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R K Jackler

Publications and source records attributed to R K Jackler.

At least 19 recordsLinked to original sources
PubMed1992

Facial paralysis due to benign parotid tumors.

On rare occasions, facial paralysis associated with a parotid tumor need not denote malignancy. We present two cases in which, contrary to appropriate conventional wisdom, facial paralysis resulted from benign mixed tumors. Each patient presented over 8 years following primary surgical excision. In neither patient was a mass palpable, and facial paralysis was the sole sign of recurrent disease. Each patient had been followed up for several months with a presumptive diagnosis of Bell's palsy prior to discovery of recurrent tumor by radiologic imaging. In each case, at operation the tumor was found to infiltrate the temporal bone via the stylomastoid foramen. Facial paralysis presumably resulted from extrinsic compression of the facial nerve. These two cases add to the few previous reports of facial paralysis due to benign parotid gland tumors.

Adenoma, Pleomorphic↗
PubMed1992

An animal model of chronic tympanic membrane perforation.

Previous investigations into the healing and reconstruction of tympanic membrane (TM) perforations have involved animal models with acute TM perforations. A problem with the acute TM perforation model is that most acute TM perforations will heal spontaneously, both in animals and human beings. A second inadequacy of acute perforation models is that they are not analogous to the salient problem in human beings: long-standing TM perforation. The ideal animal model must have a TM perforation that is permanent, well-epithelialized, and free from infection. The perforation must also be subtotal to preserve a rim of membrane for experimental manipulations. In the chinchilla, we have identified a hardy animal with a short, wide ear canal and relatively large tympanic membranes. Thermal myringectomy, followed by medial infolding of TM microflaps, has resulted in permanent, subtotal chronic TM perforations in the chinchilla animal model. Of the 19 chinchillas (38 TMs) perforated, chronic subtotal perforations were created in 32 ears, 6 to 8 weeks after the initial procedure (84% success). Persistent infection or TM regeneration despite reperforation was recorded in 6 ears (16%) failure). This model is currently being used to assess various biomembrane scaffolds impregnated with growth-promoting substances in the regeneration of a physiologically sound TM, initially in our animal model and then in human beings. We envision the development of a biomembrane disc impregnated with biorecombinant growth factors that may provide a simple office technique for the repair of chronic, non-infected TM perforations.

Animals↗
PubMed1992

Repair of chronic tympanic membrane perforations using epidermal growth factor.

Perforation of the tympanic membrane (TM) is a frequent cause of conductive hearing loss. Persistent TM perforations often require surgical repair with an autologous tissue graft to restore hearing and prevent recurrent infection. While highly efficacious, this method of closure requires a relatively complex and expensive microsurgical procedure. We have recently developed a chronic TM perforation model in the chinchilla for use in the exploration of novel methods of TM repair.

Animals↗
PubMed1992

Radiographic differential diagnosis of petrous apex lesions.

As a consequence of improved diagnostic imaging modalities, otologists have encountered a steadily increasing number of petrous apex lesions in recent years. Contemporary imaging techniques not only provide precise anatomic localization of the lesion, but also are able to suggest specific tissue diagnoses in the majority of cases. Computed tomography (CT), by virtue of its sensitivity and low false-positive rate, is the screening examination of choice in a patient suspected of having a petrous apex lesion. Once a lesion is identified, it is often necessary to obtain a combination of CT and magnetic resonance imaging (MRI). Computed tomography is important in the detection of osseous erosion as well as in the evaluation of the extent of pneumatization and marrow formation. It also provides important details about potential surgical routes to this relatively inaccessible region. Magnetic resonance imaging provides information about the composition of the lesion that cannot be readily discerned on CT scans. In the great majority of cases, it is capable of differentiating between petrous apicitis, cholesterol granuloma, osteomyelitis, cholesteatoma, and neoplasms such as schwannoma, meningioma, chondroma, and chordoma. In the interpretation of MRI scans, a familiarity with the typical appearance of the lesions that affect the petrous apex on T1-weighted, T2-weighted, and gadolinium-enhanced images is essential. A combination of MRI and CT scanning is also necessary to evaluate normal anatomic variations, such as giant air cells and asymmetric bone marrow, which may at times, on MRI alone, simulate pathologic conditions.

Aneurysm, Infected↗
PubMed1992

Analysis of chromosome 22 deletions in neurofibromatosis type 2-related tumors.

The neurofibromatosis type 2 (NF2) gene has been hypothesized to be a recessive tumor suppressor, with mutations at the same locus on chromosome 22 that lead to NF2 also leading to sporadic tumors of the types seen in NF2. Flanking markers for this gene have previously been defined as D22S1 centromeric and D22S28 telomeric. Identification of subregions of this interval that are consistently rearranged in the NF2-related tumors would aid in better defining the disease locus. To this end, we have compared tumor and constitutional DNAs, isolated from 39 unrelated patients with sporadic and NF2-associated acoustic neuromas, meningiomas, schwannomas, and ependymomas, at eight polymorphic loci on chromosome 22. Two of the tumors studied revealed loss-of-heterozygosity patterns, which is consistent with the presence of chromosome 22 terminal deletions. By using additional polymorphic markers, the terminal deletion breakpoint found in one of the tumors, an acoustic neuroma from an NF2 patient, was mapped within the previously defined NF2 region. The breakpoint occurred between the haplotyped markers D22S41/D22S46 and D22S56. This finding redefines the proximal flanking marker and localizes the NF2 gene between markers D22S41/D22S46 and D22S28. In addition, we identified a sporadic acoustic neuroma that reveals a loss-of-heterozygosity pattern consistent with mitotic recombination or deletion and reduplication, which are mechanisms not previously seen in studies of these tumors. This finding, while inconsistent with models of tumorigenesis that invoke single deletions and their gene-dosage effects, lends further support to the recessive tumor-suppressor model.

Blotting, Southern↗
PubMed1992

Clinical manifestations and audiologic diagnosis of acoustic neuromas.

If an AN is suspected, a detailed patient history and a thorough otologic and neurotologic physical examination should be carried out. The first echelon of diagnostic testing begins with a pure tone audiogram, speech reception threshold, speech discrimination testing, and acoustic reflex testing. If the clinician is even moderately suspicious of the presence of an AN, the patient should undergo a Gd-MRI scan. If suspicion is low, an ABR should be performed, and if negative, the patient should be reevaluated periodically.

Audiometry↗
PubMed1992

Selection of surgical approach to acoustic neuroma.

A variety of surgical approaches are available in the management of acoustic neuroma. Each procedure has certain advantages and disadvantages in terms of surgical exposure, the capability of preserving cranial nerve function, and postoperative morbidity. This article advocates tailoring the operative approach to each acoustic neuroma according to its size, location, and clinical manifestations.

Age Factors↗
PubMed1991

Stapedectomy: long-term hearing results.

The initial improvement in hearing following stapedectomy usually deteriorates with the passage of time. We studied the long-term results of stapedectomies performed on 42 patients (49 ears) between 1959 and 1969 who had a minimum follow-up of 18 years. Both air conduction (AC) and bone conduction (BC) thresholds progressively deteriorated over the long term. The degree of BC loss paralleled that expected from presbycusis alone. A greater deterioration was noted in the AC levels, producing a recurrent conductive hearing loss in the speech frequencies. Age at the time of surgery had no effect on the long-term outcome. Comparison of the average preoperative speech discrimination scores (SDS) to the 1-year postoperative SDS and the long-term SDS revealed a 1.1% and 16.7% drop, respectively. The improvement in the average speech reception threshold (SRT) obtained 1 year postoperatively deteriorated by less than 1 dB per year over the long term. Patients with a higher SDS (more than 95%) preoperatively fared better in the maintenance of speech discrimination than those with a lower SDS (less than 95%). The preoperative SRT level was predictive of the timing for the requirement of hearing amplification. The postoperative SRT level was predictive of the timing for the requirement of hearing amplification. The caused by presbycusis, combined with a recurrent conductive loss in the speech frequencies rather than cochlear otosclerosis. Although the decline in hearing following stapedectomy exceeds the rate of hearing loss due to presbycusis, many individuals, after successful stapes surgery, are able to delay the need for hearing amplification for longer periods than had been previously reported.

Audiometry, Pure-Tone↗
PubMed1991

Spontaneous hemotympanum associated with chronic middle ear effusion.

Idiopathic or spontaneous hemotympanum (SH) is an uncommon disorder characterized by a black-blue tympanic membrane discoloration as a result of recurrent hemorrhage in the middle ear or mastoid in the presence of eustachian tube obstruction. Initial evaluation of a blue middle ear mass includes an audiogram and computed tomography (CT) scan with intravenous contrast. CT may identify congenital vascular malformation or bone erosion due to chronic otitis media or tumors. A magnetic resonance imaging (MRI) scan is useful in distinguishing hemotympanum from a vascular tumor and avoiding angiography, which is associated with significant morbidity. Evidence suggests that secretory otitis media and SH are different phases of the same disease process.

Child↗
PubMed1990

Gadolinium-DTPA enhanced magnetic resonance imaging in acoustic neuroma diagnosis and management.

Gadolinium-DTPA (Gd-DTPA) is a paramagnetic contrast agent that increases the intensity of acoustic neuromas (AN) on T1-weighted magnetic resonance imaging (MRI) scans. Over a 9-month period we have reviewed Gd-DTPA-enhanced MRI scans on 32 consecutive cases (35 tumors) involving the internal auditory canal (IAC) and cerebellopontine angle (CPA). The majority of patients (84%) were imaged on latest generation 1.5 Tesla scanners. Every tumor studied showed marked enhancement after Gd-DTPA administration. This improved contrast permitted identification of three small tumors that were not evident on unenhanced scans. Gd-DTPA appears to be particularly useful in the evaluation of recurrent or residual AN. In three patients with known residual tumor after planned subtotal excisions, the remaining tumor could only be differentiated from surrounding scar, cerebral spinal fluid (CSF), and brain parenchyma after contrast enhancement. In one of these, a small rim of tumor capsule left on the facial nerve was evident only on Gd-DTPA-enhanced T1 images. Gd-DTPA also provides a more reliable estimate of the depth of tumor penetration in the IAC. This information is useful in selecting candidates suitable for a hearing conservation approach.

Contrast Media↗
PubMed1990

Contrast-enhanced MR imaging of the facial nerve in 11 patients with Bell's palsy.

Contrast-enhanced MR images (at 1.5 T) were obtained in 11 patients with facial palsy. The group included five people with acute idiopathic facial (Bell's) palsy, three with chronic idiopathic facial palsy, and one each with acute facial palsy after local radiation therapy, acute facial palsy resulting from herpes zoster virus infection, and facial palsy caused by facial neuroma. Eight of the 11 patients demonstrated marked enhancement of the affected facial nerve from the labyrinthine portion through the descending canal. Three patients also demonstrated mild enhancement of the distal canalicular portion of the facial nerve, simulating small distal acoustic neuromas. No difference in the pattern of enhancement between the acute or chronic Bell's palsy patients was seen. Radiographic resolution appeared to lag behind clinical resolution. The facial neuroma appeared distinct from the other lesions as a focally enhancing mass. The enhancement pattern in the Bell's group correlated with the histopathologic features of Bell's palsy and is consistent with the viral hypothesis of the syndrome. Thin-section contrast-enhanced MR scans are recommended for individuals with atypical presentation of facial paralysis. In the proper clinical setting, contrast-enhanced MR imaging may permit a positive radiographic diagnosis of Bell's palsy, which has previously been a diagnosis of exclusion.

Adult↗