Neuromodulatory Approaches to the Management of Medically Refractory Cluster Headache

Abstract

Cluster headache (CH) is, by neurological standards, a relatively common condition that affects about one in 1,000 people, 1 although compared with other more common primary headaches such as migraine 2 it remains rare in practice. CH has been defined in the second edition of the International Classification of Headache Disorders 3 as involving recurrent attacks of severe pain on one side of the head for between 15 and 180 minutes, associated with cranial autonomic features such as lacrimation, conjunctival injection, nasal congestion or rhinnorhoea (see Table 1). This condition can be divided into episodic (ECH) and chronic (CCH) forms. A diagnosis of ECH requires at least two cluster periods lasting from seven days to one year separated by painfree periods lasting one month or longer, while a diagnosis of CCH requires attacks to occur for more than one year without remission or with remission lasting less than one month. CCH affects about 10% of CH patients. General aspects of therapy of the disorder are covered elsewhere. 4,5 While it is not directly germane to neuromodulatiuon approaches, an understanding of the broad issues in medical treatment serves as a useful backdrop against which to discuss newer approaches. CH is one of the trigeminal autonomic cephalalgias, 6 and their therapies are usefully considered to be background 7 as they also can be considered for these newer approaches. Who Is Suitable for Neuromodulation Approaches?It seems reasonable to suggest that neuromodulation approaches to the management of CH be employed in patients with medically intractable forms of the condition. While this is currently true, it reflects the relatively primitive state of current interventions. One should observe that as devices become less invasive, the threshold for their use will become lower. For the moment there is a proposed working definition of medically intractable CH. 8 The essential components are disabling headache that fails at least four preventative drugs, including two from the first three of verapamil, lithium, methysergide, melatonin, topiramate and gabapentin (see Table 2). These considerations are particular to CH and, naturally, generic considerations related to requirements for the devices -such as fitness for anesthesia -are part of the overall assessment of patient suitability. What Approaches Have Been Tried?In essence, two classes of neuromodulation have been explored in CH:peripheral and central. Prior to moving to stimulation approaches, the dreadful pain and disability of medically intractable CH lead to a number of destructive procedures. In principle, these seem unlikely to work if one considers CH as fundamentally being a brain condition. Moreover, they may cause both mortality and significant morbidity, and can induce further pain problems such as anaesthesia dolorosa. Neuromodulatory Approaches to the Management of Medically Refractory Cluster Headache AbstractThe trigeminal autonomic cephalalgias are a group of primary headache disorders characterised by unilateral trigeminal d...