Multiple Sclerosis – Top USMLE Diseases

Guillain-Barré syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Typical GBS is characterized by acute monophasic neuromuscular paralysis, which is symmetric and ascending in progression. If the paralysis reaches the respiratory muscles, GBS can progress into respiratory failure, which requires prolonged hospitalization. Management is mostly supportive and may require either plasma exchange or IV immunoglobulin.

Acute disseminated encephalomyelitis (ADEM) is an immune-mediated, inflammatory, monophasic, demyelinating condition that affects the white matter of the brain and spinal cord. As a rapidly progressive post-infectious encephalomyelitis, ADEM is characterized by demyelination in the brain and spinal cord as a result of inflammation following infection or immunization.

Immunosuppressants are a class of drugs widely used in the management of autoimmune conditions and organ transplant rejection. The general effect is dampening of the immune response. There are multiple targets in the immune system, as well as varied mechanisms in inhibiting inappropriate immune activity. Biologic agents are medications derived from living organisms that target particular components of the immune system. The targets can be tumor necrosis factor (TNF), interleukins (ILs), or B- or T-cell activity. Calcineurin inhibitors halt the activity of calcineurin, a phosphatase involved in T-cell activation. Corticosteroids interfere with the cell cycle of inflammatory cells and modify the activity of other immune components. mTOR inhibitors are proliferation signal inhibitors, reducing immune-cell proliferation. Some immunosuppressants, such as cytotoxic agents, have antineoplastic activity; these are used in rheumatoid arthritis, as prophylaxis for transplant rejection, and for malignant diseases.

Guillain-Barré syndrome (GBS), once thought to be a single disease process, is a family of immune-mediated polyneuropathies that occur after infections (e.g., with Campylobacter jejuni). Typical GBS is characterized by acute monophasic neuromuscular paralysis, which is symmetric and ascending in progression. If the paralysis reaches the respiratory muscles, GBS can progress into respiratory failure, which requires prolonged hospitalization. Management is mostly supportive and may require either plasma exchange or IV immunoglobulin.

Internuclear ophthalmoplegia (INO) is an ocular movement disorder that affects the conjugate horizontal gaze, meaning the eyes are incapable of moving in a simultaneous and coordinated manner on the horizontal plane. This disorder is usually caused by a lesion in the brain stem involving the medial longitudinal fasciculus (MLF) and is characterized by impaired adduction ipsilateral to the MLF lesion and abduction nystagmus contralateral to the MLF lesion. Internuclear ophthalmoplegia is a clinical diagnosis. However, investigations involving neuroimaging, especially MRI, help establish the diagnosis. Management of INO varies depending on the cause. The prognosis mainly depends on the etiology. For instance, trauma patients do not have a very favorable prognosis, whereas patients with ischemic and demyelinating causes have a favorable recovery.

Multiple sclerosis (MS) is a chronic inflammatory autoimmune disease that leads to demyelination of the nerves in the CNS. Young women are more predominantly affected by this most common demyelinating condition. The etiology of MS is unclear; however, both genetic and environmental factors are believed to play a role. The clinical presentation varies widely depending on the site of lesions, but typically includes neurological symptoms that affect vision, motor functions, sensation, and autonomic function. The diagnosis is made via MRI of the entire CNS (brain and spine) as well as CSF examination. Management involves corticosteroids for acute exacerbations and disease-modifying agents to reduce these exacerbations and slow disease progression. The average life expectancy of individuals with MS is decreased by 5–10 years.