The Endoscopic Anatomy of the External Acoustic Meatus and of the Middle Ear in Dry Temporal Bones: A Study Conducted Using Digital and Mobile Device Technology

Abstract Introduction The endoscopic anatomy of the middle ear (ME) and of the external acoustic meatus (EAM) has been described in cadavers, in fresh temporal bones, or in vivo using conventional video recording, but not in dry bones or using an alternative inspection and recording technique. Objective To study the anatomy of the ME and of the EAM in dry temporal bones using a smartphone-endoscope system. Methods The EAM and the ME were studied in dry temporal bones using an endoscopic transcanal approach with a telescope connected to a smartphone (M-scope mobile endoscope app and adaptador, GBEF Telefonia, São Paulo, SP, Brazil). Results Out of 50 specimens, 2 had exostosis of the EAM and 3 contained remains of the tympanic membrane. The anterior wall of the EAM was prominent in 10/48 specimens (20.8%). Ossicles were seen in 13/45 (28.8%), stapes at the oval window were seen in 12/45 (26.6%), and the incus was seen in 1/45 (2.2%) specimens. The facial canal was open and protruding in 15/45 (33.3%) and in 7/45 (15.5%) specimens, respectively. Of the 45 MEs evaluated, type A was predominant for finiculus (93.3%), subiculum (100%), and ponticulus (95.6%). The rest were type B. None was classified as type C. According to its position in relation to the round window, the fustis was classified into type A (68.9%) or B (31.1%). The pyramidal eminence, the bony portion of the Eustachian tube, the semicanal of the tensor tympani muscle, and the cochleariform process were visualized completely or partially in all cases. Conclusion The use of a smartphone-based endoscopic transcanal procedure in dry temporal bones allowed the evaluation of anatomical variations in the EAM and in the ME.

Extracranial landmarks for surgical skull base approaches / Puntos de referencia extracraneales para abordajes quirúrgicos de la base del cráneo

SUMMARY: Surgical operations regarding to skull base are challenging and reliable anatomical landmarks are required. There is a lack of knowledge on anatomical variations in this region. The aim of this study was to determine the safe extracranial landmarks for surgical approach to the skull base. In this study, 23 adult dry skulls were evaluated: the age and sex of the specimens were unknown. All measurements were taken from external surface of inferior aspect of the skull by using digital calipers accurate to 0.01 mm. In right and left sides; the distances between the external acoustic meatus (EAM) and the following anatomical landmarks were measured: articular tubercle (AT); anterior margin of squamous suture (ASS); superior margin of squamous suture (SSS); posterior margin of squamous suture (PSS); end point of styloid process (SP); midpoints of pterygomaxillary fissure (PMF); foramen ovale (FO); foramen spinosum (FS); and of carotid canal (CC).The distances of the external acoustic meatus to the anatomical structures on the right and left sides were: EAM-SP; 24.24±3.19 mm, 23.16±3.17 mm; EAM-PMF; 46.56±4.51mm, 46.25±3.96 mm; EAM-FO; 27.57±2.87 mm, 28.70±2.85 mm; EAM-FS; 22.53±3.19 mm, 22.72±3.47 mm; EAM-CC; 17.35±3.56 mm, 17.19±3.39 mm; EAM-AT; 19.31±3.79 mm, 18.95±3.42 mm; EAM-ASS; 43.14±4.80 mm, 46.82±4.61 mm; EAM-SSS; 49.17±4.74 mm, 48.83±3.34 mm and EAM-PSS; 36.15±4.24 mm, 35.39±4.25 mm, respectively. We think that the findings obtained from this study related to external acoustic meatus can be an important reference for surgical anatomy and surgical procedures in skull base.

RESUMEN: Las cirugías relacionadas con la base del cráneo son un desafío, las cuales requieren puntos de referencia anatómicos confiables. Existe una falta de conocimiento sobre las variaciones anatómicas en esta región. El objetivo de este estudio fue determinar los puntos de referencia extracraneales seguros para el abordaje quirúrgico de la base del cráneo. En este estudio se evaluaron 23 cráneos secos adultos: se desconocía la edad y el sexo de los ejemplares. Las medidas se tomaron de la superficie externa de la cara inferior del cráneo utilizando calibradores digitales con una precisión de 0,01 mm. En lados derecho e izquierdo se midieron las distancias entre el meato acústico externo (MAE) y los siguientes puntos de referencia anatómicos: tubérculo articular (TA); margen anterior de la sutura escamosa (MASE); margen superior de sutura escamosa (MSSE); margen posterior de sutura escamosa (MPSE); punto final del proceso estiloides (PFPE); puntos medios de la fisura pterigomaxilar (PMFP); foramen oval (FO); foramen espinoso (FE); y del canal carotídeo (CC). Las distancias del meato acústico externo a las estructuras anatómicas de los lados derecho e izquierdo fue- ron: MAE-PFPE; 24,24 ± 3,19 mm, 23,16 ± 3,17 mm; MAE-PMFP; 46,56 ± 4,51 mm, 46,25 ± 3,96 mm; MAE-FO; 27,57 ± 2,87 mm, 28,70 ± 2,85 mm; MAE-FE; 22,53 ± 3,19 mm, 22,72 ± 3,47 mm; MAE-CC; 17,35 ± 3,56 mm, 17,19 ± 3,39 mm; MAE-TA; 19,31 ± 3,79 mm, 18,95 ± 3,42 mm; MAE-MASE; 43,14 ± 4,80 mm, 46,82 ± 4,61 mm; MAE-MSSE; 49,17 ± 4,74 mm, 48,83 ± 3,34 mm y MAE-MPSE; 36,15 ± 4,24 mm, 35,39 ± 4,25 mm, respectivamente. Creemos que los hallazgos obtenidos de este estudio relacionados con el meato acústico externo pueden ser una referencia importante para la anatomía quirúrgica y los procedimientos quirúrgicos en la base del cráneo.

A novel technique for micro-reconstruction of posterior wall of external auditory canal and tympanum in patients with chronic supprative otitis media using pedicled temporalis myofascia / 中华显微外科杂志

Objective To explore a novel surgical treatment for chronic suppurative otitis media (CSOM) and evaluate its treatment effect.Methods All 97 patients with chronic suppurative otitis media were chosen to be treated using this new surgical method.The skin of the external auditory canal was maintained intact.Open radical mastoidectomy was used to complete clean-up lesions ; the fascia of pedicled temporalis myofascia (PTM) was used to repair the tympanic membrane.The pedicled temporalis fascia,pedicled postauricular periosteal flap and intact skin of the external auditory canal were used in reconstruction of the posterior wall of external auditory canal.Pure tone audiometry (PTA) was performed before and after surgery,recording the air conduction and bone conduction thresholds at 0.5 kHz,1.0 kHz,2.0 kHz,4.0 kHz.The average of the patient's air and bone conduction hearing thresholds was recorded at the 4 frequencies.External auditory canal gauze was removed 3 weeks after surgery.All subjects were followed up for over 2 years.Comparison of hearing thresholds (PTA) was made ① Before and 4 weeks after surgery.② Before and 2 years after surgery.Hearing function comparison include air conduction (AC),bone conduction (BC) and air-bone gap (ABG) analysis.SPSS 16.0 was used in statistical analysis.Pre-and postoperated AC,BC and ABG were compared using T-test.P ＜ 0.05 was considered statistically significant.Results The healing rate of post-operated tympanic membrane was 95.88％ (93/97).Ninty-six ears had 2-year follow-up,and 1 patient was lost in follow-up.There were 2 patients presented with eardrum perforation during the follow-up,and the 2-year healing rate of tympanic membrane perforation was also 93.85％ (92/97).In 96 ears with 2-year followed-up,the average of pre-AC was (52.10 ±3.96) dB,the average of post-AC was (35.67 ±2.52) dB; the average of preABG was (36.6 ± 5.2) dB,and the average of post-ABG (± SD) was (12.14 ± 6.20) dB.Statistical analysis showed significant difference between preoperative and postoperative AC or ABG values (P ＜ 0.05).Conclusion The present surgical procedure broke through the existing conventional mastoidectomy of making a surgical incision in the posterior wall of the external auditory canal.This procedure cleared the lesion completely and preserved the physiological function of the external auditory canal.The acoustic systems and state of gasification to the mastoid tymnpanum were reconstructed,rehabilitated and maintained.The healing rate of hearing and tympanic membrane perforation was improved.