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Biomedical subjects

R K Jackler

Publications and source records attributed to R K Jackler.

At least 37 records · Page 2Linked to original sources
PubMed1998

Germline screening of the NF-2 gene in families with unilateral vestibular schwannoma.

Vestibular schwannoma may present clinically in two forms: sporadic unilateral or hereditary bilateral. Familial transmission of vestibular schwannoma is known to occur only in neurofibromatosis type II (NF-2). We have previously described the clinical characteristics of unilateral vestibular schwannoma presenting in families, in the absence of ther criteria necessary for the diagnosis of NF-2. Polymerase chain reaction-single strand chain polymorphism was used to screen for germline NF-2 gene mutations in six families with unilateral vestibular schwannoma. Direct sequencing of DNA from blood was done in affected subjects from three families. No germline mutations were identified. Because NF-2 gene mutations are detected in only 33% of patients with NF-2, hereditary transmission of mutations cannot be entirely excluded. However, in the absence of germline mutations in the NF-2 gene, familial occurrence of unilateral vestibular schwannoma more likely represents either a chance somatic NF-2 gene mutation or originates from a separate genetic loci.

Case-Control Studies↗
PubMed1998

The vulnerability of the vein of labbé during combined craniotomies of the middle and posterior fossae.

During combined middle and posterior cranial fossae ("petrosal") approaches to the skull base, the anastamotic vein of Labbe, which bridges between the inferior surface of the temporal lobe and the transverse sinus is placed at risk. Occlusion of this vein, which may drain a large section of the temporal and parietal lobes, may lead to speech, memory, and/or other cognitive disorders. Labbe may be injured along its course on the inferior aspect of the temporal lobe where it may be laceraed during dural incision or thrombosed due to prolonged or overly vigorous retraction. The anastamotic segment of the vein, which bridges between the temporal lobe and transverse sinus, may be avulsed during elevation of the temporal lobe or injured during tentorial division. Labbé may course in close proximity to the upper surface of the tentorium or even travel within it for a short segment of its course en route to the transverse sinus. This article reviews the anatomy of the vein of Labbé, discusses its clinical significance, and highlights the technical points relevant to the preservation of this important structure.

Journal Article↗
PubMed1998

Lipomas of the internal auditory canal and cerebellopontine angle.

OBJECTIVE: To evaluate lipomas of the internal auditory canal (IAC) and cerebellopontine angle (CPA). STUDY DESIGN: Retrospective review. METHODS: Review of a multi-institutional series of 17 lipomas of the IAC/CPA, combined with a Medline review of the 67 cases reported in the world literature. RESULTS: This series of 17 IAC/CPA lipomas is the largest reported series to date, bringing the total number of documented cases to 84. There appears to be a nearly 2:1 male to female predominance. Sixty percent were left-sided lesions, and three were bilateral. Hearing loss, dizziness, and tinnitus were the most common presenting symptoms. Surgical resection was performed in 52 (62%) of these lesions; however, total tumor removal was accomplished in only 17 (33%), which is most likely because of the fact that these tumors tend to have a poorly defined matrix and a dense adherence to neurovascular structures. Sixty-eight percent of patients experienced a new deficit postoperatively, 11% were unchanged, and only 19% improved with no new deficit. Only one documented case of tumor growth was identified; however, the reported follow-up was short (average, less than 3 years). CONCLUSION: With the magnetic resonance imaging techniques now available, lipomas can be reliably differentiated from other masses within the CPA and IAC, so histopathologic diagnosis is rarely necessary. Because of the potential for significant morbidity with resection of these lesions, we believe that conservative follow-up is the best treatment option for patients with these rare lesions. Surgery is indicated only when significant progressive or disabling symptoms are present.

Adolescent↗
PubMed1998

Hearing preservation in patients undergoing vestibular schwannoma surgery: comparison of middle fossa and retrosigmoid approaches.

OBJECT: The goal of this retrospective study was to evaluate hearing preservation after surgery for vestibular schwannoma in which the middle fossa (MF) or retrosigmoid (RS) approaches were used. Hearing preservation in vestibular schwannoma surgery can be achieved by using either the MR or RS approach. Comparative outcome data between these approaches are lacking, and, as a result, selection has generally been determined by the surgeon's preference. METHODS: The authors have compared removal of small vestibular schwannomas via MF and RS approaches with regard to hearing preservation and facial nerve function. The study group was composed of consecutively treated patients with vestibular schwannoma, 48 of whom underwent operation via an MF approach and 50 of whom underwent the same number of RS operations. Tumors were divided into size-matched groups. Hearing results were recorded according to the American Academy of Otolaryngology-Head and Neck Surgery criteria, and facial nerve outcome was recorded as the House-Brackmann grade. Overall, 26 (52%) of the patients treated via the MF approach achieved a Class B or better hearing result compared with seven (14%) of the RS group. Some hearing was preserved in 32 (64%) of the patients in the MF group and in 17 (34%) of the RS group. The results obtained by using the MF approach were superior for intracanalicular tumors (p=0.009, t-test), and for tumors with a cerebellopontine angle (CPA) component measuring 0.1 to 1 cm (p=0.006, t-test). For tumors in the CPA that were 1.1 to 2 cm in size, our data were inconclusive because of the small sample size. Facial weakness was seen more frequently after MF surgery in the early postoperative period, but results were equal at 1 year. CONCLUSIONS: The results of this study have demonstrated a more favorable hearing outcome for patients with intracanalicular tumors and tumors extending up to 1 cm into the CPA that were removed via the MF when compared with the RS approach.

Adolescent↗
PubMed1998

Comparison of response amplitude versus stimulation threshold in predicting early postoperative facial nerve function after acoustic neuroma resection.

OBJECTIVE: This study aimed to better predict the early postoperative facial nerve (FN) function after acoustic neuroma (AN) resection. STUDY DESIGN: This study was a prospective series. SETTING: The surgery was conducted in a tertiary referral center. PATIENTS: A total of 44 patients undergoing AN resection with cranial nerve monitoring were observed for at least 1 year after surgery. MAIN OUTCOME MEASURES: The predictive value of amplitude of the FN stimulus response on the early postoperative FN function was measured. RESULTS: Cranial nerve monitoring in AN surgery was used to obtain the stimulation threshold and facial electromyograph response amplitudes to FN stimulation proximal and distal to the tumor at 0.2 V above threshold. Thirty-eight of forty-four patients studied had a low postresection threshold (< or = 0.1 V). Of these (10), 26% sustained a postoperative FN dysfunction of House-Brackmann (HB) grades 3-6. In an effort to improve the predictive value from cranial nerve monitoring, the response amplitude to suprathreshold stimulation was compared with the threshold and FN function. Eighty-nine percent of patients with an amplitude of > or =200 microV had a grade 1-2 early postoperative FN function, whereas only 41% of patients with < 200 microV had a grade 1-2 early postoperative FN function (p = 0.00035). Eighty-eight percent of patients with both a low threshold and high amplitude had a grade 1-2 early postoperative FN function, whereas the remaining 12% of patients had a grade 3-6 FN function (p = 0.0032). The false-positive rate of threshold alone in predicting a grade 1-2 FN function was 26% compared to 12% for low threshold and high amplitude combined. CONCLUSIONS: The use of FN threshold and amplitude together is superior to threshold alone as a predictor of early postoperative FN function.

Adolescent↗
PubMed1998

Acoustic neuromas presenting with normal or symmetrical hearing: factors associated with diagnosis and outcome.

OBJECTIVE: To evaluate the clinical features leading to diagnosis in patients with acoustic neuroma (AN) who present with normal or symmetrical hearing. Underlying tumor characteristics are also studied to identify a possible explanation for this unique presentation in the AN population. STUDY DESIGN: Retrospective case review comprising patients who were identified as having AN that presented with normal audiometry. SETTING: A tertiary referral center. PATIENTS: Patients with AN who met the criteria for normal were included in the report. For this study, abnormal audiometry is defined as an interaural difference of > or =15 dB at a single frequency or > or =10 dB at two or more frequencies, and an interaural speech reception threshold difference of > or =20 dB, or a speech discrimination score of > or =20%. MAIN OUTCOME MEASURES: Presenting symptoms and signs, clinical features that led to the diagnosis of AN, auditory brain stem response results, tumor location, size and relationship to temporal bone landmarks, surgical intervention, surgical outcome, and results of hearing preservation attempts were tabulated for each patient. RESULTS: A total of 29 patients (5%) were identified who had normal or symmetrical pure-tone audiograms between 500 and 4,000 Hz. The average difference in speech reception threshold between tumor and nontumor ear was 3.2 dB, and the average difference in speech detection score was 2.6%. The most common presenting symptoms that led to the diagnosis of the AN were dysequilibrium/vertigo (12 cases), cranial nerve V and VII abnormalities (11 cases), routine screening for families with neurofibromatosis type 2 (5 cases), asymmetrical tinnitus (4 cases), headaches (4 cases), unilateral subjective hearing difficulty (4 cases), and incidental finding during evaluation for another problem (4 cases). The average tumor size was 19 mm, with five cases presenting with tumors of size > or =30 mm. Nineteen patients underwent a hearing preservation procedure (middle fossa or retrosigmoid), 11 of whom had useful hearing postoperatively. CONCLUSIONS: Despite normal audiometry, patients presenting with imbalance or vertigo, Vth or VIIth cranial nerve deficits, or unilateral hearing complaints may warrant further evaluation to rule out the possibility of AN or other retrocochlear lesion. To seek an explanation for this phenomenon, the incidence of various tumor characteristics (e.g., depth of penetration into the internal auditory canal and degree of porous erosion) is discussed and compared with the entire AN population.

Adult↗
PubMed1998

Facial nerve surgery in the 19th and early 20th centuries: The evolution from crossover anastomosis to direct nerve repair.

The historical aspects of facial nerve (FN) anatomy and of Bell's palsy have long been favorite topics of otologic historians. Little attention has been paid, however, to the evolution of FN surgery, a subject with a remarkably rich and engaging history. In the early 13th century, Roland, an Italian surgeon, used a red hot iron to coapt severed nerve endings. In the 17th century, Ferrara, another Italian, sutured injured nerves with tortoise tendon dipped in hot red wine. It was not until the late 19th century that peripheral nerve suture became a subject of serious scientific study. Although it is ironic, the course of events suggests that the evolution of FN repair was greatly stimulated by the development of the modern mastoid operation. Whereas the simple mastoid operation practiced by Wilde (1853) and others carried little risk of FN injury, more adventuresome procedures such as radical mastoidectomy (Kessel, 1885) carried a much greater risk. The abundance of iatrogenic palsies during this era undoubtedly did much to motivate surgeons to seek a better means of restoring facial animation. Most surgeons would be surprised to learn that crossover anastomoses predated direct nerve repair by nearly half a century. In 1879, the German surgeon Drobnik performed the first facial-spinal accessory anastomosis. Over the next two decades, numerous articles were written (most notably by Sir Charles Balance and Harvey Cushing) on crossovers between the FN and cranial nerves IX, X, XI, and XII. Although a few tentative attempts at reapproximating severed FNs took place in the first two decades of this century, it was not until 1925 that an actual suture repair of an intratemporal injury was undertaken. This feat was first accomplished by the famous hand surgeon Sterling Bunnell and shortly thereafter by the otolaryngologist Robert Martin. The evolution of FN surgery in the days predating the operating microscope is a rich tapestry of colorful personalities and clashing egos, which saw promising advances relegated to obscurity and some previously obscure techniques become progressively more promising.

Anastomosis, Surgical↗
PubMed1997

Removal of jugular foramen tumors: the fallopian bridge technique.

Despite recent advances in neuroradiographic and electrophysiologic assessment, the surgical extirpation of lesions of the bony skull base remains challenging. Moreover, as surgeons have gained experience in removing tumors from the irregular osteologic confines of the skull base, attention has been directed toward preservation of vital neural and vascular structures traversing the operative field. This report describes the creation of a fallopian bridge with preservation of the facial nerve in removing tumors that arise within or juxtaposed to the jugular fossa. Thirty-five patients are reported herein with analysis of pathology, surgical approach, and outcome. An algorithm for use of the fallopian bridge, as opposed to facial nerve mobilization and rerouting, is presented with particular emphasis on limitation of this selective procedure.

Adult↗
PubMed1997

Are acoustic neuromas encapsulated tumors?

In articles and chapters on the subject of acoustic neuroma, it is almost invariably stated that they are well-encapsulated tumors. During surgical procedures, blunt mechanical dissection defines a natural subsurface cleavage plane that leaves intact a several millimeter thick rind of tumor surface. Occasionally, as a concession to neural integrity, less than complete resection is elected, leaving behind this "capsular" remnant. To clarify the nature of the surface of acoustic neuromas and to test whether this long held description is indeed correct, a microscopic analysis of 10 surgical specimens was performed. A wedge was harvested from the free surface of the tumor in the mid cerebellopontine angle that included a large, undisturbed section of the tumor surface. Histologic analysis showed that for most of the tumor surface only an extremely thin (3 to 5 microm) layer of connective tissue envelops the tumor. Neoplastic Schwann cells, which extend essentially to the margin of the tumor, were found to be somewhat flattened and compressed in the vicinity of the surface. Although acoustic neuromas are surrounded by a continuous layer of connective tissue, it is so exceptionally thin (on average less than the diameter of a red blood cell) that its edge cannot be visualized intraoperatively by a surgeon. Because the pathologic definition of a capsule is a thick, enveloping layer of connective tissue that is both micro- and macroscopically evident, it must be concluded that acoustic neuromas are nonencapsulated, at least in the conventional sense of the term. The surface peel observed intraoperatively is surgically produced during tumor debulking by cleaving of the looser central component from the more compressed portion of neoplastic cells that lies immediately beneath the free margin of the lesion.

Connective Tissue↗
PubMed1997

Exophytic brain tumors mimicking primary lesions of the cerebellopontine angle.

The vast majority of cerebellopontine angle (CPA) tumors are extraaxial masses arising from either the eighth nerve (acoustic neuroma) or meninges (meningioma). Rarely, a tumor that arises from the brain parenchyma may protrude laterally to present with a clinical and radiographic picture simulating that of the much more common extraaxial lesions. Three individuals with CPA lesions that ultimately proved at operation to be exophytic brain tumors (pontine medulloblastoma, cerebellar astrocytoma, and fourth ventricular ependymoma) are described. The clinical manifestations of these lesions, although not entirely typical, fell well within the possible range of presentation of benign tumors primary to the CPA. In two of these cases the tumor actually penetrated into the internal auditory canal. As the optimal management strategy for treating parenchymal tumors differs substantially from that for extraaxial lesions, it is essential that the surgeon have a preoperative awareness of the lesion's nature before embarking on a surgical endeavor. Critical to arriving at the correct diagnosis is the close examination of preoperative imaging studies. The clinician should be alerted to the possibility that a CPA tumor is of intraaxial origin when the preoperative magnetic resonance imaging scan shows 1) blurring of the margin between the tumor and brainstem or cerebellum; 2) a degree of peritumoral hyperintensity on T2-weighted scans disproportionate to the size of the extraaxial mass; and 3) dilation of the lateral recess of the fourth ventricle.

Aged↗
PubMed1997

Familial occurrence of unilateral vestibular schwannoma.

Vestibular schwannoma (VS) may present clinically in one of two forms: sporadic unilateral or hereditary bilateral. Almost all cases of familial transmission have been associated with the diagnosis of neurofibromatosis type II (NF-2). In this report, we describe nine families (18 individuals) presenting with unilateral VS without evidence of NF-2. In four of the nine families, the affected individuals were of parent-offspring relationship, in three families they were cousin-cousin, and in the remaining two families, they were sibling-sibling and aunt-nephew. No other members of the families were diagnosed with NF-2. There was no evidence for gender predilection or genomic imprinting among affected individuals. This study suggests that familial occurrence of unilateral VS may be genetically inherited as it occurs more commonly than would be estimated by chance alone. Future genetic studies will elucidate whether occurrence of unilateral VS in these families represents a variable expression of NF-2, chance occurrence of unilateral VS in families, or a new genetic disorder.

Adult↗
PubMed1997

Radiation-induced tumors of the temporal bone.

OBJECTIVE: To discuss a rare but devastating complication following radiotherapy to the head and neck: radiation-induced malignancies of the temporal bone. STUDY DESIGN: A retrospective case review comprising five patients with radiation-induced tumors involving the temporal bone. SETTING: A tertiary referral center. PATIENTS: Patients with tumors involving the temporal bone who have satisfied the criteria for being considered radiation-associated. MAIN OUTCOME MEASURES: Initial tumor histology, radiation-induced tumor histology, latency between radiotherapy and diagnosis of the radiation-associated malignancy, amount of radiation received, therapeutic interventions, and survival statistics for each patient. RESULTS: Five cases of radiation-induced tumors of the temporal bone are presented (two osteosarcomas, two fibrosarcomas, and one squamous cell carcinoma). All five temporal bone tumors occurred in individuals that had previously received > 5,000 cGy of radiation. The initial histologic diagnoses included two astrocytomas, a glomus jugulare, a malignant meningioma, and a vestibular schwannoma. There was an average latency period of 15 years (range, 7-23 years) between completion of radiation and diagnosis of the malignancy. Four patients were treated with resection plus chemotherapy, and one decided against therapy. The prognosis was poor, with survival time of 7-14 months after the diagnosis of the radiation-induced tumor. Only one patient survived > 14 months and is currently free of disease, 3 years after diagnosis of the radiation-induced tumor. CONCLUSIONS: Although radiation-induced tumors of the temporal bone occur with a very low incidence, their prognosis is extremely poor. The remote possibility of a radiation-associated tumor should be factored in when deciding upon the most appropriate therapeutic modality for individuals with neoplasms of the CNS and head and neck. Such considerations are particularly germane when contemplating radiation therapy for a benign lesion (e.g., glomus jugulare, acoustic neuroma, or meningioma) in an individual with a long predicted lifespan.

Adolescent↗
PubMed1997

Acoustic neuroma surgery: outcome analysis of patient-perceived disability.

OBJECTIVE: Numerous studies have investigated the outcome of acoustic neuroma (AN) treatment using classical medical measures. In an effort to describe the long-term lifestyle consequences of AN removal from the patient's perspective, patients filled out detailed questionnaires concerning their functional status. STUDY DESIGN: This was a retrospective survey. SETTING: This study was performed at a tertiary referral center. PATIENTS: A total of 130 late postoperative acoustic neuroma patients were surveyed a minimum of 6 months following surgery (average, 39 months). Survey response rate was 65% (130/200). MAIN OUTCOME MEASURES: The main outcome measures were the patient's perception of their hearing, balance, facial expression, and eye function in relation to its impact upon the activities of daily life. A comparison of pretreatment with long-term posttreatment functional levels. RESULTS: When asked to designate their "most significant" symptom, hearing loss was by far most prevalent (61.3%), followed by balance troubles (14.3%) and facial weakness (10.1%). The relatively low incidence of facial weakness as the patient's dominant complaint was somewhat surprising. When considering the incidence of each symptom, women were more likely to complain of facial weakness, dry eye, and headache, whereas men had a marginally higher incidence of hearing loss and imbalance. Patient age had no apparent influence upon either the distribution or severity of symptomatic complaints. Both hearing in the tumor ear and overall auditory function (e.g., the ability to understand in a restaurant) tended to worsen following surgery. One finding, which was both unanticipated and intriguing, was the improvement in sound localization ability reported by 57% of patients following surgery. Although the proportion of patients complaining of frequent tinnitus increased postoperatively, the number of patients who found the tinnitus troublesome decreased markedly. In terms of balance function, only 31% preoperatively and 15% postoperatively described themselves as free of balance difficulties. An aid to ambulation (e.g., cane, walker) was needed in five patients (4%) preoperatively, two of whom regained the ability to walk independently following tumor removal. CONCLUSIONS: These functional outcome data provide much useful information to both patient and clinician to consider when contemplating the optimal course of AN management. Although virtually all acoustic neuroma patients have some degree of persistent symptoms over the long-term, the data indicates that most of these are attributable to the tumor itself as opposed to the after effects of its surgical removal. The relatively slight differences between preoperative and late postoperative symptom profiles was a rather unanticipated finding. As the degree of disability tends to increase with larger tumor sizes, these data tend to support a policy of early intervention.

Adolescent↗
PubMed1997

Socioeconomic impact of acoustic neuroma surgery.

OBJECTIVE: This study aimed to assess the impact of acoustic neuroma (AN) surgery on socioeconomic function. STUDY DESIGN: This study was a retrospective postal survey. SETTING: The study was performed at a tertiary referral center. PATIENTS: One hundred thirty late postoperative AN patients were surveyed a minimum of 6 months after surgery (average 39 months). The survey response rate was 65% (130 of 200). MAIN OUTCOME MEASURES: These included effect of AN surgery on employability, income, activities of daily living, social involvement, and psychological well-being. RESULTS: When comparing preoperative occupational status with latest follow-up, 2 of 125 (1.6%) became unemployed from their usual occupations. An additional 15 of 125 (12%) retired, attributing their retirement to the effects of the tumor itself (3), an aftermath of surgery (2), and causes unrelated to their AN (10). After AN removal, two formerly unemployed patients became employed. Among those remaining employed, there was no significant impact of surgery on either income or work responsibility. Return to normal activity was gradual: < or = 6 weeks, 31%; < or = 3 month, 64%; and < or = 6 months, 84%. Among activities of daily living, the tasks most often impaired (both before and after tumor removal) were ladder climbing and night driving, whereas dressing and bathing were seldom problematic. Overall, patients reported a minor decline in ability to perform routine daily activities after tumor removal. Social function (contact with friends, community involvement, and participation in sports) changed little after surgery. The incidence of both stress and depression decreased slightly after tumor removal. CONCLUSIONS: The economic, social, and psychological impact of AN and its surgical management appears to be relatively minor, with few individuals having life altering consequences.

Activities of Daily Living↗
PubMed1996

The early history of the neurofibromatosis. Evolution of the concept of neurofibromatosis type 2.

Although neurofibromatosis (NF) became widely recognized as a pathologic entity in the late 19th century, only relatively recently has a clear distinction been made between its generalized form and the central variety. The latter form is typified by bilateral acoustic neuromas (ANs), which may be accompanied by other intracranial tumors, in particular, meningiomas. Up until almost the current era, confusion regarding the protean manifestations of the 2 types of NF existed in the minds of clinicians and in the literature. In 1987, a consensus panel of the National Institutes of Health differentiated the clinical manifestations associated with classic von Recklinghausen syndrome from those of the predominantly intracranial subtype and they were subsequently deemed NF type 1 (NF-1) and NF type 2 (NF-2), respectively. During the last few years, the genetic flaws that underlie these 2 syndromes have been elucidated, revealing that their origins lie in defects on separate chromosomes. The early literature on the subject included repeated descriptions of patients with manifestations typical of NF-2. The investigators, however, considered the intracranial lesions to be merely 1 facet of the generalized form of the disease. A few prescient individuals, however, demonstrated an appreciation for the distinguishing characteristics between these superficially similar, yet quite different, syndromes. The goals of this article are to trace the evolution of the concept of NF-2 as a distinct clinical entity from NF-1 and to assess the early awareness of and attitudes toward bilateral ANs, familial ANs, and ANs associated with other intracranial tumors.

Europe↗