FDG- and Dopa-PET in postencephalitic parkinsonism

Area of Science:

• Neurology
• Virology
• Medical Imaging

Background:

• Postencephalitic Parkinsonism (PEP) is a rare neurological disorder that can follow viral encephalitis.
• Encephalitis lethargica, described by von Economo in 1917, shares clinical features with some forms of PEP.
• Idiopathic Parkinson syndrome (IPS) is a common neurodegenerative disorder with distinct pathological and metabolic characteristics.

Observation:

• A 74-year-old woman developed akinetic-rigid Parkinsonism with tremor, hypokinesia, hypomimia, rigidity, cogwheel phenomenon, brady-dysdiadochokinesia, and myoclonic jerks after acute viral encephalitis.
• Cerebrospinal fluid analysis indicated viral encephalitis.
• Serological screening revealed a positive Influenza A IgA-antibody titer (1:>160).

Findings:

• Positron Emission Tomography (PET) revealed altered glucose and dopa metabolism patterns in the patient, differing significantly from those observed in idiopathic Parkinson syndrome (IPS).
• The observed metabolic differences are attributed to the acute loss of inhibitory input from the substantia nigra pars compacta to the striatum.
• The findings suggest Influenza A as a potential cause of postencephalitic Parkinsonism (PEP).

Implications:

• This case highlights Influenza A as a possible etiological agent for postencephalitic Parkinsonism (PEP).
• Positron Emission Tomography (PET) imaging can effectively differentiate PEP caused by viral infections from idiopathic Parkinson syndrome (IPS).
• Understanding the distinct metabolic profiles of different Parkinsonian syndromes can aid in diagnosis and potentially inform future therapeutic strategies.