Microsurgical Removal of Pediatric Skull Base Tumors Effective in Preserving Hearing, Facial Nerve Function

Newswise — The lateral skull base is that portion of the base of skull that is composed of the hearing and balance organs, in addition to vital neural and vascular components. Lesions of the lateral skull base present numerous challenges for the skull base surgeon. The intricacies of multiple neurovascular structures and their relationship to the components of the temporal bone make the lateral skull base a complex surgical field. Removal of even small lesions can result in deafness, facial nerve dysfunction and balance disorders. For the pediatric patient, the procedure holds higher risk due to the oft-advanced disease at presentation and lower rates of cranial nerve preservation when compared to adult patients. The consequence for the child can be devastating; loss of facial nerve function and hearing loss is a lifetime problem with a significant impact on quality of life. Therefore, as in adult patients, current approaches to treatment emphasize both complete tumor removal and preservation of normal anatomy and function.

Technological developments in perioperative care and surgical approaches and techniques have improved skull base surgery outcomes in recent years. The integration of magnetic resonance imaging, advances in microsurgical technique and cranial nerve monitoring into the standard of diagnostic and surgical care has created greater opportunity for successful surgical treatment. As a result of these advances, patients with lateral skull base lesions undergoing surgical treatment can reasonably expect a fair probability of good post-operative facial nerve function as well as an improved probability of hearing preservation in select cases, while facing a low likelihood of serious complications and death.

However, few reports exist regarding the application of lateral skull base procedures to pediatric patients. Many believe the child's anatomy, coupled with the nature of the tumors, precludes full benefits these technological and procedural advances in skull-based surgery. As a result, previous management strategies have often included a watchful waiting policy.

Researchers have performed a 10-year retrospective evaluation of all pediatric patients who have undergone surgical treatment for one or more skull base tumors at the House Ear Clinic to determine the outcomes of therapy in this patient population. The authors of "Neurotologic Skull Base Surgery in Pediatric Patients," are Calhoun D. Cunningham III MD, Rick A. Friedman MD PhD, Derald E. Brackmann MD, William E. Hitselberger MD, and Harrison W. Lin, all with the House Ear Clinic and House Ear Institute, Los Angeles, CA. Their findings are being presented at the annual meeting of the American Neurotology Society http://www.otology-neurotology.org/ANS/ans-mai being held April 30-May 3, 2004, at the JW Marriott Desert Ridge Resort & Spa, Phoenix, AZ.

Methodology: All pediatric patients 18 years or younger undergoing surgery for lateral skull base lesions at the House Ear Clinic between July 1992 and September 1993 were reviewed. A total of 115 lateral skull base procedures were performed on 89 patients. Twenty-one patients underwent more than one skull base procedure and each of these surgeries is reported separately. Seventeen patients underwent bilateral procedures, three patients underwent three separate procedures and one patient underwent four separate skull base surgeries. There were 70 middle fossa, 40 translabyrinthine, two transcochlear, two infratemporal fossa, and one retrosigmoid approach performed. There were 61 male and 54 female procedures (44 male and 45 female patients). The mean age at the time of surgery was 13.8 years and ranged from 7 to 18 years. Sixty-five patients (73 percent) were diagnosed with Neurofibromatosis Type-2 (NF-2), a condition with few cutaneous manifestations, and consists primarily of bilateral (less often, unilateral) acoustic neuromas, causing deafness, often accompanied by other intracranial and paraspinal neoplasms. These patients underwent a total of 91 procedures (24 procedures in non-NF-2 patients). All patients who underwent more than one skull base surgery had a diagnosis of NF-2. Preoperative data including presenting symptoms, tumor size, facial nerve function, and audiometric studies including four-frequency (500, 1000, 2000 and 3000 Hz) pure-tone average (PTA) and speech discrimination scores (SDS) were prospectively recorded and obtained from a computerized database. Surgical time, amount of tumor removal, tumor size, tumor type, blood loss, facial nerve status, and complications were recorded at the time of surgery in all patients.

Postoperative outcomes including length of hospital stay, complications and management, long-term facial nerve function and postoperative PTA and SDS at 14-day follow-up were obtained retrospectively from data sheets and in some cases with follow-up letters to the patient. Pure-tone bone conduction thresholds were used in some cases in computing the postoperative PTA because occasionally a hemotympanum was present at the two-week postoperative evaluation.

Results: The majority of tumors in this series were vestibular schwannomas, and 65 patients were diagnosed with Neurofibromatosis Type-2. Complete tumor removal was accomplished in the majority of cases (97 percent) with good preservation of facial nerve function in 80 percent of patients. In patients undergoing middle fossa surgery for hearing preservation, measurable hearing was preserved in 61.4 percent of cases. The incidence of complications was low.

Conclusions: Current surgical therapies are well-accepted forms of treatment for skull base tumors, but there have been very little written about surgical therapy in pediatric patients. The few studies that have addressed this patient population have reported worse outcomes in children when compared to adults. This is the fist study of a large series of patients less than or equal to age 18 that demonstrates similar successful results in children as well as adults.

There are several options for the treatment of pediatric skull base lesions. The three main options are observation with serial imaging to follow tumor size, stereotactic radiotherapy, and Surgery. Oftenphysicians probably choose observation or radiotherapy for fear of the morbidity of neurologic deficits that occurred in the past. The authors suggest these findings demonstrate that children with tumors in this region can be successfully treated with good functional outcomes using microsurgical approaches. Furthermore, in NF-2, they demonstrate the hearing can be preserved in a number of cases with complete removal of their tumors.

For the parent of a child with a skull-based lesion, this research is important. Tumors or lesion which once likely left the patient with hearing loss or facial nerve weakness, can be successful treated, with good preservation of function and minimal morbidity, using current microsurgical techniques that are used in adult patients.