Axonal pathology in multiple sclerosis: relationship to neurologic disability.

Area of Science:

• Neuroscience
• Neurology
• Pathology

Background:

• Multiple sclerosis (MS) is characterized by inflammatory demyelination leading to axonal damage.
• Axonal loss is increasingly recognized as a primary driver of irreversible neurologic disability in MS patients.
• Both active inflammation and chronic demyelination contribute to axonal degeneration throughout the disease course.

Purpose of the Study:

• To review evidence supporting axonal loss as the key factor in MS-related irreversible neurologic disability.
• To discuss the implications of axonal loss for disease monitoring and therapeutic strategies in MS.
• To propose potential surrogate markers and treatment approaches for managing MS progression.

Main Methods:

• Review of pathological studies implicating demyelination in axonal transection and degeneration.
• Analysis of magnetic resonance spectroscopy (MRS) and imaging (MRI) data on early axonal loss and brain atrophy.
• Synthesis of findings to correlate axonal loss with disability progression and disease staging.

Main Results:

• Axonal loss begins at the onset of MS and contributes to progressive disability.
• Brain atrophy occurs early in MS, with compensatory mechanisms masking functional decline initially.
• Beyond a certain threshold of axonal loss, disability progression becomes continuous, potentially marking the transition to secondary progressive MS.

Conclusions:

• Axonal loss is a critical determinant of irreversible neurologic disability in multiple sclerosis.
• Early therapeutic intervention, including disease-modifying and neuroprotective agents, is essential before significant axonal loss occurs.
• Brain parenchymal fraction is proposed as a surrogate marker for monitoring axonal loss and disease progression in MS clinical trials and patient care.