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| ORIGINAL ARTICLE |
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| Year : 2014 | Volume
: 4
| Issue : 1 | Page : 2-5 |
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Laryngeal ultrasound in diagnosis of vocal cord palsy: An underutilized tool?
Inita R Matta1, Kanupriya B Halan1, Ramesh H Agrawal2, Mandar S Kalwari2
1 Department of ENT, Mumbai Port Trust Hospital, Mumbai, Maharashtra, India
2 Department of Radiology, Mumbai Port Trust Hospital, Mumbai, Maharashtra, India
| Date of Web Publication | 22-Sep-2014 |
Correspondence Address:
Kanupriya B Halan
C901 Sanjeev Enclave, Seven Bungalows, Andheri (w), Mumbai - 400 061, Maharashtra
India
 Source of Support: None, Conflict of Interest: None  | Check |
DOI: 10.4103/2230-9748.141439
 Abstract | | |
Background: Despite the prevalence of ultrasonography in medical practice, its use in laryngeal disorders appears underutilized. It provides a simple, easy, cheap and non-invasive method to diagnose vocal cord palsy in real time, dynamic 2 or 3-dimensional image mode. It can be an alternative diagnostic tool where flexible fibreoptic laryngoscopy is limited by an uncooperative patient, xylocaine sensitivity or where stroboscopy is not available due to cost restraints. Especially it is useful in the preoperative workup of a patient undergoing thyroid surgery. Aims: The present study evaluates the accuracy of ultrasonography in diagnosis of vocal cord palsy in 25 patients. We have used fibreoptic laryngoscopy purely as a comparative tool for purposes of this study. Materials and Methods: It was a prospective study carried out in 25 patients presenting with hoarseness. Patients underwent laryngeal ultrasound followed by flexible fibreoptic laryngoscopy. Results: We were able to accurately diagnose vocal cord palsy by ultrasound in all but two patients where the examination was limited by extensive laryngeal cartilage calcification. Discussion and Conclusion: There is every evidence to suggest that ultrasonography has a place in diagnosis of vocal cord palsies. It is easy, cheap, available, and non-invasive. It is a useful tool where fibreoptic laryngoscopy is limited by an uncooperative patient and where strobolaryngoscopy is not available. Further study and more familiarity would extend its use to other laryngeal disorders. Keywords: Echolaryngography, ultrasound larynx, vocal cord palsy
How to cite this article:
Matta IR, Halan KB, Agrawal RH, Kalwari MS. Laryngeal ultrasound in diagnosis of vocal cord palsy: An underutilized tool?
. J Laryngol Voice 2014;4:2-5 |
| INTRoDUCTION | |  |
Ultrasound imaging is used widely and effectively in head and neck as a diagnostic modality. [1] In laryngeal disorders, it's use spans over two decades. However, though it is radiation free, simple, easily available and cost-effective, ultrasonography or echography of the larynx is not yet a well established modality. Though stroboscopy and flexible laryngoscopy have become the benchmark of laryngeal diagnosis, the cost of the former and limitations of both especially in children and patients with a pronounced gag reflex remain. Ultrasonography of the larynx would then be a viable alternative in these patients and in pregnant women where even application of topical anesthesia in the throat may be a consideration. Since it does not interfere with vocal cord vibration, it seems a useful way to assess vocal fold mobility disorders Also since patients with thyroid disorders do undergo ultrasound examination as part of their workup, the cords can be assessed at the same time, translating into effective cost saving. The reporting of 100% diagnostic accuracy by Tarek Khalil for diagnosis of vocal cord mobility by ultrasound are noteworthy and encourage further research. [2]
| Materials and methods | | |
This prospective study was conducted over a period of 15 months in the ENT department of our hospital on a total of 25 patients with hoarseness related to vocal cord palsy. Patients underwent both, laryngeal ultrasound to visualize vocal cord mobility, followed by flexible fibreoptic laryngoscopy which was done as a confirmatory diagnostic measure to correlate ultrasound findings for the purpose of this study. Patients with head and neck anatomical pathologies with unpredictable effects on the ultrasound assessment of vocal folds were excluded from the study. A medical high resolution ultrasound scanner (HDI-5000, Philips Medical Ultrasound, Bothell, Washington, USA) with linear and curvilinear probes of frequencies 5-12 MHz and 2-5 MHz, respectively, was used. B mode was used to record images throughout.
The study was approved by the hospital's ethics committee and all enrolled subjects gave written informed consent prior to being investigated. Laryngeal ultrasound was performed with a linear or curvilinear probe. The patient was placed supine with neck extended. The thyroid cartilage was identified by palpation and the probe was moved superiorly and inferiorly till different laryngeal structures were visualized. The glottis was visualized at or near the midpoint of the distance between the thyroid notch and inferior border of the thyroid cartilage. The ultrasound was done in two phases
- Quiet breathing
- During phonation, to allow accurate assessment of vocal cord mobility in its lateral and medial excursions [Figure 1], [Figure 2].
| Results | | |
This study was conducted in 25 patients attending the ENT outpatient clinic at our hospital, 14 of which were male adults (of which 5 were above 50 years of age), 9 were female adults and 2 children. We were able to accurately diagnose vocal cord palsy by ultrasound in all but two patients where the examination was limited by extensive laryngeal cartilage calcification. All patients underwent flexible fibreoptic laryngoscopic examination as a ''control check'' for the purpose of this study. Findings of ultrasound were congruent with those of laryngoscopy [Table 1]. | Table 1: Patients' findings of vocal cord ultrasound compared with fibreoptic laryngoscopy
Click here to view |
| Discussion | | |
Ultrasonic imaging depends on reflection of sound from tissues of varying acoustic properties back into the transducer. [3]
Visualization of the laryngeal interior commenced when Manuel Garcia saw his own vocal cords with a dental mirror in 1854. [4] The fibreoptic laryngoscope was introduced only in 1976 and has since undergone refinements in optics and illumination. [5] Today laryngostroboscopy is the clinical gold standard for assessment of phonatory and valvular functions of the glottis. [6],[7],[8],[9],[10],[11] Flexible laryngoscopy and stroboscopy (with rigid endoscopes) however do suffer some limitations imposed by a sensitive gag reflex or neck and jaw rigidity. Children too may not be good candidates. [6],[12] The flexible laryngoscope also has the problem of ''barreling''. [13] Stroboscopy entails a costly equipment and is not widely available even in major cities.
Ultrasonography has been used for diagnosing laryngeal disorders since 1960. [14] Tamura et al. in 1973, discovered echoes from the free margins of the vocal cords. [15] Noyek in 1977 established effective visualization of the larynx by ultrasonography. [16] By late 1980s ultrasound was used for visualization of true cord mobility. [17],[18] In 2007, Huang et al. reported on the use of ultrasound in the frequency of 10-30 MHz in the diagnosis of vocal cord disorders. [19] Vats et al. stressed the use of laryngeal ultrasound to diagnose vocal fold paralysis in children due to its non-invasive nature. [20] Hannavi et al. cited ultrasound as the modality of choice for bilateral vocal cord paralysis. [21] Tarek Khalil found a 100% sensitivity and specificity in diagnosis of vocal cord mobility with ultrasonography. [2]
As mentioned earlier, patients with thyroid disorders do undergo ultrasound as part of their clinical work-up and as a preoperative measure. Cord mobility can be seen with the ultrasound at the same sitting. The convenience, simplicity and cost-effectiveness of this cannot be stressed enough. [22],[23]
Hirano's path breaking "cover- body" theory of vocal fold structure elucidated the mechanical properties of various layers of the true vocal cord. [24] The ''cover'' is the main vibratory layer with a frequency of > 70 Hz and the wave travels vertically from lower to upper cord margin. [25] This body motion cannot be seen by simple endoscopy but if the ultrasound frequency is properly tuned, a slow motion montage of vocal cord vibration may be obtained. [26] Ultrasound of the larynx is based on 3 levels, namely supraglottic, glottis and subglottic. [27] Garel further showed that the cords are seen as triangular, hypoechoeic structures with their apex lying behind the reentrant area of the thyroid lamina and their bases inserted on the hyperechoeic arytenoid vocal process. The muscular part of the cords is responsible for their echogenicity. The false cords are hyperchoeic due to their fatty content and mucous glands. [17] Hino reported on the use of B mode image in ultrasonography to see vocal fold vibration. [28] Grunert et al. were able to get a good functional diagnosis of the cords by sonography. [29]
Raghavendra et al. used the thyroid cartilage as an acoustic window to see the vocal cords. The latter appeared hypoechoeic and more importantly, their movements were visible in "real time" and representative of normal respiration. [17] Chen Gia Tsai in 2009 noted the hypoechoeic nature of Reinke's space due to its high water content. The vocal ligament and vocalis muscle could be discerned just underneath this. The white line in the B mode is due to air mucosa interface of the laryngeal lumen. This was our finding also. Though the larynx has air conduits within, which could act as a sound barrier, the strap muscles and paraglottic tissues transmit ultrasound well to the cords and arytenoid area. [26] As noted by Wang et al., the sharp angle of the thyroid cartilage could be overcome by proper application of ultrasound gel. The thyroid gland, even if enlarged, provides a good medium for ultrasound waves to travel. [22]
Considering the widespread use of ultrasound in the rest of the body and also in the head and neck, its use in laryngeal disorders remains relatively unexplored. This may be due to acoustic extinction caused by calcification of laryngeal cartilages. [27],[30],[31],[32]
Recent studies have employed an oblique transverse plane bisecting the epiglottis and posterior most part of the cords thus bypassing the ossified thyroid cartilage. [33] However, in children, women and young males ossification of the thyroid cartilage does not pose a problem.
The ultrasound has the obvious advantage of being radiation free, painless, non-invasive, cheap, available in almost every institution, is easily reproducible, portable, convenient in children and safe in pregnancy. [34],[35] Moreover, no anesthesia is needed with this modality in pediatric use. [36]
As proficiency and familiarity with laryngeal ultrasound increases, the indications may be extended to subglottic stenosis, post extubation stridor, laryngeal tumors, epiglottitis, laryngeal papillomatosis etc., Further modifications like the concave ultrasound probe would improve diagnosis. [33]
Otolaryngologists possess extensive knowledge of head and neck and an added familiarity with ultrasound of this region, particularly the larynx could provide the specialty with a cheap yet powerful diagnostic tool. [37]
| Conclusion | | |
Laryngeal ultrasonography or "Echolaryngography" seems to be a simple, easy, cheap, non-invasive, easily available tool with no radiation exposure concerns. [18] Limited to some extent in males over 55 years due to thyroid cartilage calcification, it is nevertheless useful in children, women and young adult males. Moreover, ultrasound imaging observes vocal cord movement in normal phonation with no need for the patient to stress. Most thyroid patients undergo a preoperative sonographic examination of the neck and cord movement can be assessed in the same sitting. Calcification of the thyroid cartilage in older males may limit glottis view but advancement in probe design and machine technology may overcome this in the future. More familiarity with this method would allow ultrasound to be extended to other benign and neoplastic disorders of the larynx. It can prove to be a useful and accurate diagnostic aid where fibreoptic laryngoscopy is limited by an uncooperative patient or one with sensitivity to topical xylocaine and where stroboscopy is not available.
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[Figure 1], [Figure 2]
[Table 1]
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