Diffusion tensor imaging in elderly patients with idiopathic normal pressure hydrocephalus or Parkinson’s disease: diagnosis of gait abnormalities

The study involved 10 patients with INPH, 18 with PD, and 10 healthy individuals (control group). Fractional anisotropy (FA) of five brain areas was measured and compared among the three groups. In addition, the association of INPH and PD with gait capability, frontal lobe function, and FA of each brain area was evaluated.The INPH group had significantly lower FA for anterior thalamic radiation (ATR) and forceps minor (Fmin) as compared to the PD group. The gait capability correlated with ATR FA in the INPH and PD groups. We found that adding DTI to the diagnosis assisted the differential diagnosis of INPH from PD, beyond what could be inferred from ventricular size alone.We expect that DTI will provide a useful tool to support the differential diagnosis of INPH and PD and their respective severities.Idiopathic normal pressure hydrocephalus (INPH) is a syndrome which involves cognitive disorder, gait abnormalities, and urinary incontinence. INPH was first reported in 1965 by Hakim and Adams as a condition whose symptoms could be alleviated by a cerebrospinal fluid shunt [1]. In the past, patients with suspected INPH were frequently misdiagnosed. This over-diagnosis resulted in many unsuccessful surgeries or the development of postoperative complications and as a result, less attention was paid to INPH [2]. Under these conditions, three epidemiological studies were conducted on INPH, enabling estimation of its prevalence. The study by Hiraoka et al. found that 2.9% of community-dwelling elderly subjects showed radiological and clinical features consistent with INPH [3]. Using a similar procedure, Tanaka et al. reported possible INPH prevalence to be 1.4% [4] and Iseki et al. reported the prevalence of possible INPH to be 0.5%. Because symptoms appeared 4–8？years later in some of the initially symptom-free cases, the authors suggested the possibility that changes revealed by diagnostic imaging represent a precursor condition and proposed the concept “asymptomatic vent