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Case Reports

Mandibular Tori as a Cause of Inability to Visualize the Larynx

Woods, George M. MD

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In the preoperative assessment of a patient for ease of tracheal intubation, emphasis is placed on the tongue/pharyngeal view [the Mallampati classification [1]], neck range of motion (the "sniffing position"), and the mandibular space [2]. This last factor is evaluated primarily because its length influences how well the laryngeal and pharyngeal axes will coincide during laryngoscopy with the anesthetist's line of vision, a short thyromental distance predicting difficulty. Bellhouse and Dore [3] used lateral neck radiographs to assess the length of the body of the mandible in proven difficult endotracheal intubations and stated that an increase in the anterior-posterior dimension of the tongue relative to the length of the body of the mandible was "one of the variables useful in predicting difficulty of intubation." McIntyre [4] mentioned the need to compress the tongue in order to visualize the larynx and most anesthetists will readily recognize that neck or mandibular soft tissue masses (e.g., abscesses, tumors, hematomas) impede this ability. Less well appreciated is how life-long anatomic variants in the mandibular space may make direct laryngoscopy impossible. Presented here is one such case.

Case Report

The patient, a 78-yr-old male, was diagnosed with unstable angina and two-vessel coronary artery disease. He was scheduled for coronary artery bypass grafting and was first seen by the responsible anesthesiologist the morning of surgery. Physical examination of his airway was notable for normal external anatomy, a beard, a Class II Mallampati view, and extensive bony overgrowth of the floor of his mouth, tori mandibularis Figure 1. The patient said that he had been told to bring these to the attention of the responsible anesthetist. In the operating room while he was breathing oxygen, anesthesia was induced with midazolam and fentanyl and his lungs were ventilated manually while vecuronium was inducing paralysis. Laryngoscopy was attempted with MacIntosh 3, 4 and Miller 2 blades, with head and neck repositioning and external compression, without success. The massive bony overgrowth of the floor of his mouth prevented displacement of his tongue and only the anterior surface of his epiglottis could be seen, elevated slightly off the posterior pharyngeal wall. A 7.0-endotracheal tube was placed via the right nare and guided just posterior to the epiglottis with Magill forceps. Breath sounds and a carbon dioxide tracing were obtained but the endotracheal tube could not be advanced beyond 21 cm at the nare. A tube exchanger was obtained, guided through the endotracheal tube lumen, and the tube then advanced easily over the tube changer. Surgery proceeded uneventfully, and he was taken to the intensive care unit (ICU) tracheally intubated. His trachea was extubated approximately 36 h postoperatively.

F1-37
Figure 1:
Floor of the mouth, patient elevating tongue posteriorly.

Initially the patient did well, but a widened mediastinum on postoperative Day 3 led to concerns about tamponade, and he was taken back to the operating room for exploration. On this occasion after applying local anesthesia, laryngoscopy while the patient was awake was unsuccessful and he was tracheally intubated orally with the aid of a fiberoptic bronchoscope. Postoperatively he was taken back to the ICU with the endotracheal tube still in place and extubated approximately 20 h postoperatively. Within 1 h of extubation signs of progressive respiratory failure were noted. An oral fiberoptic intubation was twice attempted without success. At this time, in response to oximetric saturation descending to 70%, systolic blood pressure of 50 mm Hg on "wide-open neosynephrine and dopamine" (nurse's notes), and a deteriorating heart rate, the cardiothoracic surgeon began an emergent cricothyrotomy. As the cricothyroid membrane was incised, blind nasal intubation was successful, and the neck wound was closed and dressed. At the option of his surgeon, the patient was taken for an elective tracheostomy 10 days later and discharged from the ICU neurologically intact.

Discussion

"Torus mandibularis may be defined as an exostosis, unilaterally or bilaterally, situated on the lingual aspect of the mandible above the mylohyoid line in the region of the pre-molars" [5]. They may be "... caused by the stress of mastication in excess of the capacity of the individual bones, and ... they are effects of the organism to provide additional strengthening to the parts affected" [6]. Studies of the prevalence of mandibular tori are few. The two largest studies surveyed highly restricted populations. Bouquot and Gundlach [7], at an oral cancer screening clinic in Minnesota, found a combined prevalence of mandibular and palatine tori of 27.1/1000 persons, two thirds of which were palatine. Kolas et al. [5] at a general dentistry clinic at Ohio State University, found the prevalence of mandibular tori to be 7.75%, increasing from the first to the third decades of life and leveling off thereafter. The male and female prevalence was approximately even. Although mandibular tori could be single or multiple, unilateral or bilateral, or any combination thereof, by far the most common presentation was single bilateral tori. The highest prevalence of mandibular tori are in Alaskan Eskimos (41.8%) [8] and in Eastern Aleuts (61%) [6]. Cross-sectional surveys demonstrate an increasing incidence of tori from the first through third decade but regrettably there are no data that address the potential for growth over time.

The Grade III laryngeal view encountered in the above case report resulted from the inability to compress or even move the patient's tongue anteriorly because of massive bony overgrowth of the floor of the mouth, the mandibular space. Cormack and Lehane [9], in classifying laryngoscopic views noted that "backward displacement of the tongue can cause intubating difficulties" as was certainly the case here. Blind nasal intubation was successful in the present case but is not without hazard in an operation where the patient is to be fully anticoagulated during the course of surgery. Blind nasal intubation in this case was not easy but was accomplished after the endotracheal tube likely impacted against the anterior laryngeal wall with a technique first suggested by MacIntosh [10] and promulgated by Cormack and Lehane [9].

On postoperative questioning, the patient related that the tori had been present for as long as he could remember and that he had experienced no difficulty with mastication or recent increase in size. He stated that all three of his adult daughters had similar bony obliteration of their mandibular spaces, lending considerable evidence for a genetic component.

In summary, this is a case of difficult endotracheal intubation due to mandibular tori. Although the patient was asymptomatic from these tori (and probably regarded them as a normal condition), elective intubation was difficult and his emergency intubation came very close to ending tragically. It behooves the anesthetist to take these and any space-occupying lesion of the floor of the mouth very seriously.

REFERENCES

1. Mallampati SR, Gatt SP, Gugino LD, et al. A clinical sign to predict difficult tracheal intubation: a prospective study. Can J Anaesth 1985;32:429-34.
2. Benumof J. Management of the difficult adult airway. Anesthesiology 1991;75:1087-110.
3. Bellhouse CP, Dore C. Criteria for estimating likelihood of difficult tracheal intubation with Macintosh laryngoscope. Anaesth Intensive Care 1988;16:329-37.
4. McIntyre JRW. The difficult tracheal intubation. Can J Anaesth 1987;34:204-13.
5. Kolas S, Halperin V, Jefferis K, et al. The occurrence of torus palatinus and torus mandibularis in 2,478 dental patients. Oral Surg Oral Med Oral Pathol 1953;6:1134-41.
6. Moorrees CFA. The dentition as a criterion of race with special reference to the Aleut. J Dent Res 1951;30:815-22.
7. Bouquot J, Gundlach K. Oral exophytic lesion in 23,616 white Americans over 35 years of age. Oral Pathol 1986;62:284-91.
8. Hrdlicka A. Mandibular and maxillary hyperostoses. Am J Phys Anthropol 1940;27:1-67.
9. Cormack RS, Lehane J. Difficult tracheal intubation in obstetrics. Anaesthesia 1984;39:1105-11.
10. MacIntosh SRRH. An aid to oral intubation. BMJ 1949;1:28.
© 1995 International Anesthesia Research Society