Applied Radiology

CASE SUMMARY:

A 45-year-old woman with a history of depression and headaches presented after an MRI examination raised the question of a possible pseudoaneurysm of the right internal carotid artery. She had no history of significant trauma to the neck or else-where, and no history of hypertension. On physical examination, the patient was alert and oriented. She had full strength and sensation in all four extremities. Her cranial nerve examination was remarkable for unequal pupils, the right pupil being approximately 2 mm smaller than the left; however, both pupils were reactive. The patient had not recognized her own pupillary asymmetry and therefore could not establish a date at which this finding may have occurred. Her neurologic examination was otherwise within normal limits. What is the most likely diagnosis?

FIGURE 1. A common carotid artery injection demonstrates a high cervical internal carotid artery pseudoaneurysm measuring approximately 11×5 mm with a 5-mm neck.

FIGURE 2. A Palmaz-Schatz stent on a 3.4 microcatheter positioned across the neck of the pseudoaneurysm.

FIGURE 3. This radiograph demonstrates the stent deployed in the internal carotid artery.

FIGURE 4. This common carotid artery arteriogram demonstrates the appearance poststenting and coil placement.

DIAGNOSIS:

A cerebral arteriogram revealed that the patient had a moderately wide-necked pseudoaneurysm arising from the distal cervical internal carotid artery, quite possibly resulting from an unrecognized dissection secondary to fibromuscular dysplasia (FMD). The aneurysm measured approximately 11×5 mm with a 5-mm neck (figure 1).

CLINICAL COURSE:

The patient was admitted to the hospital under the interventional neuroradiology service, and vascular surgery and neurosurgery were consulted. The treatment team agreed that a surgical approach to the pseudoaneurysm would be a challenge because distal control of the high cervical internal carotid artery would be difficult. The cerebral arteriogram revealed no other abnormalities. The patient had good collaterals, with a moderately large right posterior communicating artery and a patent anterior communicating artery visualized.

The patient was taken to the angio suite and, under neuroleptic anesthesia, a 7-F sheath was placed in the right common carotid artery. Repeat cerebral arteriography was performed with Visipaque (iodixanol 270mgI\mL, Nycomed Amersham, Princeton, NJ). Because of the patient's FMD and the high location of the lesion, the team was reluctant to try to place a Wallstent. Consequently, a 4×15 mm Palmaz-Schatz Crown balloonexpandable stent on a 3.5-F microcatheter was advanced across the neck of the aneurysm and deployed (figures 2,3). A control angiogram demonstrated that the stent was in proper location; however, there was significant residual filling of the aneurysm. Consequently, a Prowler 10 microcatheter (Cordis Endovascular, Miami, FL) was advanced through the stent into the aneurysm. Four GDC coils were placed in the aneurysm (figure 4). A final control angiogram demonstrated a small amount of residual neck remnant. No further coils were placed because of a concern for the possibility of extrinsic compression of the stent from the coils.

The patient tolerated the procedure well, without neurologic compromise at the end of the procedure. She had an uneventful postoperative course, and was discharged two days post-procedure.

DISCUSSION:

Fibromuscular dysplasia is a vasculopathy of unknown etiology that affects the renal arteries, the internal carotid arteries, and the vertebral arteries. SUP>>1A characteristic "string of beads" appearance usually is seen in the mid-cervical internal carotid artery. The internal carotid artery is affected in approximately three-fourths of all cases; the vertebral artery is involved in 15 to 25%.

Dissection is a well known complication of FMD; pseudoaneurysm formation is an unusual secondary finding. Patients with FMD also are subjected to an increased risk of intracranial aneurysms. ¹ S imilar cases of internal carotid artery pseudoaneurysms treated with coils and stents have previously been reported. ^2-4 This case was somewhat unusual, as the aneurysm was able to be found and the patient had been asymptomatic at presentation. In this case, the use of a small, balloon-expandable stent catheter made for a very safe and low profile means of placing the stent.

This case demonstrates that new, low profile flexible stents can be quite useful in treating surgically difficult-to- access vessels. The combination of stents and coils can be quite effective, providing a low risk, non-invasive means of treating arterial dissections and pseudoaneurysms.

Prepared by John S. Sarzier, MD; Bruce Zweibel, MD; Avery J. Evans, MD, Radiology Associates of Tampa, Tampa, FL.