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

A state-of-the-art review of functional magnetic resonance imaging technique integrated with advanced statistical modeling and machine learning for primary headache diagnosis

Primary headache is a very common and burdensome functional headache worldwide, which can be classified as migraine, tension-type headache (TTH), trigeminal autonomic cephalalgia (TAC), and other primary headaches. Managing and treating these different categories require distinct approaches, and accurate diagnosis is crucial. Functional magnetic resonance imaging (fMRI) has become a research hotspot to explore primary headache. By examining the interrelationships between activated brain regions and improving temporal and spatial resolution, fMRI can distinguish between primary headaches and their subtypes. Currently the most commonly used is the cortical brain mapping technique, which is based on blood oxygen level-dependent functional magnetic resonance imaging (BOLD-fMRI). This review sheds light on the state-of-the-art advancements in data analysis based on fMRI technology for primary headaches along with their subtypes. It encompasses not only the conventional analysis methodologies employed to unravel pathophysiological mechanisms, but also deep-learning approaches that integrate these techniques with advanced statistical modeling and machine learning. The aim is to highlight cutting-edge fMRI technologies and provide new insights into the diagnosis of primary headaches.

Modulation of trigeminal neuropathic pain by optogenetic inhibition of posterior hypothalamus in CCI-ION rat

Posterior hypothalamus (PH), an important part of the descending pain processing pathway, has been found to be activated in trigeminal autonomic cephalalgias. However, there are very few studies conducted and information regarding its implications in trigeminal neuropathic pain (TNP). Therefore, we aimed to ascertain whether optogenetic inhibition of PH could affect the outcomes of a chronic constriction injury in the infraorbital nerve (CCI-ION) rat model. Animals were divided into the TNP animal, sham, and naive-control groups. CCI-ION surgery was performed to mimic TNP symptoms, and the optogenetic or null virus was injected into the ipsilateral PH. In vivo single-unit extracellular recordings were obtained from both the ipsilateral ventrolateral periaqueductal gray (vlPAG) and contralateral ventral posteromedial (VPM) thalamus in stimulation "OFF" and "ON" conditions. Alterations in behavioral responses during the stimulation-OFF and stimulation-ON states were examined. We observed that optogenetic inhibition of the PH considerably improved behavioral responses in TNP animals. We found increased and decreased firing activity in the vlPAG and VPM thalamus, respectively, during optogenetic inhibition of the PH. Inhibiting PH attenuates trigeminal pain signal transmission by modulating the vlPAG and trigeminal nucleus caudalis, thereby providing evidence of the therapeutic potential of PH in TNP management.

Role of Functional Neuroimaging in Primary Headache Disorders

Background

Key structures for the pathophysiology of primary headache disorders such as migraine, cluster headache, and other trigeminal autonomic cephalalgias were identified by imaging in the past years.

Objective

Available data on functional imaging in primary headache disorders are summarized in this review.

Material and Methods

We performed a MEDLINE search on December 27^th, 2020 using the search terms "primary headache" AND "imaging" that returned 453 results in English, out of which 137 were labeled reviews. All articles were evaluated for content and relevance for this narrative review.

Results

The structure depicted most consistently using functional imaging in different states of primary headaches (without and with pain) was the posterior hypothalamus. Whole-brain imaging techniques such as resting-state functional resonance imaging showed a wide-ranging association of cortical and subcortical areas with human nociceptive processing in the pathophysiological mechanisms underlying the different TACs. Similarities of distinct groups of primary headache disorders, as well as their differences in brain activation across these disorders, were highlighted.

Conclusion

The importance of neuroimaging research from clinical practice point of view remains the reliable and objective distinction of each individual pain syndrome from one another. This will help to make the correct clinical diagnosis and pave the way for better and effective treatment in the future. More research will be necessary to fulfill this unmet need.

OnabotulinumtoxinA in the treatment of refractory chronic cluster headache

BACKGROUND

Cluster headache (CH) is a clinically well-defined primary headache disorder, approximately 20% of cluster headache sufferers experience recurrent attacks without periods of significant remission. For the treatment of chronic cluster headache (CCH) only limited therapeutic options are available.

METHODS

A potential refractory CCH patient group was identified according to the clinical definition of rCCH based on the consensus statement of the European Headache Federation (EHF). Treatment with OnabotulinumtoxinA (BoNT-A; Botox®, 150 Allergan IU) was done according to the PREEMPT study protocol. A standardized headache diary was used for recording frequency, duration of attacks and pain intensity. To assess personal burden the HIT-6 and the Hospital Anxiety and Depression scale was used. Primary outcome measure was a > 50% reduction in headache minutes.

RESULTS

Seventeen male patients suffering from rCCH, aged 32 ± 11 (mean ± SD) years, presenting a mean disease duration of 6.6 years completed the study of 28 weeks. The cut-off point of > 50% reduction in headache minutes as positive result was reached in 58.8%, 29.4% experienced an improvement of 30-50%. Mean frequency of headache days dropped from 28.2 to 11.8 days at week 24 (p = 0.0001; 95% CI -21.33 to - 11.61;). Intensity of remaining attacks was also reduced significantly. Headache disability scores showed a trend to improvement after BoNT-A.

CONCLUSIONS

Encouraging results for the treatment with BoNT-A in rCCH patients were observed in our study population.

Functional Neuroimaging in Trigeminal Autonomic Cephalalgias

Functional neuroimaging was able to identify key structures for the pathophysiology of trigeminal autonomic cephalalgias (TACs) including cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing or cranial autonomic features and hemicrania continua. The posterior hypothalamus was the structure most consistently depicted with functional imaging in different states of disease with and without pain. Network-oriented imaging techniques such as resting-state functional resonance imaging were able to show a broader involvement of human trigeminal pain processing in the underlying pathophysiological mechanisms of the different TACs, highlighting similarities between this distinct group of primary headache disorders, while also demonstrating the differences in brain activation across these disorders. The most important clinical assignment for neuroimaging research from the treating physician remains the objective and reliable distinction of each individual TAC syndrome from one another, to make the correct clinical diagnosis as the foundation for proper treatment. More research will be necessary to fulfill this unmet need.

Short-Lasting Unilateral Neuralgiform Headache Attacks with Conjunctival Injection and Tearing

SUNCT (Short-lasting Unilateral Neuralgiform headache attacks with Conjunctival injection and Tearing) and SUNA (Short-lasting Unilateral Neuralgiform headache attacks with cranial Autonomic symptoms) are rare primary headache syndromes, classified as Trigeminal Autonomic Cephalalgias (TACs). Hypothalamic involvement in the TACs has been suggested by functional imaging data and clinically with deep brain stimulation.

Fifty-two patients (43 SUNCT, 9 SUNA) were studied to determine the clinical phenotype of these conditions and response to medications. A functional imaging study explored activation of the posterior hypothalamus in attacks of SUNCT/SUNA.

The clinical study characterised SUNCT and SUNA in terms of epidemiology, phenotype and clinical characteristics.

Indomethacin is ineffective on single-blind testing. Intravenous lidocaine was effective in all cases. Open-label trails showed the effectiveness of lamotrigine, topiramate and gabapentin.

On functional imaging there was hypothalamic activation bilaterally in 5/9 SUNCT patients, and contralaterally in two patients. Two SUNCT patients had ipsilateral negative activation. In SUNA the activation was bilaterally negative. There was no hypothalamic activation in a patient with SUNCT secondary to a brainstem lesion.

The data suggests that there should be revised classification for SUNCT and SUNA, with an increased range of attack duration and frequency, cutaneous triggering of attacks, and a lack of refractory period. The concept of ‘attack load’ is introduced. The lack of response to indomethacin and the response to intravenous lidocaine, are useful in diagnostic and therapeutic terms, respectively. Preventive treatments include lamotrigine, gabapentin and topiramate. The role of hypothalamic involvement in SUNCT and SUNA as TACs is considered.

Functional Imaging of Autonomic Regulation: Methods and Key Findings

Central nervous system processing of autonomic function involves a network of regions throughout the brain which can be visualized and measured with neuroimaging techniques, notably functional magnetic resonance imaging (fMRI). The development of fMRI procedures has both confirmed and extended earlier findings from animal models, and human stroke and lesion studies. Assessments with fMRI can elucidate interactions between different central sites in regulating normal autonomic patterning, and demonstrate how disturbed systems can interact to produce aberrant regulation during autonomic challenges. Understanding autonomic dysfunction in various illnesses reveals mechanisms that potentially lead to interventions in the impairments. The objectives here are to: (1) describe the fMRI neuroimaging methodology for assessment of autonomic neural control, (2) outline the widespread, lateralized distribution of function in autonomic sites in the normal brain which includes structures from the neocortex through the medulla and cerebellum, (3) illustrate the importance of the time course of neural changes when coordinating responses, and how those patterns are impacted in conditions of sleep-disordered breathing, and (4) highlight opportunities for future research studies with emerging methodologies. Methodological considerations specific to autonomic testing include timing of challenges relative to the underlying fMRI signal, spatial resolution sufficient to identify autonomic brainstem nuclei, blood pressure, and blood oxygenation influences on the fMRI signal, and the sustained timing, often measured in minutes of challenge periods and recovery. Key findings include the lateralized nature of autonomic organization, which is reminiscent of asymmetric motor, sensory, and language pathways. Testing brain function during autonomic challenges demonstrate closely-integrated timing of responses in connected brain areas during autonomic challenges, and the involvement with brain regions mediating postural and motoric actions, including respiration, and cardiac output. The study of pathological processes associated with autonomic disruption shows susceptibilities of different brain structures to altered timing of neural function, notably in sleep disordered breathing, such as obstructive sleep apnea and congenital central hypoventilation syndrome. The cerebellum, in particular, serves coordination roles for vestibular stimuli and blood pressure changes, and shows both injury and substantially altered timing of responses to pressor challenges in sleep-disordered breathing conditions. The insights into central autonomic processing provided by neuroimaging have assisted understanding of such regulation, and may lead to new treatment options for conditions with disrupted autonomic function.

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 computed 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.

Pearls and pitfalls: Neuroimaging in headache

Premise

One of the most exciting developments in modern neuroscience was the development of imaging techniques providing a non-invasive technique for detection of structure-function relationships characteristic of pain and headache. There is no question that neuroimaging has provided us with a better understanding of how the aura in migraine develops, and it has served as a bridge between neurophysiological studies and clinical findings, although doubtless several questions remain.

Pearls

Neuroimaging drew attention toward central mechanisms in idiopathic headache syndromes. Outstanding functional studies have reinforced the crucial role of the brainstem in acute and chronic migraine and the hypothalamic area in trigemino-autonomic headaches. Several morphometric studies suggest a decreased gray matter in pain-transmitting areas in headache patients; however, those have to be seen in the light of a wealth of pain studies and studies on exercise-dependent plasticity.

Goal

This review focuses on neuroimaging as a scientific tool and highlights the recent advances made in studying primary headache syndromes using functional and structural neuroimaging techniques. It will also point toward open questions and gives recommendations for future studies.

Neuroimaging in cluster headache and other trigeminal autonomic cephalalgias

The central nervous system mechanisms involved in trigeminal autonomic cephalalgias, a group of primary headaches characterized by strictly unilateral head pain that occurs in association with ipsilateral craniofacial autonomic features, are still not comprehensively understood. However, functional imaging methods have revolutionized our understanding of mechanisms involved in these primary headache syndromes. The present review provides a brief overview of the major modern functional neuroimaging techniques used to examine brain structure, biochemistry, metabolic state, and functional capacity. The available functional neuroimaging data in cluster headache and other TACs will thus be summarized. Although the precise brain structures responsible for these primary headache syndromes still remain to be determined, neuroimaging data suggest a major role for posterior hypothalamus activation in initiating and maintaining attacks. Furthermore, pathophysiological involvement of the pain neuromatrix and of the central descending opiatergic pain control system was observed. Given the rapid advances in functional and structural neuroimaging methodologies, it can be expected that these non-invasive techniques will continue to improve our understanding into the nature of the brain dysfunction in cluster headache and other trigeminal autonomic cephalalgias.

Hypothalamic gray matter volume loss in hypnic headache

OBJECTIVE

Hypnic headache (HH) is a rare primary headache disorder characterized by strictly nocturnal headache attacks that mostly occur at the same time at night. The pathophysiology of this disease is poorly understood, but hypothalamic involvement was suspected as the hypothalamus represents the cerebral management center of sleep regulation and pain control.

METHODS

Fourteen patients with HH and 14 age-matched and gender-matched healthy controls were investigated using magnetic resonance imaging-based voxel-based morphometry.

RESULTS

We detected gray matter volume decrease in the posterior hypothalamus of HH patients. Additional gray matter decrease was observed in brain areas known to be associated with cerebral pain processing, including the cingulate cortex, operculum, and frontal lobe, as well as in the temporal lobe.

INTERPRETATION

Our data confirm the hypothesized involvement of the posterior hypothalamus in the pathophysiology of HH and emphasize the importance of this structure for sleep regulation and pain control.

[The window into headache research : what have we learned from functional and structural neuroimaging]

Current functional neuroimaging studies in headache patients have demonstrated that changes in vascular function are not the primary cause for the pain in migraine. Especially in headache research, functional imaging revealed for the first time important information on the pathophysiology of idiopathic syndromes beyond mere anatomical attribution. Several independent studies have reinforced the crucial role of the brainstem in migraine resulting in primary dysfunction of the endogenous antinociceptive systems, including the periaqueductal grey and the dorsal raphe nucleus (DRN) in the midbrain as well as areas involved in the neuronal regulation of cerebral blood flow (DRN and locus coeruleus). The hypothalamus on the other hand is involved in the fundamental processes leading to the acute attacks of cluster headache. These data have been repeatedly replicated by several groups and led to a new understanding of the pathophysiology of these syndromes and specifically the central role of the brain. The recent studies investigating the structural changes in migraine, chronic tension-type headache and cluster headache are not yet clear in their relevance but raise important questions and promise increasing knowledge of one of the most frequent symptoms in humans.

Deep brain stimulation in cluster headache: hypothalamus or midbrain tegmentum?

Functional and structural neuroimaging studies have provided pivotal insights into the pathophysiology of trigeminal autonomic cephalalgias (TACs), particularly cluster headache (CH). Functional imaging studies using positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) in TACs have reported activation of the posterior hypothalamus. A structural neuroimaging study using voxel-based morphometry in CH reported increased volume of the hypothalamic gray, although another larger study failed to reproduce this finding. These studies in CH prompted the use of stereotactic stimulation of the target point identified by functional and structural neuroimaging. The precise anatomical localization of the deep brain stimulation (DBS) target places it at the midbrain tegmentum rather than the posterior hypothalamus. A comparison of the PET and fMRI studies in TACs reveals that the diencephalic/mesencephalic activation is more posteroinferior in the PET studies, straddling the hypothalamus and midbrain tegmentum, whereas the activation is centered on the hypothalamus in the higher spatial resolution fMRI studies. To optimize the outcomes from DBS, it is likely that patients will need to be studied individually using functional imaging techniques that have high spatial and temporal resolution to enable targeting of the appropriate locus with stereotactic stimulation.

Different forms of trigeminal autonomic cephalalgias in the same patient: description of a case

The trigeminal autonomic cephalalgias (TACs), including cluster headache, paroxysmal hemicrania and SUNCT, are characterized by the cardinal combination of short-lasting unilateral pain and autonomic phenomena affecting the head. Hemicrania continua (HC) shares many clinical characteristics with TACs, including unilateral pain and ipsilateral autonomic features. Nevertheless, HC is separately classified in the revised International Classification of Headache Disorders (ICHD-II). Here, we describe the case of a 45-year-old man presenting an unusual concurrence of different forms of primary headaches associated with autonomic signs, including subsequently ipsilateral cluster headache, SUNCT and HC. This report supports the theory that common mechanisms could be involved in pathophysiology of different primary headache syndromes.

Neuroimaging in headache

The neurobiology of migraine is complex, but considerable progress has been made during recent decades with the aid of functional neuroimaging. Imaging studies have provided evidence of both abnormal brain functioning and structural changes. In migraine aura, the blood flow changes initially occur in V3A, an area also showing morphometric abnormalities. Pontine activation is also associated with increased volumetric changes. Similar findings are observed in the hypothalamic region in cluster headache. Other paroxysmal headache disorders, such as short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT), hemicrania paroxistica and hemicrania continua, share this similar pattern of activation as cluster headache, pointing to a common pathogenic mechanism. Further studies are required in order to determine whether these changes are the cause or the consequence of the disease, as well as the possible role they may play in the progression into a chronic disorder.

[Trigeminal autonomic cephalgias. After initial diagnosis, consider secondary causes]

Trigeminal autonomic cephalgias (TAC) are classified as primary headache syndromes. The use of instrumental procedures including neuroimaging in the diagnostic workup of the TACs is controversially discussed in the literature. Several case reports have been previously published, reporting trigeminal autonomic cephalgias related to structural lesions. We contribute two of our own cases of symptomatic TACs and demonstrate that a "classic" clinical presentation does not preclude a symptomatic etiology. Thus, we advocate a systematic diagnostic evaluation including neuroimaging in every patient presenting with symptoms indicative of TAC for the first time.

Pathophysiology of trigeminal autonomic cephalalgias

Cluster headache, paroxysmal hemicrania, and short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) are primary headaches recently classified together as trigeminal autonomic cephalalgias (TACs). The causes of these headaches have long been debated, with "peripheral" hypotheses in opposition to "central" hypotheses. The available information indicates that the pain originates from within the brain in cluster headache. The hypothalamic activation observed during TAC attacks by use of functional neuroimaging, and the success of hypothalamic stimulation as a treatment, confirm that the posterior hypothalamus is crucial in the pathophysiology of these headaches. The posterior hypothalamus is now known to modulate craniofacial pain, and hypothalamic activation occurs in other pain disorders, suggesting that this brain area is likely to have a more complex role in the pathophysiology of TACs than that of a mere trigger. Hypothalamic activation might play a part in terminating rather than triggering attacks, and might also give rise to a central permissive state, allowing attacks to take place.

Paroxysmal Hemicrania in Children—Symptoms, Diagnostic Criteria, Therapy and Outcome

Whereas paroxysmal hemicrania (PH) is studied extensively in adults, even case reports of PH in children are rare. We present the first prospective follow-up study on PH in children. Our aim was to investigate whether differences exist between paediatric and adult patients. We assessed all children with chronic headache who were referred to our paediatric out-patient pain clinic within 3 years based on interviews and validated questionnaires. Among 628 patients we found five children with PH (0.8%) and three with probable PH (0.5%), in total 1.3%. Pain characteristics, autonomic symptoms and treatment response to indomethacin were similar to adult PH patients. Our results demonstrate that the International Headache Society classification of PH is also applicable to children. We suspect that PH has been underdiagnosed in children and therefore suboptimally treated thus far.

Functional magnetic resonance imaging in episodic cluster headache

We have investigated the cerebral activation centre in four patients with episodic cluster headache (CH) with functional magnetic resonance imaging (f-MRI). The patients underwent MRI scans for anatomical and functional data acquisition in the asymptomatic state, during a headache attack and after subcutaneous administration of sumatriptan. Anatomical images were acquired by means of 3D-MPRAGE sequences and f-MRI images were obtained by means of echo-planar imaging. Data was analysed using the BrainVoyager QX version 1.7.81 software package. In all patients, the data showed significant hypothalamic activation of the hypothalamus ipsilateral to the pain side, attributable to a headache attack. Overall, we have demonstrated the anatomical location of central nervous system activation by means the first f-MRI study in CH patients. f-MRI offers a good balance of spatial and temporal resolution, and this method of study appears appropriate for investigating the pathogenetic aspects of primary headaches. Positron emission tomography and f-MRI may be regarded as little or no importance in a clinical context, they do, however, offer great potential for the exploration of headache physiopathology and the effects of pharmacological treatment.

Posterior Cerebral Hypoperfusion in Migraine Without Aura

In cerebral blood flow studies, migraine aura is characterized by a posterior cortical hypoperfusion. In contrast, only rare and mild changes in brain perfusion have been demonstrated in migraine without aura, suggesting two different haemodynamic patterns in migraine with and without aura. Our aim was to study hypoperfusion with positron emission tomography (PET) as early as possible during spontaneous migraine without aura attacks. We used H215O PET to investigate seven patients (six female, one male) with migraine without aura (International Classification of Headache Diseases-II code 1.1) in three situations: during the headache phase, after headache relief following sumatriptan injection, and during an attack-free interval. Statistical analysis was performed with SPM2. Within 4 h after the attack onset, significant relative bilateral posterior cortical hypoperfusion was found and persisted after headache relief following sumatriptan injection. A posterior cortical hypoperfusion demonstrated in migraine without aura could suggest a common pathogenesis in migraine with and without aura. The significance of relative posterior hypoperfusion in migraine without aura is discussed according to the current knowledge of migraine pathogenesis.

Neuro-ophthalmologic manifestations of primary headache disorders

Headaches are the most common disorders of the central nervous system affecting 46% of the adult population worldwide. Headaches may be lifelong illnesses, often associated with substantial disability for the individual and the population as a whole. The International Classification of Headache Disorders (ICHD-II) codifies headache disorders into fourteen categories, predominantly primary headaches and secondary headache disorders. Primary headache disorders, mainly migraine and trigeminal autonomic cephalgias (TACs), are frequently associated with neuro-ophthalmologic manifestations. Ophthalmologists are often the first physicians to be involved in the deciphering of headache-related visual disturbances. This article reviews two major primary headache disorders, migraine and trigeminal autonomic cephalgias, and discusses their neuro-ophthalmic complications, clinical presentation, and treatment.

Botulinum toxin type-A therapy in cluster headache: an open study

The objective of this open single-centre study was to evaluate the efficacy and tolerability of botulinum toxin type-A (BTX-A) as add-on in the prophylactic treatment of cluster headache (CH). Twelve male patients with episodic (n=3) or chronic (n=9) CH, unresponsive to common prophylactic medications, were treated with a cumulative dose of 50 International Units (IU) BTX-A according to a standardised injection scheme into the ipsilateral pericranial muscles. One patient with chronic CH experienced a total cessation of attacks and in 2 patients attack intensity and frequency improved. In another patient with chronic CH typical attacks were not influenced, but an ipsilateral continuous occipital headache significantly improved. Patients with episodic CH did not benefit from BTX-A treatment. Tolerability was excellent. These findings provide evidence that BTX-A may be beneficial as an add-on prophylactic therapy for a limited number of patients with chronic CH.

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.

Update on the diagnosis and management of Trigemino-Autonomic Headaches

Severe shortlasting headaches are rare but very disabling conditions with a major impact on the patients' quality of life. Following the IHS criteria, these headaches broadly divide themselves into those associated with autonomic symptoms, so called trigeminal autonomic cephalgias (TACs), and those with few autonomic symptoms. The trigeminal-autonomic cephalgias include cluster headache, paroxysmal hemicranias, and a syndrome called SUNCT (short lasting unilateral neuralgic cephalgias with conjunctival injection and tearing). In all of these syndromes, hemispheric head pain and cranial autonomic symptoms are prominent. The paroxysmal hemicranias have, unlike cluster headaches, a very robust response to indomethacin, leading to a notion of indomethacin-sensitive headaches. Although TACs are, in comparison with migraine, quite rare, it is nevertheless very important to consider the clinical factor that they are easy to diagnose and the treatment is very effective in most patients.

Trigeminal-autonomic headaches in daily clinical practice

Following the revised International Headache Society criteria, a group of short-lasting headaches associated with autonomic symptoms, the so called trigeminal autonomic cephalgias, were newly recognized. The trigeminal autonomic cephalgias include cluster headache, paroxysmal hemicranias and a syndrome involving short-lasting unilateral neuralform cephalgias with conjunctival injection and tearing (SUNCT) syndrome. In all of these syndromes, the half-sided head pain and cranial autonomic symptoms are prominent. All of the trigeminal autonomic cephalgias differ in duration, frequency and rhythmicity of the attacks, the intensity of pain and autonomic symptoms, as well as treatment options. This review gives a brief clinical description of the headache disorders and recent pathophysiological findings, as well as an overview of the treatment of cluster headache, paroxysmal hemicranias and SUNCT syndrome.

Coexistence of TACS and Trigeminal Neuralgia: Pathophysiological Conjectures

BACKGROUND

Trigeminal autonomic cephalgias (TACs) and trigeminal neuralgia are short-lasting unilateral primary headaches whose study is providing insights into craniofacial pain mechanisms. We report on 2 patients in whom trigeminal neuralgia coexists with the TACs paroxysmal hemicrania and SUNCT.

CONCLUSION

Coexistence of trigeminal neuralgia with various TAC forms suggests a pathophysiological relationship between these short-lasting unilateral headaches.

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.

Bilateral SUNCT syndrome associated to chronic maxillary sinus disease

SUNCT syndrome (short lasting unilateral neuralgiform headache with conjuntival injection and tearing) is defined as short attacks of periorbital unilateral pain and accompanied by ipsilateral lacrimation and redness of the same eye. We present an unusual SUNCT case with bilateral pain that started five years ago after an acute maxillary sinus infection that evolved to chronic sinusitis. This association has been described in few SUNCT cases, but its causal role remains uncertain. The patient was a 58 years old man that fulfilled a headache diary that showed the usual circadian pattern, worsening in the morning and afternoon, and responded to treatment with gabapentina. He was submitted to a functional endoscopic sinus surgery and evolved with milder pain. In a review of 21 patients, 5 had a past medical history of sinusitis, but the causal role of this association remained uncertain.

Seasonal, extratrigeminal, episodic paroxysmal hemicrania successfully treated with single suboccipital steroid injections

This case report describes a case of extratrigeminal, episodic paroxysmal hemicrania with a clear seasonal temporal pattern, successfully treated with repeated single suboccipital steroid injections. The pathophysiological and clinical implications of this observation are discussed.

Role of functional imaging in neurological disorders

Neuroimaging in recent years has greatly contributed to our understanding of a wide range of aspects related to central neurological diseases. These include the classification and localization of disease, such as in headache; the understanding of pathology, such as in Parkinson's disease (PD); the mechanisms of reorganization, such as in stroke and multiple sclerosis (MS); and the subclinical progress of disease, such as in amyotrophic lateral sclerosis (ALS). Apart from presurgical mapping, however, the clinical applications so far are limited. Nevertheless, functional imaging does enable the formulation of neurobiological hypotheses that can be tested clinically, and thus is well suited for testing classic clinical hypotheses about how the brain works. Understanding the mechanisms and sites of pathology, such as has been achieved in cluster headaches, facilitates the development of new therapeutic strategies.

Visual disturbances and migraine

There is a close relationship between headache and the visual system. Visual symptoms are prominent features of clinical syndromes such as migraine, cluster headache, and the trigeminal autonomic cephalgias. There are also strong links between headache and the visual system on the basis of genetics, molecular biology, neurophysiology, and neuroimaging. Studies of these links are leading to the development of novel therapies for a variety of headache syndromes. This review is designed to summarize the most recent literature on headache and the visual system. A particular emphasis is placed on publications of interest to clinicians.

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.

The role of imaging in the pathophysiology and diagnosis of headache

PURPOSE OF REVIEW

Functional neuroimaging in headache patients has revolutionized our understanding of these syndromes and provided unique insights into some of the most common maladies in humans, suggesting that at least migraine and cluster headache are driven primarily from the brain. This review highlights new studies and recent advances in studying headache using neuroimaging.

RECENT FINDINGS

Concerning the diagnostics of headache, an EFNS Task Force evaluated recently the usefulness of imaging procedures in non-acute headache patients on the basis of evidence from the literature and defined guidelines on when to use magnetic resonance imaging or computed tomography. Regarding the pathophysiology of primary headache syndromes, repeated and independent findings reinforce the crucial role for the brainstem in acute and probably also in chronic migraine, and the hypothalamic grey in several trigemino-autonomic headaches. If further studies confirm these findings, a better understanding will be gained of where and how acute and preventive therapy can be targeted.

SUMMARY

Given the rapid advances in functional neuroimaging, in particular newer techniques such as voxel-based morphometry and magnetic resonance spectrometry, functional imaging continues to play a significant role and opens new avenues in targeting the neural substrates in individual primary headache syndromes.

Deep brain stimulation to relieve drug-resistant SUNCT

The rare primary headache short-lasting unilateral neuralgiform headache attacks with conjunctival injection and tearing (SUNCT) is characterized by 3 to 200 attacks per day of severe unilateral orbital pain. Functional magnetic resonance imaging shows increased blood flow in the ipsilateral posterior inferior hypothalamus during attacks, indicating activation. We report the first patient with SUNCT in whom severe intractable pain (70 per day) was well controlled by electrode implant to and continuous stimulation of the posterior inferior hypothalamus. Ann Neurol 2005;57:925-927.