Cavernous sinus sampling

Abstract

I NTERVENTIONAL neuroradiology now plays a role in the diagnosis of Cushings disease. The disease is characterized by an increased production of corticosteroids, leading to the classic features: increase in central body weight with sparing of the extremities, increased body hair, pliable skin, hypertension, and hyperglycemia. The release of corticosteroids from the adrenal gland is controlled by a negative feedback mechanism. Corticotropin is released from the hypothalamus and travels to the anterior pituitary gland via a portal venous system. Corticotropin stimulates the release of adrenocorticotrophic hormone (ACTH) from the anterior pituitary gland. This hormone stimulates the production and secretion of corticosteroids from the adrenal cortex. The increase of corticosteroid levels in the blood has a negative feedback effect on further release of corticotropin from the hypothalamus. An excess of corticosteroids may thus be caused by an ACTH-secreting pituitary adenoma or an adrenal cortex adenoma, or an ectopic ACTHsecreting tumor. Usually, magnetic resonance imaging scans of the brain will show an enlarged pituitary gland if the location of the tumor is in the anterior pituitary gland. However, in some patients the precise location of the adenoma is unclear. It is thus necessary to stimulate secretion of the pituitary gland by corticorelin and sample cavernous sinus and peripheral venous blood samples for levels of the ACTH. 1'2 The procedure is fairly simple. Using biplane angiography, bilateral femoral venous catheters are inserted. The microcatheters are advanced bilaterally into each cavernous sinus. Baseline blood samples from the periphery and cavernous sinus are sent as indicated in Fig 1. Corticorelin is then injected intravenously, and samples of blood are taken bilaterally from each of the areas as indicated at intervals of 5, 10, 15, and 20 minutes (Fig 2). The anesthesia considerations for this procedure are dictated by the pathophysiology of Cushing's disease. These patients are often hypertensive and have elevated serum glucose levels. Care must be taken in positioning the patient and protecting their extremities because they have such fragile tissues. Their obesity may make airway management, intubation, and securing intravenous access very difficult. The procedure may be done under local or general anesthesia. Our interventional neuroradiologist usually prefers general anesthesia for these cases unless there are good reasons to do this with intravenous sedation plus local anesthesia. The procedure is done on an out-patient basis, and there should be minimal post-procedure pain or complications.