P91-T Neurophysiological assessment of asymptomatic TTRVal50Met carriers (transthyretin amyloid polyneuropathy) from the endemic foci of Mallorca

Hereditary transthyretin amyloidosis (hATTR) is a rare, multisystem disease caused by amyloid deposition, characterized by heterogeneous presentation and symptomatology. Therefore, early diagnosis remains a challenge.For carriers of the most common mutation (Val50Met-TTR variant), axonal sensorimotor polyneuropathy (AxSMP) and small fiber and autonomic neuropathy (SFN) are the main clinical features. Very few studies have used neurophysiological tests for the assessment of SFN and AxSMP in the monitoring of carriers of the Val50Met mutation. However, few alterations that can serve as an alert to identify the possible onset of neuropathy have been identified in asymptomatic carriers. The aim of this project is to evaluate SFN and AxSMP in undiagnosed individuals carrying the TTR Val50Met variant by the assessment of Nerve Conduction Studies, Sympathetic Skin Response, RR variability, QST (thermotest) and Sudoscan. 46 carriers have been included in the study. Baseline evaluation unraveled a low amplitude of the plantar SSR as a frequent finding (14/46) using the cut-off point of 0,2 mV for plantar response. This amplitude is significantly lower than the detected for the control group (n = 20). Prevalence of carpal tunnel syndrome was similar to general population. Study of asymptomatic carriers allowed the diagnosis of two subjects after the first examination. Also, 3 subjects are under suspicion of SFN. Early detection of neuropathy, specially the small fiber and autonomic neuropathy, is essential to improve diagnosis and prognosis of hATTR-PN. A complete neurophysiological test battery is the best approach to detect changes from the basal examination.