Table 1.

American/European (Relkin et al., 2005) and Japanese (Nakajima et al., 2021) criteria for probable idiopathic normal pressure hydrocephalus.

	American/European	Japanese
Clinical	Gait/balance disturbance One impairment involving either cognition or urination	More than one symptom in the clinical triad: gait disturbance, cognitive impairment, and urinary incontinence
Historical	Insidious onset of symptoms with progression over time Age >40 years at symptom onset Symptom duration for at least 3–6 months No previous insult which could lead to secondary hydrocephalus No other neurologic, psychiatric, or medical cause for symptoms	Age ≥60 years No obvious preceding diseases causing ventricular dilation (e.g., subarachnoid hemorrhage, meningitis, head injury) Clinical symptoms not completely explained by other neurological or non-neurological disease.
Investigational	Ventricular enlargement without macroscopic obstruction with Evans Index >0.3 At least one of the following features: 1. Enlargement of temporal horns without hippocampal atrophy 2. Callosal angle of ~90 degrees or less 3. Evidence of altered brain water content including periventricular signal changes 4. Aqueductal or fourth ventricular flow void seen on MRI CSF opening pressure on lumbar puncture between 5–18 mmHg (70–245 mmH2O)	Ventricular enlargement with Evans Index >0.3 CSF opening pressure ≤200 mm H2O, normal CSF content One of the following two features: 1. Neuroimaging features of narrowing of the sulci and subarachnoid space over the high convexity/midline surface (DESH) with gait disturbance: small stride, shuffle, instability during walking, and increase in instability on turning 2. Improvement of symptoms after CSF tap test and/or drainage test