Differentiation of Idiopathic Normal Pressure Hydrocephalus from Alzheimer's Disease Using Easy Z-score Imaging System (eZIS) Seiju KOBAYASHI 1 , Kumiko UTUMI 2 , Masaru TATENO 1 , Hidetoshi MORII 3 , Toshikazu SAITO 1 1Department of Neuropsychiatry, Sapporo Medical University, Sapporo, Japan 2Department of Psychiatry, Sunagawa City Medical Center 3Department of Radiology, Sunagawa City Medical Center Keyword: idiopathic normal pressure hydrocephalus , iNPH , Alzheimer's disease , AD , Brain perfusion , SPECT , easy Z-score imaging system , eZIS , Two tail view pp.533-539
Published Date 2009/6/15
DOI https://doi.org/10.11477/mf.1405101435
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 Idiopathic normal pressure hydrocephalus (iNPH) is characterized by the clinical triad of cognitive impairment, gait disturbance, urinary incontinence, and ventricular enlargement with normal cerebrospinal fluid (CSF) pressure. In iNPH cases that do not present some of these characteristic symptoms, it is difficult to distinguish between iNPH and other medical conditions such as Alzheimer's disease (AD). In order to increase the accuracy of the clinical diagnosis of iNPH, we performed 99mTc-ethylcysteinate dimer (ECD) brain perfusion single photon emission computed tomography (SPECT) and analyzed the results using an easy Z-score imaging system (eZIS). Thirteen patients diagnosed with iNPH on the basis of the diagnostic guideline (8 definite and 5 probable) and 10 probable AD diagnosed according to the NINCDS-ADRDA with prominent ventriculomegaly underwent ECD-brain perfusion SPECT. A two-tail view of analysis eZIS demonstrated a distinct two-layered structure with decreased blood flow in the cingulate gyrus and enhanced perfusion in the exterior region of this layer in the sagittal view in iNPH, cases:however, similar findings could not be observed in AD cases. The possible explanation for such a finding with respect to iNPH cases could be the insufficient anatomical standardization of SPECT images and consequent false-positive result observed as hypoperfusion in the cingulate gyrus in the two-tailed view of eZIS analysis due to the marked enlargement of the ventricle. Enhanced blood perfusion at the outer layer of the hypoperfusion area was caused by increased RI count per volume due to the exclusion of the cerebral cortex by the dilated ventricle. Our results suggest that two-tail view of brain perfusion SPECT using eZIS analysis could prove to be a useful support tool for the diagnosis of iNPH.

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