Trigeminal evoked potentials in cluster headache

We sought out alterations of early trigeminal evoked potenials (TEPs) in patients suffering from episodic cluster headache, in order to evaluate a possible direct involvement of the trigeminal nerve. The study was carried out at the Centre for Pain Relief, National Institute for Cancer Research, Genoa in collaboration with the Interuniversity Centre for Pain Neurophysiology, unit of the University of Genoa. We studied 32 patients suffering from episodic cluster headache. TEPs were recorded from the scalp, after stimulation of the infraorbital nerve on both sides. The recordings were performed during the patients' bouts, but outside attacks in 24 cases. In 8 patients the recordings were performed during attacks. All 8 patients tested during an attack showed a delayed or absent W2 and W3 of the TEP, while only 3 of the 24 patients tested outside the attack had delayed W2 and W3. The alterations detected point towards a temporary impairment of conduction along the nerve fibres, approximately at the gasserian ganglion. Such a situation is consistent with a moderate compression by a swollen internal carotid artery or cavernous sinus upon the ganglion, during the attack.