Auditory startle reaction is disinhibited in idiopathic restless legs syndrome.
OBJECTIVE
Because the auditory startle reaction is abnormal in disorders with substantia nigra pathology, we hypothesized that auditory startle responses (ASRs) might also be altered in restless legs syndrome (RLS).


METHODS
Neurophysiologic study of the auditory startle reaction.


METHODS
Neurology departments of a university hospital and an affiliated local hospital.


METHODS
Fifteen patients with idiopathic RLS (6 de novo, 9 untreated after a 7-day wash-out period of levodopa, mean duration of RLS [corrected] symptoms 21.2 +/- 17.9 years, mean IRLS [corrected] severity score 23.5 +/- 6.7) and 15 sex- and age-matched healthy controls were investigated.


METHODS
Not applicable.


RESULTS
ASRs were elicited by 8 high-intensity auditory stimuli differing randomly in tonal frequency and intensity. Reflex electromyographic activity was simultaneously recorded with surface electrodes from 8 facial, neck, arm, and leg muscles. In RLS patients, ASRs were significantly more frequent (541 of 960 possible responses; controls, 430 of 960), and ASR area under the curve was significantly larger (3812 +/- 450 microVms; controls, 1756 +/- 226 microVms). Analysis per body region revealed that ASRs were significantly more frequent in RLS patients than in controls in leg muscles (138/360 vs 55/360); ASR latencies to leg muscles were significantly shorter in RLS patients (129 +/- 6 ms vs 160 +/- 11 ms); ASR area under the curve was significantly larger in RLS patients in facial (7547 +/- 1326 mmicroVms vs 2982 +/- 448 microVms) and leg muscles (1373 +/- 308 microVms vs 541 +/- 193 microVms).


CONCLUSIONS
Our data demonstrate disinhibition of reticulospinal pathways in RLS patients as compared to normal controls, likely originating from dysfunction rostral to the lower brainstem.
Frauscher
Birgit
B
Department of Neurology, Innsbruck Medical University, Innsbruck, Austria.
Löscher
Wolfgang
W
Löscher
Wolfgang N
WN
Högl
Birgit
B
Poewe
Werner
W
Kofler
Markus
M
D000161:Acoustic Stimulation; D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001933:Brain Stem / Q000503:physiopathology; D004576:Electromyography; D005072:Evoked Potentials, Auditory / Q000502:physiology; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D009433:Neural Inhibition / Q000502:physiology*; D013216:Reflex, Startle / Q000502:physiology*; D012148:Restless Legs Syndrome / Q000503:physiopathology*; D013378:Substantia Nigra / Q000503:physiopathology