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True, True—But How Related? Bony Necrosis and Sequestration in the Mandible After Endotracheal Intubation

Fisher, Quentin A., MD

doi: 10.1213/ANE.0b013e3181e75d82
Editorials: Editorials
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From the Department of Anesthesia, Medstar Washington Hospital Center, Washington, DC.

Dr. Fisher is Professor of Anesthesia and Pediatrics at Georgetown University School of Medicine.

Disclosure: The author reports no conflicts of interest.

Address correspondence and reprint requests to Quentin A. Fisher, MD, Department of Anesthesia, Medstar Washington Hospital Center, 110 Irving St., NW, Washington, DC 20010-2975. Address e-mail to quentin.fisher@verizon.net.

Accepted May 6, 2010

The most troublesome form of not knowing something is not even knowing what one does not know. Is it possible that an anesthetic complication that so plainly declares itself as an oral ulceration with severe pain for several weeks, followed by necrosis and sloughing of bone, should have escaped notice by anesthesiologists before? In this issue of Anesthesia & Analgesia, a group of anesthesia and dental practitioners report 4 patients who, within weeks after an anesthetic requiring an endotracheal tube, presented with severe oral pain caused by exposed bone in the posterior mandible.1 All patients developed bony sequestra that were easily dislodged, whereupon healing was prompt and uneventful. Trauma during airway management was suspected because of several characteristics shared among the patients. All had endotracheal intubation as part of their management in the preceding weeks, all lesions occurred at a particularly vulnerable area, where thin mucosa overlies the mylohyoid ridge on the lingual surface, and all lesions were right sided, in what could easily have been the pathway of a laryngoscope blade, tracheal tube, or oral airway.

Although this has heretofore not been reported as an anesthetic complication, focal osteonecrosis of the mandible with development of a bony sequestrum is well known to our dental/oral surgical colleagues.2,3 The mylohyoid ridge is a bony prominence on the lingual surface of the mandible overlaid by a thin mucosa. It is considered particularly vulnerable to injury because of the ridge's prominence and the mucosal fragility. Occasionally, patients might also have a torus, which is also susceptible. Because the periosteum provides a substantial fraction of the blood supply to the underlying bone, trauma to the soft tissue may promote a cascade of events leading to avascular necrosis of the underlying bone segment, eventually demarcating and sloughing as a sequestrum. Known predisposing elements include localized trauma, viral infection, aphthous stomatitis,4 radiation therapy, and medications that inhibit angiogenesis such as bevacizumab, and bisphosphonates.5 Those lesions resulting from radiation or bisphosphonate therapy tend to have poorer demarcation, and more complications6 than the discrete sequestra described by Almazrooa et al.1

How could a relationship to laryngoscopy have gone unnoticed? Possible explanations are that (1) the complication is rare, (2) it usually goes unnoticed by patients followed by spontaneous resolution, (3) it is only coincidentally but not causally related to anesthesia care, or (4) the association has simply failed observation by patients and practitioners. Are any of these possibilities credible? Certainly, with only an anecdotal report of 4 cases, it is impossible to estimate the incidence related to anesthetic management. Given the severe pain reported by patients, it is unlikely that it would go unnoticed. However, seemingly “spontaneous” cases have been described2,3 (albeit, in the references cited, with little attention to detailed medical history). An informal survey of several of my oral surgeon colleagues indicated that the lesion is not uncommon in a busy oral surgery practice and is seen by individual practitioners 20 to 25 times per year (D. Ross, DDS, and R. Emery, DDS, personal communications). In most cases, they report, the antecedent injury is seemingly trivial, such as irritation from a sharp food item, or mucosal injury after dental work. The oral surgeons also estimated few of those patients had recently undergone other surgical procedures. Thus, the most plausible explanation is the last one; that if a relationship does exist, practitioners have simply not noticed an association before. How could that be? The lesion starts with a mucosal injury itself that may be disregarded or completely unnoticed. The denuded bone is itself painless, but pain intensifies as gingival inflammation and ulceration evolve. By the time patients present to their dentists, a relationship to antecedent surgery may no longer be considered.

Developing a confirmed link between 2 temporally distant events requires creative and collaborative thinking between disciplines to recognize unapparent relationships, and to exclude others that are plausible but unproven. Such misattributions have been common in medical epidemiology, often with medicolegal consequences.79 For example, for many years it was presumed that a postoperative ulnar nerve injury was prima facie evidence of harmful intraoperative positioning. Only careful prospective study10 showed it most frequently developed several days postoperatively. Patients have often pursued lawsuits alleging the injury was evident immediately upon recovery, even when careful documentation revealed it was not.9,10

The lesson from the neuropathy chronicle is one of caution. Although the 4 patients described by Almazrooa et al. had similar lesions temporally related to anesthesia, and anesthetic management can be plausibly implicated, it is not yet certain that there is a causal relationship. Just as Warner et al.11 found that nonsurgical hospitalized patients also developed ulnar neuropathy, we too need to know more about the “spontaneous” cases of osteonecrosis unrelated to surgery. Could those patients have incurred unnoticed trauma to the gingiva? Had their dentists overlooked a recent surgical history? Could the current series of patients have also incurred a minor traumatic lesion unrelated to the anesthetic? Until we have a careful prospective quest for the lesion, the incidence, or even the relationship to anesthetic management, remains conjectural. Prospective study tends to uncover many more cases than retrospective evaluation.10 The present series is a reminder that patients should be examined closely when they register oral complaints. Practitioners might quickly assume that oral complaints result from either tooth trauma or “sore throat” from tracheal intubation.12 Practitioners should, however, be mindful of other types of injuries as well.

Fortunately, the lesions highlighted by Almazrooa et al., although painful, were self-limiting and without serious sequelae. One must appreciate the collaborative thinking required to recognize a possible connection that might have been overlooked by either the anesthesiologist or dentist in isolation. Others should now be on the lookout. What are needed now are prospective studies to elucidate the incidence and time course of jaw osteonecrosis. We need better clinical definition of cases after surgery and cases labeled “spontaneous,” better delineation of etiologies, and especially, strategies for prevention or management.

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REFERENCES

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