Otology & Neurotology
Planned Subtotal Resection and Stereotactic Radiotherapy for Acoustic Neuroma
Collaborators: Nikolas Blevins, MD and Robert K. Jackler, MD
The advent of stereotactic radiosurgery has provided the clinician with a non-surgical option to control the growth of acoustic tumors. With the development of the Cyberknife linear accelerator system, Stanford has long been a pioneer in the non-surgical management of skull base disease. Despite considerable experience with small acoustic tumors, the role of radiosurgery into the treatment of large tumors remains to be fully defined. The potentially synergistic effect of combined microsurgical resection and stereotactic radiotherapy could offer effective new options to individuals who remain at most risk given conventional treatment.
The Stanford Department of Otolaryngology in collaboration with the departments of Neurosurgery and Radiation Oncology, is leading a prospective multicenter trial to assess the efficacy of managing large acoustic neuromas (over 3 cm) with a combination of planned subtotal resection followed by stereotactic radiosurgery. Patients enrolled in the protocol will undergo planned subtotal resection avoiding potentially injurious dissection of the facial nerve from the tumor capsule. Patients will be followed with serial MRI scans, and will receive stereotactic radiation to the tumor remnant if growth is detected.
The prospective nature of this study will provide valuable data towards establishing optimal treatment of advanced disease, while minimizing the risk of postoperative facial nerve dysfunction.
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1. Planned subtotal resection of an acoustic neuroma
2. The Stanford Cyberknife.
The Use of Stacked ABR for the Assessment of Hearing Preservation in Acoustic Neuroma Resection
Patients with small acoustic neuromas and good hearing are faced with a choice of treatment options. Whether they choose to undergo microsurgical resection or stereotactic radiotherapy (such as with Cyberknife) can be largely influenced by the likelihood of hearing preservation. The short-term rates of hearing preservation with stereotactic radiation are excellent, but given the persistence of tumor and possible long-term neurovascular changes, hearing levels may deteriorate with time. Microsurgery in contrast, often places additional risks to hearing in the short term. However, the expectation for maintaining hearing that is present post-operatively is quite favorable. Unfortunately, there is a current lack of preoperative predictors of which patients are more likely to retain hearing through a surgical procedure.
The Stanford Departments of Otolaryngology and Audiology are engaged in a prospective clinical trial to assess innovative of electrophysiologic testing to predict the success of hearing-preservation attempts. The study applies highly sensitive auditory brainstem response techniques (“stacked ABR”) that may be an accurate predictor of the potential for an involved cochlear nerve to withstand surgical manipulation and tumor extraction.
The development of such non-invasive preoperative predictors will substantively assist with patient counseling and treatment planning in patients with acoustic neuromas. Given this additional information, patients and their clinicians may make better-informed decisions about the pursuit of treatment options.
Non-invasive Diagnosis of Cholesteatoma using High-Resolution Diffusion-Weighted MRI Sequences
The Department of Otolaryngology, in conjunction with the Department of Radiology, is engaged in a prospective study to establish the efficacy of innovative MRI techniques in the diagnosis of cholesteatoma. Standard diffusion-weighted MRI is capable of detecting intratemporal squamous epithelium. However, it is subotipmal in its anatomic resolution and is subject to significant artifacts, both of which limit its clinical utility.
Our protocol involves the use of new signal processing techniques (SENSE-DWI). The resulting improved images have the potential to make MRI clinically useful in treatment planning for patients with possible occult cholesteatoma. Patients in whom a second-look procedure is contemplated may benefit greatly from this non-invasive imaging modality.
Innovations in Cochlear Implant Technology
In 1964, the first human multichannel cochlear implant was placed at Stanford. The Department of Otolaryngology continues this long history of innovation in the development and application of inner ear prostheses. Related basic science projects include the application of stem-cells for inner ear regeneration, computational modeling of inner ear function, and inner ear microendoscopy for therapeutics and inner ear microrobotics.
The LPCH/Stanford Cochlear Implant Center is actively involved in clinical trials for cochlear implants. We are a center for the clinical trial of the Nucleus Electrical-Acoustic Hybrid implant. These devices offer the potential benefits of cochlear implantation to the vast number of individuals who suffer from high frequency hearing loss, since residual acoustic hearing in the lower frequencies can be maintained.
