Rudimentary meningocele: remnant of a neural tube defect?

BACKGROUND Rudimentary meningocele, a malformation in which meningothelial elements are present in the skin and subcutaneous tissue, has been described in the past under a variety of different terms and has also been referred to as cutaneous meningioma. There has been debate as to whether rudimentary meningocele is an atretic form of meningocele or results from growth of meningeal cells displaced along cutaneous nerves OBJECTIVE We reviewed the clinical, histological, and immunohistochemical characteristics of rudimentary meningocele in an attempt to assess the most likely pathologic mechanism for it. DESIGN Retrospective study. SETTING University hospitals. PATIENTS Thirteen children with rudimentary meningocele. MAIN OUTCOME MEASURES Medical records were reviewed and histopathologic examination as well as immunohistochemistry studies were performed for each case. A panel of immunoperoxidase reagents (EMA, CD31, CD34, CD57, S-100, and CAM 5.2) was used to assess lineage and to confirm the meningothelial nature of these lesions. RESULTS Recent evidence indicating a multisite closure of the neural tube in humans suggests that classic meningocele and rudimentary meningocele are on a continuous spectrum. CONCLUSION Rudimentary meningocele seems to be a remnant of a neural tube defect in which abnormal attachment of the developing neural tube to skin (comparable to that in classic meningocele) could explain the presence of ectopic meningeal tissue. In the majority of cases, no underlying bony defect or communication to the meninges could be detected. However, in light of the probable pathogenesis, imaging studies to exclude any communication to the central nervous system should precede any invasive evaluation or intervention.