[A stiff-legged man with a bizarre gait].

BACKGROUND

Stiff person syndrome (SPS) is a rare neurological disorder characterized by simultaneous contraction of agonistic and antagonistic muscles. SPS can easily be confused with a psychogenic movement disorder, but the frequent finding of autoantibodies against glutamic acid decarboxylase (GAD65), positive response to immunomodulatory treatment and association with other autoimmune diseases strongly suggests an immununological pathogenesis.

CASE REPORT: A 43-year-old man was admitted with a three-year history of stiffness and painful spasms in the left leg, causing walking problems and frequent falls. A clinical examination revealed a bizarre gait, pes equinovarus, and simultaneous contraction of agonistic and antagonistic muscles, but no other neurological deficits. Electromyography was normal except for simultaneous contraction of agonistic and antagonistic muscles. Magnetic resonance imaging of the neuraxis and routine examinations of blood and cerebrospinal fluid were normal. A diagnosis of conversion neurosis was considered, but was not supported by positive evidence. The symptoms gradually evolved to affect the back and both legs. Elevated levels of antibodies against GAD65 in serum and cerebrospinal fluid confirmed the diagnosis SPS three and a half years after symptom debut. Both stiffness and muscle cramps responded excellently to diazepam.

CONCLUSION

This report calls attention to a rare neurological disease, in which absence of specific neurological deficits may lead to an erroneous diagnosis of a psychogenic disorder.