Original Research
Use of Ultrasonography to Locate Laryngeal Structures for Laryngeal Electromyography Han Gil Seo, MD, Hye Jin Jang, MD, Byung-Mo Oh, MD, PhD, Won Kim, MD, Tai Ryoon Han, MD, PhD Objective: To measure the representative anatomic landmarks for laryngeal electromyography (LEMG) and to delineate an accurate ultrasonography-guided approach. Design: A retrospective study. Setting: A university hospital. Participants: A total of 518 patients (270 men and 248 women) who underwent LEMG. Methods: The medical records, LEMG records, and ultrasonographic measurements of the patients who underwent LEMG in our electromyography laboratory between March 2010 and January 2013 were reviewed. Main Outcome Measurement: The longest dimension of the cricothyroid membrane, the height of the arch of the cricoid cartilage, and the distance from the superior border of the cricoid cartilage to the midpoint of the vocal fold were measured by using ultrasonography. Results: A total of 585 studies in 518 patients with a standard deviation (SD) mean age of 56.01 14.36 years (men, 59.28 14.09 years; women, 52.45 13.81 years) were reviewed. The most common etiology was surgery (44.6%), and the left side (56%) of the vocal folds was more frequently involved than the right side (23.4%) or both sides (9.4%). The longest dimension of the cricothyroid membrane, height of the arch of the cricoid cartilage, and distance from the superior border of the cricoid cartilage to the midpoint of the vocal fold measured 1.06 0.33 cm (men, 1.16 0.34 cm; women, 0.97 0.29 cm), 0.83 0.24 cm (men, 0.88 0.24 cm; women, 0.77 23 cm), and 1.88 0.48 cm (men, 2.09 0.51 cm; women, 1.70 0.36 cm), respectively. All measurements differed significantly between the men and women (P < .001 by Student t test). Conclusions: The current study provides reference ranges for ultrasonographic measurements of important anatomic landmarks for LEMG. This study also provides a technique for using ultrasonography in LEMG. Ultrasonography may be used as an adjuvant to overcome certain technical pitfalls of LEMG. PM R 2014;-:1-6
INTRODUCTION Laryngeal electromyography (LEMG) is used in laryngologic assessment as well as the diagnosis and treatment of voice disorders. Since its introduction in 1944, LEMG has been used to investigate the roles of the laryngeal muscles in voice production and laryngeal biomechanics. During the 1980s and 1990s, LEMG evolved into a valuable adjunct to laryngeal evaluation and became widely used in clinical practice [1,2]. Results of recent studies showed that LEMG is also useful in the diagnosis and treatment of vocal fold problems [3-5]. However, evidence-based reviews have reported that the positive evidence for LEMG was lacking and that additional prospective studies were still needed to assess its diagnostic accuracy and clinical utility [2,6]. Needle electromyography (EMG) of the muscles responsible for phonation is technically demanding. The challenges include the inability to directly visualize or to palpate the muscles of interest, the extreme thinness of the muscles, the need to identify anatomic landmarks by palpating the laryngeal structures, and patient discomfort [7]. The accuracy PM&R 1934-1482/13/$36.00 Printed in U.S.A.
H.G.S. Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea Disclosure: nothing to disclose H.J.J. Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea Disclosure: nothing to disclose B.-M.O. Department of Rehabilitation Medicine, Seoul National University, College of Medicine, Seoul National University Hospital, 101 Daehak-Ro, Jongno-Gu, Seoul 110-744, Republic of Korea. Address correspondence to: B.-M.O.; e-mail: [email protected] Disclosure: nothing to disclose W.K. Asan Medical Center, Department of Rehabilitation Medicine, Seoul, Republic of Korea Disclosure: nothing to disclose T.R.H. Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea Disclosure: nothing to disclose Submitted for publication August 5, 2013; accepted November 14, 2013.
ª 2014 by the American Academy of Physical Medicine and Rehabilitation Vol. -, 1-6, --- 2014 http://dx.doi.org/10.1016/j.pmrj.2013.11.008
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Seo et al
of surface landmark identification in the larynx has been reported to be poor [8], and localization of the cricothyroid membrane is less precise in patients who are obese [9]. Ultrasonography is a noninvasive and safe imaging technique that can be used to investigate the anatomic structures of the head and neck [10]. It has been suggested that ultrasonography could be used to evaluate the structure and movement of the vocal folds [11,12], and might assist in the identification of the anatomic landmarks for cricothyroidotomy [8]. Therefore, it is possible that ultrasonography could be used as an assistive tool to overcome the technical difficulty of LEMG. The European Laryngological Society guidelines for LEMG suggest that palpating the anatomic landmarks can be difficult in patients who are obese or who have undergone neck surgery, and notes that the landmarks can be localized with ultrasonography [13]. However, to the best of our knowledge, the application of ultrasonography to LEMG has not been studied in detail. Our EMG laboratory has used ultrasonography to improve the accuracy of LEMG since 2010. In the present study, we describe the application of ultrasonography in LEMG and present the ultrasonographic measurements of important anatomic structures relevant to LEMG.
METHODS
ULTRASONOGRAPHY FOR LARYNGEAL ELECTROMYOGRAPHY
neck. The ultrasonographic measurements included the longest dimension of the CT membrane (CTmax), the height of the arch of the cricoid cartilage (HC), and the distance from the superior border of the cricoid cartilage to the midpoint of the vocal fold (C-VF) (Figure 1). Needle EMG evaluation of the recurrent laryngeal-innervated TA muscle is performed by inserting a monopolar needle electrode into the neck on the midline, just superior to the cricoid cartilage and angled 45 -60 superiorly and 20 laterally, to pierce the cricothyroid membrane. The depth of the needle insertion was determined by reference to C-VF measurement; a 37-mm needle electrode was usually used for men and a 25-mm needle electrode was used for women. The position of the needle was verified by asking the patient to phonate a high-pitched “E” sound and observing crisp-sounding motor units. To evaluate the CT muscle, which is innervated by the superior laryngeal nerve, the needle was inserted approximately 3-5 mm from the midline at the level of the superior border of the cricoid cartilage and angled 45 -60 superiorly and 30 -45 laterally. The position of the needle was verified by asking the patient to phonate “E” first at a low pitch and then at a higher pitch, and by observing the concomitant sharp increase in motor unit activity. The position of the needle tip was confirmed by ultrasonography in cases in which doubt remained (Figure 2).
Subjects We reviewed the medical records, LEMG records, and ultrasonographic measurements of the patients who underwent LEMG in our EMG laboratory between March 2010 and January 2013. A total of 595 LEMG studies were conducted in 527 patients. The 9 patients less than age 19 years were excluded, and a total of 585 LEMG studies in 518 patients (270 men and 248 women) were analyzed. This study was approved by the institutional review board of our hospital.
Technique In each patient, LEMG was recorded from the cricothyroid (CT) and thyroarytenoid (TA) muscles (Synergy on Nicolet EDX System, Natus Medical Inc, San Carlos, CA), as previously described [1,7], under ultrasound guidance. Ultrasonographic evaluations were performed with a 5- to 9-MHz linear transducer (Medison 128 BW prime, Samsung Medison Co, Ltd, Seoul, Korea). Each patient, while in the supine position, was examined with the neck hyperextended by using a surgical thyroid pillow. The anatomic landmarks, which were the superior border of the cricoid cartilage, the inferior border of the thyroid cartilage, the CT membrane, and the vocal folds, were defined by ultrasonography. The anatomic landmarks were easily defined at the midline of the neck except the vocal folds, which were visualized through the thyroid cartilage slightly lateral to the midline of the
Data Analysis The patients’ demographic characteristics, including age, gender, height, weight, etiology of disease, duration of symptoms, and laterality of vocal fold paralysis, were examined. The results of the ultrasonographic measurements were represented by means and standard deviations. The differences between the men and women were analyzed by using the Student t test. The Fisher exact test was used to compare the proportions of cases in which C-VF was not measured between the genders and among the age groups. Pearson correlation coefficients between the ultrasonographic measures and height were calculated. All statistical analyses were performed by using SPSS 16.0 (IBM Corp, Armonk, NY). P values of
Use of Ultrasonography to Locate Laryngeal Structures for Laryngeal Electromyography Han Gil Seo, MD, Hye Jin Jang, MD, Byung-Mo Oh, MD, PhD, Won Kim, MD, Tai Ryoon Han, MD, PhD Objective: To measure the representative anatomic landmarks for laryngeal electromyography (LEMG) and to delineate an accurate ultrasonography-guided approach. Design: A retrospective study. Setting: A university hospital. Participants: A total of 518 patients (270 men and 248 women) who underwent LEMG. Methods: The medical records, LEMG records, and ultrasonographic measurements of the patients who underwent LEMG in our electromyography laboratory between March 2010 and January 2013 were reviewed. Main Outcome Measurement: The longest dimension of the cricothyroid membrane, the height of the arch of the cricoid cartilage, and the distance from the superior border of the cricoid cartilage to the midpoint of the vocal fold were measured by using ultrasonography. Results: A total of 585 studies in 518 patients with a standard deviation (SD) mean age of 56.01 14.36 years (men, 59.28 14.09 years; women, 52.45 13.81 years) were reviewed. The most common etiology was surgery (44.6%), and the left side (56%) of the vocal folds was more frequently involved than the right side (23.4%) or both sides (9.4%). The longest dimension of the cricothyroid membrane, height of the arch of the cricoid cartilage, and distance from the superior border of the cricoid cartilage to the midpoint of the vocal fold measured 1.06 0.33 cm (men, 1.16 0.34 cm; women, 0.97 0.29 cm), 0.83 0.24 cm (men, 0.88 0.24 cm; women, 0.77 23 cm), and 1.88 0.48 cm (men, 2.09 0.51 cm; women, 1.70 0.36 cm), respectively. All measurements differed significantly between the men and women (P < .001 by Student t test). Conclusions: The current study provides reference ranges for ultrasonographic measurements of important anatomic landmarks for LEMG. This study also provides a technique for using ultrasonography in LEMG. Ultrasonography may be used as an adjuvant to overcome certain technical pitfalls of LEMG. PM R 2014;-:1-6
INTRODUCTION Laryngeal electromyography (LEMG) is used in laryngologic assessment as well as the diagnosis and treatment of voice disorders. Since its introduction in 1944, LEMG has been used to investigate the roles of the laryngeal muscles in voice production and laryngeal biomechanics. During the 1980s and 1990s, LEMG evolved into a valuable adjunct to laryngeal evaluation and became widely used in clinical practice [1,2]. Results of recent studies showed that LEMG is also useful in the diagnosis and treatment of vocal fold problems [3-5]. However, evidence-based reviews have reported that the positive evidence for LEMG was lacking and that additional prospective studies were still needed to assess its diagnostic accuracy and clinical utility [2,6]. Needle electromyography (EMG) of the muscles responsible for phonation is technically demanding. The challenges include the inability to directly visualize or to palpate the muscles of interest, the extreme thinness of the muscles, the need to identify anatomic landmarks by palpating the laryngeal structures, and patient discomfort [7]. The accuracy PM&R 1934-1482/13/$36.00 Printed in U.S.A.
H.G.S. Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea Disclosure: nothing to disclose H.J.J. Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea Disclosure: nothing to disclose B.-M.O. Department of Rehabilitation Medicine, Seoul National University, College of Medicine, Seoul National University Hospital, 101 Daehak-Ro, Jongno-Gu, Seoul 110-744, Republic of Korea. Address correspondence to: B.-M.O.; e-mail: [email protected] Disclosure: nothing to disclose W.K. Asan Medical Center, Department of Rehabilitation Medicine, Seoul, Republic of Korea Disclosure: nothing to disclose T.R.H. Department of Rehabilitation Medicine, Seoul National University College of Medicine, Seoul National University Hospital, Seoul, Republic of Korea Disclosure: nothing to disclose Submitted for publication August 5, 2013; accepted November 14, 2013.
ª 2014 by the American Academy of Physical Medicine and Rehabilitation Vol. -, 1-6, --- 2014 http://dx.doi.org/10.1016/j.pmrj.2013.11.008
1
2
Seo et al
of surface landmark identification in the larynx has been reported to be poor [8], and localization of the cricothyroid membrane is less precise in patients who are obese [9]. Ultrasonography is a noninvasive and safe imaging technique that can be used to investigate the anatomic structures of the head and neck [10]. It has been suggested that ultrasonography could be used to evaluate the structure and movement of the vocal folds [11,12], and might assist in the identification of the anatomic landmarks for cricothyroidotomy [8]. Therefore, it is possible that ultrasonography could be used as an assistive tool to overcome the technical difficulty of LEMG. The European Laryngological Society guidelines for LEMG suggest that palpating the anatomic landmarks can be difficult in patients who are obese or who have undergone neck surgery, and notes that the landmarks can be localized with ultrasonography [13]. However, to the best of our knowledge, the application of ultrasonography to LEMG has not been studied in detail. Our EMG laboratory has used ultrasonography to improve the accuracy of LEMG since 2010. In the present study, we describe the application of ultrasonography in LEMG and present the ultrasonographic measurements of important anatomic structures relevant to LEMG.
METHODS
ULTRASONOGRAPHY FOR LARYNGEAL ELECTROMYOGRAPHY
neck. The ultrasonographic measurements included the longest dimension of the CT membrane (CTmax), the height of the arch of the cricoid cartilage (HC), and the distance from the superior border of the cricoid cartilage to the midpoint of the vocal fold (C-VF) (Figure 1). Needle EMG evaluation of the recurrent laryngeal-innervated TA muscle is performed by inserting a monopolar needle electrode into the neck on the midline, just superior to the cricoid cartilage and angled 45 -60 superiorly and 20 laterally, to pierce the cricothyroid membrane. The depth of the needle insertion was determined by reference to C-VF measurement; a 37-mm needle electrode was usually used for men and a 25-mm needle electrode was used for women. The position of the needle was verified by asking the patient to phonate a high-pitched “E” sound and observing crisp-sounding motor units. To evaluate the CT muscle, which is innervated by the superior laryngeal nerve, the needle was inserted approximately 3-5 mm from the midline at the level of the superior border of the cricoid cartilage and angled 45 -60 superiorly and 30 -45 laterally. The position of the needle was verified by asking the patient to phonate “E” first at a low pitch and then at a higher pitch, and by observing the concomitant sharp increase in motor unit activity. The position of the needle tip was confirmed by ultrasonography in cases in which doubt remained (Figure 2).
Subjects We reviewed the medical records, LEMG records, and ultrasonographic measurements of the patients who underwent LEMG in our EMG laboratory between March 2010 and January 2013. A total of 595 LEMG studies were conducted in 527 patients. The 9 patients less than age 19 years were excluded, and a total of 585 LEMG studies in 518 patients (270 men and 248 women) were analyzed. This study was approved by the institutional review board of our hospital.
Technique In each patient, LEMG was recorded from the cricothyroid (CT) and thyroarytenoid (TA) muscles (Synergy on Nicolet EDX System, Natus Medical Inc, San Carlos, CA), as previously described [1,7], under ultrasound guidance. Ultrasonographic evaluations were performed with a 5- to 9-MHz linear transducer (Medison 128 BW prime, Samsung Medison Co, Ltd, Seoul, Korea). Each patient, while in the supine position, was examined with the neck hyperextended by using a surgical thyroid pillow. The anatomic landmarks, which were the superior border of the cricoid cartilage, the inferior border of the thyroid cartilage, the CT membrane, and the vocal folds, were defined by ultrasonography. The anatomic landmarks were easily defined at the midline of the neck except the vocal folds, which were visualized through the thyroid cartilage slightly lateral to the midline of the
Data Analysis The patients’ demographic characteristics, including age, gender, height, weight, etiology of disease, duration of symptoms, and laterality of vocal fold paralysis, were examined. The results of the ultrasonographic measurements were represented by means and standard deviations. The differences between the men and women were analyzed by using the Student t test. The Fisher exact test was used to compare the proportions of cases in which C-VF was not measured between the genders and among the age groups. Pearson correlation coefficients between the ultrasonographic measures and height were calculated. All statistical analyses were performed by using SPSS 16.0 (IBM Corp, Armonk, NY). P values of
