Fatigue in multiple sclerosis represents one of the most debilitating and pervasive symptoms experienced by patients with relapsing-remitting multiple sclerosis (RRMS). Although clinicians frequently encounter this symptom, its long-term progression patterns and specific anatomical drivers have historically remained challenging to predict. Researchers from the Queen Square Multiple Sclerosis Centre conducted a landmark prospective investigation within the Predicting Optimal Individualised Treatment response in MS (POINT-MS) cohort. This study tracked adult patients initiating disease-modifying therapy over eighteen months to characterize distinct physical and cognitive fatigue trajectories. Using advanced growth mixture modeling, investigators delineated distinct patient subsets and identified critical neuroimaging and clinical predictors. Consequently, the research provides novel insights into why fatigue worsens rapidly in select individuals while remaining manageable or improving in others. Clinicians routinely struggle to treat MS-related exhaustion with conventional symptomatic pharmacotherapy. Therefore, objective imaging biomarkers and longitudinal trajectory mapping offer an essential foundation for tailored neurological interventions. Understanding these data-driven trajectories allows clinicians to recognize vulnerable patients early, optimize disease-modifying regimens, and address structural central nervous system injury before irreversible disability sets in.

Mapping Trajectories of Fatigue in Multiple Sclerosis

The prospective study enrolled 225 adult participants with relapsing-remitting multiple sclerosis who underwent standardized longitudinal assessments at baseline, six months, and eighteen months. Investigators evaluated both cognitive and physical subscales of the Modified Fatigue Impact Scale across all intervals. Applying growth mixture modeling revealed three distinct longitudinal trajectories for both cognitive and physical domains: improving, stable or mildly worsening, and worsening classes. In the worsening cohort, patients demonstrated substantial annualized score increases of +3.32 points per year on the cognitive subscale and +3.37 points per year on the physical subscale. Conversely, patients within the improving trajectory experienced meaningful reductions in perceived symptom burden over time. These divergent trajectories prove that fatigue in multiple sclerosis does not follow a uniform course across the patient population. Instead, symptom progression manifests heterogeneously, reflecting distinct biological and structural disease phenotypes. Furthermore, identifying these separate pathways underscores the inadequacy of static single-time-point evaluations. Neurologists must incorporate serialized subjective scoring tools alongside objective paraclinical evaluations to track disease evolution accurately and intervene before functional decline accelerates.

Cervical Spinal Cord Atrophy as a Key Biomarker

To uncover structural determinants of symptom progression, researchers integrated high-resolution neuroimaging assessments into multivariable predictive models. Specifically, investigators analyzed cervical spinal cord cross-sectional area alongside brain volumetrics normalized to healthy controls. Conditional random forest analysis demonstrated that smaller baseline cervical spinal cord cross-sectional area was the strongest magnetic resonance imaging predictor of worsening fatigue trajectories. In contrast, regional brain volumes showed less predictive power regarding symptom deterioration over the observation period. Structural spinal cord damage occurs early in demyelinating disease, yet routine clinical practice frequently overlooks cord volumetrics in favor of cerebral imaging alone. Consequently, progressive cord thinning indicates accumulated axonal destruction and persistent neurodegeneration. When baseline cervical cord cross-sectional area declines, patients exhibit significantly higher susceptibility to deteriorating cognitive and motor stamina. Therefore, quantitative cervical cord measurements supply crucial prognostic information that brain MRI alone cannot capture. Clinicians should increasingly consider cord cross-sectional area as an indispensable prognostic biomarker when stratifying risk for refractory fatigue.

The Neurobiological Role of Thalamocortical Pathways

The pronounced association between cervical spinal cord atrophy and progressive fatigue highlights important neurobiological mechanisms linking physical lesions to cognitive stamina. Ascending somatosensory axons passing through the cervical spinal cord transmit peripheral sensory signals directly toward the thalamus. When chronic inflammatory injury and neuroaxonal loss compromise these ascending spinal tracts, afferent input to the thalamus diminishes significantly. As a result, disrupted ascending stimulation impairs thalamocortical loop activation and suppresses cortical arousal networks. This breakdown in thalamocortical drive directly contributes to the severe cognitive exhaustion and central motor fatigue observed in worsening cohorts. Neuroscientists previously regarded cognitive fatigue primarily as a consequence of frontoparietal neocortical disruption or diffuse cerebral white matter lesions. However, these prospective data confirm that subcortical and spinal tract pathology plays an equally decisive role in modulating mental arousal and physical endurance. Consequently, intact spinal sensory conduction remains fundamental for maintaining normal thalamocortical physiological rhythm and sustaining daily cognitive energy.

Clinical Impact of Disease-Modifying Therapy Coverage

Beyond neuroimaging metrics, the investigators examined numerous demographic, functional, and therapeutic baseline variables to isolate clinical determinants of long-term fatigue progression. Interestingly, multivariable modeling identified the proportion of total disease duration spent on disease-modifying therapies as the most influential clinical predictor of trajectory status. Patients with extensive lifetime disease-modifying therapy exposure demonstrated significantly greater protection against severe symptom worsening compared to those with delayed or intermittent therapeutic coverage. Early and continuous treatment suppresses inflammatory activity, preserves axonal integrity, and prevents irreversible neuroaxonal loss in critical spinal and cerebral tracts. Conversely, prolonged periods without effective disease-modifying treatment allow subclinical inflammatory cascades and insidious axonal atrophy to progress unchecked. Therefore, timely implementation of high-efficacy therapy is vital not only for reducing clinical relapse rates but also for mitigating chronic symptomatic deterioration. Neurologists should highlight these findings during shared decision-making discussions to encourage early therapeutic initiation and maintain strict medication compliance over the entire disease course.

Translating Prognostic Models into Clinical Practice

Integrating data-driven predictive tools into routine neurological care could substantially enhance management algorithms for relapsing-remitting multiple sclerosis. Clinicians frequently encounter patients who report debilitating exhaustion despite stable cerebral MRI findings and low Expanded Disability Status Scale scores. By acknowledging the prognostic value of cervical spinal cord area and prior therapy duration, clinicians can identify vulnerable individuals before severe symptomatic worsening develops. Comprehensive care pathways should combine serial Modified Fatigue Impact Scale measurements, quantitative spinal imaging analysis, and timely optimization of disease-modifying regimens. Furthermore, patients categorized into high-risk worsening trajectories can benefit from multimodal supportive interventions, including aerobic conditioning, energy conservation therapy, and cognitive rehabilitation. Multidisciplinary care teams should actively address contributing cofactors such as mood disorders and sleep dysfunction alongside structural neuroprotection. Ultimately, moving beyond reactive symptomatic treatment toward proactive, biomarker-guided risk stratification empowers physicians to preserve both cognitive vitality and functional independence in individuals living with multiple sclerosis.

Frequently Asked Questions

What are the primary fatigue trajectories in multiple sclerosis?

Clinical research identifies three distinct longitudinal fatigue trajectories in relapsing-remitting multiple sclerosis: improving, stable or mildly worsening, and progressively worsening. In the worsening trajectory, patients experience significant annualized score increases on both physical and cognitive subscales of validated fatigue instruments. Recognizing these distinct patterns helps clinicians understand that symptom progression is heterogeneous, requiring early personalized monitoring rather than assuming a uniform disease course across all individuals.

How does cervical spinal cord atrophy influence fatigue in multiple sclerosis?

Cervical spinal cord cross-sectional area serves as a powerful neuroimaging predictor of fatigue progression. Chronic atrophy reflects axonal loss within ascending somatosensory pathways traversing the cord. When these tracts suffer damage, afferent signals to the thalamus decrease, thereby impairing thalamocortical drive and central cortical arousal. Consequently, spinal structural loss directly undermines both physical endurance and cognitive energy levels in patients.

Can early initiation of disease-modifying therapy mitigate progressive fatigue?

Yes, clinical evidence indicates that spending a greater proportion of total disease duration on disease-modifying therapies provides substantial protection against worsening fatigue trajectories. Continuous therapeutic coverage suppresses chronic neuroinflammation, reduces cumulative axonal damage, and preserves spinal cord structural volume. Therefore, prompt treatment initiation and consistent medication adherence remain vital strategies for maintaining long-term energy, cognitive vitality, and overall quality of life.

Disclaimer: This content is for informational and educational purposes only. It is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Refer to the latest local and national guidelines for clinical practice.

References

1. Cruciani A et al. Data-Driven Fatigue Trajectories in Multiple Sclerosis and Their Predictors. Neurol Neuroimmunol Neuroinflamm. 2026 Sep undefined. doi: 10.1212/NXI.0000000000200643. PMID: 42607283.
2. Englund S et al. Trajectories of self-reported fatigue following initiation of multiple sclerosis disease-modifying therapy. J Neurol Neurosurg Psychiatry. 2024;95(11):1038-1046. doi: 10.1136/jnnp-2024-333595.
3. Kearney H et al. Cervical cord atrophy and disability in multiple sclerosis: A 5-year follow-up study. Mult Scler. 2014;20(10):1403-1407. doi: 10.1177/1352458514524996.