In an acute attack, thyrotoxic PP must be distinguished from other causes of acute quadriparesis, such as myasthenic crisis, Guillain-Barré syndrome, acute myelopathy (eg, transverse myelitis), tick paralysis, and botulism [3,7]. The finding of hypokalemia generally alerts the clinician to the diagnosis of periodic paralysis, in which the possibility of thyrotoxicosis must always be evaluated, particularly in the absence of a family history. (See "Diagnosis of hyperthyroidism".) After a thyrotoxic state is established, the patient is further evaluated to determine the underlying cause. (See "Disorders that cause hyperthyroidism".)
The results of electromyography, provocative testing, and muscle biopsy are similar to those seen in familial hypokalemic PP, but these tests are often unnecessary