Rudimentary Meningocele: Remnant of a Neural Tube Defect?

Abstract

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 im-munohistochemistry 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.

A Case of Rudimentary Lateral Parietal Cephalocele: Extracranial Meningothelial and Glial Tissue without Intracranial Communication or Bony Defect

“…Last, unlike classic cephaloceles, our patient had no evidence of cerebral malformation on MRI. As previously proposed in the literature, this observation suggests that rudimentary cephalocele pathogenesis represents either an early or minor deviation in embryology that is not significant enough to distort the subsequent development of the central nervous system [6, 13]. …”

Completely Intraosseous Atretic Meningocele

“…The skin may be alopecic or excessively hairy and a ‘hair collar’ sign surrounding the lesion may be present [3, 4, 13]. Furthermore, the skin may be thinned, scar-like, angiomatous, or pigmented [3, 4].…”

Neurogenic Tumors of Soft Tissue

“…One tissue type generally predominates, but rare examples display a combination of mesenchymal and neuroectodermal elements [58,[62][63][64][65][66][67][68][69]. The term hamartoma with ectopic meningothelial elements has been used to describe unusual cases consisting of a disorganized mixture of abnormally thickened blood vessels, peripheral nerves, adipose tissue, smooth muscle bundles, and/or cutaneous adnexa in addition to ectopic meningothelial and neural elements [57,58,65,67,68,70,71].…”

“…Rarely, small foci of entrapped, degenerated, or necrotic glia can be highlighted by a GFAP stain [55,57]. Meningothelial cells are characterized ultrastructurally by copious intracytoplasmic intermediate filaments, interdigitating cell membranes, and numerous desmosomes, but they lack external lamina [91].…”