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Case report: Septic thrombosis of the cavernous sinus: Diagnosis with the aid of computed tomography
Clinical Radiology (1989), 40, 520-522
Case Report: Septic Thrombosis of the Cavernous Sinus" Diagnosis with the Aid of Computed Tomography R. BEN-URI,
L. P A L M A and Z. K A V E H
Department o f Radiology, Central Emek Hospital, Afula, Israel A case of septic cavernous sinus thrombosis is described which was observed with high resolution computed tomography (CT). The significant CT findings in cavernous sinus thrombosis (CST) include irregular filling defects within a widened enhancing cavernous sinus. Concomitant findings are unilateral or bilateral swelling of the orbital soft tissues and sinusitis.
Septic thrombosis o f the cavernous sinus is always a severe condition, yet it is very u n c o m m o n . In the preantibiotic era, the average physician could expect to see only two or three cases in a lifetime (Watkins and Chisholm, 1920). Only 10 cases were encountered at the M a y o Clinic during a 32 year period (Lillie, 1951). In 1961 a review o f the literature, revealed an 80% mortality with 75% residual morbidity in the survivors (Yarington, 1961). In a follow-up review m a d e after the introduction o f antibiotics, a m a r k e d improvement was found, a 12.6% mortality and a 23% morbidity (Yarington, 1977). In this report a case o f septic cavernous sinus t h r o m b o sis i s described, with particular attention to its features as observed with a high resolution CT. A coronal view o f the lesion is presented, possibly for the first time.
CASE REPORT A 16-year-oldgirl was brought to hospital, with a sty of the right eye of 3 days duration. On admission she complained of a severe frontal headache, right visual loss, and examination revealed right orbital cellulitis with an immobile eyeball. The pupil was dilated and reacted very slowly to light. The left eyelid also was swollen and, to a lesser degree, tender. Lumbar puncture showed cerebrospinal fluid containing protein of 200 mg/dl, glucose of 102 mg/dl and 2133 polymorphonuclear cells. Culture confirmed the presence of Staphylococcus aureus. Cranial CT was carried out with the Exel 1800 Scanner (Elscint), using a high resolution technique, after bolus injection of meglumine/ sodium diatrizoate (urographin 76%) and obtaining slices of 2 mm thickness. An axial plane of section parallel to the orbito-meatal line was used, and viewsof the cavernous sinuses were reformatted in the coronal plane. The enhanced CT slices showed abnormal enlargement of the cavernous sinuses, which contained irregular filling defects. These were more marked on the right side. The enlarged right cavernous sinus extended into the right superior ophthalmic vein. Right ptosis, exophthalmos with periorbital swelling, bilateral ethmoid and sphenoid sinusitis were also observed (Figs 1 and 2). The right sphenoidol sinus contained an opaque fluid level. Bilateral trans-septal sphenoidotomy was performed and necrotic purulent debris was recovered. The patient improved slowly and steadily following vigorous antibiotic treatment. She was discharged after a month with residual ptosis, impaired abduction and a moderate visual deficit in the right eye.
DISCUSSION The name 'cavernous sinus' is attributed to Winslow who, in 1732, noted the similarity o f the interior o f this Correspondence to: Dr R. Ben-Uri.
structure to the corpus cavernosum o f the penis. M o d e r n anatomists view it as a large u n b r o k e n venous channel, crisscrossed by a varying n u m b e r o f fibrous trabeculations; it m a y also appear as a plexus o f smaller veins (Harris and R h o t o n , 1976). The neurovascular relationships are important in understanding the anatomical and clinical manifestations o f the lesion. The horizontal portion o f the internal carotid artery surrounded by its plexus o f sympathetic nerves, passes forward t h r o u g h the cavernous sinus. The abducens" nerve passes between the artery and the lateral wall o f the sinus, and the oculomotor, trochlear and ophthalmic and maxillary divisions o f the trigeminat nerves lie within the lateral wall, separated from the venous blood by a thin fibrous sheath (Bedford, 1966; Harris and R h o t o n , 1976; W o o d r u f f et al., 1986). The c o m m o n e s t causes o f septic CST are nasal or midfacial skin infections, and paranasal sinus infections (Clune, 1963; Pascarelli and Lemlich, 1964; Sofferman and Burlington, 1983; Karlin and Robinson, 1984; Harb o u r et al., 1984). After the thrombophlebitic process reaches the cavernous sinus, the signs and s y m p t o m s evolve according to the local anatomy. Thus the signs m a y be grouped according to the following aetiologies: venous obstruction, involvement o f adjacent nerves, and generalised sepsis and meningitis (Sekhar et al., 1980; Karlin and Robinson, 1984). In the majority o f the cases reported in the literature, the diagnosis has been made on clinical g r o u n d s (Dixon, 1926; Walsh, 1937). Only a few cases have been documented pathologically (Dixon, 1926): orbital cellulitis, septic thrombi in the cavernous sinus, thrombophlebitis o f the ophthalmic veins and meningitis were observed u p o n p o s t m o r t e m examination. In o u r patient the clinical findings were consistent with bilateral septic CST, the infection being more severe on the right side. Axial C T scans and the coronal reconstructed view, showed several irregular filling defects within the enlarged and enhancing cavernous sinus, which were interpreted as CST. These filling defects were thrombi. The lateral margin o f the cavernous sinus remained straight without evidence o f localised expansion. Proptosis, periorbital swelling and enlarged periorbital muscles were shown within the right orbit. However, these are f o u n d to be nonspecific signs which m a y a c c o m p a n y orbital cellulitis, dysthyroid ophthalmopathy, carotid cavernous fistula and acute orbital pseudot u m o r ( E n z m a n n et al., 1979; Z i m m e r m a n and Bilaniuk, 1980; Kline et al., 1981). Bilateral enhancement o f the cavernous sinus is a n o r m a l finding. Unilateral visualisation should be viewed as a b n o r m a l (Segall et al., 1982). In the n o r m a l individual symmetrical filling defects m a y be seen within the enhancing cavernous sinus corresponding to the anatomical course o f the adjacent cranial nerves ( E n z m a n n et al., 1979; Segal et al., 1982). They m a y also be related to the
SEPTIC THROMBOSIS OF THE CAVERNOUS SINUS
521
Fig. 1 - E n h a n c e d axial CT slices in 16-year-old girl with septic cavernous sinus thrombosis. The right sinus is enlarged and contains irregular areas of low attenuation which are confirmed in the coronal reformatted view. Bilateral sphenoidal sinusitis is present.
lack of enhancement of the intracavernous part of the carotid siphon in cases of thrombosis (Mathew et al., 1971). Trigeminal neurinomas and intracavernous metastases may also be revealed as filling defects within the enhancing cavernous sinus. These lesions cause localized expansion and present a different clinical picture (Woodruffet al., 1986; Kline et al., 1981). The presence of adipose tissue within the cavernous sinus has been described as an incidental finding and such deposits may be confused with clots. However, careful analysis with high-resolution thin-section CT scans establish their fatty nature (Bachow et al., 1984). The adipose deposits are commonly found in the anterior lateral end and the posterior parts of the cavernous sinus where the fat is visible (Hosoya et al., 1986). Large amounts of fat have been found in association with Cushing's disease (37.5 %). Angiography and venography have a limited role in CST. A technically good cerebral angiogram will reveal the cavernous sinuses in only about 42% of normal cases
(Osborn, 1980). Orbital venography, while revealing diagnostic non-filling of the cavernous sinus, may be hazardous and disseminate the infection, or contribute to further extension of the thrombosis (Brismar and Brismar, 1977; Rao et aL, 1981; Clifford-Jones et al., 1982). The diagnosis of septic cavernous sinus thrombosis is based on demonstrating an infective process on the face, orbital area or the paranasal sinuses, associated with clinical evidence of progressive involvement of structures anatomically related to the cavernous sinus. Direct CT demonstration o f thrombosis within the cavernous sinus has only rarely been reported (Ahmadi et al., 1985). The explanation for this is that the early CT scanners failed to provide adequate detailed imaging of the cavernous sinus. However, the use of high resolution and a slice thickness of 3 mm or less (Rao et al., 1981; Clifford-Jones et al., 1982) permits the non-vascular contents of the sinus to be seen in axial and coronal planes.
522
CLINICAL RADIOLOGY
Fig. 2 Associated features of cavernous sinus thrombosis. Axial CT slices show sphenoidal sinusitis, proptosis and peri-orbital swelling and an engorged right superior ophthalmic vein.
REFERENCES
Ahmadi, J, Keane, JR, Segall, HD & Zee, CS (1985). CT observation pertinent to septic CST. AmericanJournalof Neuroradiology, 6, 755 758. Bachow, TB, Hesselink, JR, Aaron, JO, Davis, KR & Taveras, JM (1984). Fat deposition in the cavernous sinus in Cushing disease. Radiology, 153, 135-136. Bedford, MA (1966). The cavernous sinus. British Journal of Ophthalmology, 50, 41-46. Brismar, G & Brismar, J (1977). Thrombosis of the intraorbital veins and cavernous sinus. Acta Radiologica Diagnosis', 18, 145 153. Clifford-Jones, RE, Ellis, CJK, Stevens, JM & Turner, A (1982).
Cavernous sinus thrombosis. Journal of Neurology, Neurosurgery and Psychiatry, 45, 1092 1097. Clune, JP (1963). Septic thrombosis within the cavernous chamber. American Journal of Ophthalmology, 56, 33-39. Dixon, OJ (1926). The pathologic exam in cavernous sinus thrombosis. Journal of American Medical Association, 87, 1088-1096. Enzmann, DR, Donaldson, SS & Kriss, JP (1979). Appearance of Grave's disease on orbital computed tomography. Journal of Computer Assisted Tomography, 3, 815 819. Harbour, RC, Trobe, JD & Ballinger, WE (1984). Septic cavernous sinus thrombosis associated with gingivitis and parapharyngeal abscess. Archives of Ophthalmology, 102, 94 97. Harris, FS & Rhoton, AL Jr (1976). Anatomy of the cavernous sinus: a microsurgical study. Journal of Neurosurgery, 45, 169 180. Hosoya, T, Kera, M, Suzaki, T & Yamaguchi, K (1986). Fat in the normal sinus. Neuroradiology, 28, 264-266. Kartin, RJ & Robinson, WA (1984). Septic CST. Annals of Emergency Medicine, 13, 449-455. Kline, LB, Acker, JD, Post, MJD & Vitek, JJ (1981). The cavernous study: A computed tomographic study. American Journal of Neuroradiology, 2, 299-305. Lillie, HI (1951). Prognosis of septic thrombophlebitis of the cavernous sinus. Journal of the International College of Surgeons, 15, 754-759. Mathew, NT, Abraham, J, Taori, GM & Iyer, GV (1971). Internal carotid artery occlusion in cavernous sinus thrombosis. Archives of Neurology, 24, 11 16. Osborn, AG (1980). Craniofacial venous plexuses: angiographic study. American Journal of Neuroradiology, 1, 541-545. Pascarelli, E & Lemlich, A (1964). Diplopia and photophobia as promotary symptoms in CST. Annals of Otology, Rhinolology and Laryngology, 73, 210 217. Rao, KCVG, Knipp, HC & Wagner, EJ (1981). Computed tomographic findings in cerebral and venous thrombosis. Radiology, 140, 391 398. Segall, HD, Ahmadi, J, McComb, JG, Zee, CS, Becker, TS & Han, JS (1982). Computed tomographic observation pertinent to intracranial venous thrombotic and occlusive disease in children. Radiology, 143, 441 449. Sekhar, LN, Dujovny, M & Rao, GR (1980). Carotid CST caused by Aspergillus fumigatus. Journal of Neurosurgery, 52, 120-125. Sofferman, RA & Burlington, VT (1983). Cavernous sinus thrombophlebitis secondary to sphenoid sinusitis. Laryngoscope, 93, 798-800. Walsh, FE (1937). Ocular signs of thrombosis of the intracranial sinuses. Archives of Ophthalmology, 17, 46-65. Watkins, SS & Chisholm, J (1920). Twelve cases of thrombosis of the cavernous sinus. Archives of Surgery, 1, 483-512. Woodruff, WW Jr, Yeates, AE & McLendon, RE (1986). Perineural tumor extension to the cavernous sinus from superficial facial carcinoma. CT manifestations. Radiology, 161, 395-399. Yarington, CT Jr (1961). The prognosis and treatment of cavernous sinus thrombosis: Review of 878 cases in the literature. Annals" of Otology, Rhinology and Laryngology, 70, 263 267. Yarington, CT Jr (1977). CST revisited. Proceedingsof the Royal Society of Medicine, 70, 456 459. Zimmerman, RA & Bilaniuk, LT (1980). CT of orbital infection and its cerebral complications. American Journal of Roentgenology, 134, 45 52.
Case Report: Septic Thrombosis of the Cavernous Sinus" Diagnosis with the Aid of Computed Tomography R. BEN-URI,
L. P A L M A and Z. K A V E H
Department o f Radiology, Central Emek Hospital, Afula, Israel A case of septic cavernous sinus thrombosis is described which was observed with high resolution computed tomography (CT). The significant CT findings in cavernous sinus thrombosis (CST) include irregular filling defects within a widened enhancing cavernous sinus. Concomitant findings are unilateral or bilateral swelling of the orbital soft tissues and sinusitis.
Septic thrombosis o f the cavernous sinus is always a severe condition, yet it is very u n c o m m o n . In the preantibiotic era, the average physician could expect to see only two or three cases in a lifetime (Watkins and Chisholm, 1920). Only 10 cases were encountered at the M a y o Clinic during a 32 year period (Lillie, 1951). In 1961 a review o f the literature, revealed an 80% mortality with 75% residual morbidity in the survivors (Yarington, 1961). In a follow-up review m a d e after the introduction o f antibiotics, a m a r k e d improvement was found, a 12.6% mortality and a 23% morbidity (Yarington, 1977). In this report a case o f septic cavernous sinus t h r o m b o sis i s described, with particular attention to its features as observed with a high resolution CT. A coronal view o f the lesion is presented, possibly for the first time.
CASE REPORT A 16-year-oldgirl was brought to hospital, with a sty of the right eye of 3 days duration. On admission she complained of a severe frontal headache, right visual loss, and examination revealed right orbital cellulitis with an immobile eyeball. The pupil was dilated and reacted very slowly to light. The left eyelid also was swollen and, to a lesser degree, tender. Lumbar puncture showed cerebrospinal fluid containing protein of 200 mg/dl, glucose of 102 mg/dl and 2133 polymorphonuclear cells. Culture confirmed the presence of Staphylococcus aureus. Cranial CT was carried out with the Exel 1800 Scanner (Elscint), using a high resolution technique, after bolus injection of meglumine/ sodium diatrizoate (urographin 76%) and obtaining slices of 2 mm thickness. An axial plane of section parallel to the orbito-meatal line was used, and viewsof the cavernous sinuses were reformatted in the coronal plane. The enhanced CT slices showed abnormal enlargement of the cavernous sinuses, which contained irregular filling defects. These were more marked on the right side. The enlarged right cavernous sinus extended into the right superior ophthalmic vein. Right ptosis, exophthalmos with periorbital swelling, bilateral ethmoid and sphenoid sinusitis were also observed (Figs 1 and 2). The right sphenoidol sinus contained an opaque fluid level. Bilateral trans-septal sphenoidotomy was performed and necrotic purulent debris was recovered. The patient improved slowly and steadily following vigorous antibiotic treatment. She was discharged after a month with residual ptosis, impaired abduction and a moderate visual deficit in the right eye.
DISCUSSION The name 'cavernous sinus' is attributed to Winslow who, in 1732, noted the similarity o f the interior o f this Correspondence to: Dr R. Ben-Uri.
structure to the corpus cavernosum o f the penis. M o d e r n anatomists view it as a large u n b r o k e n venous channel, crisscrossed by a varying n u m b e r o f fibrous trabeculations; it m a y also appear as a plexus o f smaller veins (Harris and R h o t o n , 1976). The neurovascular relationships are important in understanding the anatomical and clinical manifestations o f the lesion. The horizontal portion o f the internal carotid artery surrounded by its plexus o f sympathetic nerves, passes forward t h r o u g h the cavernous sinus. The abducens" nerve passes between the artery and the lateral wall o f the sinus, and the oculomotor, trochlear and ophthalmic and maxillary divisions o f the trigeminat nerves lie within the lateral wall, separated from the venous blood by a thin fibrous sheath (Bedford, 1966; Harris and R h o t o n , 1976; W o o d r u f f et al., 1986). The c o m m o n e s t causes o f septic CST are nasal or midfacial skin infections, and paranasal sinus infections (Clune, 1963; Pascarelli and Lemlich, 1964; Sofferman and Burlington, 1983; Karlin and Robinson, 1984; Harb o u r et al., 1984). After the thrombophlebitic process reaches the cavernous sinus, the signs and s y m p t o m s evolve according to the local anatomy. Thus the signs m a y be grouped according to the following aetiologies: venous obstruction, involvement o f adjacent nerves, and generalised sepsis and meningitis (Sekhar et al., 1980; Karlin and Robinson, 1984). In the majority o f the cases reported in the literature, the diagnosis has been made on clinical g r o u n d s (Dixon, 1926; Walsh, 1937). Only a few cases have been documented pathologically (Dixon, 1926): orbital cellulitis, septic thrombi in the cavernous sinus, thrombophlebitis o f the ophthalmic veins and meningitis were observed u p o n p o s t m o r t e m examination. In o u r patient the clinical findings were consistent with bilateral septic CST, the infection being more severe on the right side. Axial C T scans and the coronal reconstructed view, showed several irregular filling defects within the enlarged and enhancing cavernous sinus, which were interpreted as CST. These filling defects were thrombi. The lateral margin o f the cavernous sinus remained straight without evidence o f localised expansion. Proptosis, periorbital swelling and enlarged periorbital muscles were shown within the right orbit. However, these are f o u n d to be nonspecific signs which m a y a c c o m p a n y orbital cellulitis, dysthyroid ophthalmopathy, carotid cavernous fistula and acute orbital pseudot u m o r ( E n z m a n n et al., 1979; Z i m m e r m a n and Bilaniuk, 1980; Kline et al., 1981). Bilateral enhancement o f the cavernous sinus is a n o r m a l finding. Unilateral visualisation should be viewed as a b n o r m a l (Segall et al., 1982). In the n o r m a l individual symmetrical filling defects m a y be seen within the enhancing cavernous sinus corresponding to the anatomical course o f the adjacent cranial nerves ( E n z m a n n et al., 1979; Segal et al., 1982). They m a y also be related to the
SEPTIC THROMBOSIS OF THE CAVERNOUS SINUS
521
Fig. 1 - E n h a n c e d axial CT slices in 16-year-old girl with septic cavernous sinus thrombosis. The right sinus is enlarged and contains irregular areas of low attenuation which are confirmed in the coronal reformatted view. Bilateral sphenoidal sinusitis is present.
lack of enhancement of the intracavernous part of the carotid siphon in cases of thrombosis (Mathew et al., 1971). Trigeminal neurinomas and intracavernous metastases may also be revealed as filling defects within the enhancing cavernous sinus. These lesions cause localized expansion and present a different clinical picture (Woodruffet al., 1986; Kline et al., 1981). The presence of adipose tissue within the cavernous sinus has been described as an incidental finding and such deposits may be confused with clots. However, careful analysis with high-resolution thin-section CT scans establish their fatty nature (Bachow et al., 1984). The adipose deposits are commonly found in the anterior lateral end and the posterior parts of the cavernous sinus where the fat is visible (Hosoya et al., 1986). Large amounts of fat have been found in association with Cushing's disease (37.5 %). Angiography and venography have a limited role in CST. A technically good cerebral angiogram will reveal the cavernous sinuses in only about 42% of normal cases
(Osborn, 1980). Orbital venography, while revealing diagnostic non-filling of the cavernous sinus, may be hazardous and disseminate the infection, or contribute to further extension of the thrombosis (Brismar and Brismar, 1977; Rao et aL, 1981; Clifford-Jones et al., 1982). The diagnosis of septic cavernous sinus thrombosis is based on demonstrating an infective process on the face, orbital area or the paranasal sinuses, associated with clinical evidence of progressive involvement of structures anatomically related to the cavernous sinus. Direct CT demonstration o f thrombosis within the cavernous sinus has only rarely been reported (Ahmadi et al., 1985). The explanation for this is that the early CT scanners failed to provide adequate detailed imaging of the cavernous sinus. However, the use of high resolution and a slice thickness of 3 mm or less (Rao et al., 1981; Clifford-Jones et al., 1982) permits the non-vascular contents of the sinus to be seen in axial and coronal planes.
522
CLINICAL RADIOLOGY
Fig. 2 Associated features of cavernous sinus thrombosis. Axial CT slices show sphenoidal sinusitis, proptosis and peri-orbital swelling and an engorged right superior ophthalmic vein.
REFERENCES
Ahmadi, J, Keane, JR, Segall, HD & Zee, CS (1985). CT observation pertinent to septic CST. AmericanJournalof Neuroradiology, 6, 755 758. Bachow, TB, Hesselink, JR, Aaron, JO, Davis, KR & Taveras, JM (1984). Fat deposition in the cavernous sinus in Cushing disease. Radiology, 153, 135-136. Bedford, MA (1966). The cavernous sinus. British Journal of Ophthalmology, 50, 41-46. Brismar, G & Brismar, J (1977). Thrombosis of the intraorbital veins and cavernous sinus. Acta Radiologica Diagnosis', 18, 145 153. Clifford-Jones, RE, Ellis, CJK, Stevens, JM & Turner, A (1982).
Cavernous sinus thrombosis. Journal of Neurology, Neurosurgery and Psychiatry, 45, 1092 1097. Clune, JP (1963). Septic thrombosis within the cavernous chamber. American Journal of Ophthalmology, 56, 33-39. Dixon, OJ (1926). The pathologic exam in cavernous sinus thrombosis. Journal of American Medical Association, 87, 1088-1096. Enzmann, DR, Donaldson, SS & Kriss, JP (1979). Appearance of Grave's disease on orbital computed tomography. Journal of Computer Assisted Tomography, 3, 815 819. Harbour, RC, Trobe, JD & Ballinger, WE (1984). Septic cavernous sinus thrombosis associated with gingivitis and parapharyngeal abscess. Archives of Ophthalmology, 102, 94 97. Harris, FS & Rhoton, AL Jr (1976). Anatomy of the cavernous sinus: a microsurgical study. Journal of Neurosurgery, 45, 169 180. Hosoya, T, Kera, M, Suzaki, T & Yamaguchi, K (1986). Fat in the normal sinus. Neuroradiology, 28, 264-266. Kartin, RJ & Robinson, WA (1984). Septic CST. Annals of Emergency Medicine, 13, 449-455. Kline, LB, Acker, JD, Post, MJD & Vitek, JJ (1981). The cavernous study: A computed tomographic study. American Journal of Neuroradiology, 2, 299-305. Lillie, HI (1951). Prognosis of septic thrombophlebitis of the cavernous sinus. Journal of the International College of Surgeons, 15, 754-759. Mathew, NT, Abraham, J, Taori, GM & Iyer, GV (1971). Internal carotid artery occlusion in cavernous sinus thrombosis. Archives of Neurology, 24, 11 16. Osborn, AG (1980). Craniofacial venous plexuses: angiographic study. American Journal of Neuroradiology, 1, 541-545. Pascarelli, E & Lemlich, A (1964). Diplopia and photophobia as promotary symptoms in CST. Annals of Otology, Rhinolology and Laryngology, 73, 210 217. Rao, KCVG, Knipp, HC & Wagner, EJ (1981). Computed tomographic findings in cerebral and venous thrombosis. Radiology, 140, 391 398. Segall, HD, Ahmadi, J, McComb, JG, Zee, CS, Becker, TS & Han, JS (1982). Computed tomographic observation pertinent to intracranial venous thrombotic and occlusive disease in children. Radiology, 143, 441 449. Sekhar, LN, Dujovny, M & Rao, GR (1980). Carotid CST caused by Aspergillus fumigatus. Journal of Neurosurgery, 52, 120-125. Sofferman, RA & Burlington, VT (1983). Cavernous sinus thrombophlebitis secondary to sphenoid sinusitis. Laryngoscope, 93, 798-800. Walsh, FE (1937). Ocular signs of thrombosis of the intracranial sinuses. Archives of Ophthalmology, 17, 46-65. Watkins, SS & Chisholm, J (1920). Twelve cases of thrombosis of the cavernous sinus. Archives of Surgery, 1, 483-512. Woodruff, WW Jr, Yeates, AE & McLendon, RE (1986). Perineural tumor extension to the cavernous sinus from superficial facial carcinoma. CT manifestations. Radiology, 161, 395-399. Yarington, CT Jr (1961). The prognosis and treatment of cavernous sinus thrombosis: Review of 878 cases in the literature. Annals" of Otology, Rhinology and Laryngology, 70, 263 267. Yarington, CT Jr (1977). CST revisited. Proceedingsof the Royal Society of Medicine, 70, 456 459. Zimmerman, RA & Bilaniuk, LT (1980). CT of orbital infection and its cerebral complications. American Journal of Roentgenology, 134, 45 52.