PATHOPHYSIOLOGY OF SYRINGOMYELIA ASSOCIATED WITH CHIARI I MALFORMATION OF THE CEREBELLAR TONSILS - IMPLICATIONS FOR DIAGNOSIS AND TREATMENT
PATHOPHYSIOLOGY OF SYRINGOMYELIA ASSOCIATED WITH CHIARI I MALFORMATION OF THE CEREBELLAR TONSILS - IMPLICATIONS FOR DIAGNOSIS AND TREATMENT
复制标题
DOI：
10.3171/jns.1994.80.1.0003
复制
发表时间：
1994-01-01
影响因子：
4.1
通讯作者：
PATRONAS, NJ
中科院分区：
文献类型：
--
作者：
OLDFIELD, EH;MURASZKO, K;PATRONAS, NJ
先前提出的与小脑扁桃体 Chiari I 畸形相关的脊髓空洞症进展机制存在争议，许多临床观察结果无法解释，并且是目前用作初始治疗的不同手术普遍存在的基础。为了探讨这种情况下脊髓空洞症进展的机制，作者使用解剖和动态（相衬和相衬电影）磁共振（MR）成像和术中超声检查来检查小脑扁桃体、空洞周围脊髓壁的解剖结构和运动动力学，以及静息时、呼吸和心动周期以及心动过速期间脑脊液（CSF）和空洞液的运动。对 7 名受影响的患者进行了瓦氏动作。在所有患者中，小脑扁桃体阻塞了枕骨大孔水平的蛛网膜下腔。脊髓空洞症从颈椎延伸到脊髓的下胸段。在解剖 MR 图像、动态 MR 图像或术中超声检查中，没有患者有证据表明第四脑室和空洞之间有明显的连通。三名患者的动态 MR 图像显示，在收缩期脊髓脑脊液和空洞液突然向下运动，在舒张期向上运动，但在心动周期期间脑脊液穿过枕骨大孔的运动有限。术中超声研究表明，小脑扁桃体在心脏收缩期间突然向下运动，与脊髓和空洞的突然收缩同步。通过枕骨下颅骨切除术、C-1 和 C-2 椎板切除术以及硬脑膜移植术实现枕骨大孔减压，使蛛网膜保持完整。手术后，扁桃体的搏动性向下推力以及脊髓和空洞的收缩立即消失。所有患者的脊髓空洞症在手术后 1 至 6 个月内得到缓解。作者的观察表明，以下先前未被认识的脊髓空洞症进展机制与枕大孔蛛网膜下腔闭塞有关。在心脏收缩期间，大脑因充满血液而扩张，从而向颅内脑脊液传递收缩压波，正常受试者通过脑脊液从基底池到椎管上部的突然运动而适应该脑脊液。由于枕骨大孔处的脑脊液快速运动受到阻碍，向后堵塞蛛网膜下腔的小脑扁桃体会随着每个收缩期脉冲向下移动，充当部分隔离的脊髓脑脊液上的活塞，并在脊髓脑脊液中产生作用于脊髓表面的收缩压力波。这通过突然压缩脊髓并在每次脉冲时纵向推动空洞中的液体而导致脊髓空洞症的进展，并且可能通过脉动压力波迫使脑脊液通过血管周围和间质空间进入脊髓而导致脊髓空洞症的起源和维持。当通过解除蛛网膜下腔脑脊液穿过枕骨大孔快速移动的障碍来消除小脑扁桃体传递的收缩压波时，就会出现有效的治疗。这种机制的存在可以在术前通过动态 MR 图像以及在手术过程中通过超声研究通过空腔周围脊髓壁的脉动偏移以及扁桃体减压后用力吸气期间空腔的立即消失和扩张来检测。仅通过枕骨大孔的骨和硬脑膜减压而不进入蛛网膜即可实现有效的治疗。
The mechanisms previously proposed for the progression of syringomyelia associated with Chiari I malformation of the cerebellar tonsils are controversial, leave many clinical observations unexplained, and underlie the prevalence of different operations currently used as initial treatment. To explore the mechanism of syringomyelia progression in this setting, the authors used anatomical and dynamic (phase-contrast and phase-contrast cine) magnetic resonance (MR) imaging, and intraoperative ultrasonography to examine the anatomy and dynamics of movement of the cerebellar tonsils, the wall of the spinal cord surrounding the syrinx, and the movement of cerebrospinal fluid (CSF) and syrinx fluid at rest, during the respiratory and cardiac cycles, and during Valsalva maneuver in seven affected patients.In all patients the cerebellar tonsils occluded the subarachnoid space at the level of the foramen magnum. Syringomyelia extended from the cervical to the lower thoracic segment of the spinal cord. No patient had evidence of a patent communication between the fourth ventricle and the syrinx on anatomical MR images, dynamic MR images, or intraoperative ultrasound studies. Dynamic MR images of three patients revealed abrupt downward movement of the spinal CSF and the syrinx fluid during systole and upward movement during diastole, but limited movement of CSF across the foramen magnum during the cardiac cycle. Intraoperative ultrasound studies demonstrated abrupt downward movement of the cerebellar tonsils during systole that was synchronous with sudden constriction of the spinal cord and syrinx. Decompression of the foramen magnum was achieved via suboccipital craniectomy, laminectomy of C-1 and C-2, and dural grafting, leaving the arachnoid intact. Immediately after surgery, the pulsatile downward thrust of the tonsils and constriction of the spinal cord and syrinx disappeared. Syringomyelia resolved within 1 to 6 months after surgery in all patients.Observations by the authors suggest the following previously unrecognized mechanism for progression of syringomyelia associated with occlusion of the subarachnoid space at the foramen magnum. The brain expands as it fills with blood during systole, imparting a systolic pressure wave to the intracranial CSF that is accommodated in normal subjects by sudden movement of CSF from the basal cisterns to the upper portion of the spinal canal. With obstruction to rapid movement of CSF at the foramen magnum, the cerebellar tonsils, which plug the subarachnoid space posteriorly, move downward with each systolic pulse, acting as a piston on the partially isolated spinal CSF and producing a systolic pressure wave in the spinal CSF that acts on the surface of the spinal cord. This causes progression of syringomyelia by abruptly compressing the cord and propelling the fluid in the syrinx longitudinally with each pulse, and may be responsible for the origin and maintenance of syringomyelia by the pulsatile pressure waves forcing CSF into the cord through the perivascular and interstitial spaces. Effective treatment occurs when the systolic pressure wave transmitted by the cerebellar tonsils is eliminated by relieving the obstruction to rapid movement of subarachnoid CSF across the foramen magnum. The presence of this mechanism can be detected preoperatively on dynamic MR images and during surgery on ultrasound studies by the pulsatile excursion of the wall of the spinal cord surrounding the syrinx and by its immediate disappearance and the expansion of the syrinx during forced inspiration after decompression of the tonsils. Effective treatment is achieved with bone and dural decompression of the foramen magnum alone, without entering the arachnoid.