REVIEW OF 23 PATIENTS AFFECTED BY THE STIFF MAN SYNDROME - CLINICAL SUBDIVISION INTO STIFF TRUNK (MAN) SYNDROME, STIFF LIMB SYNDROME, AND PROGRESSIVE ENCEPHALOMYELITIS WITH RIGIDITY

Objective-To investigate whether the stiff limb syndrome may be separa ted from the stiff man syndrome and progressive encephalomyelitis with rigidity on simple clinical grounds, and whether such a distinction h as implications for aetiology, treatment, and prognosis. Methods-Twent y three patients referred over a 10 year period with rigidity and spas ms in association with continuous motor unit activity, but without evi dence of neuromyotonia, extrapyramidal or pyramidal dysfunction or foc al lesions of the spinal cord were reviewed. The patients were divided into those with an acute or subacute illness, leading to death within 1 year, and those with a chronic course. The latter were divided into those in whom rigidity and spasms dominated in the axial muscles, or in one or more distal limbs, at the time of their first assessment. Re sults-This simple division identified three distinct groups of patient s. (1) Progressive encephalomyelitis with rigidity: two patients had a rapidly progressive condition characterised by widespread rigidity wh ich resulted in death within 6 and 16 weeks. One patient had negative anti-GAD and anti-neuronal antibodies, but had markedly abnormal CSF a nd widespread denervation. The principal pathological findings in this case were a subacute encephalomyelitis which primarily affected the g rey matter. In the remaining patient anti-GAD antibodies were not test ed, and postmortem was refused. (2) Stiff man syndrome: eight patients had rigidity and painful spasms of the lumbar paraspinal, abdominal, and occasionally proximal leg muscles associated with a lumbar hyperlo rdosis. There was no involvement of the upper limbs, distal lower limb s, sphincters or cranial nerves. Seven had anti-GAD antibodies and mos t had additional evidence of autoimmune disease. Neurophysiologically there was continuous motor unit activity with abnormal exteroceptive r eflexes, but a normal interference pattern during spasms. The patients all responded to baclofen/diazepam and remained ambulant. (3) Stiff l imb syndrome: thirteen patients had rigidity, painful spasm, and abnor mal postures of the distal limb, usually the leg. About half went on t o develop sphincter or brainstem involvement. Generalised myoclonic je rks were not a feature. Only two had truncal rigidity, and another two had anti-GAD antibodies. Most had no evidence of autoimmune disease. Neurophysiologically they had continuous motor unit activity in the af fected Limb, abnormal exteroceptive reflexes, and abnormally segmented EMG activity during spasms. The disease ran a protracted course, and most patients had only a partial response to baclofen or diazepam. Abo ut half became wheelchair bound. Conclusions-The stiff limb syndrome s eems distinct from the stiff man syndrome or progressive encephalomyel itis with rigidity, and is an important cause of rigidity and spasm in the setting of continuous motor unit activity.