Impairment of trigeminal sensory pathways in cluster headache

Pathophysiology of cluster headache: From the trigeminovascular system to the cerebral networks

BACKGROUND

Despite advances in neuroimaging and electrophysiology, cluster headache's pathogenesis remains unclear. This review will examine clinical neurophysiology studies, including electrophysiological and functional neuroimaging, to determine if they might help us construct a neurophysiological model of cluster headache.

RESULTS

Clinical, biochemical, and electrophysiological research have implicated the trigeminal-parasympathetic system in cluster headache pain generation, although the order in which these two systems are activated, which may be somewhat independent, is unknown. Electrophysiology and neuroimaging have found one or more central factors that may cause seasonal and circadian attacks. The well-known posterior hypothalamus, with its primary circadian pacemaker suprachiasmatic nucleus, the brainstem monoaminergic systems, the midbrain, with an emphasis on the dopaminergic system, especially when cluster headache is chronic, and the descending pain control systems appear to be involved. Functional connection investigations have verified electrophysiological evidence of functional changes in distant brain regions connecting to wide cerebral networks other than pain.

CONCLUSION

We propose that under the impact of external time, an inherited misalignment between the primary circadian pacemaker suprachiasmatic nucleus and other secondary extra- suprachiasmatic nucleus clocks may promote disturbance of the body's internal physiological clock, lowering the threshold for bout recurrence.

Alterations of structural connectivity in episodic cluster headache: A graph theoretical analysis

We evaluated structural volumes and connectivity using graph theoretical analysis in patients with cluster headache. Ten patients with episodic cluster headache were recruited, who had a normal brain MRI on visual inspection. We also enrolled a control group of 20 healthy volunteers. All of the participants underwent 3-D volumetric T1-weighted imaging. We obtained the structural volumes using FreeSurfer image analysis and performed structural global and local connectivity analysis using BRAPH. The volumes of the left caudal anterior cingulate and postcentral gyrus were decreased in the patients with cluster headache compared to healthy individuals. In addition, in the measures of local structural connectivity, there was significant hub re-organization in the patients with cluster headache; the strength of the right frontopolar, left pericalcarine, and left posterior cingulate gyrus, the betweenness centrality of the right precentral and left pericalcarine gyrus, and the closeness centrality of the left pericalcarine and left posterior cingulate gyrus were decreased. Whereas the betweenness centrality of the right rostral middle frontal and left inferior temporal gyrus were increased in the patients with cluster headache. However, the measures of global structural connectivity were not different between the patients with cluster headache and healthy individuals. We demonstrate that the structural volumes and connectivity in patients with cluster headache are significantly different from those in healthy controls, especially revealing hub re-organization. These alterations are implicated in the pathogenesis of cluster headache and suggest that cluster headache is a network disease.

Laser-Evoked Cortical Potentials in Cluster Headache

Craniofacial nociceptive processing in patients ( n = 25) suffering from unilateral cluster headache was assessed by laser-evoked cortical potentials (LEPs). Latencies and amplitudes of late (N2, P2) and middle-latency (N1) LEPs were measured in chronic (CCH, n = 9) and episodic cluster headache (ECH, n = 17). In CCH patients on headache side N1c occurred later and P2 amplitude was smaller than on the healthy control side. In active periods of ECH patients P2 latency was shorter on the headache side. In remission periods of ECH patients the N2P2 ratio was lower on the headache side. In 19 out of 26 examinations in 25 headache patients LEP deviated from normative data in healthy controls ( n = 10) without any specific pattern of altered parameters. LEPs document pathological changes in craniofacial nociception in cluster headache. However, there seems to be no pathognomonic deviation pattern that enables reliable diagnosis of cluster headache and application of LEPs in further studies of pathophysiological mechanisms.

Cluster headache: When to worry? Two case reports

Background The clinical criteria for cluster headache (CH) are included in Chapter 3 of the International Classification of Headache Disorders, 3rd beta edition (ICHD-III). CH may sometimes be secondary to other pathologies. Case reports We report two patients in whom the clinical features of CH initially fulfilled the ICHD-III criteria, but who later presented some radical modifications in headache natural history as a result of a secondary pathology. The first case of CH was secondary to a pontine cavernous angioma and the second to a cerebral venous thrombosis. Conclusion We highlight the importance of clinical modifications of CH that could suggest clinical investigations should be performed or repeated to exclude a secondary pathology in a previously diagnosed cluster headache. Some of the pathological mechanisms of CH and brain lesions are discussed.

Pearls and pitfalls: electrophysiology for primary headaches

BACKGROUND

Primary headaches are functional neurological diseases characterized by a dynamic cyclic pattern over time (ictal/pre-/interictal). Electrophysiological recordings can non-invasively assess the activity of an underlying nervous structure or measure its response to various stimuli, and are therefore particularly appropriate for the study of primary headaches. Their interest, however, is chiefly pathophysiological, as interindividual, and to some extent intraindividual, variations preclude their use as diagnostic tools.

AIM OF THE WORK

This article will review the most important findings of electrophysiological studies in primary headache pathophysiology, especially migraine on which numerous studies have been published.

RESULTS

In migraine, the most reproducible hallmark is the interictal lack of neuronal habituation to the repetition of various types of sensory stimulations. The mechanism subtending this phenomenon remains uncertain, but it could be the consequence of a thalamocortical dysrythmia that results in a reduced cortical preactivation level. In tension-type headache as well as in cluster headache, there seems to be an impairment of central pain-controlling mechanisms but the studies are scarce and their outcomes are contradictory. The discrepancies between studies might be as a result of methodological differences as well as patients' dissimilarities, which are also discussed.

CONCLUSIONS AND PERSPECTIVES

Electrophysiology is complementary to functional neuroimaging and will undoubtedly remain an important tool in headache research. One of its upcoming applications is to help select neurostimulation techniques and protocols that correct best the functional abnormalities detectable in certain headache disorders.

Primary headaches and trigeminal neuralgia: neuropathic pain yes or not? Evidences from neurophysiological procedures

Despite the fact that neurophysiological evaluation is not useful for primary headache diagnosis, the nociceptive system exploration through reflexes and evoked potentials procedures may give an aid in understanding the pathophysiological mechanism subtending pain. Neuropathic pain is caused by a lesion or disease of the somatosensory nervous system, which is supported by clinical evaluation and instrumental assessment by trigeminal and nociceptive reflexes and laser evoked potentials. The same methods, applied to migraine and cluster headache, together with evidences coming from structural and functional neuroimaging, excluded the neuropathic origin of pain, which is attaining to symptomatic and idiopathic trigeminal neuralgia, but confirmed a complex dysfunction of pain processing. Tension-type headache fits with a model of non-nociceptive and non-neuropathic pain, subtended by a complex interaction of peripheral muscular and central neuronal factors. The presence of altered modulation of pain concurs with migraine and tension-type headache, and should be taken into account for the choice of the best therapeutic approach.

Predilection to deafferentation pain syndrome after radiosurgery in cluster headache

Cluster-tic syndrome is a rare, disabling disorder. We report the first case of cluster-tic syndrome with a successful response to stereotactic radiosurgery.

After failing optimal medical treatment, a 58-year-old woman suffering from cluster-tic syndrome was treated with gamma knife radiosurgery. The trigeminal nerve and sphenopalatine ganglion were targeted with a maximum dose of 85 and 90 Gy respectively. The patient experienced a complete resolution of the initial pain, but developed, as previously described after radiosurgical treatment for cluster headache, a trigeminal nerve dysfunction. This suggests that trigeminal nerve sensitivity to radiosurgery can be extremely different depending on the underlying pathological condition, and that there is an abnormal sensitivity of the trigeminal nerve in cluster headache patients. We do not recommend trigeminal nerve radiosurgery for treatment of cluster headache.

Neuroimaging and clinical neurophysiology in cluster headache and trigeminal autonomic cephalalgias

Clinical neurophysiology and neuroimaging are two non-invasive approaches used to investigate the pathophysiological basis of primary headaches, including cluster headache (CH) and other trigeminal autonomic cephalalgias (TACs). Modern neuroimaging has revolutionized our understanding of the pathophysiology of primary headaches, and of TACs in particular, focusing on a cerebrovascular dysfunction hypothesis toward a central triggering cause. The introduction of single-photon emission computed tomography (SPECT), positron emission tomography (PET), and voxel-based morphometry has allowed us new insights into mechanisms underlying TACs and occurring during peripheral and/or central neuromodulation. The specific activation of neural structures that is observed exclusively in migraine and in TACs supports the hypothesis that primary headaches are driven predominantly by central nervous system dysfunction, and this has important implications from a therapeutic perspective. Neurophysiological examinations are of little value in the clinical setting; however, most of these tools offer vast potential for exploring further the pathophysiology of primary headaches and the effects of pharmacological treatments Trigeminofacial reflexes, the nociceptive flexion reflex, and evoked potentials have been used in TACs to explore the functional state of brainstem and spinal structures involved in pain processing, contributing to our understanding of the pathophysiology of these primary headaches.

Supraspinal modulation of trigeminal nociception and pain

OBJECTIVE

This study examined modulation of trigeminal pain/nociception by 2 supraspinal mechanisms: emotional controls of nociception and diffuse noxious inhibitory controls.

BACKGROUND

Prior research suggests emotional picture viewing (emotional controls) and tonic noxious stimuli (diffuse noxious inhibitory controls) engage supraspinal mechanisms to modulate pain and nociceptive processes. It is currently unknown, however, whether emotional controls modulate trigeminal pain and nociception. Additionally, the influences of emotional controls and diffuse noxious inhibitory controls have not been compared in the same group of participants.

METHODS

Noxious electrodermal stimuli were delivered to the trigeminal nerve using a concentric electrode designed to selectively activate nociceptive fibers. Trigeminal nociception and pain were assessed (34 participants) from the nociceptive blink reflex and pain ratings, respectively. Emotional controls were engaged by presentation of standardized picture stimuli (pleasant, neutral, and unpleasant) shown to reliably evoke pleasure-induced inhibition and displeasure-induced facilitation of pain and nociception. Diffuse noxious inhibitory controls were engaged with a forearm ischemia task.

RESULTS

Trigeminal pain (self-report ratings) and nociception (blinks) were facilitated by unpleasant pictures and inhibited by pleasant pictures. Emotion induction (as assessed from trend analysis) explained 51% of the variance in trigeminal pain and 25% of the variance in trigeminal nociception. Additionally, forearm ischemia inhibited trigeminal pain but not nociception. The baseline vs ischemia comparison explained 17% of the variance in pain report and 0.1% of the variance in blinks. Supraspinal modulation by emotional controls and diffuse noxious inhibitory controls were uncorrelated.

CONCLUSIONS

Emotional controls and diffuse noxious inhibitory controls modulated trigeminal pain and emotional controls modulated trigeminal nociception. These procedures can be used to study supraspinal modulation of nociceptive processing in disorders of the trigeminal pain system, including headache.

Reduced habituation of trigeminal reflexes in patients with episodic cluster headache during cluster period

A growing body of evidence supports the pivotal role of the hypothalamus in the pathophysiology of cluster headache (CH). On the basis of animal studies, it has been suggested that a hypothalamic dysfunction can lead to a habituation deficit of brainstem reflex responses, as result of a stress-like condition. Taking into account these findings, we tested the hypothesis that habituation of brainstem reflexes may be impaired in CH patients. The habituation phenomenon of the late components (R2 and R3) of the blink reflex was studied in 27 CH patients during the cluster period, in 22 migraine patients interictally and in 20 control subjects. A significant habituation deficit in the R2 and R3 components was found in CH compared with both controls and migraineurs. The lack of habituation in CH, more pronounced than in migraine, points to abnormal processing of sensory stimuli at the trigeminal level that could be driven by hypothalamic dysfunction during the cluster period.

TRIGEMINAL NERVE RADIOSURGICAL TREATMENT IN INTRACTABLE CHRONIC CLUSTER HEADACHE

OBJECTIVE

We have previously reported short-term results of a prospective open trial designed to evaluate trigeminal nerve radiosurgical treatment in intractable chronic cluster headache (CCH). Medium- and long-term results have not yet been reported.

METHODS

Ten patients presenting with a severe and drug-resistant CCH were enrolled (nine men, one woman). The radiosurgical treatment was performed according to the technique usually used for trigeminal neuralgia in our department. A single 4-mm shot was positioned at the level of the cisternal portion of the trigeminal nerve. The median distance between the center of the shot and the emergence of the nerve was 9.35 mm (range, 7.5–13.3 mm). The median of this maximum dose to the brainstem was 8.0 Gy (range, 4.0–11.1 Gy). Mean age was 49.8 years (range, 32–77 yr). Mean duration of the CCH was 9 years (range, 2–33 yr). The mean follow-up period was 36.3 months (range, 24–48 mo).

RESULTS

Two patients had complete relief of CCH. One patient had a good result with evolution in an episodic form. Seven patients had no improvement. Nine patients developed a new trigeminal nerve disturbance: three developed paresthesia with no hypoesthesia and six developed hypoesthesia, including two patients with deafferentation pain. Only one patient had neither paresthesia nor hypoesthesia.

CONCLUSION

We confirmed, with medium- and long-term evaluation, the high rate of toxicity and failure of the technique. The high toxicity, despite a methodology identical to the one used in trigeminal neuralgia, leads us to suspect an underlying specificity of the nerve in CCH. We do not recommend radiosurgery for treatment of intractable CCH.

Impaired thermal perception in cluster headache

Cluster headache is characterized by attacks of severe periorbital pain. Repetitive burst activity in afferent fibers may induce plastic alterations in somatosensory synaptic processing as a prerequisite for recurring and chronic pain. This psychophysical study addressed hypothesized dysfunctions in craniofacial somatosensory processing in cluster headache disease. Thermal and mechanical sensory functions in the periorbital region were assessed by quantitative sensory testing (QST) in 25 cluster headache patients and 60 healthy volunteers. Perception of warmth (p<0.01), cold (p<0.000001), and pressure pain (p<0.05) was reduced on the cluster side as compared with the contralateral asymptomatic side. In contrast to healthy volunteers, warm detection threshold (WDT) and thermal sensory limen (TSL) on one side did not positively correlate with the other side. WDT and TSL negatively correlated with the elapsed time since last attack. All patients showed QST abnormalities on the headache side in comparison to healthy controls. Loss of sensory functions strongly preponderated gain. Several lines of evidence indicate a pivotal role of the hypothalamus in cluster headache pathophysiology. The impairment of warm and cold perception in patients may be based upon a dysfunction of the hypothalamus which is strongly involved in thermosensory control.

Neurophysiological assessment of trigeminal nerve reflexes in disorders of central and peripheral nervous system

The trigeminal nerve and nuclei (the trigeminal complex) are unique in the human body with regard to their anatomical and physiological characteristics. They are also special regarding the lesions in which they are involved, both at the peripheral level because of the susceptibility of some terminal branches, and at the nuclei because of their large size and the large amount of connections with other centers. Conventional magnetic resonance imaging studies are often not sufficiently informative to demonstrate very tiny lesions that could be responsible for an important damage in the brainstem. Therefore, clinical neurophysiology and specifically, the techniques used in the study of the trigeminal functions, remain as convenient diagnostic and research tools to document clinically evident lesions or uncover subclinical abnormalities. This review is focussed on the clinical applicability of the study of trigeminal reflexes, including methods employed in the documentation of focal lesions of peripheral branches, trigeminal involvement of peripheral neuropathies, specific lesions of the trigeminal ganglia, central nervous dysfunctions causing abnormalities in the excitability of trigeminal neurons, and the possible use of trigeminal nerve reflexes in the study of facial pain syndromes and headache.

Cognitive processing in cluster headache

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