Relationship Between the Cochlear Aqueduct and Internal Auditory Canal: Surgical Implications for Transcanal Transpromontorial Approaches to the Lateral Skull Base

Microsurgical anatomy of the glossopharyngeal nerve

The glossopharyngeal nerve is a complicated and mixed nerve including sensory, motor, parasympathetic, and visceral fibers. It mediates taste, salivation, and swallowing. The low cranial nerves, including IXth, Xth, and XIth, are closely related, sharing some nuclei in the brainstem. The glossopharyngeal nerve arises from the spinal trigeminal nucleus and tract, solitary tract and nucleus, nucleus ambiguous, and inferior salivatory nucleus in the brainstem. There are communicating branches forming a neural anastomotic network between low cranial nerves. Comprehensive knowledge of the anatomy of the glossopharyngeal nerve is crucial for performing surgical procedures without significant complications. This review describes the microsurgical anatomy of the glossopharyngeal nerve and illustrates some pictures involving the glossopharyngeal nerve and its connective and neurovascular structures.

Signaling pathways regulating the immune function of cochlear supporting cells and their involvement in cochlear pathophysiology

The inner ear, including the cochlea, used to be regarded as an immune-privileged site because of its immunologically isolated environment caused by the blood-labyrinthine barrier. Cochlear resident macrophages, which originate from the yolk sac or fetal liver during the embryonic stage and are maintained after birth, are distributed throughout various regions of the cochlear duct. Intriguingly, these cells are absent in the organ of Corti, where hair cells (HCs) and supporting cells (SCs) are located, except for a limited number of ionized calcium-binding adapter molecule 1 (Iba1)-positive cells. Instead, SCs exert glial functions varying from a quiescent to an emergency state. Notably, SCs acquire the nature of macrophages and begin to secrete inflammatory cytokines during viral infection in the organ of Corti, which is ostensibly unprotected owing to the lack of general resident macrophages. This review provides an overview of both positive and negative functions of SCs enabled to acquire macrophage phenotypes upon viral infection focusing on the signaling pathways that regulate these functions. The former function protects HCs from viral infection by inducting type I interferons, and the latter function induces HC death by necroptosis, leading to sensorineural hearing loss. Thus, SCs play contradictory roles as immune cells with acquired macrophage phenotypes; thereby, they are favorable and unfavorable to HCs, which play a pivotal role in hearing function.

Vestibular schwannoma removal through expanded transcanal transpromontorial approach: a multicentric experience

PURPOSE

Expanded Transcanal Transpromontorial Approach (ExpTTA) is an endomicroscopic technique that allow surgical excision of small and symptomatic neuromas limited to the internal auditory canal (IAC) or minimally invasive the cerebellopontine angle (CPA). ExpTTA is a safer alternative to the exclusive endoscopic technique as it allows a wider surgical field and better management of the auditory porus and CPA.

METHODS

We report a retrospective case series of 34 patients who underwent ExpTTA between 2017 and 2022 at the ENT Departments of the University Hospital of Modena, Bologna and Verona. Tumor size was defined according to the Koos staging and hearing function was classified according to the AAOHNS. A clinical evaluation of facial nerve (FN) function was performed using the House and Brackman scale (HBs).

RESULTS

Our cohort consists of 34 patients. At time of surgery all patients had a normal preoperative facial function. Gross total resection was achieved in all patients, without intraoperative complications, and FN continuity was preserved in all cases. No major complications were observed. Regarding post-operative FN function, at hospital discharge ten patients had impairment equal or greater than IV grade according to H&Bs. At 6 months after surgery only two patients presented with moderate/severe facial paralysis (grade IV H&Bs) and finally at 12-month follow-up all patients had a satisfactory recovery of nervous function (grade < III H&Bs).

CONCLUSIONS

ExpTTA is a safe and effectively technique for treatment of small VS (Koos I, II and selected cases of Koos III) with low postoperative morbidity.

Maturation of the internal auditory canal and posterior petrous bone with relevance to lateral and posterolateral skull base approaches

Anatomic knowledge of the internal auditory canal (IAC) and surrounding structures is a prerequisite for performing skull base approaches to the IAC. We herein perform a morphometric analysis of the IAC and surgically relevant aspects of the posterior petrous bone during pediatric maturation, a region well-studied in adults but not children. Measurements of IAC length (IAC-L), porus (IAC-D) and midpoint (IAC-DM) diameter, and distance from the porus to the common crus (CC; P-CC) and posterior petrosal surface (PPS) to the posterior semicircular canal (PSC; PPS-PSC) were made on thin-cut axial CT scans from 60 patients (grouped by ages 0–3, 4–7, 8–11 12–15, 16–18, and > 18 years). IAC-L increased 27.5% from 8.7 ± 1.1 at age 0–3 to 11.1 ± 1.1 mm at adulthood (p = 0.001), with the majority of growth occurring by ages 8–11. IAC-D (p = 0.52) and IAC-DM (p = 0.167) did not significantly change from ages 0–3 to adult. P-CC increased 31.1% from 7.7 ± 1.5 at age 0–3 to 10.1 ± 1.5 mm at adulthood (p = 0.019). PPS-PSC increased 160% from 1.5 ± 0.7 at age 0–3 to 3.9 ± 1.2 mm at adulthood (p < 0.001). The majority of growth in P-CC and PPS-PSC occurred by ages 12–15. Knowledge of these patterns may facilitate safe exposure of the IAC in children.