Phalanx sign helps to discriminate MSA-C from idiopathic late onset cerebellar ataxia

Introduction Early diagnosis of MSA-C in patients with late-onset cerebellar ataxia (LOCA) may prove difficult. We therefore describe and evaluate the performance of the new phalanx sign (PS), that should be looked for during the nose-finger test to distinguish MSA-C from idiopathic late-onset ataxia (ILOCA). Methods Sensitivity, specificity, positive predictive value, negative predictive value and interrater reliability of PS were assessed in three groups: 21 MSA-C, 23 ILOCA and 20 age-matched healthy subjects. Results PS was positive for 61.9% of MSA-C patients', 4.3% of ILOCA patients' and in none of healthy subjects' evaluations. PS discriminated MSA-C from ILOCA (p < 0.001) with a sensitivity of 61.9%, a specificity of 95.7%, a positive predictive value of 92.9%, a negative predictive value of 73.3% and a substantial interrater reliability (Kappa = 0.7273). Conclusion PS could be a helpful, easy and reproducible sign for the early diagnosis of MSA-C in patients with LOCA.

Automated summary

This study describes and evaluates the performance of the phalanx sign (PS) in distinguishing MSA-C from ILOCA. The results show that PS can be a helpful sign for the early diagnosis of MSA-C in patients with LOCA.