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What is Bickerstaff brainstem encephalitis and explain in detail?
Bickerstaff brainstem encephalitis is a rare inflammatory disorder of the central nervous system, first described by Edwin Bickerstaff in 1951. It may also affect the peripheral nervous system, and has features in common with both Miller Fisher syndrome and Guillain–Barré syndrome.

Signs and symptoms
In order to diagnose Bickerstaff brainstem encephalitis, ataxia and ophthalmoplegia must be present. These are also diagnostic features of Miller Fisher syndrome, and so Bickerstaffs is only diagnosed if other features are present which exclude Miller Fisher syndrome. These may include drowsiness, coma or hyperreflexia. When the condition is defined in this way, a number of other features are commonly but not always found: among these are weakness of the limbs, the face, and/or the bulbar muscles; abnormalities of the pupils; and absent reflexes.Like some other autoimmune diseases, the condition usually follows a minor infection, such as a respiratory tract infection or gastroenteritis.

Pathophysiology
The clinical features and course of the condition, the associated auto-antibodies against relevant antigens, and the response to treatment, all suggest that Bickerstaff brainstem encephalitis is an autoimmune disease. However, each of these criteria fails to fit a substantial proportion of patients, and there is no single test or feature which is diagnostic of Bickerstaff brainstem encephalitis