Electrophysiological testing of the trigeminofacial system: aid in the diagnosis of atypical facial pain

The aim of this study was to evaluate the yield of objective electrophysiol ogical testing of the trigeminofacial system in atypical facial pain (AFP). In addition to the clinical neurological examination, two brainstem reflex es covering both the peripheral parts and the central connections of the tr igeminal and the facial nerves, the blink and jaw reflexes (BR and JR), wer e recorded in 17 AFP patients. The control group consisted of 18 healthy vo lunteers with no history of facial pain or chronic headache. The AFP patien ts could be divided into three distinct groups on the basis of the clinical and electrophysiological findings. (1) Major trigeminal neuropathy. Four p atients had clinical and electrophysiological signs of trigeminal neuropath y (three patients with an afferent pattern of abnormal BR, and one with abs ent JR on the clinically affected side) despite normal findings in the MRI- scans of the brain. Thus, electrophysiological testing may be more sensitiv e than MRI in demonstrating pathology in some of the AFP patients. (2) Mino r trigeminal neuropathy. Seven patients had signs of increased excitability of the BR in the form of uni- or bilaterally abnormal (diminished or absen t) habituation of the R2 component of the BR; two of these patients also sh owed clinical signs of trigeminal dysfunction, but the MRI-scans were all n ormal. This deficient habituation of the BR indicates increased excitabilit y of the BR at brainstem level in nearly 50% of our AFP patients, (3) 'Idio pathic', no signs of trigeminal neuropathy, Five patients had normal findin gs both in the brainstem reflex recordings and in the clinical examinations . Additionally, one patient had abnormal BAEP and EEG recordings. On the gr oup level, the AFP patients had significantly higher thresholds of the tact ile R1 component of the BR than the control subjects. Electrophysiological testing may offer a valuable tool for both the clinical evaluation, and the scientific study of AFP. (C) 1999 International Association for the Study of Pain. Published by Elsevier Science B.V.