Deep Brain Stimulation in Trigeminal Autonomic Cephalalgias

Abstract

Cluster headache (CH), paroxysmal hemicrania (PH), and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT syndrome) are primary headaches grouped together as trigeminal autonomic cephalalgias (TACs). All are characterized by short-lived unilateral head pain attacks associated with oculofacial autonomic phenomena. Neuroimaging studies have demonstrated that the posterior hypothalamus is activated during attacks, implicating hypothalamic hyperactivity in TAC pathophysiology and suggesting stimulation of the ipsilateral posterior hypothalamus as a means of preventing intractable CH. After almost 10 years of experience, hypothalamic stimulation has proved successful in preventing pain attacks in approximately 60% of the 58 documented chronic drug-resistant CH patients implanted at various centers. Positive results have also been reported in drug-resistant SUNCT and PH. Microrecording studies on hypothalamic neurons are increasingly being performed and promise to make it possible to more precisely identify the target site. The implantation procedure has generally proved safe, although it carries a small risk of brain hemorrhage. Long-term stimulation is proving to be safe: studies on patients under continuous hypothalamic stimulation have identified nonsymptomatic impairment of orthostatic adaptation as the only noteworthy change. Studies on pain threshold in chronically stimulated patients show increased threshold for cold pain in the distribution of the first trigeminal branch ipsilateral to stimulation. When the stimulator is switched off, changes in sensory and pain thresholds do not occur immediately, indicating that long-term hypothalamic stimulation is necessary to produce sensory and nociceptive changes, as also indicated by clinical experience that CH attacks are brought under control only after weeks of stimulation. Infection, transient loss of consciousness, and micturition syncope have been reported, but treatment interruption usually is not required.