Tethering tracts in spina bifida occulta: revisiting an established nomenclature

Restricted access

Object

The goal of the present study goal was to systematically confirm the previously recognized nomenclature for tethering tracts that are part of the spectrum of occult spinal dysraphic lesions.

Methods

The tethering tract in 20 patients with spina bifida occulta underwent histological examination with H & E staining and epithelial membrane antigen (EMA) immunolabeling, and additional selected specimens were stained with Masson trichrome.

Results

All tethering tracts contained fibrous connective tissue. Four tracts were lined with epithelial cells and either originated within a dermoid cyst, terminated at a skin dimple/sinus opening, or had both of these characteristics. No tethering tracts exhibited EMA positivity or meningeal elements. Although all tethering tracts originated in juxtaposition to the spinal cord, their termination sites were variable.

Conclusions

Based on histological findings and presumed embryological origin, the authors broadly classified tethering tracts terminating within the dura mater, epidural space, or lamina as “short tethering tracts” (STTs). The STTs occurred mostly in conjunction with split cord malformations and had a purely fibrous composition. Tethering tracts terminating superficial to the overlying lamina were classified as “long tethering tracts” (LTTs), and the authors propose that these are embryologically distinct from STTs. The LTTs were of two varieties: epithelial and nonepithelial, the former being typically associated with a skin dimple or spinal cord (epi)dermoid cyst. In fact, analysis of the data suggested that not every tethering tract terminating in or on the skin should be classified as a dermal sinus tract without histological confirmation, and because no evidence of meningeal tissue–lined tracts was detected, the use of the term “meningocele manqué” may not be appropriate.

Abbreviations used in this paper:DST = dermal sinus tract; EMA = epithelial membrane antigen; LTT = long tethering tract; MM = meningocele manqué; MR = magnetic resonance; SBO = spina bifida occulta; SCM = split cord malformation; STT = short TT; UAB = University of Alabama at Birmingham; UWMS = University of Wisconsin Medical School.

Article Information

Address reprint requests to: Bermans J. Iskandar, M.D., Department of Neurosurgery, University of Wisconsin Hospitals and Clinics, 600 Highland Avenue, Madison, Wisconsin 53792. email: iskandar@neurosurg.wisc.edu.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Diagram demonstrating the tethering tract origin (values depicted on the left of the canal) and tract termination (values on the right of the canal) for all 20 patients. Sixteen tracts originated in the spinal cord, three in a dermoid cyst, and one in adipose tissue surrounding the cord. Nine tracts terminated at the skin, seven on the dorsal dura mater, one within the epidural space, and three on the deep surface of the lamina. Percentages in parentheses reflect the fraction of the entire population.

  • View in gallery

    Histological studies. Left: Low-magnification photomicrograph of a dermal sinus tract sectioned along its long axis revealing the overlying skin (arrows) and an intradermal and subcutaneous cyst (asterisk) containing amorphous proteinacious material. Right: Higher-magnification photomicrograph of tissue obtained along the cyst lining demonstrating ciliated epithelium (arrows). H & E.

  • View in gallery

    Proposed tethering tract classification scheme. Tethering tracts originating from the spinal cord and terminating within the dura mater, epidural space, or lamina can be defined as STTs, are usually associated with SCMs, and probably represent byproducts of the embryological error that forms the split. Tethering tracts traveling from the spinal cord to the overlying skin can be classified as LTTs and seem to be embryologically distinct from STTs. The LTTs are further subdivided based on the presence or absence of epithelial elements and probably result from an error either early or late during nondysjunction.

  • View in gallery

    Artist's depiction of STTs. Note the presence of an associated SCM with several tethering tracts to the overlying dura or lamina.

  • View in gallery

    Artist drawings of various subtypes of epithelial LTTs. Left: Tethering tract containing epithelial cells originating at the spinal cord and terminating at the skin, with associated hypertrichosis. Right: Tethering tract originating from a spinal epidermoid cyst and terminating on the overlying skin.

  • View in gallery

    Artist drawing of a nonepithelial LTT. Tethering tract originating at the spinal cord and terminating in the overlying skin but containing no epithelial elements.

  • View in gallery

    Our hypothetical model for the presumed error or repair mechanism that occurs early or late in the continuum of dysjunction. Those that occur early may explain the presence of DSTs or epithelial tracts, whereas those occurring late may result in nonepithelial tethering tracts. The key difference therefore may lie in the timing of the error rather than its type. The ultimate appearance of the tethering tract from nondysjunction depends significantly on the embryo's ability to recognize and repair the tethering tract.

References

  • 1

    Ackerman LLMenezes AH: Spinal congenital dermal sinuses: a 30-year experience. Pediatrics 112:6416472003

  • 2

    Ackerman LLMenezes AHFollett KA: Cervical and thoracic dermal sinus tracts. A case series and review of the literature. Pediatr Neurosurg 37:1371472002

    • Search Google Scholar
    • Export Citation
  • 3

    Boyd HR: Iatrogenic intraspinal epidermoid. Report of a case. J Neurosurg 24:1051071966

  • 4

    Dias MSMcLone DGNormal and abnormal early development of the nervous system. McLone DG: Pediatric Neurosurgery: Surgery of the Developing Nervous System ed 4.PhiladelphiaWB Saunders2001. 3171

    • Search Google Scholar
    • Export Citation
  • 5

    French BN: The embryology of spinal dysraphism. Clin Neurosurg 30:2953401983

  • 6

    Halcrow SJCrawford PJCraft AW: Epidermoid spinal cord tumor after lumbar puncture. Arch Dis Child 60:9789791985

  • 7

    Iskandar BJOakes WJOccult spinal dysraphism. Albright ALPollack IFAdelson PD: Principles and Practice of Pediatric Neurosurgery New YorkThieme1999. 321351

    • Search Google Scholar
    • Export Citation
  • 8

    James CCMLassman LP: [Spina Bifida Occulta: Orthopaedic Radiological and Neurosurgical Aspects.] LondonAcademic Press1981

  • 9

    Jindal AMahapatra AK: Spinal congenital dermal sinus: an experience of 23 cases over 7 years. Neurol India 49:2432462001

  • 10

    Kaffenberger DAHeinz EROakes WJBoyko O: Meningocele manqué: radiologic findings with clinical correlation. AJNR Am J Neuroradiol 13:108310881992

    • Search Google Scholar
    • Export Citation
  • 11

    Kanev PMPark TS: Dermoids and dermal sinus tracts of the spine. Neurosurg Clin N Am 6:3593661995

  • 12

    Martinez-Lage JFEsteban JAPoza MCasas C: Congenital dermal sinus associated with an abscessed intramedullary epidermoid cyst in a child: case report and review of the literature. Childs Nerv Syst 11:3013051991

    • Search Google Scholar
    • Export Citation
  • 13

    O'Rahilly RMeyer DB: The timing and sequence of events in the development of the human vertebral column during the embryonic period proper. Anat Embryol 157:1671761979

    • Search Google Scholar
    • Export Citation
  • 14

    Pang D: Split cord malformation. Part II: clinical syndrome. Neurosurgery 31:4815001992

  • 15

    Pang D: Ventral tethering in split cord malformation. Neurosurg Focus 10:1E62001

  • 16

    Pang DDias MSAhab-Barmada M: Split cord malformation. Part I: a unified theory of embryogenesis for double spinal cord malformations. Neurosurgery 31:4514801992

    • Search Google Scholar
    • Export Citation
  • 17

    Tubbs RSMcGirt MJWarder DEOakes WJ: Neurological presentation and long-term outcome following operative intervention in patients with meningocele manqué. Br J Neurosurg 17:2302332003

    • Search Google Scholar
    • Export Citation
  • 18

    van der Meulen WDHoving EWStaal-Schreinemacher ABegeer JH: Analysis of different treatment modalities of tethered cord syndrome. Childs Nerv Syst 18:5135172002

    • Search Google Scholar
    • Export Citation

Cited By

Metrics

Metrics

All Time Past Year Past 30 Days
Abstract Views 177 177 15
Full Text Views 89 89 2
PDF Downloads 79 79 0
EPUB Downloads 0 0 0

PubMed

Google Scholar