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Antinociceptive reflex
alteration in acute posttraumatic headache following whiplash
injury.
Keidel M, Rieschke P, Stude P, Eisentraut R, van Schayck R,
Diener H.
Department of Neurology, University of Essen, Hufelandstrasse 55,
D-45122, Essen, Germany. keidel@uni-essen.de
Brainstem-mediated antinociceptive inhibitory reflexes of the
temporalis muscle were investigated in 82 patients (47 F, 35 M, mean
age 28.3 years, SD 9.4) with acute posttraumatic headache (PH)
following whiplash injury but without neurological deficits, bone
injury of the cervical spine or a combined direct head trauma on
average 5 days after the acceleration trauma. Latencies and
durations of the early and late exteroceptive suppression (ES1 and
ES2) and the interposed EMG burst (IE) of the EMG of the voluntarily
contracted right temporalis muscle evoked by ipsilateral stimulation
of the second and third branches of the trigeminal nerve were
analyzed and compared to a cohort of 82 normal subjects (43 F, 39 M,
mean age 27.7 years, SD 7.1). Highly significant reflex alterations
were found in patients with PH with a shortening of ES2 duration
with delayed onset and premature ending as the primary parameter of
this study, a moderate prolongation of ES1 and IE duration and a
delayed onset of IE. The latency of ES1 was not significantly
changed. These findings indicate that acute PH in whiplash injury is
accompanied by abnormal antinociceptive brainstem reflexes. We
conclude that the abnormality of the trigeminal inhibitory
temporalis reflex is based on a transient dysfunction of the
brainstem-mediated reflex circuit mainly of the late polysynaptic
pathways. The reflex abnormalities are considered as a
neurophysiological correlate of the posttraumatic (cervico)-cephalic
pain syndrome. They point to an altered central pain control in
acute PH due to whiplash injury.
PMID: 11376904 [PubMed - indexed for MEDLINE]
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