Multiple Sclerosis is a chronic, unpredictable autoimmune disease of the central nervous system, affecting the brain and spinal cord. The immune system mistakenly attacks the myelin sheath, the protective layer around nerve fibers, causing inflammation and damage. This damage disrupts the flow of electrical signals, leading to various neurological symptoms. A “flare,” also known as a relapse or attack, is a period characterized by the sudden appearance of new symptoms or the significant worsening of existing ones. Understanding the specific sensations and timeline of a flare is important for people with MS and their care providers.
The Subjective Physical Sensations of a Flare
The physical sensations experienced during a flare depend on the location of the inflammation and damage within the central nervous system. Sensory changes (paresthesia or dysesthesia) are common, manifesting as numbness, “pins and needles,” burning, crawling, or intense itching. Lhermitte’s sign is a brief electric-shock sensation traveling down the spine when the neck is bent forward.
Motor changes often present as new or increased weakness, interfering with walking or gripping objects. Muscle stiffness (spasticity) can intensify, making movement difficult. Damage to the cerebellum or brainstem may cause ataxia, resulting in a loss of balance and coordination.
Vision changes are often due to optic neuritis, inflammation of the optic nerve. This can cause pain behind the eye, especially when moving it. Vision may become blurred, colors may appear washed out, or a blind spot may develop.
A distinct form of fatigue is a hallmark of MS flares. This exhaustion is not relieved by sleep or rest and interferes with daily activities.
Duration and Intensity
For symptoms to be considered a flare, the new or worsening neurological symptoms must persist for at least 24 hours. This duration requirement distinguishes a relapse from transient, day-to-day fluctuations. The onset can be sudden, appearing over a few hours, or gradual, worsening over several days before reaching peak intensity.
The recovery phase is highly variable, with relapses typically lasting anywhere from a few days to several weeks or months. While some people return entirely to their previous baseline function, others may be left with permanent residual symptoms.
Flares exist on a broad spectrum, ranging from mild sensory symptoms to severe attacks causing vision loss or mobility impairment. Severity relates directly to the location and extent of inflammatory damage. Mild flares may resolve without treatment, but severe impairment often requires high-dose corticosteroids to reduce inflammation.
Differentiating a True Relapse from Temporary Worsening
Differentiating a true inflammatory relapse from a temporary worsening of symptoms (a pseudo-flare or pseudoexacerbation) is important for proper management. A true relapse involves new inflammatory activity and damage, often confirmed by finding new or active lesions on an MRI scan. This worsening signifies active disease and may require a change in long-term treatment.
A pseudo-flare involves no new inflammation or damage and does not create new lesions. It is a transient event where existing MS symptoms temporarily worsen, usually lasting less than 24 hours. These setbacks are caused by external factors that increase the body’s internal temperature or stress the nervous system.
Common triggers include heat or fever (known as Uhthoff’s phenomenon), infections like a urinary tract infection, physical stress, and overexertion. When the underlying trigger is identified and removed, the symptoms of the pseudo-flare resolve quickly. The key distinction is that a true relapse involves new damage, while a pseudo-flare is a reversible, transient increase in existing symptoms.