PET and MRA findings in cluster headache and MRA in experimental pain

[Etiology and diagnostics of headaches and facial pain from the neurological point of view]

Headaches are one of the most frequent outpatient complaints. Patients may describe a symptom indicating an underlying disease, which can range from an ordinary indisposition to a medical emergency. Despite these secondary headaches, there exist idiopathic forms, such as migraine and tension type headaches, which represent the most common types. In order to develop a specific treatment, the diagnosis of headaches and the knowledge of their etiology are very important for physicians. While headaches remain a neurological domain, facial pain syndromes are often seen and treated in other medical fields. Here clinically important facial pain syndromes are reported from a neurological point of view.

Connectivity of an effective hypothalamic surgical target for cluster headache

The purpose of this study was to look at the connectivity of the posterior inferior hypothalamus in a patient implanted with a deep brain stimulating electrode using probabilistic tractography in conjunction with postoperative MRI scans. In a patient with chronic cluster headache we implanted a deep brain stimulating electrode into the ipsilateral postero-medial hypothalamus to successfully control his pain. To explore the connectivity, we used the surgical target from the postoperative MRI scan as a seed for probabilistic tractography, which was then linked to diffusion weighted imaging data acquired in a group of healthy control subjects. We found highly consistent connections with the reticular nucleus and cerebellum. In some subjects, connections were also seen with the parietal cortices, and the inferior medial frontal gyrus. Our results illustrate important anatomical connections that may explain the functional changes associated with cluster headaches and elucidate possible mechanisms responsible for triggering attacks.

Chronic stimulation of the posterior hypothalamic region for cluster headache: technique and 1-year results in four patients

OBJECT

Cluster headache (CH) is the most severe of the primary headache disorders. Based on the finding that regional cerebral blood flow is increased in the ipsilateral posterior hypothalamic region during a CH attack, a novel neurosurgical procedure for CH was recently introduced: hypothalamic deep brain stimulation (DBS). Two small case series have been described. Here, the authors report their technical approach, intraoperative physiological observations, and 1-year outcomes after hypothalamic DBS in four patients with medically intractable CHs.

METHODS

Patients underwent unilateral magnetic resonance (MR) imaging-guided stereotactic implantation of a Medtronic DBS (model 3387) lead and Soletra pulse generator system. Intended tip coordinates were 3 mm posterior, 5 mm inferior, and 2 mm lateral to the midcommissural point. Microelectrode recording and intraoperative test stimulation were performed. Lead locations were measured on postoperative MR images. The intensity, frequency, and severity of headaches throughout a 1-week period were tracked in patient diaries immediately prior to surgery and after 1 year of continuous stimulation. At the I-year follow-up examination, DBS had produced a greater than 50% reduction in headache intensity or frequency in two of four cases. Active contacts were located 3 to 6 mm posterior to the mammillothalamic tract. Neurons in the target region showed low-frequency tonic discharge.

CONCLUSIONS

In two previously published case series, headache relief was obtained in many but not all patients. The results of these open-label studies justify a larger, prospective trial but do not yet justify widespread clinical application of this technique.

Cluster headache: a review of neuroimaging findings

Classified as a trigeminal autonomic cephalalgia, cluster headache is characterized by recurrent short-lived excruciating pain attacks, which are concurrent with autonomic signs. These clinical features have led to the assumption that cluster headache's pathophysiology involves central nervous system structures, including the hypothalamus. In the past decade, neuroimaging studies have confirmed such clinically derived theory by uncovering in vivo neuronal changes located in the inferior posterior hypothalamus. Using a variety of neuro-imaging techniques (functional , biochemical , and structural ) in patients with cluster headache, we are making improvements in our understanding of the role of the brain in this disorder. This article summarizes neuroimaging findings in cluster headache patients, describing neuronal changes that occur during attacks and remission, as well as during hypothalamic stimulation.

The Hypothalamic Orexinergic System: Pain and Primary Headaches

The primary headaches are a group of distinct individually characterized attack forms, which although varying in presentation, share some common anatomical basis responsible for the pain component of the attack. The hypothalamus is known to modulate a multitude of functions and has been shown to be involved in the pathophysiology of a variety of primary headaches including cluster headache and chronic migraine. It seems likely that it may be involved in other primary headache disorders due to their episodic nature and may underlie many of their diverse symptoms. We discuss the hypothalamic involvement in the modulation of trigeminovascular processing and examine the involvement of the hypothalamic orexinergic system as a key regulator of this function.

Trigeminal Autonomic Cephalalgias: Current and Future Treatments

The trigeminal autonomic cephalgias include cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT). The evidence for the current treatment options for each of these syndromes is considered, including oxygen, sumatriptan, and verapamil in cluster headache, indomethacin in paroxysmal hemicrania, and intravenous lidocaine and lamotrigine in SUNCT. Some treatments such as topiramate have an effect in all of these, as well as in migraine and other pain syndromes. The involvement of the hypothalamus in functional imaging studies implies that this may be a substrate for targeting treatment options in the future.

Magnetic resonance angiography shows dilatation of the middle cerebral artery after infusion of glyceryl trinitrate in healthy volunteers

Previous studies have reported dilatation of the middle cerebral artery (MCA) during acute glyceryl trinitrate (GTN)-induced headache, using imaging techniques such as transcranial Doppler (TCD), positron emission tomography (PET) and single photon emission computerized tomography (SPECT). In the present study we aimed to evaluate whether magnetic resonance angiography (MRA) may be used to examine the effect of GTN on the MCA, with respect to changes in diameter and cross-sectional area in healthy volunteers. In addition, we wanted to determine the intra- and inter-observer variation of the method. In a randomized, double blind, crossover study 12 healthy volunteers received intravenous infusion of GTN (0.5 microg/kg/min for 20 min) or placebo. Using 1.5 Tesla MRA, we recorded changes in the diameter and cross-sectional area of MCA before, during and after infusion of GTN. The MRA images were evaluated by two blinded, independent observers/neuroradiologists. The primary endpoints were the differences in the AUC for diameter and cross-sectional area of the MCA between the two experimental conditions and the intra- and inter-observer variation. The areas under the curve (AUC) of the MCA diameter and cross-sectional area were significantly greater after GTN than after placebo (P < 0.05). The intra-observer variation (day-to-day) at baseline was 8.3% and 10.9% for the two observers. The mean inter-observer variation of the cross-sectional MCA area was 15.5% and for the diameter measurements 8%. The present study shows that the MRA method gives a reliable semi-quantitative index of the vascular changes in the intra-cerebral arteries after infusion of GTN and may be useful for headache research.

Neuromodulatory approaches to the treatment of trigeminal autonomic cephalalgias

The trigeminal autonomic cephalalgias (TACs) are a group of primary headache syndromes characterised by intense pain and associated activation of cranial parasympathetic autonomic outflow pathways out of proportion to the pain. The TACs include cluster headache, paroxysmal hemicrania and SUNCT (short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing). The pathophysiology of these syndromes involves activation of the trigeminal-autonomic reflex, whose afferent limb projects into the trigeminocervical complex in the caudal brainstem and upper cervical spinal cord. Functional brain imaging has shown activations in the posterior hypothalamic grey matter in TACs. This paper reviews the anatomy and physiology of these conditions and the brain imaging findings. Current treatments are summarised and the role of neuromodulation procedures, such as occipital nerve stimulation and deep brain stimulation in the posterior hypothalamus are reviewed. Neuromodulatory procedures are a promising avenue for these highly disabled patients with treatment refractory TACs.

Chronic high frequency stimulation of the posteromedial hypothalamus in facial pain syndromes and behaviour disorders

Chronic high frequency stimulation (HFS) of the posteromedial hypothalamus (PMH) has been the first direct therapeutic application of functional neuroimaging data in a restorative reversible procedure for the treatment of an otherwise refractory neurological condition; in fact, the target coordinates for the stereotactic implantation of the electrodes have been provided by positron emission tomography (PET) studies, which were performed during cluster headache attacks. HFS of PMH produced a significant and marked reduction of pain attacks in patients with chronic cluster headache (CCH) and in one patient with short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT). The episodes of violent behaviour and psychomotor agitation during the attacks of CCH supported the idea that the posteromedial hypothalamus could be also involved in the control of aggressiveness; this has been previously suggested, in the seventies, by the results obtained in Sano's hypothalamotomies for the treatment of abnormal aggression and disruptive behaviour. On the basis of these considerations, we have performed HFS of the PMH and controlled successfully violent and disruptive behaviour in patients refractory to the conventional sedative drugs. Finally, we also tested the same procedure in three patients with refractory atypical facial pain, but unfortunately, they did not respond to this treatment.

LONG-TERM RESULTS OF RADIOSURGERY FOR REFRACTORY CLUSTER HEADACHE

OBJECTIVE

Medically refractory cluster headache (CH) is a debilitating condition for which few surgical modalities have proven effective. Previous reports involving short-term follow-up of CH patients have reported modest degrees of pain relief after radiosurgery of the trigeminal nerve ipsilateral to symptom onset. With the recent success of deep brain stimulation as a surgical modality for these patients, it becomes imperative for the long-term risks and benefits of radiosurgery to be more extensively delineated. To address this issue, we present our findings from the largest retrospective series of patients undergoing radiosurgery for CH with extended follow-up periods.

METHODS

Between 1997 and 2001, 10 patients with CH underwent gamma knife radiosurgery at our institution. All patients fulfilled clinical criteria for treatment, including complete resistance to pharmacotherapy (usually methysergide, verapamil, and lithium), pain primarily localized to the ophthalmic division of the trigeminal nerve, and psychological stability. The mean age at radiosurgery was 40.3 years (range, 26–62 yr), and the average CH duration was 11.3 years (range, 2–21 yr). Patients received 75 Gy to the 100% isodose line delivered to the most proximal part of the trigeminal nerve where the 50% isodose line was outside the brainstem (4-mm collimator), with a mean follow-up period of 39.7 months (range, 5–88 mo). Pain relief was defined as excellent (free of CH with minimal or no medications), good (50% reduction of CH severity and frequency with medications), fair (25% reduction of CH severity and frequency with medications), or poor (less than 25% reduction of CH severity and frequency with medications).

RESULTS

After radiosurgery, pain relief was poor in nine patients and fair in one patient. Six patients with poor to fair relief initially experienced excellent to good relief (range, 2 wk–2 yr after treatment) before regressing. Five patients (50%) experienced trigeminal nerve dysfunction, manifesting predominantly as facial numbness after treatment.

CONCLUSION

Although some patients may experience short-term pain relief, none had relief sustainable for longer than 2 years. The results from this series indicate that radiosurgery of the trigeminal nerve does not provide long-term pain relief for medically refractory CH.

Brain imaging of clinical pain states: a critical review and strategies for future studies

Research into brain imaging of pain is largely dominated by experimental acute-pain studies. Applied study paradigms have evolved a lot over past years and the ensuing results have furthered enormously our understanding of acute-pain processing. In sharp contrast, published work on brain-imaging in chronic pain remains scant. Furthermore, the results of these studies are highly incongruent, which could be explained by the fact that patient populations studied varied largely in terms of pain history, pain distribution, cause of pain, and psychological set-up. To circumvent these problems, several investigators have used surrogate models of neuropathic pain, but the validity of these models is highly questionable. In this Review we critically discuss the problems and shortcomings of most published reports on chronic pain and we propose some strategies for future studies. We argue that the post-operative pain model is highly appealing since it opens perspectives for prospective longitudinal studies with repeated assessments and it enables control for many confounding factors, which hamper the interpretation of most current studies. We also plead for a multimodal imaging approach in which classic brain-activation studies are supplemented with genetic, neurochemistry, brain morphometry, and transcranial magnetic stimulation studies.

Gene Expression Profiling in Cluster Headache: A Pilot Microarray Study

BACKGROUND

Cluster headache (CH) is a primary neurovascular headache disorder characterized by attacks of excruciating pain accompanied by ipsilateral autonomic symptoms. CH pathophysiology is presumed to involve an activation of hypothalamic and trigeminovascular systems, but inflammation and immunological mechanisms have also been hypothesized to be of importance.

OBJECTIVE

To identify differentially expressed genes during different clinical phases of CH, assuming that changes of pathophysiological importance would also be seen in peripheral venous blood.

METHODS

Blood samples were drawn at 3 consecutive occasions from 3 episodic CH patients: during attacks, between attacks and in remission, and at 1 occasion from 3 matched controls. Global gene expression was analyzed with microarray tehnology using the Affymetrix Human Genome U133 2.0 Plus GeneChip Set, covering more than 54,000 gene transcripts, corresponding to almost 22,000 genes. Quantitative RT-PCR on S100P gene expression was analyzed in 6 patients and 14 controls.

RESULTS

Overall, quite small differences were seen intraindividually and large differences interindividually. However, pairwise comparisons of signal values showed upregulation of several S100 calcium binding proteins; S100A8 (calgranulin A), S100A12 (calgranulin C), and S100P during active phase of the disease compared to remission. Also, annexin A3 (calcium-binding) and ICAM3 showed upregulation. BIRC1 (neuronal apoptosis inhibitory protein), CREB5, HLA-DQA1, and HLA-DQB1 were upregulated in patients compared to controls. The upregulation of S100P during attack versus remission was confirmed by quantitative RT-PCR analysis.

CONCLUSIONS

The S100A8 and S100A12 proteins are considered markers of non-infectious inflammatory disease, while the function of S100P is still largely unknown. Furthermore, upregulation of HLA-DQ genes in CH patients may also indicate an inflammatory response. Upregulation of these pro-inflammatory genes during the active phase of CH has not formerly been reported. Data from this pilot microarray study provide a basis for further studies in CH.

Cluster headache: orbital hemodynamic changes during Valsalva maneuver

BACKGROUND

The clinical features of cluster headache (CH) disclose some vascular changes in the symptomatic region, but few instrumental studies have assessed orbital hemodynamics in patients with this disorder.

METHODS

Orbital blood flow reactivity elicited by Valsalva maneuver (VM) was studied with ophthalmic artery eco-Doppler in 16 patients (14 men and 2 women; mean age: 41.2) suffering from episodic CH and in 18 healthy controls. Patients were examined twice: first, in a cluster period (between pain attacks), and second, in a remission period. Each time peak-systolic and end-diastolic flow velocities were recorded in both ophthalmic arteries at rest and during all phases of VM.

RESULTS

Valsalva phase IV was consistently associated with an increment of blood flow velocities through the ophthalmic arteries. Unlike controls, patients showed an asymmetric vascular reactivity. In the cluster period peak-systolic flow velocity increments were lower on the symptomatic side than on the asymptomatic side (14.1% vs. 34.4%; P < .001), while in remission end-diastolic flow velocity increments were higher in the previously symptomatic orbit (129% vs. 72.9%; P < .05). Vascular reactivity on the asymptomatic side was always similar to that of healthy controls.

CONCLUSIONS

In episodic CH, the symptomatic orbit shows an abnormal vascular reactivity. During the cluster period, basal vasodilation and hyperemia could preclude it from admitting a much greater amount of blood at the end of Valsalva. During remission, there might be some latent vascular changes that lead to supersensitive vasodilator responses and/or opening of arteriovenous shunts under certain circumstances such as Valsalva. These phenomena could be relevant in the pathophysiology of CH.

A review of diagnostic and functional imaging in headache

The neuroimaging of headache patients has revolutionised our understanding of the pathophysiology of primary headaches and provided unique insights into these syndromes. Modern imaging studies point, together with the clinical picture, towards a central triggering cause. The early functional imaging work using positron emission tomography shed light on the genesis of some syndromes, and has recently been refined, implying that the observed activation in migraine (brainstem) and in several trigeminal-autonomic headaches (hypothalamic grey) is involved in the pain process in either a permissive or triggering manner rather than simply as a response to first-division nociception per se. Using the advanced method of voxel-based morphometry, it has been suggested that there is a correlation between the brain area activated specifically in acute cluster headache--the posterior hypothalamic grey matter--and an increase in grey matter in the same region. No structural changes have been found for migraine and medication overuse headache, whereas patients with chronic tension-type headache demonstrated a significant grey matter decrease in regions known to be involved in pain processing. Modern neuroimaging thus clearly suggests that most primary headache syndromes are predominantly driven from the brain, activating the trigeminovascular reflex and needing therapeutics that act on both sides: centrally and peripherally.

Testosterone Replacement Therapy for Treatment Refractory Cluster Headache

OBJECTIVES

To describe the clinical characteristics and laboratory findings of cluster headache patients whose headaches responded to testosterone replacement therapy.

BACKGROUND

Current evidence points to hypothalamic dysfunction, with increased metabolic hyperactivity in the region of the suprachiasmatic nucleus, as being important in the genesis of cluster headaches. This is clinically borne out in the circadian and diurnal behavior of these headaches. For years it has been recognized that male cluster headache patients appear overmasculinized. Recent neuroendocrine and sleep studies now point to an association between gonadotropin and corticotropin levels and hypothalamically entrained pineal secretion of melatonin.

RESULTS

Seven male and 2 female patients, seen between July 2004 and February 2005, and between the ages of 32 and 56, are reported with histories of treatment resistant cluster headaches accompanied by borderline low or low serum testosterone levels. The patients failed to respond to individually tailored medical regimens, including melatonin doses of 12 mg a day or higher, high flow oxygen, maximally tolerated verapamil, antiepileptic agents, and parenteral serotonin agonists. Seven of the 9 patients met 2004 International Classification for the Diagnosis of Headache criteria for chronic cluster headaches; the other 2 patients had episodic cluster headaches of several months duration. After neurological and physical examination all patients had laboratory investigations including fasting lipid panel, PSA (where indicated), LH, FSH, and testosterone levels (both free and total). All 9 patients demonstrated either abnormally low or low, normal testosterone levels. After supplementation with either pure testosterone in 5 of 7 male patients or combination testosterone/estrogen therapy in both female patients, the patients achieved cluster headache freedom for the first 24 hours. Four male chronic cluster patients, all with abnormally low testosterone levels, achieved remission.

CONCLUSIONS

Abnormal testosterone levels in patients with episodic or chronic cluster headaches refractory to maximal medical management may predict a therapeutic response to testosterone replacement therapy. In the described cases, diurnal variation of attacks, a seasonal cluster pattern, and previous, transient responsiveness to melatonin therapy pointed to the hypothalamus as the site of neurological dysfunction. Prospective studies pairing hormone levels and polysomnographic data are needed.

Steroid hormones in cluster headaches

For decades, glucocorticoid therapy has been a well-recognized abortive treatment for cluster headaches. However, the role of steroid hormones, including both glucocorticoids and sex steroids, in the pathophysiology and therapy of cluster headaches has been a topic of much debate and speculation. Current research now points to the importance of cortisol and testosterone in the pathogenesis of cluster headaches, and they appear to be linked mechanistically to another hormone, melatonin. Melatonin, unlike cortisol or testosterone, is not a product of the hypothalamic pituitary axis but of the retinohypothalamic pineal axis, and is the major biomarker of circadian rhythms. The regulation of steroids and melatonin in the pathogenesis of cluster headaches in turn depends on the sympathetic nervous system. Accumulated evidence suggests sympathetic dysfunction--embodied in the Horner sign so commonly seen in the cluster headache--as a necessary ingredient in the inception of the cluster headache. Sympathetic dysfunction now is thought to be associated with the hypercortisolism, hypotestosteronism, and lower-than-normal melatonin levels in the active cluster patient. Future research may hold the key to a fuller explanation of the complex interaction of hormonal systems in the cluster headache.

An fMRI study of cerebral processing of brush-evoked allodynia in neuropathic pain patients

Previous human imaging studies have revealed a network of brain regions involved in the processing of allodynic pain; this includes prefrontal areas, insula, cingulate cortex, primary and secondary somatosensory cortices and parietal association areas. In this study, the neural correlates of the perceived intensity of allodynic pain in neuropathic pain patients were investigated. In eight patients, dynamic mechanical allodynia was provoked and brain responses recorded using functional magnetic resonance imaging (fMRI). Voxels in which the magnitude of fMRI signal correlated linearly with the ratings of allodynic pain across the group were determined in a whole brain analysis using a general linear model. To ensure that activation reflected only allodynic pain ratings, a nuisance variable containing ratings of ongoing pain was included in the analysis. We found that the magnitude of activation in the caudal anterior insula (cAI) correlates with the perceived intensity of allodynic pain across subjects, independent of the level of ongoing pain. However, the peak of activation in the allodynic condition was located in the rostral portion (rAI). This matches the representation of other clinical pain syndromes, confirmed by a literature review. In contrast, experimental pain in healthy volunteers resides predominantly in the cAI, as shown by the same literature review. Taken together, our data and the literature review suggest a functional segregation of anterior insular cortex.

New targets in acute migraine treatment

Migraine is a common and highly disabling neurological problem, whose acute treatment was revolutionized by the triptans, serotonin 5-HT1B/1D receptor agonists. Some patients do not respond to triptans, while others are not suitable for them largely because of contraindications based on vascular disease. The exploration of nonvasoconstrictor treatments for acute migraine offers the prospect of dramatic improvements in patient care, as well as important insights into the mechanisms of migraine. Possibilities for such developments include, calcitonin gene-related peptide receptor antagonists, serotonin 5-HT1F and 5-HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Taken together, the future for migraine and affected patients is bright and promising.

Posterior hypothalamic activation in paroxysmal hemicrania

OBJECTIVE

Paroxysmal hemicrania (PH) is a severe, strictly unilateral headache that lasts 2 to 30 minutes, occurs more than five times daily, is associated with trigeminal autonomic symptoms, and is exquisitely responsive to indomethacin. The purpose of the study was to determine the brain structures active in PH.

METHODS

Seven PH patients were studied using positron emission tomography (PET). Each patient was scanned in three states: (1) acute PH attack-off indomethacin; (2) pain-free-off indomethacin; and (3) pain-free after administration of intramuscular indomethacin 100 mg. The scan images were processed and analyzed using SPM99.

RESULTS

The study showed no significant activations during state 1 compared with state 2, but there was relative activation of the pain neuromatrix in both states 1 and 2 compared with state 3. This suggests that there is persistent activation of the pain neuromatrix during acute PH attacks and during interictal pain-free states off indomethacin that is deactivated by the administration of indomethacin. In addition, the untreated PH state was associated with significant activation of the contralateral posterior hypothalamus and contralateral ventral midbrain, which extended over the red nucleus and the substantia nigra.

INTERPRETATION

These activated subcortical structures may play a pivotal role in the pathophysiology of this syndrome.

[Treatment and prophylaxis for cluster headaches and other trigeminal autonomic headaches. Revised recommendations of the German Migraine and Headache Society]

Following the new IHS classification, cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT syndrome) are included in the classification as trigeminal autonomic cephalgias (TAC). The similarities of these syndromes suggest a considerable shared pathophysiology. These syndromes have in common that they involve activation of trigeminovascular nociceptive pathways with reflex cranial autonomic activation. Clinically, this physiology predicts pain with some combination of lacrimation, conjunctival injection, nasal congestion, or eyelid edema. Broadly the management of TAC comprises acute and prophylactic treatment. Some types of trigeminal autonomic headaches such as paroxysmal hemicrania and hemicrania continua have, unlike cluster headaches, a very robust response to indomethacin, leading to a consideration of indomethacin-sensitive headaches. This review covers the clinical picture and therapeutic options. Although studies following the criteria of evidence-based medicine (EBM) are rare, most patients can be treated sufficiently.

Functional brain imaging in hemicrania continua: implications for nosology and pathophysiology

Hemicrania continua is a strictly unilateral, continuous headache of mild to moderate intensity, with superimposed exacerbations of moderate to severe intensity that are accompanied by trigeminal autonomic features and migrainous symptoms. The syndrome is exquisitely responsive to indomethacin. Its clinical phenotype overlaps with that of the trigeminal autonomic cephalalgias and migraine, in which the hypothalamus and the brain stem, respectively, have been postulated to play central pathophysiologic roles. A recent positron-emission tomography study of a cohort of patients with hemicrania continua demonstrated significant activation of the contralateral posterior hypothalamus and ipsilateral dorsal rostral pons in association with the headache of hemicrania continua. In addition, there was activation of the ipsilateral ventrolateral midbrain, which extended over the red nucleus and the substantia nigra and bilateral pontomedullary junction. No intracranial vessel dilatation was obvious.

Cluster headache: pathogenesis, diagnosis, and management

Cluster headache is a stereotyped primary pain syndrome characterised by strictly unilateral severe pain, localised in or around the eye and accompanied by ipsilateral autonomic features. The syndrome is characterised by the circadian rhythmicity of the short-lived attacks, and the regular recurrence of headache bouts, which are interspersed by periods of complete remission in most individuals. Headaches often start about 1-2 h after falling asleep or in the early morning, and show seasonal variation, suggesting that the hypothalamus has a role in the illness. Consequently, the vascular theory has been superseded by recognition that neurovascular factors are more important. The increased familial risk suggests that cluster headache has a genetic component in some families. Neuroimaging has broadened our pathophysiological view and has led to successful treatment by deep brain stimulation of the hypothalamus. Although most patients can be treated effectively, some do not respond to therapy. Fortunately, time to diagnosis of cluster headache has improved. This is probably the result of a better understanding of the pathophysiology in combination with efficient treatment strategies, leading to a broader acceptance of the syndrome by doctors.

Stimulation of the Posterior Hypothalamus for Medically Intractable Impulsive and Violent Behavior

OBJECTIVE

To describe the therapeutic effect of deep brain stimulation for the treatment of patients with below-average IQs who are affected by aggressive and disruptive behavior and who are resistant to any drug and/or conservative treatment (including occupational therapy).

PATIENTS AND METHODS

Two consecutive patients suffering from mental retardation with aggressive and disruptive behavior and resistant to any pharmacological treatment underwent deep brain stimulation electrode placement in the posteromedial hypothalamus for continuous chronic high-frequency stimulation (HFS). The stereotactic coordinates of the target were chosen according to the study by Sano et al., which involved hypothalamic stereotactic lesions.

RESULTS

HFS of the posteromedial hypothalamus demonstrated consistent improvement of disruptive behavior in both patients at the follow-up evaluation 1 year later.

CONCLUSIONS

HFS of the posteromedial hypothalamus showed similar results to those obtained by Sano et al. in the 1960s with radiofrequency lesions of the same target volume. The reversibility of neurostimulation allows HFS to control disruptive behavior when conservative treatments are ineffective, and drug therapy is uneventful or causes severe side effects. In conclusion, this neuromodulation procedure improved the quality of life and the range of social relationships for both of the treated patients.

Modulation of pain processing in hyperalgesia by cognitive demand

The relationship between pain and cognitive function is of theoretical and clinical interest, exemplified by observations that attention-demanding activities reduce pain in chronically afflicted patients. Previous studies have concentrated on phasic pain, which bears little correspondence to clinical pain conditions. Indeed, phasic pain is often associated with differential or opposing effects to tonic pain in behavioral, lesion, and pharmacological studies. To address how cognitive engagement interacts with tonic pain, we assessed the influence of an attention-demanding cognitive task on pain-evoked neural responses in an experimental model of chronic pain, the capsaicin-induced heat hyperalgesia model. Using functional magnetic resonance imaging (fMRI), we show that activity in the orbitofrontal and medial prefrontal cortices, insula, and cerebellum correlates with the intensity of tonic pain. This pain-related activity in medial prefrontal cortex and cerebellum was modulated by the demand level of the cognitive task. Our findings highlight a role for these structures in the integration of motivational and cognitive functions associated with a physiological state of injury. Within the limitations of an experimental model of pain, we suggest that the findings are relevant to understanding both the neurobiology and pathophysiology of chronic pain and its amelioration by cognitive strategies.

Trigeminal autonomic cephalalgias. Pathophysiology and classification

Trigeminal Autonomic Cephalalgias (TACs) is a grouping of headache syndromes that includes cluster headache, paroxysmal hemicrania and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT). They are recognized clinically by their episodic, stereotypic attack profile and very often prominent cranial autonomic symptoms, such as lacrimation, conjunctival injection or rhinorrhea. They involve afferent activation of the trigeminal innervation of intracranial pain-producing structures, or the perception of that activation, and reflex activation of the facial, seventh cranial, nerve outflow pathway. This excess reflex trigeminal-autonomic activation seems to be permitted by dysfunction in the brain, specifically in the posterior hypothalamic gray matter. Understanding the anatomy and physiology of these disorders has greatly facilitated their management and the development of exciting new strategies such as neuromodulatory approaches to the management of the more intractable cases.

New targets in the acute treatment of headache

PURPOSE OF REVIEW

The aim of this article is to review recently identified targets for the acute treatment of primary headache disorders.

RECENT FINDINGS

Calcitonin gene-related peptide (CGRP) receptor blockade has been shown to be an effective acute anti-migraine strategy and is a non-vasoconstrictor in terms of the mechanism of action. It is likely that direct blockade of CGRP release by inhibition of trigeminal nerves would be similarly effective in both migraine and cluster headache. Options for acute treatment based on preclinical work and initial clinical studies include: serotonin 5HT1F and 5HT1D receptor agonists, glutamate excitatory amino acid receptor antagonists, nitric oxide synthase inhibitors and adenosine A1 receptor agonists. Proof of principle studies with octreotide, a somatostatin receptor agonist, demonstrated it to be better than placebo in the acute treatment of cluster headache but not in the acute management of migraine.

SUMMARY

The prospect of a non-vasoconstrictor acute migraine therapy offers a real opportunity to patients, and perhaps more importantly, provides a therapeutic rationale to plant migraine and cluster headache firmly in the brain as neurological problems.

The clinical characteristics of headache in patients with pituitary tumours

The clinical characteristics of 84 patients with pituitary tumour who had troublesome headache were investigated. The patients presented with chronic (46%) and episodic (30%) migraine, short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT; 5%), cluster headache (4%), hemicrania continua (1%) and primary stabbing headache (27%). It was not possible to classify the headache according to International Headache Society diagnostic criteria in six cases (7%). Cavernous sinus invasion was present in the minority of presentations (21%), but was present in two of three patients with cluster headache. SUNCT-like headache was only seen in patients with acromegaly and prolactinoma. Hypophysectomy improved headache in 49% and exacerbated headache in 15% of cases. Somatostatin analogues improved acromegaly-associated headache in 64% of cases, although rebound headache was described in three patients. Dopamine agonists improved headache in 25% and exacerbated headache in 21% of cases. In certain cases, severe exacerbations in headache were observed with dopamine agonists. Headache appears to be a significant problem in pituitary disease and is associated with a range of headache phenotypes. The presenting phenotype is likely to be governed by a combination of factors, including tumour activity, relationship to the cavernous sinus and patient predisposition to headache. A proposed modification of the current classification of pituitary-associated headache is given.

Cluster Headache Without Autonomic Symptoms: Why Is It different?

BACKGROUND

Some patients with otherwise typical cluster headache (CH) have persistent attacks free of cranial autonomic symptoms (CAS). The factors responsible for this atypical presentation are not known.

OBJECTIVES

To identify factors associated to the absence of CAS in patients with CH.

METHODS

A prospective series of 157 patients with the diagnosis of CH was analyzed, comparing 148 typical CH patients with 9 CH patients without CAS.

RESULTS

Patients without CAS reported significantly less intense attacks (P = .003) when compared to those with CAS. There was also a tendency (not reaching statistical significance) for a higher frequency of females and chronic CH among those without CAS. Otherwise, there were no differences between the two groups (in age, duration of illness, follow-up time, attack duration or frequency, nor side or site of pain). A logistic regression analysis showed that only pain intensity could explain the difference between the two groups, since the other explanatory variables were also associated with different intensity of attacks.

CONCLUSIONS

These results support the hypothesis that CH without cranial autonomic symptoms represents a milder form of CH.

History of cluster headache

Possibly because of the manifestation of severe debilitating pain, cluster headache has been identified in early publications, described in exquisite detail by authors dating as far back as 1641. These early descriptions focused on the symptoms of the episodes rather than the periodicity of their occurrence. Similar to most medical conditions described without anatomic or clearly defined pathophysiologic basis, cluster headache often was named for its clinical manifestations, or less helpfully, by the names of the authors of its descriptive publications. It was only in 1952 that the condition was named for its peculiar tendency to occur in clusters over a period of weeks rather than being a chronic, recurrent, episodic condition similar to migraine. Despite having such an interesting mix of autonomic and physical features, this observation seems to be most instrumental in divulging the true pathogenesis of this disease and correctly localizing its origin anatomically in the hypothalamus.

Cognitive processing in cluster headache

Little is known about specific changes of cognitive processing in cluster headache. Studies on event-related potentials (ERP) suggest that stimulus evaluation is impaired in chronic cluster headache and in episodic cluster headache during the cluster period, but not in the interval between two periods. Patients with chronic paroxysmal hemicrania do not show this impairment. Unlike patients with migraine, patients with cluster headache do not present with a loss of cognitive habituation as measured by ERP. In neuropsychologic evaluations, a reversible decline of memory processing was detected during the cluster attack, but not between two attacks. Long-term observation revealed no progressive cognitive decline in cluster headache patients over the years. With regard to personality changes, a liability susceptibility to anxiety disorders and to hypochondriasis, but not to mood changes, has been described inconsistently. All changes in alterations of cognitive processing in cluster headache are demonstrated to be mild and do not relevantly contribute to the clinical picture of this disease.

Functional neuroimaging of primary headache disorders

Until recently, primary headache disorders such as migraine and cluster headache were considered to be vascular in origin. However, advances in neuroimaging techniques, such as positron emission tomography, single photon emission computerized tomography, and functional magnetic resonance imaging, have augmented the growing clinical evidence that these headaches are primarily driven from the brain. This review covers functional imaging studies in migraine, cluster headache, rarer headache syndromes, and experimental head pain. Together with newer techniques, such as voxel-based morphometry and magnetic resonance spectrometry, functional imaging continues to play a role in elucidating and targeting the neural substrates in each of the primary headache syndromes.

Human brain mechanisms of pain perception and regulation in health and disease

CONTEXT

The perception of pain due to an acute injury or in clinical pain states undergoes substantial processing at supraspinal levels. Supraspinal, brain mechanisms are increasingly recognized as playing a major role in the representation and modulation of pain experience. These neural mechanisms may then contribute to interindividual variations and disabilities associated with chronic pain conditions.

OBJECTIVE

To systematically review the literature regarding how activity in diverse brain regions creates and modulates the experience of acute and chronic pain states, emphasizing the contribution of various imaging techniques to emerging concepts.

DATA SOURCES

MEDLINE and PRE-MEDLINE searches were performed to identify all English-language articles that examine human brain activity during pain, using hemodynamic (PET, fMRI), neuroelectrical (EEG, MEG) and neurochemical methods (MRS, receptor binding and neurotransmitter modulation), from January 1, 1988 to March 1, 2003. Additional studies were identified through bibliographies.

STUDY SELECTION

Studies were selected based on consensus across all four authors. The criteria included well-designed experimental procedures, as well as landmark studies that have significantly advanced the field.

DATA SYNTHESIS

Sixty-eight hemodynamic studies of experimental pain in normal subjects, 30 in clinical pain conditions, and 30 using neuroelectrical methods met selection criteria and were used in a meta-analysis. Another 24 articles were identified where brain neurochemistry of pain was examined. Technical issues that may explain differences between studies across laboratories are expounded. The evidence for and the respective incidences of brain areas constituting the brain network for acute pain are presented. The main components of this network are: primary and secondary somatosensory, insular, anterior cingulate, and prefrontal cortices (S1, S2, IC, ACC, PFC) and thalamus (Th). Evidence for somatotopic organization, based on 10 studies, and psychological modulation, based on 20 studies, is discussed, as well as the temporal sequence of the afferent volley to the cortex, based on neuroelectrical studies. A meta-analysis highlights important methodological differences in identifying the brain network underlying acute pain perception. It also shows that the brain network for acute pain perception in normal subjects is at least partially distinct from that seen in chronic clinical pain conditions and that chronic pain engages brain regions critical for cognitive/emotional assessments, implying that this component of pain may be a distinctive feature between chronic and acute pain. The neurochemical studies highlight the role of opiate and catecholamine transmitters and receptors in pain states, and in the modulation of pain with environmental and genetic influences.

CONCLUSIONS

The nociceptive system is now recognized as a sensory system in its own right, from primary afferents to multiple brain areas. Pain experience is strongly modulated by interactions of ascending and descending pathways. Understanding these modulatory mechanisms in health and in disease is critical for developing fully effective therapies for the treatment of clinical pain conditions.

Posterior hypothalamic and brainstem activation in hemicrania continua

OBJECTIVE

To determine the brain structures involved in mediating the pain of hemicrania continua using positron emission tomography.

BACKGROUND

Hemicrania continua is a strictly unilateral, continuous headache of moderate intensity, with superimposed exacerbations of severe intensity that are accompanied by trigeminal autonomic features and migrainous symptoms. The syndrome is exquisitely responsive to indomethacin. Its clinical phenotype overlaps with that of the trigeminal autonomic headaches and migraine in which the hypothalamus and the brainstem, respectively, have been postulated to play central pathophysiologic roles. We hypothesized, based on the clinical phenotype, that hemicrania continua may involve activations in the hypothalamus, or dorsal rostral pons, or both.

METHODS

Seven patients with hemicrania continua were studied in two sessions each. In one session, the patients were scanned during baseline pain and when rendered completely pain free after being administered indomethacin 100 mg intramuscularly. In the other session, the patients were scanned during baseline pain and when still in pain after being administered placebo intramuscularly. Seven age- and sex-matched nonheadache subjects acted as the control group. The scan images were processed and analyzed using SPM99.

RESULTS

There was a significant activation of the contralateral posterior hypothalamus and ipsilateral dorsal rostral pons in association with the headache of hemicrania continua. In addition, there was activation of the ipsilateral ventrolateral midbrain, which extended over the red nucleus and the substantia nigra, and bilateral pontomedullary junction. No intracranial vessel dilatation was obvious.

CONCLUSIONS

This study demonstrated activations of various subcortical structures, in particular the posterior hypothalamus and the dorsal rostral pons. If posterior hypothalamic and brainstem activation are considered as markers of trigeminal autonomic headaches and migrainous syndromes, respectively, then the activation pattern demonstrated in hemicrania continua mirrors the clinical phenotype, with its overlap with trigeminal autonomic headaches and migraine.

Neurobiology in primary headaches

Primary headaches such as migraine and cluster headache are neurovascular disorders. Migraine is a painful, incapacitating disease that affects a large portion of the adult population with a substantial economic burden on society. The disorder is characterised by recurrent unilateral headaches, usually accompanied by nausea, vomiting, photophobia and/or phonophobia. A number of hypothesis have emerged to explain the specific causes of migraine. Current theories suggest that the initiation of a migraine attack involves a primary central nervous system (CNS) event. It has been suggested that a mutation in a calcium gene channel renders the individual more sensitive to environmental factors, resulting in a wave of cortical spreading depression when the attack is initiated. Genetically, migraine is a complex familial disorder in which the severity and the susceptibility of individuals are most likely governed by several genes that vary between families. Genom wide scans have been performed in migraine with susceptibility regions on several chromosomes some are associated with altered calcium channel function. With positron emission tomography (PET), a migraine active region has been pointed out in the brainstem. In cluster headache, PET studies have implicated a specific active locus in the posterior hypothalamus. Both migraine and cluster headache involve activation of the trigeminovascular system. In support, there is a clear association between the head pain and the release of the neuropeptide calcitonin gene-related peptide (CGRP) from the trigeminovascular system. In cluster headache there is, in addition, release of the parasympathetic neuropeptide vasoactive intestinal peptide (VIP) that is coupled to facial vasomotor symptoms. Triptan administration, activating the 5-HT(1B/1D) receptors, causes the headache to subside and the levels of neuropeptides to normalise, in part through presynaptic inhibition of the cranial sensory nerves. These data suggest a central role for sensory and parasympathetic mechanisms in the pathophysiology of primary headaches. The positive clinical trial with a CGRP receptor antagonist offers a new promising way of treatment.

[The trigeminovascular system in the human. Cerebral blood flow, functional imaging and primary headache]

Primary headache syndromes, such as cluster and migraine, are widely described as vascular headaches, even though there is considerable clinical evidence to suggest that both conditions are primarily central, that is regulated by the brain. The shared anatomical and physiological substrate for both clinical syndromes is the neural innervation of the cranial circulation. Early functional imaging using PET has shed light on the genesis of both syndromes, documenting activation in the midbrain and pons in migraine and in the hypothalamic gray in cluster headache. These areas are involved in the pain process in a permissive or triggering manner rather than simply as a response to first-division nociceptive pain impulses. This article reviews findings in the physiology of the trigeminovascular system which demand renewed consideration of the neural influences in many primary headaches and the physiology of the neural innervation of cranial circulation. Primary headaches should thus be regarded as neurovascular headaches to emphasize the interaction between nerves and vessels which is their underlying characteristic.

[Cluster headache: study of autonomic alterations and other associated manifestations in 28 cases]

The short lasting primary headaches are classified as those without autonomic activation and those with important activation, which includes the cluster headache. This study focuses on the pathophysiology of cluster headache mainly in its autonomic phenomenon (conjunctival injection, lacrimation, nasal congestion, rhinorrhoea, partial ptosis and eyelid oedema) showing the involvement of superior salivatory nucleus with the pain stimulus propagation, which begins in the trigeminal nerve. The autonomic alterations were studied in 28 patients being lacrimation and conjunctival injection, the main features.

The pathophysiology of primary headache

Headache research has been a productive area, and understanding of primary headache pathophysiology has increased greatly. There are many more questions that need to be answered to gain a better understanding of the primary headache process. For the clinician,there is value in understanding the pathophysiology of primary headache, because this understanding can help improve diagnostic acumen and shape treatment plans to provide patients with more effective treatment.

Cluster headache

Cluster headache is a relatively rare episodic headache disorder.Although traditionally it is believed to be a male-related disorder,the sex ratios are changing toward a more even balance. The disorder is characterized by bouts of daily headaches with pain-free remissions for extended times. Though attacks are brief, they are severe and typically are associated with autonomic symptoms. Medical therapies are the mainstay of treatment, with the goal being prevention of headaches in a cycle. Acute therapies, although effective, may be limited in usefulness because of attack frequency. Intractable cases may benefit from histamine desensitization and surgical treatments.

Cluster headache: interictal asymmetric increment in intraocular pressure elicited by Valsalva manoeuvre

Changes in intraocular pressure (IOP) elicited by a Valsalva manoeuvre were studied in 11 male patients (mean age 39.8 years) suffering from episodic cluster headache (CH), and 12 healthy male controls (mean age 39.9 years). The tests were performed at rest and while exhaling hard through a mouthpiece connected to a mercury manometer. In the CH group, during symptomatic periods, between attacks, Valsalva manoeuvre elicited an asymmetric increase in IOP with significantly higher values on the symptomatic side (P = 0011), whereas no asymmetric increments in IOP were found during asymptomatic periods. Outside the cluster period the IOP values both baseline and with Valsalva manoeuvre did not differ from controls. The increment in IOP took place within a few seconds, as in spontaneous CH attacks, thus pointing to a rapid increase in intraocular blood volume or vasodilatation. These findings may reflect a latent increased vascular reactivity of the symptomatic orbit during CH period.

Outpatient Intravenous Dihydroergotamine for Refractory Cluster Headache

OBJECTIVE

To evaluate the efficacy and safety of outpatient intravenous dihydroergotamine (DHE) for treatment of refractory cluster headache.

METHOD

Medical records were retrospectively reviewed of all patients with cluster headache who received outpatient intravenous DHE for treatment of refractory cluster headache between January 1992 and May 2000.

RESULTS

One hundred four treatments were identified in 70 patients. There were 7 dropouts. Of the 97 completed treatments, 60 were for episodic cluster headache and 37 were for chronic cluster headache. Results for all treatments showed complete resolution of pain during the intravenous phase at 1 month in 61 (63%) of 97 cases, partial resolution in 13 cases (15%), and failure in 23 cases (24%). For the treatment of episodic cluster headache, there was complete resolution in 44 (73%) of 60 cases, partial resolution in 9 cases (13%), and failure in 7 cases (12%). For treatment of chronic cluster headache, there was complete resolution in 17 (46%) of the 37 cases, partial resolution in 4 cases (11%), and 16 failures (43%). As regards side effects and safety, the treatment triggered chest pain suspected of being vasospastic angina in 1 patient on day 7 of the treatment, when she was in the subcutaneous phase. Two patients dropped out due to fear of the injection, 1 because of palpitations, 1 because of chest tightness, and 2 others because of leg cramps, nausea, and diarrhea.

CONCLUSIONS

Outpatient intravenous DHE is a safe treatment. It is useful for refractory cluster headache, is more effective for the episodic form than the chronic form, and has a rapid onset of action. It did not change the evolution of the episodic form, but it did appear to induce remission in the chronic form or transform it to the episodic form. We advance a hypothesis to explain this.

Functional neuroimaging of primary headache disorders

Until recently, primary headache disorders such as migraine and cluster headache were considered to be vascular in origin. However, advances in neuroimaging techniques, such as positron emission tomography, single photon emission computerized tomography, and functional magnetic resonance imaging, have augmented the growing clinical evidence that these headaches are primarily driven from the brain. This review covers functional imaging studies in migraine, cluster headache, rarer headache syndromes, and experimental head pain. Together with newer techniques, such as voxel-based morphometry and magnetic resonance spectrometry, functional imaging continues to play a role in elucidating and targeting the neural substrates in each of the primary headache syndromes.

Subcutaneous octreotide in cluster headache: Randomized placebo-controlled double-blind crossover study

Current practical evidence-based acute treatments of cluster headache are limited to subcutaneous and intranasal formulations of sumatriptan, and oxygen. Two small randomized, double-blind trials suggested efficacy of somatostatin in cluster headache. We sought to determine whether octreotide, a somatostatin analog, is effective in the abortive treatment of acute cluster headache. Patients with episodic and chronic cluster headache, as defined by the International Headache Society, were recruited to a double-blind placebo-controlled crossover study. Patients were instructed to treat two attacks of at least moderate pain severity, with at least a 24-hour break, using subcutaneous octreotide microg or matching placebo. The primary end point was the headache response defined as very severe, severe, or moderate pain becomes mild or nil, at 30 minutes. The primary end point was examined using a multilevel analysis approach. A total of 57 patients were recruited of whom 46 provided efficacy data on attacks treated with octreotide and 45 with placebo. The headache response rate with subcutaneous octreotide was 52%, whereas that with placebo was 36%. Modeling the treatment outcome as a binomial where response was determined by treatment, using the patient as the level 2 variable, and considering period effect, sex, and cluster headache type as other variables of interest, we found that the effect of subcutaneous octreotide 100 microg was significantly superior to placebo (p < 0.01). Subcutaneous octreotide 100 microg is effective in the acute treatment of cluster headache when compared with placebo. Nonvasconstrictor treatment of acute cluster headache is possible.

Altered dopamine D2 receptor binding in atypical facial pain

Animal studies suggest that the dopaminergic system plays a role in central pain modulation. We have previously demonstrated with positron emission tomography (PET) that striatal dopaminergic hypofunction may be involved in the burning mouth syndrome. The aim of the present study was to evaluate the nigrostriatal dopaminergic system in patients with atypical facial pain using PET. In seven patients with atypical facial pain, striatal presynaptic dopaminergic function was assessed with [18F]FDOPA and dopamine D1 and D2 receptor availabilities with [11C]NNC 756 and [11C]raclopride, respectively. The results were compared with those of healthy controls. A quantitative region-of-interest analysis showed that the uptakes of [18F]FDOPA and [11C]NNC 756 did not differ between patients and controls. There was a tendency of increased D2 receptor availability in the left putamen (P=0.056), and the D1/D2 ratio in the putamen was decreased bilaterally by 7.7% (P=0.002) in patients when compared to controls. In a voxel-based analysis, the uptake of [11C]raclopride was increased in the left putamen (P=0.025). In conclusion, the increase in D2 receptor availability in the left putamen and the decrease in D1/D2 ratio imply that alterations in the striatal dopaminergic system as evaluated by PET may be involved in chronic orofacial pain conditions.