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Biomedical subjects

R T Ramsden

Publications and source records attributed to R T Ramsden.

At least 19 recordsLinked to original sources
PubMed1999

Management of neurofibromatosis type 2.

Neurofibromatosis type 2 (NF2), an as-yet incurable disease that predisposes patients to multiple intracranial and spinal tumors, requires a team approach to treatment, because of its multisystem nature. Included on the team should be neuro-otologists, neurosurgeons, ophthalmologists, geneticists, audiologists, speech therapists and other rehabilitative personnel, including counselors, psychologists and, occasionally, psychiatrists. The challenge is to arrive at a treatment strategy that preserves useful hearing and quality of life without increasing the risk of complications to the facial nerve or compromising neurologic status. Choosing the best treatment approach involves considering a complex set of competing factors that affect various aspects of the patient's outcome.

Facial Paralysis↗
PubMed1999

Central electrical stimulation of the auditory pathway in neurofibromatosis type 2.

The auditory brainstem implant (ABI) is a viable treatment option for patients with neurofibromatosis type 2 (NF2) whom either vestibular schwannomas or the surgery used to remove them has rendered totally deaf. This device stimulates the central auditory pathways in a manner similar to the cochlear implant in individuals with a total hearing loss. A multichannel model with transcutaneous signal transmission is in use experimentally in both the United States and Europe. Of 14 patients implanted with the ABI in a European pilot study, 13 received auditory sensations at initial tuning. Surgical implantation of the ABI is generally, but not always, performed at the same time as tumor removal, with the preferred route being the transmastoid-translabyrinthine approach. After insertion, monitoring of the device is required to optimize the location of its electrode on the cochlear nucleus complex.

Electric Stimulation↗
PubMed1998

Hearing preservation despite labyrinthectomy for resection of giant cholesteatoma with middle fossa extension.

A case is described of an extensive acquired cholesteatoma of the middle ear cleft which had invaded the middle cranial fossa and produced a mass effect on the temporal lobe. It had also extended into the labyrinth without causing elevation in the bone conduction threshold. Furthermore, even after total bony labyrinthectomy, there was very little elevation in these thresholds. The literature relating to hearing preservation after labyrinthectomy is reviewed.

Adult↗
PubMed1998

Intracochlear factors contributing to psychophysical percepts following cochlear implantation.

The performance of cochlear implant patients may be related to intracochlear, histopathological factors. We have performed detailed post-mortem examinations of five human, implanted cochleas and for each electrode correlated the psychophysical threshold, comfortable level and dynamic range with spiral ganglion cell survival, presence of fibrous tissue and/or new bone, and distance between the centers of the electrode bands and Rosenthal's canal. The psychophysical parameters were strongly interrelated. Threshold and comfort levels correlated with the distance between the electrodes and Rosenthal's canal. Threshold levels also correlated with the presence of intracochlear fibrous tissue and new bone, especially with the former. The dynamic range showed a negative correlation with intracochlear pathology, especially with new bone. Comfort levels and dynamic range were related to spiral ganglion cell survival. The distance between the electrodes and the modiolus increased with increasing levels of fibrous tissue and new bone. Spiral ganglion cell survival was decreased with increasing levels of fibrous tissue and new bone.

Adult↗
PubMed1998

Somatic mosaicism: a common cause of classic disease in tumor-prone syndromes? Lessons from type 2 neurofibromatosis.

Blood samples from 125 families with classic type 2 neurofibromatosis with bilateral vestibular schwannomas were analyzed for mutations in the NF2 gene. Causative mutations were identified in 52 families. In five families, the first affected individual in the family (the index case) was a mosaic for a disease-causing mutation. Only one of nine children from the three mosaic cases with children are affected. Four of these nine children inherited the allele associated with the disease-causing mutation yet did not inherit the mutation. NF2 mutations were identified in only 27/79 (34%) of sporadic cases, compared with 25/46 (54%) of familial cases (P<.05). In 48 families in which a mutation has not been identified, the index cases have had 125 children, of whom only 29 are affected with NF2 and of whom only a further 21 cases would be predicted to be affected by use of life curves. The 50/125 (40%) of cases is significantly less than the 50% expected eventually to develop NF2 (P<.05). Somatic mosaicism is likely to be a common cause of classic NF2 and may well account for a low detection rate for mutations in sporadic cases. Degrees of gonosomal mosaicism mean that recurrence risks may well be <50% in the index case when a mutation is not identified in lymphocyte DNA.

Adult↗
PubMed1998

Vestibular stimulation by multichannel cochlear implants.

The recipient of a Nucleus 22 multichannel cochlear implant began to experience severe vestibular stimulation related to the implant. This patient's experience initiated a study with the objective of determining the frequency of implant-related vestibulo-ocular stimulation. Subjects consisted of 17 randomly selected patients who use cochlear implants. Included in the study were 14 Nucleus 22 and three Med-El Combi 40-devices. Stimulation of the implants was performed both by individual channel and with sound field broad-band 80-dB noise using the users' normal device settings. Eye movements were monitored with infrared videonystagmography. Only one subject, who used a Med-El Combi 40, showed a consistent and strong ocular response to cochlear stimulation but had no subjective symptoms. The authors conclude that vestibulo-ocular activation is possible with multichannel cochlear implants but is infrequent and may not be clinically significant.

Cochlear Implants↗
PubMed1998

Vestibular disease unmasked by hyperventilation.

Hyperventilation-induced dizziness is often thought to be psychogenic, but its effects in the presence of known vestibular disease have not been adequately examined. In this study hyperventilation was tested in two models of vestibular disease. These were, first, patients with profound unilateral vestibular deficit (prior translabyrinthine acoustic neuroma resection [postsurgery group]) and, second, patients with variable unilateral vestibular deficit (unoperated unilateral acoustic neuroma [presurgery group]). Patients were hyperventilated for 90 seconds. Using infrared videonystagmography, 100% of the 32 postsurgery patients and 82% of the 28 presurgery patients developed nystagmus with hyperventilation. Hyperventilation was more sensitive than head shake for eliciting nystagmus in these models. The false-positive rate for nystagmus in 29 normal volunteers was 3.5% for hyperventilation and 10% for head shake. Our results show that hyperventilation can unmask underlying vestibular disease.

Dizziness↗
PubMed1998

Differential diagnosis of type 2 neurofibromatosis: molecular discrimination of NF2 and sporadic vestibular schwannomas.

Patients who present with unilateral vestibular schwannomas either at a young age or with additional features of type 2 neurofibromatosis (NF2) are at risk of developing bilateral disease and transmitting a risk of neurogenic tumours to their offspring. We have identified 15 patients from a series of 537 with unilateral vestibular schwannomas who also had one or more of the following: other tumours (10/15), features of NF2 (3/15), or a family history of neurogenic tumours (5/15). No germline NF2 mutations were detected and in 7/9 cases where tumour material was available for analysis a germline mutation in the NF2 gene has been excluded. Although a possibility of gonosomal mosaicism still exists, exclusion tests for the offspring are now possible. We suggest a general strategy, based on analysis of tumour DNA, for distinguishing sporadic and familial cases of tumours caused by two hit mechanisms. Application of this strategy suggests that most instances of unilateral vestibular schwannoma which do not fulfil criteria for NF2 represent chance occurrences.

Adult↗
PubMed1998

Orthodromic near-field potentials of the intratemporal facial nerve.

HYPOTHESIS: This study aimed to assess the electrophysiologic parameters of near-field action potentials recorded from the intratemporal facial nerve. BACKGROUND: Assessment of facial nerve function is limited because of the inaccessibility of the majority of its course deep in the temporal bone. Indirect measurements have therefore evolved in which stimulation distal to most major pathology and indirect recordings from the tissues the nerve supplies offers some evidence as to facial function. Recording from the intratemporal portion of the facial nerve is possible. Antidromic nerve action potentials can be recorded from an extratympanic electrode after stimulation of peripheral facial nerve branches. This technique offers new alternatives to the assessment of the facial nerve. METHODS: The facial nerve was electrically stimulated close to the brain stem, and monopolar recordings were taken distally at several points along its intratemporal course. Averaging techniques produced a reliable and reproducible triphasic waveform that then was analyzed. RESULTS: Neuromuscular blockade had no effect on amplitude of the waveform. Recording at different points along the nerve course showed an increasing nerve potential latency with increasing distance from the stimulus. The amplitude of the waveform decreased as the recording electrode was moved away from the nerve. These findings are in keeping with the electrophysiologic properties of a near-field nerve action potential. Conduction velocity along the facial nerve averaged 23.7 m/s and was found to vary along different nerve segments. CONCLUSION: Facial nerve action potentials can be recorded from within the temporal bone despite its multidirectional course through different volume conductors. These action potentials exhibit the same characteristics as those arising from more accessible peripheral nerves.

Adult↗
PubMed1998

Cochlear ossification after meningitis.

OBJECTIVE: This study aimed to assess the pathologic processes that result in ossification of the cochlear lumen after bacterial meningitis. STUDY DESIGN: The study design was a retrospective case review. SETTING: The study was conducted at a tertiary referral center. PATIENTS: Profoundly deaf postmeningitic patients who underwent cochlear implantation were studied. INTERVENTIONS: Diagnostic and therapeutic observations were performed. MAIN OUTCOME MEASURES: The extent of cochlear ossification is classified and related to age at which infection occurred, cerebrospinal fluid leukocyte count, Gram's stain, organism, and delay between meningitis and implantation. The extent of ossification noted on high-definition computed tomographic (CT) scan is compared with surgical findings and related to the time delays between meningitis, imaging, and surgery. RESULTS: Ossification fell into three groups: gross ossification of the scala tympani and variable amounts of the scala vestibuli; partial ossification localized to the basal turn of the scala tympani; and no ossification. There was no correlation between the extent of ossification and the age when infected, type of pathogen, cerebrospinal fluid leukocyte count, and time delay between meningitis and implantation. Visualization of bacteria on Gram's stain was a highly sensitive measure of ossification (0.93) but was not specific (0.6) with positive and negative predictive values of 0.76 and 0.86, respectively. High-definition CT underestimated the extent of ossification in 50% of cases when performed within 6 months of meningitis. CONCLUSIONS: Ossification is either gross or localized to the basal turn of the scala tympani. If ossification does occur, it is rapid and complete within a few months of infection. The visualization of bacteria on Gram's stain is a sensitive indicator for the presence of ossification but has low specificity. High-definition CT, if performed within the first 6 months of meningitis, can be an inaccurate diagnostic tool and therefore should be performed as close to the date of surgery as possible.

Adolescent↗
PubMed1998

Cochlear implantation in the deaf-blind.

OBJECTIVE: This study aimed to examine the outcome and rehabilitation of cochlear implantation in a select group of individuals: the deaf-blind. STUDY DESIGN: The study design was a retrospective and prospective case evaluation of the deaf-blind implantees. SETTING: The study was conducted at a national adult and pediatric cochlear implant center. PATIENTS: A total of eight adult and two pediatric blind or visually impaired individuals undergoing cochlear implantation for severe or profound deafness participated. Evaluation of the history, etiology of blindness and deafness, and outcome of the cochlear implantation was examined. INTERVENTIONS: Cochlear implantation and subsequent rehabilitation were performed. MAIN OUTCOME MEASURE: Bamford-Kowal-Bench (BKB) sentence scores were measured. RESULTS: Individually and as a group, these patients respond exceptionally well to cochlear implantation. The BKB scores are above the average for the sighted cochlear implantees. This raises the question of heterosensory substitution. CONCLUSIONS: Cochlear implantation has a major role to play in the rehabilitation of certain deaf-blind individuals, and these patients may be among the most worthwhile to consider for implantation. The implant team must acquire additional rehabilitative skills, and the strength of the deaf-blind culture must be taken into consideration.

Adolescent↗
PubMed1997

Cochlear implantation in the presence of chronic suppurative otitis media.

Nine patients are presented who underwent cochlear implantation in the presence of chronic suppurative otitis media. Four had a simple tympanic membrane perforation, four had a pre-existing mastoid cavity and one had cholesteatoma in the ear chosen for implantation. Patients with a simple perforation had a staged procedure with myringoplasty followed by cochlear implantation after an interval of three months. Patients with cholesteatoma or with an unstable mastoid cavity were also staged. A mastoidectomy or revision mastoidectomy was performed with obliteration of the middle ear and mastoid using a superiorly pedicled temporalis muscle flap and blind sac closure of the external meatal skin. After a further six months a second stage procedure was performed to confirm that the middle-ear cleft was healthy and to insert the implant. Patients presenting with a stable mastoid cavity underwent obliteration of the cavity and implantation of the electrode as a one-staged procedure. To date there have been no serious problems such as graft breakdown, recurrence of disease or implant extrusion, and all patients are performing well.

Child, Preschool↗
PubMed1997

Primary tumours of the vestibule and inner ear.

Seven primary tumours of the vestibule and inner ear are described, six schwannomas and one traumatic fibroma. Schwannomas in this situation may occur as sporadic tumours, or may be a feature of neurofibromatosis type 2 (NF-2). In the latter condition they may occur in isolation or in association with, but separate from, schwannomas arising in the internal meatus. Direct extension into the vestibule of an intrameatal vestibular schwannoma is well reported, but extension of an intravestibular tumour into the internal meatus is not described. Traumatic fibromas of the vestibule are rare and the trigger could be an attack of labyrinthitis. Intravestibular tumours, although rare, are likely to be diagnosed with increasing frequency with the widespread use of MR imaging.

Adult↗
PubMed1996

Deafness and cholesteatoma complicating fracture of the mandibular condyle.

A case of posterior fracture-dislocation of the mandibular condyle which resulted in conductive deafness and cholesteatoma is presented. Initial management by condylectomy improved auditory canal patency but failed to prevent the development of cholesteatoma, necessitating mastoid surgery. Although major complications following fractures of the condyle are not common the need to consider the possibility of damage to the ear in such fractures is emphasised.

Adult↗
PubMed1996

Explantation of a nucleus multichannel cochlear implant and re-implantation into the contralateral ear. A case report of a new strategy.

We present a unique case in which a multichannel cochlear implant device was explanted and the same device was re-implanted into the contralateral ear. A patient with bilateral total deafness secondary to head injury received an implant in his left ear but developed severe facial nerve stimulation. Because this stimulation could not be eliminated effectively with change of programming, it was decided to implant the contralateral ear. Since the device itself was functioning well, it was explanted from the left ear and re-implanted successfully into the right ear. Facial nerve stimulation was minimal in this ear and the patient demonstrated very good speech discrimination. To our knowledge, this is the first description of this strategy.

Aged↗
PubMed1996

Rehabilitation of the paralysed face: results of facial nerve surgery.

The case notes of 34 patients undergoing rehabilitative facial nerve surgery between 1978 and 1994 were retrospectively examined. Thirteen patients underwent facio-hypoglossal transposition with six achieving a facial nerve grade of IV (House-Brackmann scale) at 24 months post-surgery. Twelve patients underwent cable grafting of the facial nerve defect. Of these, 10 achieved a grade III result at 24 months. Nine patients underwent end to end anastomosis of the facial nerve, seven achieving a grade III result at 24 months after the repair. Re-routing of the facial nerve and the use of tissue glue to effect the anastomosis did not have an adverse effect on the outcome. Comparison of rerouted end to end anastomosis with non-re-routed cable grafting showed no difference. Patients presenting pre-operatively with facial weakness and those in whom nerve repair surgery was delayed for more than six months were less likely to have a good result.

Adult↗
PubMed1996

An audit of the cochlear implant service in Manchester.

The adult cochlear implant programme in Manchester was established in 1988 and the evaluation of the cochlear implant service involved the first 58 implants users (mean age = 51.65 years, range 19-75 years). Questionnaires were sent to implant users and their partners to evaluate the service with regard to provision of information, clinical care during in-patient assessments, waiting times, operation for cochlear implant and post-operative rehabilitation. The results show that the majority of patients (78 per cent) felt that the implant gave them as much or more benefit than expected. Areas identified for improvements include provision of more written information about cochlear implants; reduction in waiting times for first appointments; more information about the surgical risks and more instruction about home auditory training exercises for family and friends. As a consequence of the audit results the clinical practice and service provision for cochlear implantation in Manchester has been modified.

Adult↗