Samuel P. Gubbels

Functional auditory hair cells produced in the mammalian cochlea by in utero gene transfer

Sensory hair cells in the mammalian cochlea convert mechanical stimuli into electrical impulses that subserve audition. Loss of hair cells and their innervating neurons is the most frequent cause of hearing impairment. Atonal homologue 1 (encoded by Atoh1, also known as Math1) is a basic helix–loop–helix transcription factor required for hair-cell development, and its misexpression in vitro and in vivo generates hair-cell-like cells. Atoh1-based gene therapy to ameliorate auditory and vestibular dysfunction has been proposed. However, the biophysical properties of putative hair cells induced by Atoh1 misexpression have not been characterized. Here we show that in utero gene transfer of Atoh1 produces functional supernumerary hair cells in the mouse cochlea. The induced hair cells display stereociliary bundles, attract neuronal processes and express the ribbon synapse marker carboxy-terminal binding protein 2 (refs 12,13). Moreover, the hair cells are capable of mechanoelectrical transduction and show basolateral conductances with age-appropriate specializations. Our results demonstrate that manipulation of cell fate by transcription factor misexpression produces functional sensory cells in the postnatal mammalian cochlea. We expect that our in utero gene transfer paradigm will enable the design and validation of gene therapies to ameliorate hearing loss in mouse models of human deafness.

Head and neck manifestations of Wegener's granulomatosis.

Wegeners granulomatosis is an idiopathic, granulomatous disease with the potential for multiple head and neck manifestations. The otolarygologist is an essential part of the multidisciplinary team involved in establishing the diagnosis and providing ongoing care for patients with Wegeners granulomatosis. Diagnostic difficulties abound in Wegeners granulomatosis, making repeat biopsies and the use of ANCA imperative. Medical therapy consisting of corticosteroids and immunosuppressive agents is the mainstay of treatment in Wegeners granulomatosis, whereas surgery is reserved for selected head and neck manifestations. With appropriate medical and surgical treatment, many patients living with Wegeners granulomatosis can enjoy a good quality of life.

Advances in Molecular and Cellular Therapies for Hearing Loss

Development of effective therapeutics for hearing loss has proven to be a slow and difficult process, evidenced by the lack of restorative medicines and technologies currently available to the otolaryngologist. In large part this is attributable to the limited regenerative potential in cochlear cells and the secondary degeneration of the cochlear architecture that commonly follows sensorineural hearing impairment. Therapeutic advances have been made using animal models, particularly in regeneration and remodeling of spiral ganglion neurons, which retract and die following hair cell loss. Natural regeneration in avian and reptilian systems provides hope that replacement of hair cells is achievable in humans. The most exciting recent advancements in this field have been made in the relatively new areas of cellular replacement and gene therapy. In this review we discuss recent developments in gene- and cell-based therapy for hearing loss, including detailed analysis of therapeutic mechanisms such as RNA interference and stem cell transplantation, as well as in utero delivery to the mammalian inner ear. We explore the advantages and limitations associated with the use of these strategies for inner ear restoration.Development of effective therapeutics for hearing loss has proven to be a slow and difficult process, evidenced by the lack of restorative medicines and technologies currently available to the otolaryngologist. In large part this is attributable to the limited regenerative potential in cochlear cells and the secondary degeneration of the cochlear architecture that commonly follows sensorineural hearing impairment. Therapeutic advances have been made using animal models, particularly in regeneration and remodeling of spiral ganglion neurons, which retract and die following hair cell loss. Natural regeneration in avian and reptilian systems provides hope that replacement of hair cells is achievable in humans. The most exciting recent advancements in this field have been made in the relatively new areas of cellular replacement and gene therapy. In this review we discuss recent developments in gene- and cell-based therapy for hearing loss, including detailed analysis of therapeutic mechanisms such as RNA interference and stem cell transplantation, as well as in utero delivery to the mammalian inner ear. We explore the advantages and limitations associated with the use of these strategies for inner ear restoration.

Spontaneous Middle Fossa Encephalocele and Cerebrospinal Fluid Leakage: Diagnosis and Management

Objective: To evaluate the clinical presentation, operative findings, and surgical management of patients with spontaneous middle fossa encephalocele (SMFE) and cerebrospinal fluid (CSF) leakage repaired using a middle fossa craniotomy (MFC) approach. Study Design: Retrospective. Setting: Tertiary referral center. Patients: Fifteen consecutive patients with 16 SMFE repaired using an MFC approach between January 1999 and April 2006 were included. Interventions: Patients were evaluated clinically and radiologically with computed tomography or magnetic resonance imaging. Encephaloceles were approached via MFC, and the cranial base was repaired in multilayered fashion using a variety of materials, including hydroxyapatite cement. Patients were followed clinically after discharge. Main Outcome Measures: Postoperative complications, including CSF leak and the need for surgical revision, are evaluated. Patient factors, diagnostic testing, and operative findings are reviewed. Results: Diagnosis was made using clinical and radiologic evaluation in most patients. β2-Transferrin testing was occasionally used in the diagnostic workup. Intraoperatively, multiple defects of the floor of the middle fossa were found in more than half of patients. Fifteen SMFE in 14 patients were successfully repaired via MFC alone. One patient required revision with a combined transmastoid/MFC approach due to recurrent CSF leakage. Hydroxyapatite cement was used for repair of the cranial base in 9 patients without complication. Conclusion: An MFC approach can be used to repair SMFE with CSF leakage with a high level of success. Hydroxyapatite cement is a safe and useful adjunct to aid in reconstruction of the cranial base defects in cases of SMFE.

Long-Term Hearing Preservation After Microsurgical Excision of Vestibular Schwannoma

Objective: To examine long-term hearing outcomes after microsurgical excision of vestibular schwannoma (VS). Study Design: Retrospective case review. Setting: Tertiary referral center. Patients: Forty-nine subjects at a single institution who had undergone microsurgical excision of a VS via middle cranial fossa (MCF) approach between 1994 and 2007 with immediate postoperative (PO) hearing preservation and for whom long-term audiograms were available. Intervention: Diagnostic. Main Outcome Measures: Word Recognition Score (WRS) is defined by speech discrimination scores (SDS) greater than 70% (grade I), 50% to 70% (grade II), less than 50% (grade III), and 0% (grade IV). Results: For subjects with more than 2 years of follow-up, WRS I hearing was present PO in 42 of 49 patients and was preserved at the latest follow-up in 38 (90%) of 42 patients. No subjects fell beyond WRS II. WRS I hearing was maintained in 23 (88%) of 26 patients with more than 5 years of follow-up. Postoperative WRS I to II hearing was maintained in 28 (96%) of 29 patients with more than 5 years of follow-up. The patient who lost significant hearing in the ear operated on had sensorineural hearing loss that paralleled deterioration in her ear that was not operated on. Conclusion: Most subjects maintain their initial PO SDS after microsurgical VS removal, and therefore, the initial PO WRS is predictive of long-term hearing. Postsurgical changes do not alter the natural rate or pattern of progressive bilateral sensorineural hearing loss in individual subjects.

Electroporation-Mediated Gene Transfer to the Developing Mouse Inner Ear

The mammalian inner ear forms from a thickened patch of head ectoderm called the otic placode. The placodal ectoderm invaginates to form a cup whose edges cinch together to establish a fluid-filled sac called the otic vesicle or otocyst. The progenitor cells lining the otocyst lumen will give rise to sensory and non-sensory cells of the inner ear. These formative stages of inner ear development are initiated during the first week of postimplantation embryonic development in the mouse. The inaccessibility of the inner ear in utero has hampered efforts to gain insight into the molecular mechanisms regulating essential developmental processes. An experimental embryological method to misexpress genes in the developing mammalian inner ear is presented. Expression plasmid encoding a gene of interest is microinjected through the uterine wall into the lumen of the otocyst and electroporated into otic epithelial progenitor cells. Downstream analysis of the transfected embryonic or postnatal inner ear is then conducted to gain insight into gene function.

Tracheal reconstruction with porcine small intestine submucosa in a rabbit model

OBJECTIVE: To evaluate the ability of porcine small intestine submucosa (SIS) to 1) maintain airway patency, 2) integrate, 3) prevent granulation tissue formation, and 4) permit mucosalization when used for tracheal reconstruction. Further studies were performed to evaluate the ability of SIS to support neochondrogenesis and investigate the impact of neochondrogenesis on airway patency. STUDY DESIGN: Prospective, controlled animal trial with SIS used with and without a perichondrial flap to reconstruct a tracheal defect in a rabbit model. Functional, histologic and endoscopic analyses were performed. RESULTS: All animals except 1 control animal were without stridor. The SIS graft supported neochondrogenesis, was completely mucosalized and was well integrated into the neotrachea. There was minimal granulation tissue formation. Endoscopic analyses did not reveal a consistent, significant difference in airway patency when SIS, with or without a perichondrial flap, was used for reconstruction. CONCLUSION: SIS can be used to reconstruct a sublethal rabbit tracheal defect with no mortality and minimal morbidity.

Facial and Lower Cranial Neuropathies after Preoperative Embolization of Jugular Foramen Lesions with Ethylene Vinyl Alcohol

Objective To report 3 unique cases of cranial neuropathy after super-selective arterial embolization of jugular foramen vascular tumors with ethylene vinyl alcohol. Study Design Clinical capsule report. Setting Three tertiary academic referral hospitals. Patients Three patients who underwent superselective arterial embolization (SSE) of head and neck paragangliomas with ethylene vinyl alcohol are described. One individual was treated with primary SSE, whereas the remaining tumors were treated with preoperative SSE followed by surgical extirpation within 72 hours. All patients were found to have new cranial nerve deficits after SSE. Results One patient with isolated complete cranial nerve VII palsy demonstrated partial return of function at 8 months. One individual experienced cranial nerve VII, X, and XII palsies and demonstrated partial recovery of function of the involved facial nerve after 19 months. One subject experienced ipsilateral cranial nerve X and XI palsies after SSE and recovered full function of the spinal accessory nerve within 1 week but failed to demonstrate mobility of the ipsilateral true vocal fold. Conclusion We present the first report documenting facial and lower cranial neuropathies after super-selective embolization of head and neck paragangliomas with EVA. Although it is difficult to draw conclusions from this small number of cases, it is plausible that the use of ethylene vinyl alcohol during SSE may result in a higher risk of permanent cranial neuropathy than the use of other well-established and more temporary agents. Knowledge of the arterial supply to the cranial nerves can help the clinician to choose the embolization agent that will provide maximal occlusion while minimizing the risk of complications.

The Effect of the Palatoplasty Method on the Frequency of Ear Tube Placement

OBJECTIVE To determine whether the type of palate repair affects the frequency of subsequent ventilation tube placement. DESIGN Combined retrospective and prospective cohort with more than 2 years clinical follow-up after palatoplasty. SETTING Tertiary care childrens hospital and clinic. PATIENTS A total of 170 patients with cleft palate (with or without cleft lip) underwent palatoplasty between 1995 and 2003. Sixty-nine patients with less than 2 years of follow-up visits and 1 patient who did not require ear tubes were excluded from this analysis. INTERVENTIONS Either traditional 2-flap palatoplasty (group A) or double-opposing Z-plasty (group B) was performed. The type of palatoplasty performed was based on the reconstructive surgeons clinical decision. Ventilation tubes were placed for otitis media, conductive hearing loss, or eustachian tube dysfunction. Patients received routine follow-up care every 6 months or whenever acute problems arose. Data were analyzed with independent t tests, chi(2) tests, and Fisher exact tests. MAIN OUTCOME MEASURES Number of ear tubes placed after palatoplasty in each group. RESULTS Group A had a mean (SE) of 2.9 (0.2) sets of tubes placed, while group B had a mean (SE) of 1.8 (0.2) sets of tubes. Group A had significantly more sets of ventilation tubes placed (P < .001) than group B. Subgroup analysis based on type of cleft was performed. CONCLUSION Children with cleft palate who underwent double-opposing Z-plasty had fewer sets of ear tubes placed postoperatively than patients who had traditional repair.

Investigating long-term effects of cochlear implantation in single-sided deafness: a best practice model for longitudinal assessment of spatial hearing abilities and tinnitus handicap.

Objectives To evaluate methods for measuring long-term benefits of cochlear implantation in a patient with single-sided deafness (SSD) with respect to spatial hearing and to document improved quality of life because of reduced tinnitus. Patient A single adult male with profound right-sided sensorineural hearing loss and normal hearing in the left ear who underwent right-sided cochlear implantation. Methods The subject was evaluated at 6, 9, 12, and 18 months after implantation on speech intelligibility with specific target-masker configurations, sound localization accuracy, audiologic performance, and tinnitus handicap. Testing conditions involved the acoustic (NH) ear only, the cochlear implant (CI) ear (acoustic ear plugged), and the bilateral condition (CI+NH). Measures of spatial hearing included speech intelligibility improvement because of spatial release from masking (SRM) and sound localization. In addition, traditional measures known as “head shadow,” “binaural squelch,” and “binaural summation” were evaluated. Results The best indicator for improved speech intelligibility was SRM, in which both ears are activated, but the relative locations of target and masker(s) are manipulated. Measures that compare performance with a single ear to performance using bilateral auditory input indicated evidence of the ability to integrate inputs across the ears, possibly reflecting early binaural processing, with 12 months of bilateral input. Sound localization accuracy improved with addition of the implant, and a large improvement with respect to tinnitus handicap was observed. Conclusion Cochlear implantation resulted in improved sound localization accuracy when compared with performance using only the NH ear, and reduced tinnitus handicap was observed with use of the implant. The use of SRM addresses some of the current limitations of traditional measures of spatial and binaural hearing, as spatial cues related to target and maskers are manipulated, rather than the ear(s) tested. Sound testing methods and calculations described here are therefore recommended for assessing performance of a larger sample size of individuals with SSD who receive a CI.