Elucidating the pathophysiology of syringomyelia
Elucidating the pathophysiology of syringomyelia
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DOI：
10.3171/jns.1999.91.4.0553
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发表时间：
1999-10-01
影响因子：
4.1
通讯作者：
Oldfield, EH
中科院分区：
文献类型：
--
作者：
Heiss, JD;Patronas, N;Oldfield, EH
Object.脊髓空洞症导致进行性脊髓病。大多数患有脊髓灰质炎的患者都有小脑扁桃体的基亚里畸形。确定与基亚里I畸形相关的脊髓灰质炎进展的病理生理学机制应改善阻止脊髓病进展的策略。作者前瞻性研究了20例同时患有基亚里I畸形和症状性脊髓灰质炎的成人患者。术前测试包括以下内容：临床检查;使用T-1加权磁共振（MR）成像评价解剖结构;使用相位对比电影MR成像评价空洞和脑脊液（CSF）速度和流量;评价静息时、Valsalva动作期间、颈静脉压迫期间和取出CSF后的腰椎和颈椎蛛网膜下腔压力（CSF顺应性测量）。在手术过程中，从颅内、颈部蛛网膜下腔和腰椎鞘内空间和空洞获得心脏门控超声检查和压力测量值。术后6个月，重复进行临床检查、MR成像研究和CSF压力记录。每年重复进行临床检查和MR成像研究。为了比较，18名健康志愿者进行了T-1加权磁共振成像，电影磁共振成像，颈和腰蛛网膜下腔压力测试，与健康志愿者相比，手术前，患者的腹侧和背侧的CSF间隙的前后径减少。在患者中，枕骨大孔处的CSF流速增加，但CSF流量减少。颈静脉压迫引起的颅内压通过枕骨大孔向脊髓蛛网膜下腔的传递部分受阻。脊髓CSF顺应性降低，而颈部蛛网膜下腔压力和脉压增加。磁共振电影成像显示，收缩期脊髓空洞液向左流动，舒张期脊髓空洞液向上流动。在手术中，小脑扁桃体在收缩期突然下降，在收缩期上升，空洞的上极以与扁桃体下降和收缩期颈部蛛网膜下腔压力波峰值同步的方式收缩。手术后，枕骨大孔处CSF通道的直径与术前值相比增加，并且收缩期穿过枕骨大孔的CSF最大流速增加。颈静脉压迫时，压力通过枕骨大孔传递到脊髓蛛网膜下腔是正常的，颈部蛛网膜下腔平均压和脉压降至正常。所有患者的MRI成像上最大空洞直径均减小。电影磁共振成像记录减少速度和流量的空洞流体。所有患者临床症状和体征改善或保持稳定，扁桃体恢复正常形状。与基亚里I型畸形相关的脊髓蛛网膜炎的进展是由小脑扁桃体的作用引起的，小脑扁桃体部分阻塞了枕骨大孔处的蛛网膜下腔，并在部分封闭的脊髓蛛网膜下腔上起到活塞的作用。这产生了扩大的颈部蛛网膜下腔压力波，从外部而不是从内部压迫脊髓，并随着每次心跳向尾部传播空洞液，这导致空洞进展。单纯蛛网膜外减压手术后扁桃体的异常形状和位置消失，提示小脑扁桃体的基亚里I畸形是后天性的，而不是先天性的。手术限于枕下颅骨切除术、C-l椎板切除术和硬脑膜成形术，消除了这种机制，消除了脊髓灰质炎及其进展，而没有更多侵入性手术的风险。
Object. Syringomyelia causes progressive myelopathy. Most patients with syringomyelia have a Chiari I mal formation of the cerebellar tonsils. Determination of the pathophysiological mechanisms underlying the progression of syringomyelia associated with the Chiari I malformation should improve strategies to halt progression of myelopathy.Methods. The authors prospectively studied 20 adult patients with both Chiari I malformation and symptomatic syringomyelia. Testing before surgery included the following: clinical examination; evaluation of anatomy by using T-1-weighted magnetic resonance (MR) imaging; evaluation of the syrinx and cerebrospinal fluid (CSF) velocity and flow by using phase-contrast cine MR imaging; and evaluation of lumbar and cervical subarachnoid pressure at rest, during the Valsalva maneuver, during jugular compression, and following removal of CSF (CSF compliance measurement). During surgery, cardiac-gated ultrasonography and pressure measurements were obtained from the intracranial, cervical subarachnoid, and lumbar intrathecal spaces and syrinx. Six months after surgery, clinical examinations, MR imaging studies, and CSF pressure recordings were repeated. Clinical examinations and MR imaging studies were repeated annually. For comparison, 18 healthy volunteers underwent T-1-weighted MR imaging, cine MR imaging, and cervical and lumbar subarachnoid pressure testing.Compared with healthy volunteers, before surgery, the patients had decreased anteroposterior diameters of the ventral and dorsal CSF spaces at the foramen magnum. In patients, CSF velocity at the foramen magnum was increased, but CSF flow was reduced. Transmission of intracranial pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was partially obstructed. Spinal CSF compliance was reduced, whereas cervical subarachnoid pressure and pulse pressure were increased. Syrinx fluid flowed inferiorly during systole and superiorly during diastole on cine MR imaging. At surgery, the cerebellar tonsils abruptly descended during systole and ascended during diastole, and the upper pole of the syrinx contracted in a manner synchronous with tonsillar descent and with the peak systolic cervical subarachnoid pressure wave. Following surgery, the diameter of the CSF pas sages at the foramen magnum increased compared with preoperative values, and the maximum flow rate of CSF across the foramen magnum during systole increased. Transmission of pressure across the foramen magnum to the spinal subarachnoid space in response to jugular compression was normal and cervical subarachnoid mean pressure and pulse pressure decreased to normal. The maximum syrinx diameter decreased on MR imaging in all patients. Cine MR imaging documented reduced velocity and flow of the syrinx fluid. Clinical symptoms and signs improved or remained stable in all patients, and the tonsils resumed a normal shape.Conclusions. The progression of syringomyelia associated with Chiari I malformation is produced by the action of the cerebellar tonsils, which partially occlude the subarachnoid space at the foramen magnum and act as a piston on the partially enclosed spinal subarachnoid space. This creates enlarged cervical subarachnoid pressure waves that compress the spinal cord from without, not from within, and propagate syrinx fluid caudally with each heartbeat, which leads to syrinx progression. The disappearance of the abnormal shape and position of the tonsils after simple decompressive extraarachnoidal surgery suggests that the Chiari I malformation of the cerebellar tonsils is acquired, not congenital. Surgery limited to suboccipital craniectomy, C-l laminectomy, and duraplasty eliminates this mechanism and eliminates syringomyelia and its progression without the risk of more invasive procedures.