Direct Imaging of Paraclinoid Aneurysms and The Distal Dural Ring with High-Resolution MR Imaging 床突旁动脉瘤和远端硬膜环的高分辨核磁 全军脑卒中医疗救治研究中心 新纪元脑卒中医疗救治研究中心 中国人民解放军第二炮兵总医院神经内科 王佳楠

Background Over the years, aneurysms of the proximal ICA have been placed under different classifications by various authors because the anatomy is complex in the area where the ICA enters the intradural space through the dura mater. In this study we will call the penetrating segment of the ICA the “paraclinoid ICA”, which includes the C4 (cavernous), C5 (clinoid) and C6 (ophthalmic) segments of the ICA, as described by Bouthillier. One reason for the difficulty in classifying these aneurysms is the complex anatomy of the paraclinoid region.

Background Giant, multiple and bilateral aneurysms are more frequent in this group of aneurysms. Surgical clipping of these aneurysms is technically challenging due to the adjacent bony anatomy and neurovascular structures. Because an intradural arterial aneurysm carries a potential risk of subarachnoid hemorrhage (SAH), it is important to determine whether a paraclinoid aneurysm is intra- or extradural.

Anatomic features and adjacencies of clinoid segment of internal carotid artery B Fig A (lateral view)：the clinoid segment of left internal carotid artery, the double arrow shows the length of clinoid segment measured.1-OA; 2-ICA; 3-ON; 4-DDR; 5-PDR Fig B (axial view)：multi-slice spiral CT scanning showing relationship of ACP (a)、ICA (b) and OA(c)

T2 turbo- spin echo(TSE) MRI using a 3-T magnetic resonance scanner (General Electric, Milwaukee, WI) with an 8 channel Head Coil using fast recovery, fast spin echo sequence with the array spatial sensitivity encoding technique thickness, 0 space/gap, 448× 448 matrix, number of excitations 4, and echo train length of 17. Repetition time was 4700 to 6550 milliseconds, and echo time was 104.6 to 110.6 milliseconds The DDR is identified as the dural reflection that surrounds the ICA when it exits the cavernous sinus roof Neurosurgery，2009，64：1059-1064

T2 turbo- spin echo(TSE) MRI intradural aneurysm a medially located intradural paraclinoid aneurysm with both the neck and the sac located above the distal dural ring (DDR) Neurosurgery，2009，64：1059-1064

T2 turbo- spin echo(TSE) MRI extradural aneurysms aneurysm 1 (An 1) is extradural (under the DDR) and aneurysm 2 (An 2) is extradural (under the DDR and the clinoid process: subclinoid aneurysm). Neurosurgery，2009，64：1059-1064

contrast-enhanced (CE) 3D constructive interference in steady state (CISS) MRI MR imaging studies were performed with a circularly polarized head coil and a 1.5T superconducting system (Magnetom Vision; Siemens, Erlangen, Germany). fast spin-echo T2-weighted (TR/TEeff/NEX, 3500/96/2; echo-train length, 7), and contrast enhanced T1-weighted sequences. The T1- and T2-weighted sequences were performed at a section thickness of 5mmwith a 1-mm intersection gap, a 256256 matrix, and a 22-cm FOV. To understand the imaging characteristics, we assessed the boundary and signal intensity of the cavernous sinus, CSF, and carotid artery on the side contralateral to the lesion. On CE 3D-CISS images, multiple aneurysms adjacent to the anterior clinoid process or a giant aneurysm render accurate diagnosis difficult. AJNR Am J Neuroradiol 29:130 –33 Jan 2008

contrast-enhanced (CE) 3D constructive interference in steady state (CISS) MRI extradural aneurysm revealing that the aneurysm (large arrow) is extradural, located in the cavernous sinus. This observation was confirmed by surgery. The small arrow indicates the boundary between the cavernous sinus and the CSF. AJNR Am J Neuroradiol 29:130 –33 Jan 2008

T2-weighted three dimensional(3D) fast spin-echo (FSE) MRI MR imagings were acquired by using a 1.5-T system (Intera; Philips Medical Systems, Best, the Netherlands) with a six-channel sensitivity encoding (SENSE) head coil. The T2-weighted 3-D FSE-driven equilibrium RF reset pulse (DRIVE) sequence was performed with the following parameters : TR/TE= 1500/160 ms, 256 acquisition/256 reconstruction, 13-cm field of view, 1.5-mm section thickness with a 0.75-mm overlap, number of acquisitions = 2 and the total imaging time was less than 10 minutes. J Korean Neurosurg Soc 47 : 437-441, 2010

T2-weighted three dimensional(3D) fast spin-echo (FSE) MRI J Korean Neurosurg Soc 47 : 437-441, 2010

T2-weighted three dimensional(3D) fast spin-echo (FSE) MRI intradural aneurysm an aneurysm (arrow) within the cistern, arising from the medial aspect of the intradural ICA. Intraoperative photograph shows a superolateral view of the right paraclinoid region. The anterior clinoid process was drilled, exposing the aneurysm neck (arrow) protruding medially above the dissected distal dural ring (arrowheads). Clin. : clinoid, CN II : optic nerve, ICA : internal carotid artery. J Korean Neurosurg Soc 47 : 437-441, 2010

T1-weighted contrast-enhanced three dimensional(3D) space MRI SPACE（sampling perfection with application optimized contrasts by using different flip angle evolutions）is 3D fast spin echo imaging technology, SPACE sequence and TSE sequence is different in the use of complex phase pulse flip Angle, to solve the deficiencies of TSE sequence, the optimized Angle mode change, to overcome the T2 attenuation effect. SAR values decrease, echo chain can be significantly increased. SPACE as follows: the characteristics of high resolution, high signal-to-noise ratio and high collection rate, deficiency is the hardware requirements are higher.

T1-weighted contrast-enhanced three dimensional(3D) space MRI MR imagings were acquired by using a 3-T system (Magnetom Vision; Siemens, Erlangen, Germany) with a twenty-channel sensitivity encoding (SENSE) head-neck coil. The T1-weighted 3D space sequence was performed with the following parameters : TR/TE= 600/20ms, 256 acquisition/256 reconstruction, 22cm field of view, 0.9mm section thickness with a 0mm overlap, number of acquisitions=2 and the total imaging time was less than 10 minutes.

1 病例 左侧颈内动脉C5段动脉瘤 女性，51岁，主因头痛20天入院。既往史：小儿麻痹后遗症，右下肢行走不稳。 临 床 资 料 女性，51岁，主因头痛20天入院。既往史：小儿麻痹后遗症，右下肢行走不稳。 查体：NIHSS评分0分，Hunt-Hess评级0级。 诊断：1.左侧颈内动脉动脉瘤 治疗：弹簧圈栓塞术

病例1-LC5 extradural aneurysm T1 ACP OA ON DDR DDR Sac ICA T1-enhanced Neck Sac ICA A medially located extradural paraclinoid aneurysm with both the neck and the sac located under the distal dural ring (DDR)

病例 2 左侧颈内动脉C5段动脉瘤 临 床 资 料 男性，57岁，主因反复发作性头晕伴右侧肢体力弱8年，突发意识丧失1天入院。既往史：高血压病史8年，血压最高160/100mmHg。 查体：GCS评分15分，HUNT-HESS评分0分，Fisher评分0分，WFNS评分0分。 诊断：1.左侧颈内动脉动脉瘤；2.高血压病3极高危；3.脑梗死 治疗：支架辅助弹簧圈栓塞术

病例2-LC6 intradural aneurysm DDR Sac DDR ICA T1 Sac DDR DDR ICA T1-enhanced A medially located intradural paraclinoid aneurysm with both the neck and the sac located above the distal dural ring (DDR)

3 病例 左侧颈内动脉C6段动脉瘤 女性，55岁，主因间断头部不适1年余入院。既往体健。 临 床 资 料 女性，55岁，主因间断头部不适1年余入院。既往体健。 查体：GCS评分15分，Hunt-Hess评级0级。 诊断：1.左侧颈内动脉动脉瘤 治疗：左侧翼点入路动脉瘤夹闭复合术

病例3-LC6 intradural aneurysm DDR DDR Sac ICA T1 DDR DDR Sac A medially located intradural paraclinoid aneurysm with both the neck and the sac located above the distal dural ring (DDR) ICA T1-enhanced

病例 4 左侧颈内动脉C4段动脉瘤 临 床 资 料 男性，57岁，主因反复发作性头晕伴右侧肢体力弱8年，突发意识丧失1天入院。既往史：高血压病史8年，血压最高160/100mmHg。 查体：GCS评分15分，HUNT-HESS评分0分，Fisher评分0分，WFNS评分0分。 诊断：1.左侧颈内动脉动脉瘤；2.高血压病3极高危；3.脑梗死 治疗：支架辅助弹簧圈栓塞术

病例4-LC4 extradural aneurysm DDR DDR Sac Sac ICA ICA T1-enhanced T1 A lateral located extradural paraclinoid aneurysm with both the neck and the sac located under the distal dural ring (DDR)

5 病例 左侧颈内动脉C4段动脉瘤 女性，53岁，主因间断头痛伴复视1年，加重伴左眼睑下垂4天入院。既往体健。 临 床 资 料 女性，53岁，主因间断头痛伴复视1年，加重伴左眼睑下垂4天入院。既往体健。 查体：左侧Ⅱ、Ⅲ、Ⅳ、Ⅴ、Ⅵ颅神经功能障碍。GCS评分15分，HUNT-HESS评分0分。 诊断：1.左侧颈内动脉动脉瘤 治疗：载瘤动脉栓塞术

病例5-LC4 extradural aneurysm DDR ACP DDR DDR ICA ICA Sac T1 Sac ACP DDR T1-enhanced Sac Sac ACP ON DDR DDR DDR ICA ICA Sac Sac Water imaging A lateral located extradural paraclinoid aneurysm with both the neck and the sac located under the distal dural ring (DDR)

Results Patient no. Age(y)/sex ACP DS ICA ON DDR MR location 1 51/F ++ ++ ++ ++ ++ ExtraD 2 57/M ++ ++ ++ + ++ IntraD 3 55/F + ++ ++ + ++ IntraD 4 57/M + ++ ++ + ++ ExtraD 6 53/F ++ ++ ++ ++ ++ ExtraD

Conclusion This study demonstrated that T1-weighted contrast-enhanced three dimensional(3D) space MR imaging can directly visualize the DDR as well as its anatomic relationship with paraclinoid aneurysms. In the evaluation of paraclinoid aneurysms, we believe that preoperative imaging with this MR technique is advisable.

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