Camptocormia is characterized by an excessive anterior flexion of the spine that appears only when standing or walking. The origin of this symptom remains unknown, but recent clinical reports of camptocormia associated with Parkinson's disease (PD) suggest cerebral involvement in the pathogenesis of camptocormia. This study was undertaken to investigate the hypothesis that camptocormia in PD has a central origin. Seventeen PD patients with camptocormia were prospectively enrolled and were compared to 10 matched PD patients without camptocormia and 12 normal controls. The normalized volumes of the brain, striatal nuclei, and the cross-sectional areas of the midbrain and pons were measured on three-dimensional magnetic resonance imaging. Data were correlated with the severity of the symptoms. The normalized axial surface of the midbrain was statistically smaller in PD patients with camptocormia than in normal controls (P = 0.01). The normalized volumetric data were not statistically different in PD patients with camptocormia. There was a significant negative correlation between the severity of camptocormia and the normalized brain volume (P < 0.009; R = -0.649) and sagittal pons area (P < 0.01; R = -0.642). The results suggest that PD with camptocormia may represent a selective form of PD in which a specific neuronal dysfunction possibly occurs within the brainstem.