Altered functional connectivity of the thalamus and salience network in patients with cluster headache: a pilot study

BACKGROUND AND OBJECTIVE

Previous studies have shown that the salience network (SN) and the thalamus are involved in cluster headache (CH) attacks. However, very little is known regarding the altered thalamus-SN functional connectivity in CH. The aim of this study was to explore alterations of functional connectivity between the thalamus and the SN in patients with CH to further gain insight into the pathophysiology of CH.

MATERIALS AND METHODS

The resting-state functional MRI (rs-fMRI) data of 21 patients with CH in the headache attack remission state during in-bout periods and 21 age- and sex-matched normal controls were obtained. The rs-fMRI data were analyzed by the independent component analysis (ICA) method, and the thalamus-SN functional connectivity in patients with right-sided and left-sided CH was compared with that in normal controls.

RESULTS

Decreased functional connectivity was found between the thalamus, both ipsilateral and contralateral to the headache side, and the SN during headache remission state in both right-sided CH patients and left-sided CH patients.

CONCLUSIONS

The findings suggest that the decreased functional connectivity between the thalamus and SN might be one of the pathologies underpinning the CH. This helps us to understand better the nature of the brain dysfunction in CH and the basic pathologies of CH, which implies that this deserves further investigation.

Vessel-wall MRI in primary headaches: The role of neurogenic inflammation

OBJECTIVE

The purpose of this study was to investigate if vessel-wall magnetic resonance imaging (VW-MRI) could differentiate among primary headaches disorders, such as migraine and cluster headache (CH), and detect the presence of neurogenic inflammation.

BACKGROUND

The pathophysiology of primary headaches disorders is complex and not completely clarified. The activation of nociceptive trigeminal afferents through the release of vasoactive neuropeptides, termed "neurogenic inflammation," has been hypothesized. VW-MRI can identify vessel wall changes, reflecting the inflammatory remodeling of the vessel walls despite different etiologies.

METHODS

In this case series, we enrolled seven patients with migraine and eight patients with CH. They underwent a VW-MRI study before and after the intravenous administration of contrast medium, during and outside a migraine attack or cluster period. Two expert neuroradiologists analyzed the magnetic resonance imaging (MRI) studies to identify the presence of vessel wall enhancement or other vascular abnormalities.

RESULTS

Fourteen out of 15 patients had no enhancement. One out of 15, with migraine, showed a focal parietal enhancement in the intracranial portion of a vertebral artery, unmodified during and outside the attack, thus attributable to atherosclerosis. No contrast enhancement attributable to neurogenic inflammation was observed in VW-MRI, both during and outside the attack/cluster in all patients. Moreover, MRI angiography registered slight diffuse vasoconstriction in one of seven patients with migraine during the attack and in one of eight patients with cluster headache during the cluster period; both patients had taken triptans as symptomatic therapy for pain.

CONCLUSIONS

These preliminary results suggest that VW-MRI studies are negative in patients with primary headache disorders even during migraine attacks or cluster periods. The VW-MRI studies did not detect signs of neurogenic inflammation in the intracranial intradural vessels of patients with migraine or CH.

Altered Metabolism in Frontal Brain Circuits in Cluster Headache

Neuroimaging studies have explored cerebral activation patterns in patients with cluster headache (CH) during attacks and have revealed activation of multiple brain areas known to belong to the general pain-processing network. However, it is still unclear which changes in brain metabolism are inherent to the shift from the ‘in bout’ to the ‘out of bout’ period. We measured cerebral glucose metabolism in 11 episodic CH patients during the cluster and again during the remission period with 18F-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET) and compared these data with 11 healthy controls. ‘In bout’ compared with ‘out of bout’ scans were associated with increases of metabolism in the perigenual anterior cingulate cortex (ACC), posterior cingulate cortex, prefrontal cortex, insula, thalamus and temporal cortex. Decreases in metabolism were observed in the cerebellopontine area. Compared with healthy volunteers, hypometabolism in the patient group (‘in bout’ and ‘out of bout’) was found in the perigenual ACC, prefrontal and orbitofrontal cortex. Thus, FDG-PET in CH patients revealed ‘in bout’ activation of brain structures which are involved in descending pain control. Compared with controls, the regional brain metabolism was constitutively decreased in most of these structures, irrespective of the bout. This finding indicates a deficient top-down modulation of antinociceptive circuits in CH patients. We suggest that trigger mechanisms of CH are insufficiently controlled and thus promote the initiation of the bout period and acute attack.

Hypothalamic Activation in Trigeminal Autonomic Cephalgia: Functional Imaging of an Atypical Case

We report headache induced BOLD changes in an atypical case of trigeminal autonomic cephalgia (TAC). A 68-year-old patient was imaged using fMRi during three attacks of a periorbital head-pain with a average duration of 3 min. During the attacks, left sided conjunctival injection, rhinorrhea, lacrimation, facial sweating and hypersalivation were apparent. These attacks were usually partly responsive to oxygen administration but otherwise refractory to any drug. The patient described either attacks with a duration of one minute or less or longer attacks persisting for maximum of 20 min with headaches occurring up to 100 times a day. When considering the symptoms, frequency, duration and therapeutic response of the patient's headache, no clear-cut classification to one of the subtypes of trigeminal autonomic cephalgias (cluster headache, paroxysmal hemicrania, SUNCT) or trigeminal neuralgia was possible. The cerebral activation pattern was similar but not identical to those previously observed in cluster headache and SUNCT with a prominent activation in the hypothalamic grey matter. This case study underlines the conceptual value of the term TAC for the group of headaches focusing around the trigeminal-autonomic reflex. Our results emphasize the importance of the hypothalamus as key region in the pathophysiology of this entity.

Spinal cord stimulation in cluster headache

Neurostimulation techniques for the treatment of primary headache syndromes, particularly for chronic cluster headache (CCH), have received much interest in the recent years. Occipital nerve stimulation (ONS) has yielded favourable clinical results, and is becoming a routine treatment for refractory chronic cluster headache in specialized centres. Meanwhile, other promising techniques, such as spinal cord stimulation (SCS) or sphenopalatine ganglion stimulation, are emerging. This article reviews the current state of clinical research for neurostimulation techniques for chronic cluster headache, and particularly the pros and cons of SCS and ONS.

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.

Hypothalamic deep brain stimulation in positron emission tomography

Recently, functional imaging data have underscored the crucial role the hypothalamus plays in cluster headache, one of the most severe forms of primary headache. This prompted the application of hypothalamic deep brain stimulation. Yet, it is not apparent how stimulation of an area that is thought to act as a pace-maker for acute headache attacks is able to prevent these attacks from occurring. We addressed this issue by examining 10 operated chronic cluster headache patients, using H2(15O)-positron emission tomography and alternately switching the hypothalamic stimulator on and off. The stimulation induced activation in the ipsilateral hypothalamic gray (the site of the stimulator tip), the ipsilateral thalamus, somatosensory cortex and praecuneus, the anterior cingulate cortex, and the ipsilateral trigeminal nucleus and ganglion. We additionally observed deactivation in the middle temporal gyrus, posterior cingulate cortex, and contralateral anterior insula. Both activation and deactivation are situated in cerebral structures belonging to neuronal circuits usually activated in pain transmission and notably in acute cluster headache attacks. Our data argue against an unspecific antinociceptive effect or pure inhibition of hypothalamic activity. Instead, the data suggest a hitherto unrecognized functional modulation of the pain processing network as the mode of action of hypothalamic deep brain stimulation in cluster headache.

Opioidergic changes in the pineal gland and hypothalamus in cluster headache: A ligand PET study

Using PET with the opioidergic ligand [11C]diprenorphine, the authors demonstrate decreased tracer binding in the pineal gland of cluster headache patients vs healthy volunteers. Opioid receptor availability in the hypothalamus and cingulate cortex depended on the duration of the headache disorder. Therefore, the pathophysiology of cluster headache may relate to opioidergic dysfunction in circuitries generating the biologic clock.

Prevalence of patent foramen ovale in a large series of patients with migraine with aura, migraine without aura and cluster headache, and relationship with clinical phenotype

A relationship between migraine and patent foramen ovale (PFO) has been observed in relatively small series of patients so far. Furthermore, the exact mechanism underlying such an association remains unknown. In the present study we determined the prevalence of PFO by contrast–enhanced transcranial Doppler (TCD) in a group of 260 patients with migraine with aura (MA+), 74 patients with migraine without aura (MA–), and 38 patients with cluster headache (CH). One–hundred–sixty–one MA+subjects (61.9%), 12 MA–subjects (16.2%), and 14 CH–subjects (36.8%) were PFO–carriers. The association was independent on the frequency of migraine attacks and complexity of aura. Finally, among the 15 patients who had a history of at least one migraine attack occurring during a Valsalva maneuver only one subject turned out to be PFO–carrier. Our findings confirm previous observations of a link between MA+, CH, and PFO. They also suggest that such an association is independent on migraine clinical phenotype and is probably unrelated to the pathogenic mechanism of paradoxical embolism.

Prevalence of right-to-left shunt in patients with cluster headache

Recent investigations documented that the prevalence of right–to–left shunt (RLS) in patients with migraine with aura (MA) is significantly higher than in healthy controls and similar to prevalence of RLS in young patients with cryptogenic stroke (CS). Nevertheless, little data are available in the literature about RLS prevalence in the other forms of primary headache. The aim of this study was to investigate the occurrence of RLS in patients with cluster headache (CH). We enrolled 30 consecutive patients with CH diagnosis according to the IHS criteria and 40 controls. RLS was assessed with bilateral transcranial Doppler contrast (TCDc) monitoring of middle cerebral arteries. Eleven patients (37%) resulted positive to TCDc monitoring for evaluation of RLS. These data show that the presence of RLS in this group is more prevalent than in the general population and similar to that found in MA and in CS.

Cluster headache and right-to-left shunt on contrast transcranial Doppler: a case-control study

The authors evaluated the prevalence of right-to-left shunt in 40 subjects with cluster headache (CH) vs 40 subjects without primary headaches or cerebrovascular disease. The diagnosis of shunt was made by means of transcranial Doppler with contrast medium. A shunt was found in 17 CH patients (42.5%) and in 7 controls (17.5%) (p = 0.029; OR = 3.48; 95% CI = 1.13 to 10.69).

The contribution of functional neuroimaging to primary headaches

Functional imaging techniques have begun to provide considerable insight into the pathophysiology of primary headache syndromes. PET and f-MRI have allowed to to monitor the physiological cortical reaction and nociceptor transmission of head-pain, but more importantly have identified pathophysiological abnormalities and even the "motor" in migraine and cluster headache attacks. This has even prompted new treatment options such as DBS in cluster headache and will undoubtly change the way we see headache. Innovative techniques such as voxel- and deformation-based morphometry have just started to unravel the structural consequences of chronic pain. Functional imaging will undoubtedly provide further opportunities to study and compare metabolic, haemodynamic and structural parameters in headache sufferers' brains.

[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.

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.

Headache: lessons learned from functional imaging

Most idiopathic headache syndromes are still recognized as vascular headaches although the clinical picture points towards a central triggering cause. The early functional imaging work using PET shed light on the genesis of some syndromes, implying that the observed activation in migraine (brainstem) and in cluster headache (hypothalamic grey) is involved in the pain process in 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 (VBM), it has been suggested that there is a correlation between the brain area activated particularly in acute cluster headache, the posterior hypothalamic grey matter, and some change in grey matter in the same region. Moreover, also in a PET study in cluster headache and experimental headache, a vasodilation of major basal vessels has been observed which is non-specific to the cause and most likely the effect of a trigemino-parasympathetic reflex. Taken together, functional neuroimaging in headache patients has revolutionised this area of study and provided unique insights into some of the commonest maladies in man, suggesting that migraine and cluster headache are primarily driven from the brain.

Neuroimaging in headache

Neuroimaging of primary headache syndromes, such as cluster headache and migraine, has begun to provide a glimpse of the neuroanatomical and physiological basis of the conditions. Although these headache types have been widely described as vascular, there is now considerable imaging and clinical evidence to suggest that they are primarily driven from the brain. The shared anatomical and physiological substrate for both of these clinical problems is the neural innervation of the cranial circulation. Functional imaging with positron emission tomography (PET) has shed light on the genesis of both syndromes, documenting activation in the midbrain and pons in migraine, and in the hypothalamic grey in cluster headache. These areas are involved not simply as a response to first division nociceptive pain impulses but specifically in each syndrome, probably in some permissive or dysfunctional role. In a recent PET study in cluster headache, as well as brain activation, tracer pooled in the region of the major basal arteries. This is likely to be due to vasodilatation of these vessels during the acute pain-attack and represents the first convincing activation of neural vasodilator mechanisms in humans. The author takes the view that the known physiology and pathophysiology of the systems involved dictate that these disorders should be collectively regarded as neurovascular headaches to place emphasis on the interaction between nerves and vessels, which is the underlying characteristic of these syndromes. Understanding this neurovascular relationship facilitates an understanding of the pain mechanisms, while characterising the CNS dysfunction will ultimately allow us to dissect out the basic pathogenesis of these disorders.

Brainstem activation specific to migraine headache

Findings from functional imaging studies have shown activation of the brainstem during migraine without aura (MWOA) and activation of the hypothalamus during cluster headache. We assessed a patient with cluster headache and migraine by positron emission tomography during an active cluster headache after he had taken 1.2 glyceryl trinitate. The patient developed a typical MWOA, during which we saw activation in the dorsal rostral brainstem. There was no activation in the region of the hypothalamus. Our findings provide evidence that migraine involves the brainstem, and show several areas involved in cluster headaches. Our data show the potential for objective distinction between primary headache syndromes with functional imaging, in disorders hitherto distinguished on clinical grounds.

[Cluster headache--clinical aspects, pathophysiology and treatment]

EPIDEMIOLOGY

Cluster headache afflicts somewhat less than one in thousand in the general population. The majority of sufferers are men.

CLINICAL FEATURES

The syndrome is characterized by frequent attacks of intense pain localized in and around the eye on one side, characteristically accompanied by conjunctival injection and lacrimation in this eye, along with nasal stuffiness on the same side and sometimes a Horner's syndrome. All symptoms and signs are strictly unilateral and occur during attacks lasting between 15 minutes and three hours. The attacks occur from once to eight times daily during a period lasting from some weeks to months. After a remission of varying duration, the same pattern recurs.

PATHOPHYSIOLOGY

Recent findings suggest a pivotal role of the hypothalamus in relation to the pathophysiology.

TREATMENT

Sumatriptan injection or oxygen inhalation aborts pain attacks in most patients. The most frequently used prophylactic agents are verapamil, lithium and steroids.

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

BACKGROUND

Cluster headache (CH), like migraine, is still regarded as a vascular headache although in both conditions a CNS cause has been suggested.

OBJECTIVE

To examine neurovascular mechanisms in CH.

METHODS

The authors used functional imaging with PET to investigate 18 CH patients (25 to 62 years old). Ten were in the active period (nine patients with induced attacks and one with spontaneous attack) and eight were out of their bout. In addition, the authors studied spontaneous CH and experimental pain in volunteers using MR angiography.

RESULTS

When an acute CH attack was triggered with nitroglycerin (NTG), activation occurred in the ipsilateral posterior inferior hypothalamic gray, the contralateral ventroposterior thalamus, the anterior cingulate cortex, the ipsilateral basal ganglia, the right anterior frontal lobe, and both insulae. In patients out of the bout who experienced only a mild NTG headache, activation was seen bilaterally in the insulae and frontal cortices, the anterior cingulate cortex, the right thalamus, and the left basal ganglia, but not in the hypothalamic gray area. In addition, the authors found a significant activation (vasodilatation) in the region of the major basal arteries that was caused in part by NTG but was also observed in the spontaneous case and could be induced by capsaicin injection into the forehead. Therefore, the vasodilatation is likely to be mediated by neural mechanisms involved in the acute CH attacks that are present in every human being.

CONCLUSIONS

Dilatation of cranial vessels is not specific to any particular headache syndrome but generic to cranial neurovascular activation, probably mediated by the trigeminoparasympathetic reflex. These data confirm that CH is a CNS disorder best considered as a form of neurovascular headache.

Induction of nitrate tolerance is not a useful treatment in cluster headache

The aims of the present study were to investigate whether induction of nitrate tolerance is a useful treatment in cluster headache and to correlate any changes in attack frequency of cluster headache and nitrate-induced headache to the vascular adaptation during continuous nitrate administration. The results were compared to results obtained from studies of nitrate tolerance in healthy subjects.

MATERIALS AND METHODS

5-isosorbide-mononitrate (5-ISMN) 30 mg was administered orally three times daily for 4 weeks in nine sufferers of chronic cluster headache in a double-blind, randomized placebo-controlled cross-over design. Blood velocity in the middle cerebral artery was measured with transcranial Doppler and the diameters of the temporal and radial arteries were measured with high frequency ultrasound. The haemodynamic data were compared to changes in the frequency of cluster headache attacks and interval headaches over time.

RESULTS

Tolerance was complete within 24 h in the middle cerebral arteries and after 7 days in the symptomatic temporal artery, while tolerance of the radial artery was not observed within this period. The time profiles of tolerance were almost identical to the time profiles observed in healthy subjects. A close temporal association between the disappearance of nitrate-induced headache and tolerance of the temporal artery was observed but tolerance had no effect on cluster headache attack frequency.

CONCLUSIONS

Induction of tolerance to nitrates cannot be used to treat cluster headache. If pain is related to arterial dilatation the results point to extracerebral rather than cerebral arteries as the site of nociception. However, other peripheral and central pain-modulating effects of nitric oxide, the time courses of which are unknown, should also be taken into consideration.

Functional magnetic resonance imaging in spontaneous attacks of SUNCT: short-lasting neuralgiform headache with conjunctival injection and tearing

A 71-year-old woman presented with a short history of episodes of severe left-sided orbital and temporal pain in paroxysms lasting 60 to 90 seconds, and accompanied by ipsilateral lacrimation of the eye, rhinorrhea, and conjunctival injection. Results of clinical examination and structural imaging were normal and a clinical diagnosis of SUNCT (short-lasting unilateral neuralgiform pains with conjunctival injection and tearing) was made. The patient had a BOLD contrast-magnetic resonance imaging study in which significant activation was seen in the region of the ipsilateral hypothalamic gray, comparing the pain to pain-free state. The region of activation was the same in this patient as has been reported in acute attacks of cluster headache.

Correlation between structural and functional changes in brain in an idiopathic headache syndrome

Fundamental to the concept of idiopathic or primary headache, including migraine, tension-type headache and cluster headache, is the currently accepted view that these conditions are due to abnormal brain function with completely normal brain structure. Cluster headache is one such idiopathic headache with many similarities to migraine, including normal brain structure on magnetic resonance imaging and abnormal function in the hypothalamic grey matter by positron emission tomography. Given the consistency of the positron emission tomography findings with the clinical presentation, we sought to assess whether the brains of such patients were structurally normal. We used voxel-based morphometry, an objective and automated method of analyzing changes in brain structure, to study the structure of the brains of patients with cluster headache. We found a co-localization of structural changes and changes in local brain activity with positron emission tomography in the same area of the brain in the same patients. The results indicate that the current view of the neurobiology of cluster headache requires complete revision and that this periodic headache is associated with a hitherto unrecognized brain abnormality in the hypothalamic region. We believe that voxel-based morphometry has the potential to change in the most fundamental way our concept of primary headache disorders, requiring a radical reappraisal of the tenet of structural normality.

Hypothalamic activation in cluster headache attacks

BACKGROUND

Cluster headache, one of the most severe pain syndromes in human beings, is usually described as a vascular headache. However, the striking circadian rhythmicity of this strictly half-sided pain syndrome cannot be readily explained by the vascular hypothesis. We aimed to assess changes in regional cerebral blood flow (rCBF) in patients with cluster headache.

METHODS

We used positron emission tomography (PET) to assess the changes in rCBF, as an index of synaptic activity, during nitroglycerin-induced cluster headache attacks in nine patients who had chronic cluster headache. Eight patients who had cluster headache but were not in the bout acted as a control group.

FINDINGS

In the acute pain state, activation was seen in the ipsilateral inferior hypothalamic grey matter, the contralateral ventroposterior thalamus, the anterior cingulate cortex, and bilaterally in the insulae. Activation in the hypothalamus was seen solely in the pain state and was not seen in patients who have cluster headache but were out of the bout.

INTERPRETATION

Our findings establish central nervous system dysfunction in the region of the hypothalamus as the primum movens in the pathophysiology of cluster headache. We suggest that a radical reappraisal of this type of headache is needed and that it should in general terms, be regarded as a neurovascular headache, to give equal weight to the pathological and physiological mechanisms that are at work.

Cerebral hemodynamics in primary headaches: the transcranial Doppler experience

This paper is an extensive review of the use of transcranial Doppler (TCD) devices in "vascular" forms of headache, and a discussion of the possible occurrence of nonunivocal results, particularly in migraine with or without aura. Despite the large variability in findings, TCD is a noninvasive, safe, and reproducible method for studying hemodynamic phenomena which characterize the clinical profile of migraine and cluster headache attacks. Similarly, it can detect cerebrovasomotor reactivity to external/internal environmental stimuli, as well as responses to pharmacological (therapeutic or diagnostic) agents. Possible future applications of TCD in monitoring vasomotor changes in response to selective stimuli (sympathetic, neuropeptidergic, etc.) are also considered.

Positron emission tomography studies in headache

Positron emission tomography (PET) allows the quantitative measurement of regional cerebral flow (rCBF) in humans in quantitative terms. Gross changes in rCBF are due to variation in vessel diameter. Changes of rCBF also reflect synaptic activity (inhibition and excitation). Therefore, PET was used to monitor changes in blood flow during the aura and headache phase of a migraine attack and to investigate focal areas of increased or decreased blood flow, e.g., in the brain stem and midbrain. Hemispheric rCBF was unchanged in spontaneous migraine attacks without aura. This was true for the headache side as well as for the nonheadache side. Sumatriptan had no effects on cerebral blood flow. Regional cerebral blood flow was increased in midline brain stem structures during the headache phase, but also when the headache had been treated with sumatriptan. This persisting increased activity might reflect activity of a presumed migraine center in the brain stem. These changes are specific for migraine attacks and are not seen during attacks of cluster headache. Positron emission tomography measurements in the early phase of a migraine attack in a single subject showed flow reductions in the occipital cortex spreading forwards; an observation which would be compatible with the existence of spreading depression in humans. Our attempts to study the aura phase with PET have, to date, been unsuccessful.

Tonic pain: a SPET study in normal subjects and cluster headache patients

Whether the pathogenesis of cluster headache (CH) is peripheral or central is still matter of debate. An involvement of central structures related to pain perception and modulation, which also causes an alteration of the physiological pattern of pain perception in CH, has been hypothesized. We investigated the pattern of brain response to pain in normal subjects and CH patients by evaluating the cerebral blood flow (CBF) changes using an experimental model of tonic aching pain stimulation, the cold water pressor test (CWPT). CBF was assessed quantitatively by the Xe-133 inhalation method and single photon emission tomography (SPET), at rest and during CWPT, as previously described (Di Piero et al., 1994). CWPT was performed in 12 volunteers and in seven patients with CH. All the CH patients had a left-sided headache and were studied in a headache-free phase out of the cluster period. During CWPT, volunteers showed a significant CBF increase in the contralateral primary sensorimotor (P < 0.001), frontal (P < 0.01) and temporal (P < 0.002) regions and thalamus (P < 0.01) and in the ipsilateral temporal (P < 0.005) and anterior cingulate (P < 0.01) regions. During left-hand stimulation (ipsilateral to the headache side) by CWPT in CH patients, CBF changes were significantly lower than those observed in volunteers in the contralateral primary sensorimotor region (P < 0.0005) and thalamus region (P < 0.01). There were no significant differences in the brain response observed during the stimulation of the hand contralateral to the headache side. In conclusion, in a headache-free phase out of the cluster period, the pattern of cerebral activation during tonic pain stimulation of the hand ipsilateral to the headache side is critically modified in CH patients in areas which are probably involved in the detection of the stimulus intensity. This modification may reflect a marker of a biological modification of the pain conveyance system. The fact that it is also present out of the active period of the disease, suggests a possible involvement of central tonic pain mechanisms in the pathogenesis of CH.

Right-lateralised central processing for pain of nitroglycerin-induced cluster headache

Recent functional brain imaging studies with positron emission tomography (PET) suggest a preference of the right hemisphere, especially the anterior cingulate cortex (ACC), in affective processing of the clinical pain syndromes. We have investigated the central processing of cluster headache (CH) attacks provoked by sublingual nitroglycerin (NTG). In the cerebrum, provoked CH activated the ACC and the temporopolar region of the right hemisphere in addition to other regions. The regions activated in the ACC (Brodmann area (BA) 24 and 32) are involved in affective/cognitive processing of pain and willed attention. Our study discloses the preferential role of the right hemisphere in attributing emotional valence and attention to the suffering of pain. The findings support the theory of a right hemispheric specialisation in the mediation of withdrawal-related negative affect. The divergence of the distributed central processing between provoked cluster headache attack and experimentally induced acute pain indicates different central mechanisms for different types of pain.

Assessment of the CO2 response by means of non diffusible contrast media and angio-CT in patients with cluster headache

We analyzed the possibility of assessing functional vasomotor changes by means of Arm-Brain Circulation Time (rABCT) and Vascular volume images (Vv) obtained with Angio-CT, in basal condition and following CO2 inhalation, in a sample of 48 patients with cluster headache. CO2 inhalation resulted in the appearance of local changes, which were detected in 28 regions. Analysis by indicator images of Vv-dependent rABCT distribution showed two main patterns: abnormal rABCT mostly evident at the smallest Vv pixels and abnormal rABCT dependent on abnormal Vv distribution. The former pattern was linked to abnormality at the circle of Willis; the latter to abnormal local vasomotor responses. Patients with cluster headache showed both patterns, which prompted us to conclude for the presence of low-degree stenosis in carotid arteries and vasomotor instability in peripheral brain vessels.

SUNCT syndrome: cerebral SPECT images during attacks

Two patients with SUNCT syndrome (short-lasting, unilateral, neuralgiform headache attacks with conjunctival injection and tearing) were investigated. Blood flow velocity in the middle cerebral artery was monitored before, during, and outside four spontaneous attacks. An interhemispheric asymmetry was observed. In the second case, velocity decreased significantly on both sides during attacks in comparison with preattack values. Cerebral SPECT (single photon emission computed tomography) images were obtained during a bout and between attacks in one patient. The radiocompound was injected 5 to 10 seconds after the start of an attack. In both patients, normal tracer uptake and symmetric perfusion was observed during headache periods.

Bilateral asymmetry of cerebral blood velocity in cluster headache

In this study, 69 episodic cluster headache (CH) patients (40 in the active phase, 29 in remission period) underwent a complete TCD examination in order to verify the relationship between cerebral blood velocities (CBVs) and the clinical profile of the disease. Fifteen patients were examined during both phases, while 7 were monitored during a spontaneous attack. Sixty-three healthy sex and age-matched controls were also studied. We measured widespread, asymmetric CBV activation during the active phase, bilaterally in the anterior circulation and also in the posterior circulation. A relative reduction of CBV on the anterior cerebral artery pain side, also during remission, suggests a relationship between local vasodilation and the autonomic symptoms ipsilateral to pain during CH attacks.

Increased parasellar activity on gallium SPECT is not specific for active cluster headache

We have performed Gallium SPECT head scans in 30 successive cluster headache (CH) patients and in 7 migraineurs without aura. Parasellar hyperactivity was judged as present in 81% of chronic CH patients, 54% of episodic CH patients in an active period, 56% of episodic CH patients in remission and 71% of migraineurs. No significant correlations were found between the SPECT images and the duration of the disease, of cluster periods or of remissions. Increased parasellar activity on Gallium SPECT is thus not specific for CH, nor for the active period of episodic CH. The method lacks reliability for investigation of putative cavernous sinus inflammation.

Cluster-tic syndrome and basilar artery ectasia: a case report

A 54-year-old patient presented with two types of pain. The first was similar to trigeminal neuralgia and the second was similar to cluster headache. Clinical diagnosis was cluster-tic syndrome. Neuro-imaging studies disclosed an ectatic basilar artery. The significance of this finding is difficult to ascertain.

Cluster headache: transcranial Doppler assessment of dynamic cerebral circulatory changes during hypocapnia and attack

Transcranial Doppler ultrasound (TCD) investigations have been carried out in cluster headache patients (8 during remission and 6 during bout) and 14 healthy subjects, to assess cerebral vasomotor reactivity (VMR) to hypocapnia induced by voluntary hyperventilation. VMR was expressed as the relative change in blood flow velocity (V) (%) as a function of the reduction in end-tidal PCO2 (PETCO2) (kPa), i.e. V/P ETCO2. TCD with simultaneous PETCO2 monitoring, was also performed in 5 patients during spontaneous attacks. Prior to hyperventilation, there was bilaterally lower anterior cerebral artery velocity (VACA) during the bout than during remission (P < 0.05 on the symptomatic side), and also lower than in the controls. During remission, VACA was higher on the symptomatic side than on the other side (P < 0.05). ACA also showed a lower VMR during the bout than during remission, and it was also lower than in controls (bout vs. remission on the non-symptomatic side, P < 0.01; on the symptomatic side, P > 0.1). Approximately 30 minutes after the onset of attack, PETCO2 started to decrease gradually from 4.65 to 4.10 kPa in one patient with severe attack. The VACA decreased markedly and bilaterally already at an early stage of the attack, i.e. prior to the hyperventilation. Middle cerebral artery velocity tended to decrease 30 minutes after the onset of attack on the symptomatic side, and 50 minutes after onset on the non-symptomatic side. It is concluded that the vascular changes observed most likely are secondary phenomena during the cluster headache attack.

Pain induces decrease of blood flow in the common carotid arteries in cluster headache attacks

Eighteen cluster headache patients and five controls were studied using ultrasound duplex techniques to measure blood flow in the common carotid arteries after nitroglycerin and placebo administration. Vessel diameter and blood flow tended to be greater before nitroglycerin in patients in the cluster headache period than in patients out of period and controls. Nitroglycerin tended to increase blood flow only in patients not in the cluster period and in controls. There was a significant decrease in common carotid blood flow and increase in vascular resistance related to maximum pain in both nitroglycerin-induced and spontaneous cluster headache attacks. Blood flow did not reach the initial flow values after the attack was over. In one patient a hyperventilation attack only temporarily decreased the pain. We suggest that the decrease in blood flow and increase in vascular resistance may be due to constriction of intracranial arteries by reflex activation of sympathetic efferents, rather than to decrease of arterial CO2 tension.

Orbital phlebography: a comparison between cluster headache and other headaches

Orbital phlebography has previously been found to be pathologic in 8 of 13 patients with episodic cluster headache. To compare the frequency and pattern of the pathologic findings in cluster headache with those in other headache categories, orbital phlebographies were carried out in patients with cluster headache, cervicogenic headache, migraine and tension-type headache (tension headache). The investigations were evaluated independently by two radiologists, one of whom had no knowledge of the diagnoses. The frequencies of pathologic findings were at maximal 2/12 in the cluster headache group, 2/11 in the cervicogenic headache group, 5/12 in the migraine group and 5/15 in the tension-type headache group. The investigators agreed completely in the evaluation of 39/50 phlebograms, with lesser disagreements in 7. In conclusion, the frequency of pathologic findings at orbital phlebography in cluster headache was not higher than in the other diagnostic categories investigated, and the pattern of the pathology was generally the same.

Orbital phlebography and signs of inflammation in episodic and chronic cluster headache

One of our 7 patients (14%) with chronic cluster headache had an abnormal orbital phlebogram; this was significantly less than the 61% encountered in our 13 patients with active episodic cluster headache who had this test done. There were no pathologically increased values for serum haptoglobin or orosomucoid in our 9 patients with chronic cluster headache, again significantly less than in our 43 patients with active episodic cluster headache, 51 percent of whom had pathologically increased values of haptoglobin or orosomucoid. These inflammatory signs decreased after the episodic cluster headache was over. Episodic cluster headache we suggest to be due to temporary sympathicoplegia caused by venous vasculitis in the cavernous sinus region; chronic cluster headache we attribute to permanent post-inflammatory sympathicoplegia in the middle fossa.

Cerebral arteriovenous malformation and cluster-like headache

Cluster headache is considered a clinically distinct entity with no underlying gross pathology. However, in rare cases this kind of headache may be mimicked by an arteriovenous malformation. A 49-year-old male is described who had severe bouts of unilateral headache resembling those of cluster headache. The usual accompanying autonomic manifestations were minor and the headache attacks were prolonged. Treatment with ergotamine tartrate and pizotifen failed. A large ipsilateral arteriovenous malformation was diagnosed. Prospectively, true clustering of the headache attacks could not be documented.

Chronic cluster headache associated with a vertebral artery aneurysm

This is a report of a patient with chronic cluster headache-like pain of 12 years duration. Investigation revealed an aneurysm at the junction of the vertebral and posterior inferior cerebellar arteries and after removal the patient experienced resolution of his cluster headache. The headache and aneurysm were both right sided suggesting a possible relationship.

Cerebral hyperemia during spontaneous cluster headaches with excessive cerebral vasoconstriction to hyperoxia

Values for local cerebral blood flow (LCBF) were measured in three dimensions utilizing xenon enhanced computerized tomography among patients during spontaneously occurring cluster headaches, during headache-free intervals and immediately after terminating attacks by inhalation of 100% oxygen. Results were compared with values measured among age-matched normal volunteers. LCBF values measured in five cluster patients while headache-free did not differ from similar measures among age-matched normal volunteers. In three patients during attacks of spontaneously occurring cluster headache, LCBF values for temporal cortex, basal ganglia and subcortical white matter were increased. Immediately after terminating attacks of cluster by 100% oxygen inhalation for five minutes, LCBF values for temporal cortex and basal ganglia became significantly decreased below normal values in five patients with spontaneously occurring cluster headache. Prompt relief of head pain by inhalation of 100% oxygen is associated with abolition of the hyperperfusion of both cortical and subcortical brain structures that occurs during spontaneously occurring cluster headaches and is followed by excessive cerebrovascular constriction. It remains to be determined whether the cerebral hyperemia occurring during cluster headaches is causally related to the head pain or is secondary to the pain itself. Rapid termination of head pain by hyperoxia associated with excessive cerebral vasoconstriction suggests that this vascular phenomenon is unique to cluster headache and offers clues to its pathogenesis.

The cluster diathesis

We present further evidence for a sympathetic defect of vasomotor control of the anterior cerebral artery (ACA) on the side of the headache during cluster periods. In 119 cluster headache patients, utilizing transcranial Doppler, we measured CO2 reactivity of the major intracranial vessels, in and out of cluster. Reactivity was significantly lower during the cluster period, but only in the ACA on the side of the headache. Nineteen patients followed sequentially for a full cycle (ie/both in and out of a cluster period) showed the same changes. In 3 out of 6 patients in an active cluster period, we describe a lesion on Gallium single-photon emission computerized tomography (SPECT) in the region of the cavernous sinus which fades as the patient moves out of cluster. It is felt that this lesion may represent the cavernous sinus plexus lesion postulated as the central lesion in cluster. Changes in the sympathetic outflow at this point could explain the changes we have described in ACA CO2 reactivity during cluster.

Single photon emission computed tomography with technetium-99m hexamethyl propylenamino oxime in the pain-free interval of migraine and cluster headache

Thirty-three headache-free patients (19 F/14 M) suffering from common (n = 9) and classic migraine (n = 19) as well as cluster headache (n = 5) were investigated using the flow tracer 99mTc-hexamethyl propylenamino oxime and single photon emmission computed tomography. A regional decrease of cerebral tracer uptake was observed in 16 patients with common migraine, but only in 3 patients with classic migraine and in no patient with cluster headache. In 10 of 15 cases with hemiplegic symptoms during migraine attack the areas of decreased tracer uptake showed a topographic relationship to neurological deficits. It appears that migraine attacks occur in connection with exacerbations of preexisting changes of neuronal activities, cerebral perfusion and metabolism.

Cortical and subcortical hyperperfusion during migraine and cluster headache measured by Xe CT-CBF

High-resolution, color-coded images of local cerebral blood flow (LCBF) were made utilizing stable xenon-enhanced computed tomography among patients with common migraine (n = 18), classic migraine (n = 12) and cluster headache (n = 5). During spontaneously occurring headache in common and classic migraine patients, LCBF values for cerebral cortex and subcortical gray and white matter were diffusely increased by 20-40% with the exception of the occipital lobes. LCBF increases involved both hemispheres whether the head pain was unilateral or bilateral. No significant differences were noted in the degree or pattern of LCBF increases during headaches of common and classic migraineurs. Similar cerebral hyperperfusion of greater magnitude was observed during cluster headaches but was more prominent on the side of the head pain. Present observations do not support the hypothesis of spreading cortical depression as a cause of classic migraine. From a hemodynamic viewpoint, LCBF increases during headaches of common or classic migraine or cluster appear similar. Evidence is adduced that sympathetic hypofunction with denervation hypersensitivity of cerebral vessels plays a role in the cerebral hyperperfusion of migraine headaches. More pronounced unilateral autonomic derangements appear to account for the symptoms and cerebral hyperperfusion associated with cluster headaches.

A case of parasellar meningioma mimicking cluster headache

A medical history of a 46-year-old male is reported. At 23 years of age, he started having diffuse pain in the left side of his head for up to 30 min once or twice a month. At 28, the pain changed into left-sided cluster headache-like attacks with 2-3 h duration and with ipsilateral conjunctival injection, lacrimation, and rhinnorhea, but with short-lasting free intervals of about two to three weeks. At 36, the pattern of the attacks corresponded to chronic migrainous neuralgia. At 40, the symptoms changed to painful ophthalmoplegia-picture. A left-sided parasellar meningioma was then diagnosed. Removal of the tumor caused complete amelioration. The case history is suggested to support the hypothesis that the cavernous sinus region is involved in cluster headache.

Orbital phlebography in patients with cluster headache

Thirteen patients with cluster headache in an active stage were investigated with orbital phlebography. About 60% of the patients showed pathologic changes on the phlebograms, such as changes in the appearance of the superior ophthalmic vein. Five patients had pathologic changes on both sides and three patients on one side only. All patients with unilateral pathologic findings on orbital phlebography had the attacks on the same side. The phlebographic findings in these patients with cluster headache were very similar to those of patients with the Tolosa-Hunt syndrome. There is also some similarity in the symptoms in the two disorders. It has previously been suggested that the Tolosa-Hunt syndrome is caused by venous vasculitis, and the present findings to some extent support the idea that cluster headache may have the same etiology.