Hypokalemic Periodic Paralysis - Diagnosis

Diagnosis

Patients often report years wasted with wrong diagnosis, wrong treatments, deadends and multiple doctors, test and clinics. The CMAP (Compound Muscle Amplitude Potential) test, also called the exercise EMG or X-EMG, is diagnostic in 70–80% of cases when done correctly. Besides the patient history or a report of serum potassium low normal or low during an attack, the CMAP is the current standard for medical testing. Genetic diagnosis is often unreliable as only a few of the more common gene locations are tested, but even with more extensive testing 20–37% of people with a clinical diagnosis of hypokalemic periodic paralysis have no known mutation in the two known genes. Standard EMG testing cannot diagnose a patient unless they are in a full blown attack at the time of testing. Provoking an attack with exercise and diet then trying oral potassium can be diagnostic, but also dangerous as this form of PP has an alternate form known as hyperkalemic periodic paralysis. The symptoms are almost the same, but the treatment is different. The old glucose insulin challenge is dangerous and risky to the point of being life threatening and should never be done when other options are so readily available.

People with hypokalemic periodic paralysis are aften misdiagnosed as having a conversion disorder or hysterical paralysis since the weakenss is muscle based and doesn't correspond to nerve or spinal root distributions. The tendency of people with hypokalemic periodic paralysis to get paralyzed when epinephrine is released in "fight or flight" situations further adds to the temptation to dismiss the disorder as psychiatric.