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Partial myotomy in temporomandibular pain dysfunction: A preliminary communication
British Journal of Oral Surgery (1972), IO, 154-157
PARTIAL MYOTOMY IN TEMPOROMANDIBULAR PAIN DYSFUNCTION: A PRELIMINARY COMMUNICATION E. H. COOPER,B.D.S., F.D.S.
Royal Lancaster Infirmary, Lancaster Description o f a Case. A 29-year-old postman attended hospital in March I968 complaining of a swelling over the lower half of the left ramus of the mandible which had been present for more than two years. It had recently become painful. The left masseter and the left angle of the mandible were seen to be larger than those on the right. There was slight tenderness over the centre of the swelling but tenderness was more marked in the region over the lower part of the anterior border of the ramus and below the left zygoma. There was much attrition of the lower front teeth on the left side. The pain was controlled for a time with an upper bite plate but one year later he was anxious to have the masseteric asymmetry corrected surgically in the hope that the pain would go with the swelling. At operation in April 1969, the left masseter was approached througk a vertical incision over the anterior border of the ramus and the muscle tissue was removed until the two sides were judged to be of equal bulk. As Hankey advises (1968) it is necessary to keep hold of the tissue to be removed while incisions are made otherwise it retracts and disappears. A vacuum drain was maintained for 24 hours but was not entirely successful and a haematoma developed. As a result it was not until six weeks later that the swelling had diminished sufficiently for it to be confirmed that acceptable symmetry had been achieved. Two weeks after operation all pain cleared up and 2½ years later still has not returned. S u b s e q u e n t Cases. It had seemed possible that the hyperplasia and the pain were both due to muscle over-activity and if so, that excision of part of the muscle would, at least temporarily, prevent this anomaly and relieve the pain. So successful was the outcome that it was decided to try the effect of partial myotomy in other cases of temporomandibular joint pain-dysfunction syndrome, provided that: (I) the symptoms were severe; (2) the usual means of treatment had already failed; (3) the muscles primarily involved were easily accessible to intra-oral surgery--thus limiting the procedure to the masseter and the temporalis. Using these criteria, eight cases have now been treated by division of the muscle fibres of the masseter or temporalis. O p e r a t i o n . The approach to either muscle is intra-orally through a vertical incision over the anterior border of the mandibular ramus. In the case of the masseter a bundle of superficial fibres, say o'5 cm in cross-section, is divided near to its attachment. At first the temporalis was dealt with by cutting through the tip of the coronoid process with a bur, but subsequently a corresponding bundle of muscle and tendon fibres has been simply divided with a knife close to the bone with less post-operative discomfort. Except for the first case, which was undertaken partly for cosmetic reasons, the tissue has simply been cut and none 154
PARTIAL MYOTOMY IN TEMPOROMANDIBULAR PAIN DYSFUNCTION I55 removed. Since the first case more care has been taken with the vacuum drain, and haematoma formation has not been repeated. Morphine is given for the first r2 post-operative hours and simple analgesics thereafter. Moderate trismus follows the operation and full opening returns after about four weeks. Neither facial asymmetry nor persistent loss of function has followed the operation. In all eight cases, once the immediate post-operative pain has subsided the patient has remained pain-free. TABLE Summary of cases
Case R.T. M.W. M.W. B.T. S.K. J.E. M.M.
Sex
Age at Operation
Duration of Pain Preoperatively
23 years 30 years 33 years 43 years 56 years 18 years 34 years 36 years
5 years I3months 2omonths 3omonths 5 years I9months Iomonths I9months
Structure divided at Operation Left temporalis Left masseter Right masseter Left coronoid tip Left coronoid tip Left temporalis Right temporalis Right masseter and temporalis
Duration of Post-operative Follow-up I9 months 32 months 26 months 26 months I3 months IO months 5 months 9 months
Muscle Pain and the Principles o f Treatment. The name Temporomandibular pain-dysfunction syndrome was suggested by Schwartz (I956). The symptoms are certainly those of pain and dysfunction, but it would be more appropriate if the name of the syndrome referred to the primary involved myofascial tissue rather than to the joint which is not. Myo-fascial pain is usually felt predominantly in one of the muscles of mastication rather than equally in all of them, and the distribution of the pain reflects the particular muscle or muscles being over-used. Myo-faseial pain is felt most severely where the muscle is attached to bone, because it is here that the pain nerve endings are most plentiful. Thus, the coronoid process is tender when the temporalis is involved and the anterior part of the zygomatic arch when the superficial part of the masseter is involved. In the same way, pain arising from over-activity of the external pterygoid muscle is felt in its attachment, namely, the condyle and neck of the mandible and capsule of the joint. Schwartz's book (I959) and its successor published after his death (Schwartz & Chayes, I968) form the fullest treatise on this subject. In the chapter on 'History and Clinical Examination' examination of the muscles of mastication is described including the origin of the external pterygoid but, curiously, not of its attachment. The mechanism of pain resulting from muscle over-activity is extensively discussed by Schwartz and Chayes and the reader is referred especially to Chapter I2 of their book. However, the joint component of the pain is not represented by them as being ofmyo-fascial origin, yet perhaps this is what it is[ Perhaps it is the L
156
B R I T I S H J O U R N A L OF ORAL SURGERY
pain and tenderness of sensitive structures to which the external pterygoid is attached which is no different in nature from the rather less frequent pain and tenderness of the extremities of the other muscles of mastication or the origin (as opposed to the attachment) of the external pterygoid to which Schwartz and Chayes do, in fact, refer. The whole range of treatment of myo-fascial pain is set out fully by Schwartz and Chayes. Ideally the aim of treatment is the reduction of muscle over-activity, and improvement may follow events as diverse as reassurance and explanation, the end of the A-level exams, the removal of an impacted third molar which is inducing tooth movement in front of it, the correction of occlusal faults in old dentures and so on. But in every series there seem to be a few cases which resist all non-surgical means of treatment. S u r g i c a l T r e a t m e n t . Surgery in the treatment of this syndrome has, hitherto, been confined to the joint region and it is now necessary to examine some of the operations which have proved successful. Ward's (I961) operation of dividing the mandibular neck could be said to be analogous to section of the tip of the coronoid process, as just described. Perhaps both operations succeed for the same reason, i.e. they reduce the over-activity of the muscle which is attached to the small fragment, in the one case, the external pterygoid and in the other, the temporalis. James's (I97I) version of condylotomy is carried out via an open approach and at a higher level, but it is a similar procedure with indications much the same as Ward's. Again, it is arguable that in his cases the pain was also of myo-fascial origin and was relieved by severing part of the attachment of external pterygoid, thus reducing its function. There is nothing special about the success of condylotomy in relieving the pain, which proves that this symptom arises anywhere other than in those parts of the condyle and capsule to which the muscle is attached. Indeed, there is nothing to prove that the nature of the pain is fundamentally different from the pain felt in the coronoid process, and which was relieved by its section as described in this paper. James refers to 'myotomy or tenotomy' as one possible surgical method of relieving the pain, but doubts whether it would succeed short of dividing the whole muscle and preventing its re-attachment. The results reported in this paper suggest that partial myotomy of the external pterygoid might indeed be successful, and it would be interesting to try it as an alternative to condylotomy, even though myotomy in this situation may be no easier technically than open condylotomy and would certainly not possess the simplicity of Ward's closed operation. On the other hand, the origin rather than the attachment of the external pterygoid is accessible through the mouth, and, therefore, theoretically possible to cure at least some cases of temporomandibular joint pain by partial myotomy in this region. Myotomy of the external pterygoid might shed some light on the real origin of the pain and such knowledge is badly needed for we still have to answer the question: 'Is the temporomandibular joint-dysfunction syndrome entirely a matter of myo-fascial pain and muscle dysfunction, or is this symptom complex when the pain involves the joint region (and it does not always do so), sometimes due to degenerative joint change' ? When there is X-ray evidence of degenerative joint change in the condyle head James carries out a high condylectomy removing, rather than simply severing,
PARTIAL
MYOTOMY
IN TEMPOROMANDIBULAR
PAIN
DYSFUNCTION
I57
a part of the condyle. His indications and operation are similar to those of Henney (I957). These operations relieve the pain in a high proportion of cases, but again it does not follow that the symptom resulted directly from degenerative change in the removed tissue. It may be the alteredfunction which follows the operation that is responsible for the cessation of pain. This is not an important distinction! If the pain is myo-fascial, then the condition hangs together with all the other symptoms in the syndrome and the mechanism of the pain can be reasonably well understood. If, on the other hand, the c o m m o n condition of degeneration of the mandibular joint is occasionally responsible for pain, then a new factor is introduced and the reason why the pain should arise and the mechanism of its production become far from understood. T o resolve this problem, partial myotomy may offer some assistance. The number of cases reported in this paper is small but the operations referred to are simple. The results have been dramatic and they can easily be repeated by others. If, as a result, it becomes accepted that partial myotomy is a successful method of arresting myo-fascial pain in the masseter and the temporalis, then its extension to the external pterygoid should stop myo-fascial pain in that muscle too. Nevertheless, it would presumably fail to relieve pain from a degenerated condylar head if, in fact, pain does arise from such a source. SUMMARY Division of muscle fibres as a method of relieving myo-fascial pain in the masseter and temporalis is described. Its use is suggested when non-surgical measures have failed and where the pain is mainly confined to either the masseter or temporalis. It is further suggested that muscle section might be used experimentally to throw some light on pain located in the joint region. REFERENCES HANKEY, G. T. (1968). BritishJournal of Oral Surgery, 6, 123. HENNEY, F. A. (1957). Journal of Oral Surgery, 15, 24. JAMES, P. (1971). Annals of the Royal College of Surgeons of England, 49, 31o. SCHWARTZ,L. (1956). ffournal Chronic Diseases, 3, 284. SCHWARTZ,L. (1959). Disorders of the Temporomandibular Joint. Philadelphia: Saunders Co. SCHWARTZ & CI-IAYES (1968). Facial Pain and Mandibular Dysfunction. Philadelphia: Saunders Co. WARD, T. G. (1961). Annals of the Royal College of Surgeons of England, 28, 139.
PARTIAL MYOTOMY IN TEMPOROMANDIBULAR PAIN DYSFUNCTION: A PRELIMINARY COMMUNICATION E. H. COOPER,B.D.S., F.D.S.
Royal Lancaster Infirmary, Lancaster Description o f a Case. A 29-year-old postman attended hospital in March I968 complaining of a swelling over the lower half of the left ramus of the mandible which had been present for more than two years. It had recently become painful. The left masseter and the left angle of the mandible were seen to be larger than those on the right. There was slight tenderness over the centre of the swelling but tenderness was more marked in the region over the lower part of the anterior border of the ramus and below the left zygoma. There was much attrition of the lower front teeth on the left side. The pain was controlled for a time with an upper bite plate but one year later he was anxious to have the masseteric asymmetry corrected surgically in the hope that the pain would go with the swelling. At operation in April 1969, the left masseter was approached througk a vertical incision over the anterior border of the ramus and the muscle tissue was removed until the two sides were judged to be of equal bulk. As Hankey advises (1968) it is necessary to keep hold of the tissue to be removed while incisions are made otherwise it retracts and disappears. A vacuum drain was maintained for 24 hours but was not entirely successful and a haematoma developed. As a result it was not until six weeks later that the swelling had diminished sufficiently for it to be confirmed that acceptable symmetry had been achieved. Two weeks after operation all pain cleared up and 2½ years later still has not returned. S u b s e q u e n t Cases. It had seemed possible that the hyperplasia and the pain were both due to muscle over-activity and if so, that excision of part of the muscle would, at least temporarily, prevent this anomaly and relieve the pain. So successful was the outcome that it was decided to try the effect of partial myotomy in other cases of temporomandibular joint pain-dysfunction syndrome, provided that: (I) the symptoms were severe; (2) the usual means of treatment had already failed; (3) the muscles primarily involved were easily accessible to intra-oral surgery--thus limiting the procedure to the masseter and the temporalis. Using these criteria, eight cases have now been treated by division of the muscle fibres of the masseter or temporalis. O p e r a t i o n . The approach to either muscle is intra-orally through a vertical incision over the anterior border of the mandibular ramus. In the case of the masseter a bundle of superficial fibres, say o'5 cm in cross-section, is divided near to its attachment. At first the temporalis was dealt with by cutting through the tip of the coronoid process with a bur, but subsequently a corresponding bundle of muscle and tendon fibres has been simply divided with a knife close to the bone with less post-operative discomfort. Except for the first case, which was undertaken partly for cosmetic reasons, the tissue has simply been cut and none 154
PARTIAL MYOTOMY IN TEMPOROMANDIBULAR PAIN DYSFUNCTION I55 removed. Since the first case more care has been taken with the vacuum drain, and haematoma formation has not been repeated. Morphine is given for the first r2 post-operative hours and simple analgesics thereafter. Moderate trismus follows the operation and full opening returns after about four weeks. Neither facial asymmetry nor persistent loss of function has followed the operation. In all eight cases, once the immediate post-operative pain has subsided the patient has remained pain-free. TABLE Summary of cases
Case R.T. M.W. M.W. B.T. S.K. J.E. M.M.
Sex
Age at Operation
Duration of Pain Preoperatively
23 years 30 years 33 years 43 years 56 years 18 years 34 years 36 years
5 years I3months 2omonths 3omonths 5 years I9months Iomonths I9months
Structure divided at Operation Left temporalis Left masseter Right masseter Left coronoid tip Left coronoid tip Left temporalis Right temporalis Right masseter and temporalis
Duration of Post-operative Follow-up I9 months 32 months 26 months 26 months I3 months IO months 5 months 9 months
Muscle Pain and the Principles o f Treatment. The name Temporomandibular pain-dysfunction syndrome was suggested by Schwartz (I956). The symptoms are certainly those of pain and dysfunction, but it would be more appropriate if the name of the syndrome referred to the primary involved myofascial tissue rather than to the joint which is not. Myo-fascial pain is usually felt predominantly in one of the muscles of mastication rather than equally in all of them, and the distribution of the pain reflects the particular muscle or muscles being over-used. Myo-faseial pain is felt most severely where the muscle is attached to bone, because it is here that the pain nerve endings are most plentiful. Thus, the coronoid process is tender when the temporalis is involved and the anterior part of the zygomatic arch when the superficial part of the masseter is involved. In the same way, pain arising from over-activity of the external pterygoid muscle is felt in its attachment, namely, the condyle and neck of the mandible and capsule of the joint. Schwartz's book (I959) and its successor published after his death (Schwartz & Chayes, I968) form the fullest treatise on this subject. In the chapter on 'History and Clinical Examination' examination of the muscles of mastication is described including the origin of the external pterygoid but, curiously, not of its attachment. The mechanism of pain resulting from muscle over-activity is extensively discussed by Schwartz and Chayes and the reader is referred especially to Chapter I2 of their book. However, the joint component of the pain is not represented by them as being ofmyo-fascial origin, yet perhaps this is what it is[ Perhaps it is the L
156
B R I T I S H J O U R N A L OF ORAL SURGERY
pain and tenderness of sensitive structures to which the external pterygoid is attached which is no different in nature from the rather less frequent pain and tenderness of the extremities of the other muscles of mastication or the origin (as opposed to the attachment) of the external pterygoid to which Schwartz and Chayes do, in fact, refer. The whole range of treatment of myo-fascial pain is set out fully by Schwartz and Chayes. Ideally the aim of treatment is the reduction of muscle over-activity, and improvement may follow events as diverse as reassurance and explanation, the end of the A-level exams, the removal of an impacted third molar which is inducing tooth movement in front of it, the correction of occlusal faults in old dentures and so on. But in every series there seem to be a few cases which resist all non-surgical means of treatment. S u r g i c a l T r e a t m e n t . Surgery in the treatment of this syndrome has, hitherto, been confined to the joint region and it is now necessary to examine some of the operations which have proved successful. Ward's (I961) operation of dividing the mandibular neck could be said to be analogous to section of the tip of the coronoid process, as just described. Perhaps both operations succeed for the same reason, i.e. they reduce the over-activity of the muscle which is attached to the small fragment, in the one case, the external pterygoid and in the other, the temporalis. James's (I97I) version of condylotomy is carried out via an open approach and at a higher level, but it is a similar procedure with indications much the same as Ward's. Again, it is arguable that in his cases the pain was also of myo-fascial origin and was relieved by severing part of the attachment of external pterygoid, thus reducing its function. There is nothing special about the success of condylotomy in relieving the pain, which proves that this symptom arises anywhere other than in those parts of the condyle and capsule to which the muscle is attached. Indeed, there is nothing to prove that the nature of the pain is fundamentally different from the pain felt in the coronoid process, and which was relieved by its section as described in this paper. James refers to 'myotomy or tenotomy' as one possible surgical method of relieving the pain, but doubts whether it would succeed short of dividing the whole muscle and preventing its re-attachment. The results reported in this paper suggest that partial myotomy of the external pterygoid might indeed be successful, and it would be interesting to try it as an alternative to condylotomy, even though myotomy in this situation may be no easier technically than open condylotomy and would certainly not possess the simplicity of Ward's closed operation. On the other hand, the origin rather than the attachment of the external pterygoid is accessible through the mouth, and, therefore, theoretically possible to cure at least some cases of temporomandibular joint pain by partial myotomy in this region. Myotomy of the external pterygoid might shed some light on the real origin of the pain and such knowledge is badly needed for we still have to answer the question: 'Is the temporomandibular joint-dysfunction syndrome entirely a matter of myo-fascial pain and muscle dysfunction, or is this symptom complex when the pain involves the joint region (and it does not always do so), sometimes due to degenerative joint change' ? When there is X-ray evidence of degenerative joint change in the condyle head James carries out a high condylectomy removing, rather than simply severing,
PARTIAL
MYOTOMY
IN TEMPOROMANDIBULAR
PAIN
DYSFUNCTION
I57
a part of the condyle. His indications and operation are similar to those of Henney (I957). These operations relieve the pain in a high proportion of cases, but again it does not follow that the symptom resulted directly from degenerative change in the removed tissue. It may be the alteredfunction which follows the operation that is responsible for the cessation of pain. This is not an important distinction! If the pain is myo-fascial, then the condition hangs together with all the other symptoms in the syndrome and the mechanism of the pain can be reasonably well understood. If, on the other hand, the c o m m o n condition of degeneration of the mandibular joint is occasionally responsible for pain, then a new factor is introduced and the reason why the pain should arise and the mechanism of its production become far from understood. T o resolve this problem, partial myotomy may offer some assistance. The number of cases reported in this paper is small but the operations referred to are simple. The results have been dramatic and they can easily be repeated by others. If, as a result, it becomes accepted that partial myotomy is a successful method of arresting myo-fascial pain in the masseter and the temporalis, then its extension to the external pterygoid should stop myo-fascial pain in that muscle too. Nevertheless, it would presumably fail to relieve pain from a degenerated condylar head if, in fact, pain does arise from such a source. SUMMARY Division of muscle fibres as a method of relieving myo-fascial pain in the masseter and temporalis is described. Its use is suggested when non-surgical measures have failed and where the pain is mainly confined to either the masseter or temporalis. It is further suggested that muscle section might be used experimentally to throw some light on pain located in the joint region. REFERENCES HANKEY, G. T. (1968). BritishJournal of Oral Surgery, 6, 123. HENNEY, F. A. (1957). Journal of Oral Surgery, 15, 24. JAMES, P. (1971). Annals of the Royal College of Surgeons of England, 49, 31o. SCHWARTZ,L. (1956). ffournal Chronic Diseases, 3, 284. SCHWARTZ,L. (1959). Disorders of the Temporomandibular Joint. Philadelphia: Saunders Co. SCHWARTZ & CI-IAYES (1968). Facial Pain and Mandibular Dysfunction. Philadelphia: Saunders Co. WARD, T. G. (1961). Annals of the Royal College of Surgeons of England, 28, 139.