Establishing the Relationship of Quantitative Vibratory Sensation and Sensory Cortical Areas in Multiple Sclerosis

Background: Sensory impairment significantly impacts individuals with multiple sclerosis with more than 80% reporting sensory symptoms within 1-year of diagnosis. Vibratory sensation may serve as a sensitive proxy for proprioceptive function and balance. Understanding the relationship of quantitative vibratory sensation with brain pathology will assist with the development of a reliable outcome measure for sensory loss.

Objectives: Our objective was to establish a cortical structural substrate for vibration sensation. We hypothesized that our quantitative measure of vibratory sensation would be associated with volume or grey matter thickness in primary and secondary sensory cortices.

Methods: Eighty-four individuals with multiple sclerosis (n=54 relapsing and n=30 progressive) participated in vibratory sensation testing of the great toe (Vibratron II) and a 3T MRI (FLAIR and MPRAGE) evaluating volume and cortical thickness of the primary and secondary sensory cortices.

Results: After controlling for age, gender and disability level, vibratory sensation was significantly related to cortical thickness of the paracentral gyrus (p=0.034) and marginally related to normalized thalamic volume (p=0.072). Within the progressive disease subtype, there were significant relationships between vibratory sensation impairment and thalamus volume (ß=-0.00002; p=0.01) as well as reduced cortical thickness in the cingulate cortex (ß=-0.008; p=0.04), precentral gyrus (ß=-0.003; p=0.01), paracentral gyrus (ß=-0.003, p=0.045), and inferior frontal gyrus pars triangularis (ß=-0.004, p=0.019) and pars opercularis (ß= -0.004; p=0.016).

Conclusions: Quantitative measurement of vibratory sensation reflects pathological changes in spatially distinct brain areas and may supplement information captured by global brain atrophy measures. Without overt relapses, monitoring decline in progressive forms of multiple sclerosis has proved challenging; quantitative vibratory sensation measurement may provide a tool to examine pathological decline in this cohort. Quantitative vibratory sensation may be a useful tool for monitoring the efficacy of pharmacologic interventions and for developing targeted treatments for individuals with progressive multiple sclerosis.