Morota Nobuhito, Ihara Satoshi, Ogiwara Hideki
Division of Neurosurgery, Tokyo Metropolitan Children's Medical Center
Division of Neurosurgery, National Center for Child Health and Development, Tokyo, Japan
J Neurosurg Pediatr. 2017 Apr;19(4):428-439. doi: 10.3171/2016.10.PEDS16247. Epub 2017 Jan 27.
OBJECTIVE Spinal lipomas are generally thought to occur as a result of failed primary neurulation. However, some clinical features cannot be explained by this theory. The authors propose a novel classification of spinal lipomas based on embryonic changes seen during primary and secondary neurulation. METHODS A total of 677 patients with occult spinal dysraphism underwent 699 surgeries between August 2002 and May 2015 at the National Center for Child Health and Development and Tokyo Metropolitan Children's Medical Center. This group of patients had 378 spinal lipomas, including 119 conus spinal lipomas, 27 lipomyelomeningoceles, and 232 filum lipomas, which the authors classified into 4 types based on neural tube formation during embryonic development. Type 1 is defined as pure primary neurulation failure; Type 2 ranges from primary to secondary neurulation failure; Type 3 consists of secondary neurulation failure (early phase); and Type 4 is defined as secondary neurulation failure (late phase). The authors also review embryogenesis in secondary neurulation and analyze the clinical utility of the new classification. RESULTS There were 55 Type 1 spinal lipomas, 29 Type 2, 62 Type 3, and 232 Type 4. All filum lipomas fell into the Type 4 spinal lipoma category. Association with anorectal and/or sacral anomalies was seen in none of the Type 1 cases, 15 (52%) of Type 2, 35 (56%) of Type 3, and 31 (13%) of Type 4. Urogenital anomalies were observed in none of the Type 1 or Type 2 cases, 1 (2%) of Type 3, and 28 (12%) of Type 4. Anomaly syndromes were present in none of the Type 1 cases, 6 (21%) of Type 2, 3 (5%) of Type 3, and 16 (7%) of Type 4. Associated anomalies or anomaly syndromes were clearly observed only for Type 2-4 spinal lipomas encompassing failed secondary neurulation. Radical resection was feasible for Type 1 spinal lipomas. CONCLUSIONS Secondary neurulation of the spinal cord gives rise to the conus medullaris and filum terminale, which are often involved in spinal lipomas. Formation of spinal lipomas seems to be a continuous process overlapping primary and secondary neurulation in some cases. Association with other anomalies was higher in Type 2-4 spinal lipomas, which included failed secondary neurulation, than in Type 1 lipomas, with failed primary neurulation. On the other hand, radical resection was indicated for Type 1, but not for Type 2, spinal lipomas. The new classification of spinal lipomas based on embryonic stage has the potential for clinical use and agrees well with both clinical and surgical findings. The classification proposed here is still preliminary. Further studies and verification are necessary to establish its clinical utility.
目的 脊髓脂肪瘤通常被认为是原发性神经管形成失败的结果。然而，该理论无法解释一些临床特征。作者基于在原发性和继发性神经管形成过程中观察到的胚胎变化，提出了一种新的脊髓脂肪瘤分类方法。方法 2002年8月至2015年5月期间，在国立儿童健康与发展中心和东京都儿童医疗中心，共有677例隐性脊柱裂患者接受了699次手术。该组患者中有378例脊髓脂肪瘤，包括119例圆锥脊髓脂肪瘤、27例脂肪脊髓脊膜膨出和232例终丝脂肪瘤，作者根据胚胎发育过程中的神经管形成将其分为4型。1型定义为单纯原发性神经管形成失败；2型范围从原发性到继发性神经管形成失败；3型由继发性神经管形成失败（早期）组成；4型定义为继发性神经管形成失败（晚期）。作者还回顾了继发性神经管形成中的胚胎发生过程，并分析了新分类方法的临床实用性。结果 有55例1型脊髓脂肪瘤、29例2型、62例3型和232例4型。所有终丝脂肪瘤均属于4型脊髓脂肪瘤类别。1型病例中未发现与肛门直肠和/或骶骨异常相关，2型中有15例（52%）、3型中有35例（56%）、4型中有31例（13%）与之相关。1型和2型病例中均未观察到泌尿生殖系统异常，3型中有1例（2%）、4型中有28例（12%）。1型病例中未出现异常综合征，2型中有6例（21%）、3型中有3例（5%）、4型中有16例（7%）。仅在包括继发性神经管形成失败的2 - 4型脊髓脂肪瘤中清楚地观察到相关异常或异常综合征。1型脊髓脂肪瘤可行根治性切除。结论 脊髓的继发性神经管形成产生脊髓圆锥和终丝，它们常与脊髓脂肪瘤相关。脊髓脂肪瘤的形成在某些情况下似乎是一个与原发性和继发性神经管形成重叠的连续过程。与其他异常相关的情况在包括继发性神经管形成失败的2 - 4型脊髓脂肪瘤中比在原发性神经管形成失败的1型脂肪瘤中更高。另一方面，1型脊髓脂肪瘤适合根治性切除，而2型则不适合。基于胚胎阶段的脊髓脂肪瘤新分类方法具有临床应用潜力，并且与临床和手术结果高度相符。这里提出的分类方法仍属初步。需要进一步的研究和验证来确定其临床实用性。
