The trigemino-cervical reflex in patients with trigeminal neuralgia

To investigate the central trigeminal system in idiopathic trigeminal neuralgia (TN).

Short latency responses can be recorded in sternocleidomastoid (SCM) muscles after stimulation of the trigeminal nerve (trigemino-cervical reflex). This brainstem reflex was investigated in 40 healthy subjects and in 17 patients suffering from idiopathic TN before and after therapy for 2 months with carbamazepin.

Before therapy, six patients presented abnormalities of SCM responses on the painful side, six patients with bilateral abnormalities, and five patients with normal responses. A significant variation in the responses after therapy was found only in the patients with unilateral abnormalities: these patients and the patients with normal reflexes before therapy also had a good response to the therapy with significant pain relief.

Our findings suggest that the trigemino-cervical reflex could be useful in the clinical assessment of TN prior to instituting non-surgical treatment. The bilateral location of the abnormalities in some patients seems to point to a centrally located dysfunction; therefore, this study supports the idea that mechanisms in the central nervous system may play an important role in the pathophysiology of trigeminal neuralgic pain.