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Intracranial Dissecting Aneurysm Causing Subarachnoid Hemorrhage: The Role of Computerized Tomographic Angiography and Magnetic Resonance Angiography
Vascular: Aneurysms
Intracranial Dissecting Aneurysm Causing Subarachnoid Hemorrhage: The Role of Computerized Tomographic Angiography and Magnetic Resonance Angiography Giuseppe Lanzino, M.D., George Kaptain, M.D., David F. Kallmes, M.D., James E. Dix, M.D., and Neal F. Kassell, M.D. Departments of Neurosurgery and Radiology, Virginia Neurological Institute, University of Virginia, Charlottesville, Virginia
Lanzino G, Kaptain G, Kallmes DF, Dix JE, Kassell NF. Intracranial dissecting aneurysm causing subarachnoid hemorrhage: the role of computerized tomographic angiography and magnetic resonance angiography. Surg Neurol 1997;48:477– 81. BACKGROUND
With increasing frequency, dissecting aneurysms of the intracranial arteries are recognized as a possible cause of subarachnoid hemorrhage (SAH). In the presence of a dissecting aneurysm, angiographic changes may be subtle at presentation and correct diagnosis often requires serial angiograms. We report a patient with a dissecting aneurysm of the anterior cerebral artery (ACA) causing SAH, in whom less invasive diagnostic tools, such as high-resolution computerized tomographic angiography (CTA) and magnetic resonance angiography (MRA), were helpful in confirming the diagnosis and in following the evolution of the dissection. CASE PRESENTATION
We present this 51-year old woman who experienced the sudden onset of severe headache without associated neurological deficits. Head CT showed SAH with blood in the interhemispheric fissure, suggesting a ruptured ACA aneurysm. Serial cerebral angiograms failed to demonstrate an aneurysmal sac, but showed evolving irregularities of the ACA consistent with a dissecting aneurysm. These findings were confirmed by CTA and MRA. The patient was treated conservatively and made an excellent recovery. A MRA obtained 2 months later showed slight improvement of the previously visualized ACA dilatation. CONCLUSION
Serial angiograms are often required to confirm the diagnosis and to follow the evolution of an intracranial dis-
Address correspondence to: Giuseppe Lanzino, M.D., Department of Neurosurgery, Box 212 University of Virginia HSC, Charlottesville, VA 22908. Received April 24, 1996; accepted January 27, 1997. © 1997 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
section. With recent advances in neuroradiological techniques, however, critical information can be obtained by less invasive imaging studies, such as CTA and MRA. © 1997 by Elsevier Science Inc. KEY WORDS
Anterior cerebral artery, computerized tomography angiography, dissecting aneurysm, magnetic resonance angiography, subarachnoid hemorrhage.
n 15–20% of patients with spontaneous subarachnoid hemorrhage (SAH), cerebral angiogram fails to detect the presence of a saccular aneurysm [7]. In some of these cases, the source of the hemorrhage is an occult aneurysm; however, other causes such as intracranial artery dissections, trauma, or mycotic aneurysms must be considered [14]. Most cases of SAH from intracranial dissecting aneurysms involve the posterior circulation [16]. Involvement of the anterior circulation is uncommon, and SAH from dissecting aneurysms of the anterior cerebral artery (ACA) is a rare occurrence. In the few reported cases of ACA dissecting aneurysms, the clinical presentation was often catastrophic, with diagnosis made only at autopsy [4,5,9,10]. In milder cases, these dissections pose significant diagnostic challenges. We describe a patient with SAH from a dissecting aneurysm of the ACA in which high-resolution computerized tomographic angiogram (CTA) and serial magnetic resonance angiogram (MRA) provided critical information for the correct management of this case.
I
0090-3019/97/$17.00 PII S0090-3019(97)00178-X
478 Surg Neurol 1997;48:477–81
Axial noncontrast CT scan at the level of the midbrain demonstrates acute SAH in the anterior hemispheric region (arrows).
1
Case History This 51-year-old woman with a past medical history consistent with migraine suffered the sudden onset of a severe occipito-frontal headache without any
(A) Oblique magnified digital substraction angiogram during left common carotid artery injection. There is mild fusiform dilatation of the proximal left A2 segment (arrowheads), but multiple projections failed to demonstrate a saccular aneurysm. (B) Digital substraction angiogram of the left common carotid artery is suggestive of fibromuscular dysplasia, with multiple concentric focal stenoses involving the internal carotid artery.
2
Lanzino et al
associated neurological deficit. A nonenhanced CT scan showed the presence of SAH with blood in the interhemispheric fissure, suggesting a ruptured ACA aneurysm (Figure 1). A cerebral angiogram performed on day 1 showed mild dilatation of the A2 segment of the left ACA (Figure 2 A), but multiple projections failed to demonstrate a patent aneurysm sac. Mild changes suggesting fibromuscular dysplasia were noted in the cervical carotid artery (Figure 2 B). A follow-up conventional angiogram was performed on day 8, showing little change in the dilated A2 segment. Again, no aneurysm sac was identified (Figure 3). A high-resolution CTA was performed 1 day after the second angiogram and effectively demonstrated the dilated A2 segment of the left ACA (Figure 4). An MRA, done on day 19, also demonstrated the change in the left A2 segment (Figure 5). Since conventional angiograms as well as the CTA and MRA suggested the diagnosis of dissecting aneurysm, we elected to follow the patient without any intervention. On day 24, a third angiogram was performed. It demonstrated minimal improvement in the dilated segment, and confirmed that an aneurysm sac was not present (Figure 6). The patient made an excellent recovery and returned for further follow up 2 months after the hemorrhage. An additional MRA was performed at this time, which demonstrated slight improvement of the A2 segment dilatation (Figure 7).
CTA and MRA of ACA Dissecting Aneurysm
Surg Neurol 479 1997;48:477–81
MRA performed on day 19 showed a dilated A2 segment similar to that demonstrated using both conventional and CT angiography.
5
Digital substraction angiogram (oblique view) performed on Day 8 demonstrates persistent fusiform dilatation of the left proximal A2 segment.
3
Discussion
of the middle cerebral artery found during the autopsy of a patient with acute syphilitic arteritis [18]. Until recently, these lesions were considered rare, and only 10 pathologically verified cases were reported before 1960 [19]. During the past three decades, an increasing number of cases have been
Intracranial dissecting aneurysms have been known to cause hemorrhage since 1915, when Turnbull reported hemorrhage from a dissecting aneurysm
Spiral CTA performed on day 8. Shaded surface reconstruction in the same orientation as the conventional angiogram shown in Figure 3. Dilated left A2 segment is well demonstrated (arrow). Note callosal marginal branch originating just distal to the dilated segment, seen both on conventional and CTA (arrowhead). The distal pericallosal artery is also identified (open arrows).
4
Digital substraction angiogram performed on Day 24 shows interval slight improvement in fusiform dilatation of the left A2 segment (arrow).
6
480 Surg Neurol 1997;48:477–81
7
Follow-up MRA on day 60 shows slight improvement in fusiform dilatation (arrow).
recognized as patients with ischemic or hemorrhagic stroke are more thoroughly evaluated. Thus, these lesions are not as rare as once believed. The dissection of intracranial vessels usually occurs between the internal elastic lamina and the tunica media [19]. In the case of intracranial dissecting aneurysms that present with SAH, however, the dissection plane extends transmurally from the lumen through the tunica intima and media to the adventitia [3,5,19]. Only 14% of all intracranial dissections that cause hemorrhage involve the anterior circulation [15]. This difference strongly suggests that local anatomic factors can have a role in determining the transmural extent of the dissection. Spontaneous dissections of the ACA are unusual [1,4,6,8 –13,15,17]. In the cases reported to date, the presenting symptoms most often included sudden onset of headache followed by ischemic neurological deficits. Presentation with SAH was less common, and when it occurred, the outcome was often catastrophic [4,5,9,10]. Definitive diagnosis of intracranial dissecting aneurysms is often difficult in the absence of pathological confirmation. As such, dissecting aneurysms of intracranial arteries may occur with a greater frequency than the literature suggests. Some patients with mild symptoms, in fact, may not seek medical attention. In addition, some cases of dissection that cause SAH are likely to go unrecognized due to the difficulty of making the correct angiographic diagnosis, and such patients are con-
Lanzino et al
sidered to have suffered an SAH of unknown etiology. Several angiographic findings such as the “string sign,” “pearl reaction,” and “rosette sign” are considered characteristics of dissecting aneurysms. Fusiform dilatation may also occur. Demonstrating a double channel showing both true and false lumen is considered most important and specific to the dissecting aneurysm, but it has been demonstrated only on rare occasions [16]. Segmental narrowing can be present, and can be misdiagnosed as vasospasm in the presence of SAH [19]. Serial angiography is often required to show the evolution of the lesion [1,9], and several months may be required to show complete angiographic resolution. Angiography, however, is an invasive procedure, and the yield of repeat angiography must be weighed against the risks of the procedure. Serial image studies with less invasive tools, such as MRA and CTA, should be considered. Conventional angiography may be obtained only when these studies suggest resolution of the pathological changes. In addition, MRA and CTA can be used as adjuncts to conventional angiography to support the diagnosis of intracranial dissection. In our patient, the combination of high-resolution angiography, CTA, and MRA helped us to characterize the lesion and guide our management. In addition, MRA was shown to be useful in following the evolution of the dissection. The difficulty in the diagnosis of dissecting intracranial aneurysms obscures an assessment of the natural history of the disorder. Current therapeutic guidelines vary according to the location of the aneurysm and extent of the pathology. Patients whose dissections are limited to the intima and internal elastic lamina usually present with symptoms of ischemia and are treated conservatively or with anticoagulants [8]. Others warn against the possibility of hemorrhage caused by anticoagulants in this patient population [19] and recommend a consideration of early revascularization procedures [19]. Individuals whose aneurysms involve the entire thickness of the vessel wall present with intracranial hemorrhage and may require surgical ligation or bypass [19]. Rebleeding rates for dissecting aneurysms of the posterior fossa have been reported to be as high as 30%, and some authors use this information as an indication for hunterian ligation or bypass procedures [2]. Some lesions, however, spontaneously resolve or stabilize with nonoperative therapy [8,15]. The authors wish to acknowledge Desiree J. Lanzino and Sarah B. Hudson, who edited the manuscript.
CTA and MRA of ACA Dissecting Aneurysm
Surg Neurol 481 1997;48:477–81
REFERENCES 1. Amagasa M, Sato S, Otabe K. Posttraumatic dissecting aneurysm of the anterior cerebral artery: case report. Neurosurgery 1988;23:221–5. 2. Aoki N, Sakai T. Rebleeding from intracranial dissecting aneurysm in the vertebral artery. Stroke 1990;21: 1628 –31. 3. Farrell MA, Gilbert JJ, Kaufmann JCE. Fatal intracranial arterial dissection: clinical pathological correlation. J Neurol Neurosurg Psychiatry 1985;48:111–21. 4. Gherardi JC, Lee HY. Localized dissecting hemorrhage and arteritis, renal and cerebral manifestations. JAMA 1967;199:187– 8. 5. Guridi J, Gallego J, Monzon F, Aguilera F. Intracerebral hemorrhage caused by transmural dissection of the anterior cerebral artery. Stroke 1993;24:1400 –2. 6. Ishikawa R, Sunagawa S, Itoh I, Iwashita K. An experience of dissecting cerebral aneurysm of the anterior cerebral artery. No Shinkei Geka 1993;21:355–9. 7. Kassell NF, Torner JC, Jane JA, Haley EC Jr, Adams HP. The international cooperative study on the timing of aneurysm surgery. II. Surgical results. J Neurosurg 1990;73:37– 47. 8. Kidooka M, Okada T, Sonobe M, Nakazawa T, Handa J. Dissecting aneurysm of the anterior cerebral artery: report of two cases. Surg Neurol 1993;39:53–7. 9. Manz HJ, Luessenhop AJ. Dissecting aneurysm of intracranial vertebral artery: case report and review of literature. J Neurol 1983;230:25–35. 10. Manz HJ, Vester J, Lavenstein B. Dissecting aneurysm
11.
12. 13. 14. 15. 16.
17. 18. 19.
of the cerebral arteries in childhood and adolescence. Virchows Arch Path Anat Histol 1979;384:325– 35. Nakazawa T, Saito A, Watanabe K, Matsuda M, Handa J. Dissecting aneurysm of the anterior cerebral artery: report of a case. No Shinkei Geka 1984;12:1211–16. Nelson JW, Styri O. Dissecting subintimal hematomas of the intracranial arteries: report of a case. J Am Osteopathol Assoc 1968;67:512–7. Pilz P. Dissezierendes aneurysma der arteria cerebri anterior und Guillain-Barre-syndrom in der schwangerschaft. J Neurol 1968;214:295–9. Rinkel GJE, van Gijn J, Wijdicks EFM. Subarachnoid hemorrhage without detectable aneurysm. A review of the causes. Stroke 1993;24:1403–9. Sasaki O, Koike T, Takeuchi S, Tanaka R. Serial angiography in a spontaneous dissecting anterior cerebral artery aneurysm. Surg Neurol 1991;36:49 –53. Tanaka K, Waga S, Kojima T, Shimizu T, Niwa S. Nontraumatic dissecting aneurysms of the intracranial vertebral artery: report of six cases. Acta Neurochir (Wien) 1989;100:62– 6. Teari S, Matsubara T. A case of dissecting anuerysm involving solely anterior cerebral artery. Jpn J Stroke 1991;13:159 – 64. Turnbull HM. Alterations in arterial structure, and their relationship to syphilis. Q J Med 1915;8:201–54. Yonas H, Agamanolis D, Takaoka Y, White RJ. Dissecting intracranial aneurysms. Surg Neurol 1977;8:407– 15.
f our economy of freedom fails to distribute wealth as ably as it has created it, the road to dictatorship will be open to any man who can persuasively promise security to all; and a martial government, under whatever charming phases, will engulf the democratic world.
I
—Will and Ariel Durant “The Lessons of History” (1968)
Intracranial Dissecting Aneurysm Causing Subarachnoid Hemorrhage: The Role of Computerized Tomographic Angiography and Magnetic Resonance Angiography Giuseppe Lanzino, M.D., George Kaptain, M.D., David F. Kallmes, M.D., James E. Dix, M.D., and Neal F. Kassell, M.D. Departments of Neurosurgery and Radiology, Virginia Neurological Institute, University of Virginia, Charlottesville, Virginia
Lanzino G, Kaptain G, Kallmes DF, Dix JE, Kassell NF. Intracranial dissecting aneurysm causing subarachnoid hemorrhage: the role of computerized tomographic angiography and magnetic resonance angiography. Surg Neurol 1997;48:477– 81. BACKGROUND
With increasing frequency, dissecting aneurysms of the intracranial arteries are recognized as a possible cause of subarachnoid hemorrhage (SAH). In the presence of a dissecting aneurysm, angiographic changes may be subtle at presentation and correct diagnosis often requires serial angiograms. We report a patient with a dissecting aneurysm of the anterior cerebral artery (ACA) causing SAH, in whom less invasive diagnostic tools, such as high-resolution computerized tomographic angiography (CTA) and magnetic resonance angiography (MRA), were helpful in confirming the diagnosis and in following the evolution of the dissection. CASE PRESENTATION
We present this 51-year old woman who experienced the sudden onset of severe headache without associated neurological deficits. Head CT showed SAH with blood in the interhemispheric fissure, suggesting a ruptured ACA aneurysm. Serial cerebral angiograms failed to demonstrate an aneurysmal sac, but showed evolving irregularities of the ACA consistent with a dissecting aneurysm. These findings were confirmed by CTA and MRA. The patient was treated conservatively and made an excellent recovery. A MRA obtained 2 months later showed slight improvement of the previously visualized ACA dilatation. CONCLUSION
Serial angiograms are often required to confirm the diagnosis and to follow the evolution of an intracranial dis-
Address correspondence to: Giuseppe Lanzino, M.D., Department of Neurosurgery, Box 212 University of Virginia HSC, Charlottesville, VA 22908. Received April 24, 1996; accepted January 27, 1997. © 1997 by Elsevier Science Inc. 655 Avenue of the Americas, New York, NY 10010
section. With recent advances in neuroradiological techniques, however, critical information can be obtained by less invasive imaging studies, such as CTA and MRA. © 1997 by Elsevier Science Inc. KEY WORDS
Anterior cerebral artery, computerized tomography angiography, dissecting aneurysm, magnetic resonance angiography, subarachnoid hemorrhage.
n 15–20% of patients with spontaneous subarachnoid hemorrhage (SAH), cerebral angiogram fails to detect the presence of a saccular aneurysm [7]. In some of these cases, the source of the hemorrhage is an occult aneurysm; however, other causes such as intracranial artery dissections, trauma, or mycotic aneurysms must be considered [14]. Most cases of SAH from intracranial dissecting aneurysms involve the posterior circulation [16]. Involvement of the anterior circulation is uncommon, and SAH from dissecting aneurysms of the anterior cerebral artery (ACA) is a rare occurrence. In the few reported cases of ACA dissecting aneurysms, the clinical presentation was often catastrophic, with diagnosis made only at autopsy [4,5,9,10]. In milder cases, these dissections pose significant diagnostic challenges. We describe a patient with SAH from a dissecting aneurysm of the ACA in which high-resolution computerized tomographic angiogram (CTA) and serial magnetic resonance angiogram (MRA) provided critical information for the correct management of this case.
I
0090-3019/97/$17.00 PII S0090-3019(97)00178-X
478 Surg Neurol 1997;48:477–81
Axial noncontrast CT scan at the level of the midbrain demonstrates acute SAH in the anterior hemispheric region (arrows).
1
Case History This 51-year-old woman with a past medical history consistent with migraine suffered the sudden onset of a severe occipito-frontal headache without any
(A) Oblique magnified digital substraction angiogram during left common carotid artery injection. There is mild fusiform dilatation of the proximal left A2 segment (arrowheads), but multiple projections failed to demonstrate a saccular aneurysm. (B) Digital substraction angiogram of the left common carotid artery is suggestive of fibromuscular dysplasia, with multiple concentric focal stenoses involving the internal carotid artery.
2
Lanzino et al
associated neurological deficit. A nonenhanced CT scan showed the presence of SAH with blood in the interhemispheric fissure, suggesting a ruptured ACA aneurysm (Figure 1). A cerebral angiogram performed on day 1 showed mild dilatation of the A2 segment of the left ACA (Figure 2 A), but multiple projections failed to demonstrate a patent aneurysm sac. Mild changes suggesting fibromuscular dysplasia were noted in the cervical carotid artery (Figure 2 B). A follow-up conventional angiogram was performed on day 8, showing little change in the dilated A2 segment. Again, no aneurysm sac was identified (Figure 3). A high-resolution CTA was performed 1 day after the second angiogram and effectively demonstrated the dilated A2 segment of the left ACA (Figure 4). An MRA, done on day 19, also demonstrated the change in the left A2 segment (Figure 5). Since conventional angiograms as well as the CTA and MRA suggested the diagnosis of dissecting aneurysm, we elected to follow the patient without any intervention. On day 24, a third angiogram was performed. It demonstrated minimal improvement in the dilated segment, and confirmed that an aneurysm sac was not present (Figure 6). The patient made an excellent recovery and returned for further follow up 2 months after the hemorrhage. An additional MRA was performed at this time, which demonstrated slight improvement of the A2 segment dilatation (Figure 7).
CTA and MRA of ACA Dissecting Aneurysm
Surg Neurol 479 1997;48:477–81
MRA performed on day 19 showed a dilated A2 segment similar to that demonstrated using both conventional and CT angiography.
5
Digital substraction angiogram (oblique view) performed on Day 8 demonstrates persistent fusiform dilatation of the left proximal A2 segment.
3
Discussion
of the middle cerebral artery found during the autopsy of a patient with acute syphilitic arteritis [18]. Until recently, these lesions were considered rare, and only 10 pathologically verified cases were reported before 1960 [19]. During the past three decades, an increasing number of cases have been
Intracranial dissecting aneurysms have been known to cause hemorrhage since 1915, when Turnbull reported hemorrhage from a dissecting aneurysm
Spiral CTA performed on day 8. Shaded surface reconstruction in the same orientation as the conventional angiogram shown in Figure 3. Dilated left A2 segment is well demonstrated (arrow). Note callosal marginal branch originating just distal to the dilated segment, seen both on conventional and CTA (arrowhead). The distal pericallosal artery is also identified (open arrows).
4
Digital substraction angiogram performed on Day 24 shows interval slight improvement in fusiform dilatation of the left A2 segment (arrow).
6
480 Surg Neurol 1997;48:477–81
7
Follow-up MRA on day 60 shows slight improvement in fusiform dilatation (arrow).
recognized as patients with ischemic or hemorrhagic stroke are more thoroughly evaluated. Thus, these lesions are not as rare as once believed. The dissection of intracranial vessels usually occurs between the internal elastic lamina and the tunica media [19]. In the case of intracranial dissecting aneurysms that present with SAH, however, the dissection plane extends transmurally from the lumen through the tunica intima and media to the adventitia [3,5,19]. Only 14% of all intracranial dissections that cause hemorrhage involve the anterior circulation [15]. This difference strongly suggests that local anatomic factors can have a role in determining the transmural extent of the dissection. Spontaneous dissections of the ACA are unusual [1,4,6,8 –13,15,17]. In the cases reported to date, the presenting symptoms most often included sudden onset of headache followed by ischemic neurological deficits. Presentation with SAH was less common, and when it occurred, the outcome was often catastrophic [4,5,9,10]. Definitive diagnosis of intracranial dissecting aneurysms is often difficult in the absence of pathological confirmation. As such, dissecting aneurysms of intracranial arteries may occur with a greater frequency than the literature suggests. Some patients with mild symptoms, in fact, may not seek medical attention. In addition, some cases of dissection that cause SAH are likely to go unrecognized due to the difficulty of making the correct angiographic diagnosis, and such patients are con-
Lanzino et al
sidered to have suffered an SAH of unknown etiology. Several angiographic findings such as the “string sign,” “pearl reaction,” and “rosette sign” are considered characteristics of dissecting aneurysms. Fusiform dilatation may also occur. Demonstrating a double channel showing both true and false lumen is considered most important and specific to the dissecting aneurysm, but it has been demonstrated only on rare occasions [16]. Segmental narrowing can be present, and can be misdiagnosed as vasospasm in the presence of SAH [19]. Serial angiography is often required to show the evolution of the lesion [1,9], and several months may be required to show complete angiographic resolution. Angiography, however, is an invasive procedure, and the yield of repeat angiography must be weighed against the risks of the procedure. Serial image studies with less invasive tools, such as MRA and CTA, should be considered. Conventional angiography may be obtained only when these studies suggest resolution of the pathological changes. In addition, MRA and CTA can be used as adjuncts to conventional angiography to support the diagnosis of intracranial dissection. In our patient, the combination of high-resolution angiography, CTA, and MRA helped us to characterize the lesion and guide our management. In addition, MRA was shown to be useful in following the evolution of the dissection. The difficulty in the diagnosis of dissecting intracranial aneurysms obscures an assessment of the natural history of the disorder. Current therapeutic guidelines vary according to the location of the aneurysm and extent of the pathology. Patients whose dissections are limited to the intima and internal elastic lamina usually present with symptoms of ischemia and are treated conservatively or with anticoagulants [8]. Others warn against the possibility of hemorrhage caused by anticoagulants in this patient population [19] and recommend a consideration of early revascularization procedures [19]. Individuals whose aneurysms involve the entire thickness of the vessel wall present with intracranial hemorrhage and may require surgical ligation or bypass [19]. Rebleeding rates for dissecting aneurysms of the posterior fossa have been reported to be as high as 30%, and some authors use this information as an indication for hunterian ligation or bypass procedures [2]. Some lesions, however, spontaneously resolve or stabilize with nonoperative therapy [8,15]. The authors wish to acknowledge Desiree J. Lanzino and Sarah B. Hudson, who edited the manuscript.
CTA and MRA of ACA Dissecting Aneurysm
Surg Neurol 481 1997;48:477–81
REFERENCES 1. Amagasa M, Sato S, Otabe K. Posttraumatic dissecting aneurysm of the anterior cerebral artery: case report. Neurosurgery 1988;23:221–5. 2. Aoki N, Sakai T. Rebleeding from intracranial dissecting aneurysm in the vertebral artery. Stroke 1990;21: 1628 –31. 3. Farrell MA, Gilbert JJ, Kaufmann JCE. Fatal intracranial arterial dissection: clinical pathological correlation. J Neurol Neurosurg Psychiatry 1985;48:111–21. 4. Gherardi JC, Lee HY. Localized dissecting hemorrhage and arteritis, renal and cerebral manifestations. JAMA 1967;199:187– 8. 5. Guridi J, Gallego J, Monzon F, Aguilera F. Intracerebral hemorrhage caused by transmural dissection of the anterior cerebral artery. Stroke 1993;24:1400 –2. 6. Ishikawa R, Sunagawa S, Itoh I, Iwashita K. An experience of dissecting cerebral aneurysm of the anterior cerebral artery. No Shinkei Geka 1993;21:355–9. 7. Kassell NF, Torner JC, Jane JA, Haley EC Jr, Adams HP. The international cooperative study on the timing of aneurysm surgery. II. Surgical results. J Neurosurg 1990;73:37– 47. 8. Kidooka M, Okada T, Sonobe M, Nakazawa T, Handa J. Dissecting aneurysm of the anterior cerebral artery: report of two cases. Surg Neurol 1993;39:53–7. 9. Manz HJ, Luessenhop AJ. Dissecting aneurysm of intracranial vertebral artery: case report and review of literature. J Neurol 1983;230:25–35. 10. Manz HJ, Vester J, Lavenstein B. Dissecting aneurysm
11.
12. 13. 14. 15. 16.
17. 18. 19.
of the cerebral arteries in childhood and adolescence. Virchows Arch Path Anat Histol 1979;384:325– 35. Nakazawa T, Saito A, Watanabe K, Matsuda M, Handa J. Dissecting aneurysm of the anterior cerebral artery: report of a case. No Shinkei Geka 1984;12:1211–16. Nelson JW, Styri O. Dissecting subintimal hematomas of the intracranial arteries: report of a case. J Am Osteopathol Assoc 1968;67:512–7. Pilz P. Dissezierendes aneurysma der arteria cerebri anterior und Guillain-Barre-syndrom in der schwangerschaft. J Neurol 1968;214:295–9. Rinkel GJE, van Gijn J, Wijdicks EFM. Subarachnoid hemorrhage without detectable aneurysm. A review of the causes. Stroke 1993;24:1403–9. Sasaki O, Koike T, Takeuchi S, Tanaka R. Serial angiography in a spontaneous dissecting anterior cerebral artery aneurysm. Surg Neurol 1991;36:49 –53. Tanaka K, Waga S, Kojima T, Shimizu T, Niwa S. Nontraumatic dissecting aneurysms of the intracranial vertebral artery: report of six cases. Acta Neurochir (Wien) 1989;100:62– 6. Teari S, Matsubara T. A case of dissecting anuerysm involving solely anterior cerebral artery. Jpn J Stroke 1991;13:159 – 64. Turnbull HM. Alterations in arterial structure, and their relationship to syphilis. Q J Med 1915;8:201–54. Yonas H, Agamanolis D, Takaoka Y, White RJ. Dissecting intracranial aneurysms. Surg Neurol 1977;8:407– 15.
f our economy of freedom fails to distribute wealth as ably as it has created it, the road to dictatorship will be open to any man who can persuasively promise security to all; and a martial government, under whatever charming phases, will engulf the democratic world.
I
—Will and Ariel Durant “The Lessons of History” (1968)