Diagnostic relevance of trigeminal evoked potentials following infraorbital nerve stimulation.

A new tool in neurophysiological exploration of the trigeminal nerve has recently been introduced. It has been demonstrated that stimulation of the infraorbital nerve trunk gives rise to very reliable scalp responses reflecting the activity of the afferent pathway between the maximally nerve and the brain stem. The authors demonstrate that alterations of such trigeminal evoked responses fit with documented pathological processes at various locations along the trigeminal pathway (maxillary sinus, parasellar region, and within the brain-stem parenchyma). They report the findings in 68 patients suffering from "idiopathic" trigeminal neuralgia. Alterations of the response were detected in 33 cases, suggesting that some damage of the nerve had taken place either at the root entry zone into the pons (23 cases) or slightly distal to it (10 cases). Such results support the hypothesis that trigeminal neuralgia may be due to a compression of the trigeminal root at the pons entry zone.