The patient's clinical picture was at first interpreted as psychogenic paroxysmal dyskinesias (PxDs), although main diagnostic features suggesting a functional ethiology were missing. Owing to the absence of specific triggers and to the attack's duration, PxDs resulting from PRRT2 gene mutations might have been considered in our case, given the duration of attacks, lack of nonkinesigenic triggers, and mixed choreodystonic phenomenology. However, given the negative familial history and the age at onset, it is mandatory to exclude secondary forms of paroxysmal movement disorders (PMDs). Indeed, several conditions, most of them treatable, may cause PMDs, such as hypoparathyroidism, pseudohypoparathyroidism, and cerebrovascular diseases. Hypoglycemia is a rare cause of PMD and can be caused by an insulinoma (sporadic or within a multiple endocrine neoplasia [MEN] syndrome) or by a paraneoplastic syndrome.Given its insidious nature, this condition is still a diagnostic challenge. Detecting a low glucose level may be difficult because of the erratic activity of neoplastic cells, so serial samples analyses should be performed. Hypoglycemic condition, even if asymptomatic (hypoglycemia unawareness), is highly suggestive for insulinoma. Once suspected, CT scan remains the investigation of choice, confirming the presence of neoplastic tissue, localizing the site of surgery, and helping in differential diagnoses between sporadic cases and MEN syndrome. Given the high rate of success, patients should be referred to surgery, when contraindicated oral therapy remains a suitable option.
In conclusion, our final diagnosis was paroxysmal dystonic-dyskinetic syndrome and axonal motor neuropathy resulting from insulinoma. The complete remission of neurological symptoms after the tumor's excision strongly supports the correlation between both PNS and CNS symptoms and impaired glucose metabolism.[6-10] Genetic progress is improving our understanding in PMD, but formulating a proper presumptive diagnosis remains an essential requirement. An accurate anamnestic and symptoms record, and a high grade of suspect and several observations are crucial to pursue the recognition of this diagnostically challenging condition.