Neck Radiographs Research Articles

A Tenacious Trio of Retropharyngeal Emphysema, Pneumomediastinum and Subcutaneous Emphysema Secondary to Pulmonary Tuberculosis: A Case Report

Retropharyngeal emphysema (RPE) is the presence of air in the retropharyngeal area. It may occur due to various etiologies or sometimes spontaneously due to an underlying lung pathology. This report describes a case of a 26-year-old gentleman with pulmonary tuberculosis on treatment who presented with acute breathlessness and dysphagia. His neck and chest radiograph showed retropharyngeal emphysema with pneumomediastinum and subcutaneous emphysema. This was further confirmed by a CT neck and thorax. The patient was managed conservatively with analgesia, antibiotics, IV corticosteroids and oxygen supplementation. Repeat chest radiograph after 17 days showed resolution of retropharyngeal emphysema. Clinicians should have a high index of suspicion for RPE in patients who present with unexplained acute breathlessness and dysphagia of a diseased lung.

A Tenacious Trio of Retropharyngeal Emphysema, Pneumomediastinum and Subcutaneous Emphysema Secondary to Pulmonary Tuberculosis: A Case Report

Retropharyngeal emphysema (RPE) is the presence of air in the retropharyngeal area. It may occur due to various etiologies or sometimes spontaneously due to an underlying lung pathology. This report describes a case of a 26-year-old gentleman with pulmonary tuberculosis on treatment who presented with acute breathlessness and dysphagia. His neck and chest radiograph showed retropharyngeal emphysema with pneumomediastinum and subcutaneous emphysema. This was further confirmed by a CT neck and thorax. The patient was managed conservatively with analgesia, antibiotics, IV corticosteroids and oxygen supplementation. Repeat chest radiograph after 17 days showed resolution of retropharyngeal emphysema. Clinicians should have a high index of suspicion for RPE in patients who present with unexplained acute breathlessness and dysphagia of a diseased lung.

Abstract P324: Masked Hypertension Mimicking Migraine: A Case Report with Diagnostic Odyssey

Introduction: Masked hypertension (MH) involves normal office blood pressure but elevated readings outside clinical settings, increasing cardiovascular and neurological risks. About 10-30% of the population may have MH, often undiagnosed. This case highlights the importance of considering MH. Case Presentation: A 42-year-old woman had recurrent headaches for six months: bilateral, pulsating pain in the temples, with dizziness and occasional vomiting, lasting 2-4 hours, worsening after work. Diagnosed with migraines and treated with sumatriptan without relief. Medical history included a caesarean section; otherwise, she was healthy. Physical exam showed normal vital signs, including blood pressure at 130/80 mmHg. Neurological and ophthalmological evaluations were normal. Lab investigations were unremarkable. The patient had a normal BMI of 21.3. Further workup, including ECG, MRI, CT scan, and neck radiography, all normal. Ambulatory blood pressure monitoring (ABPM) revealed elevated blood pressure during evening hours (post work), starting around 4 pm and rising until 8-9 pm. Thereafter, blood pressure normalized to 110-130 mmHg systolic and 70-80 mmHg diastolic. To rule out nephrogenic hypertension, an ultrasound of the kidneys, renal function tests, urinalysis, and plasma metanephrine tests were negative. Following the exclusion of other causes, a diagnosis of MH was established. The patient started on Telmisartan 20 mg daily, with lifestyle modifications. Follow-up ABPM showed normalized blood pressure, and the patient reported no further headaches. Discussion: MH affects many but often remains undiagnosed due to normal clinic readings. Ambulatory or home blood pressure monitoring is essential for diagnosis. Timely diagnosis of MH is crucial, given its association with heightened risks of stroke and cardiovascular disease. Studies have revealed significantly elevated left ventricular mass index, maximal intima-media thickness, and urinary albumin levels. Consequences include left ventricular hypertrophy, carotid atherosclerosis, and albuminuria. Conclusion: Early recognition and management of MH are vital for preventing complications. Diagnosis can be achieved by home blood pressure monitoring (HBPM) or 24-hour ambulatory blood pressure. This case stresses considering MH in patients with normal office readings but persistent symptoms, advocating for regular monitoring and patient education for optimal health outcomes.

Evaluation of Dentofacial Angles in Children with Severe Adenoid Hypertrophy.

Hypertrophy of adenoids is a common condition in childhood, resulting in obstructive symptoms such as sleep apnea, snoring, and rhinosinusitis. Adenotonsillectomy is recommended to improve prognosis and quality of life. This case-control study compared facial angles and lip position related to dentofacial and mouth growth in symptomatic children with adenoid hypertrophy and asymptomatic control groups. The study included children aged 5 to 7 who presented with obstructive symptoms and confirmed severe adenoid hypertrophy in lateral neck radiography. Standard lateral photography was taken. The Nasofacial and Nasomental angles, and upper and lower lip positions and their distance behind the Ricketts line, were measured and compared with the normal control group. This study included 54 children with severe adenoid hypertrophy and 66 normal children. Facial angles were not significantly different between the two groups, but the mean horizontal position of the upper and lower lip in children with adenoid hypertrophy was significantly lower than in the control group (P value = 0.05). The lips were too close to the Ricketts line compared with the control group. This research demonstrates that children with severe adenoid hypertrophy have more dentofacial disorders than others. Adenotonsillectomy surgery is necessary for children with obstructive symptoms caused by tonsil enlargement, and if symptoms like snoring persist post-surgery, complementary orthodontic treatments should be considered.

Neck pain but not neurologic disease occurs more frequently in horses with transposition of the ventral lamina from C6 to C7.

To determine reasons for horses to have neck radiographs performed, the incidence of transposition of the ventral lamina of C6 onto C7 (TC67), and the final diagnoses for all horses. Our hypotheses were to find a similar incidence of TC67, as has been previously reported, and an increased incidence of neck pain and dysfunction in horses with TC67. 135 horses. Retrospective observational study. Medical records of 135 horses with cervical vertebral column radiographs between 2020 and 2022 were assessed. Patient signalment, reasons for radiographs, radiographic findings, and diagnoses were analyzed. The Shapiro-Wilk test was used for normality determination. Nonparametric tests were used to analyze data. 20% of horses were diagnosed with TC67. Significantly more horses with TC67 were warmblood horses (63%); TC67 was found in 28% of warmblood horses. There was no significant difference in signalment or whether horses were in work between the groups, although significantly more horses with TC67 performed in English disciplines (71%). No differences in reasons for examination or final diagnoses of neurologic disease, cervical orthopedic disease, or lameness were present between groups. In horses with neck pain, TC67 was significantly more common (31%) than in horses without (18%). Our results indicated that TC67 occurs more in warmblood horses. In the small group of horses with neck pain reported, TC67 was more commonly seen than in those without. Given the complexity of this region and the paucity of studies exploring neck pain and neck biomechanics, we suggest the need for standardized prospective studies.

Calcification of stylohyoid ligaments and its association with obesity: A cross‐sectional retrospective study

AbstractIntroductionObesity is associated with an increase in pro‐inflammatory cytokines, which eventually lead to soft tissue dystrophic calcifications. Calcifications of the stylohyoid ligament (SHL) are incidental findings occasionally seen in head and neck radiographs, the cause of which is not yet established. In this study, we investigated the possible association between obesity and SHL calcification.MethodsArchived cone beam computed tomography (CBCT) scans of 136 patients were retrieved and assessed for the presence and length of calcifications of the SHLs. Patients' height and weight were retrieved from their medical records, from which body mass index (BMI) values were calculated. Later, patients were telephone‐interviewed and asked about histories of tonsillectomy and trauma to the head and neck. Chi‐square and Mann–Whitney U tests were used to assess associations between SHL calcifications and BMI values in their nominal and continuous formats, respectively.ResultsCalcification of SHLs was detected in 63 (46.3%) of the retrieved CBCT scans. BMI values ranged from 17 to 40 (mean 27.4 (SD = 4.9)), with 30% being in the healthy category. Histories of tonsillectomy and head and neck trauma were reported in 13.5% and 7.4%, respectively. SHL calcifications were associated with the female sex (p = 0.02) and normal weight (p = 0.04). No associations were seen between SHL calcifications and age, tonsillectomy or trauma.ConclusionsDespite being associated with dystrophic calcifications of ligaments, obesity—in our study—was not associated with SHL calcifications.

Gossypiboma larynx: a rare cause of post-tracheostomy stridor—case report and review of literature

BackgroundGossypiboma, a retained surgical sponge with a foreign body reaction, is an unusual but serious complication seen in open abdominal surgeries. It is exceptionally rare following head and neck surgeries. Here, we present a case of Gossypiboma of the upper airway following tracheostomy.Case presentationA 32-year-old male presented with stridor and difficulty breathing one-month post-tracheostomy after a severe head injury following a road traffic accident. A neck radiograph was unremarkable, and a computed tomography (CT) scan of the neck showed a well-defined homogenous curvilinear membrane extending from the hypopharynx to the upper trachea. Bronchoscopic evaluation of the larynx and upper trachea revealed a retained surgical sponge, which was retrieved. The patient’s breathing improved drastically post intervention.ConclusionGossypiboma may go undetected in radiographs and may also present atypically as a homogenous membrane on a CT scan of the neck. Though rare, retained surgical items can have profound medicolegal and professional consequences on physicians. Hence, a strong clinical suspicion and vigilance for gossypiboma is necessary for patients presenting with respiratory distress post-tracheostomy.

A rare case of disseminated tuberculosis presenting as multiple visceral abscesses: retropharyngeal abscess, epidural abscess, pulmonary Koch’s, hepatic granuloma and splenic abscess

Extrapulmonary TB can present with plethora of clinical signs and symptoms, the spectrum of which remains boundless. Retropharyngeal abscess, epidural abscess, splenic abscess, hepatic granuloma are rare presentations of extrapulmonary TB which requires paramount clinical expertise for diagnosis and timely management thereby preventing dangerous complications. Here is a case report of a 6 year old boy presenting with 2 months history of fever, neck pain and swelling, difficulty in swallowing solid food, restricted neck movements, weight loss and family history of TB contact. Examination revealed bilateral jugulodigastric (level I and II) cervical lymphadenopathy (around 2×2 cm), neck rigidity and a paramedian bulge over posterior pharyngeal wall (measuring 3×3 cm), the inferior extent of which was difficult to visualize on oral cavity examination. Patient was worked up keeping in mind the high possibility of TB, radiography and ultrasonography of neck confirmed the presence of retropharyngeal abscess. CECT neck, chest and abdomen was done to find the extent of lesion and to look any other evidence of tuberculosis which revealed presence of retropharyngeal abscess, epidural abscess, pulmonary Koch’s, hepatic granuloma and splenic abscess with features s/o tuberculosis. He was started on ATT on clinico-radiological basis, his abscess was drained and cheesy material and pus were sent for microbiological and histo-pathological examination, although microbiological evidence was non-contributory, histopathology confirmed tuberculous retropharyngeal abscess. This case reporting was done to elicit the rare presentation of EPTB and the need of high degree of clinical suspicion for early diagnosis and timely treatment to prevent future complications.

Successful Management of Retropharyngeal Lymphangioma with Stridor Using Sirolimus: A Case Report.

Lymphatic malformations (LMs) are one of the congenital malformations of the lymphatic system in the body. The patient usually presents with head and neck swelling, airway compression, and/or airway obstruction. The diagnosis of retropharyngeal LMs can be challenging due to their rare occurrence. We report a case of a five-month-old boy diagnosed with retropharyngeal LMs. He presented with a three-day history of fever, cough, and stridor and was initially treated for acute bronchiolitis. A lateral neck radiograph revealed prevertebral widening, suggesting retropharyngeal collection. The patient's condition worsened, requiring intubation in the operating room and proceeding with aspirations and drainage. However, the symptoms recurred after a few days, necessitating re-intubation, repeated aspirations and drainage procedures. The patient was intubated, and the neck's magnetic resonance imaging (MRI) confirmed retropharyngeal LMs. An elective tracheostomy was performed and was treated with sirolimus. The patient had a successful tracheostomy decannulation and showed no recurrence during follow-up.

Effect of Thyroidectomy on Tracheal Remodeling and Airway Physiology in Apparently Asymptomatic Patients with Goiter: A Prospective Study.

Tracheal airflow limitation is frequently reported in patients with goiter but is severely underestimated, and studies on how goiter and its treatment affect trachea are scarce. Moreover, the choice of the optimal treatment for individual patient with asymptomatic goiter is not straightforward. Therefore, in this study we aim to investigate the effect of goiter and subsequent thyroidectomy on tracheal anatomy and change in airflow in asymptomatic patient with goiter. Seventy patients undergoing total/hemithyroidectomy (TT/HT) from Feb 2020 to Feb 2021 satisfying inclusion criteria were enrolled in the study. Neck radiograph (NR) and forced spirometry (FS) were performed preoperatively and on postoperative day 10 and 6weeks and 3months. Out of 70 patients, 84.3% patients were female, and mean duration and weight of goiter were 54.7months and 72.21gm, respectively. Of 70 patients, 57 were of benign pathology. Significant improvement in tracheal compression with moderate improvement in deviation was observed after surgery. Preoperative spirometry showed significant reduction in almost all parameters. After surgery, a weak improvement was observed at postoperative day 10 and 6weeks; however, significant improvement in FEV1, PEFR, FEV1/FEV0.5, and FEF50%/FIF50% was observed at postoperative 3months. Patient with right sided and those with ≥ 8mm deviation were associated with poorer pulmonary function. Weak correlation was observed between neck NR and spirometry parameters. Weight of the thyroid gland significantly correlated with ratio of MVV/FEV1. Patients with asymptomatic goiter can have significant abnormal changes in airflow as evidenced by FS and NR. Thyroidectomy is followed by gradual restoration of tracheal deviation and compression with significant improvement in pulmonary airflow.

Lateral neck radiography: the case is not closed.

Lateral neck radiography: the case is not closed.

Radiolucent metallic foreign body: a case report

A 13-year-old boy who accidentally ingested an aluminum beverage can pull tab. Neck and chest radiographs did not reveal any ingested foreign body. This case report illustrates poor negative predictive value of conventional radiographs for a suspected aluminum foreign body and demonstrates superiority of CT for this purpose. In such presentations, it is imperative to have a low threshold for performing further diagnostic evaluation with CT due to the relatively high radiolucency of aluminum.

Surgical management of complete esophageal obstruction in graded Murrah buffalo (Bubalus bubalis) - A case report

A seven-year-old, advance pregnant graded Murrah buffalo was presented with sudden onset of profuse salivation, anorexia, severe tympany and generalized discomfort. Palpation revealed enlarged cervical esophageal mass with pain and gagging reflex. Plain lateral radiography of neck showed presence obstructed mass in cervical esophageal lumen. The obstructed mass was removed via esophagotomy under deep sedation and local infiltration anaesthesia with uneventful recovery.

Improving detection of impacted animal bones on lateral neck radiograph using a deep learning artificial intelligence algorithm

ObjectiveWe aimed to develop a deep learning artificial intelligence (AI) algorithm to detect impacted animal bones on lateral neck radiographs and to assess its effectiveness for improving the interpretation of lateral neck radiographs.MethodsLateral neck radiographs were retrospectively collected for patients with animal bone impaction between January 2010 and March 2020. Radiographs were then separated into training, validation, and testing sets. A total of 1733 lateral neck radiographs were used to develop the deep learning algorithm. The testing set was assessed for the stand-alone deep learning AI algorithm and for human readers (radiologists, radiology residents, emergency physicians, ENT physicians) with and without the aid of the AI algorithm. Another radiograph cohort, collected from April 1, 2020, to June 30, 2020, was analyzed to simulate clinical application by comparing the deep learning AI algorithm with radiologists’ reports.ResultsIn the testing set, the sensitivity, specificity, and accuracy of the AI model were 96%, 90%, and 93% respectively. Among the human readers, all physicians of different subspecialties achieved a higher accuracy with AI-assisted reading than without. In the simulation set, among the 20 cases positive for animal bones, the AI model accurately identified 3 more cases than the radiologists’ reports.ConclusionOur deep learning AI model demonstrated a higher sensitivity for detection of animal bone impaction on lateral neck radiographs without an increased false positive rate. The application of this model in a clinical setting may effectively reduce time to diagnosis, accelerate workflow, and decrease the use of CT.

Delayed atlantoaxial rotatory dislocation in a child with Crohn's disease: illustrative case.

Atlantoaxial rotatory dislocation (AARD) in children may be caused by neck trauma or an upper respiratory tract infection. Here the authors describe the very rare association between inflammatory bowel disease and AARD in a child. A 7-year-old girl presented with an 11-month history of torticollis that occurred spontaneously without a trauma context. Her history revealed a recent diagnosis of Crohn's disease. Physical exam of the cervical spine revealed a "cock-robin" posture. Neck radiography and three-dimensional computed tomography reconstruction established the diagnosis of AARD. Given the duration of the symptoms and failure of previous conservative treatments, the patient was taken to the operating room and underwent open reduction through posterior approach with a C1-2 fusion according to the Harms technique. The torticollis resolved with no recurrence at the last follow-up and minimal restriction of rotation. This is the third report to describe the very rare association between inflammatory bowel disease and AARD but at a very early age, the youngest in the literature. One should be aware of such association as early diagnosis may prevent aggressive surgical management.

Role of neck radiography in assessing recurrent/residual adenoid hypertrophy in children with OSA and history of adenotonsillectomy: a sleep physician perspective.

Recurrent/residual adenoid hypertrophy after adenotonsillectomy in children can result in obstructive sleep apnea (OSA). We aimed to assess the role of soft tissue neck X-ray (STN-XR) in evaluating recurrent/residual adenoid tissue hypertrophy. This was a single-center retrospective study that included children with sleep study-confirmed OSA and a known history of adenotonsillectomy who underwent STN-XR to evaluate for recurrent/residual adenoid tissue hypertrophy. STN-XR nasopharyngeal obliteration and baseline polysomnographic data were analyzed. Multiple linear regression was used to assess the independent relationship between the results of STN-XR and the total apnea-hypopnea index, while controlling for relevant characteristics. The study included 160 participants with a median age of 10 years (quartile [Q] 1 = 7, Q3 = 12.25). More than half of the children were male (59.4%) and the median body mass index z-score was 2.11 (Q1 = 1.23, Q3 = 2.54). STN-XR was normal in 39.4%, and it showed mild, moderate, and complete nasopharyngeal obliteration in 20.6%, 32.5%, and 7.5% of the participants, respectively. Multiple regression analysis showed that moderate and complete nasopharyngeal obliteration was associated with an increase in the mean total apnea-hypopnea index by 109% (P = .0002) and 185% (P = .001), respectively, when compared with children without nasopharyngeal obliteration. However, mild nasopharyngeal obliteration, body mass index z-score, age, sex, and race were not significantly associated with an increase in the total apnea-hypopnea index. STN-XR was useful in assessing recurrent/residual adenoid tissue hypertrophy in children with OSA and a history of adenotonsillectomy. Moderate and complete nasopharyngeal obliteration were associated with significantly increased apnea-hypopnea index. Pediatric sleep physicians may consider STN-XR in the evaluation of children with OSA and previous history of adenotonsillectomy. Senthilvel E, Nguyen QL, Gunaratnam B, Feygin YB, Palani R, El-Kersh K. Role of neck radiography in assessing recurrent/residual adenoid hypertrophy in children with OSA and history of adenotonsillectomy: a sleep physician perspective. J Clin Sleep Med. 2023;19(6):1027-1033.

Using Transfer Learning of Convolutional Neural Network on Neck Radiographs to Identify Acute Epiglottitis.

Acute epiglottitis (AE) is a life-threatening condition and needs to be recognized timely. Diagnosis of AE with a lateral neck radiograph yields poor reliability and sensitivity. Convolutional neural networks (CNN) are powerful tools to assist the analysis of medical images. This study aimed to develop an artificial intelligence model using CNN-based transfer learning to identify AE in lateral neck radiographs. All cases in this study are from two hospitals, a medical center, and a local teaching hospital in Taiwan. In this retrospective study, we collected 251 lateral neck radiographs of patients with AE and 936 individuals without AE. Neck radiographs obtained from patients without and with AE were used as the input for model transfer learning in a pre-trained CNN including Inception V3, Densenet201, Resnet101, VGG19, and Inception V2 to select the optimal model. We used five-fold cross-validation to estimate the performance of the selected model. The confusion matrix of the final model was analyzed. We found that Inception V3 yielded the best results as the optimal model among all pre-train models. Based on the average value of the fivefold cross-validation, the confusion metrics were obtained: accuracy = 0.92, precision = 0.94, recall = 0.90, and area under the curve (AUC) = 0.96. Using the Inception V3-based model can provide an excellent performance to identify AE based on radiographic images. We suggest using the CNN-based model which can offer a non-invasive, accurate, and fast diagnostic method for AE in the future.

The clinical experience of croup at a tertiary care center in Jeddah, Western Saudi Arabia

Background: Viral croup is an upper respiratory tract inflammation that commonly affects children. This paper reports the prevalence, clinical characteristics, outcomes, and management of patients with croup who presented to the emergency department of a tertiary care center in Jeddah, Saudi Arabia. Methods: A retrospective study was conducted using the hospital\'s electronic medical records of pediatric patients with croup aged 0–14 who presented to the emergency department between July 1, 2016, and December 30, 2022. A data collection sheet containing four sections–demographics, clinical manifestations, assessment, and management–was used. Statistical analysis was conducted using JMP statistical software version 15.2.0. Results: A total of 146 patients were included; 74 (50.68%) were under 2 years of age, and approximately half presented to the ER during autumn. Cough was the most common clinical manifestation, reported in 134 patients (91.78%). Regarding the Westley score, a mild grade was reported in 25 (58.14%) patients. Abnormal chest and neck radiographs were observed in 38 (60.32%) and 21 patients (65.63%). Regarding management, dexamethasone was administered to 131 (89.73 %) patients. Moreover, only 15 (10.27%) patients were hospitalized, and the rest were discharged from the emergency department. Conclusion: The study found that approximately half of the total emergency visits for croup cases occurred during autumn, with most patients under 2 years old. The most common clinical symptom noted in these patients was cough. Dexamethasone was administered to most patients; interestingly, most patients did not require hospitalization.

Man on Noninvasive Positive Airway Pressure Ventilation With Throat Pain.

Dentures dislodged into throat on bilevel positive airway pressure (BiPAP) ventilation can be overlooked and potentially compromise airway patency. An 81-year-old man with a history of chronic obstructive pulmonary disease (COPD) presented with increased shortness of breath and productive cough for 1 week. Inhaled bronchodilators, parenteral steroids, and BiPAP ventilation were administered for acute exacerbation of COPD complicated with acute hypercapnic respiratory failure. Fifty minutes after receiving BiPAP ventilation, his respiratory condition improved; however, he started to complain of neck pain. The patient remained intolerant to the device 3 hours later, despite receiving assurance that the discomfort might be caused by air pressure through mask ventilation. His throat did not exhibit any abnormality during visual examination. Neck radiographs were subsequently obtained and demonstrated a denture impacted in the hypopharynx. His neck pain resolved after the removal of the dislodged maxillary denture. Denture dislodgement can occur in mask ventilation and compromise airway patency if stuck in the hypopharynx or respiratory tract. Such adverse events may be overlooked on the coexistence of respiratory and pulmonary diseases. A precisely pharyngolaryngeal inspection and complete imaging studies must be performed to facilitate early identification and further retrieval intervention.

Plain Radiographic Analysis of Laryngeal Dimensions in Young Children: Normal versus Croup.

(1) Background: Contrary to a tenet of the funnel-shaped pediatric larynx with the cricoid level being narrowest, recent studies show the glottis and subglottis as the narrowest levels. To locate the functionally narrowest level of the larynx, we reported normal laryngeal dimensions and their croup-related changes in young children. (2) Methods: We reviewed normal plain neck radiographs recorded for the evaluation of minor trauma or foreign bodies in 504 children aged ≤4 years who visited the emergency department from 2016 through 2021. Using computed tomography-based localization of the glottis, we radiographically defined the subglottis and cricoid. At these levels, we measured diameters and calculated cross-sectional areas (CSAs) on the radiographs. The values were compared to the equivalent values of a 1:1 age-matched population with croup. (3) Results: In the study population (n = 401), the narrowest diameter and CSA were observed in the glottis. In detail, the mean anteroposterior/transverse diameters were 9.8/3.4 mm at the glottis, 8.5/5.6 mm at the subglottis, and 7.4/6.8 mm at the cricoid (p < 0.001), respectively. In the same order, the mean CSAs were 26.5, 38.1, and 40.5 mm2 (p < 0.001). All dimensions were narrower in the croup population (p < 0.001). We found croup-related narrowing, namely reductions in the transverse diameter and CSA that were more severe closer to the glottis (p < 0.001), without differences per level in the anteroposterior diameter. (4) Conclusions: This study confirms the glottis as the narrowest level of the larynx in young children. In addition, level-based differences in croup-related narrowing suggest some point between the glottis and subglottis as the functionally narrowest level.