• PHYSIOLOGY
Ossification of the Petrotympanic Fissure:
Morphological Analysis and Clinical Implications
Joào Carlos Castro Monteiro, D.D.S.; Jussara Peixoto Ennes, D.D.S., Ph.D.;
José Roberto Zorzatto, Ph.D.
0886-9634/2904284$05.00/0, THE
JOURNAL OF
CRANIOMANDIBUUVR
PRACTICE,
Copyright ©2011
by CHROMA, Inc.
Manuscript received
May 10, 2010; revised
manuscript received
Juiy 30, 2010; accepted
July 31, 2010
Address for correspondence;
Dr. Joao C.C. Monteiro
SQN215, BiocoG, Apt. 402
Brasiiia DF, Brazil 70.874-070
E-mail; jccmdf@hotmaii.com
ABSTRACT: The petrotympanic fissure, a narrow slit in the temporal bone, aliows the temporomandibuiar joint (TMJ) and the middle ear to communicate. Both the chorda tympani and the ligament
cross the fissure between the posterior region of the joint disk and the maileolar ossicle. The parasympathetic fibers of the chorda tympani spread into the major saiivary giands and are responsible for the
taste sensibiiity on the anterior two-thirds of the tongue. After chronological identification of 30 human
skulls, petrotympanic fissures were macroscopically and stereomicroscopicaliy analyzed for the presence and disposition of ossification areas. Digitaiized images were analyzed using computer program
UTHSCSA ImageTooi 3.0 (developed by the Department of Dental Diagnostic Science at The University
of Texas Health Science Center, San Antonio, Texas). The total extension of the fissures and ossification areas was measured. The macroscopic analysis did not constitute an appropriated method for this
evaluation and the ossification of the fissures increased with aging, suggesting its influence on the
causes of otalgia in cases of TMJ dysfunction.
T
he petrotympanic fissure, located at the mandibular fossa of the temporal bone, is crossed by two
ligaments connecting the temporomandibular joint
(TMJ) to the middle ear, both adhered individually to the
collum mallei. The discomalleolar ligament, firstly
described by Pinto', extends from the retrodiscal region
of the articular capsule to the malleus ossicle and the
anterior ligament of the malleus, which becomes continuous to the sphenomandibular ligament.- These ligaments
were supposed to be related with the otological symptoms because of the involvement of the middle ear determined by the anterior displacement of the disk or by the
excessive mandibular movements, which would determine the excessive traction of the discomalleolar ligament.•'•''
However, this consequent traction of the middle ear
ossicles has been questioned, since it is admitted that the
fissure may have limiting dimensions where the intrafissural arrangement of the soft tissues would not allow the
transmission of forces.'
Cases in which the material injected for arthroscopy of
the TMJ would have determined otological complica-
Dr. Joào Carlos Castro Monteiro
received his D.D.S. degree in 2001 from
the University of Brasilia (UnB). Brazil
and his certificate of conclusion of the
Residency Progratn in Oral Surgery
at the University of Mato Grosso do Sul
(UFMS), Brazil, in 2008. He became a
volunteer professor of oral surgery at
the University of Brasilia in 2009. At
the time of this mcmti.script submission,
he was working to finish the Specialization Program of Implantology at the
University of Sao Leopoldo Mandic,
Brazil. He works as an oral surgeon at
the Regional Hospital of Planattina and
at the College Hospital of the University
of Brasilia.
284
MONTEIRO ET AL.
OSSIFICATION OF THE PETROTYMPANIC FISSURE
tions, like otalgia and tympanum perforation, suggest that
the way of communication between the articulation and
the middle ear would he evident.*"
The calcification process of the sutures of calvarium
occurs in the second decade of life^ from both the endocranial and ectocranial* surfaces. Likewi.se, the calcification process of the petrotympanic fissures could occur in
the same sequence and direction; however, the description of the ossification pattern in this fissure remains
inconclusive.
The clinical implications of the ossification pattern of
the petrotympanic suture can be better understood in light
of morphological descriptive knowledge. The aim of this
study is to morphologically characterize the calcification
in the petrotympanic fissure through three observations:
naked-eye macroscopic observation, stereomicroscopic
observation, and measurements made from digital images.
the length of the calcified regions using the ImageTool
program (University of Texas Science Center in Santo
Antonio, TX) (Figure 1). The petrotympanic fissures
were photographed in full-length under lOx magnification, with liO dpi vertical and horizontal resolutions.
Materials and Methods
Thirty human skulls were studied for the classification
of chronological age, according to the degree of calcification of the latero-anterior sutures, through the ectocranial
surface, as described by Meindl; Lovejoy.'* Sutures on the
right side were observed, (Table 1).
Left and right petrotympanic fissures were analyzed
macroscopically, stereo-microscopically, and also in digital images captured in a Leica MZ 125 stereomicroscope
with a Leica DC 300F system of image capture (Leica
Microsystems, Heerbrugg, Switzerland). Millimeter patterns were used to create proportionality in the measurements of the total length of petrotympanic fissures and
Table 1
Sum of Calcified Suture Marks for Each
Skull Studied to DeterrTiine the Presumed
Chronological Age at Death*
Sum of calcified
suture marks
0 (no calcification)
Presumed
chronological age
under 32
1
2
3 ,4, 5,
32
36
41
6
7,8
43
45
9, 10
51
11, 12, 13, 14
56
15 (total calcification)
over 56
"Adapted from Meindl & Lovejoy (1985)
OCTOBER 2011, VOL, 29, NO, 4
Figure I
Digitalized itnage of the right tnandihular fossa of skull no, 28. with
identification tag and pattein in mm.
By macroscopic evaluation, the areas of possible calcification were identified and recorded. Stereomicroscopically, using a I Ox magnification, the petrotympanic
fissures were observed along their full length in the
latero-medial direction. The calcification regions were
identified and recorded in a drawing, based on their
anatomy (Figure 2). The open-to-discussion regions
were assessed with 15, 20, and 30x magnifications,
respectively. In some cases, these regions have still been
analyzed with gradable variations of light intensity
caused by the adjustment of the stereomicro.scope so that
deeper regions in the fissure could clearly be identified.
The values of the total length of the fissures and each
calcified region yielded, in percentage, the calcification
index for each fissure.
In order to investigate whether there were differences
between the fissure length and the percentage of calcification according to age, the skulls were separated into
two groups. Group I was comprised of 18 individuals
aged 41 years old or younger and Group II, 12 individuals who were older than 41. The age of 41 years was
chosen based upon the number of individuals needed
in each group to give an adequate statistical analysis of
the results.
The statistical analysis of the results, in order to check
for differences in the parameters of both groups evaluated, considered the level of significance a=0.05%, i.e.,
the difference between the medians of the two groups was
THE JOURNAL OF CRANIOMANDIBULAR PRACTICE
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OSSIFICATION OF THE PETROTYMPANIC FISSURE
MONTEIRO ET AL.
Figure 2
Schematic drawings of individual records of skulls nos. 88 (left) and 93 (right), representing the petrotympanic fissures observed and evaluated
using a stereoniicroscope. Note the observations made in regard to the anatomical length of the fissures and the presence or absence of calcified
considered statistically significant when p (probability of
signiflcance) of the test was lower than the level of significance of 5%.
Results
The macroscopic analysis of the petrotympanic fissures revealed suggestive calcification areas in 27 fissures (45%). From the total of fissures that supposedly
presented a calcification area, 13 were relative to the right
side and 14 to the left side of the skulls.
The stereomicroscopic analysis of the fissures showed
calcification areas or bridges that were superficial and, in
some cases, deep in 40 petrotympanic fissures, i.e., in
66.6% of the total (Figures 3-7). Among these, 18 were
relative to the right side of the skulls and 22 to the left. In
most cases, the deep calcification areas (Figure 7) could
only be observed under stereomicroscope when light
intensity was increased. (Figures 4 and 5).
The localization of the calcification areas was not regular when considering the total length of the diverse flssures and its division into medial and lateral regions,
randomly occurring along the total length of the petrotympanic fissures.
A Wilcoxon test for two-related samples, with p=0.229,
showed no statistically significant difference for fissure
length in relation to the sides. Likewise, p=0.225 showed
that the difference in calcification percentages was not
statistically significant for either the right or left sides
(Table 2).
The Mann-Whitney test, for independent samples,
with p=0.4588 for the right side and p^O.2899 for the
left, showed that there were no statistically significant
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Figure 3
Right petrotympanic fissure of skull no. 88. Pattern photograph for
measuring total length of ftssure in mm. Note the calcified (white
arrows) and the noncalcifted (black arrows).
differences in median lengths of the fissures between
Group I and Group II for either the right or left sides
(Table 3).
The Mann-Whitney test, for independent samples,
with p=0.0262, showed that, for the right side of the skull,
there is statistically significant difference in the median
percentages of fissure calcifications of Groups 1 and II,
of different chronological ages; the same observation
holds for the left side, with p=0.()277 (Table 4).
Discussion
The analysis of the 3-dimensional aspects of the
anatomical structures demands a suitable device.'" The
OCTOBER 2011, V O L 29, NO. 4
MONTEIRO ET AL.
OSSIFICATION OF THE PETROTYMPANIC FISSURE
ir
Figure 4
Right fissure of skull no. 88 with increased luminous intensity. Note
the contrast of the calcified (white arrows) and noncalcified (black
arrows).
tr
Figure 6
Left petrotympanic fissure of skull no. 88. Pattern photograph for
measuring total length of the fissure in mm. Note the superficial
calcification areas (white arrows).
ÏÏ
ÏÏ
Figure 5
Right fissure of skull no. 88 with the same increase in luminous intensity, but from another angle to confirm the central calcification area
(white arrows).
Figure 7
Left fissure of skull no. 88 with increased luminous intensity Note the
contrast of the superficial (white arrows) and the deep (black arrows)
calcified areas.
analysis of the petrotympanic fissures with a stereomicroscope allowed for the identification of a larger number of
calcification areas in the fissures, which could not be
identified with the naked eye (Figures 3-7). The macroscopic analysis of the fissures is more reliable in the cases
in which a fissure is totally open and when it is totally or
practically calcified, which was not seen.
Ennes and Consolaro'" observed the direction of the
calcification of the middle palatine suture, which was
postero-anterior, and related it with the anatomical disposition of the horizontal plane of the palate. The latter,
with no condition to transmit forces to the head bone
complex, would respond to the convergence of forces
with the apposition of the bone, in a way similar to other
bone braces, such as the glabella or the menton protuberance; however, the same was not seen in relation to the
calcification of the petrotympanic fissure. The calcification areas or bridges were randomly scattered along the
length of these fissures. Some factors could contribute to
the absence of standardization, such as: longer distances
between the bone surfaces delimiting the petrotympanic
fissures; more complexity of tissues making up the
anatomical structures crossing it; the physiology of these
tissues; and the balance resulting from force distribution.
The fissures presented similar length and standard
ossification on both sides. The latter could be explained
by the physiological patterns of the TMJ. Since they are
synergic articulations, both sides move simultaneously,'
OCTOBER 2011, VOL. 29, NO. 4
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Table 2
Results of the Statistical Descriptive Analysis in Relation to the Fissure Length (in mm),
and the Percentage of Calcification, According to Laterally
Descriptive
Fissure lenqth (mm)
Percentaae calcification
Right
Left
Right
Left
statistics
Mean
14.01
13.49
24.41
28.74
Median
24.70
31.08
14.18
13.25
2.34
1.92
24.78
25.26
Std. Dev.
Minimum
8.90
0
0
9.53
16.19
82.70
77.80
Maximum
17.93
30
Count
30
30
30
p value
0.229
0.225
Table 3
Results of the Statistical Descriptive Analysis in Relation to the Fissure Length (in mm),
and the Percentage of Calcification, According to Age
Descriptive
Fissure lenqth (mm) - riqht side
Fissure lenath (mm) - left side
statistics
<41 years
>41 years
<41 years
>41 years
Mean
14.30
13.59
13.82
13.01
Median
14.21
13.54
14.34
12.98
2.07
1.77
2.12
Std. Dev.
2.73
Minimum
9.53
9.81
10.14
8.90
Maximum
17.93
17.90
16.19
16.06
Count
18
12
18
12
p value
0.4588
0.2899
Table 4
Results of the Statistical Descriptive Analysis of the Percentage of
Fissure Calcification, According to Age
Descriptive
Calcification % on riaht side
Calcification % on left side
statistics
>41 years
<41 years
>41 years
<41 years
Mean
15.88
37.21
20.09
41.72
Median
0
40.18
18.78
43.34
Std. Dev.
22.94
22.54
20.19
27.31
Minimum
0
0
0
0
Maximum
66.68
82.70
61.93
77.80
12
18
12
Count
18
p value
288
0.0262
THE JOURNAL OF CRANIOMANDIBULAR PRACTICE
0.0277
OCTOBER 2011, VOL. 29, NO. 4
MONTEIRO ET AL.
OSSIFICATION OF THE PETROTYMPANIC FISSURE
stimulating the osteogenic membranes symmetrically.
The increase of calcification percentages in the
petrotympanic fissures was observed to be associated
with an increase in chronological age. This is illustrated
graphically through the increase of both the average and
the median for calcification percentages (Figure 8). The
calcification process of anatomical accidents due to aging
was previously observed in other studies.'''-
the possible movement of ear ossicles would depend on
the degree of closure of the petrotympanic fissure during
the development and on the points of adhesion of the ligament in the fissure borders. In cases of "big and broad"
fissures and/or "ligaments badly adhered to the walls of
these fissures," the parafunctional mandibular pathways
seen in some sufferers of TMD could result in the traction
and movement of the malleus, resulting in otological
PERCENTAGES OF CALCIFICATION
37.21
41.72
40.18
43.34
• Average
• Median
15.88
0.00
G1D
G2D
G1E
G2E
Figure 8
Average and median of the percentages of fissure calcification for Group 1 on the right (GID) and left side (G2D) and for Group 2 on the right
(GlE) and left side (G2E)
The ossification of the fissure may indicate the discontinuity of the ligaments of the TMJ structure and the tympanic cavity. This observation may be associated with the
hypotheses'-*'"• used to try to explain the clinical implications of conditions such as otalgia in cases of temporomandibular disorders (TMD).""'
Kim, et al.." reported that the movement of the malleus
was observed during the traction of its anterior ligament.
This observation could strengthen the hypothesis that
associates traction of the malleus by the discomalleolar
ligament with the origin of otalgia in TMD. since both
ligaments would be adhered to each other."*
Authors like Komori, et al.,- Eckerdal,'^ Coleman,'''and
Ögütcen-Toller,-" however, claim that there is no evidence that the traction of the discomalleolar ligament
could cause the movement in the ossicle chain of the
middle ear in adults. Rodríguez-Vásquez, et al.,'* suggests that the traction of the discomalleolar ligament and
OCTOBER 2011, VOL. 29, NO. 4
symptomatology. Theoretically, this non-physiological
movement of the malleus could inflict any traumatic
injury to the tympanic membrane or to the chain of auditory ossicles, since all these structures are closely related.-' The patients could relate earache because the
tympanic membrane and the mucous membrane, which
constitute the structures of the middle ear, are extensively
innervated.-' This could be a possible reason why not all
TMD sufferers present with otalgia.'*
With the calcification of the petrotympanic fissure in
the later phases of life, the communication between the
middle ear and the temporomandibular articulation would
not exist. TMD sufferers with otologic symptomatology
should report an alleviation of these symptoms with age,
since because the fissure is calcified, there would not be
any other way for the tensional forces towards the middle
ear ossicles to propagate. It is worth noting that the average age of the sufferers corresponds to the age of adults.
THE JOURNAL OF CRANIOMANDIBULAR PRACTICE
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OSSIFICATION OF THE PETROTYMPANIC FISSURE
but not in elderly subjects, according to some studies."""
In cases where it is not seen, other theories should explain
the origin of these symptoms.'^•'•*
MONTEIRO ET AL.
10,
11,
12,
Conclusions
The macroscopic or naked-eye analysis of the calcification of petrotympanic sutures was unreliable.
The stereomicroscope showed the following: an
increase in calcification areas or bridges in the petrotympanic fissures related with chronological aging; the inexistence of a relationship between calcification and
anatomical position in both sides of the skull; and the
nonexistence of alteration in petrotympanic fissure length
related to aging.
These observations allowed the inference that the continuous calcification process of the petrotympanic fissures could be associated with the presence/absence of
otalgia in TMD sufferers. Further studies, however,
would be necessary, especially longitudinal clinical studies involving elderly patients to investigate the symptomatology. From the data collected, the diverse theories
and/or hypotheses could be related or discarded so as to
enable the development of better treatment options for
these patients.
References
Pinto OF: A new structure related to the temporomandibular joint and middle
eux. J Prosthet Den 1962; l2(n:95-103,
Komori E. Sugisaki M. Tanabe H, Katoh S: Discomalleolar ligament in the
adult human, J Craniomandih Pracl 1986; 4(4):3CIO-3O5,
Ioannides CA. Hoogland GA; The discomalleolar ligament; a possible cause
of subjective hearing loss in patients with temporomandibular joint dysfunction, V Aífl.ri//o/aí-Swr^ 1983; 11;227-23I.
Cheynet F. Guyot L. Richard O. Layoun W. Gola R; Discomalleolar and
malleomandibular ligaments; anatomical study and clinical applications,
5urg Rflí/ioMnaí 2003; 25; 152-157,
Eckerdal O; The petrotympanic tissure; a link connecting the tympanic cavity
and Ihe temporomandibular joint, J Craniomandih Pract 1991; 9( I ): 15-22,
Schickinger B. Gstoettner W. Cemy C. Komfehl J; Variant petrotympanic
fissure as possible cause of an otologic complication during TMJ
anhroscopy, J Oral Mavillofac Surg 1998; 27; 17-19,
DuBrul EL; Sicher and DuBrul's oral anatomy. St Louis & Tokyo; Lshiyaku
Euroamerica Inc. 1988,
Todd TW. Lyon Jr DW; Endix-ranial suture closure. Part I, Adult males of
white stock. Am J Pins Anihropol 1924; 7;325-384,
Meindl RS. Lovejoy CO; Ectocranial suture closure; a revised method for the
determination of skeletal age at death based on the lateral-anterior sutures.
Am J Phys Anthropol 1985; 68;57-66,
290
THE JOURNAL OF CRANIOMANDIBULAR PRACTICE
13,
14,
15,
16,
17,
18,
19,
20,
21,
Ennes J. Consolaro A; Sutura palatina mediana; avaliaçâo do grau de ossificaçào em crânios humanos, R Dental Press Onodon Orlop Facial 2004;
9(5);64-73,
Ashley-Montagu MF; Aging of the skull. Am J Phys Anihropol 1938; 3;35575,
Manzanares MC. Goret-Nicaise M. Dhem A; Metopie suture closure in the
human skull, 7/Imi; 1988; I6I;2O3-2I5,
Ash CM. Pinto OF; The TMJ and the middle ear; structural and functional
correlates for aural symptoms associated with temporomandibular joint
dysfunction, hit J Prosthodoni 1991;4(l);5l-57,
Manni A. Brunori P. Giuliani M. Modoni M. Bizzi G; Oto-vestibular symptoms in patients with temporomandibular joint dysfunction,
Electromyographic study, Minen'a Sionuitol 1996; 45(l);l-7.
Pascoal MIN. Rapop<5rt A. Chagas JFS. Pascoal MBN. Costa CC. Magna LA;
Prevalência dos sintomas otológicos na desordem temporomandibular;
estudo de 126 ca,sos. Rev Bras Olorrinolaring 2001 ; 67(5);627-633,
Tuz HH. Onder EM. Kisnisci RS; Prevalence of otologic complaints in
patients with temporomandibular disorder. Am J Orthod Denlofac Orlhop
2003; 123(6);620-623,
Kim HJ. Jung HS. Kwak HH. Shim KS. Hu KS. Park HD, Park HW, Chung
IH; The discomalieolar ligament and the anterior ligament of malleus; an
anatomic study in human adults and fetuses. Surg Radiol Anat 2004; 26;3945,
Rodríguez-Vá.squez JF. Merida-Velasco JR. Merida-Vela,sco JA. JiménezCollado J; Anatomical considerations on the discomalleolar ligament,
JAnat 1998; 192;617-621,
Coleman RD; Temporomandibular joint; relation of the retrodiscal zone to
Meckel's cartilage and lateral pterygoid muselé. J Dent Res 1970; 49;626630
OgUtcen-Toller M; The morphogenesis of the human di.scomalleolar and
sphenomandibular ligaments, J Cranioma.xiltofac Surg 1995; 23;42-46,
Clemente CD; Gray's anatomv. Philadelphia; Lea & Febiger. 1985,
Dr. Jussara Peixoto Ennes is an adjunct professor in human anatomy at
the University of Mato Grosso do Sut ( UFMS), Brazil. She received her
D.D.S. degree in 1985 from the School of Dentistry in UFMS. Brazil, a
Master's degree in odontology ft otn the School of Dentistry of the
University of Sao Paulo (USP). Brazil in 1999, atid a Doctorate in oral
pathology from the School of Dentistry of Bauru in USP, Brazil in 2002.
Dr. Ennes's specialties include: etidodontics (University of Sao Paulo —
USP, 1988) and Morpho-physiology (UFMS, 1994). Her teaching
experience iticludes: human attatomy, neuroanatomy, dental anatomy,
and her particular area of interest is in odontogenesis research, including craniofacial anatomy and dental anomalies.
Dr. José Roberto Zorzatto is an associate professor in biostatistics at
the Institute of Cotnputation at the University of Mato Grosso do Sut
(UFMS). Brazil. He graduated in mathematics at the University Julio de
Mesquita Filho, Sao Paulo, in 1978. He received his Master's degree in
statistics from the University of Campinas (Unicatnp), SP, Brazil anda
Ph.D. degree in electrical engineering at Unicatnp. The main focus of his
scientific work is on biostatistics atid experiment platining. He did his
thesis on Probability Models for tropical forests.
OCTOBER 2011, VOL, 29, NO. 4
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