G21.3

Approximate Synonyms

• Parkinsonism, postencephalitic

Clinical Information

• Parkinsonism following encephalitis, historically seen as a sequella of encephalitis lethargica von economo encephalitis). The early age of onset, the rapid progression of symptoms followed by stabilization, and the presence of a variety of other neurological disorders e.g., sociopathic behavior; tics; muscle spasms; oculogyric crises; hyperphagia; and bizarre movements) distinguish this condition from primary parkinson disease. Pathologic features include neuronal loss and gliosis concentrated in the mesencephalon; subthalamus; and hypothalamus. from Adams et al., Principles of Neurology, 6th ed, p754)

Details

• G21.3 is a billable/specific ICD-10-CM code that can be used to indicate a diagnosis for reimbursement purposes.

• The 2023 edition of ICD-10-CM G21.3 became effective on October 1, 2022.

• This is the American ICD-10-CM version of G21.3 – other international versions of ICD-10 G21.3 may differ.