Optokinetic Stimulation in Mal de Debarquement Syndrome: Case Report

Mal de Débarquement Syndrome (MdDS) is a rare neuro-otological disorder characterized by a persistent perception of self-motion, typically described as rocking, swaying, or bobbing sensations, following exposure to passive motion such as sea, air, or land travel. The syndrome can significantly impair balance, spatial orientation, and quality of life. Conventional therapeutic approaches are limited, and symptoms may persist for weeks, months, or even years. Recent studies have suggested that maladaptation of the vestibulo-ocular reflex (VOR) and velocity storage mechanisms may play a central role in the pathophysiology of MdDS.

In this single-case study, a 28-year-old female patient with a clinical diagnosis of MdDS will undergo an online OKS-based rehabilitation program. The intervention will be conducted remotely via the Smart Optometry application, using the "OKN Stripes" module to deliver full-field optokinetic visual stimulation. The participant will sit close to the screen, ensuring that the optokinetic stripes occupy approximately 85-90% of the visual field. The researcher will guide each session online, ensuring the synchronization of head roll movements with the visual stimuli using a metronome (10 bpm). The intervention will be implemented for 3-5 consecutive days, with two sessions in the morning and two in the afternoon, each lasting 4 minutes.

Assessment and Follow-up: Clinical outcomes are evaluated at multiple time points to monitor the progression and long-term sustainability of the treatment:

Baseline (T0): Pre-treatment assessment. Post-treatment (T1): Immediately following the 5-day protocol. Short-term Follow-up (T2): 1 month after treatment. Long-term Follow-up (T3): 1 year after treatment to evaluate the durability of neuroplastic changes.

Primary metrics include the Dizziness Handicap Inventory (DHI) for perceived disability, the Visual Analog Scale (VAS) for dizziness intensity, and the Istanbul MdDS Scale for syndrome-specific symptoms. To determine the patient's clinical profile and support differential diagnosis, the Motion Sickness Susceptibility Questionnaire - Short Form (MSSQ-SF) will be administered initially.

This study aims to contribute to the limited clinical evidence on non-invasive, visual-vestibular rehabilitation strategies for MdDS and to explore the feasibility of delivering optokinetic therapy in an online, remote setting.

• Optokinetic stimulation (Other): The planned optokinetic stimulation (OKS) application will be implemented. The application will last for 5 consecutive days, with a total of 4 sessions, two in the morning and two in the afternoon. Each session will last 5 minutes, and head turns will be synchronized with a metronome at 10 beats per minute (10 bpm). Each beat will complete a full right-left cycle, achieving a frequency of approximately 0.167 Hz. This arrangement reflects the standardized protocol recommended in the literature. The application will be conducted online, and the participant will use the "Optokinetic nystagmus (OKN) lines" section within the "Smart Optometry" application on their computer. The direction of the lines will move in the direction opposite the patient's dominantly affected side. The participant was seated close to the screen, and approximately 85-90% of their visual field covered by the moving stimuli.

Primary outcomes

• Level of Disability [From enrollment (baseline) until the final follow-up, assessed at multiple time points: baseline, immediately post-treatment (day 5), 1 month, and 1 year.]: Dizziness Handicap Inventory: Provides information about disability and quality of life in individuals with vestibular disorders. The scale assesses the functional, physical, and emotional effects of dizziness on disability over the past month. It consists of 25 questions, 9 functional, 7 physical, and 9 emotional, with three answer options: yes (4 points), sometimes (2 points), and no (0 points). A total score is calculated along with the scores for each subsection. The total score ranges from 0 to 100, with higher scores indicating greater disability. According to the total score, the level of disability is classified as follows: 16-34 points as mild; 36-52 points as moderate; and 54 and above as severe. This scale, whose
• Istanbul Mal de Debarquement Scale [From enrollment (baseline) until the final follow-up, assessed at multiple time points: baseline, immediately post-treatment (day 5), 1 month, and 1 year.]: The scale is composed of subfactors to better assess MdDS. The scale consists of four subfactors: "Diagnostic Criteria" (items 1-5), "Dizziness Character" (items 6-9), "Visual Movement Intolerance" (items 10-12), and "Quality of Life" (items 13-18). The scale was designed using a 5-point Likert-type scale, using the terms "Always," "Frequently," "Sometimes," "Rarely," and "Never." These statements were scored from 5 to 1, respectively. The total scale score was calculated as 100. Permission was obtained from the scale's author for use.
• Dizziness Severity [From enrollment (baseline) until the final follow-up, assessed at multiple time points: baseline, immediately post-treatment (day 5), 1 month, and 1 year.]: Visual Analog Scale: The participant's dizziness intensity was assessed on a scale between 0 and 10-cm line, where 0 represents "no vertigo/dizziness," and 10 represents "extreme dizziness. Scores are categorized as mild (2-3), moderate (4-5), severe (6-7), quite severe (8-9), and extreme.

Sex: Female

Inclusion Criteria:

* Subjective perception of movement in the "rocking/bobbing/swaying" type, beginning after exposure to passive motion (sea/aircraft/vehicle, etc.),
* lasting ≥1 month,
* Temporary relief of symptoms upon re-exposure to passive motion,
* Findings not better explained by an alternative diagnosis.
* Head and neck health must be at a level that allows head roll movement during optokinetic stimulation (no serious cervical limitation).

Exclusion Criteria:

* Alternative vestibular/otologic diagnoses: active BPPV, Meniere's disease, acute vestibular neuronitis, significant peripheral vestibulopathy; or significant central cause (stroke, CNS lesion, etc.).
* History of photosensitizer epilepsy or uncontrolled epilepsy

• Görkem ATA, Ph.D., Principal investigator, Medipol University