Neurology · Dementia
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The classic clinical triad of Normal Pressure Hydrocephalus consists of gait disturbance, urinary incontinence, and dementia.
The gait disturbance is typically the first symptom to appear and is often described as a magnetic gait or apraxic gait.
Normal Pressure Hydrocephalus is a communicating hydrocephalus characterized by ventriculomegaly out of proportion to cerebral atrophy.
Lumbar puncture is the diagnostic test of choice to demonstrate clinical improvement in symptoms following the removal of 30-50 mL of cerebrospinal fluid.
Large-volume lumbar puncture or continuous lumbar drainage serves as a predictive test for the success of surgical intervention.
The definitive treatment for symptomatic Normal Pressure Hydrocephalus is the placement of a ventriculoperitoneal shunt.
Normal Pressure Hydrocephalus is considered a reversible cause of dementia and must be distinguished from Alzheimer disease or Parkinson disease.
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A 74-year-old male is brought to the clinic by his daughter due to progressive cognitive decline and difficulty walking over the past 6 months. She notes that he frequently loses his balance and has developed urinary incontinence. On physical examination, the patient exhibits a wide-based, magnetic gait with feet appearing to stick to the floor. Cognitive testing shows mild impairment in executive function. A non-contrast head CT reveals ventriculomegaly without significant cortical atrophy or sulcal widening.
What is the most appropriate next step in the management of this patient?
Large-volume lumbar puncture
The patient presents with the classic triad of NPH; a large-volume lumbar puncture is the diagnostic test of choice to predict if the patient will respond to a ventriculoperitoneal shunt.
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Etiology / Epidemiology
Primarily affects elderly patients; often idiopathic, but secondary to meningitis, subarachnoid hemorrhage, or trauma.
Clinical Manifestations
Classic Hakim's triad: gait disturbance, urinary incontinence, and dementia.
Diagnosis
Gold standard is large-volume lumbar puncture showing clinical improvement; MRI shows ventriculomegaly out of proportion to atrophy.
Treatment
Definitive treatment is ventriculoperitoneal (VP) shunt; avoid over-shunting.
Prognosis
Early diagnosis is critical; 80% of patients show significant improvement post-shunt if gait is the primary symptom.
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Epidemiology & Etiology
Occurs most frequently in patients >60 years old. While often idiopathic, it can be secondary to conditions that impair CSF resorption, such as meningitis or subarachnoid hemorrhage. It is a rare, reversible cause of dementia.
Pertinent Anatomy
The condition involves the ventricular system of the brain. Enlargement of the lateral ventricles exerts pressure on the corona radiata, which explains the characteristic gait disturbance.
Pathophysiology
Impaired CSF resorption at the arachnoid granulations leads to chronic ventricular dilation. Despite the dilation, CSF pressure remains within the normal range (70–180 mm H2O). This chronic expansion causes mechanical distortion of periventricular white matter tracts.
Clinical Manifestations
The hallmark is the Hakim's triad: gait disturbance (often described as magnetic gait), urinary incontinence, and dementia. Gait disturbance is typically the first and most prominent symptom. Red flags include rapid cognitive decline or focal neurological deficits, which suggest alternative diagnoses.
Diagnosis
The MRI is the initial imaging of choice, demonstrating ventriculomegaly without proportional cortical atrophy. The large-volume lumbar puncture (removal of 30–50 mL of CSF) is the gold standard for predicting shunt responsiveness. A positive response is defined by objective improvement in gait speed or cognitive testing.
Treatment
The definitive treatment is the surgical placement of a ventriculoperitoneal (VP) shunt. Contraindications include patients with severe systemic comorbidities that preclude surgery. If the patient is not a surgical candidate, serial lumbar punctures may be attempted, though they are rarely curative.
Prognosis
Prognosis is highly dependent on the duration of symptoms prior to intervention. 80% of patients experience improvement if gait disturbance is the initial symptom, whereas cognitive outcomes are more variable.
Differential Diagnosis
Alzheimer's disease: memory loss precedes gait disturbance
Parkinson's disease: resting tremor and bradykinesia present
Multi-infarct dementia: history of stroke and focal deficits
Lumbar spinal stenosis: pain with extension, no dementia
Subdural hematoma: history of trauma, focal signs