Lucien M. Levy, MD, PhD; Marinos C. Dalakas, MD; Mary Kay Floeter, MD, PhD
Impairment of intracortical inhibitory neurons causes corticospinal neurons in the motor cortex to discharge heavily to the α motor neurons. The increased excitation to the spinal cord causes excessive firing by α motoneurons ( ). The loss of spinal inhibitory circuits, represented by two inhibitory motor neurons (illustrated with solid dots in center), enhances the motoneuron hyperexcitability and may increase discharges from γ motor neurons to the muscle spindles ( ). Excessive responses to afferent impulses from muscle spindles ( ) and skin afferents ( ), caused by impaired inhibitory interneurons, may explain the increased stiffness after sudden tactile stimuli.
Intense and specific staining of the Purkinje cells and γ-aminobutyric acidergic synapses can be seen.
Placement of selected regions of interest in motor cortex. Placement of selected regions of interest in posterior occipital cortex. Additional regions of interest in the putamen. Average γ-aminobutyric acid ( ) levels (expressed as ratios to creatine), obtained by magnetic resonance spectroscopy in unaffected persons, are displayed by using a color scale.
The signal profile represents the magnitude of the metabolite peaks occurring in a two-dimensional J-resolved spectrum along the J = 0 axis, where J is the decoupling dimension variable. Decoupling of peaks by introduction of a second dimension improves separation and identification of metabolite peaks. GABA = γ-aminobutyric acid; NAA = -acetylaspartate.
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Levy LM, Dalakas MC, Floeter MK. The Stiff-Person Syndrome: An Autoimmune Disorder Affecting Neurotransmission of γ-Aminobutyric Acid. Ann Intern Med. 1999;131:522-530. doi: 10.7326/0003-4819-131-7-199910050-00008
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Published: Ann Intern Med. 1999;131(7):522-530.
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