March is multiple sclerosis (MS) awareness month. MS is an autoimmune disease that affects over 900,000 individuals in the United States and millions of individuals across the world. MS is a disease of the central nervous system characterized by neuronal demyelination, chronic inflammation, neuronal loss, and gliosis. The clinical course is highly variable, ranging from mild symptoms to rapidly progressive, debilitating disease. MS is three times more common in women. The median age of onset is between 20-40. Risk factors include a genetic predisposition, prior Epstein-Barr virus (EBV) exposure vitamin D deficiency, and cigarette smoking.
The clinical manifestations of MS are also highly variable and symptoms are largely dependent on the location and severity of CNS lesions. Clinical manifestations may include paresthesias and other sensory impairments, optic neuritis, limb weakness, muscle spasticity, blurred vision, ataxia, vertigo, bladder dysfunction, facial myokymia, heat sensitivity, constipation, sexual dysfunction, cognitive dysfunction, fatigue, and Lhermitte’s symptom (an electric shock sensation radiating down the back into the legs most often induced by flexing the neck).
There are 3 clinical types of MS: Relapsing MS (RMS), secondary progressive MS (SPMS), primary progressive MS (PPMS). Relapsing or bout onset MS (RMS) accounts for 90% of cases. This type is characterized by attacks of neurologic dysfunction that develop over days to weeks. During initial attacks, patients have significant neurologic recovery in the coming months. As attacks continue, less recovery is experienced. Patients are neurologically stable between attacks. For patients with RMS, about 2% per year go on to develop SPMS. These patients experience deterioration in neurologic function unassociated with attacks. PPMS accounts for about 10% of cases. These patients do not suffer attacks, but rather have a steady decline in function from the time of disease onset.
There is no single diagnostic test to confirm MS. The diagnostic criteria for MS can be found HERE. MRI findings and evoked potentials can be used as part of the diagnostic workup. Differential diagnoses for MS may include, but are not limited to vasculitis, ischemic cerebrovascular disease, and acute disseminated encephalomyelitis (ADEM).
Full discussion of treatment is beyond the scope of this post and is individualized to the patient. Treatment is divided into management of acute attacks, maintenance therapy, and symptom management. Acute attacks are often managed with high-dose, short-term steroid therapy. Disease-modifying immunomodulatory and immunosuppressive agents are utilized for maintenance therapy. The choice of which agent is an individualized decision. Some commonly used agents include: Interferon β (Modestly Effective), Glatiramer Acetate (Modestly Effective), Fingolimod (Moderately Effective), Dimethyl Fumarate (DMF) (Moderately Effective), Natalizumab (Highly Effective), and Ocrelizumab (Highly Effective).
Read more about Multiple Sclerosis in:
Harrison's Principles of Internal Medicine, 20e: Chapter 436: Multiple Sclerosis