Patients with a chief complaint of dizziness who visited the Department of Otorhinolaryngology at the National Tokyo Medical Center were included in this study. A retrospective chart review was conducted. A total of 26 patients (4 males, 22 females; average age 51.2±18.6 years) with VM and 31 patients (10 males, 21 females, 57.1±12.4 years) in the chronic stage of VN were treated at our institute from 2015 to 2017. Participants complained of persistent dizziness even after conventional treatment, which included (1) drug therapy with betahistine 36 mg daily for the initial 2–4 weeks, (2) lifestyle counseling regarding exercise and daily walking, and (3) attaining adequate sleep and stress reduction. We recruited participants who met the above-mentioned criteria if (1) the patient was ≥20 years of age, (2) the dizziness had persisted for at least 3 months despite conventional therapy in the outpatient clinic, (3) the patient wished to have intensive, inpatient therapy for the persistent dizziness, and (4) the patient was literate. The exclusion criteria were as follows: (1) a diagnosis of dizziness due to a cerebrovascular disorder, (2) medical contraindications for the necessary head movements during vestibular rehabilitation (e.g., severe cervical disorder), (3) serious comorbidity (for instance, a life-threatening condition, severe cognitive impairment, or severe psychiatric disorder), (4) central nervous system disease, or (5) bilateral vestibular deficit. The diagnosis of VM was based on the ICHD, third edition, beta version  and VN was based on the diagnostic criteria of the Japan Equilibrium Research Association . Patients with VN complained of dizziness for at least 3 months after the diagnosis of VN.
This study was approved by the ethical committee of the National Tokyo Medical Center (R12-009) and was performed in accordance with the ethical standards laid down in the 1964 Declaration of Helsinki and its later amendments.
Dizziness Handicap Inventory
The Dizziness Handicap Inventory (DHI)  is a standard questionnaire that quantitatively evaluates the degree of handicap in the daily lives of patients with vestibular disorders and consists of 25 questions. The total score ranges from 0 (no disability) to 100 (severe disability).
State-Trait Anxiety Inventory
The State-Trait Anxiety Inventory (STAI)  is a self-reported questionnaire consisting of 40 questions, comprising a state anxiety subscale with 20 items and a trait anxiety subscale with 20 items. Each item of the STAI assesses how respondents ‘‘generally’’ feel regarding each statement (e.g., ‘‘I feel at ease’’) on a scale of 1 (almost never) to 4 (almost always).
Self-Rating Depression Scale
The Self-Rating Depression Scale (SDS), designed by Zung in 1965 , is generally considered a reliable instrument for measuring depressive symptoms in primary care. It is a self-reported, 20-item questionnaire. Item responses are rated from 1 to 4, with higher scores corresponding to more frequent symptoms.
Profile of Mood States (POMS)
The POMS is a psychological rating scale used to assess transient, distinct mood states. The POMS measures six different dimensions of mood swings over a period of time. These include tension or anxiety, anger or hostility, vigor or activity, fatigue or inertia, depression or dejection, and confusion or bewilderment. A five-point scale ranging from "not at all" to "extremely" is administered by experimenters to patients for assessing their mood state.
Japanese version of the Medical Outcomes Study 8-items Short Form Health Survey
Health-related QOL was evaluated using the Japanese version of the Medical Outcomes Study 8-items Short Form Health Survey (SF-8) questionnaire, the validity and reliability of which have already been confirmed . SF-8 comprises eight items — physical functioning, role limitation due to physical problems, body pain, general health, vitality, social functioning, role limitation due to emotional problems, and mental health. The physical health component summary score (PCS) and mental health component summary score (MCS) were measured using the norm-based scoring method, which is based on a large-scale population study conducted in Japan . Higher scores on these subscales indicate better health-related QOL.
Measurement of the gravity center fluctuation
The measurement of the gravity center fluctuation for objective assessment of the dizziness severity was performed using a stabilometer (G-5000, Anima Corp., Tokyo, Japan), and the total length of path (LNG) and environmental area (ENV) during eye-opening/closing.
Patients were hospitalized for 5 days in groups of 8–10 individuals; the groups were then taught how to self-perform the 30-min vestibular rehabilitation program , which comprised repeatedly performing the vestibulo-ocular reflex (VOR) and vestibulo-spinal reflex (VSR). The VOR training included seven exercises: (1) quick horizontal eye movement, (2) quick vertical eye movement, (3) eye tracking the horizontal direction, (4) eye tracking the vertical direction, (5) horizontal head shaking with gazing at a fixed target, (6) vertical head shaking with gazing at a fixed target, and (7) oblique head tilting with gazing at a fixed target. Each eye or head movement was repeated 20 times. The VSR training consisted of eight static and five dynamic exercises. The eight static exercises were: (1) standing up and sitting down with the eyes open, repeated thrice; (2) standing up and sitting down with the eyes closed, repeated thrice; (3) standing with the eyes closed and feet apart for 20 s; (4) standing with the eyes closed and feet together for 20 s; (5) standing in a tandem posture with the right foot in the front for 20 s; (6) standing in a tandem posture with the left foot in the front for 20 s; (7) standing on the right foot for 20 s; and (8) standing on the left foot for 20 s. The five dynamic exercises were: (1) 180° turn to the left, repeated thrice; (2) 180° turn to the right, repeated thrice; (3) walking in a tandem posture for 10 m; (4) walking with horizontal head shaking for 10 m; and (5) walking with vertical head shaking for 10 m. During the training, patients performed these exercises thrice a day under the supervision of a physician. After 5 days, all patients learned to perform the exercises. The patients were then instructed to continue performing the vestibular rehabilitation program thrice a day after discharge.
After the participants provided written informed consent, they were evaluated on the day of hospitalization (time 1), as well as a month later (time 2), using the questionnaires mentioned previously. Static posturography was also performed. All drugs that could affect dizziness, including vestibular suppressants, were discontinued soon after the introduction of vestibular rehabilitation.
Data analysis was performed using the SPSS 25.0 software (IBM Corp, NY, USA). A two-way repeated measures analysis of variance (ANOVA) was performed to analyze the effects of group and time on all outcomes. The t-test was used for group comparisons of age. A P-value <0.05 was considered significant.