Diverse Gait Phenotypes in Normal Pressure Hydrocephalus Beyond Lower Body Parkinsonism

Overview

Normal pressure hydrocephalus (NPH) presents with a spectrum of gait disturbances beyond the classic lower body parkinsonism. Shunt surgery improves gait, cognitive function, urinary incontinence, postural stability, and upper limb motor function, though responses vary by symptom domain and gait phenotype.

Background

NPH is characterized by the Hakim-Trias: gait disturbance, cognitive impairment, and urinary incontinence. The typical gait disorder is a slow, wide-based, magnetic gait resembling lower body parkinsonism, but recent evidence reveals diverse gait phenotypes. Shunting cerebrospinal fluid is the gold standard treatment, with gait improvement rates up to 85%. Cognitive deficits in NPH include subcortical-frontal dementia affecting attention, memory, and executive functions, while urinary incontinence is common and linked to detrusor overactivity. Postural instability and upper limb motor dysfunction also contribute to the clinical picture and may improve after shunting.

Data Highlights

Improvement rates of gait disturbance after shunt surgery can reach up to 85%. Urinary incontinence occurs in up to 91% of NPH patients, with a female predominance. Shunting significantly improves urinary urgency and urge incontinence, enhancing physical activity and quality of life. Cognitive domains such as verbal learning, memory, global cognition, and psychomotor speed show significant post-shunt improvement, while executive function improvement remains less certain. Postural instability and upper limb motor function also respond positively to shunting.

Key Findings

• Gait disturbance in NPH is heterogeneous, ranging from unspecific to Parkinson-like phenotypes.
• Shunt surgery yields the best symptomatic improvement in gait but responses vary by gait pattern.
• Cognitive impairment in NPH affects multiple domains, with verbal learning and memory showing significant improvement post-shunting.
• Urinary incontinence, present in up to 91% of patients, improves significantly after shunt surgery, particularly urgency and urge incontinence.
• Postural instability may originate from central vestibular, proprioceptive, or postural center dysfunction and improves after shunting.
• Upper limb motor function is impaired in NPH and can be assessed with tests like the Finger Tapping Test, which may predict shunt responsiveness.

Clinical Implications

Clinicians should recognize the diverse gait phenotypes in NPH beyond classic lower body parkinsonism to tailor assessment and management. Shunt surgery remains the cornerstone treatment, with expected improvements in gait, cognition, urinary symptoms, postural stability, and upper limb motor function. Incorporating upper limb motor tests may aid in evaluating shunt responsiveness and guide therapeutic decisions.

Conclusion

NPH manifests with a complex motor and cognitive profile extending beyond traditional descriptions, and shunt surgery offers multifaceted symptomatic relief. Future research into diverse gait phenotypes and upper limb function assessments may enhance patient selection and outcome prediction.

References

1. Hakim-Trias -- Classic NPH symptom triad
2. Recent studies on gait phenotypes in NPH
3. Shunt surgery efficacy in NPH
4. Cognitive impairment domains in NPH
5. Urinary incontinence characteristics and treatment response
6. Postural instability origins and improvement
7. Upper limb motor function testing in NPH