1 Henry Strong Denison Scholar for

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1 THE PALATE ANALOGUE: AN APPROACH TO UNDERSTANDING VELOPHARYNGEAL FUNCTION By A. LEE DELLON 1 and JOHN E. HooPES, M.D. Division of Plastic Surgery, The ffohns Hopkins University School of Medicine and Theffohns Hopkins Hospital, Baltimore, Maryland 212o5 FUNCTIONAL velopharyngeal relationships are being defined more precisely by means of cineradiography (Hoopes and Fabrikant, 1968 ; Yules et al., I968b). Meaningful application of the technique demands interpretation of the cineradiographic data within the total framework of the pertinent functional anatomical variables. For this reason it was found desirable to construct a functional mechanical model of the velopharynx (Fig. I A, B), referred to herein as a palate analogue. Description of the Model.--The palate analogue was constructed to represent the view of the velopharyngeal area displayed on a lateral cineradiogram (Fig. 2). Although such a view fails to consider lateral pharyngeal wall movements, investigations synchronising lateral cineradiography, horizontal tomograms and panendoscopic visualisation of velopharyngeal closure have demonstrated that the lateral view accurately describes velopharyngeal function (Bjork and Nylen, 1966). The velopharyngeal area includes the pharyngeal constrictor muscles, the palatoglossus muscle, the palatopharyngeus muscle, the levator and tensor veli palatini muscles and the uvular muscle. The palate analogue gives dynamic representation only to the levator and tensor veli palatini muscles and the palatopharyngeus muscle, since these are considered the principal muscles involved in palatal function. Further, the posterior pharyngeal wall is virtually stationary during phonation (Hagerty et al., 1958). The hard palate is represented by a rigid plate which is variable in position with respect to the posterior pharyngeal wall. The soft palate is represented by a flexible elastic structure which is variable in length. The posterior pharyngeal wall is represented by a fixed rigid plate. Three muscles : (I) levator veli palatini, (2) tensor veli palatini and (3) palatopharyngeus are represented bilaterally by silk ligatures which are variable in length, i.e., can be " contracted ". The levator insertion is variable in position throughout the length of the soft palate. Operation of the ModeL--Operation of the palate analogue enables an evaluation of the influence of depth of nasopharynx, length of soft palate, position of levator insertion, angle of the plane of the hard palate and muscle interactions upon velopharyn- ' geal function. " Contraction "of the levator veli palatini (produced by traction on the silk ligatures) results in elevation of the soft palate and velopharyngeal closure when the parameters are in a "standard" or "normal" configuration. Varying types of closure, or lack of closure, can be demonstrated by increasing the depth of the nasopharynx, decreasing the length of the soft palate, anteriorly displacing the point of levator insertion, or varying the angle between the plane of the hard palate and the posterior pharyngeal wall. Operation of the palate analogue qualitatively demonstrates that velopharyngeal closure can be dassitied as good closure, touch-closure, or no closure. No closure, i.e. velopharyngeal incompetence, can be shown to result from positioning the component 1 Henry Strong Denison Scholar for

2 THE PALATE ANALOGUE: UNDERSTANDING VELOPHARYNGEAL FUNCTION A B FIG. I The palate analogue. A. Three muscles : (I) levator veli palatini, (2) tensor veli palatini, and (3) palato-pharyngeus are represented bilaterally by silk ligatures which are variable in length, i.e., can be " contracted ". All components of the palate analogue are variable in position. B. " Contraction " of the levator veli palatini results in elevation of the soft palate and velopharyngeal closure when the parameters are in a "standard " or "normal " configuration. The levator insertion is variable in position throughout the length of the soft palate. 257

3 258 BRITISH JOURNAL OF PLASTIC SURGERY parts of the palate analogue such that there is : (I) an anterior insertion of the levator veli palatini muscle, (2) a deep nasopharynx or (3) a short soft palate. The palatopharyngeus, by virtue of the posterior component of its vector of action, can assist closure and can effect a tight seal in cases of touch-closure. The antagonistic action of the tensor veli palatini can prevent closure. f--[ q/ re-- / FIG. 2 Schematic view of palate analogue model. Velum is partially elevated. Letters A, ]3, and C represent positions to which soft palate may be relocated to shorten length of soft palate. Numerals x, II, III represent positions to which hard palate may be relocated to increase depth of nasopharynx. The holes in the soft palate represent positions into which the levator veli palatini muscle insertions may be relocated. HP, hard palate ; SP, soft palate ; U, uvula ; PH, pterygoid hamulus ; LE, levator eminence ; PPW, posterior pharyngeal wall ; LP, levator veli palatini muscle ; TP, tensor veli palatini muscle; PP, palato-pharyngeus muscle; NP, nasopharynx ; NC, nasal cavity ; OC, oral cavity. Calibration of the Model.--Operation of the palate analogue visually demonstrates qualitative information regarding patterns of velopharyngeal closure. Calibration of the model enables a quantitative evaluation of functional velopharyngeal relationship. Construction of the model is not dependent upon cineradiographic measurements, since all the components of the palate analogue are variable in position and since> therefore, all proportions of this model velopharynx are variable. In order, however, to evaluate the patterns of velopharyngeal closure, construction and calibration of the model is based upon a set of parameters devised for quantitative cineradiographic analysis of palate function : ANS and PNS: The anterior and posterior extremities of the moveable rigid plate (the hard palate), representing the anterior and posterior nasal spines. The plane of the hard palate is represented in two dimensions by a straight line connecting the points ANS and PNS. This plane is extended through the posterior pharyngeal wall. PPIV : The posterior pharyngeal wall. U : The position of the uvular tip at rest. The length of the flexible elastic extension (the soft palate) is the distance PNS-U.

4 THE PALATE ANALOGUE: UNDERSTANDING VELOPHARYNGEAL FUNCTION 259 LE: The point at which the arc traversed by the levator eminence (the locus of action of the levator veli palatini represented by its point of insertion) during closure intersects the plane of the hard palate. Levator Insertion : The distance from PNS to LE. The shorter this is, the more anterior the levator insertion. Velopharyngeal Incompetence : The ratio of the distances LE-PPW and PNS-PPW, viz., LE-PPW/PNS-PPW. A measure of the "gap " or inability to achieve closure. Relative Depth of Nasopharynx: The ratio of the distances PNS-PPVZ and ANS-PPW, viz., PNS-PPVd/ANS-PPW, which incorporates possible covariance in length of the hard and soft palate. Relative Length of Soft Palate : The ratio of the distances PNS-U and PNS-PPIJ7, viz., PNS-U/PNS-PPVd. A measure of the functional length of the soft palate. A ratio of I.OO indicates a length of soft palate barely allowing U to approximate PPW. The scale of the model is determined by comparing normal ANS-PNS values (7 mm.) with the ANS-PNS measurement of the palate analogue (200 mm.), with the relative depth of nasopharynx on the model set to equal the relative depth of the nasopharynx in the average normal individual (Hoopes et al., 1969, 197o); the scale, therefore, is 70 : 2oo or o'35 : I. Quantitative Assessment of the ModeL--Information defining the interaction between soft palate length, depth of nasopharynx and levator insertion in terms of the ability to achieve velopharyngeal closure can be obtained by systematically varying one of these anatomical parameters while maintaining the others constant. If each parameter is varied in turn, and the resulting degree of velopharyngeal incompetence and type of closure are measured upon the palate analogue, the information obtained may be plotted graphically (Fig. 3) to demonstrate functional velopharyngeal relationships. In Figure 3, lines I, II and III (depth of nasopharynx) represent the effect of varying levator insertion (the abscissa values) upon velopharyngeal incompetence (the ordinate values) and upon type of closure (the clear and cross-hatched areas). The arcs labelled A, B, C, etc., represent soft palate length. For a given soft palate length, those values on lines I, II, III below (downward and to the right) the intersection with the arc cannot exist, demonstrating the limiting relationship between soft palate length and velopharyngeal closure. The type of velopharyngeal closure, i.e., good closure, touchclosure, or no closure, is seen to be a function of several variables (levator insertion, depth of nasopharynx, soft palate length) and cannot be determined by knowledge "of any one variable alone. Mathematical analysis of the relationship between the position of levator insertion and velopharyngeal closure explains why functional velopharyngeal relationships graph as a family of straight lines (I, II, II in Figure 3) differing only in their slope. Given the statistic " levator insertion" equal to "x " and defined as the distance PNS-LE, the statistic "velopharyngeal incompetence" equal to " y" and defined as the ratio of the distances LE-PPW/PNS-PPW, and the fact that the sum of the distances PlqS-LE and LE-PPW equals the total distance PNS-PPW, we then have three equations which can be solved simultaneously. The solved equation, y = [(PNS-PPW)-x]/(PNS-PPW), can be put into the form y = mx +b, the equation of a straight line, i.e., y = (I/PNS-PPW)x + I. Since " m" is the slope of the line, and "b " is a constant, it is seen that for a given PNS-PPW (the depth of the nasopharynx) a straight line with a

5 260 BRITISH JOURNAL OF PLASTIC SURGERY negative slope results and that a change in depth of nasopharynx alters the slope of the line. A greater PNS-PPW (deeper nasopharynx) and/or a smaller PNS-LE (anteriorly displaced levator) insertion will increase LE-PPW/PNS-PPW (velopharyngeal incompetence). Velopharyngeal incompetence is, in general, independent of soft palate length, since LE-PPW/PNS-PPW is not a function of PNS-U. That the palate analogue can be used to predict accurately the degree of velopharyngeal incompetence of an individual whose velopharynx has been measured cineradiographically &LATE ANALOG FUNCTIONAL VELOPHARNGEAL RELATIONSHIP5 80 c~ 70. ~ 50- Ao ~ so- ~ 20- Q2 2~ 10- LEVATOR INSERTION (PNS-LE) (MM) FIe. 3 Graphic presentation of the relationships between levator insertion, depth of nasopharynx and velar length and their effect upon velopharyngeal incompetence and type of closure as demonstrated on the palate analogue. (See text for explanation of cross-hatched area.) may be demonstrated convincingly. In the Table data obtained from cineradiographic analysis of normal individuals and of patients with hypernasal speech secondary to cleft and submucous cleft palate (Hoopes et al., I969, I97 o) is compared with palate analogue pre- dictions. The cineradiographically measured levator insertion statistic can be converted to the scale of the palate analogue and used as the abscissa value on the graph (Fig. 3). The intersection with line I of a vertical line through the abscissa value determines the ordinate value, or degree of velopharyngeal incompetence, i.e., the predicted palate ana- logue value. It is apparent from the Table that the palate analogue accurately predicts quantitative values for human velopharyngeal function. The Table also demonstrates that the palate analogue can predict the type of velopharyngeal closure an individual is potentially capable of achieving if the individual's levator insertion statistic and relative depth of naso- pharynx are known from cineradiographic analysis. Cineradiographically, IOO per cent of normal individuals demonstrated good velopharyngeal closure, and IOO per cent of the patients with cleft palate demonstrated no closure. The palate analogue prediction is precisely the same. In the group of patients with submucous cleft palate, 75 per cent demonstrated no closure and 25 per cent demonstrated touch-closure. The palate analogue predicts the submucous cleft palate group to be in the cross-hatched area of the graph (Fig. 3). This zone must be regarded as an area of ambiguous interpretation in that any given patient with sufficient compensatory ability, i.e., anterior movement of the posterior pharyngeal wall, may achieve closure. observed if this ability is lacking or marginal. No closure or touch-closure is Application of the Model.--At the anatomical level, the palate analogue provides a dynamic view of the relationships between structure and function. At the speech pathology level, the palate analogue provides a powerful instructional tool capable of visually demonstrating the aetiology of hypernasality and nasal emission on the basis of anatomical variables. At the surgical level, the palate analogue provides an objective rationale for the selection of specific surgical techniques best suited to the individual case. With regard to this latter application, a patient's cineradiographic data can be converted to palate analogue scale and plotted on Figure 3 to illustrate graphically which of the

6 THE PALATE ANALOGUE: UNDERSTANDING VELOPHARYNGEAL FUNCTION 261 anatomical variables are abnormal and to what degree surgical correction is required. Decisions regarding palate lengthening procedures and/or surgical augmentation of the posterior pharyngeal wall can be entered into with precision. TABLE A comparison of data obtained from cineradiographic analysis of normals, cleft palate, and submucous cleft palate patients with predictions made from the graph of velopharyngeal relationships obtained with the palate analogue. Cineradiographically Measured Data Palate Analogue Predictions Velopharyngeal Incompetence Normals 12 % I 1% Submucous cleft Cleft palate 35 ~o 51 ~o 34% 53 % Type of Closure Normals IOO~o good closure loo% good closure Submucous cleft 25% touch-closure touch-closure 75% no closure Cleft palate IOO~o no closure IOO~o no closure SUMMARY A model for velopharyngeal function, the palate analogue, has been described. The palate analogue is basically a manual analogue computer which is "programmed" to "read out" visually in terms of velopharyngeal incompetence and type of closure after being "fed" such data as levator insertion, depth of nasopharynx, and soft palate length. The palate analogue's ability to predict the relationships between the complex anatomical variables of velopharyngeal function is presented, and these predictions are compared with data obtained from cineradiographic analysis of patients with normal and cleft palate speech. Applications of the palate analogue to the fields of anatomy, speech pathology and surgery are discussed. REFERENCES BJORK, L. and NYLEN, B. O. (1966). Studies on velopharyngeal closure. Acta chit. scand., I31, 226. HAGERTY, R. F., HILL, M. J., PETTIT, M. S. and KANE, J. J. (1958). Posterior pharyngeal wall movement in normals. J. Speech Hearing Res., I, 2o3. HoovEs, J. E., DELLON, A. L., FABRmA~T, J. I. and SOLIMAN, A. H. (1969). The locus of levator veli palatini function as a measure of velopharyngeal incompetence. Plastic reeonstr. Surg., 44, 155. HooPES, J. E., DELLON, A. L., F~RmANT, J. I. and SOLIMA~r, A. H. (197o). Cineradiographic definition of the anatomical variables responsible for cleft palate speech. Br. ft. plast. Surg. In press. HOOPES, J. E. and FABRIKAlqT, J. I. (1968). Objective evaluation of cleft palate speech. Plastic reconstr. Surg., 42, I. YULES, R. B. axad CHASE, 1:{. A. (1968). Quantitative cine-evaluation of palate and pharyngeal wall mobility in normal patients, in deft palate patients, and in velopharyngeal incompetence. Plastic reeonstr. Surg., 4I, 124. YULES, R. B., NORTHWAY~ W. H. and CHASE, R. A. (1968). Quantitative cine-radiographie evaluation of velopharyngeal incompetence. Plastic reconstr. Surg., 42, 58.