Table 1:

Differential diagnoses for normal pressure hydrocephalus, their key clinical and distinguishing diagnostic features

Differential diagnosis	NPH triad			Other key clinical features	Distinguishing imaging or investigational features
Differential diagnosis	Progressive dementia	Gait disturbance	Urinary incontinence	Other key clinical features	Distinguishing imaging or investigational features
Alzheimer disease	+++	+	+	Early amnesia Aphasia, anomia, apraxia Behavioural and mood disorders	Hydrocephalus ex vacuo Medial temporal lobe atrophy Temporoparietal cortical atrophy
Vascular dementia	+++	++	−	Vascular risk factors and events Post-stroke dementia Gait base is narrower and more closely resembles the parkinsonian gait	Hydrocephalus ex vacuo Prominent microvascular changes Evidence of stroke
Dementia with Lewy bodies	+++	++	+	Parkinsonian signs Fluctuating cognitive status Psychosis (i.e., visual hallucinations) RBD	Hydrocephalus ex vacuo (cortical atrophy)
Parkinson disease dementia	++	+++	+	Parkinsonian signs Nonmotor features (RBD, constipation, mood disorders, hyposmia)	Hydrocephalus ex vacuo (cortical atrophy)
Progressive supranuclear palsy	++	+++	+	Supranuclear ophthalmoplegia Axial rigidity Early falls Dysphagia, dysarthria	Midbrain atrophy (hummingbird sign)
Multiple system atrophy	+	++	+++	Parkinsonian or cerebellar signs Dysautonomia (orthostasis, impotence, constipation) Inspiratory stridor RBD	Putaminal atrophy Disproportionate atrophy of the cerebellum and brain stem Loss of pontocerebellar fibres (hot cross bun sign)
Corticobasal syndrome	+++	++	+	Asymmetric parkinsonism Limb dystonia Limb myoclonus Alien limb phenomena Asymmetric cortical sensory loss	Hydrocephalus ex vacuo Asymmetric cortical atrophy Atrophy of the corpus callosum or basal ganglia
Autoimmune encephalitis	+++	+	−	Various neurologic manifestations depending on the autoantibody (sleep disorders, seizure, movement disorder, neuropsychiatric symptoms, etc.)	Abnormal EEG, CSF and autoimmune serum markers Signal hyperintensities in MRI in affected brain regions
Infectious encephalitis	+++	+	−	Infectious prodrome or symptoms (e.g., headache, fever, malaise) Meningismus Behavioural abnormalities Focal neurologic deficits Seizure	Abnormal CSF markers Signal hyperintensities in MRI in affected brain regions or brain abscess
Prion disease (i.e., Creutzfeldt–Jakob disease)	+++	+++	−	Behavioural abnormalities (e.g., apathy, mutism, catatonia) Aphasia, apraxia Myoclonus Cerebellar manifestations Extrapyramidal and pyramidal signs	Abnormal EEG and CSF markers Signal hyperintensities in MRI (caudate nucleus, cortical ribboning)
Musculoskeletal disorders	−	++	+/−	Limited range of motion Radicular pain Back or joint pain	Abnormal spine or pelvis imaging (e.g., degenerative disc, herniated disc, osteoarthritis) Normal brain imaging
Peripheral neuropathy	−	++	−	Sensory ataxia Sensory deficits	Abnormal electrodiagnostic studies Normal imaging

Note: CSF = cerebrospinal fluid, EEG = electroencephalogram, MRI = magnetic resonance imaging, NPH = normal pressure hydrocephalus, RBD = rapid eye movement sleep behaviour disorder.