Brachial plexus neuritis Ref: Basic neurology [By John Gilroy 3/e p594; "Brachial plexus neuritis is characterized by a sudden paralysis of muscles supplied through the brachial plexus and is often associated with painful dysesthesia of the arm. The condition occurs in known viral infections (herpes zoster, Epstein-Barr virus), following injections of tetanus toxoid, in putative viral infections; and as an autobnmune disorder following a surgical procedure."- Basic neurology By John Gilroy 3/e p594 Brachial plexus neuritis usually is characterized by the acute onset of excruciating unilateral shoulder pain, followed by flaccid paralysis of shoulder and parascapular muscles several days later. The syndrome can vary greatly in presentation and nerve involvement. Brachial neuritis (BN) exists in an inherited and an idiopathic form. In the idiopathic version, the pathophysiology is unknown, but the condition is generally thought to be an immune system - mediated inflammatory reaction against nerve fibers of the brachial plexus. The onset of pain in brachial neuritis (BN) is often abrupt and may follow recent illness, surgery, immunization, or even trauma (see Causes, below). Up to two thirds of cases begin during the nighttime. Sensory abnormalities are of usually of less intensity than the pain and muscle weakness. Causes: The exact cause of brachial neuritis is unknown, but the condition has been linked to many antecedent events or illnesses, as follows: Viral infection (paicularly of the upper respiratory tract) Bacterial infection (eg, pneumonia, diphtheria, typhoid) Parasitic infestation S urgery 2 Trauma (not related to shoulder) Vaccinations (eg, influenza, tetanus, diphtheria, tetanus toxoids, peussis [DPT J. smallpox, swine flu) Childbih Miscellaneous medical investigative procedures (eg, lumbar puncture, administration of radiologic dye) Systemic illness (eg, polyaeritis nodosa, lymphoma, systemic lupus erythematosus, temporal aeritis, EhlersDanlos syndrome) A rarer, hereditary form of BN has been localized to the SEPT9 gene on chromosome arm 17q and should be considered a distinct disorder. This entity presents in a younger age group, and is characterized by recurrent, often bilateral attacks. Dysmorphic facial features (eg, hypotelorism, long nasal bridge, facial asymmetry) can also be present. Diagnosis: Other causes of severe pain, such as an acute herniated cervical disc, should be excluded. In brachial plexus neuritis, electromyography and nerve conduction studies reveal abnormalities in more than one nerve; in contrast, cervical radiculopathy may show osteophytes and interspace narrowing on cervical spine x-rays and neuroforaminal disc impingement of MRI. Treatment: of brachial plexus neuritis is suppoive, with analgesics for pain, physical therapy to maintain shoulder strength/mobility, and reassurance that the condition generally will improve, albeit slowly.