The stiff-person syndrome (SPS) is a rare neurologic disorder of uncertain cause, characterized by severe and incapacitating axial and proximal limb rigidity due to continuous motor unit activity. Rigidity is often enhanced by anxiety, sudden movements, or external stimuli causing intermittent painful muscle spasms, often leading to skeletal deformity. Variants of this disorder include focal involvement of one limb (“stiff-limb syndrome”), or additional neurological symptoms suggestive of involvement of subcortical gray matter (“progressive encephalomyelitis with rigidity and myoclonus”) (PEWR) and occasionally secondary to malignant disease (paraneoplastic SPS). Antineuronal antibodies often associated with other autoimmune diseases are characteristic features of this disorder. The disease follows a progressive, unremitting course, resulting in pronounced disability, if left untreated.
Since the publication of the previous edition of this book, several advances have been made in the understanding of the immunobiology and pathogenesis of SPS and PEWR; a better delineation of the clinical features and boundaries of these disorders; as well as establishing clear guidelines for its treatment. Newer therapeutic options have also been added.
This unusual syndrome was first described by Moersch and Woltman in 1956.1 The authors coined the term “stiff-man syndrome” in reporting 14 patients with clinical features of progressive fluctuating muscular rigidity and spasms. Their first case, a 49-year-old man, initially complained of a feeling of tightness of the neck musculature of variable occurrence. Over a period of 4 years, this disorder progressively affected the muscles of the shoulder, back, abdomen, and thighs, causing the muscles to appear stiff and “board-like.” Continuous muscle contraction causing pronounced stiffness of the axial and limb muscles forced the patient to walk in a peculiar way that was both slow and awkward. Voluntary movement or passive displacement of the limbs triggered prolonged and painful muscle spasms. If severe enough, the spasms caused postural instability and falls. In the words of the authors, the patient would fall like a “wooden man.” The additional 13 patients in the original report were similar in all respects.
The clinical features of this previously unreported condition were described in detail in Moersch and Woltman's paper. No other signs of central or peripheral nervous system involvement were present in their 14 patients. The only additional clinical abnormality found in 4 of the 14 original patients was diabetes mellitus. Five of their 14 patients underwent electromyographic (EMG) studies, revealing motor unit activity resembling “that which accompanies contraction of voluntary muscle.” In their 1967 review on the subject, Gordon and colleagues2 summarized the EMG findings reported in the literature until then as “one of persistent tonic contraction reflected in constant firing even at rest.” No attempt at relaxation could alter the continuous motor unit discharges according to these authors. Their observations provided the electrophysiological substrate of muscle stiffness in these patients.
Since the publication of Moersch and Woltman's description of the syndrome, more than 100 cases have been reported from different regions of the world.