dish and apparent fusiform aneurysm was noted at the top of the arterial loop ... Left subclavian artery ... right PICA and its caudal loop, the course of the right.
Neurol Med Chir (Tokyo) 52, 81¿83, 2012
Ruptured Aneurysm of a Posterior Inferior Cerebellar Artery Communicating Artery —Case Report and Histological Findings— Shin-ichiro SUGIYAMA,1 Miki FUJIMURA,1 Takashi INOUE,1 Hiroaki SHIMIZU,1 Mika WATANABE,2 and Teiji TOMINAGA3 1Department
of Neurosurgery, Kohnan Hospital, Sendai, Miyagi; Departments of 2Pathology and 3Neurosurgery, Tohoku University Graduate School of Medicine, Sendai, Miyagi
Abstract A hypertensive 60-year-old man presented with a rare aneurysm arising from the posterior inferior cerebellar artery (PICA) communicating artery, manifesting as subarachnoid hemorrhage with intraventricular hemorrhage. Angiography showed a small aneurysm arising from a fine and tortuous artery interconnecting the bilateral vermian branches of distal PICAs. The right PICA was absent and its vermian territory was supplied by the left PICA through this communicating artery. The right anterior inferior cerebellar artery was also connected to the vermian branch of the right PICA. At surgery, a reddish and apparent fusiform aneurysm was noted at the top of the arterial loop under the cerebellar vermis. Microsurgical trapping and removal of the aneurysm was performed without complication. Histological examination demonstrated typical findings of a true aneurysm. Only four previous cases of aneurysm of the communicating artery between the bilateral distal PICAs have been reported. In all five reported cases including ours, the PICA communicating artery contributed to the collateral blood supply of the contralateral vermian territory based on vascular anomalies. Hemodynamic stress and congenital vulnerability may have caused this aneurysm. Trapping is suitable to treat this precarious aneurysm if other collateral vessels supply the contralateral vermian territory. Key words: aneurysm, posterior inferior cerebellar artery, histological analysis, surgical procedure
subarachnoid hemorrhage,
Introduction
Case Report
The majority of posterior inferior cerebellar artery (PICA) aneurysms develop at the junction of the vertebral artery and the PICA, but true PICA aneurysms, especially at the distal part of this artery, are relatively rare.3,4,9) True PICA aneurysms can occur at any segment along the tortuous course of the PICA,5) but such aneurysms arising from the small branches of the PICA are extremely rare, with only four reported cases with ruptured aneurysms originating in the communicating branch between the bilateral distal PICAs, the so-called `PICA communicating artery.'1,2,8,10) Here we present another case of ruptured aneurysm arising from the PICA communicating artery, successfully treated by trapping and resection of the aneurysm. The histological characteristics of this rare aneurysm are described for the first time.
A 60-year-old man presented with severe occipital headache and vomiting, and was admitted to our hospital. He had a history of hypertension, diabetes mellitus, and dyslipidemia. Neurological examination found no focal neurological deficits. Computed tomography on admission showed subarachnoid hemorrhage with intraventricular hematoma in the fourth, third, and the bilateral lateral ventricles. Right vertebral angiography showed a fusiform aneurysm (size 2.5 × 2.5 mm) originating from a fine tortuous artery interconnecting the bilateral vermian branches of distal PICAs (Fig. 1). Left subclavian artery angiography demonstrated absence of the left vertebral artery. The right PICA was absent and its vermian territory was supplied by the left PICA through this communicating artery. The right anterior inferior cerebellar artery (AICA) was also connected the vermian branch of the right PICA. A midline suboccipital craniotomy was performed in
Received May 19, 2011; Accepted June 16, 2011 Author's present address: M. Fujimura, MD, PhD, Department of Neurosurgery, National Hospital Organization, Sendai Medical Center, Sendai, Miyagi, Japan.
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Fig. 2 Intraoperative photographs showing both the afferent (arrow) and efferent arteries (thick arrow) of the aneurysm (arrowhead) were trapped, and the aneurysm along with parts of the input and output arteries were dissected en bloc.
Fig. 3 Photomicrographs (areas indicated in inset) showing the internal elastic lamina disrupted only at the rupture point, typical of true aneurysms. No findings indicated dissecting aneurysm such as thinning of the media or blood filling between the intima and media. Elastica-Masson stain, original magnification ×40. Fig. 1 A, B: Preoperative conventional digital subtraction angiograms of the right vertebral artery, anteroposterior (A) and lateral views (B), demonstrating an aneurysm of the posterior inferior cerebellar artery (PICA) communicating artery (arrows). C–F: Three-dimensional rotational digital angiograms of the right vertebral artery, anteroposterior (C), lateral (D), and posteroanterior views (E, F), showing the PICA communicating artery in yellow, the left vermian branch in green, and other vessels including the right vermian branch in red. A fine tortuous artery (the PICA communicating artery) interconnected the bilateral vermian branches. The aneurysm arose from the PICA communicating artery. The left anterior inferior cerebellar artery (blue) also connected to the left vermian branch.
the prone position. After identification of the origin of the right PICA and its caudal loop, the course of the right PICA was traced distally and a reddish and apparent fusiform aneurysm exposed adhering to the inferior vermis (Fig. 2). Both afferent and efferent arteries of the aneurysm were trapped, and the aneurysm along with parts of the afferent and efferent arteries were dissected en bloc. The postoperative course was uneventful, and the patient did not develop cerebral vasospasm. Postoperative magnetic resonance imaging indicated no ischemic change in the cerebellar hemispheres or brainstem. Histological examination demonstrated disruption of the internal elastic lamina only at the rupture point, suggesting the typical findings of a true aneurysm (Fig. 3).
Discussion Since the first case of ruptured aneurysm in a PICA communicating artery was reported in 1991,2) only five cases including the present case have been described (Table 1).1,8,10) The 2 male and 3 female patients were aged from 45 to 68 years (mean 57.0 years). Four of the five patients were Japanese. The aneurysm size was generally small: 2–3 mm in diameter in 4 cases, and less than 5 mm in 1 case. In our case, the aneurysm diameter was also small at 2.5 mm, and three-dimensional (3D) rotational angiography facilitated detection of the aneurysm at this rare location. Therefore, high-quality imaging study including 3D digital angiography is needed to detect aneurysms at this location.8) The five cases had common pathophysiological characteristics. All reported cases presented with contralateral vascular anomalies such as defect or hypoplasia of the PICA, AICA, or vertebral artery, which resulted in flow reduction in the vermian territory. Under such conditions, a collateral vascular network including a PICA communicating artery develops to supply the contralateral vermian territory. Our patient also had occlusion of the contralateral vertebral artery, and the vascular territory of the contralateral vermis was supplied by the ipsilateral PICA through this communicating artery (Fig. 1). These findings strongly suggest the contribution of hemodynamic
Neurol Med Chir (Tokyo) 52, February, 2012
PICA Communicating Artery Aneurysm
Table 1
83
Summary of the 5 cases of posterior inferior cerebellar artery communicating artery aneurysm
Author (Year)
Age (yrs)/Sex
Hunt & Hess grade
Aneurysm shape
Diameter (mm)
Treatment
Outcome
Hlavin et al. (1991)2) Udono et al. (1997)10) Fujiwara et al. (1999)1) Okuno and Ohnishi (2001)8) Present case
45/F 51/F 61/F 68/M 60/M
3 3 3 4 2
saccular saccular saccular fusiform fusiform
º5 2.5 3 3 2.5
neck clipping neck clipping neck clipping trapping trapping
excellent excellent excellent poor excellent
F: female, M: male.
stress in this communicating artery to the formation and rupture of the aneurysm at the distal PICA, which is known to have congenital vulnerability of the vascular wall.4,7,8) Trapping surgery can be attempted to treat this precarious aneurysm. Among the five reported cases, two were trapped and three were clipped. Two aneurysms treated by the trapping procedure including our case showed the same intraoperative findings: the aneurysms had a reddish thin wall and was likely to grow as if the parent artery had expanded. In the present case, we could not rule out the possibility of pseudoaneurysm including arterial dissection, so we performed trapping and resection of the aneurysm. Histological evaluation of the aneurysm suggested a true aneurysm. We recommend trapping of such an aneurysm since such `apparent' fusiform aneurysms are difficult to clip at the neck with preservation of the parent artery, and the intraoperative findings do not always exclude the possibility of pseudoaneurysm. Further histological assessment of a larger number of patients is warranted to address this important issue. Microsurgical trapping introduces the risk of cerebral ischemia in the vascular territory of the PICA communicating artery, but the distal part of the telovelotonsillar segment can be sacrificed because no perforators irrigate the brainstem and ipsilateral superior cerebellar artery and/or the AICA generally supplies collateral blood flow.5,6) Furthermore, the left AICA was connected to the distal part of the left vermian branch in our patient, and was expected to supply sufficient collateral blood flow to the vascular territory of the PICA communicating artery. Based on these observations, we performed trapping and resection of the aneurysm without complication. Careful preoperative planning is recommended to avoid ischemic complication after this procedure, and extracranial-intracranial bypass including occipital artery-PICA anastomosis may be useful for patients with a poor collateral network. Alternatively, intraoperative monitoring by indocyanine green video-angiography prior to the trapping procedure may be useful to confirm sufficient collateral blood flow to the vascular territory of the PICA communicating artery. PICA communicating artery aneurysm is generally small, so neck clipping or intraaneurysmal coiling is
Neurol Med Chir (Tokyo) 52, February, 2012
difficult to perform. Therefore, a trapping procedure may be acceptable if adequate collateral flow supplies the contralateral vermian territory.
References 1)
Fujiwara K, Ito J, Kanayama S: [Multiple aneurysms of the PICA communicating artery: a case report]. No Shinkei Geka 27: 177–182, 1999 (Japanese) 2) Hlavin ML, Takaoka Y, Smith AS: A ``PICA communicating artery'' aneurysm: case report. Neurosurgery 29: 926–929, 1991 3) Horiuchi T, Tanaka Y, Hongo K, Nitta J, Kusano Y, Kobayashi S: Characteristics of distal posteroinferior cerebellar artery aneurysms. Neurosurgery 53: 589–595, 2003 4) Hudgins RJ, Day AL, Quisling RG, Rhoton AL Jr, Sypert GW, Garcia-Bengochea F: Aneurysms of the posterior inferior cerebellar artery. A clinical and anatomical analysis. J Neurosurg 58: 381–387, 1983 5) Lewis SB, Chang DJ, Peace DA, Lafrentz PJ, Day AL: Distal posterior inferior cerebellar artery aneurysms: clinical features and management. J Neurosurg 97: 756–766, 2002 6) Lister JR, Rhoton AL Jr, Matsushima T, Peace DA: Microsurgical anatomy of the posterior inferior cerebellar artery. Neurosurgery 10: 170–199, 1982 7) Nishizaki T, Tamaki N, Nishida Y, Fujita K, Matsumoto S: Aneurysms of the distal posterior inferior cerebellar artery: experience with three cases and review of the literature. Neurosurgery 16: 829–832, 1985 8) Okuno S, Ohnishi H: Aneurysm of the posterior inferior cerebellar arteries/communicating artery. Cerebrovasc Dis 12: 276–279, 2001 9) Salcman M, Rigamonti D, Numaguchi Y, Sadato N: Aneurysms of the posterior inferior cerebellar artery-vertebral artery complex: variations on a theme. Neurosurgery 27: 12–20, 1990 10) Udono H, Shiraishi T, Tsuji T, Abe M, Tabuchi K: [True ``PICA communicating artery'' aneurysm: a case report]. No Shinkei Geka 25: 763–766, 1997 (Japanese)
Address reprint requests to: Miki Fujimura, MD, PhD, Department of Neurosurgery, National Hospital Organization, Sendai Medical Center, 2–8–8 Miyagino, Miyagino–ku, Sendai, Miyagi 983–8520, Japan. e-mail: fujimur＠nsg.med.tohoku.ac.jp
