(Stroke. 1995;26:1945-1949.)
© 1995 American Heart Association, Inc.
Articles |
Spontaneous Thrombosis of an Unruptured Anterior Communicating Artery Aneurysm
An Unusual Cause of Ischemic Stroke
From the Departments of Clinical Neurosciences (R.D.B., B.I.T., R.J.S., G.K., B.J.C.), Radiology (R.J.S.), Pathology (G.K., B.J.C.), and the Division of Neurosurgery (R.D.B., B.I.T.), University of Calgary, Foothills Hospital, Calgary, Alberta, Canada.
Correspondence to Richard D. Brownlee, MD, Division of Neurosurgery, 1206-3031 Hospital Drive NW, Calgary, Alberta, Canada T2N 4T8.
 |
Abstract |
|---|
 Top Abstract IntroductionCase ReportDiscussionReferences |
|---|
Background Stroke caused by spontaneous thrombosis of an unruptured intracranial aneurysm is a rare event.
Case Description A 66-year-old woman experienced a transient ischemic attack and cerebral infarctions due to spontaneous thrombosis of an unruptured anterior communicating artery aneurysm. Extension of thrombus into both anterior cerebral arteries and the left middle cerebral artery, resulting in ischemic infarction in all three vascular territories, was diagnosed by CT scanning, MRI, and cerebral angiography and confirmed at autopsy.
Conclusions This case illustrates a rare complication of an unruptured saccular aneurysm with neuroimaging and pathological correlation. Morphological and hemodynamic factors that may have precipitated aneurysm thrombosis are discussed with reference to experimental models.
Key Words: aneurysm • cerebral ischemia, transient • pathology • thrombosis
|
Introduction |
|---|
|
TopAbstractIntroductionCase ReportDiscussionReferences |
|---|
Cerebral aneurysms carry a high risk of morbidity and mortality. This most commonly results from subarachnoid hemorrhage due to aneurysm rupture. We present a rare case of transient ischemic attack (TIA) and ischemic stroke resulting in death due to spontaneous thrombosis of an unruptured anterior communicating artery aneurysm.
Review of the literature suggests that complete thrombosis of intracranial aneurysms is uncommon. It most frequently occurs after subarachnoid hemorrhage and in fusiform or giant saccular aneurysms. In autopsy series thrombosis of intracranial aneurysms has been found in 9% to 13% of cases.1 2 3 4 Aneurysm thrombosis after subarachnoid hemorrhage3 4 5 6 7 8 9 10 has a reported incidence of 1% to 2%.4 5 This may be as high as 3% in patients treated with antifibrinolytic agents4 or may be a delayed event after subarachnoid hemorrhage.3 Spontaneous thrombosis of giant intracranial aneurysms11 12 13 14 15 16 17 may be evident in up to 55% of lesions demonstrated on CT scans.11 Thrombosis is usually partial, with complete thrombosis occurring in 13% to 20% of cases.18 19 20 Parent or distal artery occlusion has been reported in association with aneurysm thrombosis after subarachnoid hemorrhage,13 14 during treatment with antifibrinolytic agents,4 21 after endovascular treatment,22 and in patients with unruptured giant cerebral aneurysms.14 15 16 17 19 Unruptured, partially thrombosed aneurysms may serve as a source of emboli leading to TIAs11 23 24 25 or cerebral infarction.13 14 15 26 27
We present a case in which a TIA was followed by strokes that progressively involved several vascular territories due to thrombosis of a large, unruptured anterior communicating artery aneurysm. This rare complication of a cerebral aneurysm is supported by neuroimaging and pathological correlation. Pathogenetic mechanisms for aneurysm thrombosis are discussed with reference to experimental models.
|
Case Report |
|---|
|
TopAbstractIntroductionCase ReportDiscussionReferences |
|---|
A 66-year-old female patient was admitted to a local hospital with acute onset of left hemiparesis. Approximately 2 weeks before admission the patient experienced a presyncopal episode with bilateral leg weakness that was transient and resolved spontaneously. The patient did not seek medical attention at that time.
On the day of admission the patient awoke in normal health. Shortly thereafter she developed an acute left hemiparesis and inability to walk. She experienced no headache and no alteration in her level of consciousness. At the time of admission, the patient was alert and oriented, appeared dehydrated, and had a left hemiparesis. The remainder of her neurological and general physical examination was normal. Laboratory investigations revealed a creatinine level of 160 µmol/L and a mild metabolic acidosis associated with her documented history of chronic renal failure. The white blood cell count was mildly elevated at 12.0x109/L, and her coagulation profile was abnormal with an elevated partial thromboplastin time of 37.1 seconds (control, 29.0 seconds) and international normalized ratio of 1.59.
During the 48 hours after admission the patient exhibited a progressive
deterioration in her level of consciousness. She became drowsy, opened
her eyes to voice, occasionally verbalized to painful stimulation, and
withdrew only her right arm and leg to pain. A head CT scan (Fig 1
) revealed a hyperdense lesion in the region of the
anterior communicating artery and cerebral infarction in the right
anterior cerebral artery (ACA) territory but no evidence of
subarachnoid hemorrhage. The patient was transferred
for neurosurgical consultation.
|
An MR scan was performed on the day of transfer (Fig 2)
and revealed a thrombosed anterior communicating artery
aneurysm, absent signal void in the right ACA, and areas of
cortical ischemia in the right ACA territory. A cerebral
angiogram performed the following day (Fig 3) showed
occlusion of both ACAs and no opacification of the thrombosed
aneurysm. The patient's condition deteriorated, and a repeated
CT scan performed on the fifth day after admission (Fig 4) showed evidence of infarction in both ACAs and the
left middle cerebral artery territories. In view of her poor clinical
status and extensive cerebral infarcts, aggressive care was
discontinued. The patient died 7 days after admission to the
hospital.
|
|
|
Autopsy Findings
Gross examination of the brain in the fresh state revealed an
intact 2.3x1.3-cm-diameter anterior communicating artery
aneurysm (Fig 5) with no evidence of recent or
remote subarachnoid hemorrhage. Thrombus filled the
aneurysm (Fig 6), the right A1, and both A2
segments of the ACAs. The left A1 segment was hypoplastic and contained
no clot. Cortical infarcts were evident in the territories of both ACAs
and the left middle cerebral artery.
|
|
Histological examination of the aneurysm after
fixation revealed a dome with an internal diameter of 17x11 mm, which
was filled with recent thrombus (Fig 7). The orifice of
the aneurysm was 1.5 mm in diameter, and the dome of the
aneurysm arose from the parent vessel with a neck 1.6 mm long
(Fig 8). The dome of the aneurysm exhibited the
characteristic absence of an elastic lamina and deficiency of the
tunica media28 with no atherosclerotic changes or
calcification. No site of aneurysm rupture was identified, and
there was no evidence of iron pigment in the
leptomeninges or on the external surface of the
aneurysm. The right A1 segment and both A2 segments of the ACA
were also filled with recent thrombus. Microscopic examination of the
cortical infarcts showed emboli within small subarachnoid
arteries adjacent to large areas of dead eosinophilic neurons.
|
|
The general autopsy revealed evidence of emphysema, chronic pancreatitis, and chronic renal failure. A right lower lobe pneumonia with abscess formation was identified and believed to be the ultimate cause of death. An incidental mucinous adenocarcinoma of the pancreas was also identified. Examination of the heart and carotid arteries revealed no source of cerebral emboli, and no embolic infarcts were identified elsewhere in the body.
|
Discussion |
|---|
|
TopAbstractIntroductionCase ReportDiscussionReferences |
|---|
While rupture is a common complication of intracranial aneurysms, spontaneous thrombosis of unruptured aneurysms is uncommon, and its pathogenic mechanisms are unknown. Factors associated with aneurysm thrombosis after subarachnoid hemorrhage may include hypotension, vasospasm, and local damage to the arterial wall.2 3 9 In our patient there was no history or evidence of subarachnoid hemorrhage, and no hypotensive episodes were observed. Thrombosis of unruptured aneurysms has been associated with calcification within the atherosclerotic wall of giant saccular1 10 11 and fusiform27 aneurysms. The aneurysm in this case revealed typical microscopic features of a saccular aneurysm with loss of elastic lamina and degeneration of the muscular media28 but no evidence of atherosclerosis or calcification.
The aneurysm in our patient measured 2.3x1.3 cm in the fresh postmortem state. Although thrombus filled the lumen and may have limited shrinkage artifact, the aneurysm still could have been larger than 2.5 cm in vivo and would therefore be classified as a giant aneurysm. Since most previous reports of aneurysm thrombosis also involved large to giant-sized aneurysms,11 12 13 14 15 16 17 18 19 20 24 25 size may be an important factor in precipitating thrombosis of unruptured aneurysms. In an experimental animal model of aneurysms, Black and German29 suggested that a ratio of chamber volume (in cubic millimeters) to orifice area (in square millimeters) of greater than 28:1 was associated with aneurysm thrombosis. In our patient we found a chamber volume of 1615.56 mm3 and an orifice area of 1.77 mm2 for a ratio of 912.75, which is well above the ratio associated with aneurysm thrombosis. In a different model, Roach30 suggested that aneurysms with a length (height) greater than 4 times the tube diameter at the orifice thrombosed, while those 2 to 2.5 times the tube diameter ruptured. The aneurysm in our patient had an elliptical shape 17 mm long and 11 mm wide (internal dimensions), with an orifice diameter of 1.5 mm. The length was therefore 11 times the tube diameter at the orifice and would be predicted to thrombose. An autopsy series suggested that aneurysms may be 30% to 60% smaller postmortem than in their in vivo state.31 Although this may have confounded our comparison with the experimental models, the presence of thrombus within the aneurysm and associated vessels may have minimized shrinkage. In addition, the aneurysm dome and neck should have experienced a similar degree of shrinkage. Therefore, we believe that the experimental models can be extrapolated to the aneurysm in our patient.
Experimental models have also shown that flow in large aneurysms is complicated by blood stagnation, increased blood viscosity, and slow flow that may lead to aneurysm thrombosis,32 which has been reported in large or giant saccular aneurysms.11 12 13 14 15 16 17 18 19 20 24 25 Aneurysms with a small orifice experience lower flow velocity, different flow direction, and smaller shear forces than those with a large orifice.32 In our patient the aneurysm dome was large (ID, 17x11 mm) and the orifice was small (1.45 mm), both of which could produce a low-flow state and promote thrombosis. Platelet deposition in giant aneurysms33 and turbulent blood flow in saccular aneurysms28 have been demonstrated in humans. Endothelial injury due to turbulent blood flow facilitates platelet deposition, platelet aggregation, and thrombus formation.33 34 Therefore, a number of factors probably interacted to cause thrombosis of the large, unruptured aneurysm in our patient.
Location may also be important as a risk factor for TIAs or stroke from thrombosed saccular aneurysms. The most commonly reported sites are the ICA11 13 14 15 23 and middle cerebral artery.14 23 24 Thrombosis of fusiform aneurysms of the basilar,27 posterior cerebral,26 and cavernous carotid14 arteries has also been reported to cause TIAs or strokes. Similar events from an unruptured anterior communicating artery aneurysm, as in our patient, have not previously been reported.
Medical factors that may have contributed to aneurysm thrombosis in our patient include the presence of an occult malignancy35 and dehydration. These factors could have induced a setting of decreased blood flow and increased coagulability,35 which may have precipitated aneurysm thrombosis and extension of thrombus into adjacent vessels, resulting in ischemic stroke. Thrombosis of the aneurysm occurred despite an elevated partial thromboplastin time and international normalized ratio, which was thought to be related to alcoholic liver disease. At autopsy hepatic steatosis but no sclerosis was identified.
Although both TIAs and strokes may result from thrombosis of unruptured intracranial aneurysms, our patient is unusual in the progression of her symptoms from a single TIA to cerebral infarctions involving several vascular territories. Stroke resulting from spontaneous thrombosis of unruptured intracranial aneurysms is rare, occurring most often in giant11 13 14 15 and fusiform26 27 aneurysms. In our patient with thrombosis of a large, unruptured anterior communicating artery aneurysm, CT and MRI suggested the diagnosis, which was confirmed at autopsy. Cerebral angiography demonstrated occlusion of adjacent vessels, which was due to thrombus extending from the aneurysm into the dominant right A1 and both A2 segments of the ACA. The hypoplastic left A1 contained no clot at autopsy, possibly as a result of lysis or embolization. Pathological examination of the brain revealed emboli within small subarachnoid arteries adjacent to large cortical infarcts in the vascular distribution of both ACAs and the left middle cerebral artery.
The presyncopal episode associated with transient bilateral leg weakness that our patient experienced 2 weeks before admission probably represented an embolic TIA arising from her thrombosed aneurysm. TIAs resulting from partially thrombosed intracranial aneurysms are uncommon,14 23 24 25 although thromboembolism from clot-containing intracranial aneurysms has been reported to occur in 5% to 59% of cases.11 33 Therefore, patients with TIAs in whom no other source of emboli can be identified should be investigated with cerebral angiography,23 CT, or MRI to identify a thrombosed aneurysm as a potential source of emboli.
The optimal form of treatment for patients with a thrombosed cerebral aneurysm has not been well defined. TIAs resulting from these lesions have been treated medically with antiplatelet agents23 and surgically by aneurysm clipping14 23 24 with no apparent difference in outcome.23 However, it has been reported that intra-aneurysmal clot does not protect against aneurysm rupture11 and that TIAs may precede subarachnoid hemorrhage.23 36 Therefore, surgical treatment of thrombosed aneurysms may be the preferred treatment since it has been shown to alleviate TIAs14 23 24 and would reduce the risk of subarachnoid hemorrhage.
In summary, this case represents a rare but important complication of intracranial aneurysms. Imaging and pathological correlation provide further evidence that unruptured saccular aneurysms may thrombose and give rise to TIAs and stroke. The pathophysiology of aneurysm thrombosis is discussed in relation to animal models, although the exact cause in our patient could not be identified.
Received February 20, 1995; revision received May 3, 1995; accepted May 31, 1995.
|
References |
|---|
|
TopAbstractIntroductionCase ReportDiscussionReferences |
|---|
1. Housepian EM, Pool JL. A systematic analysis of intracranial aneurysms from the autopsy file to the Presbyterian Hospital 1914-1956. J Neuropathol Exp Neurol. 1958;17:409-423. [Medline] [Order article via Infotrieve]
2.
Crompton MR. The pathogenesis of cerebral
infarction following the rupture of cerebral berry
aneurysms. Brain. 1964;87:263-279.
3. Hamilton MG, Dold ONR. Spontaneous disappearance of an intracranial aneurysm after subarachnoid hemorrhage. Can J Neurol Sci. 1992;19:389-391. [Medline] [Order article via Infotrieve]
4. Fodstad H, Liliequist B. Spontaneous thrombosis of ruptured intracranial aneurysms during treatment with tranexamic acid. Acta Neurochir (Wien). 1979;49:129-144. [Medline] [Order article via Infotrieve]
5. Edner G, Forster DMC, Steiner L, Bergvall U. Spontaneous healing of intracranial aneurysms after subarachnoid hemorrhage: case report. J Neurosurg. 1978;48:450-454. [Medline] [Order article via Infotrieve]
6.
Lodin H. Spontaneous thrombosis of cerebral
aneurysms: case report. Br J Radiol. 1966;39:701-703.
7. Davila S, Oliver B, Molet J, Bartumeus F. Spontaneous thrombosis of intracranial aneurysm. Surg Neurol. 1984;22:29-32. [Medline] [Order article via Infotrieve]
8. Spallone A, Peresedov VV, Kandel EI. Spontaneous cure of ruptured intracranial arterial aneurysms. Surg Neurol. 1981;16:367-370. [Medline] [Order article via Infotrieve]
9. Lin JP. Thrombosis of aneurysm of anterior communicating artery: case report. Acta Radiol (Diagn). 1969;8:74-80.
10. Schunk H. Spontaneous thrombosis of intracranial aneurysms. Am J Roentgenol. 1964;91:1327-1338.
11.
Whittle IR, Dorsch NW, Besser M. Spontaneous
thrombosis in giant intracranial aneurysms.
J Neurol Neurosurg Psychiatry. 1982;45:1040-1047.
12.
Carlson DH, Thomson D. Spontaneous thrombosis of
a giant cerebral aneurysm in five days: case report.
Neurology. 1976;26:334-336.
13. Antunes JL, Correll JW. Cerebral emboli from intracranial aneurysms. Surg Neurol. 1976;6:7-10. [Medline] [Order article via Infotrieve]
14. Sakaki T, Kinugawa K, Tanigake T, Miyamoto S, Kyoi K, Utsumi S. Embolism from intracranial aneurysms. J Neurosurg. 1980;53:300-304. [Medline] [Order article via Infotrieve]
15.
Sato K, Fujiwara S, Yoshimoto T, Onuma T. Two
cases of spontaneous internal carotid artery occlusion due to giant
intracranial carotid artery aneurysm.
Stroke. 1990;21:1506-1509.
16. Scott RM, Ballantine HT Jr. Spontaneous thrombosis in a giant middle cerebral artery aneurysm: case report. J Neurosurg. 1972;37:361-363. [Medline] [Order article via Infotrieve]
17. Whittle IR, Williams DB, Halmagyi GM, Besser M. Spontaneous thrombosis of a giant intracranial aneurysm and ipsilateral internal carotid artery. J Neurosurg. 1982;56:287-289. [Medline] [Order article via Infotrieve]
18. Golding R, Peatfield RC, Shawdon HH, Rice E. Computer tomographic features of giant intracranial aneurysms. Clin Radiol. 1980;31:41-48. [Medline] [Order article via Infotrieve]
19. O'Neill M, Hope T, Thomson G. Giant intracranial aneurysms: diagnosis with special reference to computerised tomography. Clin Radiol. 1980;31:27-39. [Medline] [Order article via Infotrieve]
20. Schubiger O, Valavanis A, Hayek J. Computed tomography in cerebral aneurysms with special emphasis on giant intracranial aneurysms. J Comput Assist Tomogr. 1980;4:24-32. [Medline] [Order article via Infotrieve]
21. Scott RM, Garrido E. Spontaneous thrombosis of an intracranial aneurysm during treatment with epsilon aminocaproic acid. Surg Neurol. 1977;7:21-23. [Medline] [Order article via Infotrieve]
22. Graves VB, Strother CM, Partington CR, Rappe A. Flow dynamics of lateral carotid artery aneurysms and their effects on coils and balloons: an experimental study in dogs. AJNR Am J Neuroradiol. 1992;13:189-196. [Abstract]
23. Fisher M, Davidson RI, Marcus EM. Transient focal cerebral ischemia as a presenting manifestation of unruptured cerebral aneurysms. Ann Neurol. 1980;8:367-372. [Medline] [Order article via Infotrieve]
24. Fukuoka S, Suematsu K, Nakamura J, Matsuzaki T, Satoh S, Hashimoto I. Transient ischemic attacks caused by unruptured intracranial aneurysms. Surg Neurol. 1982;17:464-467. [Medline] [Order article via Infotrieve]
25. Hoffman WF, Wilson CB, Townsend JJ. Recurrent transient ischemic attacks secondary to an embolizing saccular middle cerebral artery aneurysm. J Neurosurg. 1979;51:103-106. [Medline] [Order article via Infotrieve]
26. Atkinson JLD, Lane JI, Colvassani HJ, Llewellyn DME. Spontaneous thrombosis of posterior cerebral artery aneurysm with angiographic reappearance. J Neurosurg. 1993;79:434-437. [Medline] [Order article via Infotrieve]
27. Watanabe T, Sato K, Yoshimoto T. Basilar artery occlusion caused by thrombosis of atherosclerotic fusiform aneurysm of the basilar artery. Stroke. 1994;25:1068-1070. [Abstract]
28. Ferguson GG. Turbulence in human intracranial saccular aneurysms. J Neurosurg. 1970;33:485-497. [Medline] [Order article via Infotrieve]
29. Black SPW, German WJ. Observations on the relationship between the volume and the size of the orifice of experimental aneurysms. J Neurosurg. 1960;17:984-990.
30.
Roach MR. A model study of why some intracranial
aneurysms thrombose but others rupture.
Stroke. 1978;9:583-587.
31. McCormick WF, Acosta-Rua GJ. The size of intracranial aneurysms: an autopsy study. J Neurosurg. 1970;33:422-427. [Medline] [Order article via Infotrieve]
32. Gonzalez CF, Cho YI, Ortega HV, Moret J. Intracranial aneurysms: flow analysis of their origin and progression. AJNR Am J Neuroradiol. 1992;13:181-188. [Abstract]
33. Sutherland GR, King ME, Peerless SJ, Vezina WC, Brown GW, Chamberlain MJ. Platelet interaction within giant intracranial aneurysms. J Neurosurg. 1982;56:53-61. [Medline] [Order article via Infotrieve]
34. Cotran RS, Kumar V, Robbins SL. Pathologic Basis of Disease. 4th ed. Philadelphia, Pa: WB Saunders Co; 1989:99-105.
35. Al-Mondhiry H. Tumor interaction with hemostasis: the rationale for use of platelet inhibitors and anticoagulants in treatment of cancer. Am J Hematol. 1984;16:193-202. [Medline] [Order article via Infotrieve]
36. Okawara S. Warning signs prior to rupture of an intracranial aneurysm. J Neurosurg. 1973;38:575-580.[Medline] [Order article via Infotrieve]
This article has been cited by other articles:
 |
|
 |
|
  Y.H. Ding, D. Dai, D.A. Lewis, M.A. Danielson, R. Kadirvel, H.J. Cloft, and D.F. Kallmes Long-Term Patency of Elastase-Induced Aneurysm Model in Rabbits AJNR Am. J. Neuroradiol., January 1, 2006; 27(1): 139 - 141. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
D. Hammoud, P. Gailloud, A. Olivi, and K. J. Murphy Acute Vasogenic Edema Induced by Thrombosis of a Giant Intracranial Aneurysm: A Cause of Pseudostroke after Therapeutic Occlusion of the Parent Vessel AJNR Am. J. Neuroradiol., June 1, 2003; 24(6): 1237 - 1239. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 T. Vogel, R. Verreault, J.-F. Turcotte, M. Kiesmann, and M. Berthel Review Article. Intracerebral Aneurysms: A Review With Special Attention to Geriatric Aspects J. Gerontol. A Biol. Sci. Med. Sci., June 1, 2003; 58(6): M520 - 524. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
F. Caramia, A. Santoro, P. Pantano, E. Passacantilli, G. Guidetti, A. Pierallini, L. M. Fantozzi, G. P. Cantore, and L. Bozzao Cerebral Hemodynamics on MR Perfusion Images before and after Bypass Surgery in Patients with Giant Intracranial Aneurysms AJNR Am. J. Neuroradiol., October 1, 2001; 22(9): 1704 - 1710. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
N. Saito, N. Hayashi, T. Okubo, K. Takai, H. Miyauchi, T. Sasaki, and T. Kirino Internal Carotid Artery Aneurysm Visualized during Successful Endovascular Treatment of Carotid Embolism AJNR Am. J. Neuroradiol., March 1, 2000; 21(3): 546 - 548. [Abstract] [Full Text]
|
|
| |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||