Can Normal Pressure Hydrocephalus (NPH) lead to memory lapses?

Normal Pressure Hydrocephalus and Memory Lapses

Yes, Normal Pressure Hydrocephalus (NPH) commonly causes memory lapses as part of its characteristic cognitive impairment profile. Memory dysfunction is a key component of the classic NPH triad, which also includes gait disturbance and urinary incontinence 1.

Cognitive Profile in NPH

• NPH typically presents with cognitive impairments characterized by frontal lobe symptoms, including psychomotor slowing and deficits in attention, working memory, verbal fluency, and executive function 2
• Memory lapses in NPH patients typically manifest as:
  • Diminished immediate memory performance due to slowed or inefficient cognitive processing 2
  • Relatively preserved recognition memory compared to recall ability 2
  • Less severe memory and orientation impairment compared to Alzheimer's disease patients 2

Clinical Presentation and Progression

• Patients with NPH typically present late in the disease course due to the slow and gradual nature of symptom onset 1
• The classic symptom progression follows a pattern:
  • Gait disturbances typically occur early in the disease course 1
  • Cognitive impairment including memory lapses develops later 1
  • Urinary incontinence often appears as the third symptom 1

Neuroanatomical Basis of Memory Impairment in NPH

• Memory lapses and other cognitive deficits in NPH are likely associated with damage to periventricular structures, including 2:
  • Corpus callosum
  • Frontal subcortical and cortical areas
  • Thalamus
  • Basal ganglia
  • Hippocampus

Diagnostic Considerations

• MRI without IV contrast is the preferred imaging modality for diagnosing NPH 1, 3

• Key MRI findings include:

  • Ventriculomegaly (Evan's index >0.3) 3
  • Narrowed posterior callosal angle (<90°) 3
  • Effaced sulci along high convexities 1, 3
  • Widened sylvian fissures 1, 3
  • Periventricular white matter changes 1, 3
  • Cerebral aqueduct flow void (associated with good response to shunt surgery) 3

• CT without IV contrast can be used as an alternative when MRI is contraindicated, but has lower sensitivity for detecting periventricular white matter changes and cannot visualize cerebral aqueduct flow void 1, 3

Treatment and Prognosis for Memory Symptoms

• NPH is one of the potentially reversible causes of dementia when treated with CSF diversion (shunting) 1
• After shunt operation 2, 4:
  • Cognitive impairment, including memory lapses, can improve but marked improvement is less frequent than for gait disorders
  • Impairment of memory, working memory, and visuoconstructive abilities appears likely to respond to shunt surgery
  • Patients with both memory impairment and visuoconstructive or executive dysfunction may show less improvement, suggesting more irreversible neural damage or comorbid conditions

Important Clinical Considerations

• NPH can be comorbid with other neurodegenerative diseases, such as Alzheimer's disease, which is detected in 20% to 57% of patients with NPH 1
• Long-term follow-up studies show that despite initial response to shunting, many NPH patients develop progressive cognitive decline, with 80% showing cognitive deterioration and 46% developing clinical dementia over a median follow-up of 4.8 years 4
• Memory deficits as the first symptom before shunt placement significantly predict later development of dementia (OR 18.3) 4
• NPH should always be considered in the differential diagnosis when memory lapses occur alongside gait disturbance and/or urinary incontinence, as approximately 80% of cases remain unrecognized and untreated 5

Atypical Presentations

• In some cases, NPH may present with psychiatric manifestations including paranoid psychosis and mild cognitive impairment before the classic triad fully develops 6
• While typically considered a disorder of older adults, NPH can occasionally affect children and young adults, though their presentation may differ from the classic adult triad 7