Ch. 23: Craniovertebral Region

• foramen magnum:

  • smaller anterior region has pair of tubercles that alar ligaments attach to
  • posterior portion houses brain stem-spinal cord junction
  • anterolateral aspect contains occipital condyles that articular with C1
• atlas (C1):

  • transverse ligament attaches to pair of tubercles
  • does not have a spinous process
  • increase in potential for CV extension at OA joint
  • transverse foramen houses vertebral artery
• axis (C2):

  • link btw cervical spine proper + CV region
  • spinous process is first palpable structure below the occiput
  • odontoid process (dens) functions as pivot for upper cervical joints + center of rotation of AA joint
• AA joint consists of:

  • 2 lateral facet joints between articular surfaces of inferior articular processes of atlas + superior processes of axis
  • 2 medial joints
  • 1 btw anterior surface of dens + atlas
  • 1 btw posterior surface of dens + hyaline cartilage of transverse ligament
• lateral AA joints function to convery the entire weight of the atlas + head to lower structures
• capsule + accessory capsule ligaments:

  • basiocciput to transverse process of atlas
  • lax to permit maximal motion
  • only moderate support provided during contralateral head rotation
• apical ligament:

  • apex of dens to anterior rim of foramen magnum
  • moderate stabilizer against posterior translation of the dens
• anterior OA membrane:

  • superior continuation of anterior longitudinal ligament
  • connects anterior arch of C1 to anterior aspect of foramen magnum
• posterior OA membrane:

  • continuation of ligamentum flavum
  • connects posterior arch of atlas + posterior aspect of foramen magnum
  • forms part of the posterior boundary of the vertebral canal
• tectorial membrane:

  • occipital bone to axis
  • superior continuation of posterior longitudinal ligament
  • limits upper cervical flexion
  • assists transverse ligament to prevent odontoid ped migration posteriorly into the spinal canal
• alar ligament:

  • posterior lateral aspect of odontoid peg to medial surface of occipital condyles (can also attach to lateral masses of the atlas)
  • provides main passive restraints to contralateral axial rotation + side bending
  • wound around dens during contralateral axial rotation
  • maximally tightened at 90 deg cervical rotation
• insufficiency of the alar ligaments increases the potential for occipitoaxial instabiltiy
• cruciform ligament:

  • transverse portion: lateral masses of atlas to odontoid of axis
  • counteracts anterior translation of atlas relative to axis --> especially during cervical flexon
  • any excessive motion could result in odontoid compressing the spinal cord
• rectus capitis anterior (RCA):

  • anterior aspect of lateral mass of atlas to inferior surface of base of occiput
  • action: flexes + minimally rotates head
  • nerve: ventral rami of C1 + C2
• rectus capitis lateralis:

  • superior surface of C1 transverse process to inferior surface of jugular process of occiput
  • action: side bends head ipsilaterally
  • nerve: ventral rami of C1 + C2
• rectus capitis posterior major:

  • C2 spinous process to spinous process of atlas
  • action:
  • bilateral: extend head
  • unilateral: ipsilateral side bending + rotation
  • nerve: suboccipital nerve
• rectus capitis posterior minor:

  • posterior arch tubercle of atlas to medial part of inferior nuchal line
  • action: extend head + provide minimal support during ipsilateral side bending
  • nerve: suboccipital nerve
• obliquus capitis inferior:

  • spinous process + lamina of axis to transverse process of atlas
  • action: ipsilateral rotation of atlas + control anterior translation + rotation of C1
  • nerve: suboccipital + dorsal rami C1
• obliquus capitis superior:

  • lateral mass of atlas to bone between superior + inferior nuchal lines
  • action:
  • unilateral: contralateral rotation + ipsilateral side bending of OA joint
  • bilateral: extension
  • nerve: suboccipital + dorsal rami C1
• joint disease in the OA region can result in:

  • vertebral artery compromise
  • compression of spinal cord
  • brainstem lesions
• normal flexion to hyperextension of the Atlanta-occipital joint: 15-20 deg
• hypermobility of the OA joint should only be considered if the range of rotation exceeds 8 deg
• within the spine, only two articulations permit pure axial rotation:

  • aa joint
  • thoracolumbar junction
• major motion that occurs at all 3 articulations of the AA joint is axial rotation
• to prevent compression, as the atlas rotates, ipsilateral facet moves posterior + contralateral facet moves anterior
• biconvex nature of the AA joint means cervical flexion + extension create motion in direction opposite of the experienced in the atlas
• when the cervical spine flexes, the atlas extends
• when the cervical spine extends, the atlas flexes
• flexion at AA joint is limited by the tectorial membrane
• extension at the AA joint is limited by the anterior arch of C1 as it makes contact with the odontoid process
• atlantodental interval (ADI): space between the back of anterior arch of atlas + odontoid
• flexion increases ADI
• extension decreases ADI
• increased in ADI can be associated with:

  • increased age
  • history of trauma
  • RA
  • neoplastic disease
  • down syndrome
  • aphasia or dysphasia of dens
• AA side bending to the right is coupled with left rotation
• dizziness associated with disorders of motor function such as clumsiness, weakness, or paralysis could suggest a compromise of vertebrobasilar system
• side view observation should include:

  • cervical curve
  • position of chin relative to chest
  • forward head posture
  • ears - asymmetry in size, shape, + color
• front view observation should include:

  • head position relative to trunk + shoulders
  • level of mastoid process
  • symmetry of cervical soft tissues
  • facial symmetry
  • pupil size + distance apart
• back view observation should include:

  • orientation of head
  • signs of trauma
  • low hairline (Klippel-feil syndrome)
• short neck flexion (AROM):

  • pt instructed to place chin on surface of throat
  • Lhermitter's sign: tingles in the feet or electric shock sensation down the neck
  • common in meningitis + MS
  • tests cranial nerves XI + C1/2 mytomes
  • if no symptoms - PT applies overpressure + tests short neck extensors by asking pt to resist
  • positive: severe pain, nausea, muscle spasm, or cord signs