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Ischemic Chiasma Syndrome

K . Franc is Lee 1

Thirty patients with chiasma syndrome attributed to ischemic (4) poly tome encephalography (contin uous insufflation technique processes of various origins are described. The initial diagnosis with 50-80 ml of nitrous oxide). In recent years, poly tome gas was made after an investigation based on polytome pneumoen­ encephalography has been replaced almost completely by high­ cephalography and angiography. This diagnosis was confirmed resoluti on CT. later with the use of high-resolution computed tomography (CT) We now use a GE 8800 CT scanner with a high-dose contrast and refined angiographic techniques. The ischemic chiasma mediu m enhancement. Excellent opacification of the circle of Willis, syndrome may be classified into five pathogenetic categories: cavernous sinus, and the is obtained with a rapid (1) mechanical compression of the secondary to ectatic bolus injection and drip infusion (up to 82 g of iodine). Axial CT tortuous arteries; (2) vascular occlusion secondary to athero­ secti ons of the sell a turcica and suprasellar region inc luding the matous plaque formation; (3) arachnoiditis with fibrosis; (4) ar­ orbits are obtained wi th 1.5 mm contiguous sections (25-30 slices). teritis of various origins; and (5) postpartum necrosis. Sophisti­ Coronal and sagittal reformatted images are then obtain ed. When cated neurologic procedures including magnification angiogra­ the sell a turcica is not grossly enlarged, we perform direct coronal phy and high-resolution CT are essential in ruling out a mass CT scanning by the 1.5 mm contiguous imaging method. The 5 mm lesion and correlating the clinical and radiologic findings of this with 3 mm increments technique is suitable for the evaluati on of syndrome. patients with enlarged sella in axial and coronal planes. With these methods, the hypothalamic part of the including the optic and infundibular recesses is clearly delineated , Chiasma syndrome is most commonly caused by a neoplastic as are the ch iasm, optic nerves, pituitary gland, infundibulum, and lesion near the sell a turcica that affects the . However, adjacent vessels. We stil l occasionall y perform poly tome gas en­ identical chiasmati c visual defects may li kewise be produced by a cephalography with N2 0 for evaluation of optochiasmatic arach­ vari ety of nonneoplastic processes involving the chi asm. Arterio­ noiditis when CT findings are equivocal. sclerosis is accepted as one of these [1 , 2]. We have also reported the chiasma syndrome attributable to several ischemic processes [3]. Results More recentl y, we evaluated ischemi c chiasma syndrome (ICS) using high-resolution computed tomog raphy (CT) with high-dose Thirty patients in fi ve eti ologic categories of ICS were identified contrast medium enhancement and magnification angiography. In on the basis of clinical and neu roradiologic evaluations (table 1). ord er to correlate clinical and radiologic features of ICS, it is Type 1 consisted of ICS caused by mechanical compression of essential to demonstrate the precise anatomic relations among the the and c hiasm due to red undant ectatic an teri or cere­ optic nerve, chi asm, pituitary gland, and adjacent vascul ature. The bral and / or carotid arteries. Ei ght patients (four men and four anatomi c relation of the neurovascular structu res in and around the worn en) made up this group. Low-lying ectatic anterior cerebral sell a turcica has been studied by many investigators [4-7]. We have arteri es were readily demonstrated to compress the chiasm or optic also studied the vasculature of the optic nerve, chi asm, hypothala­ nerve against th e sell a as seen on poly tome gas encephalogram [3] mu s, pituitary gland, and in cadavers, showing or on CT (fig. 1). Seven of the eight cases showed an empty sell a. multiple common blood supplies in the area [8]. Type 2 consisted of ICS caused by atheromatous narrowing or occlusion of the carotid arteries and their branches. Five patients (three men and two women) were in th is category. Angiograms with Materials and Methods subtraction technique demonstrated atheromatous narrowing or occlusion of the carotid arteries, with the carotid siphon and / or the Over a 16 year peri od, more than 300 patients with chiasmatic origin of the internal carotid artery ollen being involved bil aterally visual fi eld defects were evaluated at Thomas Jefferson University (fig. 2). Empty sell a was noted in four of the five cases. One patient Hospital, Willis Eye Hospital, and the University of Texas Health showed a focal infarct in the right parietal region. Science Center at Houston. Extensive neuroophthalmologic, neu­ Type 3 ICS was caused by vascular encasement and occlusion roradiologic, and endocrinologic investigations were carried out in secondary to diffuse arachnoidal adhesion and thic kening. This th ese patients to determine the cause of chiasma syndrome. In most group consisted of nine patients (si x women and three men). Dis­ cases, the syndrome was caused by prim ary or secondary neo­ tortion and / or obliteration of the suprasellar cistern and recesses plasms. of the third ventricle could be demonstrated clearly on poly tome Before the advent of CT, our protocol for neuroradiologic evalu­ gas encephalography and CT (figs. 3 and 4). Seven of the nine ati on of chiasma syndrome compri sed: (1) plain skull fil ms, (2) optic patients showed an empty sella. foramen views, (3) magnificati on angiography with subtraction, and Type 4 ICS was caused by arteritis of various ori gins. There were

1 Department of Radiotogy, University of Texas Health Science Center at Houston. 6431 Fannin St., Houston, TX 77030. AJNR 4:777-780, May/ June 1983 0195-6108/ 83/ 0403-0777 $00.00 © American Roentgen Ray Society 778 MISCELLANEOUS AJNR:4 , May/ June 1983

TABLE 1: Summary of Findings in Ischemic Chiasma Syndrome

No. Cases Type of fCS (Age Range) Visual Im pairment Pi tuitary Function Total With Empty Sella 1: Low-lying ectatic anterior cer- ebral and carotid, pericall osal, or carotid arteries (60-80) 8 7 Slowly progressive Low normal 2: Atherosclerotic plaque forma- Gradual or acute tion (50-70) 5 4 onset Usually low 3: Optochiasmatic arachnoiditis Gradual and and fibrosis (20-60) 9 7 progressive Usually low 4 : Arteritis with stenosis and dil- atation of vessels (50-70) 3 2 Acute onset Low 5: Postpartum pituitary necrosis Acute onset, slow and ischemia (20-30) 5 5 recovery Depressed

30 25

A c Fig . .- 79-year-old woman with progressive bitemporal hemianopia due ing optic chiasm. Piluitary stalk run s diagonally in front of dolichoectatic 10 low-lyi ng arleriosclerolic anlerior cerebral arteri es (ICS type 1). A, High­ basilar artery (8). Note partly empty sella. C, Coronal reformatted image with resolution CT scan demonstrates excellent opacification of circle of Willis. high window level shows ectatic cavernous carotid (C) and anterior cerebral Figures include carotid arlery (C), basilar artery (8), infundibulum of pituitary arteries (arrows) with scleroti c margin due to calcified vascular wall s. Anterior (I), and low-lyin g anlerior cerebral arteries (arrow). B, Reformatted sag ittal cerebral arteries are situated so low th at optic chiasm is compressed and image of axial CT shows low-lying anterior cerebral artery (arrow) compress- fl attened beneath low-lying vessels. Part of pituitary stalk is seen in center.

three patients (two women and one man) who showed angiographic Ischemic chiasma syndrome is believed to be secondary to evidence of arteritis, associated with pituitary insufficiency and various ischemic processes without evidence of mass lesion. There­ bitemporal hemianopia. Two of the three patients demonstrated an fore, a mass lesion should be categorically excluded by neuroradi­ empty sell a. Angiography with subtrac tion showed evidence of ologic prqcedure before the diagnosis of ICS is considered [2, 3, arteritis with vascular stenosis (fig. 5). 10]. Type 5 consisted of postpartum chiasma syndrome associated Tubular or fusiform dil atation of arteries may compress the ad­ with pituitary necrosis. The five women in this group had an empty jacent structures, producing neurologic symptoms [9, 10]. Similarly, sell a on poly tome gas encephalogram [3, 9] or CT scan (fig. 6). ICS may develop secondary to mechanical compression of the optic Only one patient showed a slightly enlarged . chiasm, optic nerve junction, or both by a tortuous ectatic anterior cerebral artery [2, 3, 10]. In the case of a pituitary tumor growing Discussion upward , the anterior cerebral artery may act as a restrictive cord on the dorsal surface of the prechiasmatic optic nerve, with the The chiasma syndrome is usually produced by compression of resultant notching or grooving accounting for chiasmatic the chiasm. A variety of parasellar mass lesions, including neo­ defect [1 , 4]. Infarction of the chiasm may develop as a result of plasms, granulomas, aneurysms, foreign bodies, and hematomas, focal ischemia produced by an intrinsic or extrinsic tumor [1 , 11]. may be responsible [1]. Nontumorous lesions such as demyelinating In order to establish the diagnosis of type 1 ICS, the anatomic disease and trauma are rarer but definite causes. relation of the anterior and/ or carotid arteries to the' chiasm and AJNR:4, May/ June 1983 MISCELLANEOUS 779

A B

Fig. 4.-25-year-old woman with progressive bitemporal hemianopia due to optochiasmati c arachnoiditis (ICS type 3). A, Axial CT with 1.5 mm section shows part ial obliterati on of suprasell ar cistern. B, Optic chiasm appears prominent with indistinct margin (arrows). C, Sagittal reformatted image shows partial eHacement of recesses of third ventricle with matt ed chiasm and opti c nerve complex (arrow). Sella is partly empty.

A B tuous anterior cerebral artery against th e chi asmati c sulcus or Fig, 2. - 57-year-old man with progressive bitemporal hemianopia with small right nasal field defect due to severe atheromatous disease of carotid planum sphenoid ale. arteri es (lCS type 2). A, Right carotid arteriogram shows marked atheroma­ Ischemia of the opti c nerve and chi asm may be produced by tous stenosis of internal carotid artery at its origin (arrowhead). Seg mental atheromatous pl aque in the circle of Willis (especially) and in the narrowing of carotid siphon is also seen (arrow). B, Left carotid arteri ogram cavernous portions of the carotid arteri es, with partial or complete shows irregular threadlike narrowing with distal occlusion of internal caroti d artery (arrows). Marked atheromatous narrowing of left external carotid at occlusion of the arteri al twigs supplying th e optic stru cture, as origin (arrowhead). observed in type 2. Advanced ath eromatous caroti d disease may produce pituitary in sufficiency in addition to visual symptoms be­ cause of the common blood supply to the pituitary and chiasm [6, 8]. Magnificati on angiography with subtracti on technique is impor­ Fig. 3. - 32-year-old man with tant in demonstrating the atheromatous changes. progressive visual loss with bitem­ Type 3 IC S was due to diffuse arachnoiditi s with dense fibrosis poral hemianopia due to optochias­ matic arachnoiditis with fibrosis (l CS encasing the optic structures. Fi ve of the nine cases were related type 3). Poly tome pneumoenceph al­ to th e previous radiation therapy for pituitary tumors with resultant ogram shows obliteration of opti c fibrosis, while th e oth er four cases were second ary to sarcoidosis b nd infundibular recesses (large ar­ (three cases) and a nonspecific granuloma (one case). Poly tome row), with nonfilling of suprasellar cistern and cistern a lamina term i­ encephalography with continuous insufflati on of N2 0 provided the nalis. Trapped air in interpenduncu­ best result in delineating the obliterated recesses of th e third lar fossa and shortening of dorsum ventricle as well as trapping of gas in the interpedun cul ar cistern, se llae (small arrow) also present. At with poor or no fi lling of th e suprasell ar cistern or cistern a lamina surgery, diffuse thickening with adhesion of arachnoid around optic terminalis (fig. 3). CT scanning with diluted metri zam ide is helpful chiasm and nerves was found. also in demonstrating a di stort ed chiasm or opti c nerve, but we consider poly tome pneumoencephalography to be superi or in as­ sessing the degree of arachnoidal adhesions. Type 4 ICS was produced by arteritis of vari ous origins. Giant­ optic nerves should be precisely delineated by means of poly tome cell arteritis, systemic lupus erythematosus, and periarteritis no­ pneumoencephalography or high-resolution CT. Although direct dosa, respectively, were responsible for arteritis with resultant ICS coronal CT provided useful information about the anatomic arrange­ in three cases investi gated. Again, su btraction angiography was ment of the chiasm and arteries, axial CT with coron al and sagittal essential in establi shing th e diagnosis in this group. reformatted images is generally far superior in delineating the Type 5 ICS was secondary to postpartum pituitary necrosis or neurovascular anatomy. This is presumably due to relatively artifact­ Sheehan syndrome. According to Sheehan [1 2], postpartum necro­ free images on axial scans (fig. 1). In our experi ence, presell ar sis of the an terior lobe of th e pituitary is not uncommon, and acute chiasm seems to be more readily compressed by a low-lying tor- necrotic lesions are mostly related to postpartum necrosis. How- 780 MISCELLANEOUS AJNR:4, May/June 1983

ever, diabetes, cranial arteritis, and cavernous sinus th rombosis are mental in some cases [8]. It is probable, however, that defi cient also etiologic factors. diaphrag ma sellae may be caused by ischemic necrosis with resul­ We noted a very high in cidence (25 of 30: 83%) of empty sella tant intrasellar extension of subarachnoid space, thus producing with ICS. Incompetent diaphragma sell ae may be purely develop- th e empty sell a syndrome. The recognition of ICS is important because this syndrome is related to vari ous ischemi c processes that produce nonsurgical lesions. The great majority of the chiasma syndromes are secondary to mass lesions that are often amenable to surgery.

REFERENCES

1. Walsh FB, Hoyt WF. Clinical neuro-ophthalmology. Baltimore: Williams & Wilkins, 1975: 1778, 1883, 2100 2. Lee KF, Schatz NJ, Hodes PJ. Arteriosclerotic chiasmal syn­ drome. Presented at the annual meeting of the Ameri can Society of Neuroradiology, New Orleans, September 1968 3. Lee KF, Schatz NJ . Ischemic chiasmal syndrome. Presented at th e X Symposium Neuroradiologicum, Punta del Este, Uru­ guay, March 19 74. Acta Radial [Suppl} (Stockh ) 1975;347: 131- 148 A 4 . Schaeffer JP. Some points in the regional anatomy of the optic path ways with special reference to tumors of th e hypophysis cerebri and resulting ocular changes. Anat Rec 1924;28: 243 - 279 5. Bull J. Th e norm al variations in the position of th e optic recess of the third ventricle. Acta Radio/1956;4 6:72- 80 6. Dawson BH . The blood vessels of the human optic chiasma and their relati on to those of the hypophysis and hypoth alamu s. Brain 1958;81 :207- 2 17 7. Parkinson D. Coll ateral circulati on of cavern ous carotid artery; anatomy. Can J Surg 1964;7: 251-267 8 . Lee KF, Parke W, Lin SR, Choi HY, Schatz NJ. The vasculature of the diaphrag ma sellae. A postmortem injecti on study. Neu­ roradiology 1978;2 6 :281-283 9. Lee KF, Lin SA. Neuroradiology of sellar and jux tasellar le­ sions. Springfield, IL: Th omas, 1979:352, 403 10. Hilton GF, Hoyt WF. An arteri osclerotic chi asmal syndrome; bitemporal hemianopi a associated with fusiform dilatation of B the anterior cerebral arteri es. JAMA 1966; 196 : 200-20 2 11 . Schn eider RC , Kriss FC, Falls HF. Prec hiasmal infarction as­ Fig. 5.-55-year-old woman with acute onset of blurred vision with bitem­ sociated with intrachiasmal and suprasell ar tumors. J Neuro­ poral hemianopia secondary to systemic lupus erythematosus (ICS type 4). surg 1970;2 : 19 7 - 208 A, Diffuse attenuation of carotid siphon just above level of anterior clinoid 12. Sheehan HL, Summers VK. Th e syndrome of hypopituitari sm. bilaterally. B, Small incidental aneurysm at trifurcation of middle cerebral artery bil aterally (arrow). No evidence of recent subarachnoid hemorrhage. Q J Med 1949;18:319- 378

j Fig. 6.- 25-year-old woman with chiasmatic visual defect due to Sheehan syndrome (ICS type 5). Sagittal (A) and coronal (B) reformatted images show ev­ idence of empty sella. Pituitary stalk (small arrows) enters sell a with intrasel­ lar hern iation of suprasellar cistern . Sell a is normal in size wi th sli ghtly rounded contour. Basilar artery (large arrow). B