Transoral Approach to the Craniocervical Junction (C1–C2)

The transoral approach provides direct midline anterior access to the craniocervical junction from the lower clivus to the C2 body. It is the classic route for irreducible anterior compression at C1–C2, odontoid resection in basilar invagination, and selected tumours. The approach uses a mouth gag retractor, midline split of the posterior pharyngeal wall, and optional soft palate division. The vertebral arteries are the principal danger, lying approximately 2 cm lateral to the midline. All anterior decompressive procedures through this approach destabilise the C1–C2 complex and mandate posterior stabilisation (Harms–Goel or equivalent). Infection risk is elevated due to the contaminated field, and velopharyngeal incompetence is a specific complication of palate splitting.

Primary Indications:

• Irreducible anterior compression at the craniocervical junction (basilar invagination, rheumatoid pannus, tumours)
• Odontoid resection for basilar invagination with ventral cervicomedullary compression
• Selected C1–C2 tumours requiring anterior column access (chordoma, metastasis)
• Chronic irreducible atlantoaxial subluxation with anterior cord compression
• Selected infectious pathology (tuberculous abscess, osteomyelitis) with anterior debridement needs

Why This Approach is Chosen:

The transoral route provides the most direct midline anterior corridor to the lower clivus, anterior arch of C1, odontoid process, and C2 body. No other anterior cervical approach reaches this level without extensive dissection or mandibular swing. The approach is particularly suited to pathology that cannot be reduced posteriorly and requires direct ventral decompression.

Contraindications:

• Patient unable to tolerate prone or sitting position for posterior stabilisation
• Severe trismus or limited mouth opening preventing retractor placement
• Active oral or pharyngeal infection
• Previous high-dose radiotherapy to the pharynx with poor tissue quality
• Isolated posterior pathology better addressed by posterior approaches alone

Alternative Approaches:

• Endoscopic endonasal approach: for purely clival pathology above the palate
• Posterior C1–C2 fusion alone: when anterior compression is reducible
• Lateral extrapharyngeal approach: for selected lateral mass pathology
• Combined anterior-posterior staged procedures: for complex tumours

Bony Anatomy:

The craniocervical junction comprises the occiput, atlas (C1), and axis (C2). The anterior arch of C1 is a thin bony ring with a central tubercle. The odontoid process (dens) projects superiorly from the C2 body and articulates with the anterior arch of C1 and the transverse ligament. The lateral masses of C1 contain the vertebral artery grooves posteriorly. The vertebral artery ascends through the C2 transverse foramen, turns medially in the C1 groove, and enters the foramen magnum.

Pharyngeal Layers:

The posterior pharyngeal wall consists of mucosa, submucosa, superior constrictor muscle, and prevertebral fascia. The retropharyngeal space lies between the pharyngeal constrictors and the prevertebral fascia. The longus colli and longus capitis muscles overlie the anterior longitudinal ligament and vertebral bodies.

Neurovascular Anatomy:

|| Structure | Location | Clinical Significance || ||-----------|----------|----------------------|| || Vertebral artery | Approximately 2 cm lateral to midline at C1–C2 | MOST CRITICAL - injury causes posterior circulation stroke or death || || Anterior spinal artery | Midline anterior to spinal cord | Risk during deep odontoid drilling || || Glossopharyngeal nerve | Lateral in pharyngeal wall | Avoid wide lateral retraction || || Hypoglossal nerve | Lateral above C1 level | At risk with superior extension || || Eustachian tube torus | Lateral pharyngeal wall | Marks safe lateral boundary ||

Soft Palate Anatomy:

The soft palate is a fibromuscular structure separating the nasopharynx from the oropharynx. The levator veli palatini and tensor veli palatini muscles elevate and tense the palate during swallowing. Midline division requires careful layered closure to prevent velopharyngeal incompetence (nasal regurgitation, hypernasal speech).

Deep Internervous Plane:

There is no true internervous plane in the classical sense. The approach is strictly midline through the posterior pharyngeal wall. The superior constrictor muscle is split in the midline raphe, which is a relatively avascular plane. Lateral retraction stays within the safe midline corridor between the vertebral arteries.

Superficial Dissection:

The pharyngeal mucosa and submucosa are incised in the midline. The superior constrictor is divided along the midline raphe. The prevertebral fascia is opened to expose the anterior longitudinal ligament and longus colli muscles. All dissection remains strictly within 1 cm of the midline to avoid the vertebral arteries.

Structures at Risk in Each Layer:

|| Layer | Structure | Protection Strategy || ||-------|-----------|-------------------|| || Mucosal | Pharyngeal vessels | Bipolar coagulation, stay midline || || Muscular | Superior constrictor | Split in midline raphe, limited lateral retraction || || Deep fascial | Longus colli | Subperiosteal elevation, protect medial branches || || Bony | Vertebral artery | Never exceed 1 cm lateral to midline, use anterior tubercle landmark || || Dural | Spinal cord / dura | Protect with Penfield dissectors during odontoid resection ||

Position: Supine with Head Extended and Mouth Open

Pre-positioning Checklist:

• Nasotracheal intubation or tracheostomy for airway access
• Head positioned on Mayfield clamp or horseshoe with slight extension
• Mouth gag retractor (Dingman or Crowe-Davis) prepared
• C-arm or O-arm positioned for lateral fluoroscopy
• Surgeon positioned at head of table
• Microscope or loupes available for deep dissection

Positioning Details:

• Patient supine on radiolucent table
• Head slightly extended (approximately 15–20 degrees) to open the oral corridor
• Mouth opened maximally with gag retractor
• Tongue retracted inferiorly with tongue blade
• Soft palate visualised and marked for split if required
• Posterior pharyngeal wall infiltrated with local anaesthetic with adrenaline

Alternative Positioning:

• Sitting position (rarely used now due to air embolism risk)
• Lateral position for combined anterior-posterior procedures

Key Bony Landmarks:

• Anterior tubercle of C1 - palpable through the posterior pharyngeal wall, central reference point
• Odontoid process - palpated as a bony prominence in the midline
• C2 body - inferior extension palpable
• Lower clivus - superior limit, requires palate split for full visualisation

Key Soft Tissue Landmarks:

• Posterior pharyngeal wall - midline raphe visible as a subtle longitudinal ridge
• Soft palate - superior boundary, split extends exposure
• Torus tubarius (Eustachian tube opening) - lateral limit approximately 2–3 cm from midline
• Uvula - retracted superiorly or divided with palate

Incision Planning:

• Midline vertical incision in posterior pharyngeal wall from C1 tubercle to C2–C3 disc
• Length: 4–6 cm depending on required exposure
• If soft palate split required: curved or straight midline incision in soft palate from uvula to hard palate junction
• Stay strictly within 1 cm of midline at all times

Vertebral Artery Injury Management:

• Immediate tamponade with bone wax or muscle
• Do not attempt primary repair in the transoral field
• Urgent endovascular consultation for possible stenting or sacrifice
• Posterior circulation monitoring in ICU
• Antiplatelet or anticoagulation per protocol

Soft Palate Split:

• Indication: Need for exposure above the C1 arch to the lower clivus
• Technique: Midline or curved incision from uvula to hard palate
• Closure: Three-layer repair (nasal mucosa, muscle, oral mucosa)
• Complication: Velopharyngeal incompetence (10–15 percent)

Mandibulotomy (Rare):

• Indication: Large tumours, limited mouth opening, need for wide lateral exposure
• Technique: Midline mandibular osteotomy with swing
• Morbidity: High (nonunion, nerve injury, prolonged recovery)
• Rarely performed in modern practice due to endoscopic alternatives

Endoscopic-Assisted Transoral:

• Indication: Minimally invasive access, reduced soft tissue trauma
• Technique: Endoscope through mouth with standard retractor
• Advantages: Better visualisation, smaller incision, reduced infection risk
• Limitations: Steep learning curve, equipment requirements

Combined Staged Procedures:

For complex pathology, the transoral approach is combined with posterior C1–C2 fusion (Harms–Goel) in the same sitting or within 48 hours. Single-stage combined anterior-posterior surgery is performed in selected high-volume centres.

Intra-operative Complications:

|| Complication | Prevention | Management || ||--------------|------------|------------|| || Vertebral artery injury | Strict midline, anterior tubercle landmark | Tamponade, endovascular consultation, posterior circulation monitoring || || CSF leak | Careful drilling, dura protection | Dural patch, lumbar drain, watertight pharyngeal closure || || Spinal cord injury | Magnification, Penfield protection | Steroids per protocol, ICU monitoring || || Pharyngeal vessel bleeding | Bipolar coagulation, adrenaline infiltration | Pressure, ligation if accessible ||

Post-operative Complications:

|| Complication | Incidence | Prevention | Treatment || ||--------------|-----------|------------|-----------|| || Infection (pharyngeal / meningitis) | 2–8 percent | Prophylactic antibiotics, watertight closure | IV antibiotics, lumbar drain if CSF leak || || Velopharyngeal incompetence | 10–15 percent with palate split | Meticulous three-layer palate closure | Speech therapy, palatal lengthening or flap if persistent || || CSF leak / pseudomeningocele | 5–10 percent | Dural repair, lumbar drain | Lumbar drainage 5–7 days, re-exploration if persistent || || Airway compromise | Common | Maintain intubation 48–72 hours | Tracheostomy if prolonged, steroids for oedema || || Dysphagia | 20–40 percent transient | Early swallow assessment | Nasogastric feeding, speech therapy || || Vertebral artery stroke | Less than 1 percent | Meticulous technique | Endovascular, antiplatelet, supportive care ||

Immediate Post-operative:

• Maintain nasotracheal tube or tracheostomy for 48–72 hours
• ICU monitoring for airway, neurological status, and CSF leak
• Nasogastric tube for feeding until swallow safe
• Cervical collar or halo for stability until posterior fusion performed
• Prophylactic antibiotics continued for 24–48 hours

Airway Protocol:

• Document cuff leak before extubation
• Steroids to reduce oedema
• Ready access to re-intubation or tracheostomy
• Speech therapy assessment before oral intake

Swallow and Nutrition:

• Videofluoroscopic swallow study or FEES before oral feeding
• Nasogastric or PEG feeding if prolonged dysphagia
• Monitor for nasal regurgitation (velopharyngeal incompetence)

Follow-up Schedule:

• 2 weeks: Wound check, pharyngeal inspection, neurological assessment
• 6 weeks: Flexion-extension radiographs, assess posterior fusion
• 3 months: CT to confirm odontoid resection and fusion
• 6 months: Clinical and radiographic review
• 1 year: Final assessment, consider decannulation if tracheostomy

DVT Prophylaxis:

• LMWH or aspirin per institutional protocol
• Mechanical prophylaxis while immobile

The transoral approach to the craniocervical junction is a specialised technique performed at major spine centres worldwide. Principles are consistent across FRCS, FRACS, EBOT, ABOS, and other examination systems. CT and MRI planning, vertebral artery mapping, and mandatory posterior stabilisation after anterior decompression are near-universal standards.

Side-by-side principles (where guidance converges):

|| Body | Position on craniocervical junction approaches || ||------|---------------------------------------------|| || AO Spine | CT and MRI mandatory for all craniocervical pathology; transoral approach indicated for irreducible anterior compression; posterior stabilisation required after odontoid resection || || NASS / AAOS | Multidisciplinary assessment for complex craniocervical pathology; endoscopic alternatives considered when appropriate; infection prevention protocols emphasised || || BOA / SBNS (UK) | Centralisation of complex craniocervical surgery to specialist centres; combined anterior-posterior expertise required; consent must include velopharyngeal incompetence and CSF leak risks ||

Registry / population evidence:

• Basilar invagination and rheumatoid craniocervical pathology are rare; most series are single-centre retrospective.
• Harms–Goel C1–C2 fusion after transoral decompression achieves greater than 95 percent fusion rates with low morbidity in experienced hands.
• Infection rates of 2–8 percent are reported across series; CSF leak is the strongest predictor of meningitis.

Global practice variation:

In high-resource centres, endoscopic-assisted transoral and purely endoscopic endonasal approaches are increasingly used to reduce soft tissue morbidity. In resource-limited settings, the open transoral approach with meticulous technique remains the standard. Posterior stabilisation is achieved with C1 lateral mass and C2 pedicle screws (Harms–Goel) or transarticular screws (Magerl) depending on local expertise and anatomy.

Consent (globally applicable):

Discuss vertebral artery injury (less than 1 percent but catastrophic), CSF leak (5–10 percent), infection and meningitis (2–8 percent), velopharyngeal incompetence (10–15 percent with palate split), airway compromise requiring prolonged intubation or tracheostomy, dysphagia, and the absolute requirement for posterior stabilisation.