The suboccipital ligament

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OBJECTIVE

A fibrous structure located dorsal to the dura at the posterior craniocervical junction stretches horizontally between the bilateral occipital condyles and the upper borders of the C-1 laminae. Partially covered by the occipital bone, this structure is always encountered when the bone is removed from the foramen magnum rim during approaches to the posterior cranial fossa. Although known to surgeons, this structure has not been defined, studied, or named. The most appropriate name for this structure is “the suboccipital ligament,” and a detailed rationale for this name is provided.

METHODS

This 3-year-long study included 10 cadaveric specimens and 39 clinical patients: 31 consecutive surgically treated patients with Chiari Type I malformations (CM-I subgroup) and 8 other patients with posterior fossa pathologies (non–CM-I subgroup). The dimensions were defined, the function of this ligament was hypothesized, size and histological composition were compared between patient subgroups, and its origin and relationship to the surrounding structures were analyzed. Possible statistical differences in the parameters between the 2 groups were also evaluated.

RESULTS

The suboccipital ligament consists of horizontally oriented hyaline fibers and has a median length of 35 mm, height of 10 mm, and thickness of 0.5 mm. These dimensions are not significantly different between the CM-I and non–CM-I patients. The median age of the patients was 43 years, with CM-I patients being significantly younger (median 35 years) than non–CM-I patients (median 57 years). There was no statistically significant difference in weight, height, and body mass index between patient subgroups. There was no significant correlation between the body mass index or height of the patients and the dimensions of the ligament. No statistically significant differences existed between the subgroups in terms of smoking history, alcohol consumption, and the presence of diabetes mellitus, hypertension, hydrocephalus, or headaches. The ligament tissue in the CM-I patients was disorganized with poorly arranged collagen bands and interspersed adipose tissue. These patients also had more hyalinized fibrosis and showed changes in the direction of fibers, with hyaline nodules ranging from 0 to 2+. The result of the histological evaluation of the suboccipital ligament for hyaline nodules, calcification, and ossification was graded as 2+ if present in 3 or more medium-power magnification fields (MPFs); 1+ if present in 1–2 MPFs; and 0, if present in less than 1 MPF. Histological examination of the ligaments showed structural differences between CM-I and non–CM-I patients, most notably the presence of hyaline nodules and an altered fiber orientation in CM-I patients.

CONCLUSIONS

The suboccipital ligament extends between the occipital condyle and the superior edge of the C-1 lamina, connecting the contralateral sides, and appears to function as a real ligament. It is ventral to the occipital bone, which covers approximately two-thirds of the height of the ligament and is loosely attached to the dura medially and more firmly laterally. Because of its distinctive anatomy, characteristics, and function, the suboccipital ligament deserves its own uniform designation and name.

ABBREVIATIONS BMI = body mass index; CM-I = Chiari malformation Type I; MPF = medium-power magnification field.

Article Information

Correspondence Kenan I. Arnautovic, Semmes-Murphey Clinic, 6325 Humphreys Blvd., Memphis, TN 38120. email: kenanarnaut@yahoo.com.

INCLUDE WHEN CITING Published online April 14, 2017; DOI: 10.3171/2016.10.JNS162161.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

  • View in gallery

    Non–CM-I patient. Intraoperative photograph of the suboccipital ligament (arrows). Note the posterior cranial fossa and spinal dura (D), C-1 postlaminectomy edge (C1), and C-2 spinous process (C2). Figure is available in color online only.

  • View in gallery

    CM-I patient. A: Intraoperative photograph of the suboccipital ligament (arrows). Before removing the occipital bone (B), the lower part of the ligament is not covered by bone (arrows) and spinal dura (D). B: The same patient after the bone has been removed. The suboccipital ligament is now completely uncovered (arrows). The suboccipital ligament superior or condylar (SB) and inferior atlantal branches (IB), posterior fossa and spinal dura (D), post–C-1 laminectomy edge (C1), and C-2 spinous process (C2) are shown. C: In the same patient, the right side of the ligament is shown at higher magnification. Figure is available in color online only.

  • View in gallery

    Artistic rendering of the suboccipital ligament. A: Before removing the occipital bone. B: After the occipital bone is removed. C: Sagittal view of the same area on the right side. C0 = occiput; PAOM = posterior atlantooccipital membrane; RCPMi = rectus capitis posterior minor muscle. Copyright Ron Tribell. Published with permission.

  • View in gallery

    Non–CM-I patient with a posterior fossa meningioma. A: Collagenous connective tissue of the suboccipital ligament and longitudinal section, including the adipose tissue. The fibers are roughly parallel. H & E stain, original magnification ×40 magnification. B: Medium-power magnification of the longitudinal section of the collagenous tissue also demonstrating the parallel nature of the fibers. H & E stain, original magnification ×200. C: A longitudinal section of the collagenous tissue. Masson's trichrome stain (original magnification ×200) highlights the parallel nature of the fibers. D: A cross-section of collagenous tissue–containing capillaries. H & E stain, original magnification ×400. Figure is available in color online only.

  • View in gallery

    CM-I patient. A: Longitudinal section of the collagenous connective tissue of the suboccipital ligament. The collagen is interspersed with adipose tissue. Low-power magnification suggests some degree of change in the orientation of the collagenous fibrous tissue. H & E stain, original magnification ×40. B: Medium-power magnification of a longitudinal section of collagen tissue of the occipital ligament. The collagen exhibits some directional change in the fibers. H & E stain, original magnification ×200. C: Masson's trichrome stain (original magnification ×200) of the longitudinal section highlighting the directional change of the collagenous fibers. D: A cross-section of collagenous fibrous tissue. H & E stain, original magnification ×400. E: Hyaline nodule (asterisk). The arrows indicate the nodule interface. H & E stain, original magnification ×40). F: Hyaline nodule (asterisk). The arrows indicate the nodule interface. H & E stain, original magnification ×100. G: Masson's trichrome stain (original magnification ×40) highlights the same nodule (asterisk). Figure is available in color online only.

References

  • 1

    Alden TDOjemann JGPark TS: Surgical treatment of Chiari I malformation: indications and approaches. Neurosurg Focus 11:1E22001

  • 2

    Anderson RCEmerson RGDowling KCFeldstein NA: Improvement in brainstem auditory evoked potentials after suboccipital decompression in patients with Chiari I malformations. J Neurosurg 98:4594642003

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 3

    Arnautovic ASplavski BBoop FAArnautovic KI: Pediatric and adult Chiari malformation Type I surgical series 1965–2013: a review of demographics, operative treatment, and outcomes. J Neurosurg Pediatr 15:1611772015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 4

    Arnautović KIal-Mefty OPait TGKrisht AFHusain MM: The suboccipital cavernous sinus. J Neurosurg 86:2522621997

  • 5

    Arnautovic KIMuzevic DSplavski BBoop FA: Association of increased body mass index with Chiari malformation Type I and syrinx formation in adults. J Neurosurg 119:105810672013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 6

    Arora PBehari SBanerji DChhabra DKJain VK: Factors influencing the outcome in symptomatic Chiari I malformation. Neurol India 52:4704742004

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 7

    Aydin SHanimoglu HTanriverdi TYentur EKaynar MY: Chiari type I malformations in adults: a morphometric analysis of the posterior cranial fossa. Surg Neurol 64:2372412005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 8

    Badie BMendoza DBatzdorf U: Posterior fossa volume and response to suboccipital decompression in patients with Chiari I malformation. Neurosurgery 37:2142181995

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 9

    Banerji NKMillar JH: Chiari malformation presenting in adult life. Its relationship to syringomyelia. Brain 97:1571681974

  • 10

    Bell WOCharney EBBruce DASutton LNSchut L: Symptomatic Arnold-Chiari malformation: review of experience with 22 cases. J Neurosurg 66:8128161987

  • 11

    Caldarelli MNovegno FVassimi LRomani RTamburrini GDi Rocco C: The role of limited posterior fossa craniectomy in the surgical treatment of Chiari malformation Type I: experience with a pediatric series. J Neurosurg 106:3 Suppl1871952007

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 12

    Chauvet DCarpentier AGeorge B: Dura splitting decompression in Chiari type 1 malformation: clinical experience and radiological findings. Neurosurg Rev 32:4654702009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 13

    Dean NAMitchell BS: Anatomic relation between the nuchal ligament (ligamentum nuchae) and the spinal dura mater in the craniocervical region. Clin Anat 15:1821852002

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 14

    Di X: Endoscopic suboccipital decompression on pediatric Chiari type I. Minim Invasive Neurosurg 52:1191252009

  • 15

    Eicker SOMende KCDührsen LSchmidt NO: Minimally invasive approach for small ventrally located intradural lesions of the craniovertebral junction. Neurosurg Focus 38:4E102015

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 16

    Eisenstat DDBernstein MFleming JFVanderlinden RGSchutz H: Chiari malformation in adults: a review of 40 cases. Can J Neurol Sci 13:2212281986

  • 17

    Erdogan ECansever TSecer HITemiz CSirin SKabatas S: The evaluation of surgical treatment options in the Chiari malformation type I. Turk Neurosurg 20:3033132010

    • PubMed
    • Search Google Scholar
    • Export Citation
  • 18

    Godil SSParker SLZuckerman SLMendenhall SKMcGirt MJ: Accurately measuring outcomes after surgery for adult Chiari I malformation: determining the most valid and responsive instruments. Neurosurgery 72:8208272013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 19

    Goel ABhatjiwale MDesai K: Basilar invagination: a study based on 190 surgically treated patients. J Neurosurg 88:9629681998

  • 20

    Gray HWarwick RWilliams PL: Gray's Anatomy ed 36PhiladelphiaSaunders1980

  • 21

    Klekamp J: Surgical treatment of Chiari I malformation—analysis of intraoperative findings, complications, and outcome for 371 foramen magnum decompressions. Neurosurgery 71:3653802012

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 22

    Kotil KTon TTari RSavas Y: Delamination technique together with longitudinal incisions for treatment of Chiari I/syringomyelia complex: a prospective clinical study. Cerebrospinal Fluid Res 6:72009

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 23

    Litvack ZNLindsay RASelden NR: Dura splitting decompression for Chiari I malformation in pediatric patients: clinical outcomes, healthcare costs, and resource utilization. Neurosurgery 72:9229292013

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 24

    Massimi LCaldarelli MPaternoster GNovegno FTamburrini GDi Rocco C: Miniinvasive surgery for Chiari type I malformation. Neuroradiol J 21:65702008

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 25

    Nakamura NIwasaki YHida KAbe HFujioka YNagashima K: Dural band pathology in syringomyelia with Chiari type I malformation. Neuropathology 20:38432000

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 26

    Nash LNicholson HLee ASJohnson GMZhang M: Configuration of the connective tissue in the posterior atlanto-occipital interspace: a sheet plastination and confocal microscopy study. Spine (Phila Pa 1976) 30:135913662005

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 27

    Park JKGleason PLMadsen JRGoumnerova LCScott RM: Presentation and management of Chiari I malformation in children. Pediatr Neurosurg 26:1901961997

  • 28

    Paul KSLye RHStrang FADutton J: Arnold-Chiari malformation. Review of 71 cases. J Neurosurg 58:1831871983

  • 29

    Romero FRPereira CA: Suboccipital craniectomy with or without duraplasty: what is the best choice in patients with Chiari type 1 malformation?. Arq Neuropsiquiatr 68:6236262010

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 30

    Sala FSquintani GTramontano VCoppola AGerosa M: Intraoperative neurophysiological monitoring during surgery for Chiari malformations. Neurol Sci 32:Suppl 3S317S3192011

    • Search Google Scholar
    • Export Citation
  • 31

    Scali FPontell MEEnix DEMarshall E: Histological analysis of the rectus capitis posterior major's myodural bridge. Spine J 13:5585632013

  • 32

    Schut LBruce DA: The Arnold-Chiari malformation. Orthop Clin North Am 9:9139211978

  • 33

    Smith JRidley A: Cerebellar ectopia presenting in adult life. BMJ 1:3533551969

  • 34

    Stovner LJBergan UNilsen GSjaastad O: Posterior cranial fossa dimensions in the Chiari I malformation: relation to pathogenesis and clinical presentation. Neuroradiology 35:1131181993

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 35

    Takayasu MTakagi THara MAnzai M: A simple technique for expansive suboccipital cranioplasty following foramen magnum decompression for the treatment of syringomyelia associated with Chiari I malformation. Neurosurg Rev 27:1731772004

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 36

    Tubbs RSBeckman JNaftel RPChern JJWellons JC IIIRozzelle CJ: Institutional experience with 500 cases of surgically treated pediatric Chiari malformation Type I. J Neurosurg Pediatr 7:2482562011

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 37

    Tubbs RSWellons JC IIIOakes WJBlount JP: Reformation of the posterior atlanto-occipital membrane following posterior fossa decompression with subsequent constriction at the craniocervical junction. Pediatr Neurosurg 38:2192212003

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 38

    Vanaclocha VSaiz-Sapena NGarcia-Casasola MC: Surgical technique for craniocervical decompression in syringomyelia associated with Chiari type I malformation. Acta Neurochir (Wien) 139:5295401997

    • Crossref
    • Search Google Scholar
    • Export Citation
  • 39

    Vega AQuintana FBerciano J: Basichondrocranium anomalies in adult Chiari type I malformation: a morphometric study. J Neurol Sci 99:1371451990

  • 40

    Yundt KDPark TSTantuwaya VSKaufman BA: Posterior fossa decompression without duraplasty in infants and young children for treatment of Chiari malformation and achondroplasia. Pediatr Neurosurg 25:2212261996

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 41

    Zamel KGalloway GKosnik EJRaslan MAdeli A: Intraoperative neurophysiologic monitoring in 80 patients with Chiari I malformation: role of duraplasty. J Clin Neurophysiol 26:70752009

    • Crossref
    • PubMed
    • Search Google Scholar
    • Export Citation
  • 42

    Zhou DBZhao JZZhang DZhao YL: Suboccipital bony decompression combined with removal of the dural band as treatment for Chiari I malformation. Chin Med J (Engl) 117:127412772004

    • PubMed
    • Search Google Scholar
    • Export Citation

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