NCT02447991.

Study characteristics
Methods	Double‐blind, placebo‐controlled, parallel‐group RCT Duration of treatment: maximum of 3 episodes of vestibular migraine Duration of follow‐up: until 3 attacks have been treated; up to 4 years, as required
Participants	Setting: 2‐centre trial based in the USA at tertiary neurology centres  Sample size: Number randomised: 114 participants reported in the results (discrepancy here with trial registry site, which states that 134 participants were randomised) Number completed: 94 participants Participant baseline characteristics Age:  Described as between 18 and 65 years, but no further details are provided  Gender:  Rizatriptan group: 69 female (77.5%): 20 male (22.5%) Placebo group: 32 female (71.1%): 13 male (28.9%) Probable/definite vestibular migraine:  Inclusion criterion is definite vestibular migraine Attack frequency at baseline:  At least 2 migraine attacks in the preceding 12 months; no other information provided  Duration of disease: Not reported  Inclusion criteria: Age ≥ 18 years and ≤ 65 years. A history that fulfils all criteria for vestibular migraine. Episodes must have a spontaneous onset and resolution without associated hearing loss or interictal neurotologic deficits. Other causes of vestibular symptoms ruled out by appropriate clinical investigations. Current medication list compatible with concomitant medications. Able to maintain a vestibular symptom diary and complete all other study procedures. At least 2 vestibular migraine attacks during the 12‐month observation period.  Exclusion criteria: Ménière’s disease. Migraine with brainstem aura (formerly basilar‐type migraine) by ICHD‐3 criteria. Ischaemic heart disease, coronary artery vasospasm, uncontrolled hypertension. History of stroke or transient ischaemic attack. History of using rizatriptan specifically to treat vestibular attacks. History of adverse response to triptans. Women who are pregnant or breastfeeding. Unable or unwilling to comply with study requirements for any reason. Diagnosis of vestibular migraine: International Headache Society criteria for definite vestibular migraine (see Appendix 1)
Interventions	Intervention (n = 89 randomised, n = 59 completed) Rizatriptan 10 mg capsule to be taken orally during 1 acute episode, until 3 episodes had been treated with the study drug  Comparator (n = 45 randomised, n = 35 completed) Placebo capsules (contents not stated) to be taken orally during 1 acute episode, until 3 episodes had been treated with the study drug Background interventions administered to all participants None reported  Additional treatments (for migraine prophylaxis or other conditions) were permitted if they had been taken during the run‐in period to the trial and participants were on a stable dose
Outcomes	Primary outcomes relevant to this review: Improvement in vertigo Participants reported symptoms using a patient self‐report of the severity of vestibular symptoms (vertigo and unsteadiness/dizziness) where:  0 = no symptoms 1 = mild symptoms (no interference with activities) 2 = moderate symptoms (had to alter some activities) 3 = severe symptoms (had to stop most or all activities) Improvement was considered a reduction in symptoms from moderate/severe to none/mild Change in vertigo Not reported  Serious adverse events Assessed and reported. Defined as those events that result in death, are life‐threatening, require inpatient hospitalisation or prolongation of existing hospitalisation, create persistent or significant disability/incapacity, or cause a congenital anomaly or birth defects. Secondary outcomes relevant to this review: Disease‐specific health‐related quality of life Not reported  Improvement in headache Assessed using the same scale as that used for vertigo (0 to 3, where 3 = most severe symptoms)  Improvement was considered a reduction in symptoms from moderate/severe to none/mild Improvement in other migrainous symptoms  Assessed using the same scale as that used for vertigo (0 to 3, where 3 = most severe symptoms). Symptoms assessed included nausea/vomiting and photo/phonophobia. Improvement was considered a reduction in symptoms from moderate/severe to none/mild Other adverse effects Assessed and reported Other outcomes reported in the study: Sensitivity to motion  Satisfaction with treatment  Health‐related quality of life by Short Form Survey ‐ 12 (SF‐12)
Notes	Research integrity checklist: No retractions or expressions of concern were identified Baseline characteristics of the groups are not fully reported; no concerns based on the (limited) data available Loss to follow‐up is not fully described, but some losses are noted  No implausible results were identified  No concerns over randomisation
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Unclear risk	Quote: "A randomization scheme will be developed to assign the 120 patients expected to be included in the Treatment Phase to parallel treatment arms in a 2:1 ratio of active drug:placebo." Comment: no information is provided regarding generation of the randomisation sequence.
Allocation concealment (selection bias)	Unclear risk	Comment: no information regarding how the randomisation process would occur and whether the randomisation list would be adequately concealed.
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Comment: trial is reported to be blinded to participants and study personnel.
Blinding of outcome assessment (detection bias) All outcomes	Low risk	Comment: self‐reported symptoms by blinded participants.
Incomplete outcome data (attrition bias) All outcomes	High risk	Comment: dropout was 22.2% in the placebo arm and 33.7% in the intervention arm, although some participants did provide partial follow‐up data. This is sufficient to impact the results of the trial, and may introduce the potential for bias in the results.
Selective reporting (reporting bias)	Low risk	Comment: outcomes are fully reported on the trial registry website according to the pre‐specified plan.
Other bias	Low risk	Comment: no other concerns identified.