Difficult direct laryngoscopy in patients with cervical spine disease.

Two hundred and fifty three patients were examined before surgery for cervical spine disease. The grade of glottic visibility was determined at direct laryngoscopy, using the classification proposed by Cormack and Lehane. The overall prevalence of difficulty (grades 3 and 4) was 20%. Patients with disease that includes the occipito-atlanto-axial complex have a higher prevalence of difficulty than those with disease below the axis vertebra. Occipito-atlanto-axial disease is associated with poor mandibular protrusion. The best single predictor of difficulty was reduced separation of the posterior elements of the first and second cervical vertebrae on lateral radiographs. The Mallampati examination was the best single predictor on physical examination. The Mallampati may be an indicator of poor cranio-cervical extension. Difficulty was rare in patients with class A mandibular protrusion, and invariable in patients with class C protrusion.