颅颈部蛛网膜下腔异常在Chiari畸形合并脊髓空洞症发病机制中意义的研究

Alteration of local subarachnoid space in patfaogenesis of Chiari malformation accompanied by syringomyelia

目的探讨颅颈交界区(CCJ)蛛网膜下腔(SS)形态学异常在Chiari畸形合并脊髓空洞症(CM-SM)发病中的作用。方法回顾分析35例CM-SM的磁共振(MR)影像学资料。与20例正常人对照,测量斜坡和枕鳞的长度(DB和IO)、小脑扁桃体下疝程度(ECT)、第Ⅳ脑室底与斜坡延长线的夹角α、颅后窝(PCF)和颅颈交界区(CCJ)及其内SS的容积等形态学指标,分析CM-SM发病机制。结果病例组DB、IO均较对照组明显缩短,小脑扁桃体平均下移8.42 mm,α角平均缩小6.29°,与对照组有显著性差异(P<0.05)。病例组PCF容积测量值均较对照组平均缩小10.24 ml,其中神经组织体积减少不明显(P>0.05)而其内SS容积则缩小25.8％,平均减少了6.05 ml。CCJ区总容积变化不明显,其内神经组织体积增加7.29 ml(16.2％)而SS容积平均减少12.96 ml(63.7％),与对照组比较差异有统计学意义(P<0.01)。表明颅后窝发育过小,使后脑组织向下向前移位,导致整个CCJ区蛛网膜下腔狭窄。结论颅颈部的发育异常是Chiari畸形发病的基础,蛛网膜下腔狭窄在SM发生发展中起重要作用。

Objective To investigate the significance of abnormal subarachnoid space(SS) at craniocervical junction(CCJ) in patients with type I Chiari malformation (CM I) accompanied by syringomyelia(SM) .Methods The magnetic resonance images (MRI) in 35 CM I patients were reviewed. The lengths of clivus and occipital squama, the extent of cerebellar tonsillar hernia, and the angle(α angle) between clivus and floor of the fourth ventricle on the sagital MRI were measured. The volumes of the posterior cranial fossa(PCF), CCJ and SS were calculated by the Cavalieri method. Results Compared with normal control subjects, the findings in the CM I patients consisted of short ene-doccipital squama and clivus,a angle decreased by 6.29° on average,and cerebellar tonsils herniated 8.42 mm below the foramen magnum; the difference was statistically significant ( P < 0.05) .Volumetric calculations for the PCF revealed a significant reduction in total volume (by a mean of 10.24 ml) and a 25.8% reduction in SS volume (by a mesn of 6.05 ml) ,but no significant reduction in nerve tissue(NT) volume. The volumetric calculations for the CCJ region revealed a significant increase in NT volume (by a mean of 7.29 ml) and a 63.7 % reduction of SS volume (by a mean of 12.96 ml), while the total volume was normal. Conclusions The anomalous formations of craniocervical junction are the basic pathogenic factors of Chiari I malformation. The narrowing of subarachnoid space plays an important role in the development of sy-ringomyelia.