Motion sickness in migraine and vestibular disorders

Motion sickness is a syndrome provoked by sensory conflict that involves the vestibular system with symptoms resembling those of common neuro-otological disorders including vestibular neuritis (VN) and vestibular migraine (VM). By contrast, it is generally believed that bilateral vestibular failure (BVF) causes reduced motion sickness susceptibility. We investigate differences between these conditions with a single protocol using validated objective experimental (off-vertical axis rotation, OVAR) and validated patient-centred measures of motion sickness susceptibility. Five groups were studied: 1. Normal healthy controls (n=12; mean age 51, SD 17.2; 4/12 women). 2. VN (history of acute vertigo without neurological features or hearing loss; none treated with steroids acutely; positive head thrust test; spontaneous unidirectional horizontal nystagmus; acute caloric canal paresis >30%, mean canal paresis repeated in chronic phase after 6 weeks was 38% (SD 31); n=12; disease duration range 10– 33 months; mean age 45, SD 15.3; 5/12 women). 3. BVF (absent caloric or rotational responses; confirmed in chronic phase; n=8; mean age 51, SD 11.5; 3/8 women). 4. VM (recurrent episodic vestibular symptoms in association with migraine according to published criteria with no vestibular test abnormalities; n=12; mean age 45, SD 15.3; 11/12 women). 5. Migraine without vestibular symptoms (M; recurrent headaches meeting International Headache Society (IHS) 2004 criteria; with/without aura but with no significant vestibular symptoms; n=12; mean age 41, SD 13.6; 8/12 women. Two groups of patient with migraine were studied (one with vestibular symptoms, VM, and one without vestibular symptoms, M) to determine whether the presence of vestibular symptoms in the setting of migraine influences motion sickness susceptibility. The normal controls and the migraine group were screened for vestibular symptoms but did not undergo formal vestibular testing. Participants were seated in a motorised chair (Neurokinetics Inc, Pittsburgh, USA). The torso, legs, feet and head were restrained. The chair took 60 s to reach a constant velocity of 72°/s (0.2 Hz) on a vertical axis in the light, then tilted over 20 s to an angle of 18° from earth vertical. Velocity and tilt remained constant until the chair was stopped, when it was