Paraneoplastic cochleovestibulopathy: clinical presentations, oncological and serological associations.

OBJECTIVE: Cochleovestibulopathy is a distinguishable paraneoplastic phenotype. In this study, we evaluate clinical presentation, serological/cancer associations and outcomes of paraneoplastic cochleovestibulopathy. METHODS: Retrospective chart review of patients with hearing impairment and/or vestibulopathy who underwent serological evaluations for paraneoplastic antibodies between January 2007 and February 2021 was performed. RESULTS: Twenty-six patients were identified (men, n=23; median age, 45 years, range: 28-70). Biomarkers detected included: KLHL11-IgG| |(n=20,| |77% (coexisting LUZP4-IgG, n=8)),| ||ANNA1-IgG| | |(n=3,| |12%),| |amphiphysin-IgG|| |(n=2,| |8%)| |and| |LUZP4-IgG|| |(n=1,| |4%). Most common neoplastic association was |testicular|/|extra-testicular| |seminoma| | (n=13,| |50%).|| Hearing| impairment (bilateral, 62%) was |present| |in| |all| |patients.| |Fifteen patients (58%) had cochleovestibular dysfunction as their initial presentation before rhombencephalitis/encephalomyelitis manifestations (hearing loss, four; acute vertigo, eight; both, three). |Brain| |MRI| |demonstrated| |internal| |auditory| |canal| |enhancement| |in| |four |patients.| Audiometry commonly revealed severe-profound bilateral sensorineural hearing loss. Most patients |had| a refractory course |despite| |immunotherapy| |and/or| |cancer| |treatment|. CONCLUSION: Cochleovestibulopathy commonly presents with rapidly progressive bilateral hearing loss and/or acute vertigo. However, in some patients, these symptoms present along with or following brainstem/cerebellar manifestations. KLHL11-IgG and seminoma are the most common serological and cancer associations, respectively. Recognition of this phenotype may aid in earlier diagnosis of paraneoplastic autoimmunity and associated cancer.

Protective effect of lutein against acrolein-induced ototoxicity in rats.

BACKGROUND: Acrolein is a reactive aldehyde that forms during burning of wood and other fuels. It is also a product of lipid peroxidation (LPO) reactions and is present in cigarette smoke. Acrolein is known to cause oxidative stress and inflammatory nerve tissue damage. Lutein is a tetraterpenoid molecule with antioxidant and anti-inflammatory properties. There appear to be no studies on the effect of lutein on vestibulocochlear nerve damage induced by acrolein. The aim of this study was to investigate the effect of lutein on vestibulocochlear nerve damage induced by acrolein in rats using biochemical and histopathological methods. METHODS: The rats were divided into three groups (n = 6, for each group) a healthy control group (HG), an acrolein (ACR) group and a lutein and acrolein (LACR) group. In the LACR group, lutein was administered (1 mg/kg) via oral gavage. The ACR and HG groups received saline via oral gavage. Then, 1 h after the administration of lutein and saline, the LACR and ACR groups were treated with 3 mg/kg of acrolein via oral gavage. This procedure was repeated once a day for 30 days. RESULTS: The results of biochemical experiments showed that in the vestibulocochlear nerve tissues of the animals treated with acrolein, the levels of malondialdehyde, total oxidants, nuclear factor kappa b, tumor necrosis factor alpha and interleukin 1 beta significantly increased, whereas the levels of total glutathione and total antioxidants decreased as compared to those in the HG and LACR groups. In addition, severe histopathological damage was observed in vestibulocochlear nerve tissue of the acrolein group, whereas this damage was alleviated in the lutein group. CONCLUSION: Lutein protected vestibulocochlear nerve tissue from acrolein-associated oxidative and proinflammatory damage. This suggests that lutein might be useful in preventing or treating acrolein-induced ototoxicity.

Vestibular mapping in patients with unilateral peripheral-vestibular deficits.

OBJECTIVE: To test the hypothesis that patterns of semicircular canal (SCC) and otolith impairment in unilateral vestibular loss depend on the underlying disorders, we analyzed peripheral-vestibular function of all 5 vestibular sensors. METHODS: For this retrospective case series, we screened the hospital video-head-impulse test database (n = 4,983) for patients with unilaterally impaired SCC function who also received ocular vestibular-evoked myogenic potentials and cervical vestibular-evoked myogenic potentials (n = 302). Frequency of impairment of vestibular end organs (horizontal/anterior/posterior SCC, utriculus/sacculus) was analyzed with hierarchical cluster analysis and correlated with the underlying etiology. RESULTS: Acute vestibular neuropathy (AVN) (37.4%, 113 of 302), vestibular schwannoma (18.2%, 55 of 302), and acute cochleovestibular neuropathy (6.6%, 20 of 302) were most frequent. Horizontal SCC impairment (87.4%, 264 of 302) was more frequent (p < 0.001) than posterior (47.4%, 143 of 302) and anterior (37.8%, 114 of 302) SCC impairment. Utricular damage (58%, 175 of 302) was noted more often (p = 0.003) than saccular impairment (32%, 98 of 302). On average, 2.6 (95% confidence interval 2.48-2.78) vestibular sensors were deficient, with higher numbers (p ≤ 0.017) for acute cochleovestibular neuropathy and vestibular schwannoma than for AVN, Menière disease, and episodic vestibular syndrome. In hierarchical cluster analysis, early mergers (posterior SCC/sacculus; anterior SCC/utriculus) pointed to closer pathophysiologic association of these sensors, whereas the late merger of the horizontal canal indicated a more distinct state. CONCLUSIONS: While the extent and pattern of vestibular impairment critically depended on the underlying disorder, more limited damage in AVN and Menière disease was noted, emphasizing the individual range of loss of function and the value of vestibular mapping. Likely, both the anatomic properties of the different vestibular end organs and their vulnerability to external factors contribute to the relative sparing of the vertical canals and the sacculus.

Endoglin-based assessment of neoangiogenesis in sporadic VIII cranial nerve schwannoma.

Although the diagnosis and treatment of sporadic vestibular schwannoma has improved in recent years, no factors capable of predicting its growth have been identified as yet. Endoglin (CD105) is a proliferation-associated protein expressed in angiogenic endothelial cells, and a potential prognostic indicator for several solid tumors. The aim of the present study was primarily to investigate the expression and role of CD105 in a series of sporadic vestibular nerve schwannomas. In 71 consecutive cases of vestibular schwannoma, vessel cross-sectional area and density were calculated from immunohistochemically assessed CD105 expression using image analysis to correlate them with: (i) tumor dimensions; and (ii) tumor growth rate measured on high-resolution contrast-enhanced MRI (ceMRI). Based on assessments of CD105 expression, a significant positive correlation was identified between vessel cross-sectional area and tumor size at the time of surgery (p = 0.0024), and between vessel density and tumor size (p = 0.013). Vessel cross-sectional area (p = 0.0006) and vessel density (p = 0.003) were significantly greater in tumors measuring ≥10 mm in size than in those <10 mm. Conversely, when tumor growth rate could be calculated from two or more ceMRI (38 cases), there was no significant correlation between tumor growth rate and cross-sectional vessel area or vessel density as assessed with CD105. Further investigations are needed to ascertain the feasibility of: (i) using circulating endoglin assay to monitor tumor growth; and (ii) targeting neoangiogenesis with anti-endoglin antibodies in sporadic vestibular schwannoma.

Ataxia in a Young Female.

Neurofibromatosis type 2 (NF2) is a genetically inherited disorder characterized by the presence of multiple central nervous system tumours, most pathognomonic being bilateral vestibular schwannomas with or without peripheral manifestations in the form of cataract or cutaneous neurofibromas. NF2 is an uncommon disorder compared to NF1. We describe a classical case of neurofibromatosis type 2 with florid clinical manifestations and characteristic neuroimaging features. We also briefly describe the literature pertaining to this rare disorder. The case also emphasizes the fact that NF2 should be considered in the list of differentials for ataxia especially when it is associated with sensory neural hearing loss.

Solitary Metastasis to the Facial/Vestibulocochlear Nerve Complex: Case Report and Review of the Literature.

BACKGROUND: Distant metastasis of mucinous adenocarcinoma from the gastrointestinal tract, ovaries, pancreas, lungs, breast, or urogenital system is a well-described entity. Mucinous adenocarcinomas from different primary sites are histologically identical with gland cells producing a copious amount of mucin. This report describes a very rare solitary metastasis of a mucinous adenocarcinoma of unknown origin to the facial/vestibulocochlear nerve complex in the cerebellopontine angle. CASE DESCRIPTION: A 71-year-old woman presented with several month history of progressive neurological decline and a negative extensive workup performed elsewhere. She presented to our institution with complete left facial weakness, left-sided deafness, gait unsteadiness, headache and anorexia. A repeat magnetic resonance imaging scan of the head revealed a cystic, enhancing abnormality involving the left cerebellopontine angle and internal auditory canal. A left retrosigmoid craniotomy was performed and the lesion was completely resected. The final pathology was a mucinous adenocarcinoma of indeterminate origin. Postoperatively, the patient continued with her preoperative deficits and subsequently died of her systemic disease 6 weeks after discharge. CONCLUSIONS: The facial/vestibulocochlear nerve complex is an unusual location for metastatic disease in the central nervous system. Clinicians should consider metastatic tumor as the possible etiology of an unusual appearing mass in this location causing profound neurological deficits. The prognosis after metastatic mucinous adenocarcinoma to the cranial nerves in the cerebellopontine angle may be poor.

Phase II study of mTORC1 inhibition by everolimus in neurofibromatosis type 2 patients with growing vestibular schwannomas.

Neurofibromatosis type 2 (NF2) is a genetic disorder with bilateral vestibular schwannomas (VS) as the most frequent manifestation. Merlin, the NF2 tumor suppressor, was identified as a negative regulator of mammalian target of rapamycin complex 1. Pre-clinical data in mice showed that mTORC1 inhibition delayed growth of NF2-schwannomas. We conducted a prospective single-institution open-label phase II study to evaluate the effects of everolimus in ten NF2 patients with progressive VS. Drug activity was monitored every 3 months. Everolimus was administered orally for 12 months and, if the decrease in tumor volume was >20 % from baseline, treatment was continued for 12 additional months. Other patients stopped when completed 12 months of everolimus but were allowed to resume treatment when VS volume was >20 % during 1 year follow-up. Nine patients were evaluable. Safety was evaluated using CTCAE 3.0 criteria. After 12 months of everolimus, no reduction in volume ≥20 % was observed. Four patients had progressive disease, and five patients had stable disease with a median annual growth rate decreasing from 67 %/year before treatment to 0.5 %/year during treatment. In these patients, tumor growth resumed within 3-6 months after treatment discontinuation. Everolimus was then reintroduced and VS decreased by a median 6.8 % at 24 months. Time to tumor progression increased threefold from 4.2 months before treatment to > 12 months. Hearing was stable under treatment. The safety of everolimus was manageable. Although the primary endpoint was not reached, further studies are required to confirm the potential for stabilization of everolimus.

Atypical teratoid/rhabdoid tumor (AT/RT) arising from the acoustic nerve in a young adult: a case report and a review of literature.

Atypical teratoid/rhabdoid tumors (AT/RTs) are rare, highly malignant central nervous system tumors that predominantly occur in young children. A 22-year-old woman presented with a 4-year history of relapsing tinnitus and gradual hearing loss. Neuroimaging revealed an enhanced intrinsic left internal auditory canal mass. The patient underwent radiotherapy treatment. Three years later, the tumor size continued to increase, as observed by imaging, and ultimately evolved into the left cerebellopontine angle. As a consequence, a total tumor resection was performed, and a pathological diagnosis of AT/RT was made. Aggressive radiotherapy and chemotherapy treatment continued; however, the tumor recurred within 11 months after the total tumor resection. The patient died within 4 months of the second operation. Histopathologically, the tumor contained characteristic rhabdoid cells with areas that resembled a classical primitive neuroectodermal tumor. Immunostaining showed loss of INI1 protein expression in tumor cells, and fluorescence in situ hybridization showed a hemizygous deletion of the hSNF5/INI1 gene region on 22q11.2. This is the first report of an AT/RT that arised from the acoustic nerve in a young adult. Despite manifold diagnostic and therapeutic advances, the prognosis of patients with AT/RT remains poor.

Pontine tegmental cap dysplasia: report of two new cases from Kuwait.

We describe two patients (a Filipino boy aged 2.7 years and a Kuwaiti girl aged 4.8 Years) with clinical and MRI findings consistent with the diagnosis of pontine tegmental cap dysplasia (PTCD) and compare them with 23 other cases reported in the literature. Both presented with feeding problems (VII nerve), sensori-neural deafness (VIII nerve) and hypotonia from birth and later developed corneal opacities due to loss of corneal sensation (V nerve). They have severe psychomotor developmental delay. The MRI of their brain showed a flattened ventral pons, vaulted "cap"- like structure protruding into 4th ventricle and a "molar tooth" sign. One of our patients also had Tetralogy of Fallot (TOF) successfully corrected. The other had no extracranial manifestations. The findings in our patients are similar to those reported except for the occurrence of TOF which has not been reported before in association with PTCD.

Indications and contraindications of auditory brainstem implants: systematic review and illustrative cases.

The number of non-neurofibromatosis type 2 (NF2) indications for auditory brainstem implant (ABI) in the literature is increasing. The objective of this study was to analyze and discuss the indications for ABI. Retrospective chart review and systematic review were conducted at Quaternary referral skull base center and referring centers. Analysis of ABI cases with non-NF2 indications and systematic review presenting non-NF2 ABI cases were performed. Fourteen referred cases with ABI were identified. All cases had unsatisfactory results of ABI and all could have been rehabilitated with a cochlear implant (CI). Of these 14 cases, 9 improved with a cochlear implant, and 2 with a hearing aid, two are still planned for CI, one received bilateral CI, no ABI. In literature, we found 31 articles presenting 144 non-NF2 ABI cases with at least 7 different indications other than NF2. ABI should be restricted to those patients who have no other rehabilitation options. Patency of the cochlea and evidence of an intact cochlear nerve should be examined with imaging and electrophysiologic testing. Sometimes a CI trial should be planned prior to proceeding with ABI. We have shown that in many cases a CI is still possible and CI provided better results than ABI. In vestibular schwannoma in the only hearing ear, cochlear otosclerosis, temporal bone fractures, (presumed) bilateral traumatic cochlear nerve disruption, auto-immune inner ear disease and auditory neuropathy primarily CI are indicated. Traumatic bilateral cochlear nerve disruption is exceptionally unlikely. In cochlear nerve aplasia, testing should be performed prior to meeting indications for ABI. In malformations, ABI is indicated only in severe cochlear hypoplasia or cochlear aplasia.

The vestibulocochlear nerve (VIII).

The vestibulocochlear nerve (8th cranial nerve) is a sensory nerve. It is made up of two nerves, the cochlear, which transmits sound and the vestibular which controls balance. It is an intracranial nerve which runs from the sensory receptors in the internal ear to the brain stem nuclei and finally to the auditory areas: the post-central gyrus and superior temporal auditory cortex. The most common lesions responsible for damage to VIII are vestibular Schwannomas. This report reviews the anatomy and various investigations of the nerve.

Rapidly progressive epithelioid malignant peripheral nerve sheath tumor of the vestibular nerve.

OBJECTIVE: Spontaneous malignant peripheral nerve sheath tumors (MPNSTs) arising from the vestibular nerve are extremely rare. In this report, we detail the case of one such tumor including the first report of its response to radiosurgery. PATIENTS: A 73-year-old woman presented with subacute sensorineural hearing loss, retroauricular pain, and facial nerve palsy. INTERVENTIONS: Magnetic resonance imaging (MRI) was obtained demonstrating findings suggestive of a vestibular schwannoma. The patient elected for gamma knife radiosurgery and 13 gray were administered to the lesion. Repeat MRIs showed that the mass quickly regressed after radiosurgery but recurred by 5 months. Subsequent microsurgical resection revealed an aggressive epithelioid MPNST of the vestibular nerve. MAIN OUTCOMES MEASURES: Interval MRI results, histopathology, and immunohistochemistry. RESULTS: We present radiographic and histopathologic confirmation of the malignant nature of this extremely rare lesion. We also document its rapid response after radiosurgery as further indication of the malignant nature of this lesion. CONCLUSION: Early and complete resection of internal auditory canal masses with atypical clinical courses suggestive of malignancy is the best initial option to treat these tumors with the understanding that further treatment with radiation or chemotherapy is essential.

Otopathology in idiopathic Dandy's syndrome.

BACKGROUND: Dandy's syndrome, or bilateral vestibular hypofunction and oscillopsia, may cause chronic disequilibrium aggravated by head movement or in the presence of reduced light. It may be secondary to ototoxicity, central nervous system tumors, Ménière's syndrome, infections, or trauma or may be idiopathic. OBJECTIVE: To describe the temporal bone histopathology in one individual with idiopathic Dandy's syndrome. MATERIALS AND METHODS: Temporal bones from 1 individual were removed at autopsy and studied using light and Nomarski microscopy. RESULTS: In this case, the otopathology demonstrated vestibular atelectasis of the membranous labyrinth of the superior, lateral, and posterior semicircular canals but not the utricle or saccule bilaterally. The findings also included mild hair cell loss in the cristae of all semicircular canals and of the utricular and saccular maculae and severely reduced neuronal count in Scarpa's ganglion bilaterally. There was also a scattered loss of inner and outer hair cells throughout the cochlea and moderate-to-severe loss of cochlear neurons bilaterally. CONCLUSION: We have reported the histopathologic findings in a case of idiopathic Dandy's syndrome. Both temporal bones showed vestibular atelectasis of all three semicircular canals, preservation of normal saccule and utricle, and severe reduction of the neuronal population in Scarpa's ganglion bilaterally. Both ears also showed substantial degeneration of the spiral ganglion of the cochleas. Severe Scarpa's ganglion degeneration was also noted in the only other case of idiopathic Dandy's Syndrome in the literature. However, that other case had no evidence of vestibular atelectasis and had normal hearing.

Loss of osteoprotegerin expression in the inner ear causes degeneration of the cochlear nerve and sensorineural hearing loss.

Osteoprotegerin (OPG) is a key regulator of bone remodeling. Mutations and variations in the OPG gene cause many human diseases that are characterized by not only skeletal abnormalities but also poorly understood hearing loss: Paget's disease, osteoporosis, and celiac disease. To gain insight into the mechanisms of hearing loss in OPG deficiency, we studied OPG knockout (Opg(-/-)) mice. We show that they develop sensorineural hearing loss, in addition to conductive hearing loss due to abnormal middle-ear bones. OPG deficiency caused demyelination and degeneration of the cochlear nerve in vivo. It also activated ERK, sensitized spiral ganglion cells (SGC) to apoptosis, and inhibited proliferation and survival of cochlear stem cells in vitro, which could be rescued by treatment with exogenous OPG, an ERK inhibitor, or bisphosphonate. Our results demonstrate a novel role for OPG in the regulation of SGC survival, and suggest a mechanism for sensorineural hearing loss in OPG deficiency.

Clinical characteristics of children with cochlear nerve dysplasias.

OBJECTIVES/HYPOTHESIS: To describe the clinical and audiometric characteristics of children with cochlear nerve dysplasia (CND). STUDY DESIGN: Retrospective chart review of clinical database of children with inner ear anomalies treated at a tertiary care children's hospital. METHODS: Institutional review board-approved retrospective review from June 30, 2006, to July 1, 2011; 18 children were identified with magnetic resonance imaging (MRI) evidence of CND defined as a cochlear nerve 50% smaller than the adjacent facial nerve. RESULTS: Of the 18 patients, nine were girls and nine were boys. Average age at time of MRI diagnosis of CND was 4.6 years. Twelve children had cochlear nerve aplasia, and six had hypoplasia. Three were affected bilaterally: two with aplasia and one with hypoplasia. Unilateral dysplasia was found in 15 children; of these, 60% occurred on the left side. Other inner ear anomalies were found in 50%, including all patients with bilateral CND. Severe-to-profound hearing loss was found in the involved ear(s) in 14 of 18 patients, including all bilateral patients. Of the 18 patients tested, 13 (72%) had an audiometric profile of auditory neuropathy/dys-synchrony syndrome (auditory neuropathy spectrum disorder [ANSD]). Comorbid conditions were present in 56% of patients. Two patients were syndromic. Family history of hearing loss was present in 11% of patients. CONCLUSIONS: Many patients with CND have ANSD, and more than half have comorbidities. Approximately half of affected patients have other inner ear anomalies in the involved ears. Unilateral CND may be more common on the left side.

Neuromuscular choristoma of the internal auditory meatus.

Choristomas of the internal auditory meatus are exceedingly rare tumors. In most cases, neuromuscular choristomas have initially been misdiagnosed as vestibular schwannomas (VS). No known characteristics in the clinical presentation or in imaging exist distinguishing these tumors from VS, which are the most common tumors at this location [Smith et al.: AJNR Am J Neuroradiol 1997;18:327-329]. We present a case of a neuromuscular choristoma of the 8th cranial nerve that was operated because of growth demonstrated on two MRI scans 3 months apart. We were convinced that this young patient would require treatment sometime in the future, and we believed that an operation at that time had higher chances to preserve the anatomical structures. Histomorphological examination of the tumor revealed a nodular lesion with fascicular and nodular assembled smooth muscle cells, connective tissue and nerve fibers.

Cochleovestibular nerve involvement in multifocal fibrosclerosis.

OBJECTIVES: To report a case of multifocal fibrosclerosis with a nine-year follow up, and to discuss this disease's radiological appearance and management. The disease is a rare systemic disorder of unknown cause characterised by fibrous proliferation involving multiple anatomical sites. CASE REPORT: A 50-year-old woman presented with histological findings characterised by similar inflammatory processes involving the meninges, pituitary gland, peritoneum, retroperitoneum and orbits, prompting a search for a common pathophysiology. A diagnosis of multifocal fibrosclerosis was postulated. Symptom improvement was noted after treatment with prednisone and azathioprine. CONCLUSION: This is the first documented case of involvement of the cochleovestibular nerve in a patient with multifocal fibrosclerosis. The rare association between fibrotic diseases and masses showing various clinical patterns should be kept in mind by otolaryngologists, and imaging performed to investigate for multifocal fibrosclerosis. However, diagnosis can only be confirmed with tissue biopsy and histopathological examination.

Malignant peripheral nerve sheath tumor of the vestibulocochlear nerve and brainstem: multimodality treatment with survival of 27 months. A case report and review of the literature.

BACKGROUND AND IMPORTANCE: Malignant peripheral nerve sheath tumors are the most common malignant mesenchymal tumors of soft tissues, but they are very rare when found to arise from a cranial nerve and when not in association with neurofibromatosis. These tumors are highly malignant and carry a poor prognosis with survival usually less than 6 months. CLINICAL PRESENTATION: The authors report the case of a 23-year-old female with no history of phakomatoses, previous irradiation, or known genetic disorders, who presented with a malignant peripheral nerve sheath tumor of the vestibulocochlear nerve and brainstem. Multiple staged skull base approaches were carried out with maximal possible resection. Adjunctive therapies including standard radiation therapy, intensity-modulated radiation therapy, and stereotactic gamma knife radiosurgery were used with an ultimate patient survival of 27 months. CONCLUSION: To our knowledge, this is the first report describing a patient with a malignant peripheral nerve sheath tumor of the vestibulocochlear nerve and brainstem treated with staged surgical approaches in conjunction with multiple forms of radiotherapy and having a significant survival of more than 2 years.

Primary glioblastoma of the cerebellopontine angle in adults.

Gliomas are rare entities in the cerebellopontine angle (CPA) in adults. The authors present clinical, neuroradiological, serological, and neuropathological findings in a 60-year-old man with an extraaxial CPA glioblastoma arising from the proximal portion of cranial nerve VIII. The patient presented with progressive left-sided deafness and left-sided facial palsy lasting less than 2 months and progressive dysarthria and dysphagia lasting 2 weeks. Preoperative neuroimaging suggested the diagnosis of CPA meningioma with "dural-tail" sign and involvement of the internal auditory canal. Serological examination showed an increase in the malignant markers of ferritin and neuron-specific enolase, which suggested underlying malignancy. The tumor was subtotally removed, and it was confirmed to be completely separated from the brainstem and cerebellum. Cranial nerves VII and VIII were destroyed and sacrificed. Transient severe bradycardia occurred during surgery due to entrapment of the caudal cranial nerve complex by the tumor in such an infiltrative way. The neuropathological examination revealed a glioblastoma. The patient underwent no further treatment and died of cachexia 2 months postoperatively. To the authors' knowledge, this represents the first case of a primary glioblastoma in the CPA in an adult. A high index of suspicion along with reliance on clinical assessment, radiological findings, and serum detection of specific malignant markers is essential to diagnose such uncommon CPA lesions.

Brain stem responses evoked by stimulation with an auditory brain stem implant in children with cochlear nerve aplasia or hypoplasia.

OBJECTIVES: The inclusion criteria for an auditory brain stem implant (ABI) have been extended beyond the traditional, postlingually deafened adult with Neurofibromatosis type 2, to include children who are born deaf due to cochlear nerve aplasia or hypoplasia and for whom a cochlear implant is not an option. Fitting the ABI for these new candidates presents a challenge, and intraoperative electrically evoked auditory brain stem responses (EABRs) may assist in the surgical placement of the electrode array over the dorsal and ventral cochlear nucleus in the brain stem and in the postoperative programming of the device. This study had four objectives: (1) to characterize the EABR by stimulation of the cochlear nucleus in children, (2) to establish whether there are any changes between the EABR recorded intraoperatively and again just before initial behavioral testing with the device, (3) to establish whether there is evidence of morphology changes in the EABR depending on the site of stimulation with the ABI, and (4) to investigate how the EABR relates to behavioral measurements and the presence of auditory and nonauditory sensations perceived with the ABI at initial device activation. DESIGN: Intra- and postoperative EABRs were recorded from six congenitally deaf children with ABIs, four boys and two girls, mean age 4.2 yrs (range 3.2 to 5.0 yrs). The ABI was stimulated at nine different bipolar sites on the array, and the EABRs recorded were analyzed with respect to the morphology and peak latency with site of stimulation for each recording session. The relationship between the EABR waveforms and the presence or absence of auditory electrodes at initial device activation was investigated. The EABR threshold levels were compared with the behavioral threshold (T) and comfortably loud (C) levels of stimulation required at initial device activation. RESULTS: EABRs were elicited from all children on both test occasions. Responses contained a possible combination of one to three peaks from a total of four identifiable peaks with mean latencies of 1.04, 1.81, 2.61, and 3.58 msecs, respectively. The presence of an EABR was a good predictor of an auditory response; however, the absence of the EABR was poor at predicting a site with no auditory response. The morphology of EABRs often varied with site of stimulation and between EABR test occasions. Postoperatively, there was a trend for P1, P3, and P4 to be present at the lateral end of the array and P2 at the medial end of the array. Behavioral T and C levels showed a good correlation with postoperative EABR thresholds but a poor correlation with intraoperative EABR thresholds. CONCLUSIONS: The presence of an intraoperative EABR was a good indicator for the location of electrodes on the ABI array that provided auditory sensations. The morphology of the EABR was often variable within and between test sessions. The postoperative EABR thresholds did correlate with the behavioral T and C levels and could be used to assist with initial device fitting.