Investigating alternative treatment methods for Mal de Debarquement Syndrome

Participants will be allocated to one of two treatment groups; Group 1: Real Combination (Real VOR + Real TBS [n = 10]), Group 2: Sham TBS Combination (Real VOR + Sham TBS [n = 10]). The participants will be blinded to the treatment allocation until all study materials had been collected at the end of the study. All patients will be required to complete an intake questionnaire, a Hospital Anxiety and Depression Scale (HADS), the Beck’s Depression Inventory (BDI), a Dizziness Handicap Inventory (DHI), a Misery Scale and a Visual Analogue Scale (VAS) questionnaire. They will also be required to complete a symptom diary one week before and four weeks after treatment week, and will have a follow-up 4 months later. The results from the diary data will indicate how effective the treatments are on reducing primary perceptual symptom levels and secondary symptoms in MdDS patients. Posturography will be measured each day of the treatment week, this is how we will monitor adherence to the intervention, and this data will indicate how effective the two treatments are on improving posture. TBS Treatment For TBS, one site on the head will be stimulated at each session. Each session will be repeated five times per day. The total treatment will comprise 20 stimulation sessions over 4 days. Determining Motor Threshold: Before the start of the treatment, the active motor threshold will be determined. This procedure helps the investigator decide what strength of magnetic stimulation is appropriate for each patient. They will sit in a chair and be asked to keep their head still during the stimulation procedures. Surface electrodes (wires) will be attached with tape to the skin over the muscles of their hands. A coil will be placed over their head and single magnetic pulses will be used to stimulate their brain in the area that controls their hand muscles. The intensity of the stimulation will be raised or lowered gradually until the level at which a muscle barely twitches in their hand is found. This part of the procedure will take between 10 and 15 minutes. Actual TBS procedure: The investigator will continue to monitor activity in the muscles of the patient’s hands. The coil will be positioned over a part of their head and intermittent TBS (iTBS) will be used to stimulate the brain region. At each location, the stimulation will last approximately 2 minutes. There will be a 10-minute break between each stimulation. The total duration of this procedure per day will be about 1 hour. We will use iTBS, in which 600 pulses will be applied in bursts of three pulses at 50 Hz, repeated five times per second, for a total of 40 s and repeated after a 20-second break. Patients will therefore receive a total of 1200 pulses per session. Five sessions will be repeated each day (20 sessions total across 4 days). This technique has been demonstrated to reduce neural activity for at least 1h (Huang et al., 2005). Patients will be stimulated at 80% of their active motor thresholds; those in the sham condition were stimulated at 10% of their active motor thresholds (Holbrook et al., 2016). Participants in Group 2 will be given the sham TBS treatment. The sham TBS treatment will be administered by an experienced operator who will not be involved in participant recruitment and will not meet the participants beforehand. One treatment session per day of iTBS will be administered over one target site (Dorsolateral Prefrontal Cortex), they will be stimulated at 40% of their active motor threshold instead of 80% maximum stimulator output. The main risk involved in TBS is a possibility of triggering seizures. Because of this risk, safety procedures have been established that specify the safe duration of iTBS at the intensities and frequencies to be used in this study. The investigator wishes to minimise the risk to subjects participating in this study. Therefore, we will be using TBS duration of 25% less than the amount used in traditional protocols to provide an additional margin of safety (Oberman et al., 2011). VOR Treatment All patients will undergo four consecutive days of optokinetic (OKN) stimulation while seated in a chair in a darkened OKN drum, specifically built for the experiment. A full-field OKN visual stimulus will be projected on the drum walls, filling the visual field of the patient, including peripheral vision. Patients will be seated at 60 cm from the wall of the drum. During the treatment, the OKN stripes will move with a speed of 10°/sec. The patients are required to stare passively at the stripes. The patient’s head will be rolled at a constant frequency of 0.165 Hz by the researcher with the help of a metronome. During the four days of treatment, patients will up to 5 sessions per day, each session lasting up to 4 minutes. A 2-10 minute interval will be provided between each session of OKN stimulation. Patients will follow a standardised protocol. Patients will follow the same number of sessions within all groups. However, the patient will have the right to stop at any moment.