Tongue strength in patients with subacute myelo-optico-neuropathy

Subacute myelo-optico-neuropathy (SMON) is a neurodegenerative disease that may be caused by overdose or prolonged oral administration of clioquinol. Recently, dysphagia has attracted attention as a complication of SMON. To investigate lingual control in SMON, we examined patients with SMON using assessments of maximum tongue pressure, compared with dysphagia-related diseases, such as sporadic inclusion body myositis (sIBM) and amyotrophic lateral sclerosis (ALS), and healthy volunteer. The mean maximum tongue pressure (P_max) in patients with SMON was 14.7 ± 5.8 kPa, while it was 33.6 ± 4.4 kPa in the controls. In contrast, the mean P_max for patients with ALS with or without bulbar involvement was 7.8 ± 2.7 kPa and 34.4 ± 5.7 kPa, respectively, while it was 29.4 ± 8.2 kPa in patients with sIBM. P_max values correlated with lower limb weakness in SMON patients. Decreases in P_max may be involved in the development of dysphagia in patients with SMON.