Stiff-man syndrome is characterized clinically by fluctuating muscular stiffness 
and spasm, and electromyographically by continuous motor unit activity at rest, 
which is abolished by sleep, general anesthesia, nerve block, curare, and 
several centrally-acting medications. A spinal or supraspinal origin has been 
proposed for this disorder. Some clinical and electrophysiologic features, along 
with an occasional association with encephalopathy, may support a proposed 
supraspinal cause. An elderly man with progressive dementia and concomitant 
development of stiff-man syndrome is described. He had not had stiff-man 
syndrome one year earlier, when he had only mild dementia. An association 
between stiff-man syndrome and dementia has not been previously described. 
Increased muscle tone and muscular rigidity is frequently encountered in 
patients with dementia, however, and pathologic reflexes involving neck and 
proximal musculature have been described in dementia. It is possible that this 
patient represents an exaggerated form of such motor disturbances in dementia, 
and that clinical and electromyographic features of stiff-man syndrome may be 
present with increased incidence in patients with dementia.