Drug-resistant primary headache patients undergoing surgical therapies: how should we assess outcomes?

The introduction of neurostimulation procedures for chronic drug-resistant primary headaches has offered new hope to patients, but has also introduced new problems. The methods to be used in assessing clinical outcomes and monitoring treatment efficacy need careful attention. The International Headache Society guidelines recommend that treatment efficacy should be monitored by getting patients to report the number of attacks per day, in a headache diary. The headache diary is a fundamental instrument for objectively assessing subjective pain in terms of headache frequency, intensity and duration and analgesic consumption. The huge discrepancy sometimes reported between patient satisfaction and headache improvement suggests that patient satisfaction should not be a primary efficacy endpoint, and more importantly should not be put forward as an argument in establishing the efficacy of highly experimental neurostimulation procedures.

Cluster headache: pharmacological treatment and neurostimulation.

Cluster headache is a primary headache syndrome that is characterized by excruciatingly severe, strictly unilateral attacks of orbital, supraorbital or temporal pain, which last 15-180 min and are accompanied by ipsilateral autonomic manifestations (e.g. lacrimation and rhinorrhea). The attacks typically occur with circadian rhythmicity, being experienced at fixed hours of the day or night. In episodic cluster headache, attacks usually occur daily in 6-12-week bouts (cluster periods) followed by remission periods. In chronic cluster headache there is no notable remission. Cluster headache attacks reach full intensity very quickly and abortive agents need to be administered without delay. The pathophysiology of cluster headache is imperfectly understood and treatment has so far been mainly empirical. However, neuroimaging studies have prompted the successful use of hypothalamic stimulation to treat the condition. More recently, the less invasive technique of occipital nerve stimulation has shown promise in drug-refractory chronic cluster headache. This Review discusses both acute and preventive treatments for cluster headache and includes suggestions of how to use the available medications. The rationale, study results and selection criteria for neurostimulation procedures are also summarized, as are the disadvantages of these procedures.

Long-term experience of neuromodulation in TACs.

Improvement in the biomedical and biotechnological research fields have allowed refinement of the neuromodulation approach in the treatment of a subgroup of medical disorders otherwise refractory to pharmacological treatment, such as chronic primary headaches. Chronic pain conditions imply central sensitisations and functional reorganisation that cannot be quickly or easily reversed. It appears evident that conventional treatment can sometimes be unsuccessful or only partially successful, and that relapse is common. Cluster headache (CH) is the most frequent trigeminal autonomic cephalalgia (TAC) and the most representative of this spectrum of disorders characterised by the association of headache and loco-regional signs and symptoms of facial parasympathetic activation. The striking features of circadian rhythmicity of attacks and circannual periodicity of cluster period, together with the neuroendocrine abnormalities, are suggestive of a neurochronobiological disorder with a central-diencephalic pathogenetic involvement, confirmed by direct evidence in functional neuroimaging studies of ipsilateral posterior hypothalamic activation during cluster attack. In 2000 these findings prompted a functional neurosurgery approach, with the first case of deep brain hypothalamic stimulation (DBS) in a severely disabled chronic CH patient. Since then, 18 implants in our centre and many others in different countries have been performed. Although the outcomes are encouraging, the invasive nature of the technique and the occurrence of rare but major adverse events have suggested a safer peripheral approach with occipital nerve stimulation (ONS).

Therapeutic neurostimulation in chronic headaches: problems of patient selection.

Chronic daily headache that does not respond or no longer responds to prophylaxis is commonly encountered at specialist headache centres. Animal and brain imaging studies indicate that peripheral neurostimulation affects brain areas involved in pain modulation, providing a rationale for its use in these conditions. We examine problems related to the selection of chronic daily headache patients for peripheral neurostimulation. These conditions are often associated with analgesic (including opioid) overuse, and psychiatric or other comorbidities, and the terms used to describe them (chronic migraine, transformed migraine, chronic daily headache and chronic tension-type headache) are insufficiently informative about these patients when proposed for neurostimulation. Longitudinal studies indicate that pre-existing subclinical depressive and anxious states play a key role in chronicisation and that the probability of responding to treatment is inversely related to headache frequency. These considerations suggest the need for extensive characterisation of patients proposed for neurostimulation. We propose that patients being considered for neurostimulation should be followed for at least a year, and that their headache over this time should consistently be frequent (all or most days) and drug refractory. We also propose that only completely drug-resistant (as opposed to partially drug-resistant) patients be considered for neurostimulation unless there are other indications.