Consensus Statements on the Definition, Classification, and Diagnostic Tests for Tinnitus: A Delphi Study Conducted by the Korean Tinnitus Study Group

Background@#Tinnitus is a bothersome condition associated with various symptoms. However, the mechanisms of tinnitus are still uncertain, and a standardized assessment of the diagnostic criteria for tinnitus is required. We aimed to reach a consensus on diagnosing tinnitus with professional experts by conducting a Delphi study with systematic review of the literature. @*Methods@#Twenty-six experts in managing tinnitus in Korea were recruited, and a two-round modified Delphi study was performed online. The experts evaluated the level of agreement of potential criteria for tinnitus using a scale of 1–9. After the survey, a consensus meeting was held to establish agreement on the results obtained from the Delphi process. Consensus was defined when over 70% of the participants scored 7–9 (agreement) and fewer than 15% scored 1–3 (disagreement). To analyze the responses of the Delphi survey, the content validity ratio and Kendall’s coefficient of concordance were evaluated. @*Results@#Consensus was reached for 22 of the 38 statements. For the definition of tinnitus, 10 out of 17 statements reached consensus, with three statements achieving complete agreement including; 1) Tinnitus is a conscious perception of an auditory sensation in the absence of a corresponding external stimulus, 2) Tinnitus can affect one’s quality of life, and 3) Tinnitus can be associated with hearing disorders including sensorineural hearing loss, vestibular schwannoma, Meniere’s disease, otosclerosis, and others. For the classification of tinnitus, 11 out of 18 statements reached consensus. The participants highly agreed with statements such as; 1) Vascular origin is expected in pulse-synchronous tinnitus, and 2) Tinnitus can be divided into acute or chronic tinnitus. Among three statements on the diagnostic tests for tinnitus only Statement 3, “There are no reliable biomarkers for sensory or emotional factors of tinnitus.”reached consensus. All participants agreed to perform pure-tone audiometry and tinnitus questionnaires, including the Tinnitus Handicap Inventory and Tinnitus Questionnaire. @*Conclusion@#We used a modified Delphi method to establish a consensus-based definition, a classification, and diagnostic tests for tinnitus. The expert panel reached agreement for several statements, with a high level of consensus. This may provide practical information for clinicians in managing tinnitus.

The 24-Hour Cardiac Autonomic Activity in Patients With Allergic Rhinitis

Background@#Definitive knowledge of the 24-hour cardiac autonomic activity in patients with allergic rhinitis (AR) is lacking. Thus, we aimed to evaluate heart rate variability (HRV), which is used to measure cardiac autonomic activity by 24-hour Holter monitoring in patients with AR. @*Methods@#We enrolled 32 patients who visited our clinic and were diagnosed with AR. The control group was selected four-fold (n = 128) by matching (age, sex, hypertension, and diabetes) in the AR group from a Holter registry in the cardiology department. The HRV results, which were measured using 24-hour Holter monitoring, were compared between the AR and control groups. @*Results@#All time-domain parameters of HRV revealed no differences between the groups.However, among the frequency domain parameters of HRV, the low-frequency to highfrequency ratio and low-frequency power in normalized units were significantly lower in the AR group. Conversely, high-frequency power in normalized units was significantly higher in the AR group. In the multiple regression analysis, AR was independently associated with sympathetic withdrawal (adjusted odds ratio = 3.393, P = 0.020) after adjusting for age, sex, hypertension, diabetes mellitus, and hyperlipidemia. @*Conclusions@#The present findings suggest differences in cardiac autonomic activity which are related with sympathetic withdrawal in patients with AR compared with that in the normal population over 24 hours.

Does Listening to Tinnitus Frequency-Filtered Music Relieve Tinnitus?

Background and Objectives@#Tinnitus frequency-filtered music therapy aims to restore lateral inhibition to reverse tonotopic reorganization in the auditory cortex. Although the tinnitus-relieving effect of this therapy has been investigated, the results remain controversial. We performed a prospective, randomized, controlled double-blind study to determine the tinnitus-suppressing effect of tinnitus frequency-filtered music therapy. @*Subjects and Methods@#The study included 90 participants who were randomly categorized into an experimental group that listened to tinnitus frequency-filtered music and a control group that listened to music from which a random frequency was removed. The Tinnitus Handicap Inventory (THI) score and measures of tinnitus loudness, daily awareness, and tinnitus-induced annoyance were evaluated at the initial visit and at 3 and 6 months (final follow-up). The rates of improvement in THI scores in the two groups were also recorded. @*Results@#All measured variables showed significant improvement in both groups, except the matched tinnitus loudness and minimal masking level. However, no significant intergroup differences were observed in the amount of improvement in THI scores and any other variable. The rates of improvement in THI scores were higher in the control group at 3 and 6 months. @*Conclusions@#Listening to tinnitus frequency-filtered music reduced tinnitus-induced handicaps; however, this approach was not significantly better than listening to music from which a random frequency was removed.

The Effect of Primary Levels and Frequencies on the Contralateral Suppression of Distortion Product Otoacoustic Emission

BACKGROUND AND OBJECTIVES: Changes in distortion product otoacoustic emission (DPOAE) caused by contralateral suppression (CS) allow the function of the auditory efferent system to be evaluated. Parameters affording maximum CS are preferred in terms of clinical application. Our objective was to evaluate the effects of primary levels and frequencies on DPOAE-mediated CS. SUBJECTS AND METHODS: Sixteen subjects with normal hearing participated. DPOAEs were recorded with and without contralateral acoustic stimulation; we delivered broadband noise of 65 dB SPL at f2 frequencies between 1,000 Hz and 6,727 Hz, at 8 pt/octave. The L2 was varied between 40 dB SPL and 80 dB SPL in 10-dB steps. RESULTS: L2 did not significantly affect DPOAE-mediated CS. Higher L2 levels significantly reduced the fine structure depth of both the baseline and suppressed DPOAE datasets. The amount of CS was greatly affected by the f2 frequency; lower and higher frequency ranges afforded significantly stronger suppression than did mid-frequencies within the studied range. CONCLUSIONS: Our findings suggest that DPOAE CS should be measured over a wide range of frequencies as the amount of CS seems to be highly dependent on f2. The use of a higher L2 level may be optimal when it is sought to evoke strong DPOAE-mediated suppression while simultaneously minimizing DPOAE fine structure. Our findings may assist in optimization of clinical procedures evaluating the integrity of the auditory efferent system.

Effect of MRI Scanner Noise on Blood Oxygen Level-Dependent Activation of Cortical and Subcortical Auditory Centers / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: We compared functional MRI acquisition methods of sparse temporal acquisition (STA) and continuous acquisition (CA) to estimate the effect of MRI scanner background noise (SBN) on blood oxygen level-dependent (BOLD) activation of cortical and subcortical auditory centers during auditory stimulation. SUBJECTS AND METHOD: Fourteen healthy subjects (eight males, age 30.6+/-4.7 years) were presented with classical music in a block paradigm (36 s on/off) in two STA [repitition time (TR)=12 s, 60 volumes] and two CA (TR=2 s, 360 volumes) functional MRI sessions. To account for the sample size difference, an additional volume-matched continuous dataset (CAm) was generated by matching CA to 60 volumes of STA. A group-level analysis based on BOLD activation maps was performed. Percent signal change (PSC), T-statistic values and signal variability in cortical and subcortical auditory regions of interest (ROIs) were calculated from individual activation maps and compared between the STA, CA, and CAm. RESULTS: The group analysis showed activation in the primary and secondary auditory cortices in all datasets. However, the activation of subcortical auditory centers above the accepted threshold was only observed in STA. STA (less SBN) showed higher PSCs and T-statistic values in all ROIs except planum temporale when compared to CAm. However, there was no difference in signal variability among the datasets. CONCLUSION: Our results suggest that SBN should be considered as a significant confounder in auditory-evoked functional MRI studies particularly in the activation of subcortical auditory centers, and that STA can be an effective imaging method for reducing the effect of SBN.

Current Trends in the Assessment of Patients with Tinnitus and the Proposal of Tinnitus Assessment in Korea / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The effective management of tinnitus should start with an accurate diagnosis, but no concensus has been developed in Korea concerning how to measure the features of tinnitus. This study surveyed otologists in the training hospitals and hospitals specialized in otologic care in Korea to identify the current status in the assessment of patients with tinnitus. SUBJECTS AND METHOD: The questionnaire on the assessment of tinnitus was sent by email to otologists in training and to specialized hospitals specializing in otologics in Korea. The questionnaire included inquiry about various types of tests conducted, such as the audiologic test, tinnitus test, blood test, radiologic test, and the methods of history taking and physical examination for somatic tinnitus. RESULTS: Regarding the audiologic assessment of tinnitus, all the otologist were using pure tone audiometry, 97% speech audiometry, and 87% tinnitus test. For the psychophysical measure of tinnitus, both loudness and pitch matching were conducted by all the otologists. The performance rate of blood test were 38.5%, and the most preferred radiologic test in pulsatile tinnitus was temporal bone computed tomography (59%). Finally, the rate of investigation including the history taking and physical examination of somatic tinnitus was between 74-84%. CONCLUSION: Our results showed that although the tests perfermed by otologists varied, the essential tests for assessing tinnitus were commonly practiced. We analyzed the current status of tinnitus assessment and supplemented guidlines to help measure tinnitus. Further concensus on tinnitus diagnosis is needed, particularly about the standadized and unified principles.

Pulsatile Tinnitus Caused by a Dilated Mastoid Emissary Vein

Although pulsatile tinnitus can be audible, objective demonstration of this heartbeat-synchronous sound has rarely been successful. We report a rare case of pulsatile tinnitus in a 44-yr-old female patient, which was induced by a large mastoid emissary vein (MEV) and objectively documented by Doppler sonography of the left posterior auricular region. The tinnitus was intermittent and the patient could adapt to the tinnitus without intervention on the mastoid emissary vein. These findings suggest that a single large MEV can cause pulsatile tinnitus in the absence of other vascular abnormalities, and imaging studies of the posterior fossa and Doppler ultrasonography can aid the diagnosis in such cases.

Multicenter Study on the Clinician's Diagnostic and Therapeutic Approaches for Benign Paroxysmal Positional Vertigo in Korea / 대한평형의학회지

BACKGROUND AND OBJECTIVES: It is necessary to establish the most efficient diagnostic and therapeutic method for benign paroxysmal positional vertigo (BPPV), which is appropriate for Korean healthcare system. We aimed to evaluate current state of Korean clinician's diagnostic and therapeutic approaches for BPPV. MATERIALS AND METHODS: A 16-item survey was emailed to the members of dizziness department of Otology Research Interest Group in the Korean Otologic Society (n=68). 43 were returned and analyzed. RESULTS: All respondents (100%) used Dix-Hallpike test as a diagnostic tool for vertical canal-BPPV. Supine roll test was used for diagnosing lateral canal BPPV in nearly all the respondents (97.7%). Epley maneuver was chosen as otolith repositioning maneuver (ORM) for posterior canal BPPV in all respondents and barbecue rotation (BBQ) was used for treating lateral canal BPPV with geotropic nystagmus in 95.3% of respondents. Extreme variation was noted for therapeutic approach of lateral canal BPPV with ageotropic nystagmus BBQ, with 4 kinds of ORM and adjunctive measures to liberate otolith from cupula, while BBQ was again the most commonly used ORM (76.7%). CONCLUSION: The development of practical and efficient ORM for lateral canal BPPV with ageotropic nystagmus is necessary.

Current Trends in the Treatment of Subjective Tinnitus at University Hospitals in Korea / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The effective management of subjective tinnitus should start with an accurate diagnosis based on an appropriate classification. Since there is no gold standard for managing subjective tinnitus, clinicians can select from various treatment options after considering the multifactorial etiology of tinnitus. This study surveyed otologists at university hospitals in Korea to identify the treatments used for subjective tinnitus and to obtain basic information on evidence-based medicine for treating tinnitus. SUBJECTS AND METHOD: A five-major-item questionnaire on current tinnitus treatments was sent by email to otologists at 37 university hospitals in Korea; 30 (81.1%) replied. RESULTS: The mean incidence of tinnitus in otology outpatient clinics was 22.7% (range 10-40%). Common treatments were oral pharmacological therapy, regular counseling with tinnitus retraining or cognitive behavioral therapy and hearing aids. Tinnitus retraining therapy and hearing aids were considered the most effective when the visual analog scale scores were 7.0 and 6.6, respectively, and considered safe when the scores were 9.9 and 9.3. Ginkgo biloba and benzodiazepines were the most frequently prescribed drugs, although their reported effectiveness was questionable. Intra-tympanic steroid injection was not considered effective (3.8) or safe (6.3). Somatosensory-based treatments such as treating neck muscle or temporomandibular joint disorders were also used to relieve a subgroup of somatic tinnitus. CONCLUSION: Our results showed trends similar to those in other countries, yet we have not reached the level of evidence-based clinical practice due to the lack of reliable and effective treatment options. Further research on tinnitus-treatments is needed, particularly about randomized controlled studies with blinding.

Voice Handicap Index and Vocal Characteristics of Teachers / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: The effect of vocal abuse on school teachers' lives has not been sufficiently studied in Korea. Our goal was to investigate teachers' vocal characteristics and their functional, physical and emotional disorders due to vocal abuse, and the correlation between them. SUBJECTS AND METHOD: Voice samples of 142 school teachers who responded to the Voice Handicap Index (VHI) questionnaire were used for the acoustic analysis. The results were compared with the control group of 27 office workers of our hospital, who matched the experimental group with respect to age and sex. RESULTS: The subjective measure of VHI showed that the teacher handicap indices were significantly higher than those of the control group in functional, physical and emotional aspects: the corresponding median values were 8, 10, 4.5 and 2, 3, 1 for the two groups, respectively (p<0.05). There was no difference in jitter, shimmer and signal-to-noise ratio between the groups. A cross-correlation analysis revealed no significant correlation between VHI-scores and the results of acoustic analysis. CONCLUSION: The teachers recognize their voice problems as a serious physico-functional disorder. However, the acoustic analysis of the 2 second-voice samples could not detect any differences in voice quality between the two groups. There was no significant correlation between VHI scores and acoustic measures. It suggests that the acoustic measures of voice samples with a limited duration might have a restrictive value in presenting handicaps associated with voice abuse.

Auditory Functional Magnetic Resonance Imaging: How to Begin / 대한이비인후과학회지

No abstract available.

Subjective and Objective Results of Radiofrequency Ablation in Drug-Resistant Allergic Rhinitis Based on a 12-Month Follow-up Study

BACKGROUND AND OBJECTIVES: Allergic rhinitis is a common condition that has been treated using various methods. Nevertheless, it remains an intractable condition in some cases. We evaluated the long-term efficacy of radiofrequency ablation (RFA) therapy for drug-resistant allergic rhinitis. MATERIALS AND METHODS: Eighteen patients with allergic rhinitis were enrolled in this prospective interventional study. Their subjective symptoms and objective findings were assessed using a visual analogue scale and acoustic rhinometry before and after RFA therapy. Postoperative follow-up was carried out at 1, 3, 6, and 12 months. RESULTS: Nasal obstruction and rhinorrhea were improved significantly (p<0.001 and p=0.015, respectively), and these effects continued for 12 months after RFA therapy. However, the effects on nasal itching and sneezing did not last throughout the year of the study. Patients' overall satisfaction scores declined at 12 months. On acoustic rhinometry, the minimal cross-sectional area and the total nasal volume did not show improvement, and there were no correlations with the subjective symptoms. Most of the complications associated with the RFA procedure were minimal and resolved within 4 weeks. CONCLUSION: RFA is a safe, simple, and effective procedure for relieving nasal obstruction and rhinorrhea for at least 12 months in drug-resistant allergic rhinitis.

Effects of Various Intracranial Volume Measurements on Hippocampal Volumetry and Modulated Voxel-based Morphometry

PURPOSE: To investigate the effects of various intracranial volume (ICV) measurement methods on the sensitivity of hippocampal volumetry and modulated voxel-based morphometry (mVBM) in female patients with major depressive disorder (MDD). MATERIALS AND METHODS: T1 magnetic resonance imaging (MRI) data for 41 female subjects (21 MDD patients, 20 normal subjects) were analyzed. Hippocampal volumes were measured manually, and ICV was measured manually and automatically using the FreeSurfer package. Gray and white matter volumes were measured separately. RESULTS: Manual ICV normalization provided the greatest sensitivity in hippocampal volumetry and mVBM, followed by FreeSurfer ICV, GWMV, and GMV. Manual and FreeSurfer ICVs were similar in normal subjects (p = 0.696), but distinct in MDD patients (p = 0.000002). Manual ICV-corrected total gray matter volume (p = 0.0015) and Manual ICV-corrected bilateral hippocampal volumes (right, p = 0.014; left, p = 0.004) were decreased significantly in MDD patients, but the differences of hippocampal volumes corrected by FreeSurfer ICV, GWMV, or GMV were not significant between two groups (p > 0.05). Only manual ICV-corrected mVBM analysis was significant after correction for multiple comparisons. CONCLUSION: The method of ICV measurement greatly affects the sensitivity of hippocampal volumetry and mVBM. Manual ICV normalization showed the ability to detect differences between women with and without MDD for both methods.

Convulsion, Symptomatic Hyponatremia and Paralytic Ileus Following Tonsillectomy: A case report / 대한마취과학회지

Severe symptomatic hyponatremia shows high mortality in association with cerebral edema and central nervous system dysfunction. Postoperative hyponatremia is usually attributed to administration of hypotonic fluids while antidiuretic hormone is acting. However, we experienced a severe symptomatic hyponatremia in spite of infusion of lactated Ringer's solution perioperatively in a case of 4-year-old girl's tonsillectomy. Inappropriate secretion of ADH caused by pain, stress, anxiety, nausea, vomiting. Paralytic ileus developed several hours after surgery, severe hyponatremia (Na 119 mmol/L) with convulsion notified. After prompt infusion of sodium supplement and fluid restriction, the patient recovered uneventfully.

The Clinical and Radiological Evaluation of Results about Closed Reduction for Children with Nasal Bone Fractures / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: It has generally been accepted that closed reduction is the management of nasal fracture in children. But proper management is still confusing and clinical and radiological evaluation about long term results have yet to be determined. The purpose of this study is to determine which closed reduction method for nasal bone fractures in children is effective when considering clinical and radiological aspects. MATERIALS AND METHOD: We analysed the medical records of 35 children with nasal bone fractures up to the age of 15, who were operated by closed reduction between 2000 and 2002. We evaluated postoperative satisfaction of doctors and patients and postoperative CT scan score (Motomura et al 2001) of 14 children over more than at least 2 postoperative years. RESULTS: A peak incidence ages ranged from 13 to 15 years. The most frequent cause was sports injuries. The degree of postoperative satisfaction and postoperative CT scan score was favorable. CONCLUSION: In management of nasal fracture in children, closed reduction is effective and satisfactory when clinical and radiological aspects are considered.

Electrocochleography in Noise-Induced Hearing Loss / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Electrocochleography (ECoG) is a sensitive evoked-response test for evaluating changes in cochlear function. We investigated the extratympanic ECoG in noise-induced temporary and permanent threshold shift to evaluate the usefulness of ECoG in the early detection and monitoring of noise-induced hearing loss (NIHL). SUBJECTS AND METHOD: Fifteen healthy ears were exposed to noise to induce temporary threshold shift (TTS). Pure-tone audiometry and ECoG were performed before (control-group), immediately after (TTS-group), and 24 hours after the exposure. And ECoG was measured in 27 ears with noise-induced permanent threshold shift (PTS-group). RESULTS: The mean amplitude of SP (summating potential) was greatest in the TTS-group. The largest increment in the SP/AP (action potential) ratio was also observed in the TTS-group. The mean ratios of control-, TTS-, and PTS-group were 0.22+/-0.11, 0.46+/-0.18 and 0.37+/-0.10, respectively. The PTS-group showed the smallest mean amplitude of AP. CONCLUSION: The results of this study suggest that SP, AP and the SP/AP ratio might be sensitive parameters reflecting the changes of cochlear function in NIHL.

The First Isolation of Chlamydia pneumoniae from a Korean Patient / 결핵

BACKGROUND: Chlamydia pneumoniae is one of common causes in upper and lower respiratory infections. Isolating C. pneumoniae from clinical specimens is very difficult due to the characteristics of the organism. Recently, we succeeded in isolating C. pneumoniae from a Korean patient, who suffered from acute pharyngitis. This is the first isolate from a clinical specimen in Korea. METHOD: We attained a nasopharyngeal swab from a 22-year-old female patient, and inoculated it on a monolayer of the Hep-2 cell line. After 8 passages, we found the inclusion bodies of C. pneumoniae by an immunofluorescence(IF) test. The species-specific monoclonal antibody IF staining and species-specific PCR were done to confirm the species of the isolate, and electron microscopy was used to characterize the morphology. RESULT: The isolate was confirmed to be C. pneumoniae by species-specific IF and PCR, and the strain was named LKK-1. The shape of the elementary body was round and with a narrow periplasmic space, as shown by electron microscopy, which is similar to the Japanese strain, but not the Western strain. CONCLUSION: We succeeded in isolating C. pneumoniae from a 22-year-old patient with acute pharyngitis, which is the first isolate in Korea. In the future, this Korean strain will be useful to the study of C. pneumoniae.

3C8, a new monoclonal antibody directed against a follicular dendritic cell line, HK

BACKGROUND: Follicular dendritic cells (FDCs) play key roles during T cell-dependent humoral immune responses by allowing antigen-specific B cells to survive, proliferate, and differentiate within the FDC networks of secondary follicles, i.e., germinal centers (GC). METHODS: A novel monoclonal antibody, 3C8, was generated by immunizing with an FDC line HK, in order to understand the molecular signals involved in the FDC-B cell interactions in the microenvironment of the GC. RESULTS: The 3C8 antibody did not bind to mononuclear cells, including T cells, B cells, and monocytes. Murine L929 and human skin fibroblasts exhibited no or little reactivity to 3C8. However, 3C8 specifically recognized HK cells by flowcytometry. Furthermore, the antigen recognized by 3C8 was restricted to the GC of the human tonsil. Dendritic networks of the GC were intensely stained by 3C8, but cells out side the GC were not. CONCLUSION: Our result s suggest that the antigen 3C8 may play some unique role on FDCs during the GC reactions.

Electrocochleography in Noise-induced temporary threshold shift / 대한이비인후과학회지

BACKGROUND AND OBJECTIVES: Early detection and monitoring are the most important measures in the prevention of development and progression of noise-induced hearing loss (NIHL). Electrocochleography (ECoG) is known as a sensitive evoked-response test to evaluate changes in cochlear function. Through the investigation about the changes of ECoG in development of noise-induced temporary threshold shift (NITTS), we intended to evaluate the usefulness of ECoG on early detection of NIHL. MATERIALS AND METHODS: Ten healthy adult participants (20 ears) were exposed to 90.3~105.0 dB broad-band noise for 3 hours in a computer-game room. Pure-tone audiometry (PTA) and ECoG were performed before the exposure, immediately after and 24 hours after the exposure. RESULTS: Before the exposure, mean PTA threshold was 6.1+/-2.6 dB, which was significantly increased to 12.0+/-3.2 dB immediately after the exposure, and recovered to 5.5+/-2.4 dB at 24 hours later. Marked increment of SP/AP (summating potential/action potential) ratio was observed simultaneously with the development of TTS and was normalized after its resolution. The mean ratio was 0.23+/-0.17 before the exposure, 0.43+/-0.16 on TTS phase, and 0.24+/-0.18 on resolution. CONCLUSION: The result of this study suggest that SP/AP ratio of ECoG might have applicability for early detection and monitoring of NIHL.

A Case of Management of Carotid Artery Rupture by Detachable Balloon Embolization / 대한이비인후과학회지

Carotid artery rupture ranks as the most dreaded among the head and neck surgery complications. Despite the well-documented risk of cerebral ischemia, operative carotid ligation has been the traditional management of last resort for carotid artery rupture. Over the past several years, however, the technique of endovascular occlusion of blood vessels has demonstated considerable promise in the management of carotid artery rupture. With the help of endovascular balloon occlusion, the authors managed a case of carotid artery rupture developed after the radiation therapy of laryngeal carcinoma and the salvage laryngectomy with neck dissection. Embolization on the right carotid artery was performed with detachable balloons and spiral coils after the carotid artery occlusion test. The patient did not show any complications of neurological function. The pharyngocutaneous fistula and skin defects were reconstructed with the use of pectoralis muscuocutaneous flap.