Atlas of pathophysiology, 2 Edition

Part II - Disorders

Neurologic disorders

Guillain-Barre syndrome

Also known as infectious polyneuritis, Landry-Guillain-Barré syndrome, or acute idiopathic polyneuritis, Guillain-Barré syndrome is a rapidly progressive and potentially fatal motor neuropathy of uncertain cause. Generally, the syndrome reaches its peak progress within 7 days to 4 weeks. Recovery occurs over weeks to months with approximately 10% to 25% of the population suffering with permanent weakness and disability.

Age Alert

The average age of onset of Guillain-Barré syndrome is 40.

Causes

An exact cause is unknown; however, in many of the cases the syndrome is preceded by a viral infection that produces a cell-mediated immune reaction. The most common infection is Campylobacter jejuni, occurring in about 30% to 40% of the cases. Epstein-Barré virus, cytomegalovirus, human immunodeficiency virus, coxsackievirus, herpes simplex, hepatitis A virus, and Mycoplasma pneumonia have also been implicated.

Other precipitating factors

·         Hematologic malignancies

·         Hyperthyroidism

·         Collagen vascular diseases

·         Sarcoidosis

·         Pregnancy

·         Surgical procedures

·         Transplants

·         Immunizations (swine flu)

·         Certain drugs (heroin)

Pathophysiology

Guillain-Barré syndrome is triggered by an autoimmune response in which the body's immune system starts to destroy the myelin sheath that surrounds the axons of many peripheral nerves, or even the axons themselves. It's possible that the virus changes the nature of the cells in the nervous system so that the immune system treats them as foreign cells. It's also possible that the virus makes the immune system itself less discriminating about what cells it recognizes, thereby allowing some of the immune cells, such as certain kinds of lymphocytes and macrophages, to attack the myelin. Sensitized T lymphocytes cooperate with B lymphocytes to produce antibodies against components of the myelin sheath and may contribute to destruction of the myelin as well.

Myelin destruction causes segmental demyelination of the peripheral nerves, preventing normal transmission of electrical impulses. Inflammation and degenerative changes in both the posterior (sensory) and anterior (motor) nerve roots result in signs of sensory and motor losses simultaneously. The autonomic nervous system may also be impaired.

Signs and symptoms

·         Symmetrical muscle weakness (major neurologic sign) appearing in the legs first (ascending type) and then extending to the arms and facial nerves within 24 to 72 hours

·         Muscle weakness developing in the arms first (descending type) or in the arms and legs simultaneously

·         Absent deep tendon reflexes

·         Paresthesia, sometimes preceding muscle weakness but vanishing quickly

·         Diplegia, possibly with ophthalmoplegia

·         Dysphagia and dysarthria

·         Hypotonia and areflexia

Diagnostic test results

·         Cerebrospinal fluid (CSF) analysis by lumbar puncture reveals elevated protein levels, peaking in 4 to 6 weeks, probably as a result of widespread inflammation of the nerve roots; the CSF white blood cell count remains normal, but in severe disease, CSF pressure may rise above normal.

·         Complete blood count shows leukocytosis with immature forms early in the illness, and then quickly returns to normal.

·         Electromyography possibly shows repeated firing of the same motor unit instead of widespread sectional stimulation.

·         Nerve conduction velocities show slowing soon after paralysis develops.

·         Serum immunoglobulin measurements reveal elevated levels from inflammatory response.

Treatment

·         Endotracheal intubation or tracheotomy, as indicated to clear secretions

·         Trial of prednisone to reduce inflammatory response

·         Plasmapheresis

·         Continuous electrocardiogram monitoring

·         I.V. immunoglobulin

·         Pain management, with anti-inflammatories and opioids

·         Rehabilitation

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PERIPHERAL NERVE DEMYELINATION

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