Search PubMed⌕ Search

Biomedical subjects

Daniel I Choo

Publications and source records attributed to Daniel I Choo.

11 recordsLinked to original sources
PubMed2004

Genomic organization and expression analysis of the murine Fam3c gene.

Previously, we identified FAM3C as a candidate gene for autosomal recessive nonsyndromic hearing loss locus 17 (DFNB17). This gene has since been found to be a member of a cytokine-like gene family, but its function has not been determined. The purpose of this study was thus to elucidate the gene structure and pattern of expression, providing information that might allow a hypothesis to be developed about FAM3C function of in the inner ear. To do this we analyzed its mouse ortholog, Fam3c. Fam3c was found to be ubiquitously expressed in all analyzed tissues, and had two major transcript variants presumed to result from an alternative use of two distinct polyadenylation signals. In situ hybridization experiments revealed a predominant Fam3c pattern of expression in the nonsensory epithelium of the growing semicircular canals at embryonic day (E) 15.5. This expression pattern resembles the known pattern of the Nkx5 homeobox genes. Analysis of the Fam3c promoter region demonstrated a putative Nkx5.1 binding site. Based on our findings, we hypothesize that Fam3c may be a downstream target gene for the Nkx5.1 transcription factor, and may thus be involved in cell differentiation and proliferation during inner ear embryogenesis. Additionally, analyses of putative amino acid sequences of FAM3C orthologous proteins showed that their primary and secondary structures and overall topology were highly conserved. Further study is underway to determine the role of FAM3C in inner ear development.

Amino Acid Sequence↗
PubMed2004

A diagnostic paradigm for childhood idiopathic sensorineural hearing loss.

OBJECTIVE: Our objective was to determine the diagnostic yield of laboratory testing, radiological imaging, and GJB2 mutation screening in a large cohort of patients with differing severities of idiopathic sensorineural hearing loss (SNHL). DESIGN AND SETTING: We undertook a retrospective study of patients presenting with SNHL at our institution from 1993 to 2002. RESULTS: Laboratory testing had an extremely low yield. Patients with unilateral SNHL had a significantly higher imaging yield than those with bilateral. The diagnostic yield of GJB2 screening was significantly higher in patients with severe to profound SNHL than in those with less severe SNHL. However, a relatively large number of patients with mild to moderate SNHL had positive GJB2 screens. CONCLUSIONS: Based on diagnostic yields, we propose a cost-effective stepwise diagnostic paradigm to replace the more commonly used and costly simultaneous testing approach. EBM RATING: C.

Adolescent↗
PubMed2004

Refining the DFNB17 interval in consanguineous Indian families.

We previously mapped the DFNB17 locus to a 3-4 cM interval on human chromosome 7q31 in a large consanguineous Indian family with congenital profound sensorineural hearing loss. To further refine this interval, 30 new highly polymorphic markers and 8 SNPs were analyzed against the pedigree. Re-analysis in the original DFNB 17 family and additional data from a second unrelated consanguineous family with congenital deafness found to map to the interval, limited the area of shared homozygosity-by-descent (HBD) to approximately 4 megabase (Mb) between markers D7S2453 and D7S525. Nineteen known genes and over 20 other cDNAs have been identified in the refined DFNB 17 interval, including the SLC26A4 gene. We have analyzed 4 other cochlear-expressed genes that map to the DFNB17 interval as candidate genes. Analysis of coding and splice site regions of these cochlear expressed genes did not reveal any disease causing mutations. Further study of other candidate genes is currently underway.

Chromosome Mapping↗
PubMed2004

Functional magnetic resonance imaging: contemporary and future use.

PURPOSE OF REVIEW: Functional magnetic resonance imaging is a relatively new neuroimaging technique that is being used in both research and clinical applications. Increasing work has been done to elucidate the auditory cortex. RECENT FINDINGS: Current studies focus on enhancing the sensitivity of functional magnetic resonance imaging in studying the auditory cortex and subcortical pathways in response to tonal stimulation, to evaluate the integrity of the auditory cortex before cochlear implantation, and as a screening tool for hearing impairment in the young child. SUMMARY: Recent work has been encouraging: silent functional magnetic resonance imaging techniques allow for better evaluation of the auditory cortex with less confounding scanner noises. Functional magnetic resonance imaging can be safely and reproducibly performed in hearing-impaired children and in the preoperative evaluation of candidates for cochlear implantation.

Adult↗
PubMed2004

The cochlear cleft.

BACKGROUND AND PURPOSE: Recent advances in the display of medical images permit the routine study of temporal bone CT images at high magnification. We noted an unfamiliar structure, which we now call the "cochlear cleft," in the otic capsule. To our knowledge, this report represents the first description of this structure in the medical imaging literature. METHODS: Temporal bone CT performed in 100 pediatric patients without sensorineural hearing loss were examined for the presence of cochlear clefts. Incidence of cochlear clefts as well as the relationship between age and incidence was examined. RESULTS: Cochlear clefts were present in 41% of the subjects. Incidence decreased with age. CONCLUSION: We describe a cleft in the otic capsule that is frequently seen on magnified images of temporal bone CT studies in children. The cleft may be the fissula ante fenestram.

Adolescent↗
PubMed2003

Genotypic and phenotypic correlations of DFNB1-related hearing impairment in the Midwestern United States.

OBJECTIVE: To determine the genotypic and phenotypic correlations of hearing impairment (HI) in a midwestern US population related to autosomal recessive nonsyndromic hearing loss locus 1 (DFNB1). DESIGN: A retrospective review. SETTING: Tertiary care children's hospital. PATIENTS: A total of 160 consecutive children diagnosed with idiopathic sensorineural hearing loss. MAIN OUTCOME MEASURES: GJB2 genotype and audiometric phenotype. RESULTS: The prevalence of subjects with HI having biallelic GJB2-related mutations was 15.3% (24/157). Of these 24 patients, 9 (38%) were homozygous 35delG, 6 (25%) had other biallelic nonsense mutations, and 9 (38%) had a missense mutation of at least 1 allele. The allelic prevalence of 35delG was 8.6% (27/314) in the study population and 48% (23/48) in the DFNB1 group. The M34T allele mutation was next most prevalent at 2.2% (7/314) in the study population and 10% (5/48) in the DFNB1 group. Severe to profound HI occurred in 59% of DFNB1 subjects. Genotypes with biallelic nonsense mutations had a high risk of severe to profound HI (88%). DFNB1-related HI was usually bilateral, symmetric, nonprogressive, and had flat audiograms. However, asymmetric HI (22%), sloping audiograms (26%), and even borderline-normal hearing in 1 ear was observed, and these were associated with the presence of at least 1 missense mutation. Two novel mutations, K15T and L90V, were identified. A subject presenting to our clinic with severe to profound HI had a 40% risk of biallelic GJB2 mutation. CONCLUSIONS: Our population represents a consecutively enrolled clinic population with sensorineural hearing loss. In our DFNB1-related HI cohort, the 35delG mutation and severe to profound HI rates were lower than previously reported. Our missense mutation and M34T allelic prevalence rates were higher than expected and were associated with a less severe hearing loss. The presence of biallelic nonsense mutations was associated with severe to profound hearing loss in nearly 90% of cases. Mild asymmetric HI and sloping audiograms were more often associated with missense mutations.

Adolescent↗
PubMed2003

Temporal bone abnormalities associated with hearing loss in Waardenburg syndrome.

OBJECTIVES/HYPOTHESIS: The objectives were to correlate audiometric thresholds with radiological findings and to determine the prevalence of inner ear radiological abnormalities in patients with hearing loss and Waardenburg syndrome. STUDY DESIGN: The study was a retrospective review of patients with Waardenburg syndrome identified in a pediatric hearing-impaired population and human genetics clinic. METHODS: Nine children with Waardenburg syndrome were identified. Eighty-nine children without sensorineural hearing loss served as control subjects. Clinical data, audiometric thresholds, and radiographic temporal bone measurements in these children were analyzed. RESULTS: Seven children were identified with hearing loss and Waardenburg syndrome. Four children had Waardenburg syndrome type 1, and three children had Waardenburg syndrome type 2. The overall prevalence of hearing loss in the total study population with Waardenburg syndrome was 78%. The mean pure-tone average was 99 dB. All of the children had sensorineural hearing loss. The hearing outcome was stable in 86% of the children. Twelve temporal bones were available for radiological analysis by computed tomography. Enlargement of the vestibular aqueduct was found in 50% of the CT scans. There was a significant difference in measurements of vestibular aqueduct width at the midpoint between the patients with Waardenburg syndrome and the control group (P <.05). There were also significant differences in the measurements of the vestibule (P =.0484), internal auditory canal (P =.0092), and modiolus (P =.0045) between the children with Waardenburg syndrome and the control group. CONCLUSION: A profound sensorineural hearing loss was characteristic of the study population with Waardenburg syndrome. Overall, 100% of patients with hearing loss and Waardenburg syndrome had temporal bone anomalies on at least one measurement of their inner ear, and 50% had an enlargement of the vestibular aqueduct at the midpoint. As shown by computed tomography, enlargement of the vestibular aqueduct and the upper vestibule, narrowing of the internal auditory canal porus, and hypoplasia of the modiolus are features of Waardenburg syndrome.

Audiometry, Pure-Tone↗
PubMed2002

Clinical and audiological features in auditory neuropathy.

OBJECTIVE: To medically and audiologically characterize a population of children diagnosed as having auditory neuropathy (AN). STUDY DESIGN: Retrospective medical chart review. SETTING/SUBJECTS: We identified 22 patients from a pediatric otology clinic in a tertiary care pediatric hospital setting. RESULTS: A genetic factor in AN is suggested by our identification of 3 families with 2 affected children and 2 other children with family histories that were positive for hearing loss. Clinical features common among our population included a history of hyperbilirubinemia (n = 11 [50%]), prematurity (n = 10 [45%]), ototoxic drug exposure (n = 9 [41%]), family history of hearing loss (n = 8 [36%]), neonatal ventilator dependence (n = 8 [36%]), and cerebral palsy (n = 2 [9%]). Full clinical and audiological data were available for 18 of the 22 children, including otoacoustic emissions, auditory brainstem responses with cochlear microphonics, and age-appropriate audiometric findings. Significantly, 9 of these 18 patients showed improvement in behavioral thresholds over time, indicating that a subset of children with AN may recover useful hearing levels. Also significant was the success of cochlear implantation in 4 children. CONCLUSIONS: Management of AN in children requires serial clinical and audiometric evaluations, with a prominent role for behavioral testing. Prematurity, genetics, and hyperbilirubinemia appear to be significant factors in the development of AN; hyperbilirubinemia can be associated with spontaneous improvement of hearing thresholds. For those children not benefiting from amplification or FM systems, cochlear implantation remains a potentially successful method of habilitation.

Audiometry↗
PubMed2002

Hearing preservation surgery for small endolymphatic sac tumors in patients with von Hippel-Lindau syndrome.

OBJECTIVE: To determine the incidence of bilateral endolymphatic sac tumors in von Hippel-Lindau syndrome and to describe the technique and results of hearing preservation surgery for small endolymphatic sac tumors in a series of patients with von Hippel-Lindau syndrome. STUDY DESIGN: Analysis of the literature to determine the incidence of bilateral endolymphatic sac tumors and a retrospective case review of hearing preservation surgery for removal of small endolymphatic sac tumors in four patients with von Hippel-Lindau syndrome. SETTING: Tertiary care academic medical centers. PATIENTS: Four patients with von Hippel-Lindau syndrome (three with bilateral endolymphatic sac tumors) and progressive sensorineural hearing loss in which preoperative imaging studies revealed in situ or small endolymphatic sac tumors without ipsilateral labyrinthine destruction. INTERVENTION: All four patients had complete surgical excisions of the endolymphatic sac tumor via one of three surgical approaches with the goal of hearing preservation. One patient had bilateral surgery. MAIN OUTCOME MEASURES: Audiometric and radiographic. RESULTS: Nearly one-third (30.2%) of patients with von Hippel-Lindau syndrome and endolymphatic sac tumors have bilateral disease. All four patients (five ears) maintained serviceable hearing postoperatively after surgical excision of the endolymphatic sac tumor via a variety of approach options. CONCLUSION: The discovery of a small or in situ endolymphatic sac tumor affords the patient the option of surgical removal with hearing preservation. This is critical in the patient with von Hippel-Lindau syndrome who is at risk for bilateral disease and complete bilateral anacusis if tumor growth progresses.

Adult↗
PubMed2002

Meningioma involving Meckel's cave: transpetrosal surgical anatomy and clinical considerations.

Meningiomas originating in Meckel's cave (MC) are uncommon lesions that represent 1% of all intracranial meningiomas. Innovations in skull base surgery have enabled resection of these lesions with less morbidity, but require an intimate knowledge of both lesional pathology and regional microneuroanatomy. To review the surgical and clinical considerations involved in the management of MC meningiomas, we retrospectively reviewed data from patients who underwent transpetrosal resection of primary MC meningiomas between 1984 and 1998. Of 146 patients who underwent transpetrosal removal of meningiomas, 7 were believed to have tumors originating in MC. All 7 patients presented with trigeminal dysfunction, facial pain, and/or headache. Complete tumor removal was achieved in 5 of the 7 patients. Facial hypoesthesia or anesthesia, paralysis of cranial nerve VI, and ophthalmoplegia were among the postoperative complications encountered. Meningiomas of MC represent treatable lesions whose diagnosis requires prompt imaging of patients with trigeminal dysfunction and symptoms of facial pain and headache.

Adult↗