Carlson, Matthew L.

Objective: The goal of the present study was to assess the sound quality of a cochlear implant for single-sided deaf (SSD) patients fit with a cochlear implant (CI). Background: One of the fundamental, unanswered questions in CI research is “what does an implant sound like?” Conventional CI patients must use the memory of a clean signal, often decades old, to judge the sound quality of their CIs. In contrast, SSD-CI patients can rate the similarity of a clean signal presented to the CI ear and candidate, CI-like signals presented to the ear with normal hearing. Methods: For Experiment 1 four types of stimuli were created for presentation to the normal hearing ear: noise vocoded signals, sine vocoded signals, frequency shifted, sine vocoded signals and band-pass filtered, natural speech signals. Listeners rated the similarity of these signals to unmodified signals sent to the CI on a scale of 0 to 10 with 10 being a complete match to the CI signal. For Experiment 2 multitrack signal mixing was used to create natural speech signals that varied along multiple dimensions. Results: In Experiment 1 for eight adult SSD-CI listeners, the best median similarity rating to the sound of the CI for noise vocoded signals was 1.9; for sine vocoded signals 2.9; for frequency upshifted signals, 1.9; and for band pass filtered signals, 5.5. In Experiment 2 for three young listeners, combinations of band pass filtering and spectral smearing lead to ratings of 10. Conclusion: The sound quality of noise and sine vocoders does not generally correspond to the sound quality of cochlear implants fit to SSD patients. Our preliminary conclusion is that natural speech signals that have been muffled to one degree or another by band pass filtering and/or spectral smearing provide a close, but incomplete, match to CI sound quality for some patients.

Background: The first description of the voluntary motor function of the facial nerve and separate sensory-motor contributions of the trigeminal nerve is most commonly attributed to Charles Bell. However, a review of the original scientific accounts and subsequent historical publications question the validity of this credit. The objective of the present historical analysis is to clarify the contributions of Herbert Mayo toward discovering the functions of the fifth and seventh cranial nerves and to raise awareness of this historical controversy within the medical literature. Methods: Review of Charles Bell's and Herbert Mayo's original dissertations published between 1821 and 1823, and subsequent reports relevant to these primary works. Results: Bell's submissions to the Royal Society of London in 1821 and 1822 describe the seventh nerve as the “respiratory nerve of the face” responsible for involuntary coordination of facial movement with the organs of respiration. Separately, Bell states that the fifth nerve is responsible for sensibility and voluntary movement of the facial muscles. In these accounts, Bell only peripherally alludes to the motor function of the seventh nerve and often comments inaccurately on fifth and seventh cranial nerve innervation. In contrast, in 1822 and 1823, Herbert Mayo first accurately and unequivocally defined the voluntary motor function of the facial nerve and sensory-motor function of the trigeminal nerve on the basis of his detailed experiments. The ultimate transfer of acknowledgment to Bell was rooted in surreptitious reworking of Bell's original dissertations and personal attacks against Mayo rather than arguments of scientific merit. Conclusion: Several notable clinicians and anatomists have contributed to our current understanding of the anatomy and physiology of the facial and trigeminal nerves, including Charles Bell; however, Herbert Mayo should be remembered for first providing a more accurate and clear description of their separate functions.

Abstract Dr Albert L. Rhoton Jr became the focal point of neurosurgery's evolution in understanding the intricate and complex microanatomy of the human brain over the last 4 decades. His pioneering work on cadaveric specimens proved to be a pivotal endeavor in the pursuit to better understand the complex microsurgical anatomy of cranial surgery. This paper details his early career at the Mayo Clinic in Rochester, Minnesota. A comprehensive review and synthesis of data acquired from the institutional historical archives including the Annual Reports to the Executive Committee, the Reports to the Board of Directors, the MAYOVOX Newsletter, the illustration archives of the Mayo Clinic Division of Creative Media, staff biographies, curriculum vitae, personal interviews, as well as full-text journal articles, and book publications was performed. Dr Rhoton was engaged in a busy clinical practice as a young staff at the Mayo Clinic. Records show he focused on tackling complex intracranial pathologies along with numerous basic research and neuroanatomy projects that became a major part of his life's work and passion. He was a great teacher and friend to countless individuals and his work will continue to impact and improve the care provided to neurosurgery patients for generations to come.

Objectives: To compare the diagnostic yield of high-resolution volumetric T2-weighted MRI (HRT2-MRI) with high-resolution computed tomography (HRCT) for diagnosis of large vestibular aqueduct (LVA). Study Design: Three board-certified neuroradiologists performed an independent, blinded radiological review for diagnosing LVA with 2:1 age-matched controls on patients with both HRCT and HRT2-MRI imaging. Setting: Tertiary referral center. Patients: All patients between 2002 and 2016 with hearing loss who underwent both HRCT and HRT2-MRI and were diagnosed with LVA on either modality. Main Outcome Measures: Concordance rate for LVA between HRCT and HRT2-MRI. Results: Concordance rate for HRCT and HRT2-MRI for diagnosing LVA was 88% (124/141) when assessing both the midpoint and external aperture diameters. Fifteen ears had LVA on computed tomography (CT), but not on magnetic resonance imaging (MRI); in comparison, two ears had LVA on MRI, but not on CT (p = 0.002). Excellent inter-rater reliability among the three radiologists was demonstrated. Conclusion: Historically, HRCT has been the imaging modality of choice for diagnosing LVA. Although a higher concordance rate of HRT2-MRI was found compared with previous studies utilizing earlier MRI technology, HRCT still detected a larger number of patients with clinically significant hearing loss compared with MRI. Given the high concordance rate and efficacy of both modalities in diagnosing LVA, the ultimate decision of which modality to choose may depend on other patient-specific and clinical factors.

Hypothesis: A new generation 192-slice multi-detector computed tomography (MDCT) clinical scanner provides enhanced image quality and superior electrode localization over conventional MDCT. Background: Currently, accurate and reliable cochlear implant electrode localization using conventional MDCT scanners remains elusive. Methods: Eight fresh-frozen cadaveric temporal bones were implanted with full-length cochlear implant electrodes. Specimens were subsequently scanned with conventional 64-slice and new generation 192-slice MDCT scanners utilizing ultra-high resolution modes. Additionally, all specimens were scanned with micro-CT to provide a reference criterion for electrode position. Images were reconstructed according to routine temporal bone clinical protocols. Three neuroradiologists, blinded to scanner type, reviewed images independently to assess resolution of individual electrodes, scalar localization, and severity of image artifact. Results: Serving as the reference standard, micro-CT identified scalar crossover in one specimen; imaging of all remaining cochleae demonstrated complete scala tympani insertions. The 192-slice MDCT scanner exhibited improved resolution of individual electrodes (p < 0.01), superior scalar localization (p < 0.01), and reduced blooming artifact (p < 0.05), compared with conventional 64-slice MDCT. There was no significant difference between platforms when comparing streak or ring artifact. Conclusion: The new generation 192-slice MDCT scanner offers several notable advantages for cochlear implant imaging compared with conventional MDCT. This technology provides important feedback regarding electrode position and course, which may help in future optimization of surgical technique and electrode design.

Abstract BACKGROUND One study has investigated postoperative growth rates following subtotal resection of petroclival meningiomas utilizing linear measurements, which are insensitive to the multidimensional complex growth of meningiomas, to estimate tumor volume. OBJECTIVE To describe petroclival meningioma growth patterns following less-than-complete resection utilizing volumetric analysis and to identify variables associated with tumor progression. METHODS Patients with surgically resected WHO grade I petroclival meningiomas were retrospectively reviewed (1999-2015). Image analysis software was utilized to perform volumetric analyses of tumor size and growth on serial MRI studies. The impact of preoperative and postoperative variables on tumor growth after subtotal resection was analyzed. An increase in tumor volume of at least 20% was defined as “tumor growth.” RESULTS Twenty-three patients had immediate preoperative and serial postoperative MRI studies available for review. The mean preoperative tumor volume was 20.9 cm 3 (range 0.4-54.6). The mean extent of resection was 75.5% (range 31.5%-100.0%). At a mean follow-up of 24.8 mo, 12 tumors (66.7%) exhibited radiological tumor growth, while 6 tumors did not change in size. The median annual volumetric growth rate was 2.82 cm 3 /yr (range –0.34 to 10.1). Extent of resection and immediate postoperative tumor volume were significantly correlated with the annual volumetric growth rate following resection. At last follow-up, 3 (13%) patients required further intervention. CONCLUSION The majority of petroclival meningiomas exhibit growth following subtotal resection. Extent of resection is strongly associated with risk for disease progression following surgery.

OBJECTIVEThe management of vestibular schwannoma (VS) remains controversial. One commonly cited advantage of microsurgery over other treatment modalities is that tumor removal provides the greatest chance of long-term cure. However, there are very few publications with long-term follow-up to support this assertion. The purpose of the current study is to report the very long-term risk of recurrence among a large historical cohort of patients who underwent microsurgical resection.METHODSThe authors retrospectively reviewed the medical records of patients who had undergone primary microsurgical resection of unilateral VS via a retrosigmoid approach performed by a single neurosurgeon-neurotologist team between January 1980 and December 1999. Complete tumor removal was designated gross-total resection (GTR), and anything less than complete removal was designated subtotal resection (STR). The primary end point was radiological recurrence-free survival. Time-to-event analyses were performed to identify factors associated with recurrence.RESULTSFour hundred fourteen patients met the study inclusion criteria and were analyzed. Overall, 67 patients experienced recurrence at a median of 6.9 years following resection (IQR 3.9–12.1, range 1.2–22.5 years). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following resection were 93% (95% CI 91–96, 248 patients still at risk), 78% (72–85, 88), 68% (60–77, 47), and 51% (41–64, 22), respectively. The strongest predictor of recurrence was extent of resection, with patients who underwent STR having a nearly 11-fold greater risk of recurrence than the patients treated with GTR (HR 10.55, p < 0.001). Among the 18 patients treated with STR, 15 experienced recurrence at a median of 2.7 years following resection (IQR 1.9–8.9, range 1.2–18.7). Estimated recurrence-free survival rates at 5, 10, 15, and 20 years following GTR were 96% (95% CI 93–98, 241 patients still at risk), 82% (77–89, 86), 73% (65–81, 46), and 56% (45–70, 22), respectively. Estimated recurrence-free survival rates at 5, 10, and 15 years following STR were 47% (95% CI 28–78, 7 patients still at risk), 17% (5–55, 2), and 8% (1–52, 1), respectively.CONCLUSIONSLong-term surveillance is required following microsurgical resection of VS even after GTR. Subtotal resection alone should not be considered a definitive long-term cure. These data emphasize the importance of long-term follow-up when reporting tumor control outcomes for VS.

Objectives: To report a contemporary review from a single-institution series on Paget's disease of the temporal bone (PDTB). Study Design: Retrospective chart review of patients evaluated from 1998 to 2016. Setting: Quaternary referral center. Patients: Patients with radiographically confirmed PDTB. Main Outcome Measures: Clinical, audiological, and radiological features and management strategies of PDTB. Results: A total of 50 temporal bones in 27 patients (15 men) were diagnosed with PDTB. Symptoms at presentation included hearing loss (n = 23, 85%), headache (n = 18, 67%), dizziness (n = 14, 52%), tinnitus (n = 5, 19%), chronic otitis media (n = 2, 7%), hemifacial spasm without facial paralysis (n = 1, 4%), multiple cranial neuropathies (n = 1, 4%), and neoplastic transformation (n = 1, 4%). Of the 23 ears with audiometric data available for review, 65% exhibited sensorineural hearing loss, and 35% mixed hearing loss. Long-term audiometric follow-up was available on two patients, both of whom demonstrated hearing loss at a rate greater than would be expected for normal aging. Two patients underwent successful cochlear implantation, achieving open-set speech recognition. Radiographic features of temporal bone involvement are reviewed and illustrated. Conclusion: This is the largest single-institution clinical series examining patients with PDTB in the English literature. Variable patterns of temporal bone involvement by Paget's disease are observed leading to a diverse set of clinical symptoms, including slowly progressive hearing loss, tinnitus, compressive cranial neuropathies, and benign or malignant tumorigenesis. Involvement typically begins in the petrous apex and progresses laterally. Otic capsule bone demineralization occurs late in the disease process. Cochlear implantation appears to be an effective management strategy for patients with severe-to-profound hearing loss.

Abstract BACKGROUND The goal of microsurgical removal of a vestibular schwannoma is to completely remove the tumor, to provide long-term durable cure. In many cases, less than gross total resection (GTR) is performed to preserve neurological, and especially facial nerve function. OBJECTIVE To analyze long-term quality of life (QoL) in a cohort of patients who received either GTR or less than GTR. METHODS Patients operated for vestibular schwannoma less than 3.0 cm in posterior fossa diameter at 1 of 2 international tertiary care centers were surveyed using generic and disease-specific QoL instruments. RESULTS A total of 143 patients were analyzed. GTR was performed in 122, and 21 underwent less than GTR. QoL was assessed at a mean of 7.7 yr after surgery (interquartile range: 5.7-9.6). Patients who underwent GTR had smaller tumors; otherwise, there were no baseline differences between groups. Patients who underwent GTR, after multivariable adjustment for baseline features and facial nerve and hearing outcomes, reported statistically significantly better Short Form Health Survey-36 (SF-36) physical and mental scores, Patient-Reported Outcomes Measurement Information System (PROMIS-10) physical and mental scores, and Penn Acoustic Neuroma Quality of Life (PANQOL) facial, energy, general health, and total scores compared to patients receiving less than GTR. CONCLUSION GTR is associated with better QoL using the general QoL measures SF-36 and PROMIS-10 and the disease-specific PANQOL, even after controlling for baseline and outcome differences. This is especially significant in the assessment of mental health, indicating there may indeed be a psychological advantage to the patient that translates to overall well-being to have the entire tumor removed if microsurgical resection is undertaken.