Correlation of Midbrain Diameter and Gait Disturbance in Patients with Idiopathic Normal Pressure Hydrocephalus

ABSTRACT

BACKGROUND: While gait disturbance is an important feature of idiopathic normal pressure hydrocephalus (NPH), there are only tentative theories explaining its pathophysiology. The mesencephalic locomotor region has been suggested as the anatomical substrate for the development of hypokinetic gait. We evaluated the correlation between gait disturbance and midbrain diameter to investigate the role of mesencephalic locomotor region in development of NPH gait. METHODS: We enrolled 21 patients with NPH and 20 age-matched control subjects. Maximal diameter of midbrain and pons and the width of lateral and third ventricle were measured at midsagittal T1-weighted MRI and axial T2-weighted MRI, respectively. Gait disturbance, cognitive dysfunction, and incontinence were semi quantified. RESULTS: Maximal midbrain diameter was significantly smaller in NPH group, as compared to the controls (14.8 +/- 0.9 vs. 17.1 +/- 0.7 mm, p<0.001). There was an inverse correlation between the midbrain diameter and the ventricular width (r=-0.562, p=0.008 in third ventricle and r=-0.510, p=0.018 in lateral ventricle). Severity of gait disturbance were negatively correlated with midbrain diameter (r=-0.598, p=0.004), but degree of cognitive dysfunction and incontinence showed no significant correlation with brainstem diameter nor ventricular width. CONCLUSIONS: This study suggests that midbrain atrophy is significantly associated with gait disturbance in NPH. Furthermore, this study implies the possible role of midbrain structures including mesencephalic locomotor region in the genesis of NPH gait.