseases typical results may disappear, when the examination is done beyond a standard temperature. In myasthenic patients the decrement and the jitter in single fibre electromyography decrease with temperature. In myasthenic syndrome the amplitude of the muscle compound action potentials increases and the increment at 50/s-stimulation becomes smaller at low temperature. Cold limbs lead to restoring nerve conduction in demyelinated nerve fibres; conduction block may thus disappear. Spontaneous activity becomes rare and myotonic discharges become more obvious at low temperature. In certain cases an examination at low temperatures can be helpful, e.g. for the distinction between myotonia and paramyotonia. Usually electrophysiological examinations should be done at standard temperatures.