Limited Dorsal Myeloschisis: Reconsideration of its Embryological Origin

• Published in: Neurosurgery Vol. 86; no. 1; pp. 93 - 100
• Main Authors: Kim, Joo Whan, Wang, Kyu-Chang, Chong, Sangjoon, Kim, Seung-Ki, Lee, Ji Yeoun
• Format: Journal Article
• Language: English
• Published: United States Oxford University Press 01.01.2020; Copyright by the Congress of Neurological Surgeons; Wolters Kluwer Health, Inc
• Subjects: Care and treatment; Congenital diseases; Development and progression; Embryonic development; Embryos; Health aspects; Neurological disorders; Neurosurgery; Physiological aspects; Prenatal development; Spina bifida; Spinal cord; Spine; South Korea; Embryogenesis; Secondary neurulation; Spinal dysraphism; Limited dorsal myeloschisis
• ISSN: 0148-396X; 1524-4040
• DOI: 10.1093/neuros/nyy632

ABSTRACT BACKGROUND Limited dorsal myeloschisis (LDM) is postulated to be a result of incomplete dysjunction in primary neurulation. However, clinical experience of LDM located below the first-second sacral (S1-S2) vertebral level, which is formed from secondary neurulation (S2-coccyx), suggested that LDM may not be entirely explained as an error of primary neurulation. OBJECTIVE To elucidate the location and characteristics of LDM to investigate the possible relation of its pathoembryogenesis to secondary neurulation. METHODS Twenty-eight patients were surgically treated for LDM from 2010 to 2015. Since the level where the LDM stalk penetrates the interspinous ligament is most clearly defined on the preoperative MRI and operative field, this level was assessed to find out whether the lesions can occur in the region of secondary neurulation. RESULTS Eleven patients (39%) with typical morphology of the stalk had interspinous defect levels lower than S1-S2. These patients were not different from 17 patients with classic LDMs at a level above or at S1-S2. This result shows that other than the low level of the interspinous level, 11 patients had lesions that could be defined as LDMs CONCLUSION By elucidating the location of LDM lesions (in particular, the interspinous level), we propose that LDM may be caused by errors of secondary neurulation. The hypothesis seems more plausible due to the supportive fact that the process of separation between the cutaneous and neural ectoderm is present during secondary neurulation. Hence, incomplete disjunction of the two ectoderms during secondary neurulation may result in LDM, similar to the pathomechanism proposed during primary neurulation.