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Trigeminal event-related potentials in patients with olfactory dysfunction.

OBJECTIVE
There are mutual interactions between the olfactory and trigeminal systems. The purpose of this study was (1) to assess trigeminal sensitivity using chemosensory event-related potentials (CSERPs) in patients with olfactory dysfunction and (2) to evaluate whether trigeminal ERPs were different with regard to the presence or absence of olfactory ERPs.


MATERIALS AND METHODS
Prospective study of 60 patients who presented with olfactory dysfunction (postinfectious olfactory loss: n = 19, posttraumatic olfactory loss: n = 28, and olfactory loss due to idiopathic, or toxic causes: n = 13). All patients were extensively evaluated with an orthonasal olfactory test based on the "Sniffin' Sticks". In addition, chemosensory ERPs were recorded in response to olfactory and trigeminal stimulation.


RESULTS
Olfactory/trigeminal ERPs were recorded in 25/60 patients, respectively. Patients with no detectable olfactory ERPs, considered as severely affected, demonstrated an altered trigeminal sensitivity as indicated by an increase in P2 latencies and a decrease in both, P2 and N1-P2 amplitudes compared to patients with detectable olfactory ERPs. A regression analysis showed a negative relation between P2 latencies and the "Sniffin' Sticks"score (r = -0.46, p < 0.001).


CONCLUSIONS
Patients with severe olfactory dysfunction demonstrated decreased trigeminal sensitivity as indicated by electrophysiological measures. This study supports the idea of interactions between the chemical senses. Whether altered responses to trigeminal stimulation may be used as a prognostic measure related to recovery from olfactory loss remains to be demonstrated.