Surgical Pathoembryology and Treatment of Limited Dorsal Myeloschisis

Abstract

Limited dorsal myeloschisis （ LDM ） , first proposed by Pang et al., is thought to originate from a small segmental failure of the dorsal closure of the neural folds during primary neurulation. The disjunction between the cutaneous and neural ectoderm is impaired at the focal limited nonclosure site. This results in a retained fibroneural stalk linking the skin lesion and the dorsal spinal cord, which results in tethering of the cord. Based on skin manifestations, LDMs were originally categorized as saccular and nonsaccular （ flat ） . Saccular LDM consists of a skin ‒ based cerebrospinal fluid sac topped by a squamous epithelial dome, whereas the flat LDM has a squamous epithelial flat surface or a sunken crater or pit typically called a “ cigarette ‒ burn ” skin lesion. Recently, we reported a human tail ‒ like cutaneous appendage as an additional morphological type of skin lesion. The recommended treatment consisted of prophylactic untethering of the stalk from the cord. Because of the shared origin of LDM and congenital dermal sinus （ CDS ） , CDS elements may be found within the fibroneural LDM stalk with a 10 ‒ 20 ％ possibility. When part of the CDS invested in the intradural stalk is left during untethering surgery, inclusion tumors such as dermoid cysts may develop in the patient. Although the central histopathological finding of LDM stalk is the presence of glial fibrillary acidic protein （ GFAP ）‒ immunopositive neuroglial tissues in the fibrocollagenous tract, immunopositivity for GFAP was observed in 50 ‒ 60 ％ of pathologically examined cases. The presence of neural crest cells, such as peripheral nerve fibers and melanocytes, also assists in the histopathological diagnosis of LDM. In this case report, the diagnostic and surgical strategies of LDM are discussed accord-ingly.