Supplementary Material for: Saccular Limited Dorsal Myeloschisis: A New Indication for Prenatal Surgery? Case Series and Scoping Review

Introduction: Limited dorsal myeloschisis (LDM) is a rare type of closed spinal dysraphism characterized by a fibroneural stalk connecting a midline skin defect to the underlying spinal cord. When saccular, LDM can mimic open spina bifida (OSB) lesions such as myelomeningocele (MMC) in prenatal imaging, potentially leading to misdiagnosis and inappropriate management.
Methods: We retrospectively analyzed eight cases of LDM diagnosed at the Dr. Franco Ravera Zunino Hospital in 2024. Clinical, imaging, surgical, and histopathological data were collected. Three cases were misdiagnosed prenatally as MMC and underwent fetal surgery; four were diagnosed and operated postnatally; one presented signs of sac rupture during gestation and was presumed LDM without histological confirmation.
Results: All seven histologically confirmed LDM cases met the two classical criteria proposed by Pang: a cutaneous midline lesion and a fibroneural stalk confirmed with GFAP-immunopositive neuroglial tissue. Five of the cases exhibited Chiari II malformation (CMII), three had ventriculomegaly, and one required shunting. Motor deficits were observed in four patients, ranging from L2 to L4. Notably, one case initially excluded from fetal surgery due to unclear diagnosis later developed sac rupture and CMII progression.
Conclusion: Our series highlights the need to include LDM in the differential diagnosis of OSB during prenatal evaluations. The differential diagnosis of LDM versus MMC remains a major prenatal challenge, particularly in the saccular form. Further studies are warranted to improve prenatal imaging and diagnostic accuracy.