Paired MRIs demonstrating effect of Gamma Knife on acoustic neuroma.
Figure 1: (Left) Coronal MRI scan with contrast demonstrates a large acoustic neuroma in a 38-year-old patient. (Right) A second coronal MRI one day after microsurgery, demonstrating complete resection with no complications and complete preservation of the facial nerve.

Specialists at the Center for Cranial Base Surgery at Penn Medicine are treating acoustic neuromas (vestibular schwannomas) with  advanced modalities, including sophisticated microsurgery with and without endoscope assistance and precision stereotactic radiosurgery (Gamma Knife® Perfexion[TM] and CyberKnife). The Center is comprised of cranial base neurosurgeons, otorhinolaryngologists and radiation oncologists who together develop comprehensive treatment plans for these complex tumors.

Acoustic neuromas are benign tumors that generally arise inside the internal auditory canal, a bony passage shared by the seventh (facial) and eight (auditory) cranial nerves. Expanding in a confined region of the skull, these indolent tumors can cause pressure on both nerves, resulting in unilateral hearing loss, vertigo, tinnitus, headaches and balance problems.

The objectives for neuroma treatment are maintenance of quality of life, complete removal or stabilization of tumor growth, preservation of hearing and preservation of facial nerve function (e.g., a normal smile). Factors influencing the decision for desired procedure include patient age, size of tumor, health status, risk tolerance and desired outcome.

Small to medium-sized tumors (< 2.5cm) can be treated with either surgical resection or Gamma Knife Perfexion radiosurgery with excellent results. Surgical resection has the advantage of complete removal of the tumor with little likelihood of recurrence, and remains the gold standard for benign tumors. However, surgery has a higher risk of complications than Gamma Knife radiosurgery.

By contrast to surgery, Gamma Knife controls (rather than removes) brain tumors, halting their growth with close to 200 beams of targeted gamma ray energy. The benefits of Gamma Knife include a low side effect profile and high quality of life after the procedure. Unfortunately, a small percentage of tumors can continue to grow after radiosurgery.

Because microsurgical resection is the best option for larger tumors (>2.5cm), the cranial base team at Penn Medicine uses three microsurgical approaches. The retrosigmoid approach is the most versatile, as it allows both small and large tumors to be removed and provides the ability to preserve hearing. The translabyrinthine approach does not require significant brain retraction and is also quite versatile, but is only for patients in whom hearing cannot be preserved. The middle fossa approach is used only for small tumors confined to the internal acoustic canal.

In addition to conventional surgical approaches, John Y. K. Lee, MD, of Penn Neurosurgery, has pioneered the use of the endoscope in the cerebellopontine angle to provide angled views and minimally invasive options.

Case Study 1

Mr. M, a 38-year-old man, was referred to Penn Neurosurgery with right-sided hearing loss, tinnitus and progressive gait ataxia. An MRI revealed a large acoustic neuroma measuring 3.4 cm anteroposteriorly, and 3.0 cm superoinferiorly with significant brainstem compression (Figure 1). Because of the tumor’s large size, Mr. M underwent retrosigmoid craniotomy. Both microscopy and endoscopy were used to obtain an optimal result. The tumor was completely resected; the facial nerve was anatomically preserved, and his gait improved. By his three-month visit, Mr. M had normal facial function and had returned to work without any restrictions. He has remained well at several years follow-up.

Case Study 2

Paired MRIs demonstrating before/after for acoustic neuroma.
Figure 2: (Left) Axial MRI scan with contrast demonstrates right acoustic neuroma at the time fo Gamma Knife radiosurgery. (Right) A second MRI scan five years post-Gamma Knife radiosurgery. This patient had both preservation of functional hearing and no change in facial function.
Mrs. G, a 67-year-old woman, was referred to the Center for Cranial Base Surgery at Penn Medicine after her personal physician confirmed a moderate loss of hearing in her right ear. An MRI at Penn showed a tumor at the right auditory canal consistent with an acoustic neuroma (Figure 2, left) with a total volume of 3 cc. Mrs. G chose the less invasive option of Gamma Knife surgery for her therapy. Her Gamma Knife treatment involved a single outpatient session, during which she received a 12 Gy prescription to the 50% isodose line. Her recovery was unremarkable and she has since enjoyed an improved quality of life without side effects. Five years after her treatment (Figure 2, right), Mrs. G retains moderate hearing in her right ear and normal facial function.


Penn Neurosurgery
Hospital of the University of Pennsylvania
3400 Spruce Street
3rd Floor, Silverstein Building
Philadelphia, PA 19104

Pennsylvania Hospital
Washington Square West Building
235 South 8th Street
Philadelphia, PA 19106

Department of Otorhinolaryngology - Head and Neck Surgery

Perelman Center for Advanced Medicine
South Pavilion, 3rd Floor
3400 Civic Center Boulevard
Philadelphia, PA 19104

Penn Medicine Washington Square
18th Floor,
800 Walnut Street
Philadelphia, PA 19107

Published on: November 6, 2013






About the Penn Center for Cranial Base Surgery

Penn Medicine's Center for Cranial Base Surgery is the Philadelphia region's premier center for the evaluation and treatment of tumors of the head, neck and face, as well as other complex skull base disorders. Led by a team of specialists from various disciplines, the Center for Cranial Base Surgery is one of the few centers in the nation dedicated to the evaluation and treatment of benign and malignant tumors of the skull base.

The Center for Cranial Base Surgery has a rich history as a leader in the treatment of these disorders through the use of modern techniques such as transoral robotic surgery (TORS), trans nasal surgery, 3-D navigation planning, microscopic and laser techniques, and ongoing research studies and clinical trials. With the advent of these procedures, many of these tumors that were previously inaccessible can now be successfully treated.

Penn Faculty Team

Michelle Alonso-Basanta, MD, PhD

Chief, Central Nervous System Section

Vice Chair, Clinical Division

Associate Professor of Radiation Oncology at the Hospital of the University of Pennsylvania

Douglas Bigelow, MD

Co-Director, Center for Cranial Base Surgery

Director, Division of Otology/Neurotology

Associate Professor of Otorhinolaryngology: Head and Neck Surgery at the Hospital of the University of Pennsylvania

M. Sean Grady, MD

Chairman, Department of Neurosurgery

Charles Harrison Frazier Professor of Neurosurgery

James D. Kolker, MD

Chief, Section of Radiation Oncology, Pennsylvania Hospital

Medical Director, CyberKnife

Clinical Associate Professor of Radiation Oncology

John Y.K. Lee, MD, MSCE

Medical Director, Gamma Knife Center

Associate Professor of Neurosurgery at the Pennsylvania Hospital

Bert W. O'Malley, Jr., MD

Associate Vice President, Physician Network Development

Chair, Department of Otorhinolaryngology - Head and Neck Surgery

Co-Director, Head and Neck Cancer Center

Gabriel Tucker Professor of Otorhinolaryngology: Head and Neck Surgery

Suneel N. Nagda, MD

Associate Professor of Clinical Radiation Oncology

Michael J. Ruckenstein, MD, MSc, FACS

Director, Implantable Hearing Devices Program

Director, Residency Training and Education

Vice Chairman, Department of Otolaryngology

Professor of Otorhinolaryngology: Head and Neck Surgery at the Hospital of the University of Pennsylvania

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