Makindo Medical Notes

Note: The popularity of the diagnosis of Normal Pressure Hydrocephalus (NPH) seems to be waning. The challenge lies in differentiating patients with NPH who will benefit from shunting, given the prevalence of the clinical triad and ventricular enlargement due to cerebral atrophy. Shunting carries significant risks, making patient selection critical.

About

• Normal Pressure Hydrocephalus (NPH): A condition characterized by the buildup of cerebrospinal fluid (CSF) in the brain's ventricles without a significant increase in CSF pressure, leading to symptoms of gait disturbance, cognitive decline, and urinary incontinence.
• It may result from reduced CSF absorption at the arachnoid villi, leading to a gradual buildup of fluid.
• Primarily affects older adults, typically over the age of 60, and was first described by Salomon Hakim in 1965.
• Considered a potentially reversible cause of dementia, but identifying candidates for shunting is challenging due to overlap with other neurodegenerative conditions.

Causes

• Idiopathic: Most cases have no identifiable cause, making diagnosis more challenging.
• Secondary Causes: Often result from trauma or conditions affecting CSF pathways:
  • Head injury or traumatic brain injury (TBI)
  • History of meningitis or other CNS infections
  • Subarachnoid hemorrhage (SAH)
  • Brain tumors that obstruct CSF pathways

Aetiology

• The condition involves damage or compression of white matter tracts that transmit signals controlling motor functions and bladder control.
• Brainstem or cortical compression can also disrupt normal neurological pathways, leading to the characteristic triad of symptoms.
• The exact mechanisms remain poorly understood, and the relationship between CSF dynamics and symptom development is a focus of ongoing research.

Clinical Features

• Triad of Symptoms: The classic Hakim triad includes:
  • Gait Disturbance: Often described as a "magnetic gait" or "feet glued to the floor." Patients may shuffle or have difficulty initiating walking, resembling Parkinsonian gait.
  • Urinary Incontinence: Urgency, frequency, and in more advanced cases, frank incontinence. This symptom can significantly impact quality of life.
  • Cognitive Impairment: Often presents as apathy, difficulty with planning, or a slowing of thought processes. Memory may be less affected initially compared to other types of dementia.
• Progression: Symptoms typically worsen gradually over months to years, contributing to increasing disability and reduced independence.
• Absence of Headache: Unlike other types of hydrocephalus, NPH usually does not present with headache due to the absence of increased intracranial pressure (ICP).

Differential Diagnosis

• Consider other conditions that may present with similar symptoms:
  • Alzheimer's disease or vascular dementia
  • Parkinson's disease or Parkinson-plus syndromes
  • Multisystem atrophy (MSA)
  • Spinal stenosis (may mimic gait disturbances)
  • Chronic subdural hematoma

Investigations

• Initial Steps: Rule out other causes of dementia and gait abnormalities through a comprehensive history and physical examination.
• Lumbar Puncture (LP): Shows normal CSF opening pressure, but large-volume removal (up to 40 mL) may provide temporary symptom relief, which helps identify potential shunt responders.
• CT Scan: Shows enlarged ventricles (ventriculomegaly) without significant cortical atrophy. Ventricular dilation is more prominent than would be expected for the degree of brain atrophy, but other conditions may also cause ex-vacuo dilation (ventricular enlargement due to brain tissue loss).
• MRI: Better for evaluating structural changes; may show periventricular hyperintensity due to transependymal flow of CSF, suggestive of chronic CSF accumulation.
• Gait Assessment: Should be performed before and after LP to assess improvement, which can indicate a positive response to shunting.

CT scan of NPH

Management

• Multidisciplinary Approach: Involves neurologists, neurosurgeons, and geriatric specialists for comprehensive assessment and management.
• Pre-Shunt Assessment: Includes gait testing and cognitive evaluation before and after large-volume LP. Improvement suggests potential benefit from shunting.
• Ventriculoperitoneal (VP) Shunt: The most common surgical procedure, diverting excess CSF from the brain's ventricles to the peritoneal cavity. The goal is to relieve symptoms by reducing ventricular pressure.
  • Outcome: 20-90% of patients experience some improvement post-shunting, but results are variable.
  • Complications: Include bleeding, shunt infection, overdrainage leading to subdural hematoma (SDH), and low-pressure headaches.
  • Shunt Adjustments: Programmable shunts allow adjustments in drainage pressure to optimize outcomes and minimize side effects.
• Conservative Management: Reserved for patients who are poor surgical candidates due to comorbidities or advanced age. Focuses on symptom management and fall prevention.
• Rehabilitation: Physical therapy for gait training and occupational therapy can aid in improving mobility and daily function, even in those with limited response to surgery.
• Long-term Follow-up: Regular follow-up is essential to monitor for complications, assess shunt function, and evaluate symptom progression or improvement.

Prognosis

• Variable Outcome: While some patients experience significant improvement in gait and cognition, others may show minimal benefit, particularly if shunting is performed late in the disease course.
• Early Intervention: Patients who respond well to LP and undergo early shunting tend to have better outcomes.
• Risk of Progression: Untreated NPH can lead to progressive disability, increased risk of falls, and further cognitive decline.

References

• Normal Pressure Hydrocephalus: Diagnosis and Management
• Mayo Clinic: Normal Pressure Hydrocephalus
• BMJ Journal: Management of Normal Pressure Hydrocephalus