Vibrotactile perception depends on cognition not just peripheral nerve integrity: a cross-sectional study

Background: Vibration perception is often considered a peripheral nerve and dorsal column function, without considering the role of cognition. The current study tested cognition’s role in vibrotactile perception thresholds (VPT). Methods: We recruited cases with mild-moderate dementia or mild cognitive impairment thought to reflect probable Alzheimer’s pathology (AD/MCI group), and controls without memory concerns (all participants >50 years). Polyneuropathy, B12 deficiency, diabetes, or other conditions associated with cognitive impairment were exclusionary criteria. Participants underwent cognitive evaluation with the Self-Administered Gerocognitive Examination (SAGE), standardized nerve conduction studies, and quantitative VPT testing. Demographic and medical history were obtained through interview and chart review. We constructed linear regression models to test whether poor cognition correlates with VPT. Results: Nineteen AD/MCI participants (age 71.5±8.9, 47.4% female) and fourteen controls (age 67.4±9.3, 78.6% female) did not differ on age or gender. Univariate predictors of poor/increased mean VPT (all p­-values <0.10) were age, AD/MCI, SAGE score, sural sensory nerve action potential (SNAP) amplitude <5 microvolts, yearly income <$50,000, history of vascular disease, and peroneal motor and sural conduction velocity (CV). SAGE score (standardized β=-0.38, p<0.01); sural SNAP amplitude (β=0.51, p<0.001); peroneal motor CV (β=-0.37, p<0.01), history of vascular disease (β=0.27, p=0.03), and female gender (β=0.22, p=0.10) remained independently associated with VPT in multivariable linear regression analysis (backwards modeling; removal criteria p>0.10; model adjusted R2=0.66; p<0.001). Conclusions: Poor cognition is associated with worsened VPT. Neurologists should consider cognition when using sensory perception to assess peripheral nerve integrity, both for research and during a traditional neurologic examination.