Transmastoid exposure of the labyrinthine segment of the facial nerve: an anatomical study.

INTRODUCTION: Compression of the labyrinthine segment of the facial nerve by edema has been considered as an important pathology in the majority of the cases of idiopathic facial nerve paralysis. Hence, it is suggested that total decompression of the facial nerve should also include the labyrinthine segment by a middle fossa approach. However, the middle fossa approach requires craniotomy and temporal lobe retraction, which increases the morbidity. The labyrinthine segment of the facial nerve can also be reached through mastoidectomy. However, many ear surgeons are not familiar with this approach due to the lack of anatomical data on this surgical area. OBJECTIVE: To study the anatomical limitations of decompression of the labyrinthine segment via transmastoid approach. METHODS: Complete mastoidectomy was performed in six adult cadavers heads. Dissection was extended in the zygomatic root and posterior bony wall of the external auditory canal to visualize the incudomallear joint completely. The bone between tympanic segment, lateral and superior semicircular canal's ampullas and middle fossa dural plate was removed. Fine dissection was carried out over tympanic segment of the facial nerve in an anterosuperomedial direction the labyrinthine segment was reached. RESULTS: All the mastoids were well pneumatized. Distances between the labyrinthine segment and middle fossa dura, and between the labyrinthine segment and superior semicircular canal, were 2.5 and 4.5 mm on average, respectively. In addition, distances between the middle fossa dura and dome of the lateral semicircular canal, and between the middle fossa dura and tympanic segment were 4.6 mm and 4.3 mm on average, respectively. CONCLUSION: It is possible to expose the labyrinthine segment of the facial nerve through mastoidectomy by dissecting the bone in the area between the tympanic segment of the facial nerve, middle fossa dural plate and ampullary ends of the lateral and superior semicircular canals.

Transmastoid exposure of the labyrinthine segment of the facial nerve: an anatomical study,

Abstract Introduction: Compression of the labyrinthine segment of the facial nerve by edema has been considered as an important pathology in the majority of the cases of idiopathic facial nerve paralysis. Hence, it is suggested that total decompression of the facial nerve should also include the labyrinthine segment by a middle fossa approach. However, the middle fossa approach requires craniotomy and temporal lobe retraction, which increases the morbidity. The labyrinthine segment of the facial nerve can also be reached through mastoidectomy. However, many ear surgeons are not familiar with this approach due to the lack of anatomical data on this surgical area. Objective: To study the anatomical limitations of decompression of the labyrinthine segment via transmastoid approach. Methods: Complete mastoidectomy was performed in six adult cadavers heads. Dissection was extended in the zygomatic root and posterior bony wall of the external auditory canal to visualize the incudomallear joint completely. The bone between tympanic segment, lateral and superior semicircular canal's ampullas and middle fossa dural plate was removed. Fine dissection was carried out over tympanic segment of the facial nerve in an anterosuperomedial direction the labyrinthine segment was reached. Results: All the mastoids were well pneumatized. Distances between the labyrinthine segment and middle fossa dura, and between the labyrinthine segment and superior semicircular canal, were 2.5 and 4.5mm on average, respectively. In addition, distances between the middle fossa dura and dome of the lateral semicircular canal, and between the middle fossa dura and tympanic segment were 4.6 mm and 4.3 mm on average, respectively. Conclusion: It is possible to expose the labyrinthine segment of the facial nerve through mastoidectomy by dissecting the bone in the area between the tympanic segment of the facial nerve, middle fossa dural plate and ampullary ends of the lateral and superior semicircular canals.

Examination of the Relation Between Audiometric Configuration and Hematological Parameters in Idiopathic Sudden Sensorineural Hearing Loss.

Among the hematological parameters, neutrophil/lymphocyte ratio (NLR) and platelet/ lymphocyte ratio (PLR) have been associated with inflammatory state, microvascular damage and ischemia. It is well-known that these ratios increase in idiopathic sudden sensorineural hearing loss (ISSHL). In ISSHL, different audiographic features may reflect different disease mechanisms. This study aimed to investigate whether there were differences in NLR and PLR among patient groups with different audiometric configurations. Patients meeting the study inclusion criteria were divided into four groups according to their audiogram configurations. Mean NLR and PLR values of the patient groups were compared among themselves and versus control group. The study was conducted with 166 participants. Mean NLR values were 3.07 ± 2.48, 3.30 ± 2.70, 5.24 ± 3.71, 3.57 ± 3.19 and 1.51 ± 0.68 for ascending, flat, descending and total/subtotal audiometric configuration groups and control group, respectively. Mean PLR values were 145.2 ± 126.7, 130.9 ± 57.8, 192.2 ± 94.4, 143.7 ± 70.8 and 94.1 ± 24.7 for ascending, flat, descending, total/subtotal audiometric configuration groups and control group, respectively. Both NLR and PLR were significantly greater in patients from all configuration groups than in control group (p < 0.05). In addition, the group with descending audiometric configuration showed significantly higher mean NLR and PLR compared to other audiometric configuration groups (p < 0.05). The highest level of inflammation was detected in the ISSHL patient group with high frequency hearing loss and descending audiographic configuration.

Effect of thermal energy produced by drilling on the facial nerve: histopathologic evaluation in guinea pigs.

The effect of thermal energy due to drilling around the facial nerve canal on the facial nerve was histopathologically evaluated in four guinea pigs. The bony canal of the facial nerve was drilled using a 3 mm diamond burr for one minute. The temperature changes on the facial nerve canal were noted before and after dissection. The temporal bones of the animals were histopathologically examined under light microscopy using haematoxylin & eosin (H&E) and solochrome cyanine staining for myelin, and immunohistochemical staining for neuronal nitric oxide synthase (nNOS). Compared to the control group, it was observed with H&E staining that there was oedema among the axonal fibres and with solochrome cyanine staining that the thickness of the myelin fibres was decreased, and that the severity and extent of nNOS activity was decreased in the axonal fibres. It was concluded that a temperature increase on the facial canal may potentially lead to inflammation of the nerve, and may also cause deterioration of nerve conduction to some extent.

Considerations of isolated destruction of the short process of the incus in a case of cholesteatoma.

Cholesteatoma occurs frequently with the destruction of the ossicles. The most commonly eroded ossicle has been reported to be the incus. Many studies report destruction of the long process and body of the incus. However, isolated erosion of the short process of the incus is an unusual finding. We present such a case with a slight conductive hearing loss that remained unchanged at 2 1/2 years postoperatively. The short process of the incus may contribute to hearing up to 10-15 dB. It is also possible that it plays a role in epitympanic aeration by supplying an attachment surface to the incudal folds.