Severity of restless legs syndrome is inversely correlated with echogenicity of the substantia nigra in different neurodegenerative movement disorders. A preliminary observation

Abstract

Objective: To verify whether the presence and severity of restless legs syndrome (RLS) is correlated with substantia nigra (SN) echogenicity, in Parkinson’s disease (PD) and Machado-Joseph disease (MJD) patients. Background: Hyperechogenicity of the SN is a frequent observation on TCS in PD and MJD patients. Additionally, RLS is a sleep disorder that is also frequently found in both diseases. Autopsy studies have demonstrated increased iron content in hyperechogenic SN. Iron storage is also known to be involved in RLS. Methods: A total of 120 subjects were recruited, divided into five groups: 20 MJD patients with RLS, 17 MJD without RLS, 10 PD patients with RLS, 10 PD without RLS, and 63 healthy subjects. RLS was ascertained based on a clinical face-to-face interview. Severity of RLS was assessed by applying the International RLS Rating Scale. TCS was performed through temporal acoustic bone window on both sides by applying a phased-array ultrasound system e quipped with a 5-1 MHz transducer. Results: Significant differences were seen among groups, with a general continuum in mean TCS echogenicity throughout the SN (Figure 1). Pearson’s test for L and R SN areas of echogenicity versus severity of RLS yielded significant inverse correlations among groups (Rp L-SN 5-0.568; p<0.001 and Rp R-SN 520.545; p< 0.001) (Figure 2). No significant correlations were detected for the presence of RLS and SN echogenicity. Conclusions: The present study confirmed that severity of RLS can be influenced by SN echogenicity in PD and MJD patients. This data allows us to suppose that echogenicity of the SN partially explains pathophysiological aspects of RLS in PD and MJD patients. Fig. 1 (1226). Box plots showing substantia nigra (SN) mean area of echogenicity in patient groups with Parkinson’s disease (PD) without restless legs syndrome (RLS), PD with RLS, Machado-Joseph disease (MJD) without RLS, MJD with RLS, and in healthy control group. *indicates outliers. Fig. 2 (1226). Pearson’s correlation test between severity of Restless Leg Syndrome (RLS) in Parkinson’s disease (PD) and in Machado-Joseph disease (MJD) for left and right SN areas of echogenicity.