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Difficulty: MediumNeurocognitive Disorders

A 75-year-old man is brought to the neurology clinic by his son. Over the past 8 months, the patient has developed a progressively unsteady gait. The son describes his father's walking as feeling "glued to the ground" with very short steps. For the past 4 months, the patient has had difficulty managing his finances, exhibits new-onset apathy, and struggles with short-term memory. Over the last month, he has had multiple episodes of urinary incontinence, toward which he appears indifferent. His medical history includes hypertension and type 2 diabetes mellitus. Neurological examination reveals a broad-based, magnetic gait, but muscle strength and deep tendon reflexes are normal. A magnetic resonance imaging (MRI) scan of the brain is obtained and is shown below, demonstrating enlarged lateral and third ventricles with relatively normal, uncrowded cortical sulci. What is the most appropriate next step in the management of this patient?

  1. High-volume lumbar punctureAnswer
  2. B
    Placement of a ventriculoperitoneal shunt
  3. C
    Initiation of donepezil therapy
  4. D
    Trial of carbidopa-levodopa
  5. E
    Measurement of cerebrospinal fluid 14-3-3 protein

Answer

High-volume lumbar puncture
The correct answer is a high-volume lumbar puncture. The patient presents with the classic triad of Normal Pressure Hydrocephalus (NPH): abnormal gait (magnetic, broad-based, 'glued to the floor'), cognitive impairment, and urinary incontinence. Neuroimaging confirms communicating hydrocephalus, showing ventriculomegaly without significant cortical atrophy. The most appropriate next step in management is a high-volume lumbar puncture (also known as the tap test or Miller Fisher test) to remove 30-50 mL of cerebrospinal fluid. Improvement in gait and cognitive function following this procedure confirms the diagnosis and indicates that the patient is likely to benefit from definitive surgical treatment with a ventriculoperitoneal shunt.

Step-by-Step Solution

1
Identify the clinical syndrome based on the patient's presentation.
The patient exhibits the classic triad of gait apraxia ('magnetic' gait), cognitive impairment, and urinary incontinence.
Recognizing this specific symptom triad is essential for suspecting Normal Pressure Hydrocephalus (NPH).
2
Analyze the neuroimaging findings provided in the vignette.
The MRI shows ventriculomegaly out of proportion to cortical atrophy.
This confirms communicating hydrocephalus and supports the diagnosis of NPH over ex vacuo ventriculomegaly, which is typically seen in neurodegenerative diseases like Alzheimer's.
3
Determine the next best step in the diagnostic and management pathway.
A high-volume lumbar puncture (Miller Fisher tap test) is indicated.
Removing 30-50 mL of cerebrospinal fluid assesses whether the patient's gait and cognitive symptoms temporarily improve, which strongly predicts the success of definitive surgical treatment.

Key Concept

Diagnosis and management of Normal Pressure Hydrocephalus (NPH)
Estimated Time:1m 0s
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Topics

Neurocognitive Disorders

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