Physiologic studies of spinal inhibitory circuits in patients with stiff-person syndrome.
OBJECTIVE
To test inhibitory spinal circuits in patients with stiff-person syndrome (SPS).


BACKGROUND
Patients with SPS have fluctuating muscle stiffness and spasms, and most have antibodies against GABAergic neurons. We predicted they would also have abnormalities of spinal GABAergic circuits.


METHODS
Physiologic methods using H-reflexes were used to test reciprocal inhibition in the forearm and thigh, vibration-induced inhibition of flexor carpi radialis and soleus H-reflexes, recurrent inhibition, and nonreciprocal (1b) inhibition of soleus H-reflexes.


RESULTS
Vibration-induced inhibition of H-reflexes was diminished in eight of nine patients tested, but the presynaptic period of reciprocal inhibition was normal in most patients. Both circuits are presumed to involve presynaptic inhibition and GABAergic interneurons. Presumed glycinergic circuits, including the first period of reciprocal inhibition and nonreciprocal (1b) inhibition, showed occasional abnormalities. Recurrent inhibition was normal in all five patients tested.


CONCLUSIONS
Differences between the two presumptive GABAergic circuits may indicate that not all populations of GABAergic neurons are uniformly affected in SPS. The involvement of presumptive glycinergic circuits in some patients could point to impairment of nonGABAergic neurons, unrecognized involvement of GABAergic neurons in these inhibitory circuits, or, more likely, alterations of supraspinal systems that exert descending control over spinal circuits.
National Institutes of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD 20892-1404, USA.
M K
MK
Floeter
J
J
Valls-Solé
C
C
Toro
D
D
Jacobowitz
M
M
Hallett
D000328:Adult; D000368:Aged; D004576:Electromyography; D005267:Femoral Nerve / Q000166:cytology / Q000502:physiology; D005998:Glycine / Q000502:physiology; D006181:H-Reflex / Q000502:physiology*; D006801:Humans; D007395:Interneurons / Q000737:chemistry / Q000502:physiology; D008475:Median Nerve / Q000166:cytology / Q000502:physiology; D008875:Middle Aged; D009046:Motor Neurons / Q000737:chemistry / Q000502:physiology; D018482:Muscle, Skeletal / Q000294:innervation; D009433:Neural Inhibition / Q000502:physiology*; D010812:Physical Stimulation; D013116:Spinal Cord / Q000737:chemistry / Q000166:cytology / Q000503:physiopathology*; D016750:Stiff-Person Syndrome / Q000503:physiopathology*; D013710:Tendons / Q000502:physiology; D014732:Vibration; D005680:gamma-Aminobutyric Acid / Q000502:physiology
D005680:gamma-Aminobutyric Acid; D005998:Glycine