**Core Concept**
The patient's symptoms and laboratory findings are consistent with a diagnosis of pheochromocytoma, a catecholamine-secreting tumor that leads to episodic hypertension due to excessive release of epinephrine and norepinephrine.

**Why the Correct Answer is Right**
The elevated plasma norepinephrine (450 pg/mL) and epinephrine (115 pg/mL) levels are indicative of an excess of these catecholamines, which are typically produced by the adrenal medulla. The 24-hour urinary vanillylmandelic acid (VMA) level is also elevated (11 mg), which is a metabolite of catecholamines. This combination of findings is highly suggestive of a pheochromocytoma, a tumor of the adrenal gland that secretes excess catecholamines.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because primary aldosteronism is characterized by excessive production of aldosterone, leading to hypertension, but the laboratory findings in this case are more consistent with catecholamine excess.

**Option B:** Renal artery stenosis is a cause of secondary hypertension, but it would not typically be associated with elevated plasma catecholamine levels.

**Option C:** Cushing's syndrome is characterized by excessive production of cortisol, which can lead to hypertension, but the laboratory findings in this case are more consistent with catecholamine excess.

**Option D:** This option is incorrect because essential hypertension is a common cause of hypertension, but it would not typically be associated with the specific laboratory findings seen in this case, such as elevated plasma catecholamine levels and 24-hour urinary VMA.

**Clinical Pearl / High-Yield Fact**
When evaluating a patient with episodic hypertension, it is essential to consider the possibility of a catecholamine-secreting tumor, such as a pheochromocytoma, especially if there is evidence of catecholamine excess on laboratory testing.

**Correct Answer:** C. Pheochromocytoma.