Neurologists at the Mayo Clinic, Rochester, MN extended their reports of patients with stiff-man syndrome (SMS), first reported there by Drs Moersch and Woltman in 1956. They describe the characteristics of a large cohort of 99 patients (67 female), their treatment and outcome. Median age at symptom onset was 40 years (range 5-70 years); 5 presented before 18 years of age. Mean follow-up from symptom onset was 5 years (range 0-23 years). Phenotypic symptoms included low back stiffness and spasms in all of 59 classic cases, exaggerated lumbar lordosis in 52, lower extremity stiffness and spasms in 59, neck stiffness and spasms in 10, upper extremity stiffness and spasms in 4, abdominal wall stiffness and spasms in 26, respiratory symptoms with spasms in 6, and falls in 30. Symptoms were exacerbated by emotional stress, startle, cold, and movement. Seventy-nine were GAD65 antibody seropositive, and 53 (67%) had at least one coexisting autoimmune disease; 3 (4%) had cancer. GAD65 antibody values were significantly higher in patients with classic SMA than in those with partial or variant SMA. Treatment with diazepam (40 mg/day) provided sustained improvements. Immunotherapy gave additional improvements. Sixteen (64%) of 23 patients with extended follow-up remained ambulatory. [1]

COMMENT. Stiff-man syndrome occurs mainly in adults but can occur in children. Diagnosis may be confirmed with EMG documentation of hyperexcitability of spinal motor neurons, GAD65 antibodies, and response to diazepam, first described by Howard FM Jr. [2]

Several reports of stiff-child syndrome are uncovered by a PubMed search. The disorder must be distinguished from hyperexplexia or hereditary stiff-baby syndrome, an autosomal dominant disorder. The EMG shows persistent hyperexcitability at rest, abolished by diazepam. The hypertonia lessens during sleep and increases with the slightest startle or tactile stimulus. Nose tapping will elicit the hyperexplexic startle response in affected newborns (Ped Neur Briefs May 1991). [3]