Idiopathic trigeminal pain associated with gustatory stimuli

We present a unique case of a patient with facial pain evoked by gustatory stimuli. Pain was typically evoked by application of sucrose to the ipsilateral anterior 2/3 of the tongue, but not to the contralateral aspect. Pain was referred to the maxillary tuberosity area and, when stronger, to the infraorbital and supraorbital regions. Sucrose was most effective in eliciting pain, whilst saline, citric acid and water had a minimal effect. Spatial or temporal summation of gustatory stimuli was associated with stronger pain of longer duration and shorter latency. Some of the pain characteristics were similar to those of idiopathic trigeminal neuralgia. Thus, pain was elicited by innocuous ipsilateral stimuli, referred out of the stimulus zone, persisted beyond the period of stimulation and could be controlled with carbamazepine. We proposed a central neural mechanism for pain induction with convergence between gustatory stimuli afferents and pain pathways in the trigeminal system.