Ossicular fusion and cholesteatoma in auriculo-condylar syndrome: in vivo evidence of arrest of embryogenesis.

Auriculo-condylar syndrome (ACS) is a rare condition affecting first branchial arch structures. The types of hearing loss and temporal bone findings in ACS have not been reported. We describe a 14-year-old male with constricted pinnae, mandibular dysostosis, glossoptosis, a high-arched palate, hearing loss, and cholesteatoma. Computed tomography imaging demonstrated malleoincudal joint ankylosis. The fused malleoincudal complex was removed during mastoidectomy for cholesteatoma. Electron microscopy and histopathology of the joint suggested the fusion was congenital. This is the first report of ossicular fusion and cholesteatoma in ACS and the most detailed in vivo evidence of disruption of embryogenesis during malleoincudal joint formation.

Multidimensional voice program analysis in profoundly deaf children: quantifying frequency and amplitude control.

Characterization of the vocal profile of profoundly deaf children using an objective voice analysis was carried out in a university-based pediatric otolaryngology clinic. 21 persons ages 3.5 to 18 years were assessed. From each sustained phonation of the vowel /a/ the following acoustic variables were extracted: fundamental frequency (F0), jitter percentage, shimmer percentage, fundamental frequency variation (vF0), peak amplitude variation (vAM), and first, second, and third formant frequencies (F1, F2, F3). Mean F0 was 267.8 Hz and consistent with established normative data. Mean measurements of jitter (0.88%) and shimmer (3.5%) were also within normal limits. The notable feature of the acoustic analysis was a statistically significant elevation in vF0 (2.81%) and vAM (23.58%). With the exception of one subject, the F1, F2, and F3 formant frequencies were comparable to those for normal hearing children. Auditory deprivation results in poor long-term control of frequency and amplitude during sustained phonation. The inability to maintain a sustained phonation may represent the partial collapse of an internal model of voice and speech.

Dynamics of real time DPOAE contralateral suppression in chinchillas and humans.

The dynamics of contralateral acoustic suppression were studied using real time (millisecond resolution) distortion product otoacoustic emissions (DPOAEs) in chinchillas and humans. Latency of DPOAE suppression onset is 26 ms in chinchillas and 45 ms in humans. After onset, suppression builds over time before tending to plateau, reflecting a temporal integration process with a time constant of 100 ms (chinchillas). In chinchillas, suppression persists for 40 ms even when elicited by stimuli as short as 5 ms. With stimuli >40 ms, offset and onset latencies are similar and duration of suppression equals that of the contralateral stimulus. A comparison of DPOAE suppression onset latency with neural latency data from the pathways involved suggests the following timing scheme: stimulus onset to activity in (ventral) cochlear nucleus, 4ms (15% of delay); transfer to olivocochlear efferents, 9 ms (35%); efferent conduction to presynaptic OHC site, 4ms (15%); synaptic and mechanical events at OHCs, 9 ms (35% of delay).

Is there a critical period for cochlear implantation in congenitally deaf children? Analyses of hearing and speech perception performance after implantation.

A range of basic and applied studies have demonstrated that during the development of the auditory system, early experimental manipulations or clinical interventions are generally more effective than those made later. We present a short review of these studies. We investigated this age-related plasticity in relation to the timing of cochlear implantation in deaf-from-birth children. Cochlear implantation is a standard intervention for providing hearing in children with severe to profound deafness. An important practical question is whether there is a critical period or cutoff age of implantation after which hearing outcomes are significantly reduced. In this article, we present data from prelingually deaf children (mostly congenitally deaf) implanted at ages ranging from 1 to 15 years. Each child was tested with auditory and speech understanding tests before implantation, and at regular intervals up to 8 years postimplantation. We measured the improvement in performance of speech understanding tests in younger implanted children and compared it with the results of those implanted at a later age. We also used a binary partitioning algorithm to divide the data systematically at all ages at implant to determine the optimum split, i.e., to determine the age at implant which best separates performance of early implanted versus later implanted children. We observed distinct age-of-implant cutoffs, and will discuss whether these really represent critical periods during development.

Effects of middle ear application of Cipro HC Otic Suspension in an animal model.

The objective of this study was to examine whether ciprofloxacin-containing otic drops (Cipro HC Otic Suspension; 0.2% ciprofloxacin, 0.1% hydrocortisone; Alcon, Ontario, Canada) are cochleotoxic in the chinchilla animal model. Five chinchillas in total underwent these studies. Pretreatment distortion-product otoacoustic emissions (DPOAEs) were measured in each ear, followed by a random injection of Cipro to one ear and normal saline to the other. Injections consisted of 0.2 mL into the middle ear cavity (bulla) for 5 consecutive days. Post-treatment DPOAEs and auditory brainstem responses were measured at 1 month, and cochlear hair cell integrity was assessed by scanning electron microscopy (SEM). All animals had normal pretreatment DPOAEs. One month after Cipro instillation, DPOAE levels decreased in three of the animals. No significant change was seen in the ears treated with saline. On SEM examination, the integrity of the stereocilia of the inner and outer hair cells demonstrated no histologic evidence of significant cochlear damage. The finding of reduced DPOAEs suggests a mild local middle ear inflammation caused by the ciprofloxacin or some other component or property of Cipro.

Cerebral vascular abnormalities in a murine model of hereditary hemorrhagic telangiectasia.

BACKGROUND AND PURPOSE: Hereditary hemorrhagic telangiectasia type 1 (HHT1) is an autosomal dominant vascular dysplasia caused by mutations in the endoglin gene and characterized by dilated vessels and arteriovenous malformations (AVMs). To understand the etiology of this disorder, we evaluated the cerebral vasculature of endoglin heterozygous (Eng+/-) mice, which represent the only animal model of HHT1. METHODS: The cerebral vasculature of Eng+/- and Eng+/+ mice from C57BL/6 (B6) and 129/Ola (129) strains with a differential susceptibility to HHT1 was studied with corrosion casting. Casts were observed by scanning electron microscopy to detect malformations and evaluate arterial diameters and orientation of endothelial nuclei. Measurements were taken to assess relative constriction at arteriolar branching points and downstream relative dilatation. RESULTS: Three of 10 Eng+/- mice demonstrated abnormal vascular findings including AVMs, while none of 15 Eng+/+ mice did. The incidence of relative constriction at arteriolar branching points was significantly less in both Eng+/- groups than in their Eng+/+ counterparts. The occurrence of relative dilatation was significantly greater in B6-Eng+/- than in B6-Eng+/+ mice. Endothelial nuclei were significantly rounder and deviated more from the direction of blood flow in Eng+/- than in Eng+/+ mice. CONCLUSIONS: Eng+/- mice showed significant structural alterations in cerebral blood vessels, indicating that the level of endoglin on endothelium is critical for maintenance of normal vasculature. Since endoglin haploinsufficiency is associated with HHT1, such changes in arteriolar structures might occur in HHT1 patients and predispose them to AVMs and their sequelae.

Influence of age at implantation and of residual hearing on speech outcome measures after cochlear implantation: binary partitioning analysis.

The goal of this study was to evaluate speech understanding outcomes in prelingually deaf children who use a cochlear implant device. Specifically, we discuss investigations on 2 prognostic variables--age at implantation and degree of residual hearing--and use a novel method: binary partitioning analysis. Our outcome measures are standard speech perception evaluations, including the Word Intelligibility by Picture Identification (WIPI) test, the Phonetically Balanced-Kindergarten (PBK) test, and the Glendonald Auditory Screening Procedure (GASP). Regarding age at implantation, we definitely showed that growth rates of speech understanding do relate to age at implantation, but not in a simple fashion. We used binary partitioning in an attempt to find the age at implantation that best separates the performances of children with younger versus older ages at implantation. We found that there is no one "critical age"; much appears to depend on the nature and difficulty (eg, whether open- or closed-set) of the test used. Regarding residual hearing, binary partitioning analysis was unable to show that the amount of residual hearing (as shown by preimplantation audiometric data) has any significant bearing on speech outcome measures in congenitally or prelingually deaf children.

Blood capillary distribution correlates with hemodynamic-based functional imaging in cerebral cortex.

Our study concerns the mechanisms that underlie functional imaging of sensory areas of cortex using hemodynamic-based methods such as optical imaging of intrinsic signals, functional magnetic resonance imaging and positron emission tomography. In temporal cortex of chinchilla, we have used optical imaging of intrinsic signals evoked by acoustic stimulation to define the functionally responsive area and then made (scanning electron microscopy) observations of the corresponding capillary networks prepared by corrosion cast methods. We report that intrinsic signals associated with auditory cortex correlate directly with discrete capillary beds. These capillary beds, within the cortical surface layers, are distributed across the cortex in a non-uniform fashion. Within cortex both the arterial supply and the capillary network contain various flow control structures. Our study suggests a causal relationship between the metabolic demands of local neuronal activity and both the density of the capillary network and the placement of the control structures. Such relationships will affect the ultimate spatial resolution obtainable by hemodynamic-based functional brain imaging studies. These relationships will also affect quantitative comparisons of activity levels in different areas of cortex.