Phenotypes and clinical subgroups in vestibular migraine: a cross-sectional study with cluster analysis

Objective: The aim of this multicentric cross-sectional study was to collect phenotypes and clinical variability on a large sample of 244 patients enrolled in different university centers in Italy, trying to differentiate subtypes of VM. Background: VM is one of the most frequent episodic vertigo characterized by a great clinical variability for duration of attacks and accompanying symptoms. Diagnosis is based only on clinical history of episodic vertigo in 50% of cases associated with migrainous headache or photo/phonophobia. Methods: We enrolled in different university centers 244 patients affected by definite VM according to the criteria of the Barany Society between January 2022 and December 2022. An audiometric examination and a CNS MRI were performed before inclusion. Patients with low-frequency sensorineural hearing loss were not included, as well as patients with an MRI positive otherwise that for microischemic lesions. Patients were asked to characterize vestibular symptoms choosing among (multiple answers were allowed): internal vertigo, dizziness, visuo-vestibular symptoms/external vertigo; onset of vertigo and duration, neurovegetative, and cochlear accompanying symptoms (hearing loss, tinnitus, and fullness during attacks) were collected as well as migrainous headache and/or photo/phonophobia during vertigo; autoimmune disorders were also analyzed. A bedside examination was performed including study of spontaneous-positional nystagmus with infrared video goggles, post head shaking ny, skull vibration test, and video head impulse test. Results: We included 244 subjects, 181 were females (74.2%). The age of onset of the first vertigo was 36.6 ± 14.5 while of the first headache was 23.2 ± 10.1. A positive correlation has been found between the first headache and the first vertigo. The mean duration of vertigo attacks was 11 ± 16 h. We carried on a cluster analysis to identify subgroups of patients with common clinical features. Four variables allowed to aggregate clusters: age of onset of vertigo, duration of vertigo attacks, presence of migrainous headache during vertigo, and presence of cochlear symptoms during vertigo. We identified 5 clusters: cluster 1/group 1 (23 subjects, 9.4%) characterized by longer duration of vertigo attacks; cluster 2/group 2 (52 subjects, 21.3%) characterized by absence of migrainous headache and cochlear symptoms during vertigo; cluster 3/group 3 (44 subjects, 18%) characterized by presence of cochlear symptoms during vertigo but not headache; cluster 4/group 4 (57 subjects, 23.4%) by the presence of both cochlear symptoms and migrainous headache during vertigo; cluster 5/group 5 (68 subjects, 27.9%) characterized by migrainous headache but no cochlear symptoms during vertigo. Conclusion: VM is with any evidence a heterogeneous disorder and clinical presentations exhibit a great variability. In VM, both symptoms orienting toward a peripheral mechanism (cochlear symptoms) and central ones (long lasting positional non-paroxysmal vertigo) may coexist. Our study is the first published trying to characterize subgroups of VM subjects, thus orienting toward different pathophysiological mechanisms.