Effects of persistent Mal de debarquement syndrome on balance, psychological traits, and motor cortex exctiability

Mal de debarquement syndrome (MdDS) is a poorly characterized and understood disorder of perceived motion. We sought to characterize postural control and the psychological impact of MdDS. Additionally, we explored whether patients with MdDS exhibit altered corticospinal and intracortical excitability. In a case-control study we compared patients with MdDS to age- and sex-matched controls (n=8/group). Postural stability (σr) was quantified from plane phase plots based on center or pressure, and psychological indices of depression, fatigue and kinesiophobia were obtained. Transcranial magnetic stimulation (TMS) was used to assess corticospinal excitability by quantifying the motor evoked potential (MEP) amplitude of the flexor carpi radialis, and intracortical excitability was assessed by quantifying indices of intracortical facilitation (ICF), and short-interval and long-interval intracortical inhibition using a paired-pulse TMS paradigm. The patients with MdDS exhibited greater mean (±standard error of the mean) σr during semi-tandem stance (10.9 ± 1.5 compared to 7.1 ± 0.7, p=0.04), higher levels of kinesiophobia (41.6 ± 2.8 compared to 27.3 ± 2.2), and higher levels of fatigue (27.0 ± 4.1 compared to 48.4 ± 1.0). Patients with MdDS exhibited a higher mean motor threshold (MT) (58.1 ± 2.5 compared to 47.4 ± 2.7% of stimulator output), and larger MEP (13.1 ± 3.1 compared to 5.1 ± 1.2% of maximal compound muscle action potential) but there was no difference in measures of intracortical excitability. These findings suggest that patients with MdDS exhibit impaired postural stability, and high levels of kinesiophobia and fatigue. Additionally, we observed that patients with MdDS exhibit higher MT and large MEP amplitudes, but do not exhibit differences in measures of intracortical excitability, compared to controls. These findings help characterize MdDS, and provide insight into the physiology of MdDS.