Thunderclap headache without hypertension in a patient with pheochromocytoma.

Pheochromocytoma is a well known, catecholamine-producing tumor characterized by hypertension, headache, hyperglycemia, hypermetabolism, and hyperhydrosis. Approximately 65% of cases of pheochromocytoma were shown to be associated with hypertension. A case of pheochromocytoma that presented with thunderclap headache (TCH) and palpitations is reported. The patient never showed hypertension during the course of the disease. Paroxysmal headache and palpitations led to the identification of the underlying condition, and the final diagnosis was confirmed by histopathological examination of a surgical specimen. Pheochromocytoma should be identified as a less common although important cause of TCH. In addition, due to its lack of utility in identifying this disorder, negative cranial imaging may impede further investigation of extracranial lesions that may be the cause of a patient's headache. According to the International Classification of Headache Disorders (ICHD)-II, headache attributed to pheochromocytoma usually develops concomitantly with an abrupt increase in blood pressure. In our case, however, hypertension was never observed, even when the patient was symptomatic. This is the first report of a case of pheochromocytoma with TCH without hypertension.