Acoustic Tumors Research Articles

Endolymphatic Duct Violation During Retrosigmoid Dissection of the Internal Auditory Canal: A Human Temporal Bone Radiographic Study

Successful hearing preservation after acoustic neuroma resection is sometimes complicated by delayed hearing deterioration. The goal of this study was to investigate the hypothesis that internal auditory canal (IAC) drilling during retrosigmoid acoustic neuroma removal may result in endolymphatic duct (ELD) injury, a potential cause of delayed hearing loss (HL) after hearing preservation surgery. Temporal bone anatomic and radiographic study and literature review. Twenty-one human temporal bones were analyzed with high-resolution multislice computed tomography (HRMCT) and subjected to standard retrosigmoid IAC dissection with labyrinthine preservation and follow-up HRMCT for analyses of the ELD. A MEDLINE search was performed of studies documenting long-term hearing preservation outcomes after retrosigmoid dissection. Five of 21 (24%) bones were found to have violation of the ELD despite preservation of labyrinthine structures and the endolymphatic sac. These results correlate with the mean incidence of long-term hearing decline (26.6%). Reviews of human and animal studies indicate that injury to the ELD may create endolymphatic hydrops. The ELD is vulnerable to injury during IAC dissection even if labyrinthine structures at the lateral aspect of the IAC are preserved. These findings may be helpful in explaining and potentially preventing some cases of long-term hearing deterioration that may be a result of endolymphatic hydrops after ELD injury during acoustic tumor removal. Careful preoperative review of imaging studies using HRMCT may prove useful before retrosigmoid dissection.

The history of neurosurgery at Temple University.

TEMPLE UNIVERSITY'S NEUROSURGERY program has had a colorful and distinguished history since its creation in 1929. It has always functioned under challenging circumstances with limited resources but with a strong sense of mission. It was one of the 20 neurosurgical training programs in existence when the American Board of Neurosurgery was founded in 1940. Over the past 64 years, the program has trained approximately the same number of neurosurgeons, many of whom have contributed significantly to our specialty. Some of the advances pioneered in part at Temple include clinical hypothermia (Fay), the biplanar stereoscopic angiographic unit (Chamberlain), human stereotactic surgery (Spiegel and Wycis), lumboperitoneal shunts (Scott), posterior lumbar interbody fusion (Lin), microsurgery for acoustic tumors (Buchheit), and new pharmacological approaches to neuroprotectors (Strauss and Narayan). The Temple neurosurgery program has survived many challenges in the past and will no doubt weather the current financial and medicolegal challenges that confront the neurosurgical community in Philadelphia. It remains a strong clinical program that serves an otherwise underserved community and attracts patients beyond its geographic area because of its strong clinical reputation and the excellence of its clinical faculty and residents.

Cervical dumbbell meningioma and thoracic dumbbell schwannoma in a patient with neurofibromatosis

The occurrence of both dumbbell meningioma and dumbbell schwannoma in one patient has not been reported in the literature. We present a 16-year-old female patient, who had progressive bilateral hearing impairment for 5 years and a progressively enlarged, non-tender neck mass for 1.5 years. Mild motor weakness over her right upper limb was noted 1 week before admission. No café-au-lait spot was noted. Magnetic resonance imaging (MRI) revealed bilateral cerebellopontine angle tumors, a C1-2 dumbbell tumor, and a T5-6 dumbbell tumor. Neurofibromatosis type 2 was diagnosed. The cervical spine and thoracic spine tumors were removed via one-staged combined posterior (laminectomy) and antero-lateral (transforaminal or thoracoscopic) approaches during two operations performed 1 month apart. The pathology revealed meningioma and schwannoma, respectively. The patient had good recovery after these two operations and her motor function improved. Six months after the second surgery, radiosurgery was performed for the bilateral acoustic tumors, because of enlarged tumor size on follow-up MRI. To the best of our knowledge, this is the first case reported in the literature of a patient, having both dumbbell meningioma and dumbbell schwannoma. A literature review of the dumbbell tumors was done, and their treatment strategies were discussed.

The otodystrophies: Diagnosis and differential diagnosis

The imaging evaluation of hearing loss is usually focused on inflammatory entities, especially chronic otitis/cholesteatoma and cerebellopontine angles lesions, particularly acoustic tumors. This discussion concerns several developmental and acquired entities. The developmental entities referred to as the otodystrophies include otosclerosis, Paget’s disease, fibrous dysplasia, and osteogenisis imperfecta. Otosyphilis and postradiation temporal bone changes are also included because of the overlapping imaging appearances.

Comparison of retrosigmoid and middle fossa approaches for vestibular schwannoma

Problem: Hearing preservation during acoustic tumor removal is generally attempted using 1 of 2 approaches: the middle fossa or retrosigmoid. This study evaluates hearing and facial nerve preservation rates using the retrosigmoid approach and compares the postoperative results with those reported in the literature using the middle fossa technique. This comparison was conducted to determine which approach offers an opportunity for the best patient outcome. Methods: Hearing preservation was attempted in 46 patients with vestibular schwannomas. Tumor size ranged from 0.5 to 2.5 cm. A retrosigmoid approach and direct eighth nerve monitoring (DENM) was used for all patients. Outcome measures of hearing preservation, facial nerve function, and cerebral spinal fluid leak were evaluated and compared to those reported using the middle fossa approach. Results: Hearing was preserved in 71% of patients with tumors 1 cm or smaller and 32% of patients with tumors between 1 and 2.5 cm. Facial nerve preservation rates were 94% (HB 1–2) for tumors smaller than 2 cm. Conclusion: The retrosigmoid approach with DENM provides rates of hearing preservation comparable to those reported for the middle fossa approach for the resection of vestibular schwannomas. Facial nerve function, both short-term and long-term, appears to be better with the retrosigmoid approach. Significance: Resection of vestibular schwannomas via either the retrosigmoid approach, the use of DENM, or the middle fossa approach provides comparable results for hearing preservation. However, facial nerve function appears to be better preserved with the retrosigmoid approach. Support: None reported.

The application of vestibular evoked myogenic potentials (VEMP) in otoneurosurgery

Objectives: It is the aim of the present paper to use VEMP recordings in the perioperative assessment of patients who have to undergo various otoneurosurgical or otosurgical procedures Methods: VEMP recordings were done routinely by bone-conduction stimulation at the mastoid and EMG recording at the sternocleidomastoid muscle (SCM) of each side before and after the surgery. The intraoperative stimulation was done at the vestibular nerve by a monopolar electrode (VIKING IV) with different impulses. The patients (56) underwent cochlear implantations(CI) (28), acoustic tumor removals (AN) (via different approaches)(19), microvascular decompressions (MVD)9). They had previously various degree of vertigo (DHI). The follow-up was 2 years. Results: VEMP recordings could only successfully be performed intraoperatively when they could be preoperatively elicited. A preservation of VEMP was related to a decrease in vertigo after the operation (AN/MVD). A postoperative loss of VEMP was accompanied by long-term instability, enhanced in the dark and on fast movements and in elderly (AN/CI). Conclusions: VEMP can be reliably recorded in this way. They can also be recorded in deaf patients and originate from the otolith organs (saccule). They provide additional helpful information for the surgeon in otoneurosurgery about the function of the inferior branch of the vestibular nerve (AN/MVD) and about the otolithic part of the labyrinth (CI). Loss of VEMP require long-standing vestibular rehabilitation, particularly in the elderly.

Superatentorial intracerebral hemorrhage following infratentorial surgery

Supratentorial hematoma following infratentorial surgery is rare. We present two such patients with remote site supratentorial hematoma after posterior fossa surgery. In one patient, a supratentorial hematoma developed following surgery for an acoustic tumor. The supratentorial hematoma was located near where a supratentorial meningioma was excised five days before. No hematoma was seen on the immediate postoperative CT scan. In another patient there were two tumors, one in the pons and the other in the basal ganglia. This patient developed a basal ganglia hematoma following brain stem surgery. In both the patients, hematological profile revealed a coagulation abnormality following the posterior fossa surgery. Our first case stabilized conservative management, whereas the second required surgical evacuation of the hematoma. The differential diagnosis of declining level of conciousness after posterior fossa surgery must include supratentorial intracerebral hemorrhage and CT scan of the head is the diagnostic test of choice.

Commentary

Dr. Buchheit was well known for his expertise in dealing with acoustic tumors during his active career. This review thoroughly defines the outcomes expected of surgery for acoustic neuromas by the best surgeons currently involved. Cure of the tumor is the rule. The mortality rate is extremely low, but not zero. Cranial nerves are usually preserved, and satisfactory facial function can be obtained in almost all patients with smaller tumors. Hearing preservation data are still inadequate to make predictions for individual patients. This study adds to the significant number of patients reported from several institutions around the world with similar outcomes for surgery. There is now a solid database against which surgeons can assess their individual results and against which the outcomes for observation and radiation can be compared.

感音難聴の画像診断‐ＭＲＩとＣＴ‐

Image diagnosis of sensorineural hearing loss was discussed with the presentation of examples of magnetic resonance imaging (MRI) and computed tomography (CT). MRI and CT of acoustic tumor, congenital perilymphatic fistula, brain stem infarction in the region of the anterior inferior cerebellar artery, inner ear hemorrhage, congenital ipsilateral profound hearing loss or sudden sensorineural hearing loss associated with inner ear anomaly, large vestibular aqueduct syndrome, superior canal dehiscent syndrome, large internal auditory canal syndrome, cochlear otosclerosis, and idiopathic low cerebrospinal fluid pressure syndrome were presented. In large vestibular aqueduct syndrome, superior canal dehiscent syndrome and large internal auditory canal syndrome, air-bone gap exist. As the explanation of the air-bone gap, we propose “three windows” model when there is a wide non-osseous communication route between the inner ear and the cerebrospinal fluid.

6. 巨大聴神経腫瘍に対する手術(A1 難しい脳腫瘍手術への挑戦)

6. 巨大聴神経腫瘍に対する手術(A1 難しい脳腫瘍手術への挑戦)

Facial F wave recording: a novel and effective technique for extra- and intraoperative diagnosis of facial nerve function in acoustic tumor disease

To investigate the diagnostic yield of facial F wave recording in patients with acoustic neurinomas intraoperatively and extraoperatively. Study design and setting Prospective study, comparative evaluation of facial F waves, transcranial magnetic stimulation of the facial motor cortex, blink reflex, and intraoperative online electromyographic activity. The study was performed in the neurosurgical department of a university hospital. Extraoperatively, only F wave latencies were closely correlated to tumor diameter as an independent variable. Intraoperatively, loss of F waves was specific for the development of a severe to total facial paresis postoperatively. A transient loss of F waves heralds an imminent danger of severe facial dysfunction. Facial F wave recording provides valuable information on the functional status of the nerve intra- and extraoperatively. Facial F wave recording should be used as a standard electrodiagnostic technique in addition to transcranial magnetic stimulation and blink reflex recording. It seems particularly useful for intraoperative facial nerve monitoring.

Detection of Viral DNA in the Endolymphatic Sac in Ménière’s Disease by in situ Hybridization

The main purpose of this study is to search for a viral etiology in Ménière’s disease by examining the presence or absence of herpes family virus DNA in the endolymphatic sac (ES) using the in situ hybridization method. This was a prospective study with the ES from 10 patients with Ménière’s disease and from 7 control cases without any pre-mortem ear diseases except a case of acoustic tumor. These 10 patients underwent the ES surgery. The presence of herpes family virus DNA, such as herpes simplex virus types 1 and 2 (HSV1&2), varicella-zoster virus (VZV), Epstein-Barr virus (EBV) and human cytomegalovirus (CMV), was examined using the in situ hybridization method. Serum antibody titers against these viruses just before the ES surgery were studied in these patients. Of the 10 specimens from the patients with Ménière’s disease, 7 were positive for VZV, 4 for EBV, 1 for CMV and none for HSV1&2, although the serum antibody titers against these viruses did not show any significant elevation in these patients just before the ES surgery. This result suggests that the viral DNA in the ES is inactive and is present in a latent form. From the statistical analysis, it can be postulated that VZV infection in early childhood may reach the ES and play a role in the pathogenesis of Ménière’s disease (p = 0.0235). The double infection with both VZV and EBV tended to be another candidate for the pathogenesis of Ménière’s disease (p = 0.0557).

Plug pattern optimization for gamma knife radiosurgery treatment planning

Purpose: To develop a novel dose optimization algorithm for improving the sparing of critical structures during gamma knife radiosurgery by shaping the plug pattern of each individual shot. Method and Materials: We first use a geometric information (medial axis) aided guided evolutionary simulated annealing (GESA) optimization algorithm to determine the number of shots and isocenter location, size, and weight of each shot. Then we create a plug quality score system that checks the dose contribution to the volume of interest by each plug in the treatment plan. A positive score implies that the corresponding source could be open to improve tumor coverage, whereas a negative score means the source could be blocked for the purpose of sparing normal and critical structures. The plug pattern is then optimized via the GESA algorithm that is integrated with this score system. Weight and position of each shot are also tuned in this procedure. Results: An acoustic tumor case is used to evaluate our algorithm. Compared to the treatment plan generated without plug patterns, adding an optimized plug pattern into the treatment planning process boosts tumor coverage index from 95.1% to 97.2%, reduces RTOG conformity index from 1.279 to 1.167, lowers Paddick’s index from 1.34 to 1.20, and trims the critical structure receiving more than 30% maximum dose from 16 mm 3 to 6 mm 3. Conclusions: Automated GESA-based plug pattern optimization of gamma knife radiosurgery frees the treatment planning team from the manual forward planning procedure and provides an optimal treatment plan.

Acoustic tensor tympani response and vestibular-evoked myogenic potential.

To investigate the acoustic response properties and the vestibular-evoked myogenic potential (VEMP) in various lesions. Retrospective study of the clinical records of patients. Neurotological tests including acoustic response and VEMP were performed and analyzed in 62 patients with facial palsy, otosclerosis, ossicular chain interruption, sensorineural hearing loss, or acoustic tumor. Inverted acoustic responses were observed in 25 of 38 (65.8%) patients with facial palsy, in 5 of 6 (83.3%) patients with acoustic tumor, and in all patients with otosclerosis, ossicular chain interruption, or sensorineural hearing loss. These inverted responses were obtained only when ipsilateral stimulation was used. The thresholds of the inverted responses were statistically significantly higher than those of the normal response. The vibration of the eardrum is thought to stimulate the ipsilateral trigeminal nerve, leading to contraction of the tensor tympani muscle. The stapedius response had an inhibitory effect on the inverted response. Vibration of the stapes footplate (which requires a normal middle ear conduction system) is necessary to induce the VEMP, whereas the functioning of the facial and cochlear nerves is independent of the VEMP response.

Cost-effective diagnosis of acoustic neuromas: a philosophical, macroeconomic, and technological decision.

Our goals were to define the most sensitive techniques of acoustic neuroma diagnosis, to examine their relative costs, and to propose diagnostic modality selection given the rarity of acoustic neuroma incidence and given the other costs that society faces in more commonly encountered diseases. We conducted a MEDLINE search of the English language from 1966 to 2001 using the following keywords: acoustic neuroma, acoustic tumor, vestibular schwannoma, diagnosis, cost effectiveness, MRI, auditory brainstem response, brainstem audiometric evoked response, incidence, and prevalence. Although magnetic resonance imaging with gadolinium remains the most sensitive diagnostic modality in the discovery of acoustic neuromas, its cost may be prohibitive for some societies. Which modality to use in acoustic neuroma diagnosis is just as much a philosophical and macroeconomic question as a technological one. The cost of a timely diagnosis of acoustic neuromas must be weighed against using resources for other, more pressing, health concerns.

Auditory brainstem response testing in acoustic neuroma diagnosis

In the past year, there was a lack of published papers on using auditory brainstem responses for acoustic tumor diagnosis. This lack is probably caused by the large number of published studies demonstrating that standard auditory brainstem response measures frequently fail to detect small (≤ 1 cm) a

Acoustic neuroma management: an evidence-based medicine approach.

Partisan claims supporting the use of microsurgical resection, radiologic surveillance, and radiosurgery in acoustic neuroma management appear widely in the published literature. However, the strength of the evidence supporting these claims has not been assessed, and the management of acoustic tumors continues to be controversial. The English-language medical literature for the past 23 years was searched for articles dealing with outcomes after acoustic neuroma management. The quality of evidence in each article was classified according to the categories of evidence as defined by a standard appraisal instrument for clinical guidelines. The search produced 111 articles reporting outcomes after acoustic neuroma management. From the 111 studies, 78 (70.3%) concerned surgery, 20 (18%) concerned radiosurgery, 9 (8.1%) concerned radiologic surveillance, and 4 (3.6%) compared different methods of management. From these studies, 95 (85.6%) represented Type III evidence, 6 (5.4%) represented Type IV evidence, and in 10 (9%) a clear-cut definition between Type III and Type IV could not be made. No study was supported by Type I or Type II evidence. The evidence supporting the various methods of acoustic neuroma management is of low quality (Type III or Type IV evidence). Well-designed comparisons between treatment methods do not exist, and therefore claims by clinicians favoring a particular treatment are unfounded. Better quality of evidence from large, well-designed, randomized clinical trials should now be undertaken at the points of clinical equipoise to address the true merits of each modality of acoustic neuroma management.

Acoustic Neuromas.

Patients with acoustic neuromas have several treatment options that include observation, surgical resection, stereotactic radiosurgery, and fractionated radiotherapy. Resection is indicated for patients with larger tumors that have caused major neurologic deficits from brain compression. Surgeons perform stereotactic radiosurgery as the main alternative to acoustic tumor resection with the goals of preserved neurologic function and prevention of tumor growth. The long-term outcomes of radiosurgery, particularly with gamma knife technique, have proven its role in the primary or adjuvant management of this disease. Radiotherapy can be offered to selected patients with larger tumors in whom radiosurgery may not be feasible. Patients with neurofibromatosis type-2 pose specific challenges, particularly in regard to preservation of hearing and other cranial nerve function. The primary clinical issues include avoiding tumor-related or treatment-related mortality, prevention of further tumor-related neurologic disability, minimizing treatment risks such as spinal fluid leakage, infections, or cardiopulmonary complications, maintaining regional cranial nerve function (facial, trigeminal, cochlear, and glossopharyngeal/vagal), avoiding hydrocephalus, maintaining quality of life and employment, and reducing cost. All treatment choices should strive to meet all of these goals.

Intratympanic ciprofloxacin and the human labyrinthine sampling model.

The aim of the study was to investigate the potential absorption of intratympanic ciprofloxacin through the human round window membrane. A prospective study. Ciprofloxacin was instilled into the middle ear of 10 patients undergoing acoustic tumor removal. The lateral semicircular canal and vestibule were subsequently opened and, using a microsyringe, labyrinthine fluid was aspirated. A sample each of serum and cerebrospinal fluid was also drawn. Into each middle ear, 0.5 mL ciprofloxacin (0.3%) was instilled. The time interval between the ciprofloxacin application to the round window membrane and sampling of labyrinthine fluid and plasma ranged from 9 to 120 minutes. There was no measurable ciprofloxacin in the labyrinthine fluid, cerebrospinal fluid, or serum of 10 patients. The lack of measurable absorption of intratympanic ciprofloxacin into the inner ear indicates that the chance of ototoxicity when ciprofloxacin is used clinically, even in the presence of a tympanic membrane perforation, is low.

多彩な合併症を伴ったｐａｔｕｌｏｕｓ ｃａｎａｌ例

A case of bilateral dilatation of the internal auditory canal without acoustic tumors, which was the so-called patulous internal auditory canal, is reported. The patient was a 12-year-old boy with bilateral sensorineural hearing loss, canal paresis in the left ear, anal atresia, epilepsy, mental retardation, and A-V block.Radiographs showed that the maximum diameter of the internal auditory canal was 12.8 mm on the left and 16.3 mm on the right. CT and MRI showed no evidence of an intracanalicular mass. Diffusion-weighted imaging was useful for a definitive diagnosis. No epidermoid cyst was present in the internal auditory canal.