Illustration of brain hemispheres with varying levels of neural activity, symbolizing brain excitability asymmetry in multiple sclerosis.

Brain Balance: How Understanding Excitability Asymmetry Could Revolutionize Multiple Sclerosis Treatment

Jordan Keane in Health & Wellness December 2025 • 4 min read.

"New research reveals the potential of brain excitability as a key biomarker in multiple sclerosis, offering hope for more targeted and effective therapies."

Multiple sclerosis (MS) is a complex neurological condition affecting millions worldwide. It is characterized by the immune system attacking the protective myelin sheath around nerve fibers, leading to a range of physical and cognitive symptoms. Managing MS effectively requires a deep understanding of its underlying mechanisms, and recent research is shedding light on a promising new area: brain excitability.

Traditionally, MS research has focused on structural changes in the brain, such as lesions detected through MRI. While valuable, these structural insights don't fully explain the variability in symptoms and disease progression among individuals. Scientists are now exploring the functional aspects of the brain, particularly how nerve cells (neurons) communicate and respond to stimuli. This has led to the concept of brain excitability – the ease with which neurons fire – and how imbalances in this excitability might contribute to MS.

A groundbreaking study by Chaves et al. delves into the idea of brain excitability asymmetry in MS patients. This asymmetry refers to the differences in excitability between the left and right hemispheres of the brain. The study reveals that this asymmetry is not just a random occurrence but could be a critical biomarker, offering new avenues for diagnosis, treatment monitoring, and personalized therapeutic strategies in MS.

What is Brain Excitability Asymmetry and Why Does It Matter in MS?

Illustration of brain hemispheres with varying levels of neural activity, symbolizing brain excitability asymmetry in multiple sclerosis.

Brain excitability refers to the readiness of neurons to fire in response to stimulation. This process is crucial for all brain functions, from motor control to cognitive processing. In a healthy brain, there is a balance between excitatory and inhibitory signals, ensuring that neural activity is regulated and efficient. However, in neurological conditions like MS, this balance can be disrupted, leading to areas of hyperexcitability (overactive neurons) or hypoexcitability (underactive neurons).

Brain excitability asymmetry specifically looks at the differences in neuronal firing patterns between the two hemispheres. While some degree of asymmetry is normal, significant imbalances can indicate underlying neurological issues. In the context of MS, researchers are discovering that this asymmetry is linked to various disease characteristics and symptoms.

Objective and Subjective Symptoms: The study found that the severity of MS-related physical symptoms, such as walking speed and dexterity, as well as cognitive functions, correlates with the degree of brain excitability asymmetry.
Neuroinflammation: Atypical brain excitability asymmetry in MS may indicate neuroinflammation-mediated hyperexcitability.
Biomarker Potential: Shifting excitability asymmetry significantly predicted more severe physical MS symptoms and cognitive processing.
Tracking Disease Progression: Monitoring brain excitability asymmetry could provide a way to track the progression of MS and assess the effectiveness of treatments.

To investigate brain excitability, the research team used transcranial magnetic stimulation (TMS). This non-invasive technique involves using magnetic pulses to stimulate specific areas of the brain and measure the resulting neuronal activity. By applying TMS to both hemispheres of MS patients, the researchers were able to quantify the excitability of each side and calculate an asymmetry ratio.

The Future of MS Treatment: Personalized Approaches Based on Brain Excitability

The findings of this study open new doors for personalized MS treatment. By understanding an individual’s unique pattern of brain excitability asymmetry, clinicians can potentially tailor therapeutic interventions to address the specific imbalances present. This could involve using targeted therapies to reduce hyperexcitability in one hemisphere or enhance activity in another, ultimately leading to improved symptom management and a better quality of life for those living with MS.

About this Article -

This article was crafted using a human-AI hybrid and collaborative approach. AI assisted our team with initial drafting, research insights, identifying key questions, and image generation. Our human editors guided topic selection, defined the angle, structured the content, ensured factual accuracy and relevance, refined the tone, and conducted thorough editing to deliver helpful, high-quality information.See our About page for more information.

This article is based on research published under:

DOI-LINK: 10.1016/j.bbr.2018.11.005, Alternate LINK

Title: Asymmetry Of Brain Excitability: A New Biomarker That Predicts Objective And Subjective Symptoms In Multiple Sclerosis

Subject: Behavioral Neuroscience

Journal: Behavioural Brain Research

Publisher: Elsevier BV

Authors: Arthur R. Chaves, Elizabeth M. Wallack, Liam P. Kelly, Ryan W. Pretty, Hailey D. Wiseman, Alice Chen, Craig S. Moore, Mark Stefanelli, Michelle Ploughman

Published: 2019-02-01

Everything You Need To Know

What is brain excitability asymmetry, and why is it important in the context of Multiple Sclerosis (MS)?

Brain excitability asymmetry refers to the differences in the ease with which nerve cells, also known as neurons, fire between the left and right hemispheres of the brain. In the context of Multiple Sclerosis (MS), it matters because significant imbalances in brain excitability asymmetry can indicate underlying neurological issues and are linked to various disease characteristics and symptoms, such as walking speed, dexterity, and cognitive functions. Researchers found a correlation between the severity of MS-related physical symptoms and cognitive functions with the degree of brain excitability asymmetry. This understanding is crucial as it opens up new avenues for diagnosis, treatment monitoring, and personalized therapeutic strategies in MS.

What is brain excitability, and why is it important?

Brain excitability is the ease with which neurons fire in response to stimulation. It's a crucial process for all brain functions, from motor control to cognitive processing. In a healthy brain, there's a balance between excitatory and inhibitory signals, ensuring efficient neural activity. However, in neurological conditions like MS, this balance can be disrupted, leading to areas of hyperexcitability (overactive neurons) or hypoexcitability (underactive neurons). This imbalance plays a key role in the symptoms and progression of MS, making it a critical area of focus for research and treatment.

How is brain excitability investigated, and what role does it play in MS?

Transcranial Magnetic Stimulation (TMS) is a non-invasive technique used to investigate brain excitability. It involves using magnetic pulses to stimulate specific areas of the brain and measure the resulting neuronal activity. Researchers use TMS on MS patients to quantify the excitability of each brain hemisphere, allowing them to calculate an asymmetry ratio. This ratio helps to identify imbalances in brain excitability, which can correlate with the severity of MS symptoms and help monitor disease progression. TMS offers a valuable tool for understanding the functional aspects of the brain in MS, providing insights beyond structural changes.

Why is brain excitability asymmetry significant in MS, and what are the implications?

The significance of brain excitability asymmetry in Multiple Sclerosis lies in its potential as a biomarker, and its implications are far-reaching. The asymmetry is linked to the severity of physical and cognitive symptoms. Monitoring brain excitability asymmetry could provide a way to track the progression of MS and assess the effectiveness of treatments. The understanding of brain excitability asymmetry provides new avenues for personalized MS treatment, potentially tailoring therapeutic interventions to address the specific imbalances present in each patient. This could involve using targeted therapies to reduce hyperexcitability or enhance activity, leading to improved symptom management.

How do personalized treatment approaches based on brain excitability work?

Personalized treatment approaches based on brain excitability aim to tailor interventions to address individual imbalances. By understanding a patient's unique brain excitability asymmetry, clinicians can potentially target specific imbalances, either reducing overactivity or enhancing underactivity in certain brain regions. This could involve new therapies designed to reduce hyperexcitability in one hemisphere or enhance activity in the other, ultimately leading to improved symptom management and a better quality of life. This approach moves beyond generalized treatments and allows for more precise and effective interventions based on an individual's specific neurological profile.