The stiff-man syndrome: report of a case

Demystifying the spontaneous phenomena of motor hyperexcitability

Possessing a discrete functional repertoire, the anterior horn cell can be in one of two electrophysiological states: on or off. Usually under tight regulatory control by the central nervous system, a hierarchical network of these specialist neurons ensures muscular strength is coordinated, gradated and adaptable. However, spontaneous activation of these cells and their axons can result in abnormal muscular twitching. The muscular twitch is the common building block of several distinct clinical patterns, namely fasciculation, myokymia and neuromyotonia. When attempting to distinguish these entities electromyographically, their unique temporal and morphological profiles must be appreciated. Detection and quantification of burst duration, firing frequency, multiplet patterns and amplitude are informative. A common feature is their persistence during sleep. In this review, we explain the accepted terminology used to describe the spontaneous phenomena of motor hyperexcitability, highlighting potential pitfalls amidst a bemusing and complex collection of overlapping terms. We outline the relevance of these findings within the context of disease, principally amyotrophic lateral sclerosis, Isaacs syndrome and Morvan syndrome. In addition, we highlight the use of high-density surface electromyography, suggesting that more widespread use of this non-invasive technique is likely to provide an enhanced understanding of these motor hyperexcitability syndromes.

Sudden death and paroxysmal autonomic dysfunction in stiff-man syndrome

Two women with typical stiff-man syndrome (SMS) developed increasingly frequent attacks of muscle spasms with severe paroxysmal autonomic dysfunctions such as transient hyperpyrexia, diaphoresis, tachypnea, tachycardia, pupillary dilation, and arterial hypertension. Autoantibodies to GABA-ergic neurons were identified in the serum of both patients and in the cerebrospinal fluid of one. Both died suddenly and unexpectedly. General autopsy did not reveal the cause of death. Neuropathological studies revealed perivascular gliosis in the spinal cord and brain stem of one patient and lymphocytic perivascular infiltration in the spinal cord, brain stem, and basal ganglia of the other. The occurrence of a chronic inflammatory reaction in one of the two patients supports the idea that an autoimmune disease against GABA-ergic neurons may be involved in SMS. A review of the literature indicates that functional impairment in SMS is severe and prognosis is unpredictable because of the potential for sudden and unexpected death. Both muscular abnormalities and autonomic dysfunctions may result from autoimmunity directed against GABA-ergic neurons.

Autoantibodies to glutamic acid decarboxylase in a patient with stiff-man syndrome, epilepsy, and type I diabetes mellitus

Stiff-man syndrome is a rare disorder of the central nervous system consisting of progressive, fluctuating muscle rigidity with painful spasms. It is occasionally associated with endocrine disorders, including insulin-dependent diabetes, and with epilepsy. We investigated the possible existence of autoimmunity against the nervous system in a patient with stiff-man syndrome associated with epilepsy and Type I diabetes mellitus. Levels of IgG, which had an oligoclonal pattern, were elevated in the cerebrospinal fluid. The serum and the cerebrospinal fluid produced an identical, intense staining of all gray-matter regions when used to stain brain sections according to an indirect light-microscopical immunocytochemical procedure. The staining patterns were identical to those produced by antibodies to glutamic acid decarboxylase (the enzyme responsible for the synthesis of gamma-aminobutyric acid). A band comigrating with glutamic acid decarboxylase in sodium dodecyl sulfate-polyacrylamide gels appeared to be the only nervous-tissue antigen recognized by cerebrospinal fluid antibodies, and the predominant antigen recognized by serum antibodies. These findings support the idea that an impairment of neuronal pathways that operate through gamma-aminobutyric acid is involved in the pathogenesis of stiff-man syndrome, and they raise the possibility of an autoimmune pathogenesis.