Case Description. Unusual middle ear symptoms immediately followed the administration of 1.8 milliliters of 3 percent mepivacaine for a Gow-Gates mandibular block injection. Over the course of 10 days, the patient had complaints of inner ear pressure, inability to equilibrate ear pressure, decreased hearing, pain and severe headache before returning to normal without further complaints and complications.

Conclusions. The cause of the complications was either a hematoma, a technique problem causing trauma and inflammation, an anatomical variation or any combination of these.

Clinical Implications. Proper technique, knowledge of the anatomy of the injection area and familiarity with potential complications are important in the administration of local anesthetic.

As a general rule, complications resulting from administration of local anesthetic can be divided into two categories: localized and systemic.^1,3–6 Localized complications include needle breakage,^4–7 pain or burning on injection, paresthesia, trismus, hematoma, infection, soft-tissue injury, self-inflicted soft-tissue trauma, facial nerve paralysis, sloughing of tissues and post-anesthetic intraoral lesions.^4–6 More specific examples include patients who have acquired visual or motor problems, or both, in the eye after either a posterior superior alveolar injection or an inferior alveolar injection.^8,9 Furthermore, there have been reports of trauma to both lingual and chorda tympani nerves after inferior alveolar injections.^3,10 Systemic complications can result from intra-vascular injections, drug overdose, rapid absorption, delayed biotransformation, slow elimination and allergies.⁴ Although many of these events could be considered uncommon, dentists around the United States administer more than 6 million cartridges of dental anesthetic per week and give in excess of 300 million injections per year, which means that even the most uncommon of complications have the potential to be experienced by patients in the dental office.⁴

In 1973, Dr. George Gow-Gates¹¹ described a "true" mandibular block technique, whereby the anesthetic solution is delivered to the region by the neck of the condyle, to act on the nerve at a site proximal to its branches. These branches include the buccal nerve from the anterior division of V3, and, in descending order, the auriculotemporal, lingual, mylohyoid and inferior alveolar nerves of the posterior division of V3. This single injection then not only may block sensation from the inferior alveolar and lingual nerves, but also may anesthetize the mylohyoid, auriculotemporal and buccal branches of the mandibular nerve.⁴ The Gow-Gates injection also is reported to anesthetize the inferior alveolar nerve on the first injection more successfully than the standard inferior alveolar injection.^4,12 In addition, the Gow-Gates technique has been found to be significantly less painful in children (4 to 16 years of age) than is the standard inferior alveolar block technique.¹³

However, although this mandibular block technique has been found to be both more successful and less painful than the inferior alveolar block, problems still have been reported with it. These complications happen to be similar to those associated with the inferior alveolar nerve injection, the most notable being temporary paralysis of the cranial nerves that bring about and affect eye movement: the oculomotor (cranial nerve, or CN, III), trochlear (CN IV) and abducens (CN VI) nerves.^4,14 Furthermore, there have been reports of hematomas and trismus at the level of insertion of the lateral pterygoid muscle during a Gow-Gates mandibular block injection.^4,12

Although complications with the Gow-Gates injection technique have occurred, a literature search revealed no problems concerning the ear, a structure that is in very close proximity to the neck of the condyle and the deposition site. The following is a case report of a complication involving the middle ear after the administration of local anesthetic using the Gow-Gates injection technique.

	CASE REPORT

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During a local anesthetic practice exercise at the University of the Pacific School of Dentistry, San Francisco, a healthy 22-year-old male dental student was administered a Gow-Gates injection that resulted in complete anesthesia of the inferior alveolar, lingual and auriculotemporal nerves. A classmate, carrying out the procedure under one-on-one supervision from a trained and experienced faculty dentist, had noted a positive aspiration on needle insertion and thus adjusted the needle until a negative aspiration was achieved before he administered the local anesthetic. Immediately after receiving the injection, the student-patient complained that he had felt a buildup of pressure in his middle ear region during the release of 1.8 milliliters, or mL, of the 3 percent mepivicaine solution without vasoconstrictor. Examination after this complaint revealed no bleeding from the site of injection and no signs of hematoma.

The symptoms of anesthesia wore off in four hours, but for the next seven days the patient complained about not being able to properly "equilibrate" the pressure in the ear on the side of the face that had received the injection. In addition, he complained of having difficulty hearing in that ear and felt pressure in the middle ear region as if there was fluid in it. At the end of the seventh day, the patient and the faculty dentist made a joint decision to seek an examination by an otolaryngologist and by a dentist in the school’s facial pain clinic who happened to be an associate professor in the school’s department of pathology and medicine. A dry human skull also was brought to the examinations to demonstrate the path of the injection and the deposition site. The examination by the physician and the dentist revealed nothing outside of normal limits, and they could make no definitive diagnosis. However, the professor of pathology felt that something, possibly a hematoma, was placing pressure on and creating inflammation in the patient’s eustachian tube.

The symptoms changed between the eighth and 10th days after the injection to include pain in the ear region and severe headache. The patient reported the pain in the ear as continuous, pulsating and severe. The headache pain was of the tension type and described as constant, steady and aching in nature. The patient tried to alleviate the pain with three 400-milligram doses of ibuprofen over the period of a day, but reported only a small reduction in the pain. The patient claimed that he rarely experienced headaches and that this event must have been due to the injection, although this cannot be proved. The patient experienced a gradual reduction of symptoms and, after a total of 10 days, was free of any abnormal symptoms.

	DISCUSSION

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The deposition site for the Gow-Gates mandibular block is approximately 1 millimeter from the neck of the condyle, below the insertion of the lateral pterygoid muscle in a relatively avascular fatty area.¹⁵ There have been inconsistent reports on the frequency of positive aspirations with the Gow-Gates injection. In 1977, Gow-Gates and Watson¹⁶ reported a 1.6 percent incidence of positive aspiration with this injection, far lower than the 7.9 percent average in eight studies in which a total of 10,286 injections were given via the conventional inferior alveolar injection technique.² However, in 1981, Levy¹⁷ noted a positive aspiration 7.7 percent of the time with the Gow-Gates injection, which is comparable to rates with the inferior alveolar injection. In addition, Montagnese and colleagues¹⁸ and Robertson¹⁹ recorded positive aspiration on injection 15 percent and 17 percent of the time, respectively, for the Gow-Gates injection. Although Malamed⁴ reported a much lower rate of aspiration, he speculated that the large internal maxillary artery that sits a few millimeters inferior to the target site (neck of the condyle) is the blood vessel usually penetrated during a positive aspiration test. (Figure 1²⁰ shows the artery in question.)

View larger version (48K): [in this window] [in a new window]   Figure 1. The maxillary artery and its branches. Reprinted with permission of the publisher from Agur and Lee.20

This theory of hematoma-induced symptoms in this case report is supported by the fact that hematomas normally resorb in seven to 14 days⁴ and that it took the patient 10 days to be free of all symptoms. Another reason for this hypothesis is that the complication described in this article is the first such experienced at this university, where, during the past nine years, 150 dental students have administered the Gow-Gates injection to each other and have used the injection during their two clinical years. Noteworthy is the fact that the complication arose during the only year in which a local anesthetic without vasoconstrictor was used in the local anesthesia course. The faculty agreed to the use of a local anesthetic without vasoconstrictor because of students’ desire for a shorter duration of anesthesia.

It is absolutely impossible to determine the exact mechanism of this complication, but it also may have been a problem in technique. According to Jastak and colleagues,² one of the main disadvantages of the Gow-Gates injection is difficulty in learning the technique. In other words, the student-operator probably misguided the needle too far medially and deposited the local anesthetic either in or close to the auditory tube. Deflection of the needle away from the bevel may or may not have played a role in the misguidance.² This medially placed injection would have resulted in blockage of the tube and the patient’s inability to equalize pressure. Soon after, it is possible that trauma from the needle may have led to a secondary inflammatory reaction in the tube, around it or both, which would have prolonged the blockage for about a week until the inflammation dissipated. Once the inflammation subsided, the tube was able to resume its healthy pressure-equalizing function. It also should be noted that this problem could have occurred in the hands of an experienced operator whose technique is poor. After all, "all too often, local anesthetic administration becomes increasingly traumatic to the patient the longer a dentist has been out of school,"⁴ because experienced clinicians at times become lazy in maintaining their technique.

One last feasible explanation is that the patient may have had an eccentric anatomical variation with regard to his auditory tube or the surrounding structures. If this is the case, the best technique in the world could not have prevented this incident from occurring. It also is worth noting that two months after this incident, the same patient was given a successful Gow-Gates injection on the opposite side by a different operator. Once again, a positive aspiration occurred before the syringe was repositioned, but this time no negative symptoms occurred as a result of the injection. This is not of major significance, because it is well-known that some people have slight variations in anatomy and are asymmetric bilaterally. It is worth noting that 2 percent lidocaine with 1:100,000 epinephrine was used with this injection, as opposed to 3 percent mepivicaine without vasoconstrictor.

	CONCLUSIONS

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Whether one is an inexperienced novice or an accomplished practitioner, proper technique is a very important aspect of administering local anesthetic. Without proper technique, the clinician may inflict pain on patients and incur complications unnecessarily. Therefore, when performing the Gow-Gates technique, the clinician should be sure to orient the syringe properly before puncturing the mucosa.² One of the keys to mastering this technique is the lateral angulation of the needle, which must be determined on the basis of the location of the condyle.² If the position of the condyle is misread, the tip of the needle very easily can end up in an undesired position.

The cause of the complications in this case is not entirely known. But there is a good chance that the source was either a hematoma, a technique problem causing trauma and subsequent inflammation, an anatomical variation or any combination of these.

View larger version (136K): [in this window] [in a new window]   Mr. Brodsky is a Class of 2002 student at the University of the Pacific, School of Dentistry, San Francisco.

View larger version (139K): [in this window] [in a new window]   Dr. Dower is an associate professor, Restorative Dentistry, and the director, Local Anesthesia Curriculum, University of the Pacific School of Dentistry, 2155 Webster St., San Francisco, Calif. 94115-2333, e-mail "jdower{at}sf.uop.edu". Address reprint requests to Dr. Dower.