Modified Barium Swallow Study (MBSS)/Videofluoroscopy

MBSS is performed through the collaborative efforts of a speech pathologist and a radiologist. Images can be obtained in lateral and AP projections. Neonates and young infants are generally imaged in a side-lying position, whereas older infants and children are seated for the exam [4]. Various consistencies of barium (liquid, thickened liquid, semisolid, and solid) can be administered to determine what foods result in aspiration and which are safe for the patient to eat. Beyond determining only the presence or absence of aspiration, the swallow study evaluates where, when, and why the swallow breaks down and looks at alterations in structure and deficits in strength and timing. Positioning, viscosity, and method of delivery can all be altered to determine the safest and most effective way for an infant or child with dysphagia to eat. In older children, it is often best to attempt to cover their favorite foods with barium. For example, mix barium into yogurt or sprinkle barium powder in a peanut butter and jelly sandwich. By allowing the child to choose the foods they eat, tolerance of the exam improves. Additionally, it is important to test foods that parents report the child has problems with at home.

The field of view should be limited to the superior margin of the nasal cavity to avoid radiation to the eyes. The inferior margin of the image should include the upper chest so that tracheoesophageal fistulas and reflux can be seen. The mouth needs to be included in the field of view so that both the oral and pharyngeal phases of swallowing can be evaluated [4]. There is much debate between speech pathologists and radiologists regarding an acceptable frame rate by which to obtain images. There needs to be a balance between trying to decrease radiation exposure in pediatric patients who are more susceptible to the potential deleterious effects of radiation and the need to make a diagnosis and plan treatment. Depending on the institution, frame rates ranging from 3 to 30 frames per second are used. Bonilha et al. described differences in judgments of swallow impairment between 30 frames per second and simulated 15 frames per second in a cohort of only 5 patients [5]. Further study on larger pediatric populations will be required to determine how to optimize exam sensitivity while limiting radiation exposure. Importantly, though a lower frame rate may be adequate to detect the presence of aspiration, a higher frame rate may be needed to determine why it occurred and what interventions could help address it.

Images need to be scrutinized for any of the following abnormalities: nasopharyngeal reflux, penetration (Fig. 5.3a), aspiration (Fig. 5.3b), intraesophageal/gastroesophageal reflux, and retrograde flow of contrast from the esophagus into the airway as with H-type tracheoesophageal fistula. It is also important to comment on adenoid or palatine tonsil hypertrophy (Fig. 5.4) as this can be another cause of noisy breathing or dysphagia. Lastly, as the trachea lies directly anterior to the esophagus, caliber change of the trachea due to tracheomalacia can be observed.

Esophagram

This exam is performed by a radiologist with the patient in the supine versus upright position depending on age. Images of the esophagus need to be obtained in both the AP and lateral dimensions and include the cervical esophagus through the gastroesophageal junction. It is preferable that the patient drink contrast via bottle, straw, or age-appropriate cup. The examination can, however, still be diagnostic by administering contrast via a syringe. If the patient is unable or unwilling to drink via those mechanisms, a feeding tube can be inserted into the proximal esophagus for injection of contrast. If there is a concern for esophageal perforation or anastomotic leak, water-soluble, low-osmolality contrast should be administered. High-osmolality water-soluble contrast such as gastrografin should be avoided as it can cause chemical pneumonitis when aspirated. All other patients can be given liquid barium. Esophageal caliber and motility should be commented on, as well as abnormal extrinsic mass effect caused by a vascular ring, sling, or mass. There are three normal impressions on the esophagus. First, the aorta should have an impression on the left lateral aspect of the upper thoracic esophagus in the AP view and an anterior impression on the lateral view. Second, an impression by the left main stem bronchus is variably seen sloping downward from right to left on the AP view. Third, on the lateral view, there is a gentle impression on the posterior wall of the esophagus by the left atrium (Fig. 5.5). Lastly, evaluation for gastroesophageal reflux should be performed. For infants and small children who cannot follow directions well, this is done by rolling the patient from side to side. Older children can be asked to cough or perform a Valsalva maneuver. That being said, the esophagram only captures a few moments in time and is not 100% sensitive for reflux.

Computed Tomographic (CT) Imaging

When performing CT to evaluate the upper aerodigestive tract in pediatric patients, intravenous contrast is always needed in order to delineate the soft tissues from the vascular structures. Anatomy and pathology will be more clearly identified in case surgery is indicated. When evaluating for a vascular ring or sling, only a single-phase study is indicated following injection of contrast. When the airway is being evaluated for malacia, vascular compression, or congenital abnormality, contrast-enhanced imaging is done with a two-phase scan – one in inspiration and one in expiration. Anesthesia has traditionally been needed to obtain adequate imaging in infants and small children who cannot hold their breath. An endotracheal tube cannot be used as it limits the ability to evaluate the trachea; however, satisfactory inspiratory and expiratory imaging can be done with a laryngeal mask airway.

With newer, wide-detector dynamic CT imaging, continuous low-dose scanning can be performed over the respiratory cycle, providing more physiologic evaluation of the airway during both inspiration and expiration without the need for anesthesia [6]. This allows for evaluation of children with noisy breathing or respiratory distress with a differential diagnosis including tracheobronchomalacia, vascular ring, and innominate artery compression syndrome.

Magnetic Resonance Imaging (MRI)

Newer techniques make it possible to image the large airways with MRI and evaluate for intrinsic large airway disorders such as tracheobronchial branching anomalies, tracheobronchomalacia, congenital stenosis, vascular rings and slings, intrinsic large airway neoplasms, and infectious disorders [7]; however, this has not yet become universal. Although older children can undergo this procedure with adequate coaching, special equipment including an MRI-compatible spirometer is required for dynamic imaging of the airway. Sedation is required for almost all patients under the age of 6 [7].

Another important application of MRI for evaluation of voice and swallowing disorders is the evaluation for an underlying Arnold-Chiari malformation. Arnold-Chiari malformation refers to the downward herniation of the hindbrain below the level of the foramen magnum [8]. Four subtypes are described, and types I and II are more commonly encountered. Type I is characterized by caudal descent of the cerebellar tonsils; symptoms may not arise until adulthood [9]. Type II involves herniation of the cerebellar vermis, medulla, and fourth ventricle, which may lead to hydrocephalus or myelomeningocele; symptoms are common in infancy [8]. Type III includes occipital encephalocele, and type IV is associated with cerebellar hypoplasia [8]. Importantly, patients with type I and II malformations may present with vocal fold mobility impairment and aspiration [10, 11]. MRI is the imaging modality of choice for diagnosis. Multiplanar T1- and T2-weighted images with a slice thickness less than 3 mm are recommended, covering the entire skull, brain, spine, spinal cord, and cerebrospinal fluid spaces [12]. Diagnostic criteria for type I malformation includes caudal displacement of one cerebellar tonsil >5 mm or both tonsils 3–5 mm below a virtual line connecting the basion with the opisthion of the foramen magnum [12] (Fig. 5.6). Importantly, some children with tonsillar displacement >5 mm may be asymptomatic [13], and others with displacement of only 3–4 mm may be symptomatic [14]; it is important to look not only at the tonsillar position but also whether the tonsils are compressed and the perimedullary cerebrospinal fluid spaces are effaced [12]. If a cause for vocal fold mobility impairment or aspiration cannot be identified based on history and exam, further investigation with MRI can be helpful.

Acute Disease Processes

Epiglottitis

Clinical Presentation and Etiology

Acute epiglottis is a medical emergency which requires prompt airway evaluation and management. This disease process is caused by infectious agents (Haemophilus influenzae, Staphylococcus aureus, β-hemolytic Streptococcus, Neisseria, and Streptococcus pneumoniae) or noninfectious agents (angioedema/anaphylaxis, trauma, or ingestion). Epiglottitis results in cellulitis, edema, and inflammation of the epiglottis and surrounding tissue (including the aryepiglottic folds and subglottis) [15, 16]. Children with epiglottitis usually present with acute, rapid-onset stridor, dysphagia, sore throat, fever, and respiratory distress. They typically assume the “tripod position,” sitting upright, leaning over with a hyperextended neck, and drooling. Prompt evaluation by otolaryngology and emergent intubation is the recommended initial treatment for acute epiglottitis [16]. Fortunately, vaccines have decreased the overall incidence of epiglottitis.

Radiographic Findings

Acute epiglottitis is often a clinical diagnosis which does not require imaging. That being said, lateral radiograph of the neck will demonstrate classic findings consistent with swelling of the epiglottis called the “thumb sign” (Fig. 5.7). Normally, the epiglottis has defined margins and the aryepiglottic fold is convex inferiorly. In acute epiglottitis, submucosal edema causes a thumb sign and narrowed vallecula [2, 17].

Retropharyngeal Abscess

Clinical Presentation and Etiology

Retropharyngeal abscesses occur in the neck between the posterior pharyngeal wall and prevertebral fascia along a chain of lymph nodes which drain the nasal cavity, adenoids, eustachian tubes, and posterior paranasal sinuses [18]. Abscesses are typically the result of suppuration of lymph nodes from an upper respiratory tract infection, but can also be seen after trauma, instrumentation, or ingestion of foreign bodies or caustic agents. Abscesses are typically polymicrobial and include respiratory anaerobes, Staphylococcus aureus, Haemophilus influenzae, and Streptococcus pneumoniae [2]. The incidence of retropharyngeal abscesses is most common in children under 5 years old [18]. Patients typically present with fever, neck pain, cervical lymphadenopathy, and dysphagia. Retropharyngeal abscesses are treated with supportive care, humidified oxygen, airway management, broad spectrum antibiotics, and possible incision and drainage [18].

Radiographic Findings

Upright and lateral radiographs will demonstrate thickening of the prevertebral soft tissues to >7 mm at C2 or >14 mm at C6 [18] (Fig. 5.8a). Contrast-enhanced CT is generally performed to confirm the diagnosis and assist with surgical planning (Fig. 5.8b). If cross-sectional imaging is obtained for preoperative planning or evaluation of complications, it should be extended to the mediastinum in order to evaluate for secondary mediastinitis [19].

In advanced disease, arterial and venous abnormalities may be seen on ultrasound or contrast-enhanced cross-sectional imaging, including jugular vein thrombosis (Lemierre’s syndrome) and pseudoaneurysm [2].

Croup

Clinical Presentation and Etiology

Croup (laryngotracheobronchitis) is a subglottic inflammatory process which affects approximately 3% of children and is caused by the parainfluenza virus in 75% of cases [20]. This infection is most common in children 6 months to 3 years old [21], but can be seen in older school-age children. Children present with respiratory distress and a barking cough. It is typically treated conservatively with oxygen, humidification, steroids, and nebulizers [20]. Croup is generally a clinical diagnosis, with imaging of the neck soft tissues or chest being performed only in those who are not appropriately responding to therapy which raises concern or additional pathology (foreign body, tracheitis, superimposed bacterial pneumonia).

Radiographic Findings

Plain film radiographs of the soft tissues of the neck are the diagnostic imaging modality of choice for croup [22]. In croup, the normal, smooth subglottic larynx will have an elevation and loss of lateral convexities, causing a classic steeple sign or inverted V sign on frontal radiographs and subglottic narrowing, hypopharynx overdistension, or increased subglottic density on lateral radiographs [2] (Fig. 5.9). The differential diagnosis for these radiographic findings would include angioedema and tracheitis depending on the clinical history.

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