British Journal of Neurosurgery, August 2007; 21(4): 406 – 410 SHORT REPORT Intracranial aneurysm and arachnoid cyst: a rare association between two cerebral malformations Br J Neurosurg Downloaded from informahealthcare.com by V U L Periodicals Rec on 12/27/14 For personal use only. J. G. DE OLIVEIRA, M. GIUDICISSI-FILHO, A. RASSI-NETO, L. A. B. BORBA, M. S. RASSI, S. L. SANCHEZ-JÚNIOR, C. A. A. RIBEIRO & C. V. M. DE HOLANDA Department of Neurosurgery, Center of Neurology and Neurosurgery Associates (CENNA), Hospital Beneficência Portuguesa de São Paulo, São Paulo-SP, Brazil Abstract Intracranial aneurysms and arachnoid cysts are cerebral disorders of a high prevalence. However, association between both malformations is a rare finding. The aim was to analyse this association with regard to the different clinical presentations according to the haemorrhage types, as well as the pathogenesis of this association. We searched the English language literature in MEDLINE database in order to include all manuscripts in which this association was found. A new case of a 55year-old man with a large posterior communicating artery aneurysm and a middle cranial fossa arachnoid cyst presenting with headache and seizure was added to review of the literature and presented as an illustrative case. Nine cases were found. Six were male and three were female. The mean age was 42 years (range 29 – 66 years). All but one arachnoid cysts were located at middle cranial fossa, aneurysms arose from middle cerebral artery in three cases, internal carotid artery bifurcation in two cases, posterior communicating segment of carotid artery in two cases, anterior communicating artery in one case and azygos pericallosal artery in one case. Clinical presentation was related to aneurysmal rupture in six cases (subarachnoid haemorrhage in four, subdural haematoma in one and intracystic haematoma in two) and related to arachnoid cysts in three cases, where the most common symptoms were seizures and headache. Association between intracranial aneurysms and arachnoid cysts is a rare finding that can present with signs and symptoms related to aneurysm rupture, or with mass effect and seizures related to the cyst. The aneurysmal haemorrhage may be atypical, since it can be into the subarachnoid space, into the arachnoid cyst, or into the subdural space. Key words: Arachnoid cyst, cerebral malformations, incidental aneurysm, intracranial aneurysm, middle cranial fossa, seizure. Introduction Material and methods Population prevalence of cerebral aneurysm ranges between 1 and 5% in autopsy studies,1 – 3 while in angiography studies it ranges between 1 and 10%.4,5 Arachnoid cysts occur in about 0.5% of autopsies as an incidental finding6,7 and they are believed to account for about 1% of all intracranial expansive lesions.8 In spite of the high prevalence of both diseases, association between intracranial aneurysm and arachnoid cyst is very unusual, but with clinical peculiarities and an intriguing pathogenesis. We performed a comprehensive review of the literature in order to identify all cases where these two intracranial malformations were found and to discuss the pathophysiology of the bleeding in ruptured aneurysm cases and the pathogenesis of this association. We searched the English language literature in MEDLINE (1966 to February 2007) database in order to include all manuscripts where association between intracranial aneurysm and arachnoid cyst was found. A new case is added to review of the literature and presented as an illustrative case. Results Association between intracranial aneurysm and arachnoid cyst was found in only eight previous case reports after a comprehensive review of the literature.9 – 16 All of them, including our new case, are listed in the Table I. Analysing these nine cases, six were male and three female. The mean age was 42 years (range 29 – 66 years). All but one arachnoid cysts were located at Correspondence: J. G. de Oliveira, Rua Sena Madureira, 1123 ap.61, 04021-051. São Paulo-SP. Brasil. Tel: 55-11-55718432. Fax: 55-11-32666296. E-mail: jeangol@uol.com.br Received for publication 7 February 2007. Accepted 22 May 2007. ISSN 0268-8697 print/ISSN 1360-046X online ª The Neurosurgical Foundation DOI: 10.1080/02688690701466313 Left middle cerebral artery bifurcation Anterior communicating artery Right middle cerebral artery bifurcation Left internal carotid artery bifurcation Azygos pericallosal artery Left posterior communicating artery Left middle cerebral artery bifurcation Left internal carotid artery bifurcation Left posterior communicating artery Left middle fossa Left middle fossa Right convexity Left middle fossa Right middle fossa Left middle fossa Left middle fossa Left middle fossa Left middle fossa No No SAH Intracystic hematoma SAH SAH Intracystic and subdural hematoma SAH No Illustrative case A 55-year-old white man was admitted with complaints of headache and seizures that had developed during a period of 1 year. He had previous history of systemic arterial hypertension, smoking, alcoholism and bariatric surgery 5 years before. The neurological examination was normal. The computerized tomography (CT) scan demonstrated a low density area in the left middle cranial fossa and a round spontaneously hyperdense formation suggestive of an arachnoid cyst and a saccular aneurysm (Fig. 1). Cerebral angiography showed a large aneurysm (1.5 cm) arising from the posterior communicating segment of the left internal carotid artery (Fig. 2). There were no clinical or radiological signs of subarachnoid haemorrhage (SAH). Unfortunately, MRI was not available at that moment. The patient was submitted to a left pterional craniotomy. The opening of the left middle cranial fossa arachnoid cyst was performed, providing a communication with the carotid-chiasmatic cistern. Then, the aneurysm was exposed and successfully clipped (Fig. 3). The postoperative period was uneventful. Discussion Female Male Male SAH: Subarachnoid haemorrhage. 1999 2000 2007 Huang et al.15 Zanini et al.16 de Oliveira et al. (New illustrative case) 407 middle cranial fossa; aneurysms arose from middle cerebral artery (MCA) in three cases, internal carotid artery (ICA) bifurcation in two cases, posterior communicating segment of carotid artery (P-comm) in two cases, anterior communicating artery (ACoA) in one case and azygos pericallosal artery in one case; clinical presentation was related to aneurysmal rupture in six cases (subarachnoid haemorrhage in four, subdural haematoma in one and intracystic haematoma in two) and related to arachnoid cysts in three cases, where the most common symptoms were seizures and headache. 61 35 55 1979 1986 1987 1995 1996 1998 Leo et al.9 Schumacher et al.10 Jinkins et al.11 Hirose et al.12 Baykal et al.13 Barker et al.14 55 39 40 45 66 29 Male Male Male Male Female Female Headaches; speech arrest Seizures Sudden headache, nausea and vomiting Sudden headache Sudden headache Sudden headache, nausea and vomiting photophobia and neck stiffness Sudden headache Headache, right hemiparesis and aphasia Headache and seizures Location of aneurysm Location of arachnoid cyst Haemorrhage Signs and symptoms Gender Age Year Author TABLE I. Summary data about the cases where association between intracranial aneurysm and arachnoid cyst was found Br J Neurosurg Downloaded from informahealthcare.com by V U L Periodicals Rec on 12/27/14 For personal use only. Intracranial aneurysm and arachnoid cyst Intracranial aneurysms and arachnoid cysts are relatively common cerebral malformations. However, association between these two disorders is very rare.16 Our new case added to the previous cases from literature review resulted in only nine cases published to date. Although association between intracranial aneurysm and arachnoid cyst is a rare finding, its clinical presentation and pathogenesis have some variable factors. Asymptomatic incidental aneurysms have a prevalence rate of 0.65% and yearly rate of rupture within the range 1 – 2%.17 With regard to location, the middle cranial fossa hosts nearly half (49%) of all intracranial arachnoid cysts.18 When localized in the middle cranial fossa, arachnoid cysts commonly present with seizures, headache and hemiparesis.19 Arachnoid cysts may bleed spontaneously or after relatively minor trauma resulting in subdural Br J Neurosurg Downloaded from informahealthcare.com by V U L Periodicals Rec on 12/27/14 For personal use only. 408 J. G. De Oliveira et al. FIG. 1. CT scan showing a low density area in the left middle cranial fossa suggestive of an arachnoid cyst and a round spontaneously hyperdense formation suggestive of a saccular aneurysm (arrows). FIG. 2. Cerebral angiography showing a large aneurysm (1, 5cm) arising from the posterior communicating segment of the left carotid artery (arrows). Br J Neurosurg Downloaded from informahealthcare.com by V U L Periodicals Rec on 12/27/14 For personal use only. Intracranial aneurysm and arachnoid cyst 409 FIG. 3. Surgical view after a pterional craniotomy and dura-mater opening. A) superficial aspect of Sylvian fissure; B) Surgical opening in the superior wall of the arachnoid cyst; C) Inside aspect of the arachnoid cyst; D) Inferior wall of the arachnoid cyst; E) Surgial opening in the inferior wall of the arachnoid cyst (arrows), communicating it with carotid-chiasmatic cistern and revealing an aneurysm (AN) neck (dashed line) arising from the posterior communicating segment of the left carotid artery (CA); F) After aneurysm occlusion with surgical clipping. haematoma, intracystic haemorrhage or both.20,21 Subdural haematoma due to ruptured intracranial aneurysm is a rare finding, which may be found with22 or without23 subarachnoid haemorrhage. Pure subdural haematoma due to ruptured aneurysm can be explained by the existence of local tear in the arachnoid membrane through which it can bleed directly into the subdural space.23 It is well know that arachnoid cysts may either communicate with or be isolated from the subarachnoid space.24 Consequently, there were two cases reported where a ruptured aneurysm was not anatomically close to the arachnoid cyst and the bleed was found in the subarachnoid space and inside the cyst in one,11 and restricted to subarachnoid space in another case.13 Therefore, in cases of a typical history of subarachnoid haemorrhage, without evidence of bleeding in CT scans and incidental arachnoid cyst, we advise referring these patients to an angiography, as well as in cases with spontaneous haemorrhage restricted to arachnoid cyst. The exact aetiology and pathogenesis of both arachnoid cysts and intracranial aneurysms remain unclear. However, there is some evidence for the role of genetic factors.25,26 The main line of evidence for genetic factors is the association of both diseases with heritable connective tissue disorders.25 Autosomal dominant polycystic kidney disease (ADPKD) is one of the more common genetic diseases and the propensity of affected patients to develop intracranial aneurysm25,27 and arachnoid cysts28 is well recognized. Schievink and colleagues26 analysed a series of 247 patients with ADPKD, and found an association with intracranial aneurysm in 10.8% and arachnoid cyst in 8.1%. However, they found no correlation between both disorders. There was no reference about ADPKD in the case described, as well as in the eight previous cases where this association was found. Since the arachnoid and muscle layer of arteries have a mesenchymal embryonic origin, probably the association between arachnoid cysts and intracranial aneurysms may represent two products of a single dysembryogenesis.16 Conclusion Association between intracranial aneurysm and arachnoid cyst is a rare finding that can presenting with signs and symptoms related to aneurysm bleeding or mass effect, and seizures from the cyst. Regarding the pathogenesis of this association, we believe that it likely represent two findings of a single dysembryogenesis, since both arachnoid and muscle layer of arteries have the same mesenchymal embryonic genesis. References 1 Inagawa T, Hirano A. Autopsy study of unruptured incidental intracranial aneurysms. Surg Neurol 1990;34(6):361 – 5. 2 McCormick WF, Schmalstieg EJ. The relationship of arterial hypertension to intracranial aneurysms. Arch Neurol 1977; 34(5):285 – 7. 3 Sugar O. Autopsy study of unruptured incidental intracranial aneurysms. 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