837

CT Cisternography of Dolichoectatic Arterial Compression of the Optic Chiasm David B. Hinshaw, Jr.,' Kenneth R. Jordan,2 Anton N. Hasso,' and Joseph R. Thompson '

Dolichoectasia of the distal internal carotid arteries and the proximal anterior cerebral arteries is a well recognized abnor­mality. The angiographic and computed tomographic (CT) findings have been described [1-8]. Arterial enlargement has been implicated in chiasmal and optic nerve syndromes [1, 3-9]. We report a symptomatic patient with chiasmal deform­ity and associated arterial dolichoectasia who was examined using high-resolution CT (GE CT/N 8800, ReView) with me­trizamide cisternography.

Case Report

A 19-year-old woman was referred for evaluation of episodic left­leg weakness and visual disturbances. At the age of 15 she began having recurrent episodes of transient visual blurring and, occasion­ally, blindness that lasted as long as 2 min. No medical attention was sought at that time. Her condition was then quiescent until age 17, when she began having episodes of transient left-leg weakness every 2-4 weeks. At age 18, she had a particularly severe occurrence without resolution . A contrast-enhanced CT scan obtained elsewhere showed marked gyriform enhancement in the distribution of the right anterior cerebral artery suggesting infarction. Cerebral angiography demonstrated marked ectasia of the intracranial parts of the internal carotid arteries and the proximal anterior cerebral arteries. The right anterior cerebral artery was occluded distal to the anterior commu­nicating artery. She was treated with Coumadin but had two more episodes of transient left-sided weakness before presenting at our institution. Her family history included diabetes mellitus but did not include migraine headaches.

On examination, the patient was normotensive. Visual acuity was profoundly impaired in the right eye with finger-counting ability at 10 cm only. Visual acuity on the left was 20/25. An afferent pupillary defect with advanced optic atrophy was present on the right. There was rapid slowing of alternating movements on the left with aWk­wardness of fine dexterity. The left knee jerk was hyperreflexic. There were no vascular bruits and the cardiac examination was normal.

Electroencephalography showed bifrontal , intermittent, rhythmic slow wave bursts , greater over the left hemisphere. The visual­evoked responses showed no reproducible response from the right eye; however, the p-100 for the left eye was 126 msec, which is significantly prolonged for our laboratory.

Repeat four-vessel cerebral angiography at our institution again

Received March 21 , 1984; accepted after revision July 27 , 1984.

revealed the severe dolichoectasia of the arteries at the base of the brain with occlusion of the right anterior cerebral artery (fig . 1). Coronal CT with intravenous iodine enhancement also revealed the tortuous and enlarged distal internal carotid , proximal middle, and proximal anterior cerebral arteries along with infarction in the cere­brum in the right anterior cerebral artery distribution (fig. 2). Com­pressive or ischemic injury to the optic chiasm caused by the enlarged anterior cerebral arteries was clinically suspected, prompting further examination using metrizamide CT cisternography . Using the usual technique for sterile lumbar puncture , 6 ml of 170 mg I/ml metrizamide was injected into the lumbar subarachnoid space. The patient was then placed in a head-down position and subsequently scanned in the axial and coronal planes using the 1.5-mm-slice-thickness mode of the GE CT /N 8800 scanner. This CT examination showed deformity and diminution of the optic chiasm (fig . 3).

Neurosurgical intervention was considered, but was believed to be risky and the outcome doubtful. The patient was maintained on medical hypotension using Propanolol and diuretics. She was also treated continuously with aspirin and Persantine. Her blood pressure remained stable at 90/60 mm Hg, and she had no recurrent visual symptoms during the subsequent 18 months.

Discussion

From 1942 to 1945 Le Riche [10-12] described "arteria magna et dolicho" as a process of severe dilatation and elongation of the major pelviC arteries. Other, similar contri­butions to the literature followed , until the development of angiography allowed better delineation of the process [13-15].

The angiographic findings have been described in several anatomic locations , including the brain [1 , 2, 13-16]. Typically , the involved arteries are elongated , tortuous, dilated, and slow-flowing. Patients often have symptoms of local mass effect or ischemia [1 , 2, 4, 5, 7-9 , 16-18]. These patients have an increased incidence of thrombosis , embolization , and associated aneurysms [14]. Intravenous-contrast-enhanced cranial CT scans have characteristically shown fusiformly dilated and elongated enhancing silhouettes , generally in the courses of the intracranial internal carotid or basilar arteries [1 , 2, 19, 20] .

1 Department of Radiation Sciences, Section of Neuroradiology, Loma Linda University School of Medicine, Loma Linda, CA 92350. Address reprint requests to D. B. Hinshaw, Jr.

2 Department of Medicine, Section of Neurology, Loma Linda University School of Medicine, Loma Linda, CA 92350.

AJNR 6:837-839, September/October 1985 0195-6108/85/0605-0837 $00.00 © American Roentgen Ray Society

838 HINSHAW ET AL. AJNR:6, Sept/Oct 1985

A B

Fig. 1.- Anteroposterior left (A) and right (B) cerebral arteriograms. Marked fusiform enlargement of distal internal carotid arteries and proximal anterior and middle cerebral arteries. Right anterior cerebral artery is occluded (arrow) . Arteries in midline are dorsal callosal collaterals supplied by posterior cerebral arteries.

Fig. 2.-lntravenous-contrast-enhanced coronal CT scan. Enlarged distal internal carotid artery bifur­cations (long prrows). Optic chiasm (short solid ar­row) visible, but shape is not clearly defined. Infarction of right cingulate cortex (open arrow).

A B c Fig. 3.- Metrizamide-enhanced axial (A and B) and coronal (C) CT cisternograms. Enlarged internal carotid (long arrows) and anterior cerebral (open arrows)

arteries outlined by metrizamide in subarachnoid space. Optic chiasm (short solid arrows) is small and deformed.

Pathologic examination of the arteries has revealed frag­mentation or complete loss of the medial elastic lamina [13 , 15]. The presence of atheromatous change has been variable but is usually evident [5 , 13]. Since even a 2-year-old patient has been reported with dolichoectatic arteries, the process is thought to have a congenital or acquired cause unrelated to atherosclerosis . It appears that the frequent presence of atherosclerosis probably is coincidental [5 , 21].

Several patients have been reported with visual symptoms

ascribed to compression or ischemia of the optic chiasm or nerves by enlarged internal carotid and/or proximal anterior cerebral arteries [1 , 4-6, 8, 9, 22, 23]. Pathologic examina­tions have shown deformity and atrophy of the optic chiasm and/or grooving of the optic nerve at the site of the entrance into the cranial end of the optic canal in cases of this type [3, 5].

The blood supply of the intracranial optic nerves and chiasm is known to originate predominantly from the distal internal

AJNR:6, Sept/Oct 1985 CHIASMAL DEFORMITY WITH ARTERIAL DOLICHOECTASIA 839

carotid artery, ophthalmic artery, proximal anterior cerebral arteries, and the anterior communicating artery via small branches. The hypophyseal, posterior communicating , ante­rior choroidal, and proximal middle cerebral arteries play a variable role [24].

The visual symptoms and type and degree of visual field defects appear to be highly variable, probably depending on the size, shape, and position of the dolichoectatic segments. Since atherosclerosis is often associated , it is probably im­possible to determine the degree of the symptomatology caused by direct-pressure atrophy as opposed to that caused by ischemia secondary to occlusion of small arterial supply branches.

The normal and pathologic CT appearance of the optic chiasm and suprasellar cistern using subarachnoid metriza­mide has been reported [25-27] . Our case demonstrates the appearance of carotid and anterior cerebral artery dolichoec­tasia using high-resolution CT with subarachnoid metriza­mide. Clearly, there has been a marked decrease in the size of the optic chiasm with deformity of its shape. Presumably, this has been caused by chronic pulsatile pressure atrophy. Even though thrombosis and embolization appear to be seen more often with dolichoectasia [14] , the pathogenesis for our patient's right anterior cerebral artery occlusion is not entirely clear. This certainly could have played a role in her chiasmatic symptoms.

Therapy for such a diffuse process can be very difficult. Some have argued that surgical manipulation of the dolichoec­tatic arteries can be beneficial [6]. Our patient was stabilized under conservative antihypertensive management.

REFERENCES

1. Goldstein SJ, Sacks JG, Lee C, Tibbs PA, McCready RA. Com-puted tomographic findings in cerebral arterial ectasia. AJNR 1983;4:501-504

2. Banna M, Romeo MA. Cerebral arterial ectasia on computed tomography. J Can Assoc Radio/1979;30:259-260

3. Walsh FB, Gass JD. Concerning the optic chiasm. Selected pathologic involvement and clinical problems. Am J Ophthalmol 1960;50 : 1 031-1 047

4 . Yu YL, Moseley IF, Pullicino P, McDonald WI. The clinical picture of ectasia of the intracerebral arteries . J Neurol Neurosurg Psy-chiatry 1982;45 :29-36

5. Sacks JG, Lindenburg R. Dolicho-ectatic intracranial arteries: symptomology and pathogenesis of arterial elongation and dis-tention . Johns Hopkins Med J 1969;125:95-106

6. Post KD, Gittinger JW Jr, Stein BM . Visual improvement after surgical manipulation of dolichoectatic anterior cerebral arteries.

Surg Neuro/1981 ;15 :321-324 7. Hildon GF, Hoyt WF. An arteriosclerotic chiasmal syndrome.

Bitemporal hemianopia associated with fusiform dilatation of the anterior cerebral arteries . JAMA 1966;196: 1 018-1 020

8. Mitts MG, McQueen JD. Visual loss associated with fusiform enlargement of the intracranial portion of the internal carotid artery. J Neurosurg 1965;23:33-37

9. Tassman IS. Foster Kennedy syndrome with fusiform aneurysm of internal carotid arteries . Arch Ophthalmol 1944;32: 125-127

10. LeRiche R. Pathological expansion of the arteries aside from aneurysm. Presse Med 1942;46: 17

11 . LeRiche R. Elongation and dilatation without obstruction of the primary iliac vein and artery simulating an aneurysm. Presse Med 1943;38: 554

12. LeRiche R. Pathological physiology and surgical treatment of arterial disorders. Paris: Masson, 1945 :283-287

13. Staple TW, Friedenberg MJ , Anderson MS, Butcher HR Jr. Arteria magna et dolicho of leriche. Acta Radiol [Diagn] (Stockh) 1966;4: 293-305

14. Carlson DH, Gryska P, Seletz J, Armstrong S. Arteriomegaly . AJR 1975;125 :553-558

15. Randall PA, Omar MM, Rohner R, Hedgcock M, Brenner RJ . Arteria magna revisited. Radiology 1979;132:295-300

16. Bingas B, Cotsou S. Cerebello-pontine angle-syndrome with uncommon aetiology [a case report] . Neuroradiology 1972;3: 165-166

17. Bladin PF, Donnan GF. Cerebral arterial ectasia. Clin Radiol 1963; 14: 349-352

18. Segal HD, McLaurin RL. Giant serpentine aneurysm. J Neurosurg 1977;46: 115-210

19. Scotti G, De Grandi C, Colombo A. Ectasia of the intracranial arteries diagnosed by computed tomography. Megadolichoba­silar artery: CT diagnosis. Neuroradiology 1978;15 : 183-184

20 . Peterson NT, Duchesneau PM, Westbrook EL, Weinstein MA.

21 .

22 .

23. 24.

25 .

26.

27 .

Basilar artery ectasia demonstrated by computed tomography . Radiology 1977;122:713-715 Thompson JR , Weinstein PR , Simmons CR. Cerebral arterial dolichoectasia with seizure. J Neurosurg 1976 ;44 :509-512 Lee FK, Schatz MJ. Ischemic chiasmal syndrome. Acta Radiol [Suppl] (Stockh) 1975;347:131-148 Lee FK. Ischemic chiasma syndrome. AJNR 1983;4 :777-780 Hughes B. Blood supply of the optic nerves and chiasma and its clinical significance. Br J Ophthalmo/1958;42 : 1 06-125 Kline LB, Vitek JJ, Acker JD. Computed tomography in the evaluation of the optic chiasm. Surv Ophthalmol 1983;27 :387-396 Drayer BP, Rosenbaum AE, Kennerdell JS, et al. Computed tomographic diagnosis of suprasellar masses by intrathecal en­hancement. Radiology 1977;123 :339-334 Ghoshhajra K. High resolution metrizamide CT cisternography in sellar and suprasellar abnormalities. J Neurosurg 1981 ;54 :232-239