How does fever exacerbate multiple sclerosis (MS) symptoms?

How Fever Exacerbates Multiple Sclerosis Symptoms

Fever causes temporary worsening of MS symptoms primarily through temperature-dependent slowing or blocking of neural conduction in demyelinated nerve fibers, which can affect sensory, motor, and cognitive function. 1

Mechanism of Fever-Induced Symptom Worsening

• Increases in body temperature (even small elevations) lead to temperature-dependent slowing or blocking of neural conduction within the central nervous system, particularly affecting demyelinated nerve fibers 1
• Core temperature elevation of as little as 0.37°C can significantly worsen MS symptoms, demonstrating the sensitivity of demyelinated neurons to temperature changes 2
• The exacerbation of symptoms during fever is temporary and typically resolves when body temperature returns to normal 1

Common Symptoms Exacerbated by Fever

• Fatigue is the most commonly reported symptom that worsens with temperature elevation in MS patients 3
• Ambulatory dysfunction (walking difficulties) becomes more pronounced during fever episodes 2
• Visual disturbances may temporarily worsen during periods of elevated body temperature 2
• Cognitive function, particularly concentration, can deteriorate during fever 3
• Sensory symptoms such as numbness or tingling may intensify with increased body temperature 1

Temperature Sensitivity Patterns in MS

• Approximately 60-80% of MS patients experience temperature sensitivity, making it a highly prevalent characteristic of the disease 1
• Different patterns of temperature sensitivity exist among MS patients: 58% are heat-sensitive only, 29% are both heat and cold sensitive, and 13% are cold-sensitive only 3
• Individual factors such as age, level of motor disability, and baseline fatigue can predict greater susceptibility to temperature-related symptom exacerbation 3

Management Strategies for Fever in MS

• Prompt treatment of underlying infections causing fever is essential to minimize symptom exacerbation 4
• Controlled normothermia (targeting core temperature 36.0-37.5°C) should be considered when fever occurs in MS patients 4
• Head and neck cooling has been shown to improve ambulatory function in heat-sensitive MS patients by decreasing core temperature 2
• Antipyretics may provide symptomatic relief during fever episodes 4
• Environmental modifications such as air conditioning and appropriate clothing can help manage temperature sensitivity 3

Clinical Considerations and Pitfalls

• Fever in MS patients may be mistaken for an MS relapse (pseudo-relapse) when it is actually a temporary exacerbation of existing symptoms due to temperature elevation 4
• MS patients on immunomodulatory therapies may have altered immune responses and be more susceptible to infections causing fever 5
• It's important to distinguish between true disease progression and temporary symptom worsening due to fever, as management approaches differ significantly 1
• Experimental treatments that induce fever (like poly ICLC) have been observed to cause transient worsening of neurologic symptoms in MS patients, further confirming the temperature-symptom relationship 6