Hypothalamic deep-brain stimulation: target and potential mechanism for the treatment of cluster headache

Recently, functional imaging data have underscored the crucial role of the hypothalamus in trigemino-autonomic headaches, a group of severe primary headaches. This prompted the application of hypothalamic deep-brain stimulation (DBS), with the intention to preventing cluster headache (CH) attacks in selected severe therapy-refractory cases. To date, a total of 50 operated intractable CH patients, one patient with short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing and three with atypical facial pain, have been reported. However, it is not apparent why the spontaneous bursts of activation in the inferior posterior hypothalamus result in excruciating head pain, whereas continuous electrical stimulation of the identical area is able to prevent these attacks. Recently, this issue has been addressed by examining 10 operated chronic CH patients, using H(2)(15)O-positron emission tomography and alternately switching the hypothalamic stimulator on and off. The stimulation-induced activation in the ipsilateral posterior inferior hypothalamic grey (the site of the stimulator tip) as well as activation and de-activation in several cerebral structures belonging to neuronal circuits usually activated in pain transmission. These data argue against an unspecific antinociceptive effect or pure inhibition of hypothalamic activity as the mode of action of hypothalamic DBS and suggest functional modulation of the pain-processing network.