A 52-year-old male with ankylosing spondylitis presents for elective lumbar spine fusion. On pre-operative assessment, you anticipate a difficult airway due to severe cervical kyphosis and limited neck extension. Which investigation is most appropriate to guide your airway management strategy?

## Rationale for Investigation Choice **Key Point:** Fibreoptic laryngoscopy is the gold standard investigation for assessing the difficult airway in patients with predicted difficult intubation, particularly those with limited cervical mobility. ### Why Fibreoptic Laryngoscopy? Fibreoptic laryngoscopy provides: 1. **Direct visualization** of the laryngeal inlet and vocal cords under awake conditions 2. **Functional assessment** — demonstrates the degree of glottic opening achievable despite cervical kyphosis 3. **Therapeutic capability** — can be used as the definitive intubation device if difficulty is confirmed 4. **Safety profile** — allows assessment without risk of losing the airway ### Clinical Pearl: **Clinical Pearl:** In ankylosing spondylitis with cervical kyphosis, the cervical spine is rigid and immobile. Fibreoptic intubation allows navigation around the fixed deformity, whereas conventional laryngoscopy (which requires neck extension) would be impossible or dangerous. ### Difficult Airway Assessment Algorithm ```mermaid flowchart TD A[Predicted Difficult Airway]:::outcome --> B{Airway Assessment Complete?}:::decision B -->|No| C[Perform Mallampati, TMD, Thyromental Distance]:::action B -->|Yes| D{High Risk Features Present?}:::decision D -->|Limited neck mobility| E[Fibreoptic Laryngoscopy]:::action D -->|Anatomical deformity| F[Imaging: CT/MRI]:::action E --> G[Awake Fibreoptic Intubation]:::action F --> H[Plan alternative technique]:::action G --> I[Secure airway safely]:::outcome ``` ### High-Yield Comparison Table | Investigation | Utility in AS with Cervical Kyphosis | Therapeutic? | Timing | | --- | --- | --- | --- | | **Fibreoptic Laryngoscopy** | **Excellent** — direct visualization, functional assessment | **Yes** — can intubate | Awake, pre-operative | | Mallampati Score | Poor — assumes neck extension possible | No | Bedside | | CT/MRI Spine | Good — shows anatomy, stenosis | No | Pre-operative | | Ultrasound Neck | Limited — assesses soft tissue only | No | Bedside | ### High-Yield: **High-Yield:** Fibreoptic laryngoscopy is the **investigation of choice** when you suspect difficult intubation AND need both diagnostic and therapeutic capability. It is the standard of care in ankylosing spondylitis with cervical involvement.