Longitudinal PET and MRI Evaluation in Late Onset Rasmussen Encephalitis: A Series of Three Cases

Area of Science:

• Neurology
• Nuclear Medicine

Background:

• Rasmussen's encephalitis (RE) is a rare neurological disorder causing epilepsy and brain atrophy.
• Late-onset RE presents diagnostic difficulties due to subtle early symptoms and MRI findings.

Purpose of the Study:

• To evaluate the utility of [18F]FDG PET in diagnosing and monitoring Rasmussen's encephalitis.
• To assess PET's ability to detect metabolic changes preceding or accompanying MRI findings in RE.

Main Methods:

• A case series approach was used to analyze [18F]FDG PET scans in patients with RE.
• PET imaging was employed to detect unihemispheric hypometabolism and crossed cerebellar diaschisis.

Main Results:

• [18F]FDG PET identified unihemispheric hypometabolism and crossed cerebellar diaschisis at diagnosis, prior to apparent MRI changes.
• Follow-up PET scans indicated active disease through hypermetabolism or pseudo-normalization, and quiescence via stable hypometabolism.

Conclusions:

• [18F]FDG PET is valuable for early diagnosis of RE, detecting subclinical seizure activity and disease progression.
• Integrating PET with MRI improves diagnostic accuracy and informs treatment strategies for Rasmussen's encephalitis.