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Small Parts - ENT Ultrasound Applications

Quick Image Reference

Illustration 1: Overview of neck anatomy.

Illustration 2: Cross sectional anatomy.

Figure 1: Image of a peritonsillar abscess.

Illustration 3: Appearance of peritonsillar abscess.

Figure 2: A needle (yellow) is seen inserting into the abscess cavity for drainage.

Figure 3: Odontogenic facial abscess with anechoic, hyperechoic (gas) and isoechoic material within the abscess cavity (circled).

Figure 4: Color Doppler sonogram showing enlarged cervical lymph node (yellow) with vascularity suggesting lymphadenitis (shown with red in color Doppler window).

 

 

Srikar R. Adhikari, M.D., RDMS

I.  Introduction and Indications

Ear, nose and throat related complaints are a common cause of visits to the emergency department. ENT emergencies include a wide variety of conditions such as pharyngitis, tonsillitis, peritonsillar abscesses, retropharyngeal abscesses, dental abscesses, and facial fractures.  Patients typically present with pain, odynophagia, hoarseness, facial or neck swelling.  Ultrasound is a useful adjunct for the clinical evaluation of ENT emergencies as clinical findings can be misleading.  Patients who present with an obvious cellulitis may have an underlying abscess, which may be missed.  Ultrasound has emerged as a valuable diagnostic tool for the evaluation of these conditions and is being used in the emergency room to assist with diagnosis, localization and therapeutic management. In a patient with a subcutaneous mass, it can determine whether the mass is cystic, solid or complex, in turn successfully differentiating between adenitis, cellulitis and abscess. (2,4,5) Ultrasound is also of considerable value in the diagnosis of nasal fractures, midfacial fractures, and orbital fractures in the setting of facial trauma.

Indications:

  1. Odynophagia/dysphagia
  2. Facial swelling
  3. Neck masses
  4. Facial trauma

II.  Anatomy

Illustration 1:  Overview of neck anatomy.

 

Illustration 2: Cross sectional anatomy.

III.  Scanning Technique and Normal Findings

A 7.5 to 10 MHz linear transducer, which has low penetration but high resolution is used to examine areas of facial and neck swelling. The area of concern is usually visualized in at least two planes, typically the longitudinal and transverse planes. If an abscess is identified, one should try to identify adjacent structures, such as vessels, nerves and lymph nodes in an effort to avoid them while draining the abscess. The depth of the abscess should also be noted. Most of the ultrasound machines have markers on the side of the screen, which indicate the depth of the area being visualized.  In the setting of a very superficial abscess, an acoustic standoff pad can be used to improve image resolution.

IV. Pathology

Peritonsillar Abscess
Ultrasonography is a valuable tool in the assessment and management of suspected peritonsillar abscess (PTA).  A peritonsillar abscess is the most common deep infection of the face and neck.  It typically begins as tonsillitis, which then progresses to peritonsillar cellulitis, which in turn may develop into a peritonsillar abscess.  Peritonsillar cellulitis is generally treated with analgesics and antibiotics whereas a peritonsillar abscess usually requires definitive therapy, i.e. aspiration or incision and drainage.  Clinical differentiation of peritonsillar abscess from peritonsillar cellulitis can be difficult.  The traditional management has been to perform a diagnostic needle aspiration of the tonsillar fossa.  Blind needle aspiration carries with it serious complications such as inadvertent puncture of the carotid artery, jugular vein or parotid gland. In addition, blind needle aspiration has a reported false-negative rate of 10-24 %.  The use of intraoral ultrasonography in the diagnosis of PTA has been well established.   It is non-invasive and rapidly performed at the bedside in the emergency department.   In the setting of a PTA, it provides means for guided aspiration.  A 5.0 to 10.0 MHz curved array endovaginal probe is utilized for intraoral ultrasound.  It is covered with either a glove or condom and placed into the oral cavity over the area in question.  Pre-application of a topical anesthetic spray is recommended to reduce gagging and overcome trismus.  During the ultrasound evaluation of a PTA, the carotid artery and its relationship to the abscess cavity should be identified (Figure 1).  It is generally located posterolateral to the tonsil and within 5-25 mm of a PTA.  Sonographically, the internal carotid artery is identified by its anechoic and tubular shape.  Its location should be evident with systematic scanning of the peritonsillar area in both sagittal and transverse planes.  A peritonsillar abscess most commonly appears as a hypoechoic or complex cystic mass.  For aspiration, an 18 gauge, 2-inch needle can be inserted adjacent to the probe head and directed into the abscess cavity under ultrasound guidance (Figure 2).  The ability to simultaneously image and introduce the needle allows the emergency physician to track the entire course of needle and prevent the complications such as puncturing the carotid artery. (1,2,4)

Figure 1:  Image of a peritonsillar abscess.  A complex mass with mixed echogenicity is visualized.  Note the vessels posterior to the mass. (Courtesy of Michael Blaivas, M.D.)

Illustration 3: Appearance of peritonsillar abscess.

Figure 2:  A needle (yellow) is seen inserting into the abscess cavity for drainage.  (Courtesy of Michael Blaivas, M.D.)

Facial Abscess
Ultrasound has been found to be of value in the diagnosis and treatment of odontogenic facial abscesses.  It is an effective tool in both confirming abscess formation in the superficial facial spaces and detecting the stage of infection.  Ultrasound can separate solid from fluid masses and determine the size and depth of the area of concern while revealing adjacent vital structures such arteries, veins and nerves.  This objective identification can assist in incision and drainage while helping to avoid serious complications.  It is important to note that abscesses can have a variety of sonographic appearances.  The most common appearance of is that of a mass that is hypoechoic or anechoic relative to adjacent structures.   They can also appear as complex masses with scattered echoes representing necrotic debris, septae or gas  (Figure 3).  Color Doppler may show hyperemia adjacent to the abscess cavity and absence of flow within it.  Once the abscess is identified, ultrasound can be used to drain the abscess in real-time.  It not only allows for visualization of the needle or scalpel but also provides a means to ensure the abscess cavity been adequately drained.

Figure 3:  Odontogenic facial abscess with anechoic, hyperechoic (gas) and isoechoic material within the abscess cavity (circled).  Posterior acoustic enhancement is also present.  (Courtesy of Michael Blaivas, M.D.)

Lymphadenitis
Ultrasound is a useful imaging modality in the assessment of neck masses. (3,6)  It can differentiate between abscess and cervical lymphadenitis. Both gray scale and power Doppler sonographic features are helpful in differentiating neck masses.  Useful gray scale features include size, shape, echogenicity, intranodal necrosis, and calcification.  Important power Doppler features include the presence of a vascular pattern and the displacement of vascularity.  Recent literature has indicated the possibility of differentiating benign from metastatic lymph nodes by observing the vascular patterns on color or Doppler sonography.(7) Normal reactive lymph nodes are predominantly hypoechoic when compared with the surrounding structures.  Lymphadenitis appears as a hypoechoic mass with hilar vascularity present on color Doppler (Figure 4), whereas an abscess cavity has an absence of flow.

Figure 4:  Color Doppler sonogram showing enlarged cervical lymph node (yellow) with vascularity suggesting lymphadenitis (shown with red in color Doppler window).  (Courtesy of Michael Blaivas, M.D.)

V.  Pearls and Pitfalls

  • Improved visualization of neck anatomy can be achieved by placing the patient supine with neck in mild hyperextension.
  • Begin scanning with highest frequency possible/available for best resolution.
  • Failure to identify vascular structures before PTA or any abscess drainage carries a higher risk of complications.
  • Cystic and complex thyroid nodules can appear similar to an abscess.
  • A rare differential diagnosis of an abscess found in the neck is a fluid filled cyst formed by the thyroglossal duct or branchial cleft.  Use your clinical judgment, Doppler evaluation and additional imaging before attempting incision and drainage.

 

VI.  References

  1. Blaivas M, Theodoro D, Duggal S.
    Ultrasound-guided drainage of peritonsillar abscess by the emergency physician. Am J Emerg Med.2003;21:155-158.

  2. Lyon M, Blaivas M.
    Intraoral ultrasound in the diagnosis and treatment of suspected peritonsillar abscess in the emergency department. Acad Emerg Med.2005;12:85-88.

  3. Ying M, Ahuja A, Brook F, Metreweli C.
    Vascularity and grey-scale sonographic features of normal cervical lymph nodes: variations with nodal size. Clin Radiol.2001;56:416-419.

  4. Dewitz A.
    Soft tissue applications. In: Ma OJ, Mateer J, eds. Emergency Ultrasound. New York: McGraw-Hill,2003:385.

  5. Promes M.
    Miscellaneous applications. In: Simon B, Snoey E, eds. Ultrasound in Emergency and Ambulatory Medicine. St. Louis: Mosby,1997:250.

  6. Peleg M, Heyman Z, Ardekian L, Taicher S.
    The use of ultrasonography as a diagnostic tool for superficial facial space infections. J Oral Maxillofac Surg.1998;56(10):1129-31; discussion 1132.

  7. Na D, Lim H, Byun HS, Kim HD, Ko YH, Baek JH.
    Differential diagnosis of cervical lymphadenopathy: usefulness of color Doppler sonography. Am J Roentgenol.1997;168:1311-1316.

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