Electrophysiological studies on the "stiff-man" syndrome.

In addition to anamnestic and clinical data electrophysiological and pharmacokinetic investigations may be necessary for the diagnosis of stiff man syndrome. Continuous activity of motor units with superimposed bursts during muscular spasms was found by electromyography in the two patients reported. Rigidity and continuous activity disappears during sleep, after i.v. application of Tubocurarine and Diazepam, during Thiopenal anesthesia and after neural block with Procaine. Dipropylacetate and Baclofen improved the condition but did not lead to complete relaxation. Biperidenlactat and Magnesiumlaevulinat have only a temporary effect on rigidity. Neostigmine, Phenytoine, Glycine, Dopa and 5-Hydroxy-Tryptophan had no effect. Passive shortening or stretching of the m. biceps brachii as well as touching the skin increased motor activity which spread to other segments and to the contralateral side. The H/M ratio was increased but the silent period was normal. A combination of Diazepam and Dipropylacetate or Clonazepam was therapeutically effective in the cases reported. A central genesis, of the pathogenetic mechanisms discussed, is the most probable in our cases.