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PARKINSON'S DISEASE & PARKINSON'S DISEASE DEMENTIA

Parkinson's disease is a progressive neurodegenerative disorder that is common, age-related and chronic.

It is caused by loss or degeneration of dopaminergic neurons in the substantia nigra of the midbrain.

Onset of symptoms and progression of the disease is gradual.

Motor signs and symptoms include resting tremor, rigidity, bradykinesia and postural instability.

Parkinson's disease dementia indicates loss of intellectual functions including memory, significant deterioration in the ability to carry out day-to-day activities and changes in social behavior are often noted.

Diagnosis

It may be difficult to diagnose Parkinson's disease during the early stages of the disease

  • Diagnosis is clinical and requires the presence of the cardinal manifestations of Parkinson's disease, absence of atypical features, a slowly progressive course, and a response to drug therapy
    • Pronounced loss of olfactory sense can distinguish Parkinson's disease from other forms of parkinsonism
Movement Disorder Society - Unified Parkinson's Disease Rating Scale (MDS-UPDRS)
  • Used as a gold standard for the clinical diagnosis of Parkinson’s disease
  • Contains 3 sections [mentation, behavior and mood; activities of daily living (ADL); and motor] that rates the course of Parkinson’s disease
  • Essential characteristic of Parkinson’s disease is the presence of motor parkinsonism (bradykinesia with tremor or rigidity)
  • Clinically established Parkinson's disease can be made if all of the following requirements are met:
    • Positive parkinsonism
    • No absolute exclusion criteria (see Alternative Diagnosis discussion)
    • At least 2 supportive criteria
    • No red flags (see Alternative Diagnosis discussion)

Imaging

Neuroimaging Tests
Functional Neuroimaging

  • Positron emission tomography (PET) scan
  • Functional MRI
Structural Neuroimaging
  • MRI
  • CT scan
Dopamine Transporter Single Photon Emission Computed Tomography (DaTscan-SPECT)
  • Used when there is significant diagnostic uncertainty after serial clinical evaluations, in patients with suspected drug-induced parkinsonism, patients who are possible candidates for deep brain stimulation and to rule out parkinsonian syndrome

Complications

Psychiatric Complications

Mood Disorder

  • Mood disorders, particularly depression, are common in Parkinson's disease
  • Impulse control disease (ICD) or dopamine dysregulation syndrome (DDS) are usually found in dopamine agonist treatment
  • Accurate recognition and diagnosis is important; however, there may be overlap of cognitive and somatic symptoms of Parkinson's disease and those with depression resulting to inaccurate diagnosis
  • Various screening tools may be used in assessing depression in Parkinson's disease (eg Hamilton depression rating scale, Montgomery-Asberg depression rating scale), although diagnosis should not be based solely on rating scale

Sleep Disorder

  • Parkinson’s Disease Sleep Scale (PDSS) is a 15-item visual analogue scale that is used to assess sleep disturbance in patients with Parkinson's disease

Parkinson's Disease Dimentia (PDD)

  • Dementia indicates loss of intellectual functions including memory, significant deterioration in the ability to carry out day-to-day activities and changes in social behavior are often noted
  • An 8-year prospective study of patients with Parkinson's disease revealed that approximately 75% of the representative Parkinson's disease cohort developed dementia during the study period
  • Risk factors include older age, age at onset of Parkinson's disease is ≥60 years old, long duration of disease, absence of a resting tremor (akinetic-rigid subtype), and presence of hallucinations or depression
  • Pathology includes neurotransmitter deficiencies in dopamine (substantia nigra and ventral tegmental area), acetylcholine (nucleus basalis of Meynert), norepinephrine (locus ceruleus), and serotonin (raphe nuclei), as well as Lewy bodies in cortical and subcortical regions
  • Parkinson's disease patients showing mild cognitive impairment should be assessed
  • Parkinson's disease dementia may present with bradyphrenia and memory retrieval deficits; impaired set shifting and maintenance; impaired problem solving; poor visuospatial function; decreased fluency and other language abnormalities; and mood disorders are often noted
  • Patients with Parkinson's disease presenting with dementia and depression have more severe disabilities and develop faster decline in cognitive function
  • Faster rate of cognitive impairment and poor prognosis are commonly noted in Parkinson's disease patients with older age, hallucinations, and non-tremor motor subtype
  • Atypical neurological features of Parkinson's disease (eg early occurrence of autonomic failure, symmetrical disease presentation, non-tremor presentation, poor response to dopamine agonists) are indicative of other neurodegenerative diseases associated with more severe dementia

Screening

  • There are no validated diagnostic criteria for Parkinson's disease dementia but in practice, the McKeith’s criteria is applied
  • Clinical distinction between Parkinson's disease dementia and dementia with Lewy bodies (DLB) lies in the timing of the onset of cognitive impairment in relation to motor symptoms
    • Parkinson's disease dementia >1 year
    • Dementia with Lewy bodies ≤1 year

Screening Tools for Dementia

  • Montreal Cognitive Assessment (MoCA) - has been found to be a more accurate bedside test for Parkinson's disease dementia
  • Mini-Mental State Examination (MMSE)
  • Cambridge Cognitive Examination (CAMCog)
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