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Matthew L. Carlson, Dusica Babovic-Vuksanovic, Ludwine Messiaen, Bernd W. Scheithauer, Brian A. Neff and Michael J. Link

Neurofibromatosis Type 2 (NF2) is a rare autosomal dominant disorder characterized by the development of benign tumors of the peripheral nervous system and the CNS, including schwannomas, meningiomas, and ependymomas. The gene responsible for the development of NF2 acts as a tumor suppressor gene. Stereotactic radiotherapy (SRT) or single-fraction stereotactic radiosurgery has been increasingly used in the past decades to treat benign tumors in patients with NF2. These radiotherapy methods are less invasive and can be potentially used to treat multiple tumors in a single session. The risk of inducing malignancy is unclear. Few reports exist of malignant peripheral nerve sheath tumors, meningiomas, or ependymomas occurring after SRT or stereotactic radiosurgery in patients with NF2. The authors present the first documented case of rhabdomyosarcoma following SRT for multiple NF2-associated schwannomas. Compared with patients with sporadic tumors, NF2 patients having a germline tumor suppressor gene defect may be more prone to secondary malignancies after treatment involving radiation therapy.

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Matthew L. Carlson, Kathryn M. Van Abel, William R. Schmitt, Colin L. W. Driscoll, Brian A. Neff, John I. Lane and Michael J. Link

Object

The authors describe the unique occurrence of nodular enhancement within the fundus of the internal auditory canal (IAC) lateral to the preoperative radiological tumor margin following gross-total vestibular schwannoma (VS) resection.

Methods

The nature of the study was a retrospective chart review of records. The authors reviewed the cases of all patients who underwent microsurgical resection of a VS between January 2000 and January 2010 at a single tertiary referral center. Patients with incomplete resection, neurofibromatosis Type 2, and those with fewer than 2 postoperative MR images available for review were excluded.

Postsurgical patients with IAC enhancement located lateral to the preoperative imaging–delineated tumor margin were identified. Lesion morphology was characterized on serial MR imaging studies. Clinical follow-up and outcomes were recorded.

Results

Over the past decade, 350 patients underwent microsurgical VS resection. Of these, 16 patients met study criteria and were found to have postsurgical enhancement in the distal aspect of the IAC lateral to the imaging limits of the preoperative tumor margin on the first postoperative MR imaging study (37.5% women, median age 45 years). Initial MR imaging was performed at a mean of 3.1 months following surgery, and the mean radiological follow-up duration was 39.8 months (range 16.4–101.9 months). None of the 16 patients developed recurrence during the follow-up course.

Conclusions

In contrast to previous publications that have reported a high rate of recurrence in cases involving nodular enhancement within the original tumor bed, postoperative enhancement in the IAC lateral to the original tumor margin appears to carry much less risk for tumor recurrence. These findings may be helpful when counseling patients on the recommended frequency of postoperative follow-up imaging.

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William R. Schmitt, Jasper R. Daube, Matthew L. Carlson, Jayawant N. Mandrekar, Charles W. Beatty, Brian A. Neff, Colin L. Driscoll and Michael J. Link

Object

The goal of vestibular schwannoma surgery is tumor removal and preservation of neural function. Intraoperative facial nerve (FN) monitoring has emerged as the standard of care, but its role in predicting long-term facial function remains a matter of debate. The present report seeks to describe and critically assess the value of applying current at supramaximal levels in an effort to identify patients destined for permanent facial paralysis.

Methods

Over more than a decade, the protocol for stimulating and assessing the FN during vestibular schwannoma surgery at the authors' institution has consisted of applying pulsed constant-current stimulation at supramaximal levels proximally and distally following tumor resection to generate an amplitude ratio, which subtracted from 100% yields the degree to which the functional integrity of the FN “dropped off” intraoperatively. These data were prospectively collected and additional variables that might impact postoperative FN function were retrospectively reviewed from the medical record. Only patients with anatomically intact FNs and > 12 months of follow-up data were analyzed.

Results

There were 267 patients available for review. The average posterior fossa tumor diameter was 24 mm and the rate of long-term good (House-Brackmann Grade I–II) FN function was 84%. Univariate logistic regression analysis revealed that prior treatment, neurofibromatosis Type 2 status, tumor size, cerebellopontine angle extension, subjectively thinned FN at the time of operation, minimal stimulation threshold, percent dropoff by supramaximal stimulation (SMS), and postoperative FN function all correlated statistically (p < 0.05) with long-term FN function. When evaluating patients with significant FN weakness at the time of hospital discharge, only the percent dropoff by SMS remained a significant predictor of long-term FN function. However, the positive predictive value of SMS for long-term weakness is low, at 46%.

Conclusions

In a large cohort of patients, the authors found that interrogating intraoperative FN function with SMS is safe and technically simple. It is useful for predicting which patients will ultimately have good facial function, but is very limited in identifying patients destined for long-term facial weakness. This test may prove helpful in the future in tailoring less than gross-total tumor removal to limit postoperative facial weakness.

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Matthew L. Carlson, Jeffrey T. Jacob, Bruce E. Pollock, Brian A. Neff, Nicole M. Tombers, Colin L. W. Driscoll and Michael J. Link

Object

The goals of this retrospective cohort study were as follows: 1) to describe the long-term prevalence and timing of hearing deterioration following low-dose (12- to 13-Gy marginal dose) stereotactic radiosurgery (SRS) for vestibular schwannoma (VS); and 2) to identify clinical variables associated with long-term preservation of useful hearing following treatment.

Methods

Patients with serviceable hearing who underwent SRS for VS between 1997 and 2002 were studied. Data including radiosurgery treatment plans, tumor characteristics, pre- and posttreatment pure tone average, speech discrimination scores, and American Academy of Otolaryngology–Head and Neck Surgery hearing class were collected. Time to nonserviceable hearing was estimated using the Kaplan-Meier method. Univariate and multivariate associations with time to nonserviceable hearing were evaluated using Cox proportional hazards regression models.

Results

Forty-four patients met the study criteria and were included. The median duration of audiometric follow-up was 9.3 years. Thirty-six patients developed nonserviceable hearing at a mean of 4.2 years following SRS. The Kaplan-Meier estimated rates of serviceable hearing at 1, 3, 5, 7, and 10 years following SRS were 80%, 55%, 48%, 38%, and 23%, respectively. Multivariate analysis revealed that pretreatment ipsilateral pure tone average (p < 0.001) and tumor size (p = 0.009) were statistically significantly associated with time to nonserviceable hearing.

Conclusions

Durable hearing preservation a decade after low-dose SRS for VS occurs in less than one-fourth of patients. Variables including preoperative hearing capacity and tumor size may be used to predict hearing outcomes following treatment. These findings may assist in pretreatment risk disclosure. Furthermore, these data demonstrate the importance of long-term follow-up when reporting audiometric outcomes following SRS for VS.

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Michelle A. Holman, William R. Schmitt, Matthew L. Carlson, Colin L. W. Driscoll, Charles W. Beatty and Michael J. Link

Object

The aim in this study was to describe the clinical presentation, differential diagnosis, and risk for neurofibromatosis Type 2 (NF2) in pediatric patients presenting with cerebellopontine angle (CPA) and internal auditory canal (IAC) tumors.

Methods

The authors conducted a retrospective study at a tertiary care academic referral center. All patients with an age ≤ 18 years who had presented with an extraaxial CPA or IAC tumor between 1987 and 2012 were included in the study cohort. Data regarding symptoms, diagnosis, tumor characteristics, and NF2 status were collected and analyzed.

Results

Sixty patients (55% female, 45% male) harboring 87 tumors were identified. The mean age at diagnosis was 12.8 years (median 14.0 years, range 0.9–18.9 years). Schwannomas were the most commonly identified lesions (57 of 87 tumors, including 52 vestibular, 3 facial, and 2 trigeminal schwannomas), followed by meningiomas (5 of 87) and epidermoid cysts (4 of 87). Six malignant tumors were diagnosed, including small-cell sarcoma, squamous cell carcinoma, malignant meningioma, atypical rhabdoid-teratoid tumor, endolymphatic sac tumor, and malignant ganglioglioma. Headache, followed by hearing loss and imbalance, was the most common presenting symptom, whereas dysphagia, otalgia, and facial pain were uncommon.

Neurofibromatosis Type 2 was diagnosed in 20 (61%) of 33 patients with vestibular schwannoma (VS), while the other 13 patients (39%) had sporadic tumors. Nineteen of the 20 patients with NF2 met the diagnostic criteria for that disorder on initial presentation, and 15 of them presented with bilateral VS. At the last follow-up, 19 of the 20 patients subsequently diagnosed with NF2 demonstrated bilateral VSs, whereas 1 patient with a unilateral VS and multiple other NF2-associated tumors has yet to demonstrate a contralateral VS to date. Only 1 patient presenting with an isolated unilateral VS and no family history of NF2 demonstrated a contralateral VS on subsequent radiological screening.

Conclusions

Cerebellopontine angle and IAC tumors in the pediatric population are rare. There are several noteworthy differences between the adult and pediatric populations harboring these lesions. While VS is the most common pathology in both age groups, the lesion was found in only 60% of the pediatric patients in the present study. Unlike in adults, VSs in the pediatric population were associated with NF2 in over one-half of all cases. The majority of pediatric patients with NF2 fulfilled the diagnostic criteria at initial presentation; however, approximately 7% of patients presenting with a seemingly sporadic (no family history of NF2) unilateral VS will meet the criteria for NF2 later in life. Finally, malignancies account for a significantly higher percentage (10%) of cases among pediatric patients. These findings underscore the importance of early screening and close radiological follow-up and may be helpful in patient counseling.

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Matthew L. Carlson, William R. Copeland III, Colin L. Driscoll, Michael J. Link, David S. Haynes, Reid C. Thompson, Kyle D. Weaver and George B. Wanna

Object

The goals of this study were to report the clinical presentation, radiographic findings, operative strategy, and outcomes among patients with temporal bone encephaloceles and cerebrospinal fluid fistulas (CSFFs) and to identify clinical variables associated with surgical outcome.

Methods

A retrospective case series including all patients who underwent a middle fossa craniotomy or combined mastoid–middle cranial fossa repair of encephalocele and/or CSFF between 2000 and 2012 was accrued from 2 tertiary academic referral centers.

Results

Eighty-nine consecutive surgeries (86 patients, 59.3% women) were included. The mean age at time of surgery was 52.3 years, and the left side was affected in 53.9% of cases. The mean delay between symptom onset and diagnosis was 35.4 months, and the most common presenting symptoms were hearing loss (92.1%) and persistent ipsilateral otorrhea (73.0%). Few reported a history of intracranial infection (6.7%) or seizures (2.2%).

Thirteen (14.6%) of 89 cases had a history of major head trauma, 23 (25.8%) were associated with chronic ear disease without prior operation, 17 (19.1%) occurred following tympanomastoidectomy, and 1 (1.1%) developed in a patient with a cerebral aqueduct cyst resulting in obstructive hydrocephalus. The remaining 35 cases (39.3%) were considered spontaneous. Among all patients, the mean body mass index (BMI) was 35.3 kg/m2, and 46.4% exhibited empty sella syndrome. Patients with spontaneous lesions were statistically significantly older (p = 0.007) and were more commonly female (p = 0.048) compared with those with nonspontaneous pathology. Additionally, those with spontaneous lesions had a greater BMI than those with nonspontaneous disease (p = 0.102), although this difference did not achieve statistical significance.

Thirty-two surgeries (36.0%) involved a middle fossa craniotomy alone, whereas 57 (64.0%) involved a combined mastoid–middle fossa repair. There were 7 recurrences (7.9%); 2 patients with recurrence developed meningitis. The use of artificial titanium mesh was statistically associated with the development of recurrent CSFF (p = 0.004), postoperative wound infection (p = 0.039), and meningitis (p = 0.014). Also notable, 6 of the 7 cases with recurrence had evidence of intracranial hypertension. When the 11 cases that involved using titanium mesh were excluded, 96.2% of patients whose lesions were reconstructed with an autologous multilayer repair had neither recurrent CSFF nor meningitis at the last follow-up.

Conclusions

Patients with temporal bone encephalocele and CSFF commonly present with persistent otorrhea and conductive hearing loss mimicking chronic middle ear disease, which likely contributes to a delay in diagnosis. There is a high prevalence of obesity among this patient population, which may play a role in the pathogenesis of primary and recurrent disease. A middle fossa craniotomy or a combined mastoid–middle fossa approach incorporating a multilayer autologous tissue technique is a safe and reliable method of repair that may be particularly useful for large or multifocal defects. Defect reconstruction using artificial titanium mesh should generally be avoided given increased risks of recurrence and postoperative meningitis.

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Jonathan A. Forbes, Matthew L. Carlson, Saniya S. Godil, Marc L. Bennett, George B. Wanna and Kyle D. Weaver

In this publication, video format is utilized to review the operative technique of retrosigmoid craniotomy for resection of acoustic neuroma with attempted hearing preservation. Steps of the operative procedure are reviewed and salient principles and technical nuances useful in minimizing complications and maximizing efficacy are discussed.

The video can be found here: http://youtu.be/PBE5rQ7B0Ls.

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Kathryn M. Van Abel, Matthew L. Carlson, Colin L. Driscoll, Brian A. Neff and Michael J. Link

Object

The authors' objective was 2-fold: 1) to compare outcomes of microsurgical resection for vestibular schwannoma (VS) between patients aged 70 years or older and patients younger than 70 years and 2) to test the hypothesis that symptomatic tumors in elderly patients represent a more aggressive variant of VS than those in younger adults, resulting in increased morbidity and a higher rate of recurrence after subtotal resection (STR).

Methods

A retrospective matched cohort study was conducted. Patients aged 70 years or older who had undergone microsurgical resection of VS were matched to adult patients younger than 70 years; the matching was performed on the basis of surgical approach, completeness of resection, and tumor size. Associations between clinical, radiographic, and surgical data and postoperative outcome were analyzed using conditional logistic regression.

Results

Twenty patients aged 70 years or older (mean age ± SD 75.9 ± 5.3, range 70–86 years) were identified and matched to a cohort of younger adult patients (mean age ± SD 55.7 ± 13.8, range 25–69 years). The mean tumor size in both groups was approximately 3 cm. Overall, the elderly patients had a poorer preoperative American Society of Anesthesiology physical status score (p = 0.038), were more likely to report imbalance (OR 9.61, p = 0.016), and more commonly exhibited compromised balance and coordination (OR 9.61, p = 0.016) than patients in the younger cohort.

There were no differences between the 2 cohorts in perioperative complications (p = 0.26) or facial nerve function (p > 0.5) at any time. The elderly patients were 13 times more likely to have long-term postoperative imbalance (OR 13.00, p = 0.013) than the younger patients. Overall, 9 tumors recurred among 32 patients undergoing STR; 6 of these patients underwent additional interventions (stereotactic radiosurgery in 5 patients and microsurgery in 1) and showed no evidence of tumor progression at the last follow-up. The median growth rate of the recurrent tumor in the 6 elderly patients was 4.8 mm/year (range 2.1–14.9 mm/year) and, in the 3 control patients, 2.2 mm/year (range 1.9–4.0 mm/year). Overall, the mortality data showed a trend toward statistical significance (p = 0.068) with a higher risk of death in the elderly.

Conclusions

As the number of elderly patients with VS increases, microsurgical resection will remain an important management option for these patients. Despite a poorer preoperative physical status in elderly patients, their morbidity profiles are similar to those in adult patients younger than 70 years. However, elderly patients may require longer convalescence due to prolonged postoperative imbalance. Not surprisingly, overall diminished functional reserve and advanced comorbidities may increase the mortality risk associated with surgical intervention in the elderly patients. Finally, there was a high risk of further tumor growth following STR in the elderly patients (6 [37.5%] of 16), underscoring the need for close postoperative radiological surveillance and consideration of early stereotactic radiosurgery for the tumor remnant following the STR.

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Matthew L. Carlson, Oystein Vesterli Tveiten, Colin L. Driscoll, Frederik K. Goplen, Brian A. Neff, Bruce E. Pollock, Nicole M. Tombers, Marina L. Castner, Monica K. Finnkirk, Erling Myrseth, Paal-Henning Pedersen, Morten Lund-Johansen and Michael J. Link

OBJECT

The optimal treatment for sporadic vestibular schwannoma (VS) is highly controversial. To date, the majority of studies comparing treatment modalities have focused on a narrow scope of technical outcomes including facial function, hearing status, and tumor control. Very few publications have investigated health-related quality of life (HRQOL) differences between individual treatment groups, and none have used a disease-specific HRQOL instrument.

METHODS

All patients with sporadic small- to medium-sized VSs who underwent primary microsurgery, stereotactic radiosurgery (SRS), or observation between 1998 and 2008 were identified. Subjects were surveyed via postal questionnaire using the 36-Item Short Form Health Survey (SF-36), the 10-item Patient-Reported Outcomes Measurement Information System short form (PROMIS-10), the Glasgow Benefit Inventory (GBI), and the Penn Acoustic Neuroma Quality-of-Life (PANQOL) scale. Additionally, a pool of general population adults was surveyed, providing a nontumor control group for comparison.

RESULTS

A total of 642 respondents were analyzed. The overall response rate for patients with VS was 79%, and the mean time interval between treatment and survey was 7.7 years. Using multivariate regression, there were no statistically significant differences between management groups with respect to the PROMIS-10 physical or mental health dimensions, the SF-36 Physical or Mental Component Summary scores, or the PANQOL general, anxiety, hearing, or energy subdomains. Patients who underwent SRS or observation reported a better total PANQOL score and higher PANQOL facial, balance, and pain subdomain scores than the microsurgical cohort (p < 0.02). The differences in scores between the nontumor control group and patients with VS were greater than differences observed between individual treatment groups for the majority of measures.

CONCLUSIONS

The differences in HRQOL outcomes following SRS, observation, and microsurgery for VS are small. Notably, the diagnosis of VS rather than treatment strategy most significantly impacts quality of life. Understanding that a large number of VSs do not grow following discovery, and that intervention does not confer a long-term HRQOL advantage, small- and medium-sized VS should be initially observed, while intervention should be reserved for patients with unequivocal tumor growth or intractable symptoms that are amenable to treatment. Future studies assessing HRQOL in VS patients should prioritize use of validated disease-specific measures, such as the PANQOL, given the significant limitations of generic instruments in distinguishing between treatment groups and tumor versus nontumor subjects.