Thanks for using the forum. I am happy to address your questions, and my answer will be based on the information you provided here. Please make sure you recognize that this forum is for educational purposes only, and it does not substitute for a formal office visit with your doctor.
Without the ability to examine you and obtain a history, I can not tell you what testing you should specifically have. However I will try to provide you with some useful information.
I will assume by PNH you mean peripheral nerve hyperexcitability; if you meant something else, then the following discussion will not apply.
PNH is a disorder of spontaneous and continuous muscle overactivity. On EMG, spontaneous muscle activity (i.e. muscle activity that is not due to voluntary muscle activiation) is found, with specific types of discharges often found: myokymia being the broad term for them. PNH can be associated with the presence of certain antibodies, with an antibody against a specific nerve channel called voltage-gated potassium channel (VGKC) being the best described. The presence of VGKC in the blood can indicate one of two situations. One is an autoimmune disorder, whereby the body's immune system reacts against itself in the production of antibodies, for no apparent reason. The second is what is termed paraneoplastic, or the production of these antibodies due to the presence of a cancer in the blood. To my knowledge, there is not yet a blood test present to distinguish between the two, so that if the antibody is present, a search for a cancer is indicated. Often this will include a colonoscopy, CT scan of the chest, abdomen, and plevis, a mammogram, and other tests depending on the patient's age, sex, and other risk factors. Other autoimmune disorders are often present in patients with autoimmune VGKC antibodies and these should be further investigated as well. Treatment depends on the cause, but often includes immunosuppresion or plasmapharesis.
If the antibodies are negative, the PNH could be medication-induced, genetic, due to certain types of neuropathy, and other causes. The investigations in such cases would depend on other EMG findings and other medical history and clinical and examination features.
Continued follow-up with your physicians is recommended. Evaluation at a center experienced with PNH is recommended, and in such cases, a tertiary care hospital (associated with a university hospital, an academic center) in your area is often preferable, where there are neuromuscular specialists familiar with this disorder.
Thank you for this opportunity to answer your questions, I hope you find the information I have provided useful, good luck.
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