OBJECTIVE: Hearing loss after aminoglycoside administration has been thought to result primarily from hair cell injury. The purpose of the study was to determine the potential for direct injury of spiral ganglion cells and hair cells in cases of documented human aminoglycoside ototoxicity. STUDY DESIGN: Retrospective case review. METHODS: The clinical course of two individuals with aminoglycoside ototoxicity are documented, including the details of administration of tobramycin and other ototoxic medication and serial audiograms. The temporal bones were processed, and the cochlear elements quantified. RESULTS: Histopathological study of the temporal bones from the individuals in the study demonstrated reduction of both ganglion cell and hair cell populations. Spiral ganglion cell loss was not necessarily subadjacent to areas of hair cell loss in cases of aminoglycoside ototoxicity. Instead, spiral ganglion cell reduction may be present in segments of the cochlea with normal-appearing hair cells. CONCLUSIONS: The study suggests that aminoglycoside antibiotics can injure spiral ganglion cells directly, as well as hair cells. Thus, the characteristic hearing loss of ototoxicity can result from degeneration of either cochlear element.

Adult↗

PubMed2001

Antonio Scarpa and the discovery of the membranous inner ear.

OBJECTIVE: To give a historical perspective of Antonio Scarpa's contributions to otology, specifically the discovery of the inner ear organs as the foundation for the experimental work that followed. BACKGROUND/METHOD: Scarpa's original descriptions of the human inner ear were translated from the Latin text, and his illustrations were analyzed and compared with current knowledge. CONCLUSIONS: Antonio Scarpa's anatomic and clinical studies place him among the great scientists of the eighteenth century. His discoveries about the inner ear established the limit of what could be learned without advanced histologic techniques and provided the foundation for the work that eventually led to the modern understanding of ear physiology.

Anatomy↗

PubMed2001

Aplasia of the cochlear nerve: a temporal bone study.

OBJECTIVE: The purpose of this study was to evaluate the temporal bone findings in individuals with cochlear nerve aplasia. STUDY DESIGN: Retrospective case review. METHODS: Two individuals with unilateral profound deafness caused by aplasia of the cochlear nerve were identified. The temporal bones were processed, and the cochlear elements were quantified. RESULTS: Histopathologic study of the temporal bones from these individuals demonstrate that a fully formed cochlea and normal-appearing organ of Corti can occur in the absence of the spiral ganglion and cochlear nerve. Cochlear nerve aplasia can occur in both a narrow or a normal-sized internal auditory canal. CONCLUSION: These findings suggest that the development of the cochlea and organ of Corti are not dependent on the presence of the cochlear nerve and spiral ganglion. The entity of cochlear nerve aplasia in the presence of a normally formed cochlea must be considered when evaluating individuals as candidates for cochlear implantation.

Adult↗

PubMed2000

Temporal bone histopathology in connexin 26-related hearing loss.

OBJECTIVE: Mutations in GJB2, a gene that encodes a gap junction protein, Connexin 26 (Cx26), are responsible for approximately one third of sporadic severe-to-profound or profound congenital deafness and half of severe-to-profound or profound autosomal recessive nonsyndromic hearing loss (ARNSHL). Mouse mutants homozygous for knockouts of this gene are nonviable, precluding histopathologic studies of the associated inner ear pathology in this animal model. Therefore, we studied archival temporal bone sections to identify temporal bone donors with Cx26-related deafness. STUDY DESIGN: Temporal bone donors with a history of congenital severe-to-profound or profound deafness were identified in the registry of the Temporal Bone Library at the University of Iowa. Histological findings were interpreted in a blinded fashion. DNA extracted from two celloidin-embedded mid-modiolar sections from each temporal bone was screened for the 35delG Cx26 mutation. The entire coding region of Cx26 was screened for other deafness-causing mutations if the 35delG mutation was detected. RESULTS: Of five temporal bone donors with congenital severe-to-profound deafness, one donor was found to have Cx26-related deafness. This individual was a Cx26 compound heterozygote, carrying the 35delG mutation and a noncomplementary Cx26 missense mutation on the opposing allele. Microscopic evaluation of this temporal bone showed no neural degeneration, a good population of spiral ganglion cells, near-total degeneration of hair cells in the organ of Corti, a detached and rolled-up tectorial membrane, agenesis of the stria vascularis, and a large cyst in the scala media in the region of the stria vascularis. CONCLUSION: This study is the first to report the temporal bone histopathology associated with Cx26-related deafness. Preservation of neurons in the spiral ganglion suggests that long-term successful habilitation with cochlear implants may be possible in persons with severe-to-profound or profound Cx26-related deafness.

Adult↗

PubMed1998

The systemic vasodilatory action of protamine: is it inhibited or mediated by heparin?

UNLABELLED: The administration of protamine to neutralize the circulating heparin is common practice in cardiovascular surgery. The use of this drug is sometimes associated with hemodynamic alterations of varying degree and intensity (systemic hypotension, pulmonary hypertension and even cardiogenic shock). An intrinsic action of protamine has been suggested to be the cause of these vascular reactions. This action is blocked when protamine forms a complex with heparin, although in other cases it appears that the heparin-protamine complex is the factor responsible for these hemodynamic alterations. The aim of this experimental study was to characterize the vasodilatory action of protamine on the systemic circulation, determining whether or not it is dose-dependent; to analyze the role of endothelium; and to evaluate whether this vasodilatory effect is modified by the presence of heparin. MATERIALS AND METHODS: The abdominal aorta was dissected from eight New Zealand rabbits and then sectioned into vascular rings for study in an organ chamber. Mechanical disruption of endothelium was performed on some rings (n = 14). Once submaximal contraction was reached (ClK 80 mM), protamine sulfate with a final concentration in the organ chamber of 80-400 micrograms/ml was added to one of the groups (n = 12). In the second group (n = 12), equal concentrations of protamine were tested in the presence of heparin at a final concentration of 100 U/ml. RESULTS: The mean vasodilatation reached in the group of rings exposed only to protamine was 95.4 +/- 1.5% with respect to the submaximal contraction induced with ClK. In the second study group, the rings were exposed to protamine at equally increasing concentrations (80-400 micrograms/ml) but with the presence of heparin in the organ chamber. The mean vasodilatation in this group was 90 +/- 1.5. No statistically significant differences in vasodilatation were found between this group and the protamine without heparin group. On the other hand, in the endothelium-denuded rings (n = 14) exposed to isolated protamine and to protamine-heparin, no vasodilatory response was observed. CONCLUSION: Our results show that the administration in vitro of protamine induces endothelium-dependent vasodilatation of the systemic circulation. Likewise, this relaxing effect mediated through endothelium is not blocked when protamine forms a complex with heparin in comparable concentrations of both drugs. Based on these preliminary findings, we believe that in high-risk patients the prevention of systemic vasodilatation and cardiovascular collapse produced by protamine should move towards the use of other substances that can neutralize the anticoagulant effect of heparin or towards pre-medication guidelines that prevent these secondary effects in the case of protamine administration.

Acetylcholine↗

PubMed1997

Particulate matter in the posterior semicircular canal.

The pathoetiology of benign paroxysmal positional vertigo (BPPV) is controversial. Particulate matter within the posterior semicircular canal has been identified intraoperatively in patients with BPPV but has also been reported in non-BPPV patients at the time of translabyrinthine surgery (Parnes LS, McClure JA. Free-floating endolymphatic particles: a new operative finding during posterior semicircular canal occlusion. Laryngoscope 1992;102:988-92; Schuknecht HF, Ruby RRF. Cupulolithiasis. Adv Otorhinolaryngol 1973;20: 434-43; Kveton JF, Kashgarian M. Particulate matter within the membranous labyrinth: pathologic or normal? Am J Otol 1994;15:173-6). The nature of the particulate matter remains unknown. The purpose of this study was to prospectively examine the posterior semicircular canal of patients with and without a clinical history of BPPV for the presence of particulate matter. Seventy-three patients without BPPV symptoms undergoing labyrinthine surgery (vestibular schwannoma excision or labyrinthectomy) and 26 patients with BPPV undergoing the posterior semicircular canal occlusion procedure were compared. Additionally, 70 archived temporal bones without a history of BPPV were examined microscopically for the presence of particulate matter within the lumen of the membranous labyrinth. No particles were observed intraoperatively in any of the 73 patients without a history of BPPV. Particulate matter was observed in 8 of 26 patients at the time of the posterior semicircular canal occlusion procedure for intractable BPPV. Of the 70 temporal bones examined, 31 did not show significant postmortem changes and also did not demonstrate cupulolithiasis or canalithiasis. Particulate matter from within the membranous posterior semicircular canal was removed from one patient at the time of posterior semicircular canal occlusion for intractable BPPV symptoms and was examined by scanning electron microscopy. The particulate matter appeared morphologically consistent with degenerating otoconia. These data show a statistically significant association between the presence of particles within the posterior semicircular canal in this study and the symptom complex of BPPV.

Ear, Inner↗

PubMed1997

Measurement of body temperature in pediatric patients.

Explore the source record for details and available documents.

Body Temperature↗

PubMed1997

Mitochondrial DNA deletions associated with aging and possibly presbycusis: a human archival temporal bone study.

HYPOTHESIS: We attempted to determine if the common mitochondrial DNA aging deletion is also associated with presbycusis. BACKGROUND: Presbycusis is the most common cause of deafness in adults in the United States, affecting approximately 40% of the population older than 75 years of age. The ability to identify a gene(s) or a specific genetic deficit(s) associated with presbycusis has significant clinical importance. METHODS: The current study examined mitochondrial DNA (mtDNA) from cochlear sections of 34 human temporal bones: 17 with normal hearing and 17 with presbycusis. DNA was extracted from celloidin-embedded temporal bone sections; and specific oligonucleotide primers were designed to amplify the cytochrome b gene and a 4,977 base pair (bp) deletion of the mtDNA. Polymerase chain reaction (PCR) was used to amplify the base pair products that correspond to targeted gene regions, and sequencing was used to verify the products. RESULTS: Fourteen of the 17 patients with hearing loss showed the 4,977 bp deletion and this deletion was present in only eight of the 17 human specimens with normal audiograms. The cytochrome b gene was amplified from all specimens. CONCLUSIONS: The current study demonstrates the presence of a 4,977 bp deletion in human mitochondrial DNA genome that is associated with aging and with some forms of presbycusis. These results, coupled with previous animal studies, suggest that this 4,977 deletion may be associated with presbycusis.

Adult↗

PubMed1996

Otocephalus: histopathology and three-dimensional reconstruction.

Otocephaly is a lethal malformation of the first and second branchial arches, which consists of ventromedial displacement of the external ear structures (synotia), mandibular aplasia (agnathia), absence of the tongue (aglossia), and microstomia. We present the first complete description of the temporal bone findings in a case of otocephalus. A three-dimensional computer-assisted reconstruction of the right temporal bone was performed, allowing a unique graphic analysis. An extremely low-lying middle fossa tegmen was noted with malrotation of the middle ear structures. Severe ossicular malformations were also found. An anomalous course of the internal carotid artery was noted with indentation of the basal turn of the cochlea. All three layers of the otic capsule were incompletely developed. Cochlear bony dehiscences were noted. These findings are consistent with early arrest of fetal development and malrotation caused by lack of growth pressure from the mandibular arch. Implications of these findings in the embryologic development of the ear are discussed.

Abnormalities, Multiple↗

PubMed1996

Association of mitochondrial DNA deletions and cochlear pathology: a molecular biologic tool.

The purpose of these experiments was to develop a method of isolation, amplification, and identification of cochlear mitochondrial DNA (mtDNA) from minute quantities of tissue. Additionally, studies were designed to detect mtDNA deletions (mtDNA del) from the cochlea that previously have been amplified from other organ systems and tissues. MtDNA del have been associated with many pathologies, including neurological disorders, sensorineural hearing loss, ischemia, cardiomyopathies, and aging. DNA was extracted from rat and human tissues, and polymerase chain reaction was used to amplify mtDNA sequences. A 360 base pair (bp) cytochrome-b gene product and the highly conserved ND1-16S ribosomal ribonucleic acid regions found only in mtDNA were amplified from all tissues. Preliminary studies have identified a 4834 bp mtDNA del in aged rats and a corresponding 4977 bp mtDNA del in aged humans. Additionally, preliminary results in human archival temporal bone studies reveal the presence of the 4977-bp mtDNA deletion in two out of three patients with presbycusis. The deletion was not evident in age-matched control patients without a history of presbycusis. This technique of mtDNA identification makes it possible to investigate specific mtDNA defects from a single cochlea, promoting the study of hereditary hearing loss and presbycusis at a molecular biologic level.

Aged↗

PubMed1996

Update on idiopathic perilymphatic fistulas.

Idiopathic perilymphatic fistula has been confirmed with clinical-temporal bone histopathologic studies as a separate inner ear disease. Criteria for its diagnosis are sudden or progressive sensory hearing loss, or for vestibular components, a positive fistula test, constant disequilibrium, and positional nystagmus or postural vertigo. Nonsurgical treatment, such as keeping the head higher than the heart and avoiding heavy lifting, can be tried. When it is ineffective or when there is sudden hearing loss without improvement, surgical sealing of the leak should be attempted.

Adult↗

PubMed1995

Idiopathic perilymphatic fistulas. A temporal bone histopathologic study with clinical, surgical, and histopathologic correlations.

OBJECTIVE: To report a case of idiopathic perilymphatic fistulas diagnosed and successfully treated during life and confirmed histopathologically post mortem. METHODS: Perilymphatic fistulas were diagnosed clinically and repaired surgically. Light microscopic histopathologic studies were made of both temporal bones after death. RESULTS: Vestibular symptoms had improved postoperatively. Postmortem histopathologic examination of the temporal bones demonstrated patencies of the labyrinth capsule that had been predicted clinically during life, the qualities of the membranous labyrinth in both the operated-on and the unoperated-on ears, and the elements of the surgical repair. Notably, there was no evidence of endolymphatic hydrops. CONCLUSIONS: The histopathologic findings document the relationships of the fistula ante fenestram and the fissure connecting the round window niche and the posterior semicircular canal to idiopathic perilymphatic fistulas. Also, the diagnostic features reported herein allowed this patient with fluctuating hearing loss, episodic vertigo, and tinnitus to be distinguished from a patient with Meniere's syndrome. These findings have implications regarding past and future studies of vestibular and cochlear disorders.

Aged↗