4 Imaging of the Pediatric Head and Neck

Shelly I. Shiran


When evaluating head and neck pathology in children judicious use of imaging modalities can aid the physician with diagnosis, treatment planning, and follow-up. As in any aspect of caring for children, referring a child to imaging requires risk versus benefit assessment and avoiding unnecessary examinations.

Important Safety considerations include level of radiation exposure, need for sedation, and intravenous (IV) contrast related complications. The absence of ionizing radiation or need of sedation makes ultrasound (US) the initial imaging of choice for most cases of pediatric neck pathology.

A cross-sectional imaging study is indicated for either further assessment of an US diagnosed lesion or as initial evaluation for suspected skull base or facial pathology. When this is indicated a child may be referred to computed tomography (CT) study or magnetic resonance imaging (MRI) study depending on the diagnostic question. CT will be the initial study of choice in the setting of head trauma or cases of complicated sinusitis and mastoiditis where contrast injection is indicated. In the setting of suspected skull base or facial mass, referring a child to an MRI study for initial evaluation can be justified. It is important to note that in pathologies involving skull and facial bones MRI and CT studies have a complementary role.

4 Imaging of the Pediatric Head and Neck

4.1 Introduction

When evaluating head and neck pathology in children, the use of imaging modalities can aid the physician with diagnosis, treatment planning, and follow-up. Specifically, for the pediatric ENT surgeon, the use of imaging is crucial for surgery planning and for image-guided navigation systems. The modalities available for imaging the pediatric head and neck can be divided into two groups on the basis of related exposure of the patient to ionizing radiation. Radiography, fluoroscopy, CT and nuclear medicine (NM) studies all expose the imaged patient to different degrees of ionizing radiation; US and MRI do not.

When imaging children there are unique safety issues regarding radiation exposure and sedation, which differ from the adult population and need to be addressed when referring a child for a diagnostic study. In the following chapter, safety issues will be discussed, the different imaging modalities will be described, and the proper diagnostic workup will be recommended. 1 3

4.2 Pediatric Imaging Safety

4.2.1 Radiation Safety

In the last 20 years, following the increased usage of CT studies in medicine, there has been increased awareness of radiation burden from imaging studies especially in the pediatric population. 4 , 5 Children are more sensitive to radiation effect due to higher effective dose per delivered dose in a smaller patient compared to a larger patient (infant vs. adult), and due to a longer expected life span for carcinogenic changes to take place. This highlighted the importance of reducing the radiation exposure to children by adjusting the technique. 6 Since the society of pediatric radiology launched the “Image gently” campaign, 7 pediatric imaging centers adopted dedicated protocols adjusted to child’s size and age to reduce the delivered effective dose, in compliance with two major concepts:

  1. The linear, no-threshold model, which states that no level of radiation exposure is without risk.

  2. The ALARA (As Low As Reasonably Achievable) concept, where studies are performed with lowest radiation dose possible to still produce a diagnostic study. This has become an important guideline in pediatric radiology practice. 2

In recent years two large cohort studies were published that demonstrated relative increased risk for developing certain malignancies following diagnostic CT exposure in childhood. 8 , 9 These studies gained media attention and caused concern to parents. The main teaching points from these studies are that the relative increased risk per mGy of exposure is small but present, this relative increased risk is more substantial the younger the patient is at the time of exposure, especially below 5 years of age and that there is an accumulative effect from multiple studies. For sake of discussion, mGy is the measuring unit for radiation exposure and mSv is the measuring unit for effective dose (1 mSv = 1 mGy). Pearce et al 9 demonstrated excessive relative risk (ERR) of 0.023 per mGy (range 0.010–0.049) for brain tumors. However, for patients who received a cumulative dose of 50–74 mGy (mean dose 60.42 mGy) the ERR for developing brain cancer was 2.82 (1.33–6.03). In their study patients received 5 to 10 mGy per brain CT, which puts a child in relative increased risk to develop brain tumor after having 5 to 10 CT studies of the head. One should remember that these studies evaluated exposure to CT imaging prior to low-dose pediatric protocols adjustments. In an attempt to assess the impact of head and neck CT in children, Chen et al 10 reviewed the literature and found limited data regarding the effect of otolaryngological imaging (i.e., temporal bone, sinus, neck). In modern pediatric imaging facilities, the expected effective dose from a single brain CT is around 2 mSv and the expected dose from a facial or temporal bone CT is around 1 mSv. ▶ Table 4.1 lists the expected effective dose from additional common imaging studies. With these lower dose imaging protocols and by avoiding multiple repeat studies, the actual increased relative risk for the individual patient should be very small. In addition, advances in technology and post processing algorithms bring to the medical world new faster CT machines that will further decrease radiation exposure as these will become more prevalent in imaging facilities.

Table 4.1 Mean effective dose for patients from common pediatric radiology studies with correlation to effective dose from natural background radiation


Dose (mSv)

Time period for equivalent effective dose from natural background radiation

Chest PA radiograph


2.4 days

Skull lateral radiograph


2.4 days

Panoramic dental radiograph


1.8 days

Barium swallow


72 days

Head CT


240 days

Facial bones CT


120 days

Temporal bones CT


120 days



1800 days

4.2.2 Sedation

In recent years there have been experimental animal studies followed by retrospective population studies that raised concern regarding increased risk for neurodevelopmental pathology in children who were exposed to anesthetic substances in early infancy. To date, no scientific evidence is available to support a change in pediatric anesthesia practice, and the scientific community is awaiting results of large population prospective studies that are being performed. However, as young children need sedation for several imaging studies, this concern should be addressed. 11 Out of all imaging studies performed, the largest number of children requiring sedation is at the MRI suit. MRI is sensitive to motion artifact and a good quality MRI study requires cooperation of the patient with holding still for a substantial length of time, 20 to 60 min, depending on the type of study. For young children, this means that sedation is required; a child can be sedated with moderate sedation or general anesthesia depending on the child’s clinical condition and the anesthesiologist preference. Efforts to decrease the number of children requiring sedation for their MRI study include the development of motion-insensitive fast imaging sequences, as well as developing age-appropriate protocols.

It is possible to image neonates without sedation with proper feeding prior to the study, careful attention to noise and light reduction, using ear muffles, wrapping and swaddling the patients and keeping them warm. Infants and children up to 6-year-old usually require sedation. For children 6- to 10-year-old the ability to hold still may vary. In some pediatric imaging centers, a “test” study or a mock exam can be performed for each child prior to the scheduled study to decide whether sedation is needed. Using an MRI video and audio system, which creates a movie theater experience by wearing specialized goggles, can further decrease the need for sedation. Sedation is also needed for non-cooperative children undergoing a CT study, though these are much shorter studies in the range of a few minutes. Future newer faster CT scanners may obliviate the need for sedation completely. Additional studies that may require sedation are PET-CT and interventional radiology procedures.

4.3 The Imaging Modalities

4.3.1 Ultrasound

The absence of ionizing radiation or need of sedation makes US the initial imaging of choice for most cases of pediatric neck pathology that require additional evaluation to supplement the physical exam. US is an imaging modality based on detection and display of acoustic energy reflected from interfaces within the body. On US, fluid is hypoechoic (dark) with through-transmission, fat is hyperechoic (bright), air and bone will create acoustic shadowing, eliminating evaluation of deeper structures (▶ Fig. 4.1a). An US study may be sufficient for diagnosis, especially in evaluation of a focal mass, parotid space lesions (▶ Fig. 4.2a), or thyroid pathology. 12 In addition to US a Doppler study can be obtained that will add information regarding vascularity of a focal lesion (▶ Fig. 4.1a and ▶ Fig. 4.2b) and patency of the carotid sheath vessels. US is an excellent method for guiding procedures such as fine needle aspiration (FNA) (▶ Fig. 4.2c) or abscess drainage.

Fig. 4.1 A 2-year-old girl presented with left submandibular swelling. A US study (a) demonstrates a multilobulated space-occupying lesion of low echogenicity consistent with fluid. Increased echogenicity in soft tissue deep into the lesion compared to soft tissue anterior to the lesion is related to enhanced through-transmission typical to fluid. The dark regions (*) on both sides of the image are related to acoustic shadowing from mandible (arrows). A US-Doppler study (b) demonstrates no flow within the lesion. The findings are consistent with a lymphatic malformation.
Fig. 4.2 A 10-year-old girl presented with a right-sided parotid focal mass. A US study (a) demonstrates a focal, round, space-occupying lesion which is hypoechoic compared to normal parotid tissue (*). A US-Doppler study (b) demonstrated increased vascularity within the lesion. A US-guided fine needle biopsy was performed, with the needle appearing as a linear hyperechoic structure with acoustic shadowing, positioned within the lesion (c). Pleomorphic adenoma was diagnosed.

It is also a preferred method for following progression or regression of a lesion. When a diffuse pathologic process is evaluated, US may not be able to assess the full extent and additional cross-sectional imaging, such as CT or MRI, will be needed. This is especially important for processes extending towards skull base, as US cannot penetrate the skull base bone, and for lesions involving retropharyngeal space or extending into the mediastinum (▶ Fig. 4.3).

Fig. 4.3 A 4-week-old infant had feeding difficulties and left neck swelling. A US study (a) demonstrated a large cystic mass in the left neck with internal low-level echoes which reflect complicated fluid. The mass extended to the retropharyngeal space (arrow) displacing the trachea (*), which can be recognized by the echogenic artifact of air within it. There was also mass effect and displacement of the thyroid gland (short arrows). A US-Doppler study (b) demonstrated no internal vascularity. The left carotid sheath vessels were effaced and displaced laterally and posteriorly (arrow). To evaluate the full extent of this space-occupying lesion and to better characterize it, an MRI study was performed ▶ Fig. 4.15).

In recent years US has gained popularity as a bedside tool in the hand of the emergency room or ICU physician for point-of-care US; this may serve for assessing intubation tube placement. 13 Studies published in recent years are suggesting expanding US interrogation of the neck to include assessment of laryngeal structures, as the vocal cords can be assessed in children through the uncalcified cartilage (▶ Fig. 4.4), and assessment of tonsillar and peritonsillar infections (▶ Fig. 4.5).

Fig. 4.4 Mid-axial US image at the level of the glottis in an 8-year-old boy. The thyroid cartilage has an inverse V shape and hyperechoic margins (1). Anterior to the thyroid cartilage the anterior superficial muscles of the neck are visible (2). Deep to the thyroid cartilage the paraglottic fat is hyperechoic (3), the muscles and process of the true vocal cords are relative hypoechoic (4). The arytenoids are seen as two triangular structures deep into the vocal folds (*).
Fig. 4.5 An 18-month-old child with fever, torticollis, and enlarged lymph nodes on physical examination. A US study was performed to assess for lymphadenitis. The US study demonstrated enlarged reactive lymph nodes in the left neck without areas of necrosis (a). Deep to the carotid space a hypoechoic oval lesion was demonstrated with increased echogenicity of the adjacent fat (b) and no internal vascularity on Doppler study (c) suspected for a retropharyngeal abscess. A contrast-enhanced CT study was performed; an axial image at the level of the oropharynx (d) and a sagittal reformat image (e) demonstrate a retropharyngeal phlegmon involving nasopharyngeal and oropharyngeal spaces on the left with central hypodensity consistent with abscess formation. There is mild airway effacement (arrow on d) and extensive enlargement of lymph nodes in the left neck (d).

In the adult literature, the use of contrast-enhanced US of the neck is being evaluated for differentiating benign from malignant thyroid nodules or lymph nodes; this may expand to the pediatric population in the future.

The main limitation of US is that the quality of the study and related interpretation depends on the skills of the examiner; it is advisable to have children examined by specifically trained personnel.

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Feb 8, 2021 | Posted by in HEAD AND NECK SURGERY | Comments Off on 4 Imaging of the Pediatric Head and Neck
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