The typical symptoms of Parkinson’s disease such as tremor, rigidity, slowness of movement, and postural instability may also occur in certain other conditions not related to Parkinson’s disease. These symptoms are grouped together under the term “Parkinsonism” and the conditions may be called “secondary Parkinsonism”.

Causes

PD is a relentlessly progressive neurodegenerative disorder of the brain. Lack of dopamine produces the symptoms of Parkinson’s disease.

Parkinsonism may be caused by a number of conditions, such as :

• Dementia with Lewy bodies
• Progressive supranuclear palsy
• Multiple system atrophy
• Corticobasal degeneration
• Shy-Drager syndrome
• Wilson’s disease
• Benign essential tremor
• Dystonic tremor
• Huntington’s disease.
• Creutzfeldt-Jakob disease (CJD or “Mad Cow Disease”)
• Pick’s disease
• Alzheimer’s disease
• Encephalitis
• Meningitis
• Brain tumors
• Stroke
• Head injury, particularly repeated head trauma, as in boxing
• Drugs- pharmaceutical and narcotic
• Other toxins – manganese, carbon monoxide, methanol

Drug-Induced Parkinsonism

The onset of drug induced Parkinsonism is more rapid than that of PD. On withdrawal of the offending drug the symptoms often improve but some percentage of patients develop persistent and progressive Parkinsonism. In these cases it is believed that the drug did not cause the Parkinsonism but rather unmasked a latent condition.

Many medicines have been implicated in producing parkinsonism, including :

• Antiemetics – metoclopramide
• Antidepressants – selective serotonin-reuptake inhibitors (SSRI)
• Antipsychotics (used to treat severe paranoia and schizophrenia) – chlorpromazine, haloperidol. Atypical antipsychotics are less likely to cause secondary Parkinsonism
• Anti-seizure medication – valproic acid.
• Antihypertensives – methyldopa, reserpine
• Brain damage caused by anesthetic drugs

MPTP seems to be selectively toxic to the cells in the substantia nigra, producing not only sudden irreversible Parkinsonism but all other associated features of PD too. Inadvertent synthesis and use of MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) while trying to manufacture MPPP (1-methyl-4-phenyl-4-propionpiperidine), an illicit narcotic compound, led to symptoms of PD.

Use of MPPP contaminated with MPTP, which was sold in the street as synthetic heroin, led to similar symptoms with toxicity and death.

Symptoms

PD and Parkinsonism may have similar symptoms. Tremor, rigidity, slowness of movements, postural instability, slow shuffling gait, unilateral involvement (symptoms only on one side of the body) or other associated symptoms of PD such as dementia, difficulty with speech, swallowing difficulties and other features may also be present with secondary Parkinsonism.

Diagnosis

Differentiation between Parkinsonism due to some other cause and that due to PD may become difficult in patients presenting with early symptoms, especially in the elderly.

• A thorough history, noting other signs and symptoms, and a neurological examination may help to arrive at a diagnosis.
• There are no definite tests to confirm the diagnosis of PD, which is often diagnosed by eliminating other causes of Parkinsonism.
• Investigations, including a CT scan and MRI, may be done as indicated.
• A dramatic improvement of symptoms with levodopa can sometimes support the diagnosis of Parkinson’s disease.

Treatment

Treatment of PD is usually with a combination of anti-Parkinson drugs, including levodopa, and auxilliary therapies like physical therapy.

In Parkinsonism, treatment will be directed the cause, once it is identified. Parkinsonism caused by drugs or toxins often improve on stopping the drugs or eliminating the toxins. Specific treatment may be undertaken for other diagnosed conditions.

In most cases, Parkinsonism due to other causes does not respond, or responds only moderately, to anti-Parkinson drugs.