Can normal pressure hydrocephalus (NPH) cause loss of consciousness?

Normal Pressure Hydrocephalus Does Not Typically Cause Loss of Consciousness

Normal pressure hydrocephalus (NPH) characteristically presents with gait disturbance, dementia, and urinary incontinence—but not loss of consciousness. The condition is defined by the absence of signs of increased intracranial pressure such as nausea, vomiting, or altered consciousness 1.

Classic Clinical Presentation

The hallmark triad of NPH consists of:

• Gait disturbance (the cardinal and earliest sign, described as "magnetic" or appearing as if feet are glued to the floor) 2, 3
• Cognitive impairment/dementia (mild to moderate mental deterioration) 2, 4
• Urinary incontinence (urgency, frequency, and incontinence) 2, 3

Importantly, nausea, vomiting, and signs of increased intracranial pressure do not occur in NPH 1. The mean basal intracranial pressure remains normal or only mildly elevated 2.

When Hydrocephalus DOES Cause Decreased Consciousness

Loss of consciousness occurs with hydrocephalus only in specific acute contexts that differ fundamentally from NPH:

• Acute hydrocephalus with significantly elevated intracranial pressure (pressures ≥250 mm H₂O) in conditions like coccidioidal meningitis or intracerebral hemorrhage requires urgent intervention 5
• Spontaneous intracerebral hemorrhage with intraventricular extension causing acute hydrocephalus can lead to decreased level of consciousness, warranting ventricular drainage 5
• In these acute scenarios, ventricular drainage should be performed when hydrocephalus contributes to decreased consciousness to reduce mortality 5

Critical Distinction: NPH vs. Acute Hydrocephalus

The key differentiator is that NPH develops insidiously over time with normal CSF pressure, whereas loss of consciousness occurs only with acute hydrocephalus and significantly elevated intracranial pressure 2, 1. One case report documented a patient with concealed NPH who developed drowsiness only after anesthesia-related complications, not from the NPH itself 1.

Differential Diagnosis Considerations

If a patient presents with apparent loss of consciousness, consider:

• Seizures: Loss of consciousness typically lasts 74-90 seconds with eyes open, tongue biting (lateral), and oral automatisms 6
• Syncope: Brief loss of consciousness (<30 seconds) due to cerebral hypoperfusion, requiring only 6-8 seconds of cessation of cerebral blood flow 5
• Other causes of altered mental status in the context of NPH may indicate concurrent pathology, as 75% of NPH patients requiring treatment have another neurodegenerative disorder 2

Clinical Implications

If a patient presents with the radiological appearance of hydrocephalus AND loss of consciousness, this is NOT typical NPH and warrants investigation for acute processes such as intracerebral hemorrhage, acute obstructive hydrocephalus, or other causes of elevated intracranial pressure 5, 1. The presence of decreased consciousness should prompt consideration of ICP monitoring and urgent neurosurgical consultation 5.

NPH remains a treatable condition when recognized early, with 70-90% of patients showing clinical improvement after ventriculoperitoneal shunt placement, but the diagnosis requires the characteristic triad without loss of consciousness 2.