T1w/T2w Ratio Identifies the Basolateral Amygdala as a Preferential Target in Autoimmune Limbic Encephalitis

Area of Science:

• Neuroscience
• Immunology
• Radiology

Background:

• The amygdala is implicated in the pathophysiology of autoimmune limbic encephalitis (ALE), contributing to seizures and neuropsychiatric symptoms.
• Previous studies have not investigated microstructural changes in individual amygdala nuclei in ALE.
• This study utilizes the T1-weighted/T2-weighted (T1w/T2w) ratio to explore amygdalar pathology in ALE.

Purpose of the Study:

• To investigate microstructural changes in amygdala nuclei in patients with ALE using the T1w/T2w ratio.
• To explore the association between amygdalar pathology and clinical manifestations, including epilepsy and neuropsychiatric symptoms.

Main Methods:

• A single-center study included 57 ALE patients and 16 healthy controls (HC).
• Comprehensive assessments included clinical evaluation, EEG, MRI, and neuropsychological testing.
• T1w/T2w ratio and volumetric measures of the amygdala and its nuclei were analyzed and correlated with epileptic focus and neuropsychiatric outcomes.

Main Results:

• Reduced T1w/T2w ratio in the left amygdala was observed in patients with left temporal and bitemporal epileptic foci compared to HC.
• This reduction was most pronounced in the left basolateral complex.
• No significant correlations were found between MRI measures and neuropsychiatric scores.

Conclusions:

• The basolateral complex of the amygdala shows preferential involvement in ALE, indicating region-specific vulnerability to autoimmune inflammation.
• T1w/T2w ratio alterations in the amygdala correlate with the epileptogenic focus.
• T1w/T2w ratio may serve as a noninvasive biomarker for early diagnosis and treatment monitoring in ALE.