Coma and brain stem areflexia in brain stem encephalitis (Fisher's syndrome).

The assessment of brain stem function in comatose patients is now regular medical practice world wide. When envisaging a diagnosis of brain stem death it is essential, firstly, to establish that the patient is suffering from irremediable structural brain damage of known cause, and, secondly, to exclude the primary or contributory role of reversible causes of apnoeic coma with absent brain stem reflexes. Such causes include drug intoxication, hypothermia, and metabolic and endocrine disturbances. Brain stem encephalitis (Bickerstaff's encephalitis, Miller Fisher syndrome) is characterised by acute ophthalmoplegia, ataxia, and areflexia.47 In unusually severe cases the patient may be comatose and apnoeic and there may be complete paralysis of the motor functions of the cranial nerves.6 We describe three patients with this condition in whom brain stem areflexia was associated with apnoeic coma. None of them met the first precondition for a diagnosis ofbrain stem death, emphasising the importance of the necessary preconditions for making such a