The stiff baby syndrome and its diagnostic distinction from epilepsy is reviewed from the Service de Neuronatologie, Pavillon de la Mere et l’Enfant, Nantes, France. The disease hyperexplexia was first described in 1962 by Kok and Bruyn in 29 members of one family and occurred as a dominant autosomal transmission. It was distinguished by a permanent hypertonia that is heightened by the slightest stimulus. The hypertonia was noted at birth and became less pronounced during the first year of life but later could lead to repeated falls. The electromyogram showed persistent activity even at rest and the activity was abolished by diazepam. Lingam S, Wilson J, and Hart E named the condition “hereditary stiff baby syndrome” . The child has a fixed stare and an expression of anxiety. The hypertonia diminishes during sleep and increases with the slightest psychic or tactile stimulus. Attacks of hypertonia may involve respiratory muscles and lead to apneas which can endanger the child’s life. Digestive disorders including vomiting are usually associated with a hiatal hernia. The electroencephalogram is normal. 
COMMENT. In addition to myoclonic epilepsy, the differential diagnosis includes the stiff man syndrome which is not hereditary but which may occur in children (Millichap JG,unpublished observation), the Isaacs-Mertens syndrome with distal hypertonia and fasciculations, the jumping Frenchmen of Maine syndrome with violent starts induced by slight stimuli and associated with echolalia and echopraxia, and Gilles de la Tourette syndrome. The pathology of stiff man syndrome has been localized to the spinal interneurons but the mechanism of hyperexplexia is controversial. Treatment with diazepam is effective.