Transcranial magnetic stimulation compared with upper motor neuron signs in patients with amyotrophic lateral sclerosis

If patients with amyotrophic lateral sclerosis (ALS) present without upper motor neuron signs (UMNS) they do not meet current ALS research criteria. T o compare how sensitively degeneration of upper motor neurons is detected c linically and by transcranial magnetic stimulation, 35 patients with ALS we re studied. Nineteen patients had definite UMNS, nine patients had probable UMNS, and seven patients had no UMNS. Cortex, cervical nerve roots, and lu mbar plexus were stimulated with a magnetic stimulator. Compound muscle act ion potentials from abductor digiti minimi and from anterior tibial muscles were recorded with surface electrodes. Responses to transcranial magnetic stimulation were considered abnormal if central motor conduction time was a bove the 99% upper limits or if there was no response to cortical but to pe ripheral stimulation. In all patients with definite UMNS central motor cond uction was abnormal. In patients with probable UMNS it was abnormal in 67%, and in patients without UMNS it was abnormal in 71%. Abnormality of centra l motor conduction was neither correlated with the duration nor with the se verity of the disease. The high rate of abnormalities of central motor cond uction found in patients with ALS but without definite UMNS suggests that, in these patients, the diagnosis of ALS can be made more reliably if transc ranial magnetic stimulation studies are performed. (C) 1999 Elsevier Scienc e B.V. All rights reserved.