Critical review of gangliosides and thyrotropin-releasing hormone in peripheral neuromuscular diseases. The lack of effective therapy for many of the chronic neuromuscular diseases such as amyotrophic lateral sclerosis, hereditary motor sensory neuropathy (Charcot-Marie-Tooth disease), spinocerebellar degenerations and idiopathic polyneuropathy has led to a search for substances that may stimulate peripheral nerve regeneration. Two such agents that have been proposed are gangliosides (mixed purified bovine brain gangliosides, Cronassial) and thyrotropin releasing factor (TRH). Studies on both of these agents were initially reported with enthusiasm to be successful, but later double-blind controlled studies have failed to confirm these findings. This review provides critical analysis of the designs of studies of potentially effective agents in chronic neuromuscular diseases, and emphasizes the power of the placebo response, and the importance of designing placebos which are indistinguishable from the trial medication other than in the active effect. 