Differentiation between paraclinoid and cavernous sinus aneurysms with contrast-enhanced 3D constructive interference in steady- state MR imaging

BACKGROUND AND PURPOSE: Differentiation between paraclinoid and cavernous sinus aneurysms of the internal carotid artery (ICA) is critical when considering treatment options. The purpose of this study was to determine whether contrast-enhanced (CE) 3D constructive interference in steady state (CISS) MR imaging is useful to differentiate between paraclinoid and cavernous sinus aneurysms.MATERIALS AND METHODS: This study included 11 aneurysms in 10 consecutive female patients, ranging from 52 to 66 years of age. All aneurysms were adjacent to the anterior clinoid process. After conventional and CE 3D-CISS imaging on a 1.5T MR imaging unit, all patients underwent surgery, and the relationship between the aneurysms and the dura was confirmed. Two neuroradiologists evaluated the location of the aneurysms on CE 3D-CISS images and classified them as intradural, partially intradural, and extradural aneurysms. Operative findings were used as a reference standard. To understand the imaging characteristics, we assessed the boundary and signal intensity of the cavernous sinus, CSF, and carotid artery on the side contralateral to the lesion.RESULTS: Operative findings disclosed that 5 aneurysms were intradural and 6 were extradural. All except 2 were accurately assessed with CE 3D-CISS imaging. One intradural aneurysm adjacent to a large cavernous aneurysm and 1 cavernous giant aneurysm were assessed as partially intradural. On CE 3D-CISS images, the boundary between the CSF, cavernous sinus, and carotid artery was identified by high signal-intensity contrast in all cases.CONCLUSION: CE 3D-CISS MR imaging is useful for the differentiation between paraclinoid and cavernous sinus aneurysms.

Differentiation between paraclinoid and cavernous sinus aneurysms of the internal carotid artery (ICA) is critical when considering treatment options. Paraclinoid carotid aneurysms pose the risk for subarachnoid hemorrhage (SAH) and may be considered for treatment. On the other hand, cavernous sinus aneurysms pose little or no risk for hemorrhage and are usually followed in asymptomatic patients. For the appropriate management of patients with SAH and multiple intracranial aneurysms, it is important to determine whether the aneurysms are located in the intradural portion.Traditional anatomic landmarks on digital subtraction angiograms for discrimination between paraclinoid and cavernous sinus aneurysms are the origin of the ophthalmic artery¹ and the anterior clinoid process.² However, these landmarks are not always reliable for making the distinction.^3,4 Although some researchers reported the usefulness of CT angiography for this issue,^3,4 the landmarks are indirect signs, and the accurate site at which the ICA penetrates the dura mater is not clearly understood.3D constructive interference in steady state (3D-CISS) MR imaging can provide high-resolution images with good contrast between the CSF and solid structures; they facilitate evaluation of acoustic neurinomas, epidermoids, ventricular lesions, and syringomyelia.^5–10 Although 3D-CISS imaging is useful for demonstrating cranial nerves in the cistern, contrast-enhanced (CE) 3D-CISS imaging yields good visualization of cranial nerves in the cavernous sinuses.¹¹ CE 3D-CISS imaging may demonstrate the site at which the ICA penetrates the dura mater; however, to date, the usefulness of CE 3D-CISS imaging for distinguishing between paraclinoid and cavernous sinus aneurysms has not been assessed.The purpose of this study was to determine whether CE 3D-CISS MR imaging is useful for the differentiation between paraclinoid and cavernous sinus aneurysms.