Discussion:
Many groups have reported on the vascular flow of the auricle. (3-6) Blood supply depends on two branches of the external carotid arteries: 1) the superficial temporal artery; and 2) the posterior auricular artery. These branches form the dense arterial network perforating the cartilage. Recently, Zilinsky re-evaluated the arterial supply of the auricle. Superior and inferior auricular branches of the superficial temporal artery mainly supply the helical rim of the auricle.(6) The upper third of the helical rim was also supplied from non-performing branches of the posterior auricular artery. The perforators of the posterior auricular artery supply the concha, inferior crus, triangular fossa antihelix, and the ear lobe.(6) Venous drainage occurs through the accompanying veins of each artery.
LTBR and STBR are popular surgical methods for en bloc resection of temporal bone malignancy. It is clear that arterial supply to the auricle is significantly impaired when en bloc resection combined with parotidectomy is performed or when the superficial temporal artery is sacrificed. The frequency of auricular complication has not been elucidated. To our knowledge, Carpenter al. first reported ear complications in temporal bone surgery.(2) They followed 32 patients who underwent lateral skull base surgery, including parotid surgery, subtemporal fossa surgery, and temporal bone surgery. Postoperative necrosis was found in 3 of the 32 cases. However, that study reported no statistically significant risk of avascular necrosis when comparing preauricular and postauricular approaches, suggesting that no detailed study had previously identified a significant relationship with surgical procedures.
Simple LTBR can logically preserve the arterial supply of the auricle, and theoretically preserve anterior venous drainage of the superficial temporal vein. However, with STBR or LTBR, along with additional procedures, including parotidectomy and manipulation of the TMJ, it is impossible to preserve the main arterial branches to the auricle and both the main anterior and posterior venous drainage routes. We examined 34 cases who had undergone these procedures, and three of them showed postoperative vascular insufficiency in the auricle. However, sacrificing main arterial flow did not lead to ischemic auricular necrosis in any cases. Generally, the facial region has an abundant arterial network. The result of our study suggests the auricles had sufficient blood supply via the anastomosis connecting the facial arterial network. In our study, only one case showed postoperative auricular necrosis after auricular congestion, due to insufficient bloodletting after surgery. Appropriate postoperative bloodletting recovered auricular congestion and preserved the auricle cosmetically in the other two cases with postoperative vascular insufficiency in the auricle. These facts imply that venous drainage is crucial for preserving the auricle after temporal bone resection.
Veins in the face, which include the superior ophthalmic and facial veins, contain valves that determine blood flow direction.(7, 8) Zhang et al. mentioned that blood flow in the face is (1) caudal toward the internal jugular vein in the inferior part of the facial vein; (ii) normally toward the cavernous sinus in the superior ophthalmic vein; and (iii) into either the facial vein or the superior ophthalmic vein from the angular vein.(8) If the two main drainage routes from the auricle are sacrificed after temporal bone resection, the venous network in the face may be important for maintaining venous flow from the auricle. Hosokawa et al. recommend parotidectomy when the tumour invades the anterior–inferior wall of the canal.(9) If an early-stage tumour invaded this wall, we applied partial resection of the parotid gland and soft tissue abutting the canal. Furthermore, total parotidectomy is recommended for advanced T3 and T4 cases.(10, 11) The superficial temporal artery emerges from the superior border of the parotid gland and courses superolaterally between the TMJ and the tragus, and cross-superficially to the zygomatic process accompanied by the superficial temporal vein. Therefore, dissecting the infra-/pre-auricular region and manipulating the TMJ results in sacrificing the anterior drainage route from the auricular to the superficial temporal vein. To elevate the auricle, the posterior drainage route to the posterior auricular vein needs to be divided in all temporal bone resection cases. During neck dissection, common facial veins are often ligated. These cause a dramatic change in the venous flow related to the auricle. Unlike with arterial flow, it is likely that the valves in veins make it difficult for the venous drainage system to adapt to changes in blood flow after temporal bone resection. When pre-/infra-auricular lymphadenopathy is found preoperatively, the tissue around the lymph node needs to be sufficiently dissected to achieve adequate surgical margins. Therefore, temporal bone resection combined with total, superficial, or partial parotidectomy or with TMJ manipulation leads to sacrificing the main venous drainage from the auricle to the superficial temporal vein and the posterior auricular vein. In addition, careful dissection of the subcutaneous tissue around the lymphadenopathy potentially damages the venous network in the subcutaneous layer, which can worsen auricular congestion postoperatively.
Our analysis showed that cases with pre-/infra-auricular lymph node dissection had a statistically significant risk of auricular complication in the temporal bone resection (Fig. 5). Neck dissection, parotid gland resection TMJ manipulation and history of radiation therapy can worsen the venous drainage, theoretically. In addition, our study suggest that pre-/infra-auricular lymph node dissection had most impact to the worsens venous drainage leading to auricular congestion. A clear consensus on the guidelines for treating external ear congestion is lacking. Tissue milking, pin pricking,(12) use of medical leeches,(13, 14) mechanical leeching, (15) and chemical leeching(16) are the current treatment methods for venous congestion. In our two cases, mechanical bloodletting effectively salvaged the auricular necrosis. When the colour of the auricle changes during surgery, either 1) arterial spasm or 2) venous flow obstruction could be the cause. If ischemia due to artery spasm is observed, bleeding from the wound is confirmed after some time. If congestion is observed, it is important to check whether congestion can be recovered by pinprick, bloodletting and so on. Sufficient bloodletting should be initiated as soon as possible following confirmation of auricular congestion by the surgeon.
Our study involved several limitations, including small sample size and its retrospective nature. In addition, our sample was comprised of only 63 patients. Further studies are needed to confirm the cause and risk factors associated with auricular complications.