REVIEW ARTICLE Imaging Lesions of the Cavernous Sinus A.A.K. Abdel Razek SUMMARY: Our aim was to review the imaging findings of relatively common lesions involving the M. Castillo cavernous sinus (CS), such as neoplastic, inflammatory, and vascular ones. The most common are neurogenic tumors and cavernoma. Tumors of the nasopharynx, skull base, and sphenoid sinus may extend to the CS as can perineural and hematogenous metastases. Inflammatory, infective, and granulomatous lesions show linear or nodular enhancement of the meninges of the CS but often have nonspecific MR imaging features. In many of these cases, involvement elsewhere suggests the diagnosis. MR imaging is sensitive for detecting vascular lesions such as carotid cavernous fistulas, aneurysms, and thromboses. he cavernous sinus (CS) contains vital neurovascular orbital fissure anteriorly to the Meckel cave and farther poste- Tstructures that may be affected by vascular, neoplastic, in- riorly to the dura and the pores that allow nerves to enter it. Its fective, and infiltrative lesions arising in the CS proper or via transverse diameter is 5–7 mm, its vertical diameter is 5–8 extension from adjacent intra- and extracranial regions. Pa- mm, and its anteroposterior diameter is 10–15 mm. The CS is tients with CS syndrome usually present with paresis of 1 or composed of a network of small venous channels that may more cranial nerves (IIIϪVI), which may be associated with arbitrarily be divided into different compartments. The main painful ophthalmoplegia. The clinician needs to know the type venous influx into the CS is the superior and inferior ophthal- of CS lesion, its relationship to crucial neurovascular struc- mic veins, pterygoid plexus, and Sylvian vein. The outflow of tures, and its extension into the surrounding tissues. These the CS occurs via the superior and inferior petrosal sinuses. findings are essential for deciding therapeutic modalities such The internal carotid artery (ICA) is the most medial structure as microsurgery, radiation therapy, or medical treatment as inside the CS and is contained in the so-called carotid trigone. well as for appropriate planning of surgery or radiation ther- Cranial nerves III and IV and the first and second divisions of apy.1-8 Because the MR imaging features of many of these le- the cranial nerve V (from superior to inferior) are located in sions overlap and are often nonspecific, we will emphasize the lateral dural wall of the CS (called the oculomotor trigone). those features that allow one to formulate a reasonable differ- Cranial nerve V courses in the central part of the CS inferolat- ential diagnosis. eral to the ICA. Inside, the CS is a multiseptate space, which shows intense contrast enhancement of the slower flowing ve- Imaging Protocol and Anatomy nous blood. The ICA appears as a signal-intensity void struc- MR imaging of the CS should include routine T2, fluid-atten- ture.3-7 Occasionally, the CS may contain fatty deposits that uated inversion recovery (FLAIR), and precontrast T1- are normal (Fig 1). These fatty zones may be more prominent weighted images of the entire brain. Postcontrast T1-weighted in obese patients or those with Cushing syndrome or receiving Յ3-mm-thick images should be obtained in the axial and exogenous steroid therapy. coronal planes with at least 1 plane imaged with a fat-satura- tion technique. Thin-section postcontrast axial images may be Neoplastic Lesions acquired by 3D spoiled gradient techniques. We generally im- age from the orbital apex through the prepontine cistern. Schwannoma Thin-section 3D heavily T2-weighted images (such as con- A trigeminal nerve schwannoma commonly involves the CS structive interference in steady state or fast imaging employing and, in 50% of instances, has a typical dumbbell-shape with steady-state acquisition) may allow visualization of individual bulky tumor in the Meckel cave and the prepontine cistern cranial nerves in the CS and adjacent cisterns. CT is best per- with a waist at the porous trigeminus. Conversely, it may be formed by using a multidetector scanner after intravenous ad- found only involving the Meckel cave (Fig 2). It may be solid ministration of iodinated contrast medium. Acquisitions in or have variable cystic or hemorrhagic components with oc- axial or coronal planes by using Ͻ1-mm-thick sections may be casional fluid levels. Small tumors tend to be homogeneous, obtained and then reformatted in other planes.2-7 whereas large ones are frequently heterogeneous in appear- The CS is composed of 2 layers of dura that split to form a ance. Schwannomas are isointense-to-hypointense masses on septate venous channel. Each dural wall contains an outer T1 images, mostly T2 hyperintense, and show contrast en- layer apposed to bone and an inner layer in contact with blood hancement. A clue to the diagnosis is that they follow the ex- or CSF. The CS extends from the orbital apex and superior pected course of the nerves from which they arise. Schwanno- mas may arise from other cranial nerves in the CS, particularly Received August 14, 2008; accepted after revision October 2. cranial nerve III. Multiple CS schwannomas and bilateral From the Department of Diagnostic Radiology (A.A.K.A.R.), Masnoura Faculty of Medicine, acoustic ones are seen in patients with neurofibromatosis type Mansoura, Egypt; and Department of Radiology (M.C.), University of North Carolina, Chapel 2.9-13 Hill, NC. Please address correspondence to Ahmed Abdel Khalek Abdel Razek, MD, Diagnostic Plexiform Neurofibroma Radiology Department, 62 El Nokri St, Meet Hadr, Mansoura Faculty of Medicine, Mansoura, Egypt; e-mail: [email protected] Plexiform neurofibromas most commonly involve the trigem- Indicates open access to non-subscribers at www.ajnr.org inal nerve, especially its first and second branches. A sugges- tive imaging feature is a tortuous or fusiform enlargement of DOI 10.3174/ajnr.A1398 the nerves that exhibit heterogeneous signal intensity. Unlike 444 Abdel Razek ͉ AJNR 30 ͉ Mar 2009 ͉ www.ajnr.org Fig 1. Normal fat deposits. Axial noncontrast CT scan shows normal and incidentally found deposits of fat (arrowheads) in the posterior CSs. These deposits may be seen in obese individuals, those taking corticosteroids, or those with Cushing syndrome. In the absence Fig 3. Malignant peripheral nerve sheath tumor. Coronal postcontrast T1-weighted image of these conditions, they have no significance. shows a large aggressive-appearing mass that involves the left CS, surrounds the ICA (arrow), erodes the middle cranial fossa floor, and extends into the infratemporal region. primary CS tumors along with schwannoma and meningi- oma. This tumor is formed by sinusoidal spaces with endothe- lial lining that contain slow-flowing or stagnant blood. A pre- operative diagnosis is important because of its propensity to bleed at the time of resection. These tumors are nearly hyper- REVIEW ARTICLE intense on T1- and T2-weighted images and are attached to the outer wall of the CS, and their diagnosis may be suggested when they show progressive “filling in” after contrast admin- istration. Other times, they show nonspecific intense homo- geneous or heterogeneous contrast enhancement (Fig 4).16-19 Meningioma Most CS meningiomas arise from the lateral dural wall, but sometimes they may be exclusively inside the CS. A meningi- oma is usually hypo- to isointense with respect to gray matter in all MR imaging sequences and enhances intensely (Fig 5A). A dural tail frequently can be seen extending away from the Fig 2. Schwannoma. Axial postcontrast T1-weighted image shows a well-defined enhanc- edge of the tumor and often into the ipsilateral tentorium. ing mass (arrow) involving the Meckel cave on the right. Although the findings are Meningiomas constrict the lumen of the ICA. Meningiomas nonspecific, the most common mass in this location is a schwannoma. may extend inside the CS and the Meckel cave and via the schwannomas, neurofibromas are less likely to extend to the porous trigeminus into the prepontine cistern. They may have Meckel cave. They are seen in 30% of patients with neurofi- an appearance very similar to schwannomas (Fig 5B).20-22 bromatosis type 1 but are extremely rare outside this disease.9,14 Pituitary Adenoma Pituitary adenomas may grow laterally and invade the CS. A Malignant Peripheral Nerve Sheath Tumor sign of CS invasion is encasement of the intracavernous ICA Malignant peripheral nerve sheath tumor is a high-grade sar- by Ͼ30% of its diameter or tumor extension lateral to the top coma that may infiltrate the CS. Large tumor size (Ͼ5 cm), (12 o’clock) of the ICA. Interposition of abnormal soft tissue ill-defined infiltrative margins, rapid growth, tumor signal- between the lateral wall of the CS and the ICA is a reliable intensity heterogeneity, and erosion of the skull base foramina indicator of CS invasion. Unlike meningiomas, pituitary ade- out of proportion to tumor size suggest its underlying malig- nomas generally do not narrow the ICA.23 nant nature (Fig 3).9,15 Its imaging findings are nonspecific, and the diagnosis is made by histology. Melanocytoma Primary melanocytomas originate from the leptomeninges of Cavernous Hemangioma the CS. The lesion is hyperintense with fine punctate areas of CS hemangioma is more commonly seen during the fifth de- decreased signal intensity on T1-weighted images and of low cade of life in female patients. It is among the most common signal intensity on T2-weighted images and shows no contrast AJNR Am J Neuroradiol 30:444–52 ͉ Mar 2009 ͉ www.ajnr.org 445 Fig 4. Cavernous hemangiomas. A, Axial postcontrast T1- weighted image shows a large and homogeneously enhanc- ing mass arising from the lateral wall of the left CS. B, Axial postcontrast T1-weighted image in a different cavernoma, which shows inhomogeneous contrast enhancement but also arises from the lateral wall of the CS, pushing the ICA (arrow) medially.