Conservative approaches to the management of voice disorders.

The presence of a voice disorder not only affects social interaction but potentially also has a major impact on the work environment. The latter is becoming more important given the increasing demands employers make in terms of competency in both communication skills and adequacy of phonation. The development of newer and more precise phono-microsurgical techniques for the treatment of an increasing variety of voice disorders has not entirely replaced a conservative approach to voice rehabilitation. Nevertheless, conservative methods have to demonstrate an higher effectiveness in comparison with the microsurgical intervention given the alternative indications. This would be especially true for the more specific and systematically a given individual glottic pathophysiology could be changed in direction of individual phonatory physiology or supplementary phonation mechanism. This desired changing depends not only on the theoretical concepts but also on maintaining strict therapeutic principles during their clinical application. Conservative management of voice disorders has to be intensive and comprehensive, especially in the case of accepting our model of Larnygeal Double Phonation Function and the existence of a phonatory feedback loop.

1. Voice Disorder and Quality of Life

Voice disorders continue to be viewed as mere fabrications since the patient is generally very healthy and able to carry out their actvities of daily living competently. However the potential negative effect of any given voice disorder on both social interaction and performance at work, depending on its heavy reliance on both adequate communication skills and phonatory function, is frequently overlooked. A study from the US in 2000, examining the importance of adequate communication skills required for employment, identified an increase from 20% in 1900 to the current level of 63% [1]. Normal vocal function is required for a greater variety of occupations than has been previously realized [2], [3], [4], [5]. The importance of normal phonatory function at work is demonstrated by the fact that 76% (108/174) of voice disorder patients are concerned about their place of employment and their potential for promotion when compared to 19 % (31/173) in a control group [6]. In the same study, 73,5% (125/174) of patients reported a negative effect on their social interaction based on their voice disorder when compared to 11,1% (31/173) in the control group. Voice disorders are a major impediment for the patient and can result in a significant psycho-physiological burden and considerable anxiety. This is supported by our daily clinical experience.

The treating physician needs to carefully and seriously consider the negative consequences of a voice disorder [7] on the quality of life of any patient especially when there exists the opportunity for rehabilitation given conservative and/or phono-microsurgical approaches [8], [9], [10], [11], [12], [13]. Successful vocal rehabilitation relies on early intervention. Success is not only measured by the extent of return to normal phonation but also in terms of the rapid minimization and avoidance of unnecessary negative secondary effects due to a unnessessarily prolonged voice disorder. The degree of success depends not only on the content of the therapeutic approach but also on the conditions of treatment, which generally are underestimated. For instance, voice therapy should be viewed as intensive and daily [14] and require no treatment lasting months. Only one or two sessions a week could not be substituted by unsupervised exercises carried out by the patient at home.

Changes in sound and/or reduction in vocal performance with increased demand are the main symptoms in patients with voice disorders. These pathognomic symptoms are the result of a general phonatory disturbance that is due to varying dysfunction present in all aspects of normal voice production (Table 1 (Tab. 1)). The degree of phonatory disturbance also depends on each patients psychosocial state and their individual vocal sensibility. It is however unrealistic to assume that direct therapeutic intervention of these partial dysfunctional components per se causes a normalization of the general phonation function and leads to a healthy and resilient voice. Relevant outcome studies are currently not regularly conducted despite international agreeance about the existence of well established, objective measurable physical links between the extent of vibrational irregularity and/or shortened or incomplete closure of vocal folds vibration corresponding to varying degrees of the psychoacustic-perceptive hoarseness [15], [16], [17], [18], [19].

Table 1

Pathophysiology of a disordered voice

2. Objectives of Conservative Approaches

The primary aim of conservative voice therapy is to achieve a individual-physiological normalization of the voice. The end-point of treatment should not rest with the technical optimization of laryngeal dysfunction but rather the patients own natural voice. The desired functional outcome depends primarily on the nature of the pathophysiological process present within the larynx and their therapeutical changing. Examples include trauma to or integrity of laryngeal structures, the nature and extent of glottal insufficiency and presence or loss of muscle tone. The specialist needs to establish and document the precise diagnosis of this underlying pathophysiological process. It is vital that this is discussed with both the physician and the therapist before embarking on treatment. Optimally this is carried out conjointly with the patient and the treating team during which time a video of the changed patients laryngeal findings are discussed. This is not only vital at the outset of therapy but also important during all stages of treatment.

It is then obvious that the natural end-point of therapy does not always mean normalization of voice function [7], [20], [21]. Only too often are varying degrees of improvement in "any" laryngeal hyperfunction seen as relative success stories after only 2 to 3 outpatient sessions or less with previous operative intervention [22], [23], [24]. According to our own principles, voice outcomes ideally need to be documented objectively pre- and posttherapeutically using both videoendoscopic and objective acoustic analyses. In addtion aerodynamic parameters such as subglottic pressure need to be included in the objectification of treatment outcome [19], [25], [26], [27], [28], [29]. However in reality these measurements are far from routine in the management of patients with voice disorders.

3. Preconditions for the Development of Treatment Objectives

Targeted change from the concrete laryngeal pathophysiology in direction of or in the best case to physiology of the patients own voice, requires expert knowledge of normal laryngeal physiology. In addition a fundamental prerequisite for a successful outocme is the comprehensive knowledge of the pathophysiology of voice disorders and their treatment. The voice therapist requires an ability to interprete sophisticated clinical findings and to create profound internal visualization of what has to change and how to manage this task. Important aids include state of the art videoendoscopic demonstration and/or photographs in the report.

Voice therapists are expected that they clearly understand and are convinced of the potential for realization of the management objectives based on each individual clinical finding. The therapeutic repertoire needs to be adapted to the individual objectives of treatment. In addition voice therapists needs to be proficient in their application. In this way, voice therapists can develop an experience and continue to develop and refine their strategies based on critical self-analysis of relevant successes and failures. In this way every treatment event serves the purpose of not only testing each voice therapists personal understanding of both normal and abnormal voice physiology but also facilitates comparison with current literature. It is our belief that the outcome of a professional conservative regime, based on a minimum of one private session a working day, will be found to be highly efffective. This is not only in terms of normalization of voice but this approach also serves as a stimulant for future research and development of more sophisticated treatment methods. Sometimes grouptherapy is also of benefit in particular in the application of the accent method [s. 5.1] or within an inpatient setting.

4. Holistic Approach

A plethora of differing therapeutic strategies with varying sucess have been described for the management of voice disorders, a comprehensive review of which is beyond the scope of the current review. An example includes the Fernau-Horn method whose application is based on both individual preference and experience [30]. Up to now the main number of approaches could be collect in this chapter. The basic belief and common to all these differing strategies is the concept, that „ disturbance of the Body-Soul-Spirit-Complex " would be the cause of the majority of voice disorders. For further information on the specifics of each approach, we recommned a well-written review article that summarizes salient features of each technique [31].

4.1 Multidirectional Therapeutic Approach

The basis for the majority of therapeutic regimes described in the current article is an unpublished logopaedic concept [32], which has been "widely accepted" by therapists with some modifications and ongoing critical review [33], [34], [35]. The object is to create a "physiological voice" with modification in the 5 areas of the patients personality, intention, tone, respiration and phonation/articulation. The success of the individual treatment regime does not require precise specialist documentation of the integrity of phonatory function but rather rests on the therapists overall impression of the general state of the voice and the personality of the patient. The aim of voice therapy has to orientate itself "on the human individuality rather than on the particular method".

Depending on the detail of the symptom complex or clinical findings, voice therapy needs to focus on those factors that are most dominant: changes of sound are corrected with voice exercises, tension dysphonias or hyperfunction are managed with either general or local relaxation and self-awareness techniques, pathological respiration is treated with breathing exercises etc. Relevant psychotherapeutic elements of voice therapy are of almost greater importance than functional exercises in managing the individual patient with a voice disorder. Ultimate success of therapy rests on viewing the patient as an individual, with their own distinct spirit-soul-body-complex, within their own environment.

4.2 The Schlaffhorst-Andersen Voice Therapy

The Schlaffhorst-Andersen method is another example of a holistic approach to voice therapy. It focuses primarily on "the effort of respiration " via "body-orientated and autonomous posture and movement therapy" [36]. The authors recognize the importance and potential effect of emotion on the quality of the voice and therefore indirectly consider it as part of their therapeutic approach.

4.3 Assessment

There is no defined therapeutic protocol in terms of number of treatment sessions nor are there any objective and validated outcome measures available for the above-mentioned voice therapies. In conjunction with unsupervised home voice exercises, in general only 1 to 2 sessions per week are routinely scheduled. Therefore many outpatient-based regimes can take months and even occasionally last longer than 1 year. Aside from anectodal evidence reporting relative success of various conservative postoperative approaches to voice rehabilitation, we are not aware of any reliable and critically reviewed outcome studies. This is not suprising when compared to a more systematic and pathophysiologically orientated approach [37], [38], [39], [40], [41].

5. Selection of Methods

5.1 Accent Method (Svend Smith)

The primarily movement orientated Accent Method [42] turns off the patient´s conciousness from the inclosed phonatory mechanism and strikes a balance between subglottic pressure and glottal activity. It seeks to optimize flexibility of voice generation independent of either the origin or type of voice disorder. The therapist conducts various walking exercises in different musical tempos (Largo, Andante, Allegro) with the rhythm of a hand drum in synchronicity with specific soft-phonatory tasks to a particular vowel. This dynamic interplay between the therapist and patient creates a very friendly, happy and relaxed atmosphere, the result of which allows the patient to test the dynamics of their voice and explore the maximum potential of phonation. This method is therefore very appropriate within both a private or group setting [43] and can very effectively be integrated into any other treatment concept.

5.2 Nasal Reflecting Method (Pahn)

The aims of this method in treating patients with voice disorders lie in both rehabilitation and prevention, which are based on individual techniques of phonation during both speaking and singing [44]. For example, sounding a vowel with open mouth and closed nose achieves due to relaxed soft palate the immobilization of the oropharynx and inactivates relevant laryngeal levator musculature thereby physiological lowering the larynx. This technique also allows the development of new terminology when trying to differentiate between the aetiology of various voice disorders. The treatment of "usogene" dysphonia achieves a very clear voice with this technique (nasal reflex positive) whereas those patients with a "organogene" type potentially only achieve a partial reponse. Practicing this technique in the first instance removes any abnormal tension asscociated with articulation. Depending on the individual aetiology and pathology, sensory ability, age, employment and social situation, this technique begins with downwards directed sound exercises during the natural speaking in the modal register with training of different melodic, dynamic and rhythmic movements.

5.3. Chewing Method (Froeschels)

This method has been practiced for many decades and is based on the developmental link between the phylogenetic primary function of mastication and the secondary activation of articulation [45]. The laryngeal musculature relaxes during the phase of mastication and therefore this knowledge allows intentional modification of abnormal tension that exists during pathological phonation. This technique achieves relaxation of the local musculature and therefore allows the unconscious expression of the natural and individual pitch of speaking voice. The strength of this technique lies in the restoration of the balance between relevant agonists and antagonists during natural phonation. This method should be part of the general repertoire of every therapist, especially if they believe in a diagnosis of "hyperfunctional" dysphonia and that it is the most common of all functional dysphonias [46], [47], [48].

5.4 Respiration adapted Phonation (Coblenzer / Muhar)

The aim of this exercise is the optimal coordination of respiration and speaking in respect of the 3 respiratory phases (inspiration, expiration and break) [49]. During this technique, the patient needs to first of all avoid rapid and noisy inspiration prior to speaking and starts the onset of phonation out of the mid-phase of respiration. Each speaking phrase should correspond to the individual length of expiration. Stop of articulation at the end of the sentence is much more controlled with this technique and this in addition also promotes natural inflow of air during the inspiratory phase of respiration The end result is a very individual and economical way of speaking. It is associated with a good level of comprehension, expression, resonance and greater efficiency. Overall the phonatory ability is resilient and robust.

5.5 Selective Current Therapy

This is still a very controversial discussed method of conservative voice rehabilitation especially for patients with laryngeal paralysis, that has been practiced for many decades. The aim of this method is to selectively strenghten paralysed or weakened laryngeal muscles with despite on the surrounding healthy neck musculature [50]. To stimulate only the pathological muscles of the larynx will be possible by their reduced accommodation capacity in comparison to the surrounding healthy musculature. So this prevents not only atrophy but leads to hypertrophy too with improved glottic closure in phonation. This result maintains the glottal competence furthermore without any need of a treatment again. Similar absolute indications for the application of this method are either accidental or operative laryngeal trauma leading to varying degrees of vocal cord immobility [20], [40], [51], [52]. Various symptomatic myopathies or a myriad of different functional dysphonias are relative indications. This method can be integrated into any alternate therapeutic regime with potential benefits of improving ultimate voice outcome.

5.6 Assessment

All the above-mentioned methods, except selective current therapy, can be applied to patients with either a normal or pathological larynx in order to achieve overall normal function in a holistic sense. It remains to be seen whether this aim can be realized in fact for various pathophysiological situations. Success with these methods is empirically reported without the availability of any reliable and validated outcome studies. All these techniques have specific and valid objectives which can be successfully integrated into any management concept and therefore should be part of actual therapists repertoire.

6. Functional Voice Therapy (Kruse) and Voice Rehabilitation (Goettingen Concept)

6.1 Laryngeal Double Valve Function

A fundamentally different approach has resulted from better understanding and new information about the physiology and pathophysiology of phonation. Phylogenetically, the primary function of the larynx include airway protection and as it´s variation especially the respiration regulating valve function up to the maximum of respiration stop during different periods of activity. Phonation is traditionally seen as a secondary function of the larynx. The functional link between phonation and the closure mechanism of the larynx is still valid however requires further clarification. Negus in 1929 [53] and later Pressman [54] again described 3 distinct endolaryngeal sphincter mechanisms: at the level of the vocal folds, the ventricular (not false) folds and at the laryngeal introitus (Figure 1 (Fig. 1)). The vocal folds therefore act as an inspiratory valve while expiratory endolaryngeal valve is built up by the supraglottis ie. either ventricular fold alone or combined with ary-epiglottis.

Figure 1

Anterior view of the larynx with topographic-anatomic representation of the vocal cords and ventricular folds. Schematic diagram of the „Laryngeal Double Valve Function" [54], [55]

There therefore exists a phylogenic primary "Laryngeal Double Valve Function" (DLVF). Singing teachers were the first to exploit this physiological fact for modification and training of the voice [55], [56]. These 2 distinct and separate functions of the larynx can be independently manipulated and stimulated depending on various types of physical activity. This has been verified via flexible videolaryngoscopy [39]. Physical activity that is predominantly inspiratory in nature can be categorized as "thoraco-petal" (ie. pull ups) and therefore stimulates the vocal cords, the glottal level. In contrast, physical activity that is mainly expiratory in nature is described as "thoraco-fugal" (weightlifting or abdominal pressing) and predominantly activates the forementioned supraglottic structures. Both mechanisms are tactile-kinesthetic clearly distinguishable as separate entities and individually self-controllable, independent of the musicality.

6.2 Laryngeal Double Phonation Function

Careful evaluation of video-endoscopic data has objectively identified the relationship between the physiology of phonation and the glottic valve-mechanism of the vocal cords [39]. When voice teachers have to train and optimize the physiologic voice or voice therapists have to treat a glottal phonation pathophysiology, they have to realize this in combination with whole body activities using the inspiratory activating principle. Thus, contemporary voice therapy has to be systematic active movement therapy in respect to further analogous to certain sport training, in particular it´s intensity [20], [57].

In contrast to it´s sphincteric functioning the supraglottis remains physiologically inactive during phonation. Supraglottic co-activation is only seen when phonation becomes pathological. Ventricular fold´s median movement and increasing constriction of supraglottic space are seen easily during laryngoscopy. This activation of the supraglottis during altered phonation seems to be a hyperfunctional compensatory, not wrong mechanism and nesserary for patient´s demands [58]. Subjective this compensation mechanism correlates with the well-known complex "discomfort within the throat" (ie. globus, persistent throat clearing, local or referred pain) [20], [39]. Therefore, improvement in glottal function and effectiveness of conservative voice therapy subjectivily could be controlled by reduction of this incomfortable complex.

6.3 Phonatory feedback loop and its diagnostic / therapeutic significance

Our concept of "Laryngeal Double Phonation Function" with involuntarily on-demand activation of supraglottic compensation, provides - in analogy to hormonal regulation - clear evidence for the existence of a also biologic self regulating mechanism of the phonatory function [20] (Table 2 (Tab. 2)). While up to now the central regulating processor remains unknown, according to both clinical and therapeutic data the sensory level of this feedback loop seems to be the glottic function by which the effect of such a feeback loop on laryngeal structures can be objectively measured [20], [41], [58]. The quality of the vocal cord´s vibration (regular/irregular etc.) and of the vibrational closure are obviously critical glottal parameters, disturbance of which lead to both physical and perceptive alteration of the voice signal [15], [16], [17], [18], [19], [59], [60] which psycho-acoustically is perceived as "hoarseness".

Table 2

Concept of „Laryngeal Double Phonation Function" [20]

In order to competently functional diagnose any voice disorder based on our hypothesis, the use of either a stroboscope or high-speed camera would be mandatory to precisely document glottic function. Conservative and/or phonosurgical approaches to optimal voice rehabilitation have to carried out on the basis of these relevant glottal pathological findings, not of the supraglottic compensation. This dominantly glottal approach is vital also for appropriate classification of voice disorders, choice of therapeutic approach and it allows objective measurement of treatment outcome. It is not the place to demonstrate these consequences on distinct organic or functional voice disorders.

6.4 Functional Voice Therapy (Kruse)

The first step in the therapeutical approach to any voice disorder based on our physiologic-pathophysiologic "functional" concept, is the precise differential diagnosis of glottic function [20], [39], [61], [62], [63], [64] (Table 3 (Tab. 3)) This is the primary responsibility of the specialized and qualified physician with the aid of a comprehensive diagnostic protocol (Table 4 (Tab. 4)). The following application of a such disease-specific conservative differential therapy has first of all to improve or to cure this concrete glottal pathophysiology with indirect the "automatically" reduction or removing of supraglottal compensatory mechanisms. Improved glottic function requires less supraglottic compensation [58]. The main objective of voice therapy is targeted change of specific glottic pathological findings. Like generally in medicine these may require different and individualized therapeutic approaches, ie. in the case different laryngeal paralyses other strategies than hypofunctional or mutational dysphonias [57], [62], [63], [64]. The ultimate prognosis is clearly different depending on the specific cause of voice disorders.

Table 3

Principles of Functional Voice Therapy (Kruse) [39]

Table 4

Phoniatric diagnosis of laryngeal function

There need to be significant differences in therapeutic approaches and objectives. For example breathing and relaxation exercises for the management of laryngeal paralyses are equally as ineffective as in our opinion too frequently prescribed voice rest. In contrast for these disorders the selective current therapy would be as indispensable as intensive, daily treatment session [50], [57]. In direct analogy to sport training, a better outcome can be realized more rapidly in patients with paralyzed laryngeal muscles if the treatment approach is appropriate and intense.

Possibly during or more likely after almost completion of disease-specific voice therapy the achieved result in glottic function´s improvement requires individual technical optimization. During this disease-unspecific part of therapy all patients have to re-discover their specific-treated voice, independent of the type of disorder, and learn how to control phonatory output, loudness and how to avoid excessive strain during all activities of daily living. Depending on the skills learned during voice therapy, home exercises become of benefit in achieving a voice satisfactory for all activities. However this should not come at the expense of intensive therapy directed by a trained therapist. The fact that this part of therapy is carried out independent of the specific nature of the voice disorder does not mean that this method is not systematic (Figure 2 (Fig. 2)). In this circle it starts with body activating exercises that are predominantly driven by the inspiratory phase of the respiratory cycle in combination with phonation or speaking. Following completion of therapy, during mandarory controls we continue to observe ongoing improvement in phonatory function. In addition this method contributes to prevent the development of future voice detoriation through more conscious self-controlled use of their voice.

Figure 2

Voice Function Circle (modified to Haupt) [34]

6.5. Functional postoperative voice rehabilitation (Goettingen Concept)

Normalization of voice is not possible if there is either operative or traumatic destruction of functionally important laryngeal structures. We have coined the term "substitute phonation" [20], [21], [41], [65], independent of the actual endolaryngeal level of phonation and the potential voice quality achieved with or without rehabilitation.

The loss of functionally important laryngeal tissue as it occurs for example after treatment of early glottic carcinoma, is unique in every situtation and in the first instance affects the quality of the voice. The resultant hoarseness or aphonia requires treatment like any other voice disorder, independent of aetiology. Conservative voice therapy is appropriate however requires some specific modifications to the one described previously.

A special type of voice rehabilitation is required for the post-operative or post-trauma situtation in order to achieve a individual-optimal "substitute phonation" [20], [21], [41]. Compared to voice therapy, voice rehabilitation requires functional and vibrational optimization of important laryngeal structures that have been traumatized and scarred [40], [41], [51], [52]. In addition this method seeks to establish a neoglottis and/or optimize this type of substitute phonation through the systematic utilization of still functionally intact laryngeal structures. It is therefore vital to avoid the excessive resection of uninvolved and normal tissue during tumor removal since this may have potential implications for the nature and quality of the substitute voice post rehabilitation [20], [21].

With some minor exceptions of special individual solutions, after minimally invasive laser resection [66], [67] of glottic carcinomas and all T-stages it was possible to restore a neoglottis at one of again 3 endolaryngeal levels: of the glottis, the ventricular folds or the ary-epiglottis [20], [21], [40], [41]. This corresponds to the 3 endolaryngeal sphincter mechanisms [53], [54] described previously. If phonation postoperatively remains at the level of the glottis, we differentiate between a "glottic" or "pseudo-glottic" type of substitute phonation based on the presence or absence of the operated vocal cord vibration capacity respectively. This clearly has implications for the final quality of voice after rehabilitation (Figure 3 (Fig. 3)). The distinction between these two clinical scenarios cannot be made by means of simple laryngoscopy (Figure 4 (Fig. 4)).

Figure 3

Goettingen Hoarseness Diagram (GHD) : Results of post rehabilitation „substitute phonation" in patients after minimally invasive laser resection for glottic carcinoma [66], [67]

Figure 4

Laryngoscopic images of glottic (left) and pseudo-glottic substitute phonation after partial chordectomy

Acoustic analysis using our newly developed "Goettingen Hoarseness Diagram" (GHD) allows two-dimensional documentation and quantification of voice quality [68], [69], [70], [71], [72], [73], [74], [75], [76], [77], [78], [79]. For the first time [22], [23], [74], [76], [77] this covers the entire sound spectrum from normal voice to aphonia. Review of acoustic postrehabilitative results has identified significant differences and a clear hierarchy in quality of substitute voice achieved with the various different levels of phonation. The various values obtained for the quantified degree of irregularity and noise present within each singular recording or in summarizing cluster are easily to see and pathophysiological precise to interprete in a validated objective manner.

The best voice is unsuprisingly obtained via a glottic substitute phonation. This is significantly better in terms of irregularity and/or noise components when compared to voice rehabilitation at the level of the supraglottis. Pseudo-glottic substitute phonation has far worse vibratory characteristics when compared to the quality achieved at the level of the ventricular folds. This comes at a small cost of a minor increase in breathiness. It is therefore not true that voice rehabilitation at the level of the glottis would be the best result in all cases, especially when pseudo-glottic phonation often results in an increased level of pitch. This is not desirable for the majority of male patients [37], [38]. Interestingly voice achieved at the level of the supraglottis continues to be gender-specific, which is not suprising given the fact that the the laryngeal framework generally remains intact. To compare the outcome in phonation to the voice of Louis Armstrong is, especially for women very confusing and unnecessary and therefore this should be discouraged.

The higher degree of irregularity and poor closure pattern seen in ary-epiglottic phonation is clearly asscociated with a worse voice quality however still objectively better when compared to tracheo-esophageal speech [13], [80]. Rehabilitation at the level of the supraglottis is also associated with a significantly better quality of life when compared to laryngectomized patients. In addition to these group analyses of outcome, the Göttingen Hoarseness Diagram allows the objective and reproducible measurement and documentation of all individual courses of rehabilitation, results of which can be either numerically or graphically represented [20], [21], [41], [73], [74], [75], [78], [79].

6.6 Asssessment

Our concepts of "Functional Voice Therapy", and "Functional postoperative Voice Rehabilitation" allows for the first time to our knowledge, a systematic approach to conservative treatment of voice disorders, irrespective of their aetiology [39]. This approach is based on profound understanding of evolutionary and pathophysiological principles of voice production. The advantage of this approach, in conjunction with the use of routine video-phonoscopy and objective voice analyses, is a better outcome achieved more quickly when compared with other contemporary therapies. In addition our approach allows precise and objective documentation of the quality of voice after therapy. The visual demonstration and explanation of all clinical findings in addition to being able to document change relatively quickly, allows the patients to actively participate in their treatment. This creates a sense of better understanding and leads to an increase in motivation and cooperation. Patients are therefore more ready to accept the intensive nature of therapy which requires at least 1 session a day. Without knowing the future definitive outcome, this systematic and pathophysiologically orientated approach rapidly provides precise and objective information, which is vital when informing the patient regarding the potential outcome and length of therapy. Treatment lasts approximately 2 to 6 weeks depending on the pathology and the complexity of therapy required.

We have over 10 years experience in performing conservative voice rehabilitation according to the Goettingen concept in patients, who have undergone minimally invasive laser resection of glottic carcinoma [66], [67]. Our results [20], [21], [41], [73], [74], [75], [78], [79], [80], [81] at least seem to equalize the voice results as far as the perceived functional advantages of radiotherapy [82], [83], [84], [85], [86], [87] of early glottic carcinomas (Tis,T1,T2) are concerned. In fact the opposite seems to emerge, with laser microsurgical resection having superior results in terms of both local control and voice quality. In the treatment of T2 carcinoma with primary radiotherapy for example, salvage total laryngectomy rates of up to 55 % are reported [88], [89]. In our only singular experience with rehabilitating patients post radiotherapy, we have observed a significant reduction in the ability of the irradiated glottis to vibrate. This is reminiscent of what we have reported in patients with "pseudo-glottic" substitute phonation. After primary radiotherapy it has been very difficult or indeed impossible to stimulate the vibrational capacity of the stiffened radiated vocal cord and adequately rehabilitate these patients. In our experience this seems to be apparantly worse than what can be achieved after laser microsurgical resection of early glottic carcinoma by conservative voice rehabilitation.

In general the laryngoscopically observed structurally normal vocal cord, as is also seems to seen after a course of radiotherapy, cannot be assumed to be also functionally normal (Figure 3 (Fig. 3), Figure 4 (Fig. 4)). One needs to be also cognizent of this fact when analysing laryngeal function post endolaryngeal reconstructive surgery. So for a perfect anatomic outcome in terms of „successful" medialization of a postoperative fixed vocal cord is not synonomous with re-establishing of glottal phonation [90], [91], [22], [23]. This is based on the fact that the phonatory feedback loop continues to function and therefore may continue to promote substitute phonation at the supraglottic, especially ventricular level. This requires ongoing conservative voice therapy in order to optimize ultimate this substitute voice outcome. We therefore recommend early consultation and involvement of an experienced phoniatrician in all aspects of the voice patients management. This includes the cooperative pre- and postoperative objective assessment and documentation of any relevant laryngeal pathophysiology and treatment outcome [21].

7. Evaluation of Voice Quality

Unfortunately there are no studies in the literature objectively and prospectively comparing quality of voice after either radiotherapy or minimally invasive laser resection and post-therapeutical voice rehabilitation [25], [22], [92], [93], [94], [95], [96], [97], [98]). The fundamental problem is a lack of well-validated and multicentric reproducable acoustic parameters, that can easily be measured in patients with all types of voice qualities between normal and aphonic and are also universally and internationally accepted [22], [25], [69], [76], [74], [77]. The Goettingen Hoarsness Diagram (GHD) is such a potential device that allows the objectification of quality of sustained vowel phonation and of a standard text analysis too [74], [77], [78], [79], [99], [100], [101], [102].

Subjective voice perception judgements continue to be favoured for the assessment of voice disorders, however are universally not useful or acceptable when attempting to carry out objective and multicentric outcome studies [59], [38], [60], [103], [104], [105], [106]. Phonetograms equally are of little at least scientific benefit [37], [38], [107], [108], [109], [110]. It waits to be seen, whether the basic protocol of voice analysis of the European Laryngological Society may fullfill such scientific demands [111], [112].

8. Conclusion

Voice disorders, whether they are due to early glottic carcinoma or of another aetiology, are neither fictitious nor fabricated. The approach to voice rehabilitation, which can be conservative, phono-surgical or a combination of both, depends entirely on a thorough assessment of laryngeal function and not just simple laryngoscopy [63], [64]. It is very important to carry out ongoing carefull controls of laryngeal function during the course of therapy, in order to observe any therapeutic changing into the supposed direction, would it be improvement, normalization or development of a substitute phonation. The results of treatment depend very much on the type, content and execution of a basic concept and require some basic knowledge regarding conservative voice rehabilitation methods from the involved physician in the same way as would be usual in controlling of surgical interventions. Individually suboptimal results seem to be the rule, however should not be accepted by the patient nor the therapist. They lead to the unfounded belief, that conservative voice therapy is of less or no therapeutic relevance and less effective than operative intervention [37], [38]. According to our experience however, when properly indicated, these conservative methods according to our pathophysiological concept, appear to be more beneficial and superior to surgical intervention, when ie. applied in either the postoperative rehabilitation [20], [39], [40], [41] or in patients with distict laryngeal paralyses [57], [63].