Introduction: Cluster headache (CH) is one of the most disabling primary headache syndromes. Recent pathophysiological models focus on central hypothalamic and ventral tegmental area dysfunction. Consequently, neuromodulation with sphenopalatine ganglion, occipital nerve or deep brain stimulation dominate the literature in patients refractory to medical treatment. Although neurovascular conflict is implicated in other facial pain syndromes such as trigeminal neuralgia, its role in CH has not been systematically reviewed.

Methods: Patients with CH underwent high-resolution magnetic resonance imaging of the prepontine cistern between October 2007 and January 2017. Prospectively acquired images were retrospectively reviewed by a neuroradiologist and two neurosurgeons blinded to symptom severity and lateralization. Each trigeminal nerve was classified into one group based on its relationship with arterial and venous structures: (1) no vessel within 1 mm, (2) vessel within 1 mm, (3) vascular contact, (4) vessel distorting the nerve, and (5) vascular contact with atrophy or signal change in the nerve.

Results: 136 patients (mean age at imaging: 44.5 years±11.5, mean age at symptom onset: 31.9±13.2, M/F ratio: 2.3) had 153 symptomatic and 119 asymptomatic nerves. 64 patients had exclusively right-sided attacks; 55 had exclusively left-sided attacks; 17 had side-alternating attacks. Incidence of arterial conflict (groups 3, 4 and 5) was significantly higher in symptomatic compared to asymptomatic nerves (40.5% vs. 26.9%; p=0.02). There was no significant difference in the incidence of venous conflict between symptomatic and asymptomatic nerves (42.5% vs. 42.0%, p=0.94).

Conclusions: Arterial contact is neither required nor sufficient to drive CH attacks, however it may interact with the presence of a central (hypothalamic) generator to drive symptoms in a subgroup of patients. This suggests a rationale for microvascular decompression of the trigeminal nerve in patients with refractory CH and vascular contact on the symptomatic side. Dedicated trigeminal neuroimaging should be considered for all CH patients.

Patient Care: To date, there are no definitive surgical treatments for medically refractory cluster headache, and neuromodulatory techniques (sphenopalatine ganglion stimulation, occipital nerve stimulation, and deep brain stimulation) only provide partial symptomatic relief while necessitating permanent hardware implantation. This preliminary data demonstrates a positive association between arterial conflict and symptomatic nerves in cluster headache patients. These results provide a rationale for performing microvascular decompression of the trigeminal nerve for the treatment of medically refractory cluster headache. Microvascular decompression, which has established efficacy in treating other facial pain syndromes such as trigeminal neuralgia, has the potential to serve as a definitive surgical treatment for this devastating disease, without the involvement of implanted hardware.

Learning Objectives: By the conclusion of this session, participants should be able to: 1)Describe the pathophysiological mechanisms and surgical treatment options for cluster headache 2) Identify the role of vascular conflict in facial pain syndromes, and 3) Discuss, in small groups, the potential role of microvascular decompression for treatment of medically refractory cluster headache

References: 1. Akram H, Miller S, Lagrata S, Hyam J, Jahanshahi M, Hariz M, et al. Ventral tegmental area deep brain stimulation for refractory chronic cluster headache. Neurology. 2016;86(18):1676-82. 2. Maarbjerg S, Wolfram F, Gozalov A, Olesen J, Bendtsen L. Significance of neurovascular contact in classical trigeminal neuralgia. Brain 2015; 138: 311–9. 3. Magis D, Schoenen J. Advances and challenges in neurostimulation for headaches. The Lancet Neurology 2012; 11: 708–19. 4. Matharu MS, Zrinzo L. Deep brain stimulation in cluster headache: hypothalamus or midbrain tegmentum? Curr Pain Headache Rep 2010; 14: 151–9. 5. Goadsby PJ. Pathophysiology of cluster headache: a trigeminal autonomic cephalgia. The Lancet Neurology 2002; 1: 1–7.