Diagnosis of Parkinson's Disease

Differential Diagnosis of Parkinson's Disease

Several other conditions can mimic the neurologic symptoms of Parkinson's disease and must be excluded before the diagnosis is established. It is important to differentiate between true idiopathic (unknown cause) Parkinson's disease and parkinsonian symptoms that develop secondary to some underlying condition or medication.

The two most common categories of conditions that may be mistaken for Parkinson's disease include medication-induced parkinsonism and Parkinson-plus syndrome.

• Medication-Induced Parkinsonism - Certain medications may either cause parkinsonian symptoms or exacerbate the severity of symptoms in the individual diagnosed with Parkinson's disease. It is important to determine whether symptoms are related to medications in which case discontinuing the medications can result in cessation of symptoms over time or to actual Parkinson's disease. The most common medications that can induce parkinsonian symptoms include:

  • antipsychotics - Examples include haloperidol, thioridazine, risperidone, lithium, chlorpromazine, olanzapine. Parkinsonian side-effects of these medications can last 1-2 years after stopping the medications.
  • antiemetics - These drugs are used to treat nausea and vomiting. Examples include prochlorperazine and metoclopramide.
  • antihypertensives - These drugs are used to treat high blood pressure. Examples include methyldopa and reserpine
  • antianginals - Heart medications used to treat angina or chest pain (e.g., diltiazem).
  • antineoplastics - These drugs are used to treat various types of cancers.

• Parkinson-Plus syndromes - This is a group of disorders which presents with Parkinsonism in association with other distinct clinical features, such as autonomic disturbances (Shy-Drager syndrome) or ataxia (multi-system atrophy). These syndromes show poor or short-lived therapeutic response to Parkinson's disease medications and include symptoms or patterns of symptoms that do not appear in Parkinson's disease such as:

  • signs of dementia early after onset of symptoms
  • incidences of falling soon after onset of symptoms
  • feet set wide apart while walking
  • abnormal eye movements
  • symmetric (bilateral) signs of parkinsonism
  • severe disability within five years of onset of symptoms

Other conditions which should be ruled out when a patient present with Parkinson-like symptoms include:

• Multi-infarct disease (multiple small strokes), also called arteriosclerotic (vascular) parkinsonism
• Other degenerative brain diseases such as Alzheimer's Disease (destroys memory and cognition) and Huntington's Disease (causes uncontrolled movements and cognitive loss), among others
• Dementia with Lewy bodies
• Normal Pressure Hydrocephalus which is an excessive accumulation of cerebrospinal fluid in the cerebral ventricles of the brain
• Brain tumors
• Exposure to toxins such as manganese dust, carbon disulfide and carbon monoxide
• Abuse of drugs containing MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine), often found in heroin, was found to cause a permanent form of Parkinson's. This finding in the 1980's actually heralded an important breakthrough in Parkinson's disease research as scientists could now induce a simulated Parkinson's disease in animals for further study.
• Shuffling gait disorders which can be caused by many other conditions and are often misdiagnosed as Parkinson's disease.
• Wilson's disease - causes the body to retain copper

• Essential tremor - tremors not related to Parkinson's disease but often confused with early Parkinson's disease. They are distinguished from Parkinson's disease by the following signs:

  • typically bilateral
  • often accompanied by head tremor or tremulous voice
  • handwriting is typically large and tremulous
  • signs of bradykinesia and rigidity are absent