Ultrasound, as a diagnostic modality, has been developing rapidly. High-resolution ultrasound machines have been reduced to the size of a laptop computer. Ultrasound can be adopted by otolaryngologists for use within the clinic and the operating room. Ultrasound offers several advantages to the pediatric patient population. It is well tolerated and adds a degree of precision to the physical examination. It can be done repeatedly as lesions evolve and treatment is performed. It is valuable for guidance and therapeutic treatment of lesions in the operating room. It is likely that ultrasound use will continue to rapidly grow and evolve as a tool within the field of otolaryngology.
Advantages of office imaging studies of the head and neck in children
Diagnostic imaging studies of the head and neck in children have three main challenges. First, pediatric conditions that require imaging are often dynamic and changing. Examples include lymphadenopathy, deep neck space infections, and vascular malformations. Although an initial imaging study can offer a great deal of information, it remains a snapshot in time and does not offer the physician insight beyond a narrow period. Many pediatric lesions quickly evolve over days or weeks, making remote imaging less relevant. Also, virtually all pediatric imaging is done outside the otolaryngology clinic. This not only requires additional logistics but also is accompanied by an interruption in care. In most major medical centers, imaging is scheduled hours, days, or weeks after the initial clinic visit. Once completed, the study must be conveyed back to the managing provider for review and decision making. Finally, many pediatric imaging studies require sedation or even general anesthesia for adequate information to be gained. This adds further logistical challenges to the health care team and poses additional risk to the patient.
In selected cases, directed ultrasound has the potential to solve all three of these major issues. Ultrasound devices are now portable enough to be brought directly to the operating room, clinic examination room, or bedside and can be used by a radiologist or otolaryngologist with little preparation. Examinations are usually completed in minutes, can frequently be performed during the initial consultation, and are well tolerated in most children. With no need for radiation exposure, intravenous medication, or sedation, it can be repeated as often as needed rather than offering a single snap-shot of the lesion in question; ultrasound can be repeatedly used to track the evolution of lesions before, sometimes during, and after treatment.
Pediatric head and neck ultrasound uses the same hardware used in adult applications. No additional supplies are needed. Machines range in size from moderate-sized carts to laptop versions that are placed on wheeled stands. Each of the machines fit into a standard size examination room and, with battery backup, can be moved between treatment areas without interruption. Image storage varies between machines and ranges across the standard data formats and, depending on hospital archive systems, may or may not be available throughout the hospital. Although many probe types exist, a single high-frequency linear probe, 8 to 15 MHz, is adequate for most applications in otolaryngology. Specific courses in pediatric ultrasound for otolaryngologists do not yet exist. Despite this lack, current course offerings dealing with adult ultrasound are offered to otolaryngologists through the American College of Surgeons. Techniques reviewed and evaluated at these training events are highly relevant to pediatric applications. Along with outside training, partnership with one’s own radiology team is indispensable for advice and training as comfort is gained with the basic examination and techniques.
Specific applications of ultrasound in the otolarngology clinic
Lymphadenopathy
Evaluation of lymphadenopathy in children can quickly be accomplished with ultrasound. In the authors’ clinic, ultrasound has evolved to become a natural extension of the physical examination. Although palpation of lymphadenopathy in most children is simple, accurate sizing of lymph nodes and diagnosis of multiple contiguous nodes is often difficult. Overlying tissue frequently adds to the perceived size of the lymph nodes. Ultrasound offers solutions to both problems. With a brief imaging examination done to enhance palpation, the location of the lymphadenopathy is quickly determined. Precise sizing can be performed with digital calipers. Specific nodal architecture can often be visualized. Normal or reactive lymph nodes should typically be well defined and elliptical in shape. Their parenchyma should be homogeneously hypoechoic with a central linear-hyperechoic vascular hilum ( Fig. 1 ). Although no ultrasound findings have been strongly correlated with neoplasm, concerns for malignancy arise with loss of the normal architecture, loss of the kidney bean shape to a more bulbous or round shape, absent hilum, irregular borders, cystic necrosis, and irregular capsular vasculature. With baseline data established during initial consultation, children can be monitored with serial ultrasound examinations while undergoing medical evaluation and treatment. Any nodes that remain enlarged or demonstrate multiple abnormal findings despite treatment can be documented and targeted for excisional biopsy as indicated.
Branchial Cleft Anomalies and Thyroglossal Duct Cysts
Ultrasound can be used to evaluate branchial cleft anomalies and thyroglossal duct cysts ( Figs. 2 and 3 ). In each case, cysts often present as thin-walled ovoid or round masses with significant heterogeneity and a lack of vascular architecture. Because 90% of branchial cleft cysts have origins in the second arch, most are frequently confirmed to be anterior to the sternocleidomastoid whereas thyroglossal duct cysts are most frequently localized within or in close proximity to the strap musculature. Thyroglossal duct cysts can, in rare circumstances, represent ectopic thyroid tissue. Confirmation of normal thyroid architecture below the mass in question is recommended before surgery is undertaken. Ultrasound can easily accomplish this task during the same examination done for mass evaluation.
Vascular and Lymphatic Malformations
Vascular and lymphatic malformations are both amenable to ultrasound evaluation. Although various classification schemes exist, mixed lesions are possible and, in the authors’ opinion, more frequent than often reported. Purely lymphatic malformations are often encountered in the posterior cervical space and within the oral cavity. Ultrasound examination demonstrates cysts with variable thickness to their septa and heterogeneous fluid levels within ( Fig. 4 ). Ultrasound examination can rapidly define microcystic disease from macrocystic elements. Doppler color flow examination is invaluable in this setting and quickly confirms lack of significant blood flow. Finding significant random blood flow patterns within a lesion provides evidence for a vascular or mixed lesion ( Fig. 5 ). Flow rates within these lesions can be subjectively observed and low-flow versus high-flow status can be seen in real time.
Abscesses
Ultrasound can be used to evaluate possible abscess formation. Classically, deep neck space infections have been limited to expansion within potential spaces and limited by fascial planes. With the advent of methicillin-resistant Staphylococcus aureus , otolaryngologists have begun to see more cases of superficial cellulitis lead to abscesss formation. These superficial absecesses with overlying cellulitis are often difficult to examine by palpation alone. Ultrasound again offers an augmentation of the physical examination in these situations and can quickly identify the border between soft tissue and the pus within an abscess cavity. Needle localization with or without excision and drainage can follow and total evacuation of the cavity can be confirmed.
Other Applications
Many other clinical applications for diagnostic ultrasound have been reported in the pediatric population. Infants born with an anterior neck mass and torticollis can be evaluated for pseudotumor of infancy with ultrasound alone ( Fig. 6 ). This modality can be used in the clinic to obviate CT or MRI evaluation. Laryngeal studies in children have been undertaken to assess dynamic vocal cord function and papilloma status in patients with known disease. Thyroid mass evaluation can be performed in children as it is done in adults. Finally, ultrasonography has even been found to be an accurate method of confirming middle ear fluid and further defining the viscosity of the effusion.
