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Is the Tingling on My Scalp Helping my Headaches? Occipital Nerve Stimulation for Cluster Headaches
Abstract & Commentary
By Dara G. Jamieson, MD, Associate Professor of Clinical Neurology, Weill Medical College. Dr. Jamieson reports no financial relationship relevant to this field of study.
Synopsis: Occipital nerve stimulation appears to decrease the cluster pain and attack frequency in most, but not all, patients with chronic drug-resistant cluster headaches.
Source: Burns B, et al. Lancet Neurology. 2007;6:314-321.
Patients who suffer from cluster headaches report that the pain is so brutal that they are willing to consider any therapy that promises even slight relief from the agony of unilateral periorbital knife-like pain. Options for successful treatment of cluster headaches are limited. Preventative medication to decrease the frequency and severity of the pain is often only minimally effective. The medications used to treat the acute pain may be used excessively or may not be appropriate for cluster patients with vascular risk factors. Surgical procedures that target the trigeminal nerve or cranial parasympathetic outflow tracts have been attempted with variable results and with risk of significant complications. Deep brain stimulation of the hypothalamus, an area of activation in cluster headaches, has been shown to be effective but the potential surgical complications make this treatment inappropriate for all but the most intractable of patients. While some cluster headaches remit for months to years, the patient with chronic cluster headaches, without intervening headache-free periods, is particularly disabled by the unremitting excruciating pain. The patient with chronic cluster headaches may either have had episodic cluster periods with periods of relief or may have always had unrelenting headaches. The patient with chronic cluster headaches is often amenable to any treatment that offers promise of partial pain relief.
These 2 papers, one from Belgium (Magis et al) and one from the United Kingdom (Burns et al) examined the benefit of occipital nerve stimulation in patients with chronic medication-unresponsive cluster headache. Suboccipital injection of steroids or local anesthetics have been of occasional benefit in cluster patients but the effect is transient and repeated injections often lose efficacy. Occipital nerve stimulation has been used in intractable migraine patients and its efficacy in these 2 groups of drug-resistant cluster headache patients was evaluated, even though its mechanism of action is not clear. Peripheral neurostimulation has been beneficial in patients with pain disorders such as neuropathic pain, with possible extrapolation to patients with primary headache disorder. Multiple pain pathways, including cervical, somatic trigeminal, and dural trigeminal vascular afferents, which converge on second-order neurons in the brain stem and on third-order cortical neurons, may be impacted by stimulation of the occipital nerve. The perceived clinical benefit of occipital nerve injection and the appreciation of any relief of pain in patients with cluster headaches served as the impetus for the evaluation of occipital nerve stimulation.
The patient population of the 2 papers was very similar, with 8 patients (one woman and 7 men) of average age in the mid-forties, in each study. All patients had suffered from cluster headaches for years (minimum 7 years) to decades with headache that persisted despite aggressive medical therapy. The stimulation technique differed, as the British patients had bilateral occipital nerve stimulators inserted, whereas the Belgian patients had the stimulator surgically implanted only on the side of the headache. The stimulation parameters were adjusted to obtain paresthesias in the innervation territory of the greater occipital nerve.
The assessment of response differed between the 2 papers but was subjective in both. The patients monitored by Magis et al used headache diaries before and after treatment to assess clinical response. Burns et al used a less quantitative assessment in which the patients were asked to give an overall impression of their response and their use of triptan medications before and after the treatment. They were also asked if they would recommend the treatment to a fellow cluster sufferer. No blinding of treatment was possible since paresthesias indicated that stimulation was occurring. However, frequent technical problems with battery life and electrode migration led to interruption of the stimulation with increase in cluster-attack frequency and severity. The stimulation was also intermittently discontinued in order to monitor response. These interruptions were not blinded as the patients knew when the stimulation was no longer operating because the paresthesias disappeared.
The outcomes reported by both sets of investigators were encouraging. Both studies found that most patients had decreased cluster attack pain and frequency that persisted over months. Magis et al reported that 2 patients were pain free after follow-up of 16 and 22 months. Three patients had 90% reduction in attack frequency and 2 patients had improvement of around 40%. Length of follow-up was variable but was greater than 3 months for all the patients. One patient who had no benefit at 4 months with intolerable paresthesias discontinued treatment. Seven out of 8 patients were able to decrease medication use. These patients all had unilateral stimulation on the side of the headaches.
Burns et al followed their 8 patients for a range of 6-27 months of bilateral stimulation. Two patients had marked improvement and would recommend treatment. Three patients had only moderate improvement but would still recommend treatment. One patient had only mild improvement and would not recommend treatment. The benefit accrued over weeks but appeared relatively durable.
Both groups of patients had frequent technical malfunctions requiring surgical replacement of batteries and electrodes. However, unlike other surgical treatments, specifically deep brain stimulation of the hypothalamus, there were no serious complications of treatment. Patients were selected based on the refractoriness of the headaches, and the pre-implantation response to occipital nerve block did not seem to predict the outcome of successful occipital nerve stimulation.
Patients with drug-resistant chronic cluster headaches have an existence dominated by unpredictable, unrelenting pain, and are desperate for any treatment that offers a modicum of relief. The patients in these studies were taking large quantities of medications with minimal benefit and were willing to undergo multiple surgical procedures to obtain benefit. The results are encouraging, even if the pathophysiological mechanism to explain it is elusive. The technique appears to be safe with only frustrating technical glitches. The lack of blinding was, probably, only of minimal consequence given the refractoriness of the pain. The similar result with either unilateral or bilateral stimulation is curious and needs further study. The results with unilateral stimulation are encouraging enough to indicate that the treatment should be unilateral, at least initially, in the appropriate patient with unilateral symptoms. These 2 papers give hope to a group of patients who are despondent and frustrated. For the appropriate patient who understands the uncertainty of the individual response, occipital nerve stimulation can offer hope of an existence with decreased pain.