Multiple Sclerosis

A 28-year-old woman reports vision loss in one eye that resolved weeks ago — now the patient has leg numbness. The pattern of symptoms appearing, disappearing, and reappearing in different locations is the diagnostic fingerprint of MS.

Multiple sclerosis is an autoimmune demyelinating disease of the central nervous system. The immune system attacks the myelin sheath surrounding nerves in the brain and spinal cord, creating plaques (scleroses) that disrupt nerve signal transmission. The hallmark is symptoms that are disseminated in time and space — meaning they affect different CNS areas at different times. Relapsing-remitting MS (RRMS) is the most common form (~85%), characterized by acute exacerbations followed by partial or full recovery. Onset typically occurs between ages 20 and 40, more common in women. Key presenting symptoms include optic neuritis (unilateral vision loss with eye pain), sensory changes (numbness, tingling), Lhermitte sign (electric shock sensation down the spine with neck flexion), intention tremor, spastic weakness, and bowel/bladder dysfunction. Heat worsens symptoms (Uhthoff phenomenon) — even a warm bath can trigger temporary neurological decline. Diagnosis requires MRI showing white matter lesions disseminated in time and space (McDonald criteria), supported by oligoclonal bands in CSF. Acute relapses are treated with high-dose IV corticosteroids; disease-modifying therapies (interferons, glatiramer acetate) reduce relapse frequency. Fatigue is the most disabling and common symptom, often underestimated.

Key Distinctions

Don't confuse MS (CNS demyelination, relapsing-remitting, UMN signs like spasticity) with Guillain-Barré (PNS demyelination, ascending paralysis, LMN signs like flaccidity). Students mix up MS fatigue management with general fatigue — MS fatigue specifically worsens with heat and requires energy conservation and cooling strategies. Lhermitte sign is strongly associated with MS; Chvostek sign is hypocalcemia — don't swap them.

Clinical Pearl

MS hates heat. If a patient's neurological symptoms worsen after a hot shower, think MS first — cool the patient down and the symptoms improve.