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Biomedical subjects

T E Mitchell

Publications and source records attributed to T E Mitchell.

14 recordsLinked to original sources

The preauricular sinus: A review of its aetiology, clinical presentation and management.

The preauricular sinus is a not uncommon finding in the paediatric population. Recent reports have added to our knowledge of this benign malformation. We review the current literature with respect to the aetiology of the condition, its clinical features, and associations with other congenital malformations. In those patients in whom a preauricular sinus is identified, we recommend associated congenital anomalies be sought. In selected cases, a renal ultrasound scan may be appropriate. Where no associated abnormalities are identified, and where the preauricular sinus is asymptomatic, there is consensus opinion that no further action is indicated. In the acute phase of infection, treatment comprises administration of appropriate antibiotics, and incision and drainage of an abscess if present. In the symptomatic preauricular sinus exhibiting recurrent or persistent infection, opinion regarding optimal management varies. Latest evidence suggests definitive surgical treatment offering the most favourable outcome is by wide local excision of the sinus, as opposed to the previously preferred technique of simple sinectomy. Magnification employed during surgery, and opening, and following from the inside as well as outside, branching tracts of the sinus may further minimise the risk of recurrence.

Abscess↗

An experimental investigation of the resolution of tympanometry for micro-perforations of the tympanic membrane.

Tympanometry is well established as a useful tool in the field of otological diagnosis. There have been sporadic reports, however, of bizarre tympanograms in the presence of small perforations of the tympanic membrane. A model of the outer and middle ears was fabricated which was able to produce normal and pathological tympanograms. This model was used to investigate tympanometry in the presence of microperforations. A hypothesis for the mechanism of generation of sawtooth tympanograms in the presence of micro-perforations is postulated.

Acoustic Impedance Tests↗

Performance after cochlear implantation: a comparison of children deafened by meningitis and congenitally deaf children.

The speech perception and speech production performance following cochlear implantation of congenitally deaf children and children deafened by meningitis were analysed. Three groups consisting of 70 congenitally deaf children, 22 children deafened by meningitis before two years of age and 14 children deafened by meningitis after two years of age were compared. The group deafened by meningitis after two years of age demonstrated significantly better speech perception than the other two groups. Their speech production appeared better but did not achieve statistical significance compared with the other two groups. There was no significant difference in either speech perception or speech production between the congenitally deaf group and the group deafened by meningitis before two years of age.

Child, Preschool↗

Abnormal positive potentials in round window electrocochleography.

OBJECTIVE: To describe an atypical waveform, termed an abnormal positive potential (APP), on round window electrocochleograms (RW ECochG) of children and to relate its occurrence to clinical history. STUDY DESIGN: APPs were identified prospectively, and a retrospective analysis was made of these patients' clinical histories, audiograms, and auditory outcomes (hearing aid, cochlear implant, or nonauditory communication) SETTING: Tertiary referral teaching hospital, day surgery and clinics. PATIENTS: All 431 children <110 months of age suspected of a severe to profound hearing loss who underwent RW ECochG from January 1993 to August 1997. INTERVENTION: Diagnostic RW ECochG for auditory threshold estimation. MAIN OUTCOME MEASURE: The presence on the RW ECochG of the APP: an early positive potential in the absence of a compound action potential (CAP). RESULTS: An APP was observed in 34 children. The APP was most marked in response to clicks and 8-kHz tones. The APP click threshold averaged 70 dB hearing loss. The brainstem evoked potential of these children showed an absence of waves, or a broad positive wave with no subsequent waves. Twenty-nine of 30 behavioral audiograms obtained were indicative of severe to profound hearing loss. Auditory outcomes were available from 26 children; 45% of them derived no help from a hearing aid, and 8 children received a cochlear implant. Clinical factors frequently associated with APP were prematurity in combination with kemicterus or hypoxia. CONCLUSIONS: APP thresholds were lower than neural thresholds or behavioral thresholds. Children with APP need close follow-up, because half of those studied needed nonauditory strategies to develop effective communication.

Audiometry, Evoked Response↗

Positioning of the receiver-stimulator for the CI-24M cochlear implant in infants.

A new cochlear implant (CI-24M) has recently been released by Cochlear Ltd. The shape and size of the receiver-stimulator differs from that of the CI-22M. Infants as young as one year of age are now receiving cochlear implants. We have examined the likely effect of skull growth following the implantation of a CI-24M cochlear implant in an infant of this age.

Child↗

Traumatic laryngocoele.

This is the first reported case of a laryngocoele developing after laryngeal trauma. A 26-year-old man sustained a shotgun injury to his larynx. A large number of shotgun pellets was removed from his left vestibular fold. He subsequently developed a left-sided laryngocoele, probably due to fibrosis around the neck of the saccule. The laryngocoele was removed by an external approach.

Adult↗

Hairy polyp of the tonsil.

Hairy polyps or dermoids of the oro- and naso-pharynx are benign lesions containing elements of both ectodermal and mesodermal origin. We report a case of a hairy polyp arising from the tonsil in a three-week-old infant. This presented as an intermittent swelling in the mouth, which was successfully removed under general anaesthesia. To our knowledge this is only the third case of a hairy polyp arising at this site to be reported. We discuss the terminology applied to these lesions and review the literature.

Dermoid Cyst↗

Eye protection during mastoid surgery.

A questionnaire was sent to all Full Members of the British Association of Otolaryngologists to ascertain whether and what type of eye protection surgeons and theatre nurses wear during mastoid surgery. Despite Department of Health recommendations only 58 per cent of surgeons and 19 per cent of theatre nurses routinely wear any form of eye protection.

Eye Protective Devices↗

Spontaneous rupture of a congenital diaphragmatic eventration.

A 51-year-old man presented as an emergency with acute intestinal obstruction following herniation of abdominal contents into the left hemithorax through a spontaneous rupture of his eventrated left hemidiaphragm. He underwent a left thoracotomy with reduction of the herniated abdominal contents, repair of the diaphragmatic rupture and plication of the diaphragm. He made an uneventful recovery and remains asymptomatic. This is the first reported case of spontaneous rupture of an eventration of the diaphragm.

Diaphragmatic Eventration↗

Preparation of cross-sectional specimens of ceramic thermal barrier coatings for transmission electron microscopy.

During the microstructural examination of ceramic thermal barrier coatings by transmission electron microscopy (TEM), initial efforts for the preparation of cross-sectional thin foils from interface regions by conventional means were mostly failures. Delamination of the Y2O3-stabilized ZrO2 ceramic coating from the nickel-base alloy substrate sometimes occurred during fine polishing at around 80 microns thickness but mostly occurred during dimpling. Because of this sensitivity, special techniques for mechanical handling were developed so that ion milling could give thin enough regions of the metal-ceramic interface. TEM showed convincingly that the highly fragile nature of the coatings is in fact due to the extensive porosity at the interface developed as a result of heat treatment.

Ceramics↗

Electron microscopy study of twin behavior in GdBa2Cu3Ox and YBa2Cu3Ox.

Twins are ubiquitous in the perovskite superconductors. They form during cooling from high temperatures through the tetragonal-to-orthorhombic phase transformation. Their behavior has been studied by transmission electron microscopy using a liquid-nitrogen-cooled specimen holder. It is observed that extra twins sometimes form in coarse-twinned regions to give a "refined" twin structure; this is thought to be induced by thermal stresses from the electron beam. Prolonged electron irradiation (with little beam heating) results in transformation to tetragonal with a loss of the twin structure; this is probably due to disordering of the oxygen sublattice by knock-on displacement. The same transformations can be induced by deliberate electron beam heating. In both cases the twinned orthorhombic structure can be restored by re-ordering of the oxygen ions, in the first case by removing the beam and in the second case by allowing the specimen to cool.

Barium↗