A Narrative Review on Laryngeal Manual Therapy Methods in Muscle Tension Dysphonia: Manual Techniques, Target Structures, and Tension Criteria

Abstract

Background

Laryngeal manual therapy (LMT) has been known as one of the main techniques for decreasing musculoskeletal tension in the (para) laryngeal muscles in dysphonic patients, especially patients with muscle tension dysphonia (MTD).

Objective

A narrative review on the available LMT methods in MTD.

Study Design

(Method).

A review on the literature regarding to the LMT methods in MTD was conducted using electronic databases up to December 2022. To identify all eligible literature, hand searching was also utilized. Moreover, articles and books in which LMT methods were introduced or used for the first time, or had innovation and were complementary for previous LMT methods were included. Relevant sources were identified by two reviewers based on screened titles/abstracts and full texts.

Results

The authors found five main common and some miscellaneous LMT methods that may not be used as conventional methods in clinical and research settings. There are some similarities and differences between the available LMT methods based on the manual techniques, target anatomical structures, and tension criteria. Although there is not enough information about details of some LMT methods, we additionally tried to provide some details about LMT treatment protocol.

Conclusion

The LMT is still at the beginning and it is necessary to revise the previous methods or develop new ones according to the similarities and differences have been found in this review. This paper will be useful for learning and teaching the LMT methods in MTD for clinicians and students who are interested in.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12070-024-04896-1.

Introduction

Muscle tension dysphonia (MTD) is a frequently used term in voice clinics. It was originally introduced by Morrison and colleagues [1]. MTD is a condition where the muscles around the voice box and nearby areas are overly tense [1–3]. There are two types of MTD: primary and secondary. Primary MTD does not have clear reasons for its occurrence, while secondary MTD is a reaction to existing organic conditions[4]. MTD is a condition where vocal folds behave abnormally due to various factors. It is considered a link between organic and functional voice disorders [3]. The main factors causing MTD are increased tension, hyperfunction, and unbalanced/uncoordinated activity in the muscles around the larynx [2, 3, 5]. Voice pathologists need to understand the normal functioning of the larynx and surrounding muscles, as well as the changes in tense muscles, to accurately diagnose and effectively treat MTD patients [5–7].

When evaluating MTD, it is important to consider various factors, such as patient complaints, auditory-perceptual assessment, and laryngostroboscopy. Other evaluations, such as acoustic measurements, aerodynamic assessments, and surveys of quality of life, should also be taken into account [3, 8, 9]. Voice therapists can use different subjective and objective measures to diagnose MTD, select appropriate treatments, and track changes in voice [3, 8]. Palpation is a subjective method that can be used to assess tension in the larynx and surrounding areas[10]. To achieve this goal, different laryngeal palpation scales such as Angsuwarangsee and Morrison grading scale, Mathieson et al. grading scale, and novel laryngeal palpatory scale (LPS) have been developed [9, 11, 12]. Familiarity with palpation and accurate performance is essential for voice therapists evaluating and treating MTD.

Laryngeal manual therapy (LMT) is a key technique used in voice therapy to reduce tension in the laryngeal and paralaryngeal muscles for patients with MTD [13, 14]. The LMT targets different anatomical structures within and around the voice box to improve the ability to produce voice. Intrinsic laryngeal muscles are responsible for phonation, while extrinsic laryngeal muscles support their movement and activity [11, 15, 16]. Patients with MTD experience excessive tension, hyperactivity, and dysregulation in both intrinsic and extrinsic laryngeal muscles [2, 17, 18]. The LMT methods have been developed to reduce muscle tension in the extrinsic laryngeal muscles and regulate their activity [5, 14]. It is believed that by reducing tension in the extrinsic laryngeal muscles, the function of the intrinsic laryngeal muscles improves and eventually relieves the symptoms of dysphonia. Since the first LMT technique was introduced, several different methods have been suggested for MTD patients.

In 1990, Aronson introduced the first LMT technique for vocal hyperfunction [17]. Over time, more studies have been conducted, and new methods have been developed in the field of speech-language pathology (SLP). Roy et al. conducted studies to evaluate the effectiveness of the Aronson technique and made improvements, resulting in the introduction of manual circumlaryngeal therapy (MCT) [3, 11, 13, 15–18]. In 1998, Lieberman introduced a new LMT method based on the osteopathic approach [6]. Then, in 2009, Mathieson and colleagues developed a different LMT specifically for MTD patients. Additionally, there are a few other LMT-related studies based on SLP and physiotherapy viewpoints, although they are mentioned less often in the literature [19–22]. These different LMT methods have similarities and differences that are worth understanding for those interested in the field of LMT. Despite various LMT methods being individually introduced or mentioned in previous articles, there has not been a study that comprehensively summarizes all these methods. This study aims to introduce and compare all LMT methods in MTD in terms of techniques used, target anatomical structures, and criteria for reducing tension. Additionally, specific treatment details such as patient/therapist positions, tasks, number, and duration of sessions will be discussed in detail.

Method

We looked at electronic databases including medline (pubmed), web of science, google scholar, and CINAHL for information on the LMT methods in MTD from 1990 to december 2022. We used keywords such as ‘‘laryngeal manual therapy”, ‘‘laryngeal massage”, ‘‘laryngeal manipulation”, ‘‘muscle tension dysphonia’’, “muscle misuse voice disorder”, “vocal hyperfunction”, “functional voice disorder”, and “functional dysphonia” to find relevant articles. We also manually checked the references of those articles for additional citations. Related books were among other sources that were reviewed. We included articles and books that introduced or used the LMT methods for the first time or provided innovation or complement to existing LMT methods. In addition, only english language articles were included in this study. We excluded articles that used the LMT for therapeutic purposes or to evaluate treatment effectiveness. Finally, we excluded articles that did not address the topic of interest based on our search strategy and keywords. Relevant sources were identified by two reviewers based on screened titles/abstracts and full texts (Fig. 1).

Fig. 1.

Flow diagram of narrative review of literature

Results

We discovered five main methods of LMT [9, 13, 23–26], as well as some additional methods [19–22]. The main focus of these LMT methods was using massage on the extralaryngeal muscles and sometimes on muscles near the larynx. In most of these methods, if tension is confirmed through palpation, manual therapy is used on the patients. The main goal in the majority of LMT methods is to reduce muscle tension, improve fluid drainage, enhance neural messaging, eliminate waste from the body, improve blood circulation, improve laryngeal posture, and in turn, improve dysphonia [5, 9, 20, 23].

There are different LMT methods for reducing musculoskeletal tension. They all have similarities and differences in how they are done and what they target. Additionally, criteria for the assessment of tension and document tension reduction may be different among the LMT methods. Some methods have more information available about their details, but we also tried to provide extra information about things such as the position of the patient and therapist during treatment, the tasks done during treatment, how many sessions are needed, and how long each session lasts. In the following, we describe the main and miscellaneous LMT methods separately. In addition, the specifications of the available LMTs based on the type of literature are given in Tables 1 and 2.

Table 1.

Characteristics of laryngeal manual therapy (LMT) methods introduced in textbooks and tutorial articles

Author/s (year)	LMT Methods	Manual techniques	Target Structures	Tension Criteria	LMT Protocol
Aronson & Bless (2009) [23]	Manual laryngeal musculoskeletal tension reduction technique	1) Circular massage; 2) Downward and lateral movement	1) Hyoid bone; 2) Thyrohyoid (TH) space; 3) Thyroid cartilage	1) Narrow space (laryngeal elevation); 2) Laryngeal pain in response to pressure or as patient complaint; 3) Feeling lump or ball in the larynx or pharynx as patient complaint; 4) Resistance of the larynx and Hyoid bone to lateral and vertical movement; 5) Voice improvement after treatment	Patient position: Sitting; Therapist position: Not reported; Vocal tasks: Sustain vowels or hum, shaping voice from vowels to words, phrases, sentences; Manual intervention: Unimanual, thumb and middle fingers; Number of sessions: Different from one to several sessions according to patient's need; Duration of sessions: Not exactly reported (within 15 min plus palpation based on the case reports); Follow up: Not reported
Roy et al. (1998 & 2008) [5, 24]	Manual circumlaryngeal therapy (MCT)	1) Circular pressure; 2) Manual laryngeal reposturing maneuvers (Hyoid pushback, pull-down & combined medial compression and downward traction)	1) Hyoid bone (body and tips); 2) Thyroid cartilage (posterior and superior borders, and superior cornu); 3) TH space; 4) Anterior border of the sternocleidomastoids (SCMs); 5) Suprahyoid area (if necessary)	1) Laryngeal elevation (Decreased TH space); 2) Pain in response to pressure (In the area of the hyoid bone and TH space); 3) Excessive tension (Focal nodularity, taut bands & stiffness) in the suprahyoid region; 4) Tension and narrowing of the cricothyroid (CT); 5) Patients report from ache & tightness in the anterior neck, larynx, and shoulders; 6) Laryngoscopic features of dysregulated laryngeal muscle activity; 7) Abnormal voice quality	Patient position: Sitting; Therapist position: Not reported; Vocal tasks: Sustain vowels or to hum, shaping voice from vowels to words, phrases, sentences Manual intervention: Unimanual, using thumb and middle fingers; Number of sessions: Different from one session to several sessions; Duration of sessions: Flexible according to patient's need; Follow up: Not reported
Lieberman (1998)[6] Rubin et al. (2000) [7]	Osteopathic LMT	1) Passive articulation, stretching, kneading, inhibition, rhythmic traction and springing, stripping, and massage techniques; 2) Semiactive or active breathing control; 3) Muscle energy, low velocity stress, relaxation techniques, and high velocity thrust	1) Hyoid bone; 2) Thyroid cartilage; 3) Superior suspensory muscles; 4) TH space; 5) Inferior suspensory muscles; 6) Cricoid cartilage; 7) CT joints; 8) CT muscles; 9) Pharyngeal constrictors; 10) Posterior cricoarytenoid muscles; 11) Cricoarytenoid joints; 12) Lateral cricoarytenoids 13) Interarytenoids; 14) Musculature related to temporomandibular joint (TMJ); 15) SCMs; 16) Palatal muscles	1) Hyper tonicity, decreased range of motion & fibrotic changes in external laryngeal muscles; 2) Asymmetry in laryngeal muscles function; 3) Pulled forward or tilted hyoid bone; 4) Decreased or painful TH space; 5) Short or painful space between hyoid and symphysis; 6) Low anchored larynx; 7) Chronic dry cough & irritation, nonspecific soreness, and dryness in throat 8) Tenderness or difference in muscle bulk between the sides of CT visor; 9) Failure in anterior lifting and lateral rotation of pharyngeal constrictors muscle; 10) Loss of vocal range & stamina; 11) Swallowing difficulties or globus feelings; 12) Tightness at the tongue base; 13) Tenderness in temporomandibular joints (TMJs) & palatal muscles; 14) Tightness in the SCMs; 15) Tenderness in palatal muscles	Patient position: Supine; Therapist position: Standing at the side of the patient's; Vocal tasks: Not reported; Manual intervention: Bimanual and unimanual using pads of index, middle, and third fingers; Number of sessions: Different from one session to several sessions; Duration of sessions: Not reported; Follow up: Not reported

LMT, Laryngeal manual therapy; TH , Thyrohyoid; MCT ,  Manual circumlaryngeal therapy; SCM ,  Sternocleidomastoid; CT,  Cricothyroid; TMJs ,  Temporomandibular joints

Table 2.

Characteristics of Laryngeal Manual Therapy (LMT) Methods introduced in original articles

Author/s (year)	Study Design	Participants	LMT Method	Manual techniques	Target Structures	Tension Criteria	LMT Protocol
Roy et al. (1993, 1996, and 1997) [27, 29, 30]	Pre and posttest (1993); Case report (1996); Repeated measures preand posttreatment (1997)	Functional dysphonia (n: 17; 16 F) (1993); Muscle tension dysphonia (MTD) (n: 1), Spasmodic dysphonia (n: 1), Spasmodic dysphonia + MTD (n: 1) (1996); Functional dysphonia (n: 25; F) (1997)	Aronson's technique (1993); Manual circumlaryngeal therapy (MCT) (1996 & 1997) Laryngeal reposturing maneuvers (1996)	1) Manual tension reduction procedure (1993, 1996 & 1997); 2) MCT (1993, 1996 & 1997); 3) Laryngeal reposturing maneuvers: Downward and lateral moving the larynx, downward traction (Pull-down maneuver) (1993, 1996 & 1997)	1) Hyoid bone (body & tips) (1993, 1996 & 1997); 2) Thyroid cartilage (Notch, upper & posterior borders) (1993, 1996 & 1997); superior corn (1996); 3) Thyrohyoid (TH) space (1993, 1996 & 1997); 4) Anterior border of the sternocleidomastoids (SCMs) (1996); 5) Suprahyoid muscles (1996)	1) Narrowed or absent space/Laryngeal elevation) (1993, 1996 & 1997); 2) Closed space (1993, 1996 & 1997); 3) Pain (1993, 1996 & 1997); 4) Voice improvement following downward maneuver (1996); 5) Excessive tension in suprahyoid region (1996); 6) Tightness and pain, tenderness and taut bands, and focal tenderness or nodularity in the laryngeal region (1996); 7) Larynx resistance to lateral movement (1996)	Patient position: Sitting; Therapist position: Not reported (1993, 1996 & 1997); Vocal tasks: Sustain vowels or hum, shaping voice from vowels to words, phrases, sentences, paragraph recitations and to conversation; Manual intervention: Unimanual, using thumb and middle fingers (1993, 1996 & 1997); Number of sessions: One session (1993, 1996); One session (1993, 1997); Duration of sessions: Different from 1 to 3 h (1993), Not reported (1996), different from 50 min to 3 h (1997); Follow up: One week later with telephone (1993), not reported (1996), three faces to face follow ups (1997)
Mathieson et al (2009) [9]	Repeated measures pilot study (Pre and post design)	Primary MTD (n: 10; 8 F)	Mathieson’s LMT (MLMT)	1) Circular massage; 2) Kneading; 3) Circular massage; 4) Side to side movement of the larynx	1) SCMs; 2) Supralaryngeal area; 3) Hyoid bone; 4) Larynx	1) Muscle resistance; 2) Resistance to lateral digital pressure; 3) Laryngeal height	Patient position: Siting; Therapist position: Standing behind patient; Vocal tasks: Counting, days of the week, gliding, and spontaneous speech in the final stage of intervention; Manual intervention: Bimanual and unimanual with pad of index, middle, and third fingers; Number of sessions: Not reported; Duration of session: 10 min; Follow up: Not reported
Voice Massage [25, 26]	Quasiexperimental study [25, 26]	Healthy subjects [25, 26]	Voice massage [25, 26]	1) Strokes; 2) Kneading; 3) Friction; 4) Intercostal pull of agonistic and antagonistic muscles; 5) Education for ease of breathing and phonation; 5) Active relaxation	1) Laryngeal muscles; 2) Respiratory muscles; 3) Articulatory muscles	1) Mobility of the ribcage during breathing; 2) Excessive tension in the various muscles involved in the voice production	Patient position: Supine; Therapist position: Standing beside patient; Vocal tasks: Breathing against resistance offered by the therapist’s hands, production of long voiceless/s/, humming on nasals and phonation on voiced fricatives; Manual intervention: Bimanual and unimanual; Number of sessions: 5 sessions [26]; Duration of session: One hour; Follow up: None [25], six months and 12 months [26]
Salehi & Barkmeier-Kraemer (2014) [22]	Case report (Pre and post design)	Singers with vibrato problems (n: 4; 3 M)	Mixing LMT with vocalization during Iranian Tahrir vibrato & a modified version of MCT	1) Posture correction of head and neck; 2) Bimanual circular kneading; 3) Light circular massage; 4) Bimanual light pressure; 5) Support and prevent the larynx from deviating during Tahrir by placing the fingertips on the lateral sides of the cricothyrohyoid structure; 6) Circular massage of the superior border of the hyoid during vibrato in the chin tuck, or neck flexion head position	1) Head and neck; 2) Cricothyroid (CT); 3) SCMs (Anterior surface); 4) Hyoid bone (body & superior border)	1) Position and the degree of laryngohyoid deviation from the midline; 2) Palpable tension, stiffness, and protrusion of the anterior neck muscle groups	Patient position: Siting; Therapist position: Standing behind patient; Vocal tasks: Tahrir vibrato production Manual intervention: Bimanual and unimanual with index, middle and third finger; Number of sessions: 20 sessions (3 weekly sessions); Duration of session: 15 min; Follow up: None
Craig et al (2015) [20]	Retrospective Cohort Study	MTD patients (n: 153; 104 M)	Physical therapy	Perilaryngeal massage, neck stretches, ergonomic training, posture correction, neck and chest extensions, shoulder rotations, trunk rotation, pectoralis stretch, self-relaxation, tongue stretch, temporomandibbular joints (TMJs) stretch, scar management, lower limb stretch	1) SCMs; 2) Scalene muscles; 3) Suprahyoid muscles; 4) Infrahyoid muscles; 5) Chest muscles; 6) Posterior cervical muscles; 7) TMJs; 8) Masseter muscles; 9) Psoas muscles; 10) Thyroid cartilage; 11) Hyoid bone	Tenderness or tension in the TH space, anterior neck, shoulders, and upper back	Patient position: Siting & Supine; Therapist position: Not reported; Vocal tasks: Not reported; Manual intervention: Bimanual and unimanual; Number of sessions: At least 8 sessions over 90 days; Duration of session: Not reported; Follow up: None
Dehqan & Ballard (2019) [21]	A quasiexperimental study (Pre and posttest)	Primary MTD (n: 88; F)	MCT & Cricothyroid visor maneuver (CVM)	MCT: 1) Circular massage; 2) Downward and lateral movement) CVM: Pulling away of the visor	MCT: 1) Hyoid bone; 2) Thyrohyoid (TH) space; 3) Thyroid cartilage; CVM: CT space (visor)	Not reported	Patient position: Sitting for MCT & Not reported for CVM (Supine according to Fig. 1 [21]; Vocal tasks: Not reported; Manual intervention: MCT: Unimanual, thumb and middle fingers; CVM: Bimanual (Thumbs of both hands); Therapist position: Not reported; Number of sessions: One session; Duration of sessions: Thirty minutes; Follow up: None

LMT , Laryngeal manual therapy; n,  Number; F , Female; MTD ,  Muscle tension dysphonia; MCT ,  Manual circumlaryngeal therapy; TH , Thyrohyoid; SCMs ,  Sternocleidomastoids; MLMT ,  Mathieson’s laryngeal manual therapy; M , Male; CT , Cricothyroid; TMJs ,  Temporomandibular joints; CVM , Cricothyroid visor maneuver

The LMT Method of Aronson

Aronson was the first author to write about tension-related voice disorders at LMT. His technique, known as the “manual laryngeal musculoskeletal tension reduction technique” or “manual circumlaryngeal manipulation”, focuses on reducing tension in the voice box muscles. In his book, Clinical Voice Disorders, Aronson suggested using digital techniques to relax the paralaryngeal muscles for vocal hyperfunction [17].

The Aronson method uses a circular massage technique with pressure applied downward or sideways. The therapist uses their thumb and middle fingers of one hand to apply this technique to certain areas of the larynx, such as the hyoid bone, thyrohyoid (TH) space, posterior, and superior borders of the thyroid cartilage. The patient is asked to speak and make sounds during the treatment to see if their voice improves. Signs of tension are identified through self-reporting by the patient, and feelings of tension are identified through palpation by the clinician. The patient may experience pain in their larynx, which might spread to their ears and chest, and they may feel a lump or tension in their throat. When the therapist feels tension in the muscles, they may notice that the larynx is elevated and the patient might experience pain in response to pressure. The patient’s voice may improve once the tension is reduced. During treatment, the therapist stands beside the patient while he/she is sitting. According to Aronson, a normal voice can be achieved within a few minutes or several hours across multiple sessions. Since this is the first LMT technique, there are currently no specific details about the treatment protocol [17]. The developers found some clinical findings. These included 1) the larynx being lower due to increased TH space; 2) improved voice quality and lower pitch; and 3) soreness in the larynx that went away within 1–2 days. However, there was no proof of Aronson’s LMT method’s effectiveness until 1993. Furthermore, not much is known about the long-term effects of treatment or if the problem will come back.

The LMT Method of Roy et al.

After Aronson introduced the “manual laryngeal musculoskeletal tension reduction technique” in the 1990s, Roy and his team reviewed how well it worked in different studies from 1993 to 2009 [5, 24, 27–31]. Then, Roy and his colleagues developed and introduced a modified version of Aronson’s method called MCT [27].

The MCT involves circular massage, gentle kneading or sustained pressure, pulling down, and lateral movement. It focuses on specific structures of the larynx, such as the hyoid bone, greater horns of the hyoid, TH space from the thyroid notch to its posterior region, upper border of the thyroid cartilage, posterior borders of the thyroid cartilage near the sternocleidomastoid (SCM) muscles, and, if needed, the medial and lateral suprahyoid muscles. In this method, focal areas of pain, discomfort, soreness, tenderness, muscle nodularity, laryngeal elevation, limitation of laryngeal side-to-side mobility, and voice effect following downward pulling of the thyroid are considered tension criteria. These tension criteria can be evaluated during rest and while speaking. Additionally, Roy introduced three manual laryngeal repositioning techniques: “hyoid pushback”, “pull down the larynx”, and “combined medial compression and downward traction”. Three laryngeal reposturing maneuvers involve applying inward and downward pressure, downward traction, and combined medial compression and downward traction as manual techniques. The “hyoid pushback” targets the suprahyoid area at the base of the tongue, the hyoid bone, and the TH space. The superior margin of the thyroid cartilage and the superior cornu of the thyroid are targeted in the other two maneuvers. These maneuvers are used to assess the potential for temporary voice improvement and to address habitual muscle misuse patterns [5, 24].

In the MCT method, the patient sits while the therapist sits beside him/her. MCT sessions can last anywhere from 50 min to 3 h, as reported in various studies [21, 27, 29, 30, 32, 33]. It is important to note that the number and length of treatment sessions may be extended based on the patient’s tolerance and progress [5]. While the exact number of sessions needed is not known, Roy suggests that improvement can be seen even after the first session. Research at MTD has shown that MCT is effective after just one session [21, 27, 29, 30, 34, 35], as well as after multiple sessions [32, 33].

According to the literature, the MCT has been found to have several effects, including 1) Improving voice quality by reducing jitter and shimmer and enhancing the signal-to-noise ratio [27, 30]; 2) Decreasing laryngeal height [30]; 3) Reducing pain [30]; and 4) Identifying abnormal muscle tension through a positive response to circumlaryngeal massage [29]. However, it should be noted that some patients experienced early recurrences during follow-up [27]. Additionally, the MCT has been reported to be useful for diagnosing and making clinical decisions for both MTD and spasmodic dysphonia [29].

The LMT from the Viewpoint of Osteopathy

The LMT, as viewed by Lieberman (1998) [6] and Rubin et al. (2000) [7], is based on the principles of osteopathy, a form of complementary medicine. Osteopathy is a comprehensive healthcare system with various descriptions [36–38]. According to William and Michael Kuchera (1992), it is a system that promotes and teaches the osteopathic philosophy: 1) The body functions as a whole; 2) It has its own mechanisms to protect and regulate itself; and 3) The structure and function of the body are interconnected [39]. In this approach, treatment takes into account these three principles. Osteopathy includes various diagnostic and healing techniques, such as osteopathic palpation and manipulative treatments [13].

In osteopathic LMT, manual treatment techniques are only used after assessing and diagnosing the patient’s condition. This approach involves taking a detailed history and observing and feeling the patient’s posture, head position, laryngeal posture, and breathing. Based on this information, a comprehensive treatment plan is created, taking into account the patient’s history, assessment, tolerance, and ability. The plan includes specific techniques to improve posture and exercises to establish new muscle patterns. The goal of treatment is to improve joint mobility, restore muscle function symmetry, and correct abnormal postures [13]. This paper focuses on introducing laryngeal posture correction techniques using the osteopathic approach. The techniques involve soft tissue manipulation, such as stretching and kneading, on specific muscles. The muscles are stabilized against fixed structures, and gentle pressure is applied to separate or move adjacent structures in different directions. These techniques are performed in passive and active situations, either on one side or both sides, depending on the assessment results. The target structures in the larynx include the hyoid bone, thyroid cartilage, superior suspensory muscles, TH space, inferior suspensory muscles, cricoid cartilage, cricothyroid (CT) joint, CT muscles, pharyngeal constrictors, posterior cricoarytenoid muscles, cricoarytenoid joints, lateral cricoarytenoids, and interarytenoids. There are also other targets to manipulate, such as the SCM muscles, temporomandibular joint (TMJ)-related muscles, and palatal muscles. An osteopathic LMT uses observation and palpation to determine tension. The practitioner examines the patient’s posture, head position, breathing habits, and laryngeal movements. They also consider factors such as the range and direction of laryngeal movements, asymmetry, and deviation of the suspensory muscles during swallowing and speech. The position of the larynx, tissue quality (bulk differences and deformity or fibrotic changes), muscle hypertonicity, decreased joint motion range, pain and tenderness in muscles, joints, and ligaments, anchored larynx, and laryngeal cartilage displacement are also taken into account as tension criteria during palpation. These tension criteria are evaluated during various activities, such as swallowing, low and high vocal tasks, laryngeal rotation, lateral laryngeal movement, stretching, and laryngeal lifting [13].

During osteopathic LMT, the patient lies on their back while the practitioner stands beside him/her. The practitioner uses their fingers to perform the intervention, either with one hand or both hands. It is recommended that a skilled practitioner palpates the internal laryngeal structures because it requires special skills [13]. Some immediate effects of osteopathic LMT include increased pitch changes, decreased hoarseness, improved swallowing and sense of openness, and reduced wobble, pain, and discomfort. Long-term effects may include increased vocal range, stamina, and flexibility, better ability to navigate vocal transitions, resolved laryngeal click, improved joint mobility, improved muscle function symmetry, and improved awareness of abnormal posture. There is limited information available about the specifics of osteopathic LMT, with only one study mentioning the number and duration of sessions. In that study, osteopathic LMT was performed for one hour per session over a one-week intensive treatment period [40].

The LMT Method of Mathieson et al.

In 2009, Mathieson and colleagues introduced a new method called Mathieson’s LMT (MLMT) for treating tension in the muscles around the larynx. The MLMT involves circular massage, kneading, and stretching. Vocalization is not recommended during massages to prevent the return of habitual hyperfunctional patterns. At the end of the process, the patient is asked to make vocalizations to check for relaxation. The MLMT focuses on specific areas around the larynx and considers muscle resistance, laryngeal resistance, and abnormal laryngeal position as indicators of tension. The authors stated that the MLMT takes approximately 10 min and can be repeated within a session based on the patient's needs [9]. Research on the effectiveness of this method has found that it can improve certain aspects of the voice after just one session [9] or multiple sessions [41–43]. Some of the key positive changes include a decrease in resistance of the SCMs and supralaryngeal area and improved movement of the larynx. However, there was no significant change in the frequency of formants or reduction in certain discomfort sensations in the vocal tract [9]. The outcomes of the multiple treatment sessions varied. The MLMT helped to rebalance the larynx muscles during phonation by providing better regularity during laryngeal diadochokinesis and improving supraglottic activity. It also improved how the voice sounds and how individuals perceive their own vocal abilities. Additionally, the type of MTD changed after multiple treatment sessions [41–43].

Voice Massage

Voice massage (VM) is a massage technique from Finland that focuses on the muscles involved in phonation. Its main purpose is to improve the movement of the ribcage during breathing and reduce tension in the muscles used for production of the voice. VM involves manual techniques such as strokes, kneading, and friction, as well as intercostal pulling of agonistic and antagonistic muscles. It also aims to increase patients’ awareness of their muscle state, breathing, and phonation processes, and active relaxation. The targeted muscles include those in the larynx, respiratory system, and articulation. The VM is performed with the patient lying down and the clinician standing. Manual intervention is performed using one or both hands during breathing exercises and sustained voiceless and voiced consonant sounds [25, 26]. The recommended frequency for VM sessions is once a week for the first three sessions, followed by once a month for the last two sessions, totaling five sessions (each session lasts one hour) [25, 26]. It is important to note that the effectiveness of VM for dysphonic patients has not been studied.

Other LMT Methods

Additionally, there are four manual therapies for the larynx mentioned in the literature that are not commonly used for patients with MTD or voice disorders in clinical and research settings [19–22]. These methods are categorized as “other” LMT methods.

Boone et al. proposed three techniques called digital manipulation. These techniques involve gently pushing from the back, monitoring the up-and-down movement of the larynx, and applying pressure. The specific targets are the front area of the thyroid cartilage, the thyroid cartilage itself, and the sidewall of the thyroid cartilage. The first and second techniques aim to lower pitch and reduce excessive larynx movement during phonation. However, the third technique does not have specific criteria for reducing laryngeal muscle tension because its main purpose is to address paralysis of the vocal folds [19]. The first and second techniques are recommended for patients with puberphonia and pitch variability, respectively, while the third technique is used for patients with vocal fold paralysis. Unfortunately, there is limited information available about the details of treatment using Boone et al.’s digital manipulation techniques.

In 2014, Salehi and Barkmeier-Kraemer conducted a case-based study on treating Tahrir problems in singers using modifications and additions to the LMT. The study focused on correcting the posture of the head and neck, performing circular kneading, and preventing larynx deviation during Tahrir as manual techniques. The targeted anatomical structures included the head and neck, lateral sides of the CT muscles, lateral sides of the larynx, anterior border of the SCMs, and superior border of the hyoid. Measures of tension in this method included deviation of the CT structure from the midline, as well as tension, stiffness, and protrusion of the anterior neck muscle groups. During the intervention, the patient sat while the manual therapist stood behind them, using their index, middle, and third fingers with one hand or both hands. Salehi and Barkmeier-Kraemer evaluated the effectiveness of this method after 20 sessions, with three weekly sessions lasting 15 min each [22]. They reported positive outcomes such as increased satisfaction, improved vibrato regularity and rate, enhanced relaxation, better alignment in laryngeal palpation, and improved acoustic measures during vibrato [22].

Craig et al. (2015) suggested combining physical therapy with voice therapy for treating MTD. The manual techniques used in this study included joint mobilization, passive range of motion exercises, contract-relax stretching, and myofascial release. Voice therapy in the form of MCT was also utilized. The targeted anatomical structures included the TMJ, masseter muscles, supra- and infrahyoid muscles, hyoid bone, thyroid cartilage, SCMs, scalenes, chest muscles, posterior cervical muscles, and psoas muscles. Tension was identified through tenderness or tension felt during digital palpation. Patients could be in either sitting or standing positions during the intervention, but specific treatment protocols were not provided. The number of physical therapy sessions varied based on individual patient needs, with an average of 8 sessions. The duration of each treatment session was not reported [20]. Interestingly, there were no significant differences in the VHI score among the different treatment groups.

Dehqan and Ballard (2019) introduced a technique called the cricothyroid visor maneuver (CVM) and combined it with traditional MCT to compare their immediate effects. In CVM, the visor is pulled away from both sides to open the CT space while producing a high-pitched sustained vowel sound (/a/). The authors reported that posttherapy voice improvement was observed due to reduced tension following CVM, but they did not specify the criteria for measuring tension in CVM. This technique was presented in a 30-min session. Although the authors suggested studying the long-term effects of CVM, they did not provide any recommendations regarding the number or duration of treatment sessions for this method [21]. The authors claimed that both MCT and CVM resulted in positive changes in voice quality based on acoustic-perceptual measures and self-report, but the CVM group. showed greater improvements compared to the group that received only MCT [21]

Discussion

Manual therapy is a useful and practical treatment option for people with voice disorders, definitely for those with MTD. It is a safe method that can be regularly used by healthcare professionals, as it does not require any special equipment. However, using manual therapy effectively requires expertise in muscle work, laryngeal mechanisms, and voice characteristics.

We examined the different LMT methods that are available. We discovered that these methods have similarities and differences in terms of how they are performed manually, the structures they target in the body, and the criteria for applying tension. Additionally, we found some information about how these methods are used in treatment. In the next section, we will discuss the LMT methods based on what we have learned.

Manual Techniques

All LMT methods aim to reduce tension, but the specific techniques used vary because experts and researchers have different criteria for defining tension. This means that the definition of tension in the larynx affects which manual techniques are chosen in LMT methods. For instance, many researchers consider an elevated larynx to be a common indicator of tension in the larynx [5, 9, 23]. As a result, lowering the larynx is one of the manual techniques that was proposed in some LMT methods, such as the Aronson technique, the Roy maneuvers [5, 23], and the MLMT [18]. In contrast, some LMT methods suggest that narrowing or closing the laryngeal spaces can show tension [5, 6, 23, 24]. Therefore, opening the laryngeal spaces is recommended by these methods [13, 21].

The type of massage is an important factor in LMT Methods. According to SLPs, the most important massage technique is kneading and circular massage [5, 9, 23, 24]. Although “kneading” can have different meanings, such as lifting, compression, crushing, and rhythmic release of soft body tissues [44, 45], SLPs seem to use it as a circular massage with finger pressure and rotation [5, 22, 24]. Additionally, Roy considers kneading and sustained pressure to be the same, but in the manual therapy literature, these terms have different meanings. Circular kneading is a technique commonly used in several massage methods, including Aronson, Roy et al., Mathieson et al., and Salehi and Barkmeier-Kraemer [5, 9, 22, 23]. However, the primary focus in the osteopathic LMT technique is stretching [13].

One debated aspect of LMTs is how manual techniques are implemented. Most LMTs have a specific protocol where the target structures, manual techniques, and massages are similar for all clients [5, 9, 21]. This means that the target structures, manual techniques, and massages used for all clients are nearly the same. However, not all LMT methods follow the same protocol. For example, in osteopathic LMT [13], the techniques are customized for each patient based on palpation results due to the numerous target structures involved. Having a specific protocol is advantageous because it is easy to implement and train. However, a main issue with this is that it overlooks the unique needs of patients. Specifically, there is a chance that certain areas that need special attention and manual techniques that could be more effective based on examination results may be ignored, while areas that do not have issues or manual techniques that are not as effective are given priority.

Overall, there is a need to improve and broaden the manual techniques used in LMT methods in the future.

Target Structures

Different LMT methods vary in the number and types of anatomical structures they target for intervention. Some techniques, such as MLMT, have fewer target structures [9], while others, such as osteopathic LMT, have more [13]. Generally, techniques with fewer target structures are easier to perform and train. The osteopathic LMT, with its higher number of target structures, requires certification. These target structures can include the hyoid bone, cartilage, muscles, spaces, and ligaments of the larynx. It is unclear why the hyoid bone and laryngeal cartilages are selected as targets, whether it is for ease of implementation and training as landmarks or to release tension in connected muscles and ligaments.

The target anatomical structures for the osteopathic technique are chosen based on the developers’ clinical experiences, scientific evidence, and the functional role of each structure during phonation. One of the unique aspects of the osteopathic technique is its focus on laryngeal joints, including the difficult-to-access cricoarytenoid joint. Other structures, such as palatal muscles and those related to the TMJ joint, are only considered in osteopathic techniques [13]. The selection of these target structures likely considers both clinical and theoretical reasons, as well as the ease of performing and training the technique. Some of these target structures are of critical importance in LMT techniques. In the MCT [5] technique, manual therapy is recommended for both suprahyoid and infrahyoid structures, whereas the osteopathic technique also considers neck, shoulder, and chest muscles outside of the larynx [13].

Several structures have been extensively targeted in LMT techniques, including the hyoid bone [5, 9, 13, 20–22], musculoskeletal structures of the TH [5, 13, 20, 22], and the CT [5, 13, 20, 22]. However, some structures, such as the omohyoid [7, 13], inferior constrictor muscle [7, 13], and SCM, have not received much attention [9, 13]. The hyoid bone is often chosen in LMT techniques because it connects the origin and insertion of the extralaryngeal muscles, and its position can change quickly. The TH and CT structures are targeted due to their crucial role in phonation from the biomechanical point. The omohyoid muscle has shown voice improvement when released based on clinical experiences, despite being less focused on. Although the pharyngeal constrictor muscles are rarely considered in LMT methods, clinical and research evidence suggests that MTD patients have a narrow pharyngeal space [46], which can be observed during palpation by narrowing lateral laryngeal channels [47] and laryngoscopic findings related to the pharyngeal cavity [46]. The SCM muscle is often the focus of certain LMT techniques [9, 13] because it is a common source of tension for people with MTD. These techniques reduce discomfort and tension in the SCM, which in turn helps to relax the suprahyoid structures [9]. It is not clear why other neck muscles such as the trapezius and scalene are not given the same attention in these techniques.

Overall, new LMT methods can target various structures based on the clinical experiences of working with MTD patients.

Tension Criteria

The reason for including tension criteria in introducing various LMT methods is to have measures to assess how much tension is reduced in the larynx during or after the treatment. Different LMT methods have different criteria for evaluating tension. When looking at the current LMT methods, it is evident that these tension criteria are typically defined in different ways depending on the laryngeal structures.

The tension criteria for (para) laryngeal muscles are pain[5, 9, 23, 24, 30], tightness [7, 13, 23, 24, 27, 30], tenderness [5, 7, 13, 20, 24, 30], nodularity [5, 24, 27, 29], and muscle resistance [9]. These criteria for laryngeal spaces are defined as closed or narrowed spaces [5, 22–24, 27, 29, 30], along with pain and tension [5, 22–24, 27, 29, 30]. Regarding the hyoid bone, tension criteria include pain or tenderness during palpation [5, 7, 9, 20, 22–24, 29, 30], resistance to movement [23], deviation from the midline [22], and its position mentioned in some references [22, 23]. There are some tension criteria regardless of specific anatomical structures. Two tension criteria for the larynx are laryngeal elevation [9] and decreased laryngeal mobility [7, 13]. In addition, other criteria include discomfort sensations such as feeling lump, globus or ball or voice changes [9].

As mentioned earlier, there are different ways to determine tension in this context. However, some of the differences in these methods are more about the terms used rather than actual variations in meaning. For example, “tightness” and “resistance” or “tenderness” and “pain” are used interchangeably. Additionally, the frequency of criteria of tension in different LMT methods is not the same. Some criteria, such as larynx elevation, are mentioned more often [5, 7, 9, 24, 27, 30], while others, such as laryngeal resistance, are mentioned less frequently [9]. Sometimes, different methods use different criteria to describe the same clinical feature. For instance, larynx elevation has been described in different ways in different studies. In one study [23] and other studies by Roy et al. [5, 24, 27, 30], closure of the TH space was used as an indicator of laryngeal elevation. However, in Mathieson et al.'s study, the distance between the cricoid and the clavicle was used as a measure of larynx elevation [9].

Overall, it is important to accurately and thoroughly determine the criteria for laryngeal tension before implementing an effective LMT using palpation methods. Also, objective evaluation methods using instrumental tools including surface electromyography, electroglottography, real-time elastosonography, and magnetic resonance imaging can be inserted into the clinical decision-making process for screening tension criteria. However, we need to consider whether the currently introduced criteria are sufficient or if they need to be changed.

Treatment Details

The treatment details for manual therapy include the position of the therapist and patient, the tasks during the intervention, the number and type of fingers used for massages, the number or time of massages, the distance between massages, the amount of pressure needed, and the number and length of treatment sessions. Some methods of LMT mention certain treatment details, but many important details are not mentioned in most methods of LMT [5, 9, 13, 24, 27, 29, 30]. The main goal of manual therapy is to reduce muscle tension, so it is important to design the treatment details in a way that effectively changes muscle tension. This requires knowledge of muscle physiology, how tension affects muscles, and details about manual therapy techniques. Providing this information not only makes it easier to teach students and therapists but also helps generate research evidence about the effectiveness of these techniques.

Due to the probable effect of treatment details on the educational aspects and effectiveness of the LMT methods, it is suggested that researchers and developers of LMT methods provide more information about these methods in the future to improve their educational aspects and effectiveness.

Conclusion

This review looked at different LMT techniques and compared them based on the manual therapy techniques they use, anatomical structures they target, and the criteria they use for tension. Based on the similarities and differences between these methods, it is important to create new LMT methods. These new methods should incorporate principles of muscle physiology and massage techniques to expand the manual therapy techniques used in LMT. It is also suggested to include more target anatomical structures, particularly soft tissues in the (para) laryngeal area. Additionally, new tension criteria should be developed to monitor tension reduction based on muscle behavior and theories in the field of MTD. The review also discussed the details of LMT methods. Overall, it is clear that voice therapy still has a long way to go in the development of LMT techniques.

Supplementary Information

Below is the link to the electronic supplementary material.

Abbreviations

MTD

Muscle tension dysphonia

LMT

Laryngeal manual therapy

SLP

Speech-language pathology

MCT

Manual circumlaryngeal therapy

TH

Thyrohyoid

SCM

Sternocleidomastoid

CT

Cricothyroid

TMJ

Temporomandibular joint

MLMT

Mathieson’s LMT

VM

Voice massage

CVM

Cricothyroid visor maneuver