Parkinson's disease-like midbrain hyperechogenicity is frequent in amyotrophic lateral sclerosis

Clinical and neuroimaging data suggest impairment of the nigrostriatal system in amyotrophic lateral sclerosis (ALS). We thus hypothesized whether Parkinson's disease (PD)-like midbrain sonography findings are also present in ALS. Eighty-six patients with the diagnosis of possible or definite ALS according to revised El Escorial criteria were examined by transcranial B-mode sonography compared to 76 age- and gender-matched controls and 33 PD patients. Hyperechogenic areas of the midbrain representing the substantia nigra were measured planimetrically using standard protocols. In subjects with sufficient temporal acoustic bone windows, mean midbrain hyperechogenic areas were significantly higher in ALS (0.251 ± 0.104 cm(2)) and PD patients (0.286 ± 0.078 cm(2)) compared to controls (0.091 ± 0.054 cm(2)) with no significant difference between ALS and PD patients (one-way ANOVA: F value = 94.3; P < 0.0001). Sixty-seven percent (95 % CI 57-78 %) of ALS patients and 84 % (95 % CI 71-97 %) of PD patients displayed abnormal midbrain hyperechogenic areas (P = 0.383 for group comparison, χ(2) test). No correlations of hyperechogenic area sizes in ALS patients were found in regard to age, gender, ALS subtype (bulbar versus spinal form) or ALS-FRS-R score. In summary, we observed hyperechogenicity of the substantia nigra in patients with sporadic ALS with a frequency similar to that in PD and higher than in all other movement disorders. These findings are important for the diagnosis and differential diagnosis of PD and ALS alike.