Here is the design of a clinical trial:

Official Title: Feasibility and Safety of an Immersive Virtual Reality-based Vestibular Rehabilitation Program for Dizziness, Balance and Fatigue Improvement in People With Multiple Sclerosis: Protocol for a Pilot Randomised Controlled Study

Included conditions:
- Multiple Sclerosis
- Vestibular Disease
- Dizziness
- Balance Disorders
- Fatigue
- Quality of Life
- Usability
- Cybersickness

Study Armgroups:
- {'label': 'Immersive virtual reality-based vestibular training.', 'type': 'EXPERIMENTAL', 'description': 'Subjects in this group will receive the same intervention than the other group of study, but they will wear a 3D head mounted display (Oculus Quest glasses) and will receive real-time gaming feedback in terms of visual and audio output while using the training system.\n\nParticipants will receive a total of 20 sessions (3 sessions of 50 minutes per week, 7 weeks). These sessions will be divided in 10 initial sessions (based on the three first blocks of Cawthorne-Cooksey protocol) and 10 advanced sessions in which vestibular exercises are gradually get more complicated by modifiying the following exercise parameters: base of support width, standing on unstable surface, alternatives single leg support, tandem position, increased velocity of head movements, higher head range motion and coordinated movements with arms and trunk.\n\nSame location, tailoring parameters and physical therapist supervision than conventional vestibular training.', 'interventionNames': ['Other: Immersive Virtual-based vestibular rehabilitation']}
- {'label': 'Conventional vestibular training.', 'type': 'ACTIVE_COMPARATOR', 'description': 'Subjects in the control group will receive a total of 20 sessions of 50 minutes (3 sessions per week, 7 weeks). They will receive traditional "Cawthorne-Cooksey" vestibular rehabilitation exercises. This program improves vestibular compensation through a mechanism of neuroplasticity known as adaptation, habituation and substitution. Just like the virtual reality intervention it will be divided in 10 initial sessions and 10 advanced sessions. For the advanced phase of intervention exercises parameters were the same described for the virtual vestibular rehabilitation intervention.\n\nA physical therapy with at least two years of expertise in vestibular rehabilitation will adjust the difficulty level. The intervention will be conducted at the Physical Therapy Department of the University of Sevilla (Spain).', 'interventionNames': ['Other: Conventional vestibular rehabilitation protocol']}

Interventions:
- {'type': 'OTHER', 'name': 'Immersive Virtual-based vestibular rehabilitation', 'description': 'Vestibular rehabilitation based on virtual environment using a head mounted display', 'armGroupLabels': ['Immersive virtual reality-based vestibular training.']}
- {'type': 'OTHER', 'name': 'Conventional vestibular rehabilitation protocol', 'description': '"Cawthorne-Cooksey" vestibular rehabilitation exercises.', 'armGroupLabels': ['Conventional vestibular training.']}

Primary Outcomes:
- {'measure': 'Feasibility of virtual reality-based vestibular rehabilitation', 'description': 'Usability of virtual reality device: System Usability Scale (0-100%). Higher Scores means higher usability\n\nParticipation rate\n\nRetention rate\n\nAdherence to treatment rate', 'timeFrame': '7 weeks of intervention'}
- {'measure': 'Safety of virtual reality-based vestibular rehabilitation', 'description': 'Cybersickness: Scores ranging between 10 and 15 mean significant symptoms and above 20 indicates a simulator problem\n\nFalls registry\n\nAdverse events registry', 'timeFrame': '7 weeks of intervention'}

Please estimate the sample size based on the assumption: 
Formal sample size calculation is not carried out; recommendations for good practice in feasibility and pilot studies are followed.
Sample size calculation
        A major reason for conducting a pilot study is to determine the initial data to perform a sample size calculation for a larger trial.76 For this reason, the formal sample size will not be carried out. However, following the recommendations of good practice for the design and analysis of feasibility and pilot studies in preparation for RCT,76 77 we aimed to recruit at least 30 subjects (15 per group).