THE airway management of a surgical patient is one of the anesthesiologist’s primary concerns. The combination of several parameters seems to predict difficult lar-yngoscopy and intubation: short thyro-mental distance, protruding incisors, micrognathia, small mouth opening, acromegalic features, short neck, morbid obesity, and others. 1This case report describes another rare and frequently unrecognized physical feature associated with difficult intubation: a mandibular osteoma.
A 54-yr-old man was scheduled to undergo general anesthesia so that biopsy of several areas from the base of the tongue could be performed. His medical history was remarkable for 55 pack/years of smoking, osteoarthritis in his hands and knees, and a remote history of hiatal hernia but no current reflux. Physical examination was unremarkable. His neck was thin, and he appeared to have an adequate thyro-mental distance. There was good mobility of his temporomandibular joint and his cervical spine. His teeth appeared to be in good repair and well aligned, he had a Mallampati class III airway.
We decided to proceed with general anesthesia and to secure the airway with an endotracheal tube to prevent aspiration of blood. We were concerned about the Mallampati class III airway and the presence of a lesion at the base of the tongue, which was described as “suspicious” on computed tomographic scans but appeared not to obstruct the pharyngeal airway. Because all features of the airway examination were normal except for the Mallampati airway classification, we decided to proceed with a modified rapid-sequence induction with alternative airway equipment and a surgeon immediately available in the room.
The patient was preoxygenated for 5 min, and anesthesia was induced with 400 mg thiopental (5.1 mg/kg). Cricoid pressure was applied, and 80 mg succinylcholine was administered after adequate mask ventilation was assured (normal tidal volume, carbon dioxide waveform, and peak inspiratory pressure of 15 mmHg). Laryngoscopy was attempted with a Macintosh no. 4 blade, and a second attempt was made with a Miller no. 2 blade after optimization of the patient’s head position. The epiglottis could not be visualized with either attempt. Mask ventilation was resumed with 100% O2and 2% isoflurane. Another 100-mg dose of thiopental was administered because a slight increase in blood pressure indicated partial recovery from the initial induction dose. Mask ventilation at this point seemed to be more difficult, with peak inspiratory airway pressures between 20 and 25 mmHg. With continued cricoid pressure, laryngoscopy was attempted a third time with the Macintosh no. 4 blade. At this point, only the tip of the epiglottis could be visualized. Because higher inspiratory airway pressures were necessary to maintain adequate mask ventilation, we decided to let the patient recover from his anesthetic induction and perform an awake fiberoptic intubation.
Ten minutes later, with the patient awake and alert, the sequence of events and the changed anesthetic plan was explained to the patient. We then performed an awake nasal fiberoptic intubation after the usual preparations (intravenous antisialagogue, local anesthesia of the pharynx and nasal passages with 4% lidocaine, transtracheal anesthesia and bilateral block of the superior laryngeal branch of the vagus nerve). The fiberoptic intubation was uneventful and proceeded in a timely fashion. The surgical procedure was complicated by the fact that rigid, surgical laryngoscopy was impossible.
After the patient was successfully intubated, we reexamined the airway and discovered prominent, bilateral bony growths extending from the lingual surface of the mandible toward the floor of the mouth. In discussion with the surgeon, we learned that this tumor was an osteoma of the mandible, clearly visible on the preoperative computed tomographic scan (fig. 1). Throughout the surgical procedure, the patient’s vital signs and oxygen saturation remained normal, and his recovery was uneventful.
Osteoma is a benign bone tumor characterized by proliferation of either compact or cancellous bone in an endosteal or periosteal location. The most common location of osteomas is the skull; however, lesions do occur in the jaw. The mandible is more frequently involved, and the most common sites are the lingual aspect of the body, the angle, and the condyle. 2The age at which the lesions are first identified range between 15 and 75 yr, the majority being noticed after the age of 25 yr.
This lesion prevented any displacement of the tongue and the mouth floor and was the reason that direct laryngoscopy was not possible. Biopsy specimens of the tongue base had to be obtained without direct visualization. Osteomas in the maxillofacial region may be associated with limited mouth opening (osteoma of the mandibular condyle) or difficult laryngoscopy 3,4(osteoma of the mandibular body or angle). Unfortunately, there are insufficient demographic data to demonstrate risk factors for this tumor.
This case illustrates that adequate compliance of the tongue and mouth floor is an important prerequisite for rigid laryngoscopy. Decreased motility of this structure may be caused by simple induration, infection, or systemic connective tissue disorders such as mucopolysaccharidoses. Decreased compliance of the mouth floor may not be obvious. The mandibular osteoma described here was not obvious by classically used methods of evaluating the airway.
The anesthesiologist should be aware of the entity because mandibular osteomas can be identified easily by sublingual palpation of the mouth and may have a dramatic impact on laryngoscopy and intubation.