postencephalitic parkinsonism

Postencephalitic parkinsonism is a neurological disorder that occurs after encephalitis, or inflammation of the brain. This condition is a form of secondary parkinsonism, meaning it arises from a known cause, unlike Parkinson disease, which has no identifiable cause.123

The pathology involves the degeneration of neurons in the substantia nigra, a part of the brain responsible for controlling voluntary movement. These neurons normally produce dopamine, a neurotransmitter crucial for regulating movement. When these dopamine-producing cells are damaged or destroyed, dopamine levels drop, disrupting the brain's motor control system. This leads to symptoms characteristic of parkinsonism, such as tremors, muscle rigidity, and difficulty initiating movement.34

A notable historical cause of postencephalitic parkinsonism was the encephalitis lethargica pandemic that occurred after World War I.32