Adolescents show higher possible mitochondrial inheritance and maternal inheritance than found in adults. Single base-pair and DNA rearrangements in the mitochondrial DNA (mtDNA) have been associated with these traits. Diagnosis
The cause of CVS has not been determined and there are no diagnostic tests for CVS. Several other medical conditions, such as cannabinoid hyperemesis syndrome (CHS), can mimic the same symptoms, and it is important to rule these out. If all other possible causes have been excluded, a diagnosis of CVS using Rome criteria by a physician may be appropriate.Once formal investigations to rule out gastrointestinal or other causes have been conducted, these tests do not need to be repeated in the event of future episodes. Diagnostic criteria
Due to the lack of specific biomarkers available for the disorder, and if all other possible causes can be ruled out (such as intestinal malrotation), physicians rely on the Rome IV process criteria in order to diagnose patients. Patients must meet all three of the following criteria to receive diagnosis: 

Stereotypical episodes of acute vomiting each with a duration of less than 1 week
A history of at least three discrete episodes in the prior year and at least two episodes in the past 6 months, each occurring at least 1 week apart
An absence of vomiting between episodes, but other milder symptoms can be present between cyclesCriteria must be fulfilled for the last 3 months with symptom onset at least 6 months prior to diagnosis. A history of family history of migraine headaches can also be used in facilitating diagnosis.
Some acute TM patients may present symptoms of blurred vision and bulging eyes due to eye muscle degradation and inflammation, but documented cases are rare. Acute TM patients usually have very weak respiratory muscles and often severe respiratory failure occurs. Cause
TM is directly related to thyroxine toxicity. It is believed this disorder is a direct result of hyperthyroidism, specifically hyperthyroidism caused by Graves disease or a multinodular goiter. Both cause the thyroid gland to overproduce thyroxine. A multinodular goiter is a condition where the thyroid develops nodules. Overproduction of thyroxine is due to the enlargement of the thyroid gland. Graves disease is an autoimmune condition where the immune system chronically stimulates the TSH receptor in the thyroid and induces overproduction of the thyroxine hormone. Pathophysiology
Excess thyroxine is believed to bring about the onset of thyrotoxic myopathy and eventually cause the degradation of muscle tissue. Thyroxine is a hormone produced in the thyroid gland that regulates the growth metabolism of the nervous system and regulates basal metabolic rate of many cell types. Scientists agree thyroxine brings about the degradation of muscle fibers specifically at the motor end plates of neuromuscular junctions. There is debate as to whether thyroxine degrades the motor end plates from the muscular side, from the nervous system side, or a combination.To understand how high levels of thyroxine can be toxic and lead to thyrotoxic myopathy physiologically, consider basic neuromuscular junction function.