Reduced cerebral blood flow of lingual gyrus associated with both cognitive impairment and gait disturbance in patients with idiopathic normal pressure hydrocephalus

Idiopathic normal pressure hydrocephalus (iNPH) is primarily characterized by cognitive impairment and gait disturbance. Our objective was to evaluate the clinical characteristics of iNPH and the association between cerebral blood flow (CBF), measured using single-photon emission computed tomography (SPECT), and both cognitive and gait disturbances in iNPH patients.We compared cognitive and motor functions and neuroimaging findings between 29 iNPH patients and 35 age-matched Parkinson's disease (PD) patients. We examined the associations between cognitive and motor dysfunctions and CBF in iNPH patients using 99mTc-ECD SPECT subtraction imaging data from a database of healthy control subjects.The cognitive function of iNPH patients, as measured by the Mini-Mental State Examination (MMSE) and Frontal Assessment Battery (FAB), was significantly poorer than that of PD patients; however motor function of the legs based on the Unified PD Rating Scale (UPDRS) part III was similar across groups. Impairment in cognitive function based on the MMSE and FAB was significantly correlated with motor dysfunction of the legs on the UPDRS part III and the 3-m Timed Up and Go test. Furthermore, 99mTc-ECD SPECT subtraction imaging revealed lower CBF in the bilateral lingual gyrus of iNPH patients with severely impaired cognitive and motor functions than healthy control subjects.Patients with iNPH have severely impaired cognitive function; however, motor dysfunction of the legs is similar to PD patients. The cognitive and gait disturbances of iNPH are significantly interrelated, which may be associated with an impaired brain network that includes the bilateral lingual gyrus.