Relations between cochlear histopathology and hearing loss in experimental cochlear implantation.

This study reviews the cochlear histology from four hearing preservation cochlear implantation experiments conducted on 73 guinea pigs from our institution, and relates histopathological findings to residual hearing. All guinea pigs had normal hearing prior to surgery and underwent cochlear implantation via a cochleostomy with a silastic-platinum dummy electrode. Pure tone auditory brainstem response (ABR) thresholds from 2 to 32 kHz were recorded prior to surgery, and at one and four weeks postoperatively. The cochleae were then fixed in paraformaldehyde, decalcified, paraffin embedded, and mid-modiolar sections were prepared. The treatment groups were as follows: 1) Systemic dexamethasone, 0.2 mg/kg administered 1 h before implantation, 2) Local dexamethasone, 2% applied topically to the round window for 30 min prior to cochlear implantation, 3) Local n-acetyl cysteine, 200 µg applied topically to the round window for 30 min prior to implantation, 4) inoculation to keyhole-limpet hemocyanin (KLH) prior to implantation, and 5) untreated controls. There was a significant correlation between the extent of the tissue reaction in the cochlea and the presence of foreign body giant cells (FBGCs), new bone formation and injury to the osseous spiral lamina (OSL). The extent of the tissue response, as a percentage of the area of the scala tympani, limited the best hearing that was observed four weeks after cochlear implantation. Poorer hearing at four weeks correlated with a more extensive tissue response, lower outer hair cell (OHC) counts and OSL injury in the basal turn. Progressive hearing loss was also correlated with the extent of tissue response. Hearing at 2 kHz, which corresponds to the region of the second cochlear turn, did not correspond with loco-regional inner hair cell (IHC), OHC or SGC counts. We conclude that cochlear injury is associated with poorer hearing early after implantation. The tissue response is related to indices of cochlear inflammation and injury. An extensive tissue response limits hearing at four weeks, and correlates with progressive hearing loss. These latter effects may be due to inflammation, but would also be consistent with interference of cochlear mechanics.

Diagnosis and outcomes of middle cranial fossa repair for patients with superior semicircular canal dehiscence syndrome.

The aim of this study was to retrospectively review the clinical presentation, diagnostic features, in particular cervical vestibular evoked myogenic potentials (cVEMPs), and the outcomes of surgical repair for superior semicircular canal dehiscence syndrome (SSCDS). SSCDS is a well-described syndrome of auditory and vestibular symptoms due to a bony dehiscence of the superior semicircular canal in the middle cranial fossa. A series of six procedures on five patients with SSCDS who underwent surgical repair via a middle fossa craniotomy were retrospectively reviewed. Preoperative and postoperative audiometric and vestibular symptoms as well as investigation findings were reviewed. Auditory and vestibular symptoms improved and hearing was preserved in all patients. The low frequency pseudo-conductive loss was corrected in four out of five patients, and the lowered preoperative cVEMP thresholds normalised following successful middle cranial fossa repair. In this series, middle fossa repair of SSCD was safe and effective with excellent sensorineural hearing preservation.

Sensitivity and specificity of computed tomography for detection of extranodal spread from metastatic head and neck squamous cell carcinoma.

AIM: To estimate the sensitivity and specificity of computed tomography used for the detection of extranodal spread of metastatic head and neck squamous cell carcinoma, by experienced head and neck radiologists. MATERIALS AND METHODS: Participants had undergone a neck dissection for head and neck squamous cell carcinoma, together with computed tomography scanning prior to surgery (accessible for reporting). Computed tomography images were independently examined by two experienced head and neck radiologists. Nodal involvement by squamous cell carcinoma and the presence or absence of extranodal spread were recorded. Results were compared to the histological specimen. The sensitivity, specificity and positive predictive value of using computed tomography for the detection of nodal involvement and presence or absence of extranodal spread were estimated, and 95 per cent confidence intervals were calculated. RESULTS AND ANALYSIS: The study analysed 149 neck dissections. When using computed tomography to detect the extranodal spread of head and neck squamous cell carcinoma, radiologists A and B had sensitivities of 66 and 80 per cent, specificities of 91 and 90 per cent, and positive predictive values of 85 and 87 per cent, respectively. DISCUSSION: The sensitivity and specificity of radiological detection of extranodal spread from head and neck squamous cell carcinoma is not well reported in the literature. Accuracy of reporting improves in the hands of experienced head and neck radiologists. This finding has clinical implications for surgical planning and adjuvant therapy requirements.