Flattened facial colliculus on magnetic resonance imaging in Machado-Joseph disease

Atrophy of the pontine tegmentum and facial colliculus is a characteristic pathological feature of Machado-Joseph disease. We assessed whether this finding can be detected by conventional brain magnetic resonance imaging. A total of 17 patients with genetically confirmed Machado-Joseph disease, 15 disease controls (spinocerebellar ataxia type 6 and dentatorubral-pallidoluysian atrophy), and 17 normal subjects were examined using a 1.5-Tesla magnetic resonance imaging scanner. The widths of the facial colliculus, pontine tegmentum, and pontine base and the area of the fourth ventricle were measured on axial T2-weighted imaging. Pathological examination was performed in 9 Machado-Joseph disease patients. In addition, visual inspection of the facial colliculus was evaluated by receiver operating characteristic analysis. The width of the facial colliculus was significantly smaller in Machado-Joseph disease patients (0.37 ± 0.16 mm; mean ± standard deviation) than in normal subjects (0.73 ± 0.30 mm; P < .01), whereas the width of the pontine tegmentum was smaller in both Machado-Joseph disease (4.85 ± 0.58 mm) and dentatorubral-pallidoluysian atrophy (4.72 ± 0.59) patients than in normal subjects (6.35 ± 0.74 mm; P < .01). Visual evaluation of the facial colliculus showed sufficient area under the receiver operating characteristic curves to differentiate Machado-Joseph disease from dentatorubral-pallidoluysian atrophy (0.78) and spinocerebellar ataxia type 6 (0.87). Pathological evaluation showed significant atrophy of the facial colliculus in all Machado-Joseph disease patients. Atrophy of the facial colliculus is a feasible magnetic resonance imaging finding for diagnosing Machado-Joseph disease, and it is easily found as a flattening of the fourth ventricular floor.