4. Laryngoscope, 127:2833-2842, 2017.

SUMMARY Disregarding the widely used division of skull base into anterior and lateral, since the skull base should be conceived as a single anatomic structure, it was to our convenience to group all those approaches that run from the antero-lateral, pure lateral and postero-lateral side of the skull base as “Surgery of the lateral skull base”. “50 years of endeavour” points to the great effort which has been made over the last decades, when more and more difficult surgeries were performed by reducing morbidity. The principle of lateral skull base surgery, “remove skull base bone to approach the base itself and the adjacent sites of the endo-esocranium”, was then combined with function preservation and with tailoring surgery to the pathology. The concept that histology dictates the extent of resection, balancing the intrinsic morbidity of each approach was the object of the first section of the present report. The main surgical approaches were described in the second section and were conceived not as a step-by-step description of technique, but as the highlighthening of the surgical principles. The third section was centered on open issues related to the tumor and its treatment. The topic of vestibular schwannoma was investigated with the current debate on observation, hearing preservation surgery, hearing rehabilitation, radiotherapy and the recent efforts to detect biological markers able to predict tumor growth. Jugular foramen paragangliomas were treated in the frame of radical or partial surgery, radiotherapy, partial “tailored” surgery and observation. Surgery on meningioma was debated from the point of view of the neurosurgeon and of the otologist. Endolymphatic sac tumors and malignant tumors of the external auditory canal were also treated, as well as chordomas, chondrosarcomas and petrous bone cholesteatomas. Finally, the fourth section focused on free-choice topics which were assigned to aknowledged experts. The aim of this work was attempting to report the state of the art of the lateral skull base surgery after 50 years of hard work and, above all, to raise questions on those issues which still need an answer, as to allow progress in knowledge through sharing of various experiences. At the end of the reading, if more doubts remain rather than certainties, the aim of this work will probably be achieved.

Objective: To review the classification and management of petrous bone cholesteatomas (PBCs) at our center and the outcomes of facial nerve (FN) management in these lesions. Methods: This was a retrospective study. The setting was a quaternary referral center for skull base pathology in Italy. A total of 200 patients with 201 PBCs were included in the study. All patients diagnosed radiologically with PBCs were classified according to the Sanna classification. All patients were surgically treated and followed up with radiology. The main outcome measures - classification of PBCs, the surgical approach used, disease control, and FN outcomes - were analyzed. Results: Supralabyrinthine PBCs were the most common type with 92 cases (45.8%) followed by the massive PBCs with 72 cases (35.8%). Preservation of preoperative FN function was highest in the infralabyrinthine (72.2%) and infralabyrinthine-apical (73.3%) types. The transotic approach was used in 66 cases (32.8%) in this series. The modified transcochlear approach type A was applied in 55 cases (27.3%). Active management of the nerve (rerouting, anastomosis, or grafting) was required in 53 cases (26.4%). Postoperatively, of the 116 cases with FN House-Brackmann grade I and II, 107 cases (92.2%) retained the same grade or improved. Recurrence was seen in 7 cases (3.5%). The mean duration of follow-up was 6.3 years. Conclusions: Radical disease clearance must take precedence over hearing and FN preservation in PBCs. Active FN management, including rerouting, end-to-end anastomosis, and cable nerve grafting, routinely come to play in the surgical management of PBCs, and the postoperative FN results after such interventions can be satisfactory in most cases.

Purpose To correlate objective measures of audio-vestibular function with superior canal dehiscence (SCD) size and location in ears with SCD and compare results with literature. Methods We retrospectively evaluated 242 patients exhibiting SCD and/or extremely thinned bone overlying superior canals (SC) on CT scans and selected 73 SCD patients (95 ears with SCD). Data concerning audiometry, impedance audiometry, video-head impulse test (vHIT), cervical vestibular-evoked myogenic potentials (cVEMPs) and ocular VEMPs (oVEMPs) to air-(AC) and bone-conducted (BC) stimuli were collected for each pathologic ear and correlated with dehiscence size and location. Results AC pure-tone average (PTA) (p = 0.013), low-frequency air-bone gap (ABG) (p < 0.001), AC cVEMPs amplitude (p = 0.002), BC cVEMPs amplitude (p < 0.001) and both AC and BC oVEMPs amplitude (p < 0.001) positively correlated with increasing SCD size. An inverse relationship between dehiscence length and both AC cVEMPs and oVEMPs thresholds (p < 0.001) and SC vestibulo-ocular reflex (VOR) gain (p < 0.001) was observed. Dehiscences at the arcuate eminence (AE) exhibited lower SC VOR gains compared to SCD along the ampullary arm (p = 0.008) and less impaired BC thresholds than dehiscences at the superior petrosal sinus (p = 0.04). ConclusionWe confirmed that SCD size affects AC PTA, ABG and both amplitudes and thresholds of cVEMPs and oVEMPs. We also described a tendency for SC function to impair with increasing SCD size and when dehiscence is located at the AE. The latter data may be explained either by a spontaneous canal plugging exerted by middle fossa dura or by a dissipation through the dehiscence of mechanical energy conveyed to the endolymph during high-frequency impulses.

Objective: To assess all different patterns of associated abnormalities on audiometry, bithermal caloric test (BCT) and cervical/ocular vestibular-evoked myogenic potentials (VEMPs) to air/bone-conduction in patients with selective posterior semicircular canal (PSC) hypofunction and to correlate them with underlying disorders. Study Design: Retrospective review. Setting: Tertiary referral center. Patients: 51 patients (23 men, 28 women, mean age 57.5 yr) with isolated PSC deficit (one bilateral). Interventions: Correlation with instrumental data and underlying diagnoses. Main Outcome Measures: Video-oculographic findings, objective measurements on audiometry, BCT, VEMPs and video-head impulse test (vHIT). Results: Ongoing or previous acute vestibular loss (AVL) was diagnosed in 13 patients (25.5%, 3 inferior vestibular neuritis, 10 AVL with sudden sensorineural hearing loss [SSNHL]), Meniere's disease (MD) in 12 (23.5%), cerebellopontine angle (CPA) lesion in 9 (17.6%), various causes in 7 (13.7%), benign paroxysmal positional vertigo (BPPV) involving the non-ampullary arm of PSC in 5 cases (9.8%) whereas unknown pathology in 5 (9.8%). Involvement of at least one additional receptor besides PSC was seen in 89.8% of cases. Cochlear involvement was diagnosed in 74.5% with pure-tone average significantly greater in patients with AVL+SSNHL (p < 0.05). Overall involvement of labyrinthine receptors or afferents was highest in patients with AVL+SSNHL (p < 0.01), MD and CPA lesions (p < 0.05). Conclusions: Isolated loss of PSC function on vHIT is mostly accompanied by additional labyrinthine deficits that could only be identified through an accurate instrumental evaluation. Assessment of all receptors and afferents should be always pursued to identify the lesion site and better understand the underlying pathophysiological mechanisms.