The trigemino-cervical reflex in tension-type headache

To investigate the pathophysiology of tension-type headache (TTH) with special reference to central mechanisms and to the involvement of the trigeminal system. Short latency responses can be recorded in tonically active sternocleidomastoid muscle after stimulation of the infraorbital branch of the trigeminal nerve (the trigemino-cervical reflex). This brainstem reflex was studied in 15 healthy subjects, in 15 patients with episodic tension-type headache (ETTH) and in 15 patients with chronic tension-type headache (CTTH) outside of the pain attacks. The trigemino-cervical response was abnormal, in the size or latency, in 13 patients with CTTH and in only one patient with ETTH. This finding strongly suggests that only in the CTTH the underlying pathophysiology involves the trigeminal system. The trigemino-cervical reflex is a sensitive method to evaluate the involvement of the trigeminal brainstem neurones in TTH and their assessment may provide useful diagnostic and prognostic information.