A problem arises in distinguishing generalized GBS with ophthalmoparesis or the Fisher variant from basilar artery thrombosis. The presence of reactive pupils, areflexia, and F-wave abnormalities in GBS, and of lively reflexes and Babinski signs in the case of brainstem infarction, dependably separate the disorders. Ptosis and oculomotor weakness in GBS causes confusion with myasthenia gravis, but there are no sensory symptoms and the tendon reflexes are unimpaired in the latter disease. The mandibular muscles remain relatively strong in GBS, whereas the exercised jaw hangs open in myasthenia. Botulism also simulates this cranial variant of GBS, but pupillary reflexes are lost early in botulism (pupillary paralysis occurs mainly in advanced cases of GBS) and there is usually a bradycardia, which is unusual for GBS. Ingestion of shellfish or reef fish contaminated with saxitoxin, ciguatoxin, or tetrodotoxin (ciguatera, neurotoxic shellfish poisoning) is another cause of facial-brachial paresthesias, weakness, tachypnea, and iridoplegia lasting up to a few days—symptoms that resemble the cranial nerve variants of GBS.
A number of neuromuscular disorders in critically ill patients with systemic medical conditions are difficult to distinguish from GBS. These include the polyneuropathy of critical illness (see further on in the chapter); an accelerated neuropathy of renal failure that is seen mainly in diabetic patients receiving peritoneal dialysis (both discussed further on); acute hypophosphatemia induced by hyperalimentation; polymyopathy produced by the administration of high-dose corticosteroids; and the prolonged effects of neuromuscular blocking drugs, resulting in the accumulation of their metabolites in patients under conditions of renal failure and acidosis.
General medical care In severe cases, respiratory assistance and assiduous nursing are paramount, because the disease remits naturally and the outlook for recovery is favorable in the majority of patients. About one-quarter of our patients have required mechanical ventilation. Because a patient’s condition may deteriorate unpredictably and rapidly in the first days of illness, virtually all but the mildest cases should be admitted to the hospital for observation of respiratory, autonomic, and motor function. The comments that follow are applicable to most other forms of acute and subacute neuromuscular respiratory failure, including myasthenia gravis and high spinal cord injury.