Short Postoperative Length of Stay After Lateral Cerebrospinal Fluid Leak Repair.

OBJECTIVE: To characterize the short-term outcomes of patients undergoing surgical repair of lateral skull base cerebrospinal fluid (CSF) leaks followed by a shortened length of stay (LOS) protocol. STUDY DESIGN: Retrospective study. SETTING: Tertiary medical center. METHODS: A total of 156 adult patients from July 2016 to December 2022 who underwent repair of CSF leaks via transmastoid (TM), middle cranial fossa (MCF), or combined (TM/MCF) approaches were included. Data collected included: LOS, presentation to the emergency department (ED), need for readmission, major neurologic complications (stroke, seizure, and meningitis), and CSF leak recurrence. RESULTS: Approximately half of patients underwent a TM repair (49.4%), whereas the other half underwent either an MCF (3.8%) or combined TM/MCF repair (46.8%). No peri-/postoperative lumbar drains were used and only 2 (1.3%) patients were admitted to the intensive care unit after surgery. Mean LOS for the cohort was 1.1 ± 0.7 days and was longer for surgeries involving MCF (1.3 ± 0.6) compared to TM (0.8 ± 0.7). Ninety-two percent of TM cases were discharged within 24 hours (32% on the same day) while for cases involving an MCF approach, 72.2% of patients were discharged within 24 hours. Of the patients in the study, 6 (3.8%) presented to an ED for minor complications and no patient required readmission. Revision surgery was required for 3 (1.9%) patients for recurrent CSF leak. CONCLUSION: Our findings suggest that short LOS after surgical repair of lateral skull base defects in the treatment of CSF leak is safe and effective.

Frequency-to-Place Mismatch Impacts Cochlear Implant Quality of Life, But Not Speech Recognition.

OBJECTIVE: To retrospectively compare frequency-place mismatch among adult cochlear implant (CI) recipients with lateral wall (LW) and perimodiolar/Mid Scala (PM/MS) arrays, and to quantify the impact of these factors on early post-activation (3 months) speech recognition abilities and CI-specific quality of life. METHODS: One hundred and twenty-six adult participants were separated into two groups: (1) 83 participants who underwent CI with a PM/MS array and 43 patients who underwent CI with a LW array. All participants completed the Cochlear Implant Quality of Life Profile (CIQOL-35 Profile) instrument. Angular insertion depth and semitone mismatch, which contribute to frequency-place mismatch, were assessed using post-operative CT scans. Word and speech recognition in quiet were determined using the Consonant-Nucleus-Consonant (CNC) and the AzBio tests, respectively (n = 82 patients). RESULTS: LW arrays were more deeply inserted and exhibited less semitone mismatch compared to PM/MS arrays. No significant relationship was found between semitone mismatch and early post-operative speech perception scores for either PM/MS or LW arrays. However, greater degrees of semitone mismatch were associated with lower CIQOL-35 profile scores for PM/MS arrays. CONCLUSIONS AND RELEVANCE: The results of this study indicate that both the degree of frequency-place mismatch, and its impact on CI-specific quality of life, vary by CI array design. LEVEL OF EVIDENCE: 4 Laryngoscope, 2024.

Elevated Body Mass Index Associated with Cerebrospinal Fluid Leak after Lateral Skull Base Surgery: A Systematic Review and Meta-analysis.

OBJECTIVE: To determine if body mass index (BMI) increases the risk of cerebrospinal fluid (CSF) leak after lateral skull base surgery. DATA SOURCES: CINAHL, PubMed, and Scopus were searched from January 2010 to September 2022 for articles published in English. STUDY SELECTION: Articles that reported BMI or obesity with and without CSF leaks after lateral skull base surgery were included. DATA EXTRACTION: Two reviewers (F.G.D. and B.K.W.) independently performed study screening, data extraction, and risk of bias assessment. DATA SYNTHESIS: A total of 11 studies and 9,132 patients met inclusion criteria. Meta-analysis of mean difference (MD), odds ratio (OR), proportions, and risk ratio (RR) were calculated using RevMan 5.4 and MedCalc 20.110. BMI for patients with CSF leak after lateral skull base surgery (29.39 kg/m 2 , 95% confidence interval [CI] = 27.75 to 31.04) was significantly greater than BMI for patients without CSF leak after lateral skull base surgery (27.09 kg/m 2 , 95% CI = 26.16 to 28.01) with an MD of 2.21 kg/m 2 (95% CI = 1.09 to 3.34, p = 0.0001). The proportion of patients with BMI ≥ 30 kg/m 2 that had a CSF leak was 12.7%, and the proportion of patients with BMI < 30 kg/m 2 (control) that had a CSF leak was 7.9%. The OR for CSF leak after lateral skull base surgery in patients with BMI ≥ 30 kg/m 2 was 1.94 (95% CI = 1.40 to 2.68, p < 0.0001), and the RR was 1.82 (95% CI = 1.36 to 2.43, p < 0.0001). CONCLUSION: Elevated BMI increases the risk of CSF leak after lateral skull base surgery. LEVEL OF EVIDENCE: IIa.

Why Do Candidates Forgo Cochlear Implantation?

OBJECTIVE: Identify barriers and facilitating factors in cochlear implant (CI) utilization by comparing functional measures between CI candidates who undergo or forgo implantation. METHODS: Forty-three participants were separated into two groups: (1) 28 participants who underwent CI and (2) 15 participants who elected not to proceed with CI despite meeting eligibility criteria (no-CI). Prior to implantation, all participants completed the CI Quality of Life (CIQOL)-35 Profile and CIQOL-Expectations instrument. They were also surveyed on factors contributing to their decision to either undergo or forgo CI. Word and speech recognition were determined using the Consonant-Nucleus-Consonant (CNC) and the AzBio tests, respectively. RESULTS: CIQOL-Expectations scores were indistinguishable between groups, but there were substantial differences in baseline CIQOL-35 Profile scores. Compared to the CI group, the no-CI group exhibited higher pre-CI scores in the Emotional (Cohen's d [95% CI] = 0.8 [0.1, 1.5]) and Entertainment (Cohen's d [95% CI] = 0.8 [0.1, 1.5]) domains. Survey data revealed that the most commonly reported barriers to pursuing CI in the no-CI cohort were fear of surgical complications (85%), cost associated with implantation (85%), and perception that hearing was not poor enough for CI surgery (85%). CONCLUSIONS AND RELEVANCE: The results of this study indicate that functional outcome expectations are similar between candidates who elect to receive or forgo CI, yet those who forgo CI have higher baseline CI-specific QOL abilities. LEVEL OF EVIDENCE: 4 Laryngoscope, 133:3548-3553, 2023.

Neurophysiological profiles of responders and nonresponders to hypoglossal nerve stimulation: a single-institution study.

STUDY OBJECTIVES: Hypoglossal nerve stimulation (HGNS) is an effective alternative treatment for obstructive sleep apnea that acts by opening the airway via selective stimulation of nerve fibers that innervate tongue muscles that protrude (genioglossus) and stiffen the tongue (transverse and vertical) while avoiding nerve fibers that innervate tongue muscles that retract the tongue (styloglossus and hyoglossus). There remains a subset of postoperative patients who fail to adequately respond to HGNS, in some cases due to mixed activation of muscles that simultaneously protrude and retract the tongue. This study aims to characterize the relationship between neurophysiological data from individual tongue muscle activation during intraoperative electromyographic recordings and postoperative apnea-hypopnea index responses to HGNS. METHODS: A single-institution review of 46 patients undergoing unilateral HGNS implantation for obstructive sleep apnea. Patients were separated into responders and nonresponders through comparison of pre and postoperative apnea-hypopnea index. Neurophysiological data included electromyographic responses of the genioglossus, styloglossus/hyoglossus, intrinsic/vertical, and hyoglossus (neck) muscles to intraoperative stimulation using unipolar (- to - and o to o) and bipolar (+ to +) settings. RESULTS: The overall treatment success rate was 61% as determined by a postoperative apnea-hypopnea index < 20 events/h with a greater than 50% AHI reduction. We observed no statistically significant relationships between treatment response and individual muscle responses. However, we did note that increasing body mass index was correlated with worse postoperative responses. CONCLUSIONS: Although we noted a significant subgroup of clinical nonresponders to HGNS postoperatively, these patients were not found to exhibit significant inclusion of tongue retractors intraoperatively on neurophysiological analysis. Further research is needed to delineate additional phenotypic factors that may contribute to HGNS treatment responses. CITATION: Wang D, Modik O, Sturm JJ, et al. Neurophysiological profiles of responders and nonresponders to hypoglossal nerve stimulation: a single-institution study. J Clin Sleep Med. 2022;18(5):1327-1333.

Comparative Performance of Lateral Wall and Perimodiolar Cochlear Implant Arrays.

OBJECTIVE: The physical shape of cochlear implant (CI) arrays may impact hearing outcomes. The goal of this study was to compare post-operative speech and melody perception between patients with lateral wall (LW) and perimodiolar (PM) electrode arrays across a range of lengths and manufacturers. STUDY DESIGN: Retrospective chart review. SETTING: Tertiary Care Hospital. PATIENTS: 119 adult patients with post-lingual hearing loss who underwent cochlear implantation. MAIN OUTCOME MEASURES: A total of seven different electrodes were evaluated including 5 different LW electrodes (CI422 [Cochlear American], 1J [Advanced Bionics], Medium [Med El], Standard [Med El], Flex28 [Med El]) and 2 PM electrodes (Contour [Cochlear American], MidScala [Advanced Bionics]). Speech perception outcomes (n = 119 patients) were measured by Consonant-Nucleus-Consonant (CNC) scores collected 3, 6, 12 and 24 months after implantation. Melody perception outcomes (n = 35 CI patients and n = 6 normal hearing patients) were measured by Melodic Contour Identification (MCI). RESULTS: CNC scores increased over time after implantation across all array designs. PM designs exhibited higher CNC scores compared to LW electrodes, particularly 6-months after implantation. Pre-operative pure tone averages did not correlate with post-operative CNC scores. PM arrays outperformed LW electrodes in terms of MCI scores. CONCLUSIONS: The physical shape of cochlear implant electrode arrays may impact hearing performance. Compared to LW designs, PM arrays appear to offer superior speech perception during the first 6 months after implantation, with performance equalizing between groups by 24 months. Compared to LW designs, PM arrays also appear to afford superior melody perception.

Comparison of Speech Performance in Bimodal versus Bilateral Cochlear Implant Users.

OBJECTIVE: To assess whether listening with two cochlear implants (bilateral) offers significant benefits in terms of speech perception over listening with one cochlear implant and one hearing aid (bimodal). METHODS: Retrospective review of bilateral cochlear implant recipients (24 pediatric and 26 adult). Bimodal listening was compared to bilateral listening in terms of speech perception performance at 1-year post second implant under three listening conditions: 50 dBHL, 35 dBHL, and 50 dBHL+5 SNR. Changes in speech performance from bimodal (before second implant) to bilateral (after second implant) listening were determined within subjects and compared to a separate control group of bimodal users matched for age of first implantation who never received a second implant (10 pediatric and 20 adult). RESULTS: In the pediatric group, compared to bimodal listening prior to a second implant, speech perception scores with bilateral implants increased significantly when measured at 50 dBHL, 35 dBHL, and 50 dBHL+5 SNR. By contrast, pediatric bimodal controls who never received a second implant failed to demonstrate similar improvement over 1 year's time. In the adult group, compared to bimodal listening prior to a second implant, speech perception scores with bilateral implants increased when measured at 50 dBHL, but were not significantly different at 35 dBHL and 50 dBHL + 5 SNR. Adult bimodal controls who never received a second implant failed to demonstrate significant improvement in all conditions over 1 year's time. CONCLUSION: Bilateral listening with two cochlear implants improved speech perception performance relative to bimodal listening in the pediatric population. Improvement in the adult population was not as significant. LEVEL OF EVIDENCE: 4, Retrospective Chart Review. Laryngoscope, 131:E1322-E1327, 2021.

Intraoperative identification of mixed activation profiles during hypoglossal nerve stimulation.

STUDY OBJECTIVES: The effectiveness of hypoglossal nerve stimulation (HGNS) in the treatment of obstructive sleep apnea (OSA) depends on the selective stimulation of nerve fibers that innervate the tongue muscles that produce tongue protrusion (genioglossus) and stiffening (transverse/vertical) while avoiding fibers that innervate muscles that produce tongue retraction (styloglossus/hyoglossus). Postoperative treatment failures can be related to mixed activation of retractor and protrusor muscles, despite intraoperative efforts to identify and avoid nerve fibers that innervate the retractor muscles. This study describes a novel intraoperative protocol that more optimally identifies mixed activation by utilizing an expanded set of stimulation/recording parameters. METHODS: This study was a case series in a university hospital setting of patients undergoing unilateral hypoglossal nerve stimulation implantation for obstructive sleep apnea. Data included electromyographic responses in the genioglossus and styloglossus/hyoglossus to intraoperative stimulation with an implantable pulse generator using unipolar (- - -, o-o) and bipolar (+-+) settings. RESULTS: In a subset of patients (3/55), low-intensity unipolar implantable pulse generator stimulation revealed significant mixed activation of the styloglossus/hyoglossus and genioglossus muscles that was not evident under standard bipolar implantable pulse generator stimulation conditions. Additional surgical dissection and repositioning of the electrode stimulation cuff reduced mixed activation. CONCLUSIONS: A novel intraoperative neurophysiological monitoring protocol was able to detect significant mixed activation during hypoglossal nerve stimulation that was otherwise absent using standard parameters. This enabled successful electrode cuff repositioning and a dramatic reduction of mixed activation.

Contralateral Tongue Muscle Activation during Hypoglossal Nerve Stimulation.

OBJECTIVE: The effectiveness of upper airway stimulation via hypoglossal nerve stimulation for obstructive sleep apnea depends upon the pattern of tongue muscle activation produced. This study investigated the nature of contralateral tongue muscle activation by unilateral hypoglossal nerve stimulation using intraoperative nerve integrity monitoring in conjunction with electromyography and explored the relationship between contralateral tongue muscle activation and polysomnographic measures of obstructive sleep apnea severity. STUDY DESIGN: Prospective case series. SETTING: Tertiary care medical center. SUBJECTS AND METHODS: Fifty-one patients underwent unilateral (right) hypoglossal nerve stimulator implantation for obstructive sleep apnea. Neurophysiological data included electromyographic responses in ipsilateral (right) and contralateral (left) genioglossus muscles in response to intraoperative bipolar probe stimulation (0.3 mA) of medial hypoglossal nerve branches. Clinical data included pre- and postoperative apnea-hypopnea indices and oxygen desaturation levels. RESULTS: A subset of patients (20/51, 39%) exhibited electromyographic responses in both the ipsilateral and contralateral genioglossus (bilateral), whereas the remaining patients (31/51, 61%) exhibited electromyographic responses only in the ipsilateral genioglossus (unilateral). The baseline characteristics of bilateral and unilateral responders were similar. Both groups exhibited significant and comparable improvements in apnea-hypopnea index and oxygen desaturations after hypoglossal nerve stimulation. Neither the amplitude nor the latency of contralateral genioglossus responses was predictive of clinical outcomes. CONCLUSION: A subset of patients undergoing unilateral hypoglossal nerve stimulation exhibits activation of contralateral genioglossus muscles. Patients with unilateral and bilateral genioglossus responses exhibit comparable, robust improvements in apnea-hypopnea index and oxygen desaturation levels.

Impact of Underlying Diagnosis on Speech and Quality of Life Outcomes After Cochlear Implantation for Single-Sided Deafness.

OBJECTIVE: Our objective was to compare outcomes in speech and quality of life in those undergoing cochlear implantation for single-sided deafness (SSD), with the aim to characterize the clinical impact of underlying diagnosis in the affected ear and pre-operative hearing status. STUDY DESIGN: Prospective case series. SETTING: Academic Cochlear Implant Center. PATIENTS: 42 adult patients implanted with the diagnosis of SSD. INTERVENTIONS: Patients were evaluated at 3-, 6-, and 12-months post-operatively using AZBio sentence and speech, and consonant-nucleus-consonant (CNC) depending on appropriate testing level. Our previously validated Comprehensive Cochlear Implant Quality of Life (CCIQ) questionnaire was administered. MAIN OUTCOME MEASURES: Speech perception, quality of life. RESULTS: Subjects were stratified by the underlying diagnosis: Meniere's Disease (MD; n = 10), sudden sensorineural hearing loss (SSNHL; n = 13), and Other (eg TBI, acoustic neuroma, progressive, noise-induced; n = 19). Mean preoperative PTA of the implanted ear was 82dB ±â€Š17; that of the nonimplanted ear was 32dB ±â€Š17. SSNHL and MD demonstrated the highest speech perception score at 3 months (93 and 95%), and "Other" demonstrated the lowest scores at 88%. All 3 groups demonstrated nadir in speech scores at 6 months before improving at 12 months, but the "Other" diagnoses maintained the lowest speech testing across all time points. All 3 groups reported improved quality of life on CCIQ. CONCLUSIONS: Subjects with SSNHL and MD demonstrate excellent speech perception and quality of life outcomes after cochlear implantation for SSD. Subjects with "Other" diagnoses underlying their SSD demonstrated lower scores on speech testing but nonetheless reported improved quality of life.

Neurophysiological monitoring of tongue muscle activation during hypoglossal nerve stimulation.

OBJECTIVES/HYPOTHESIS: Upper airway stimulation for obstructive sleep apnea (OSA) via implantable hypoglossal nerve stimulation (HGNS) reduces airway obstruction by selectively stimulating nerve fibers that innervate muscles that produce tongue protrusion, while avoiding fibers that produce tongue retraction. This selective stimulation likely depends upon the location, intensity, and type of electrical stimulation delivered. This study investigates the impact of changing stimulation parameters on tongue muscle activation during HGNS using intraoperative nerve integrity monitoring in conjunction with electromyography (EMG). STUDY DESIGN: Prospective case series. METHODS: Ten patients undergoing unilateral HGNS implantation for OSA in a university hospital setting were studied. Data included EMG responses in tongue muscles that produce protrusion (genioglossus), retraction (styloglossus/hyoglossus), and stiffening (transverse/vertical) in response to intraoperative bipolar probe electrical stimulation of lateral and medial branches of the hypoglossal nerve (HGN) and to implantable pulse generator (IPG) unipolar and bipolar settings after placement of the stimulation cuff. RESULTS: Stimulation of medial division HGN branches resulted in EMG responses in genioglossus muscles, but not in styloglossus/hyoglossus muscles, whereas stimulation of the lateral division HGN branches drove responses in styloglossus/hyoglossus muscles. Variable responses in transverse/vertical muscles were observed with stimulation of lateral and medial division branches. After electrode cuff placement, unipolar and bipolar HGN stimulation configurations of IPG resulted in unique patterns of muscle activation. CONCLUSIONS: The relative activation of extrinsic and intrinsic tongue musculature by HGNS is determined by stimulus location, intensity, and type. Intraoperative neurophysiological monitoring of tongue muscle activation enables proper electrode cuff placement and may provide essential data for stimulus optimization. LEVEL OF EVIDENCE: 4 Laryngoscope, 130:1836-1843, 2020.

Quality Assessment of the Clinical Practice Guideline for Tympanostomy Tubes in Children.

OBJECTIVES: To determine the association between the introduction of statements 6 and 7 in the 2013 clinical practice guideline (CPG) for tympanostomy tubes in children and the identification of preoperative middle ear fluid (acute otitis media / otitis media with effusion [AOM/OME]) in children undergoing bilateral myringotomy and tube (BMT) placement. STUDY DESIGN: Case series with chart review. SETTING: Tertiary care children's medical center. SUBJECTS AND METHODS: Patients who underwent BMT for recurrent AOM were retrospectively reviewed. We examined 240 patients before (BG; 2012) and 240 patients after (AG; 2014) the introduction of the CPG. RESULTS: The baseline characteristics of the 2 groups were comparable. The total annual number of BMT placements performed at our institution decreased from 3957 (BG) to 3083 (AG). There was no significant increase in the rate of preoperative AOM/OME identification following CPG introduction (BG 78.3% vs AG 83.3%, P = .164). The rate of identification of AOM/OME in the operating room (OR) increased from 54.2% (BG) to 71.3% (AG, P < .001). The rate of identification of AOM/OME both in the clinic and in the OR increased from 55.1% (BG) to 71.3% (AG, P < .001). Cases with concordant clinic and OR AOM/OME occurred among younger children ( P = .045), those with fewer episodes of AOM ( P = .043), and those with shorter time between the clinic and OR dates ( P = .008). CONCLUSIONS: Following the introduction of the CPG, there was no change in the rate of identification of AOM/OME prior to recommending BMT placement in children with recurrent AOM. The lack of improved compliance with statements 6 and 7 may be related to multiple clinician- and patient-derived factors.

Second tympanostomy tube placement in children with recurrent acute otitis media.

OBJECTIVES/HYPOTHESIS: To determine the rate and predictors of electing for a second bilateral myringotomy and tympanostomy tube placement (BMT) in children with recurrent acute otitis media (RAOM). STUDY DESIGN: Retrospective chart review. METHODS: Charts of 600 children who underwent BMT for RAOM between 2012 and 2014 were reviewed. RESULTS: The overall rate of a second BMT was 15.2% (91/600) and occurred a median of 1.58 years after the initial BMT. The most common indication was continued RAOM with extruded tubes. There was a higher rate of second BMT in patients of younger age (1.06 vs. 1.32 years old, P < .001) and those with a positive family history of RAOM/BMT in a first-degree relative (odds ratio [OR]: 1.67, 95% confidence interval [CI]: 1.02-2.73, P = .041). Identification of middle ear fluid intraoperatively (OR: 1.99, 95% CI: 1.22-3.26, P = .005) but not preoperatively (OR: 1.88, 95% CI: 0.98-3.57, P = .051) was associated with higher rates of second BMT. Children with bilateral intraoperative fluid (OR: 2.25, 95% CI: 1.42-3.58, P < .001) or fluid both preoperatively and intraoperatively (OR: 2.25, 95% CI: 1.40-3.61, P = .001) had greater higher risk of requiring second BMT. In this series, the finding of blocked tubes or tube otorrhea at the first postoperative visit were not predictive of an increased risk of second BMT. CONCLUSIONS: Children who underwent BMT for RAOM were more likely to undergo second BMT if they were of younger age, had a family history of RAOM/BMT, or were found to have middle ear fluid intraoperatively. The overall second BMT rate for children with RAOM is lower than in studies examining all BMT indications. LEVEL OF EVIDENCE: 4. Laryngoscope, 128:1476-1479, 2018.

Noise Trauma-Induced Behavioral Gap Detection Deficits Correlate with Reorganization of Excitatory and Inhibitory Local Circuits in the Inferior Colliculus and Are Prevented by Acoustic Enrichment.

Hearing loss leads to a host of cellular and synaptic changes in auditory brain areas that are thought to give rise to auditory perception deficits such as temporal processing impairments, hyperacusis, and tinnitus. However, little is known about possible changes in synaptic circuit connectivity that may underlie these hearing deficits. Here, we show that mild hearing loss as a result of brief noise exposure leads to a pronounced reorganization of local excitatory and inhibitory circuits in the mouse inferior colliculus. The exact nature of these reorganizations correlated with the presence or absence of the animals' impairments in detecting brief sound gaps, a commonly used behavioral sign for tinnitus in animal models. Mice with gap detection deficits (GDDs) showed a shift in the balance of synaptic excitation and inhibition that was present in both glutamatergic and GABAergic neurons, whereas mice without GDDs showed stable excitation-inhibition balances. Acoustic enrichment (AE) with moderate intensity, pulsed white noise immediately after noise trauma prevented both circuit reorganization and GDDs, raising the possibility of using AE immediately after cochlear damage to prevent or alleviate the emergence of central auditory processing deficits.SIGNIFICANCE STATEMENT Noise overexposure is a major cause of central auditory processing disorders, including tinnitus, yet the changes in synaptic connectivity underlying these disorders remain poorly understood. Here, we find that brief noise overexposure leads to distinct reorganizations of excitatory and inhibitory synaptic inputs onto glutamatergic and GABAergic neurons and that the nature of these reorganizations correlates with animals' impairments in detecting brief sound gaps, which is often considered a sign of tinnitus. Acoustic enrichment immediately after noise trauma prevents circuit reorganizations and gap detection deficits, highlighting the potential for using sound therapy soon after cochlear damage to prevent the development of central processing deficits.

Diagnosis and Management of Cervical Thymic Cysts in Children.

We present the case of a 10-year-old boy with the sudden onset of a large, painless left neck mass. Findings on magnetic resonance imaging (MRI) and fine needle aspiration (FNA) biopsy suggest a cystic lesion, most likely of thymic origin. Cervical thymic cysts are a rare form of cervical mass, which are easily overlooked in the differential diagnosis of children presenting with painless neck masses. A combination of CT and MRI investigations can be helpful in differentiating thymic cysts from other congenital and neoplastic masses, but the definitive diagnosis of thymic cyst requires histopathological documentation of thymic tissue. Surgical excision is considered the management of choice for thymic cysts, and no cases of postoperative recurrence have been reported.

Mapping Auditory Synaptic Circuits with Photostimulation of Caged Glutamate.

Photostimulation of neurons with caged glutamate is a viable tool for mapping the strength and spatial distribution of synaptic networks in living brain slices. In photostimulation experiments, synaptic connectivity is assessed by eliciting action potentials in putative presynaptic neurons via focal photolysis of caged glutamate, while measuring postsynaptic responses via intracellular recordings. Two approaches are commonly used for delivering light to small, defined areas in the slice preparation; an optical fiber-based method and a laser-scanning-based method. In this chapter, we outline the technical bases for using photostimulation of caged glutamate to map synaptic circuits, and discuss the advantages and disadvantages of using fiber-based vs. laser-based systems.