Extra-hippocampal subcortical limbic involvement predicts episodic recall performance in multiple sclerosis

Area of Science:

• Neuroscience
• Radiology
• Cognitive Science

Background:

• Episodic memory impairment is a common yet poorly understood symptom in multiple sclerosis (MS).
• The extended hippocampal-diencephalic system's role in MS memory deficits requires further elucidation.
• Quantitative neuroimaging can help understand these memory impairments.

Purpose of the Study:

• To determine the contribution of the extended hippocampal-diencephalic system to memory performance in MS patients.
• To investigate the relationship between neuroimaging markers and episodic memory deficits in MS.

Main Methods:

• 34 MS patients and 24 controls underwent 3 T MRI, including diffusion tensor imaging and 3-D T1-weighted imaging.
• Fractional anisotropy (FA) of the fornix and volumes of the hippocampus, mammillary bodies, and thalamus were quantified.
• Episodic memory was assessed using visual recall, verbal recall, verbal recognition, and verbal fluency tests.

Main Results:

• MS patients exhibited significantly lower fornix FA and mammillary body volumes compared to controls.
• Forix FA and mammillary body volume predicted visual recall performance in MS patients (R²=.31, P=.003).
• Thalamic volume was a significant predictor of verbal recall (R²=.37, P<.0005), while no limbic measures predicted recognition or fluency.

Conclusions:

• Structural and ultrastructural changes in subcortical limbic regions beyond the hippocampus are associated with episodic recall deficits in MS.
• These findings highlight the importance of the fornix, mammillary bodies, and thalamus in MS-related memory dysfunction.
• Quantitative neuroimaging offers valuable insights into the neural underpinnings of memory impairment in multiple sclerosis.