Cognitive Decline and Dementia

Key Facts

  • The vast majority of PD patients may experience some form of cognitive impairment, even before motor symptoms develop.
  • A wide variety of cognitive functions are affected in PD, but the most common one is deficit in executive function.
  • Identification is of major importance as appropriate management can improve quality of life for patient and caregiver.
  • Changes in medication used to treat Parkinson's symptoms may be needed for better management.
  • All individuals with cognitive impairment should undergo a driving evaluation.

Clinical Best Practices

  • You should rule out treatable causes of cognitive decline/dementia including hypothyroidism, Addison’s disease, infections, and medications.

The vast majority of PD patients may experience some form of cognitive impairment over time with perhaps 75% or more developing PD dementia in advanced disease. Cognitive deficits tend to be worse for patients with predominant symptoms of bradykinesia and rigidity. Being male and having visual hallucinations are strong predictors of developing dementia in PD.

Cognitive Functions Affected

The following cognitive functions are usually affected in PD:

  • Attention
  • Speed of mental processing
  • Problem solving or executive function
  • Memory
  • Language
  • Visuospatial

Common Treatable Causes

  • Infection (asymptmatic aspiration pneumonia and UTI are the commonest infections), metabolic disorders (check B12, TSH, RPR in every patient)—particularly if onset is acute
  • Medication introduction—sedatives or analgesia
  • Antiparkinsonian medication

Diagnosis

 

Barriers to Diagnosis

  • Patient and family denial

Treatment Options

 Minimize

Stop

Important Caveats to Therapy

  • Cholinesterase inhibitors may worsen parkinsonism-in particular, tremor-or cause agitation

Note: all individuals with cognitive impairment should undergo a driving evaluation to assess driving skills and safety.

References: 

 

Miyasaki JM, Shannon K, Voon V, et al; Quality Standards Subcommittee of the American Academy of Neurology. Practice parameter: evaluation and treatment of depression, psychosis, and dementia in Parkinson disease (an evidence-based review): report of the Quality Standards Subcommittee of the American Academy of Neurology. Neurology. 2006;66(7):996-1002.

Goldman Gross R, Siderowf A, Hurtig HI. Cognitive impairment in Parkinson’s disease and dementia with Lewy bodies: a spectrum of disease. Neurosignals. 2008;16(1):24-34.