1Division of Neurosurgery, Arkansas Children's Hospital; and.
2Department of Neurosurgery, University of Arkansas for Medical Sciences, Little Rock, Arkansas.
J Neurosurg Pediatr. 2020 Oct 2;26(6):671-675. doi: 10.3171/2020.6.PEDS19744. Print 2020 Dec 1.
Chiari malformation type I (CMI) is diagnosed as herniation of the cerebellar tonsils by at least 5 mm below the foramen magnum. However, the degree of tonsillar herniation is a poor predictor of the need for decompression surgery. Exploration for an alternative morphological predictor for surgical intervention could provide greater insight into the development of an appropriate treatment plan for these patients. To investigate this issue, the authors calculated the soft tissue density within the foramen magnum as a measure of impaction of the cerebellar tonsils. Soft tissue density within the foramen magnum and degree of tonsillar herniation were then assessed for their correlation with the need for surgical intervention.
The authors conducted a retrospective, longitudinal chart review of pediatric patients with CMI. Those who had undergone surgical intervention were considered symptomatic and those who had been treated conservatively, as asymptomatic. Soft tissue density was found by dividing the soft tissue occupancy of the foramen magnum (brainstem and cerebellar tonsils) by the total area of the bony foramen magnum. The predictive value of these two measurements for the need of surgery was determined.
Of the 465 patients seen for CMI at the authors' institution between July 1, 2011, and May 31, 2017, 80 underwent surgical intervention and 385 were asymptomatic. The average tissue density was significantly greater in the surgical group than in the asymptomatic group (83.3% and 78.6%, respectively, p < 0.0001). The average tonsillar descent for surgical patients was 10.8 mm compared to 9.8 mm for asymptomatic patients (p = 0.140). The point-biserial correlation coefficient was assessed, and soft tissue density was found to positively correlate with the need for surgical intervention (rpb = 0.199, p = 0.0001), whereas tonsillar herniation did not correlate with the need for surgery (rpb = 0.083, p = 0.115). Additionally, the degree of tonsillar herniation did not correlate with soft tissue density (r = 0.09), indicating that soft tissue density is an independent morphological parameter.
The study findings suggest that the need for surgical intervention in CMI patients is positively correlated with increasing soft tissue density within the foramen magnum, whereas the degree of tonsillar herniation did not show a correlation with the need for surgical intervention. Additionally, soft tissue density is a factor independent of the degree of tonsillar herniation. Further investigation of tissue density within the foramen magnum is needed in the hope of discovering a clinically applicable parameter that would indicate a need for surgical intervention in patients with CMI.
Chiari 畸形 I 型（CMI）被诊断为小脑扁桃体通过至少 5 毫米以下的枕骨大孔疝出。然而，扁桃体疝出的程度是减压手术需求的一个很差的预测指标。寻找替代的形态学预测因子来进行手术干预，可以更深入地了解为这些患者制定适当治疗计划的问题。为了研究这个问题，作者计算了枕骨大孔内的软组织密度，作为小脑扁桃体冲击的测量指标。然后评估枕骨大孔内的软组织密度和扁桃体疝出的程度，以评估它们与手术干预需求的相关性。
作者对患有 CMI 的儿科患者进行了回顾性、纵向图表回顾。接受手术干预的患者被认为是有症状的，而接受保守治疗的患者则被认为是无症状的。软组织密度是通过将枕骨大孔（脑干和小脑扁桃体）的软组织占有率除以骨性枕骨大孔的总面积来确定的。确定了这两个测量值对手术需求的预测价值。
在作者所在机构，2011 年 7 月 1 日至 2017 年 5 月 31 日期间，共有 465 例 CMI 患者就诊，其中 80 例接受了手术干预，385 例为无症状。手术组的平均组织密度明显大于无症状组（分别为 83.3%和 78.6%，p <0.0001）。手术患者的扁桃体下降平均为 10.8 毫米，而无症状患者为 9.8 毫米（p = 0.140）。评估了点双变量相关系数，发现软组织密度与手术干预的需求呈正相关（rpb = 0.199，p = 0.0001），而扁桃体疝出与手术需求不相关（rpb = 0.083，p = 0.115）。此外，扁桃体疝出的程度与软组织密度不相关（r = 0.09），表明软组织密度是一个独立的形态学参数。
研究结果表明，CMI 患者手术干预的需求与枕骨大孔内软组织密度的增加呈正相关，而扁桃体疝出的程度与手术干预的需求没有相关性。此外，软组织密度是一个独立于扁桃体疝出程度的因素。需要进一步研究枕骨大孔内的软组织密度，以期发现一个可用于临床的参数，该参数可以表明 CMI 患者需要手术干预。
