Disproportionately Enlarged Subarachnoid Space Hydrocephalus (DESH) Identified on I-123 Ioflupane SPECT/CT.

A patient with gait instability underwent I-123-ioflupane SPECT/CT imaging for suspected Parkinson's disease. DaTQUANT analysis was negative for Parkinson's disease; however, evaluation of the SPECT images revealed low counts within the bilateral parietal region. Further review of the CT images demonstrated the classic appearance of disproportionately enlarged subarachnoid space hydrocephalus (DESH), a supportive imaging feature of idiopathic normal pressure hydrocephalus (iNPH), highlighting the importance of correlation of cross-sectional CT and DaT SPECT imaging.