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The incidence of ear symptoms in cases of malocclusion and temporo-mandibular joint disturbances
THE INCIDENCE OF EAR SYMPTOMS IN C A S E S OF MALOCCLUSION AND T E M P O R O - M A N D I B U L A R JOINT D I S T U R B A N C E S HILMAR MYRHAUG, M.D.
Bergen, Norway IT is a common observation that there is a functional connection between the masticatory apparatus and the ear, particularly the acoustic organ (Fig. I). Phylogenetically, the middle ear bones are interpreted as jaw bones passed over to the service of hearing. The tympanic and palatine tensor muscles are, likewise, interpreted as originally being masticatory muscles because, among other things, they have a common nerve supply from the trigeminal nerve. In this connection, the locomotor system of the middle ear, consisting of the malleus, the incus and the stapes and the two muscles, the stapedius and the tensor tympani muscle, have a characteristic anatomical build up. In the joints between the three ear bones, the capsule consists of elastic connective tissue fibres and not of collagen fibres as is usually found in other joints. The tendon of the middle ear muscles is also of the elastic type (Fig. 2), and the same is true of the tendon attaching the foot of the stapes to the fenestra ovalis. The suspension of the soundconducting apparatus in the middle ear is, thus, very elastic and labile. Tensile equilibrium in the two middle ear muscles is required, or the whole system will easily come out of balance. This is what happens in a certain number of our temporo-mandibular syndrome cases. In the period 1952-6I, the author registered I39I patients who sought help because of neuralgic type pains of the face, headache and temporo-mandibular arthrosis resulting from bite anomalies. Of these, 378 had noticed disturbances of equilibrium. This was revealed partly by unpleasant feelings of unsteadiness on rising from a bending position, by severe degrees of incapacitating giddiness in which the patient could not follow his work, and by difficulty in walking alone in the street. There were 436 who had acoustic symptoms consisting of tinnitus, popping sensations in the ears and diminished hearing. 283 had noticed otalgia and 87 glossodynia. This means that approximately one in four patients with subjective disorders resulting from bite anomalies~ also, had disturbances of balance and hearing. A typical representative of this group of patients is a woman who was greatly troubled and incapacitated by vertigo for nine years. Her balance was upset, if for instance, she put her head back and looked up at the ceiling. After restoration of the bite, she could carry out all the housework including washing walls and ceiling. She had not been able to do this in all the nine years. 'I cannot understand it myself', was the comment she made about the immediate improvement in her health. That correcting an abnormal bite should improve ear symptoms will be puzzling to those who are not familiar with the anatomy and physiology of the ear, with the functional connection between the jaws and the sound-conducting system of the ear, nor with the phylogenesis of these parts. Bite anomalies regularly lead to tensions and contraction states in the masticatory muscles which can be demonstrated by electromyography. On the. 28
INCIDENCE
OF EAR S Y M P T O M S I N CASES OF M A L O C C L U S I O N
/
M. pteryqoideus ext.
Mandi bI~
Meckel~ c a r t ( I o q e
Pars squamosa
,,,-/'~
/~,~j \ , ~ ~ ~ ' . . ~
~
/,¢
29
maxiJlae
Lig. ant erior Incus
membrane
M. tensor tympani FI~. I Phylogenesis of jaw structures and middle ear bones.
o
. #I
•
°
-°d~. -
a
%
,,,
o
Section of the incudostapedial joint. The elastic fibres of the crapsule appear black.
Longitudinal section of stapedius muscle and tendon. The elastic fibres appear black.
FIG. 2 Elastic connective tissue fibres~'~in the joint capsules and muscle tendons o f the middle ear.
same basis, the two tensor muscles (tensor tympani and tensor veli palatini) are, also, influenced through their common nerve supply (nervus trigeminus). This has been demonstrated visually during operations for otosclerosis when the drum head is reflected. Contractions of the tensor tympani muscle can be watched directly under the operating microscope when stimulated voluntarily by grinning and clenching movements of the jaw. By contraction of the tensor tympani muscle, the shaft of the hammer is pulled inward and foreshortened. This can regularly be seen when there is a state of tension in the muscles innervated by the
30
B R I T I S H JOURNAL OF ORAL SURGERY
trigeminal nerve as a consequence of bite anomalies. The tympanic membrane will show a typical pattern in those cases. The light reflex is distorted or lost. Because of the strain to which the drum-head obviously becomes exposed, its blood supply is reduced. This often leads to the tympanic membrane becoming permanently thin, transparent and atrophic. Later, a sickle-shaped, grey-white precipitate is formed peripherally in the pars tensa called the arcus lipoides myringis. These more or less pronounced changes can be appropriately called
COCHLEA
Z
o
Arcus lipoides myringis and retractio membrana tympani.
ev
FENESTRA~ OVALIS 8. STAPES
=.M.TENSOR TYMPANI
vt.',STAP E DI US
TUBA
M'EMBRANA TYMPANI
~ PORUSEX~ACUS1
Hammer and sickle siqn of the tympanic membrane
FIG. 3 H a m m e r and sickle sign of the tympanic membrane.
the hammer and sickle sign of the ear (Fig. 3). Thus, with practice and experience and by studying the appearances of the tympanic membrane, one can see whether there are any stress abnormalities in the masticatory system. One may say that the drum-head reflects the functional state of the dentition. The compression of the chain of ear bones which one must, also, presume to exist with the retraction of the tympanic membrane, may lead to contusion of the chorda tympani in its course between the hammer and the anvil (Fig. 4). This anatomical relationship has not been previously connected with glossodynia, that smarting and burning sensation in the tongue which is usually unilateral and which has been observed many times to clear up after correction of bite defects. It is quite likely that there is a causal relationship here. Dysfunction of the masticatory muscles and the temporo-mandibular joint attributed to dental faults is found to be a frequent cause of neuralgia of the face and head. It is, therefore, no accident that these troubles always appear together with those peculiar disorders of ear function.
INCIDENCE
OF EAR S Y M P T O M S
I N CASES OF M A L O C C L U S I O N
31
It is mentioned by otologists that bite deformity is a known cause of tinnitus aurium. The sound which the patient hears, is not due to external sound waves as in the usual hearing reaction. This tinnitus arises as an autogenous vibration in the sound-conducting system, and it seems to be due to tremor or myoclonus (myorhythmia) in the tensor muscle of the middle ear. It represents a fatigue reaction resulting from prolonged irritation and stress of the muscles innervated by the trigeminal nerve (masticators). This form of fatigue reaction apparently only affects the small muscles in this group because of their anatomical relationship.
Chorda ~, tyrnpani
Malleus t Inc~.......~. c"
M. tensor ~
c"
.~I' ........%
~Cc' e Tub.. audir~va
Membrana tympani
FIG. 4 C h o r d a t y m p a n i p a s s i n g b e t w e e n t h e middle ear bones, malleus a n d incus.
Hence, the two tensor muscles are in a vulnerable position in bite anomalies. On rare occasions, objective tinnitus may appear. This sound can also be heard by a second person. The sound arises by means of rhythmic opening and shutting movements of the pharyngeal opening of the eustachian tube, and both tensor muscles will be involved. In the ordinary (subjective) tinnitus, the tensor tympani only is active. It is also a common observation that sufferers from otosclerosis regularly complain of tinnitus in connection to their impairment of hearing. These patients, for whose hearing the bell tolls, may well have an ailment of odontogenic origin. At the annual meeting of The Norwegian Society of Otolaryngology last year, the author compared the histology of otosclerotic bone with that of unilateral fibrous dysplasia of the maxilla in a boy with bite anomalies. It seems that the changes in the bone are similar in both instances and are caused by vibratory trauma to bone tissue. In otosclerosis, this is due to autogenous vibration of the sound-conducting apparatus with tinnitus, and in the particular form of maxillary fibrous dysplasia, it is due to traumatic occlusion on a solitary tooth. The fibrous transformation of bone seems to be caused by those physical irritants. With tension and compression of the sound-conducting structures, the impedance increases, and this entails what is known as functional diminution of hearing. Sometimes, this causes a fullness in the ear of fluctuating character in connection with tinnitus and often alternating with it. Paracusis and hyperesthesia acoustica may occur. There may, also, be autophony, a condition in which one hears one's own voice inside the head as if speaking into an empty barrel. In these
32
B R I T I S H JOURNAL OF ORAL SURGERY
cases, there is a contraction (spasm) in the tensor muscle of the soft palate causing a fullness in the ear and temporary deafness. It is relevant in the explanation of the vestibular type of vertigo, that the violent dizzy attacks generally start with strong and intense tinnitus and are often associated with headache. It is suggested that such attacks can arise from sudden and severe movements of the footplate of the stapes (Fig. 5). A ripple of the waves arise in the lymph of the inner ear which gives rise to these reactions and
tmph us erl$
FIG. 5 T h e organ of hearing and balance. Fluid motion in the l y m p h is indicated, the result of autogenous vibrations of the soundconducting apparatus in the middle ear, T h e cochlear as well as the vestibular structures of the inner ear is found to be influenced by this mechanism.
exerts an intermittent pressure on the walls of the labyrinth. This is similar to waves breaking on the shore. The hollowing out of the labyrinth found in Meniere's disease, called 'hydrops', may well be explained as the result of such pressure effects, as no real increase of pressure in the labyrinth has been measured. One constantly finds that vestibular and cochlear disorders go hand in hand, i.e. vertigo and deafness appear at the same time, as in Meniere's disease. The damage which can be shown to the respective sense cells for hearing and balance has obviously the same origin. In a few cases, the sense cells break down suddenly during an attack, but as a rule, the destruction takes place gradually over a period of years. A prolonged and troublesome tinnitus can be taken as a forerunner of this. By removing the causative factors which can be done by adequate restoration of the bite, the attacks can be checked and the subiective ear symptoms reduced or brought to an end. The issue here is an oto-dental syndrome which demands close co-operation between medical and dental practitioners.
Bergen, Norway IT is a common observation that there is a functional connection between the masticatory apparatus and the ear, particularly the acoustic organ (Fig. I). Phylogenetically, the middle ear bones are interpreted as jaw bones passed over to the service of hearing. The tympanic and palatine tensor muscles are, likewise, interpreted as originally being masticatory muscles because, among other things, they have a common nerve supply from the trigeminal nerve. In this connection, the locomotor system of the middle ear, consisting of the malleus, the incus and the stapes and the two muscles, the stapedius and the tensor tympani muscle, have a characteristic anatomical build up. In the joints between the three ear bones, the capsule consists of elastic connective tissue fibres and not of collagen fibres as is usually found in other joints. The tendon of the middle ear muscles is also of the elastic type (Fig. 2), and the same is true of the tendon attaching the foot of the stapes to the fenestra ovalis. The suspension of the soundconducting apparatus in the middle ear is, thus, very elastic and labile. Tensile equilibrium in the two middle ear muscles is required, or the whole system will easily come out of balance. This is what happens in a certain number of our temporo-mandibular syndrome cases. In the period 1952-6I, the author registered I39I patients who sought help because of neuralgic type pains of the face, headache and temporo-mandibular arthrosis resulting from bite anomalies. Of these, 378 had noticed disturbances of equilibrium. This was revealed partly by unpleasant feelings of unsteadiness on rising from a bending position, by severe degrees of incapacitating giddiness in which the patient could not follow his work, and by difficulty in walking alone in the street. There were 436 who had acoustic symptoms consisting of tinnitus, popping sensations in the ears and diminished hearing. 283 had noticed otalgia and 87 glossodynia. This means that approximately one in four patients with subjective disorders resulting from bite anomalies~ also, had disturbances of balance and hearing. A typical representative of this group of patients is a woman who was greatly troubled and incapacitated by vertigo for nine years. Her balance was upset, if for instance, she put her head back and looked up at the ceiling. After restoration of the bite, she could carry out all the housework including washing walls and ceiling. She had not been able to do this in all the nine years. 'I cannot understand it myself', was the comment she made about the immediate improvement in her health. That correcting an abnormal bite should improve ear symptoms will be puzzling to those who are not familiar with the anatomy and physiology of the ear, with the functional connection between the jaws and the sound-conducting system of the ear, nor with the phylogenesis of these parts. Bite anomalies regularly lead to tensions and contraction states in the masticatory muscles which can be demonstrated by electromyography. On the. 28
INCIDENCE
OF EAR S Y M P T O M S I N CASES OF M A L O C C L U S I O N
/
M. pteryqoideus ext.
Mandi bI~
Meckel~ c a r t ( I o q e
Pars squamosa
,,,-/'~
/~,~j \ , ~ ~ ~ ' . . ~
~
/,¢
29
maxiJlae
Lig. ant erior Incus
membrane
M. tensor tympani FI~. I Phylogenesis of jaw structures and middle ear bones.
o
. #I
•
°
-°d~. -
a
%
,,,
o
Section of the incudostapedial joint. The elastic fibres of the crapsule appear black.
Longitudinal section of stapedius muscle and tendon. The elastic fibres appear black.
FIG. 2 Elastic connective tissue fibres~'~in the joint capsules and muscle tendons o f the middle ear.
same basis, the two tensor muscles (tensor tympani and tensor veli palatini) are, also, influenced through their common nerve supply (nervus trigeminus). This has been demonstrated visually during operations for otosclerosis when the drum head is reflected. Contractions of the tensor tympani muscle can be watched directly under the operating microscope when stimulated voluntarily by grinning and clenching movements of the jaw. By contraction of the tensor tympani muscle, the shaft of the hammer is pulled inward and foreshortened. This can regularly be seen when there is a state of tension in the muscles innervated by the
30
B R I T I S H JOURNAL OF ORAL SURGERY
trigeminal nerve as a consequence of bite anomalies. The tympanic membrane will show a typical pattern in those cases. The light reflex is distorted or lost. Because of the strain to which the drum-head obviously becomes exposed, its blood supply is reduced. This often leads to the tympanic membrane becoming permanently thin, transparent and atrophic. Later, a sickle-shaped, grey-white precipitate is formed peripherally in the pars tensa called the arcus lipoides myringis. These more or less pronounced changes can be appropriately called
COCHLEA
Z
o
Arcus lipoides myringis and retractio membrana tympani.
ev
FENESTRA~ OVALIS 8. STAPES
=.M.TENSOR TYMPANI
vt.',STAP E DI US
TUBA
M'EMBRANA TYMPANI
~ PORUSEX~ACUS1
Hammer and sickle siqn of the tympanic membrane
FIG. 3 H a m m e r and sickle sign of the tympanic membrane.
the hammer and sickle sign of the ear (Fig. 3). Thus, with practice and experience and by studying the appearances of the tympanic membrane, one can see whether there are any stress abnormalities in the masticatory system. One may say that the drum-head reflects the functional state of the dentition. The compression of the chain of ear bones which one must, also, presume to exist with the retraction of the tympanic membrane, may lead to contusion of the chorda tympani in its course between the hammer and the anvil (Fig. 4). This anatomical relationship has not been previously connected with glossodynia, that smarting and burning sensation in the tongue which is usually unilateral and which has been observed many times to clear up after correction of bite defects. It is quite likely that there is a causal relationship here. Dysfunction of the masticatory muscles and the temporo-mandibular joint attributed to dental faults is found to be a frequent cause of neuralgia of the face and head. It is, therefore, no accident that these troubles always appear together with those peculiar disorders of ear function.
INCIDENCE
OF EAR S Y M P T O M S
I N CASES OF M A L O C C L U S I O N
31
It is mentioned by otologists that bite deformity is a known cause of tinnitus aurium. The sound which the patient hears, is not due to external sound waves as in the usual hearing reaction. This tinnitus arises as an autogenous vibration in the sound-conducting system, and it seems to be due to tremor or myoclonus (myorhythmia) in the tensor muscle of the middle ear. It represents a fatigue reaction resulting from prolonged irritation and stress of the muscles innervated by the trigeminal nerve (masticators). This form of fatigue reaction apparently only affects the small muscles in this group because of their anatomical relationship.
Chorda ~, tyrnpani
Malleus t Inc~.......~. c"
M. tensor ~
c"
.~I' ........%
~Cc' e Tub.. audir~va
Membrana tympani
FIG. 4 C h o r d a t y m p a n i p a s s i n g b e t w e e n t h e middle ear bones, malleus a n d incus.
Hence, the two tensor muscles are in a vulnerable position in bite anomalies. On rare occasions, objective tinnitus may appear. This sound can also be heard by a second person. The sound arises by means of rhythmic opening and shutting movements of the pharyngeal opening of the eustachian tube, and both tensor muscles will be involved. In the ordinary (subjective) tinnitus, the tensor tympani only is active. It is also a common observation that sufferers from otosclerosis regularly complain of tinnitus in connection to their impairment of hearing. These patients, for whose hearing the bell tolls, may well have an ailment of odontogenic origin. At the annual meeting of The Norwegian Society of Otolaryngology last year, the author compared the histology of otosclerotic bone with that of unilateral fibrous dysplasia of the maxilla in a boy with bite anomalies. It seems that the changes in the bone are similar in both instances and are caused by vibratory trauma to bone tissue. In otosclerosis, this is due to autogenous vibration of the sound-conducting apparatus with tinnitus, and in the particular form of maxillary fibrous dysplasia, it is due to traumatic occlusion on a solitary tooth. The fibrous transformation of bone seems to be caused by those physical irritants. With tension and compression of the sound-conducting structures, the impedance increases, and this entails what is known as functional diminution of hearing. Sometimes, this causes a fullness in the ear of fluctuating character in connection with tinnitus and often alternating with it. Paracusis and hyperesthesia acoustica may occur. There may, also, be autophony, a condition in which one hears one's own voice inside the head as if speaking into an empty barrel. In these
32
B R I T I S H JOURNAL OF ORAL SURGERY
cases, there is a contraction (spasm) in the tensor muscle of the soft palate causing a fullness in the ear and temporary deafness. It is relevant in the explanation of the vestibular type of vertigo, that the violent dizzy attacks generally start with strong and intense tinnitus and are often associated with headache. It is suggested that such attacks can arise from sudden and severe movements of the footplate of the stapes (Fig. 5). A ripple of the waves arise in the lymph of the inner ear which gives rise to these reactions and
tmph us erl$
FIG. 5 T h e organ of hearing and balance. Fluid motion in the l y m p h is indicated, the result of autogenous vibrations of the soundconducting apparatus in the middle ear, T h e cochlear as well as the vestibular structures of the inner ear is found to be influenced by this mechanism.
exerts an intermittent pressure on the walls of the labyrinth. This is similar to waves breaking on the shore. The hollowing out of the labyrinth found in Meniere's disease, called 'hydrops', may well be explained as the result of such pressure effects, as no real increase of pressure in the labyrinth has been measured. One constantly finds that vestibular and cochlear disorders go hand in hand, i.e. vertigo and deafness appear at the same time, as in Meniere's disease. The damage which can be shown to the respective sense cells for hearing and balance has obviously the same origin. In a few cases, the sense cells break down suddenly during an attack, but as a rule, the destruction takes place gradually over a period of years. A prolonged and troublesome tinnitus can be taken as a forerunner of this. By removing the causative factors which can be done by adequate restoration of the bite, the attacks can be checked and the subiective ear symptoms reduced or brought to an end. The issue here is an oto-dental syndrome which demands close co-operation between medical and dental practitioners.