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[A case of encephalitis with MRI abnormalities localized in the bilateral amygdala and hippocampus]
I Kohira1, T Shohmori, S Kuroda
1Department of Neurology, Okayama University Medical School, Japan.
Abstract:
We report a patient with encephalitis who showed anterograde and retrograde amnesia with MRI abnormalities localized in the bilateral amygdala (AM) and hippocampus (HIPP). A 25-year-old man suddenly experienced a generalized tonic-clonic seizure (GTCS). He was admitted because of increasing lethargy with two further GTCSs during the following 6 days. The patient had high fever, and neurological examination revealed somnolence, disorientation, amnesia, and nuchal stiffness. MRI revealed bilateral symmetrical abnormalities localized in the AM and HIPP, which showed low intensity on T1-weighted images and high intensity on T2-weighted images. Cerebrospinal fluid examination showed a mildly elevated cell count. We suspected herpes simplex virus type I encephalitis and began treatment with acyclovir. After the patient regained a clear consciousness, his antero- and retrograde amnesia continued for several months. The MRI abnormality became less distinct with the improvement of amnesia. We consider that the MRI abnormality was indicative of inflammation and edema, and that the lesion in the AM and HIPP had induced the amnesia.
Insights
A patient with encephalitis experienced severe amnesia due to inflammation and edema in the amygdala and hippocampus. MRI confirmed these abnormalities, highlighting the link between brain lesions and memory loss.
Area of Science:
- Neurology
- Neuroimaging
- Infectious Diseases
Background:
- Encephalitis can present with diverse neurological symptoms, including memory impairment.
- Herpes simplex virus type 1 (HSV-1) is a common cause of infectious encephalitis.
Observation:
- A 25-year-old male presented with seizures, fever, lethargy, and disorientation, indicative of encephalitis.
- Magnetic Resonance Imaging (MRI) revealed bilateral symmetrical abnormalities in the amygdala (AM) and hippocampus (HIPP).
- The patient exhibited profound anterograde and retrograde amnesia lasting several months post-treatment.
Findings:
- MRI showed T1-hypointensity and T2-hyperintensity in the bilateral AM and HIPP, suggesting inflammation and edema.
- Cerebrospinal fluid analysis revealed a mildly elevated cell count.
- Acyclovir treatment was initiated for suspected HSV-1 encephalitis.
Implications:
- Lesions in the amygdala and hippocampus are strongly associated with severe amnesia.
- MRI findings in encephalitis can correlate with clinical symptoms and disease progression.
- This case underscores the critical role of the AM and HIPP in memory formation and retrieval.