stiff-man syndrome

[stĭfmăn′]
n.
  1. A chronic, progressive but variable disorder of the central nervous system having no known cause and associated with fluctuating muscle spasms and stiffness.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.