Computed tomography of cavernous sinus disease

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大짧放 9‘t 線醫웰會품‘ 第 24卷第2 號 pp. 201 - 212, 1988 Journal 01 Korean Radiological Society, 24(2) 201-212, 1988

Computed Tomography of Cavernous Sinus Diseases

Jin Wook Chung, M.D., Kee Hyun Chang, M.D., Moon Hee Han, M.D., 80 Hyun Kim, M.D., Chi Sung Song, M.D., Hyo Keun lim, M.D., Jong Chul Kim, M.D. *

Department of Radiology, College of Medicine, 5eoul National Univerisity

〈국문초록〉

해면정맥동 질환에서의 전산화단층촬영술

서울대 학교 의 파대 학 방사선과학교실

정 진 욱 • 장 기 현 • 한 문 희 • 김 보 현 • 송 치 성 • 임 효 근 • 김 종 칠.

저자들은 강밸진안에 도움이 되는 CT소견을 찾기 위해서 최근 5 년간 경험한 21 례의 해연정액동 영변 을 역행석무로 분석하였다. 21례를 원인별로 분류하연 패혈성 혈전증 5 례， 경동액-해연정액동류 5 례， 양성종양 5례， 악성전이암 6 례였마. CT 소견은 해연정액동의 모양， 조영증강양상， 양측성여부， 주위골 변화， 안와변화 및 두개강내 이상소견의 동반여부에 중점을 두어 분석하였마.

패혈성 해연정액옹 헐천증 5례중 4례에서 조영증강을 보이는 해연정액동 내부에 다수의 불규칙한 음 영결손。 1 일측성 또는 양측성으로 판찰되었고， 안와를 판찰할 수 있었띤 3 례중 2 례에서 안와의 영증성 변화가 동반되었마. 정동액 -해연정액동류 5 례중 4례에서는 한측 해연정액동의 미만성 팽창파 아울러 강한 균질성 조영증강을 보였고 쿠불구불하게 확장된 상안정액 (superior ophthalmic vein) 을 관찰할 수 있었￡며 특정석으로 2 례에서는 3차 신경절 등의 정상음영이 소질되어 있었마. 양성종양 5 례중 4 례에서 는 해 연정액동에 국한펀 구행종괴로 경계 가 뚜렷하고 주위골변화가 없거 냐 골칭식 (bone erosion) 또는 골갱화 (bone sclerosis) 를 보이는 것이 특정석이었고， 악성전이성 종양에서는 6 례중 5례에서 골파괴 또 는 뱅밴의 두개낭내 미만성 파급 둥 뱅변의 악성성향을 시사하는 소견을 말견힐 수 있었다. 결론적우로 모든 례에서 득이한 조직학적 진단을 L~ 릴 수는 없지만 소수의 예외를 제외하고는 CT 소견만으혹 21 례 의 해연정액동 명변을 영증성질환， 헬판성질환， 양성종양 빛 악성건이성종양으로 구분지을 수 있었다.

횡단스캔은 판상스캔에 비해 해연정액동 뱅소와 전후좌우 안정쿠조물과의 판계를 밝히고 안와연화 및 연판된 두개강내 명변을 찾는데 우월하였마. 직접 판상스캔은해연정액동내부의 신경헐판구조물의 평 가， 양쪽 해연정액동의 비교판찰， 뇌히수체와의 판계 빛 투개기저의 골변화를 판찰하는데 횡단스캔보 다 우월하였다. 따라서， 임상적으로 해연정액동의 명밴이 의심될때 횡안 및 직접판상 선산화단층촬영 을 모두 시챙하는 것이 바람직하다고 생각된다

Summary. We retrospectively analyzed CT scans 01 21 cavernous sinus lesions in an attempt to lind the CT lindings helplul to the differential diagnosis. With the integration 01 various CT lindings it was possible to categorize the lesions into inllammatory, vascular, benign neoplastic and malignant metastatic lesions with lew exceptions. Four 01 5 cases 01 septic cavernous sinus thrombophlebitis revealed unilateral or bilateral multiple irregular lilling delects in the enhancing cavernous sinus with or without orbital inllammatory change

• 경 상대 학교 의 파대 학 방사선파학교실

• Department of Radiologκ College of Medicine, Kyung 5ang National University 이 논운은 1988 년 1월 22 일에 접수하여 1988년 2월 24 일에 채택되었음.

Received January 29, 1988, Accepted March 16, 1988

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-大韓放射線醫學會誌: 第24 卷第 2 號 1988-

Four of 5 cases of carotid-cavernous fistula demonstrated unilateral or bilateral diffuse bulging and homogeneous enhancement of cavernous sinus with obliteration of normallow densities of cranial verves and gasserian ganglion.

미 latation and tortuosity of superior ophthalmic vein were also associated. Four of 5 cases of benign neoplastic lesion showed well-circumscribed enhancing mass confined to cavernous sinus with pressure erosion or hyperostosis of adjacent bone. Five of 6 cases of malignant metastatic lesion showed various findings suggesting malignant nature such as destruction of adjacent bone or associated manifestation of intracranial spread‘

As compared with axial scan, coronal scan proved to be more sensitive in detection of subtle cavernous sinus expansion, and superior in evaluation of intracavernous neural structures, relationships with pituitary gland and osseous change of skull base. Axial scan, however, was superior in detection of associated orbital and intracranial abnormalities. Scans in both projections are needed in the evaluation of most cavernous sinus diseases

KEY WORDS; Cavernous sinus-computed tDmography

Introduction

Ophthalmplegia, complete or incomplete, usually painful and commonly associated with sensory deficits in the first or second division of the trigeminal nerve, alerts the clinician to the presence of a pathologic process in the cavernous sinus¹). The added finding of visual loss further localizes the lesion to the anterior cavernous sinus and orbital apex. Despite the anatomical specificity provided by the clinical findings

,

it is often difficult to diffe- rentiate local masses from non-mass lesions. This dilemma is attributable to the wide variety of diseases that affect this region and to their frequently overlapping clinical presentations²). That is, accurate etiologic diagnosis of the parasellar lesion is not made on clinical grounds but is contingent upon supplementary examinations, such as appro- priate blood tests, inspection of the nasopharynx, and radiographic studies.

In the past, radiographic examination has been limited; skull films or conventional tomography have demonstrated only osseous change and sphenoid sinus abnormality and angiography has delin- eated only the vascular components. However, with the introduction of high resolution(HR)CT, direct visualization of the neurovascular structures

within the cavernous sinus and accurate definition of its dural boundaries have been possible 3,4,5)

Now

,

CT findings of several cavernous sinus diseases have been reported and specific diagnosis of them has been possible on occasion^Z-13

).

Changes in size, density, and configuration of the cavernous sinus are useful findings in detecting abnormality by CT. Among these, contour bulging of lateral boundary is the most sensitive indicator of pathologic involvemene,4l. The purpose of this paper is to describe CT findings of various diseases causing cavernous sinus bulging and to eluci- date differential points in CT diagnosis

Materials and Methods

A retrospective review of all CT studies at the Seoul National University Hospital from January 1983 to December 1987 uncovered 21 cavernous sinus Iesions. These included 5 cases of septic cavernous sinus thrombophlebitis, 5 carotid-cavernous fistulas, 5 benign neoplasms, and 6 malignant metastatic neoplasms(Table 1). Ten patients were male and eleven were female. Age ranged from 6 to 72 years. We excluded trigeminal neuroma with severe extension into middle and posterior cranial fossas

,

and lesions which arised from adjacent organ and secondarily invaded cavernous

SH뼈

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} 5 ^특^gr^nrζ그@-m〔 ∞- 〔。_g건드@(} ^、[。g 。m^【^∞〔^〕r_〕、。{ηα_{〈엌그(〕ζα}mgzω [〕}@@∞ω@@^|

Exophthalmos, prominent Abnormal thick ophthalmic vein enhancement of ipsilateral tentonum (-)

Associated Intracranial Abnormality Cerebellar abscess (-)

(-) (-) (-) (-)

(-) (-) (-) Exophthalmos, prominent ophthalmic vein

Exophthalmos, prominent ophthalmic vein Exophthalmos, prominent ophthalmic vein Prominent ophthalmic vein, bulbar wall thickening, EOM thickening, periorbital swelling Bulbar wall thickening, periorbital swelling

Orbital Change (-) (-) (-)

No scan

No scan Erosion of lateral wall of sphenoid sinus, and petrous apex

Bone Change (-) (-) (-) (-) (-) (-) (-) (-) (-) (-)

Enhancement Pattern Bilaterality Unilateral

Unilateral Unilateral

Unilateral Unilateral Unilateral

Unilateral Bilateral

Bilateral Bilateral Bilateral

CT Findings of Cavernous Sinus Homogeneous and isodense

Homogeneous and mtense Homogeneous and mtense Homogeneous and mtense Homogeneous and mtense

Homogeneous and mtense Multiple irregular filling defects Multiple irregular filling defects

Multiple irregular filling defects Multiple irregular filling defects Single large filling defect Diffuse widening with slightly convex border Round mass with Round mass with smooth convex convex border border

Diffuse widening with straight border Diffuse widening with straight border Diffuse widening with straight border Diffuse widening with slightly concave border Diffuse widening with slightly convex border Diffuse widening with straight border Diffuse widening with straight border Diffuse widening with slightly convex border Diffuse widening with straight border

Coronal Contour Axial Contour Septic cavernous sinus thrombo phlebitis Septic cavernous sinus thrombophlebitis 34/ M Septic cavernous sinus thromb。 phlebitis Septic cavernous sinus thrombophlebitis Carotid-cavernous Smooth lateral fistula convex bulging

Smooth lateral convex bulging Smooth lateral convex bulging Smooth lateral convex bulging Carotid-cavernous Smooth lateral fistula convex bulging Carotid-cavernous Smooth lateral fistula convex bulging

Smooth lateral convex bulging Carotid-cavernous No scan fistula

No scan Cerotid-cavernous No scan fistula

Summary of the 21 Cases Benign neoplasm Trigeminal neunnoma

Septic cavernous sinus thrombophlebitis

Age & Diagnosis Gender 46/M 55/F 58/F 54/F 56/F 53/F 72/F 60/F 46/F 6/F

Table 1. Case N。 10 ⁵ 6 8 9 2 3 4 7 11

t'V ζ〉 μJ

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Associated Intracranial Abnormality

CT Findings of Cavernous Sinus Age & Diagnosis Gender

Orbital Change Bone Change Case No Enhancement Pattern Bilaterality Coronal Contour Axial Contour (-) ]/

(-) (-)

lu가짧냥옆앓빼빼깨뼈뼈빼애야” W생NA뺑

(-) (-) (-)

니

^/

(-) No scan

Erosion of posterior clinoid, lateral wall of sphenoid sinus H yperostosis of posterior clinoid, lateral wall of sphenoid sinus Destruction of orbital apex, posterior ethmoid (-)

(-) Unilateral Unilateral

Ring enhancement Homogeneous and isodense

Round mass with convex border Round mass with Round mass with smooth convex convex border border

No scan Benign neoplasm Trigeminal neunnoma Benign neoplasm Cavernous hemangioma

191M 421F

12 13 Unilateral Homogeneous and isodense with central low density

Round mass with Diffuse widening smooth convex with straight border border

Benign neoplasm Meningioma 45/F 14 Unilateral Unilateral Subdural spread No scan (-) Unilateral Homogeneous and isodense

@얘 ^N 뽕

Another suprasellar mass

(-) (-) Unilateral Homogeneous and isodense } 잉∞∞ j (-) No scan

」^l

(-) Direct invasion into temporal lobe, meningeal spread

Homogeneous and isodense Homogenous and isodense (-)

Destruction of dorsum sellae, lateral wall of sphenoid sinus Destruction of orbital apex, posterior ethmoid (-)

Unilateral Homogeneous and isodense

Diffuse widening with straight border Round mass with smooth convex border Round mass with Diffuse widening smooth convex with slightly border convex border Round mass with No sc뻐 smooth convex border Smooth lateral convex bulging

No scan No scan

Benign neoplasm Eosinophilic granuloma Metastatic ca From salivary gland Metastatic ca Lymphoma

6/M 301M

15 16

l N()A | 121M 17 Diffuse widening with straight border

Metastatic ca Germ cell tumor Metastatic ca From para nasal sinus

151M 18 281M 19 Unilateral Inhomogeneous Unilateral Homogeneous and isodense

Diffuse widening with straight border Irregular mass with fuzzy border

Smooth lateral convex bulging

Metastatic ca Lung cancer 54/M 20 Irregular mass with fuzzy border Metastatic ca From nasopharynx

391M 21

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- Jin Wook Chung, et a^l.:Computed Tomography 01 Cavernous Sinus Diseases

gioma of sphenoid wing and petrous apex, metastasis to skull base, chordoma, chondroosseous tumor of skull base, etc).

Their diagnosis was confirmed by biopsy in tumors, by angiography in vascular lesions, and by clinical manifestation in septic cavernous sinus thrombophlebitis. Biopsy was not performed in cases of metastatic disease with known primary slte.

AIl patients were scanned on GE CT /T 8800 and / or 9800 scanners with variable thickness from 1.5mm to 5mm. Sixteen patients were scanned in both axial and coronal planes, four in axial plane only

,

and one in coronal plane only. In the major- ity of cases, only contrast enhanced scans were obtained after bolus injection of 60ml of Telebrix 30(iodine content 18gm) followed by drip infusion of 100ml of Telebrix 38(iodine content 38gm).

The CT scans were retrospectively analyzed in viewpoint of pattern of enhancement, bilaterality, configuration of boundary of cavernous sinus

,

adjacent bone change

,

orbital change

,

and associated intracranial abnormality. In 16 cases, it was possible to evaluate orbit.

Result

The CT findings of all 21 cases were summari- zed in Table 1.

1. Septic cavernous sinus thrombophlebitis(5 cases)

In all cases, direct visualization of septic thrombi was possible; four cases showed multiple irregular filling defects(Fig. 1) and one case showed single large filling defect(Fig. 2) in the enhancing cavernous sinus. They ranged roughly from 3mm to lOmm in size. Lateral boundary of the sinus was sharp, smooth and showed diffuse bulging in all cases. Three cases showed bilaterality. The other two case were left-sided. Orbital changes were associated in two out of three cases in which orbital scans were performed. Orbital abnor-

Fig. 1. (Case 1) -Bilateral septic cavernous sinus thrombophlebitis with multiple defects A. Coronal enhanced scan shows lateral bulging

of both cavernous sinuses and irregular enhancement with irregular delects. Lateral wall of cavernous sinus, intracavernous internal caro.

tid artery and pituitary gland enhance more intensely than the rest 01 the cavernous sinus B. Axial enhanced scan shows widening of both

cavernous sinuses, irregular filling defects,

and linear enhancement of lateral wall of the sinus. Note that lateral borders of both cavernous sin uses appear straight, but not convex Subdural extension along greater wing of spe noid and dilated superior ophthalmic vein in right orbit are also demonstrated

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A

B

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-大韓放射線醫學會註、. 第24 卷第 2 號 1988-

malities included tortuous dilated superior ophthalmic vein, thickening of extraocular muscle, bulbar thickening with fuzzy border, periorbital swelling, and increased soft tissue strands at retro- bulbar fat. There was apparent discrepancy in degree of bulging between coronal and axial scan.

On . coronal scan convex bulging of lateral boundary was evident

,

but on axial scan it was rather straight in all cases. Instead, there was diffuse widening of the involved cavernous sinus on axial scan. In three cases of extensive cavernous sinus thrombosis, intracavernous carotid artery and pituitary gland showing norrnal enhancernent were readily identified within thrombosed cavernous sinus by density difference(Fig. 1-a). Cerebellar abscess was associated in a case with rnycotic aneurysrn of intracavernous carotid artery. No adjacent bony abnorrnality was found.

2. Carotid-cavernous fistula(including direct internal carotid-cavernous fistula and dural AVM of cavernous sinus; 5 cases).

All cases showed hornogeneously intense εnhan

cernent of bulging cavernous sinus with non-visualization or smaller size of normal low densities of intracavernous cranial nerves and gasserian ganglion. One case was bilateral(Fig. 3) and four cases were unilateral(Fig. 4). The lateral wall of involved cavernous sinus was sharp andsrnooth in all cases. There was discrepancy in appearance of the sinus bulging between coronal and axial scan.

On coronal scan lateral boundary showed convex lateral bulging, but on axial scan it appared widen ed but remained rather straight or slightly convex in lateral border. Degree of bulging seems to be related with amount of shunting. In two cases of large carotid-cavernous fistula, ipsilateral gasserian ganglion was obliterated(Fig. 4). In four cases, orbital changes including proptosis, enlar gernent of ophthalrnic vein and thickening of ex traocular muscle were associated(Fig. 4). The case without orbital change had small dural A VM on angiography. Abnormal thick enhancement of ipsi-

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’

^{Fig. 2.} ^(Casethrombophlebitis ⁵⁾^-Unil^ateralwith ^septicsingle defect ^cavern^* ^‘-^。따

^’·

^sinu^s^B A. Coronal enhanced scan shows unilateral con

vex bulging of left cavernous sinus with large single filling defect. Low density of oculo.

motor nerve within left cavemous sinus is also obliterated

B. Axial scan shows unilateral widening of left cavernous sinus with slightly concave lateral border. The filling defect in left cavernous sinus appears not well defined and not separa ble from normal area probably due to partial volume averaging

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A

- Jin Wook Chung, et al.: Computed Tomography of Cavernous Sinus Diseases-

Fig. 3. (Case 6) -Bilateral carotid-cavernous fistula A. Coronal enhanced scan shows convex lateral

bulging and homogeneous enhancement 01 both cavernous sinuses

B. Axial enhånced scan shows bilateral expansion 01 cavernous sinus with mild convexity

。1 lateral border and intense homogeneous en hancement. Note that the low density area 01 gasserian ganglion is obliterated

lateral tentorium was assoicated in one case of dural A VM. No adjacent bony abnormality was found.

3. Benign neoplastic lesion(5 cases)

Five cases of benign neoplastic lesion inc\uded

two trigeminal neurinomas, a meningioma, a eosinophilic granuloma, and a cavernous hemangioma.

All cases were unilateral and their lateral border was sharp and smooth. Except a ring-enhancing trigeminal neurinoma(Fig. 5), all other four tumors showed homogeneous isodense enhancement compared with the density of pituitary gland or contralateral cavernous sinus. The mases appeared not separable from normal portion of the sinus and obliterated normal intracavernous neural structures. Three cases(two trigeminal neurinomas and a cavernous hemangioma) showed round mass expanding cavernous sinus with smooth convex border on both axial and coronal scans. In a meningioma and a eosinophilic granuloma, the involved sinus showed diffuse widening and straight lateral border on axial scan but round mass-like appearance with convex border on coronal scan(Fig. 6). In four cases, abnormality of adjacent bone was observed; pressure erosion at lateral wall of sphenoid sinus and petrous apex in

Fig. 4. (Case 7)-Unilateral carotid-cavernous fistula Axial enhanced scan shows unilateral widening 01 right cavernous sinus with intense enhancement. The low density 01 right gasserian ganglion is obliterated. Ipsilateral exophthalmos and thickening 01 extraocular muscle are als。

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-大轉放射線홉學會誌 : 第 24 卷第 2 號 1988-

Fig. 5. (Cases 12)-Trigeminal neurinoma

Axial enhanced scan shows round mass with ring-enhancement at right Meckel’s cave area

a trigeminal neurinoma, pressure erosion at posterior c1inoid process and lateral wall of sphenoid sinus in a cavernous hemangioma, hyperostosis at posterior c1inoid process, and lateral wall of sphenoid sinus in a meningioma(Fig. 6), irregular focal destruction of sphenoid bone at orbital apex and planum sphenoidale, and posterior ethmoid air cells in a eosinophilic granuloma. There was no orbital change.

4. Malignant metastatic Iesion(6 cases)

Primary sites of six metastatic lesions were as follows; a nasopharyngeal cancer, two adenoid cystic carcinomas of paranasal sinus and salivary gland, a lung cancer, a Iymphoma, and a ectopic germinoma. AIl cases revealed unilateral bulging of the cavernous sinus. Four cases were left-sided and two cases were right-sided. Pattern of enhancement was homogeneously isodense in four cases(two adenoid cystic carcinomas of salvary gland and paranasal sinus, a ectopic germinoma, a nasopharyngeal cancer), homogeneously hypodense in a lymphoma(Fig. 7) and slightly inhomogeneous in a metastatic lung cancer. Later-

al wall was fuzzy and indistinct only in the metastatic Iesion of nasopharyngeal cancer. The other five cases showed sharp and smooth lateral margin. Metastatic lesion without bone destruction showed round mass expanding cavernous sinus on both axial(Fig. 8) and coronal scans. Metastatic

Fig. 6. (Case 14)-Meningioma

Coronal(A) and axial(B) enhanced scans show convex lateral bulging and diffuse widening of left cavernous sinus, respectively. There is hyperostosis at greater wing of sphenoid bone,

posterior clinoid process and lateral wall of sphenoid sinus

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A

B

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Jin Wook Chung, et al.: Computed Tomography of Cavernous Sinus Diseases-

Fig. 7. (Case 17)-Malignant Iymphoma

Coronal enhanced scan shows expansion of right cavernous Slnus with homogeneously hypodense enhancement relative to the lateral dural wall and internal carotid artery

Fig. 8. (Case 16)-Metastatic lesion from adenoid cystic carcinoma of salivary gland. Axial enhanced scan . demonstrates homogeneously enhancing round mass without definite bone change

Fig. 9. (Case 20)-Metastatic lesion from lung cancer Axial enhanced scan shows hypodensely enhancing mass in widened left cavernous sinus, orbital apex and posterior ethmoid air cells with adjacent bony destruction. Lateral border is slightly concave in spite of extensive involvement

lesions with bone destruction(a adnoid cystic carcinoma of paranasal sinus, ^alung cancer) showed diffuse widening of the involved cavernous sinus and rather straight lateral margin on axial scan- (Fig. 9) in contrast to convex bulging on coronal scan. Focal bone destruction was found at dorsum sellae and lateral wall of sphenoid sinus in a metastatic adenoid cystic carcinoma of paranasal sinus, and at orbital apex, sphenoid sinus and posterior ethmoid air cells in a metastatic lung cancer.

Various intracranial abnormalities were associated;

direct parenchymal invasion into temporal lobe in a nasopharyngeal cancer, sheet-like meningeal enhancement suggesting meningeal spread in a lymphoma and a nasopharyngeal cancer, and a sepa- rate suprasellar mass with no apparent connεctiO n

to the sinus lesion in a ectopic germinoma.

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-大韓放射線뿔學會誌 ; 第24 卷第 2 號’ 1988-

Discussion

The cavernous sinus is one of the dural venous sinuses located between the meningeal and perio- steal layers of the dura and contains trabeculated network of venous channels, intracavernous portion of internal carotid artery, and cranial nerve- s(oculomotor nerve, trochlear nerve, abducens nerve, ophthalmic division of trigeminal nerve and gasserian ganglion)3,14l. Consequently

,

diseases of the cavernous sinus can be classified into inflamm- atory(e.g., cavernous sinus thrombophlebitis), vascular(e.g., fistula, aneurysm), and neoplastic lesion(e.g., neurinoma, meningioma, metastatic tumor). No matter what the cause is, it leads to volume expansion of the involved cavernous sinus

,

demonstrating bulging of lateral boundary of the cavernous sinus on CT. If the disease process is unilateral, lesion of the cavernous sinus is easily detected by asymmetricity. Both cavernous sinuses are connected by intercommunicating venous channels, which provide the route of disease spread into contralateral side and explain bilaterality of some cavernous sinus lesions.

For evaluation of cavernous sinus by CT it is essential to perform intravenous contrast enhancement. Amount of contrast media should be large enough to enhance the cavernous sinus and pituitary gland adequately. Contrast enhancement highlights cavernous sinus and its dural boundary in degree similar to internal carotid artery and pituitary gland, but not the Meckel’s cave and intracavernous cranial nerves. Intracavernous intracranial nerves are seen as low attenuation areas at specific location of cavernous sinus along its anatomical course3). Among these, κ1eckel’s cave and oculomotor nerve are consistently visible and usually symmetric. They can be obliterated by any kind of disease that involves cavernous sinus. Non- visualization of normal low density of Meckel’s cave within homogeneously enhancing cavernous

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sinus seems to be one of the important CT findings suggesting carotid-<.:avernous fistula, because it may manifest as subtle expansion of cavernous sinus as those of our cases 9 and 10.

If not dynamic scan, prominent linear enhancement of dural lateral border or identification of intracavernous carotid artery or pituitary gland by density difference suggests abnormal enhancement of entire cavernous sinus and can be a sign helpful to the detection of cavenrous sinus disease. 1n our series

,

3 cases of septic thrombophlebitis and one case of lymphoma show this CT finding(Fig. 1-a, Fig. 7).

Besides the contrast enhancement, the other technical factors of CT scan such as section thickness and planes are crucial for the detection of small lesion of cavernous sinus. The section thickness is advised to be 1.5-3.0mm for avoiding partial volume effects, even though the lesions were seen with 5mm thickness in our some cases. Which projection of scanning is superior, coronal or axial? Coronal scan is more sensitive in detection of subtle cavernous sinus expansion, easier to compare both cavernous sinuses, and superior in evaluation of intracavernous neural or vascular structures

,

relationship with pituitary gland and osseous change of skull base. Axial scan is superi- or in display ofaxial relationship with adjacent structures and in detection of orbital change or intracranial abnormality. Scans in both projections are needed for complete evaluation of cavernous sinus disease. 1n our series, a thrombus was more clearly visible on coronal scan(Fig. 2), while meningeal spread was seen only on axial scan in Iymphoma patient. All of the cavernous sinus le sions showed convex bulging of lateral border on coronal scan only with difference in degree, but configuration of cavernous sinus on aixal scan is greatly different between different etiologies, which is thought to be helpful in differential di- anosis. Neoplastic lesions without bone destruction or meningeal spread usually showed round mass

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- Jin Wook Chung, et al.: Computed Tomography of Cavernous Sinus Diseases-

expanding cavernous sinus on both axial and coronal scans, which might be due to confinement of the mass within the dural boundary of the sinus. But, destruction of adjacent bone or meningeal spread in neoplastic lesion caused disruption of dural confinement of the neoplasm, leading to loss of round convexity of lateral border. 1n in- flammatory or vascular lesion of cavernous sinus, involved sinus was diffusely expanded and its lateral boundary remained to be rather straight on axial scan.

There are many causes that show filling defects within enhancing cavernous sinus. Partial or complete thrombosis of cavernous sinus

,

neurinomas of intracranial nerves, intracavernous metastasis, and spontaneous aseptic thrombosis of the cavernous sinus in a preexisting carotid-cavernous fistula may all demonstrate abnormal low attenuation values within the enhancing cavernous sinus⁸)

But

,

in our series m비 tiple irregular filling def，εcts

within the enhancing cavernous sinus were found solely in septic cavernous sinus thrombosis and seems to be specific finding. The filling defects due to septic thrombi are irregular and do not correspond to the anatomic course of neural structures. Additionally, air in the cavernous sinus can be a sign of septic cavernous sinus thrombosis⁹)

,

but not seen in our cases. Fatty tissue also appears as low attenuation value within the cavernous sinus in normal person or in association with Cushing disease⁸). Neoplasms with inhomogeneous or little enhancement should be differentiated from inflammation. But, it is not difficult to diffe- rentiate them because neoplastic lesion usually shows focal bulging, unilateral involvement and bony change.

Bilateral involvement is usually demonstrated in cavernous sinus thrombophlebitis or carotid-cavernous fistula as those in our series. Bilateral cavernous sinus involvement may also be seen in bilateral neurogenic tumors such as trigeminal neurinoma in neurofibromatosis and bilateral metastatic

lesions²). But, they are very rare diseases. Abnormality of adjacent bone was also very helpful in differential diagnosis. Bone destruction and pressure erosion usually indicate malignant and benign neoplastic nature of the lesion, respectively. But

,

there are exceptions. Benign neo-

이asm such as eosinophilic granuloma may show gross bopy destruction as shown in our case 15.

Also, the carotid-cavernous fistula can cause en- largement of superior orbital fissure by pressure erosion. Hyperostosis adjacent to the bulging cavernous sinus is characteristic of meningioma 13)

Orbital changes are usually associated with only cavernous sinus thrombosis and carotid-cavernous fistula, but not with the neoplasm. Dilatation and tortuosity of superior ophthalmic vein is the hall- mark of the carotid

•

avernous fistula, even though it may be associated with other conditions such as orbital venous malformation and varices, and vascular tumor⁷). Other orbital abnormalities such as thickening of extraocular muscle

,

bulbar wall thickening with fuzzy border, periorbital swelling, and increased soft tissue strands at retro- bulbar fat are nonspecific and may be found in Grave’s ophthalmopathy, orbital cellulitis, acute orbital pseudotumor, etc. These lesions, however, usually demonstractes normal cavernous sinus. No neoplastic lesion of our cases was associated with orbital change.

Associated intracranial abnormality can also assist to make a correct differential diagnosis and lead to specific diagnosis on occasion, as those of our cases 4,9,17,18 and 21. Cavernous sinus involvement in ectopic germinoma( case 18) might be caused by cisternal drop metastasis at subarach- noid -space around gasserian ganglion

Most difficult situation to judge the nature of the lesion is benign-Iooking tumorous lesion which is demonstrated as well circumscribed mass with uniform enhancement on CT. Magnetic resonance imagíng may be greatly useful in the differential diagnosis of these patients, even thgough there are - 211-

(12)

-大韓放射線훌훌學會註 : 第24 卷第 2 號 1988-

only a few descriptions in the literature to date. Angiography is essential for the verification of the carotid-cavernous fistula and intracavernous aneurysm and is usually hεlpful to the diagnosis of meningioma or cavernous hemangioma. With no aid of angiography, there are still diverse possi- bilities including trigeminal neurinoma, meningioma without hypervascularity, chronic granulo- matous lesion \0), and metastasis. However, com- bined analysis of all the radiologic examinations in association with clinical and neurologic symptoms lead to correct preoperative diagnosis in most of the patients.

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