The malleus, the heart of the tympanic-ossicular chain
Carla Branco, MD1,2, Helena Ribeiro, MD2, João Paço, MD, PhD1
1Hospital Cuf Infante Santo, 2Centro Hospitalar Lisboa Norte - Hospital Pulido Valente, Lisbon, Portugal
ABSTRACT
OBJECTIVE
RESULTS AND DISCUSSION
RESULTS AND DISCUSSION
The malleus, the heart of the tympanicossicular chain
Objective: Document the anatomical
relationships of the malleus and their clinicalsurgical implications.
Study Design: Point-prevalence study of postmortem material.
Material and Methods: 110 temporal bones
from adults without history of otologic
pathology were studied. The anatomic details
of the malleus and its relationship with the
tympanic membrane and its ligaments were
observed; histology was documented on 30
sectioned bones.
Results: The malleus is an ossicle with an
important relationship with the tympanic
membrane, although the tympanic fibres only
actually cover the lower half of the manubrium
of the malleus. In 86% of cases the upper half
of the manubrium is attached to the tympanic
membrane by a mucosal fold, the plica
mallearis ou malleolus fold. In many cases, at
where the tympanic membrane is adjacent to
the lateral process, exists embryonic
cartilaginous debris that constitutes, just as the
plica mallearis, excellent surgical dissection
planes. The malleus consists of an important
ligamentous apparatus, being the true heart of
the tympanic cavity and the epicentre of the
movements that physiologically sustains
hearing, having been detected the existence of
3 major ligaments, contrary to the 4 or 5
previously mentioned by other authors.
Discussion and Conclusion: The anatomical
systemization of the malleus and its ligaments
allows delimitation of the spaces/pockets in the
interior of the tympanic membrane, thus being
a fundamental aspect towards the
comprehension of the phenomenon of hearing,
of the clinical and radiologic evolution of much
pathology, and finally, the surgical approach of
cholesteatoma.
Document the anatomical relationships of the malleus and their clinicalsurgical implications.
In other cases the manubrium is in contact with the fibrous layer of the
tympanic membrane. Surgically the presence of this fold is also home to
a surgical point of cleavage, allowing the introduction and fixation of a
graft during a tympanoplasty (Fig. 2).
The umbo, flat from the outside in, is where the narrowest contact is
established between the malleus and the fibrous layer of the tympanic
membrane. As the fibers of the lamina propria reach the edge of the
umbo they divide to completely involve it, covering its external and
internal surfaces, which prevents surgical dissection and making it a
point of great physiological importance in the tympanic membrane
mobility (Fig. 3).
Contact between the malleus and the walls of the tympanic cavity are
established by ligaments, muscular tendons and folds. These, having
the malleus as a fixating site, dictate the formation of different
compartments essential for understanding the evolution of
cholesteatoma disease but also of any image analysis of the tympanic
cavity.
The anterior ligament has a cylindrical shape and provides the union
between the malleus neck and the petro-tympanic fissure, located in the
anterosuperior angle of the tympanic frame. Between this ligament and
the tympanic membrane the anterior tympanic spine interposes that
provides osseous support to the ligament throughout its course. This
disposition allows that these structures, together, constitute the main
supporters of the malleus, being considered the axis of rotation of this
ossicle.
The superior ligament of the malleus or the suspensory ligament is the
smallest and most fragile of the three ligaments, establishing a
connection between the tegmen tympani, on the petro-squamous suture,
and the head of the malleus. It contributes along with the malleus head in
dividing the outer epitympanum and the inner epitympanum.
CONTACT
Carla Branco
H. Cuf Infante Santo, H. Pulido Valente
Email: csbranco@gmail.com
Phone: +351965891121
Poster Design & Printing by Genigraphics® - 800.790.4001
METHODS AND MATERIALS
The study included 110 temporal bones (55 right and 55 left) chosen
from 55 crania of adults from both sexes, from sequential necropsies:
well preserved, one temporal bone per cranium. Those chosen had no
known history of otological pathology.
In every temporal bone macroscopic cuts were done using an electric
saw of fine cut (Black & Decker, DN330). Two vertical cuts were made
parallel to the tympanic membrane (one that passed through the
external auditory canal, at the isthmus level, and the second on the
internal cavity wall). With these cuts a total exposure of the tympanic
membrane is possible, leaving the bone frame that involves it whole.
The parts were then observed using a surgical microscope (Wild-M650
with a 200mm lens) with increasing amplifications of 16, 25 and 40,
finalizing the study with micro dissection (which permitted analyzing the
the relationships established between the malleus, the tympanic
membrane and the walls of the tympanic cavities.
RESULTS AND DISCUSSION
The intimate and distinct involvement between the lower half of the
malleus and the tympanic membrane allowed organization of the area
of contact of the two structures into three different areas: the lateral
process, the manubrium, and the umbo.
The lateral process is the upper most point of contact between the
malleus and the tympanic membrane at its end, being evident at
otoscopy the procidentia it causes. It was found that in none of the
temporal bones observed tympanic fibers involved the lateral process.
In fact they come into contact with the cartilaginous tissue at the end of
the lateral process whose presence was constant. This may give some
mobility of the tympanic membrane on the malleus and to create a
surgical point of cleavage, facilitating the detachment of the tympanic
membrane and preventing its collapse (Fig. 1).
The external border of the malleus manubrium has an outwards
concave curvature, which causes the tympanic membrane to contact
only a part of the border’s extension. It was found that, at the upper half
of the manubrium , the connection between the tympanic membrane
and the malleus is made by a delicate mucosal fold called plica
mallearis, identified in 86% of cases, crescent shaped, and not
exceeding 0.5 mm wide.
The presence of three ligaments were noted: the external lateral,
anterior and superior.
The external lateral ligament, composed of fibrous tissue, lays out like a
fan between the neck of the malleus and the Rivinus notch. The
proximity between this ligament and the pars flaccida, which terminates
next to the outer side of the notch, is particularly important because, if
there is erosion of the wall, the two structures are simultaneously
detached. This ligament divides the external hall of the epitympanum,
on top, from the Prussak pocket or superior tympanic pocket, creating
an anatomical barrier to cholesteatoma evolution (Fig. 4).
There are some authors that report other ligaments, namely a malleus
posterior ligament which corresponds to posterior fibers of the external
lateral ligament, having no need for such a division as this ligament
functions as a unit (Fig. 5).
The malleus muscle tendon originates at the inner wall of the middle ear,
close to the cochleariformis processus and heads to the superior
extremity of the malleus manubrium , where it instills on the inner border
and anterior side, contributing to the separation of the epitympanum from
the antrum (Fig. 6).
The malleolus folds, posterior and anterior, are mucosal folds that exist
given that the manubrium, two tympanic spines (anterior and posterior)
and tympanic lamina meet at a more internal level than the tympanum.
RESULTS AND DISCUSSION
The posterior malleolus fold, identified in 96% of cases, instills behind
the tympanic lamina and posterior tympanic spine to then go forward
towards the malleus, fixating on the upper third portion of the inner
border of the manubrium. Above the malleolus fold is presented in two
distinct ways: in 65% of the cases it is united in all its extension to the
posterior border of the external lateral ligament of the malleus; in the
remaining cases the malleolus fold instills on the posterior side of the
tympanum, at the transition of the pars tensa to the pars flaccida. On
the outer side it topographically correspondes to the posterosuperior
quadrant portion, above the chorda tympani.
The anterior malleolus fold, present in all cases, is between the anterior
tympanic spine and the extremity of the inner border of the manubrium.
Interiorly and along its entire course the anterior ligament of the malleus
and the anterior tympanic spine was always found. Adjacent to this fold,
it was also observed in all cases the presence of the chorda tympani
nerve. On the outer side it topographically correspondes to the
anterosuperior quadrant (Fig. 7).
The malleolus folds and the external lateral ligament contribute to the
formation of tympanic pockets on the inner side of the tympanum,
designated as posterior, anterior and superior (or Prussak) tympanic
pockets (Fig. 8).
The first two are located at the mesotympanum and the last at the
epitympanum, making it therefore more fragile and being at the origin of
a significant number of retraction pockets, which ultimately lead to its
collapse. In 65% of the cases a posterior pocket comunicates with the
superior and only 20% of the cases anterior pocket comunicates with
the superior, given the absence of a meso in its apex. It is in this
intratympanic "labyrinth“ that cholesteatoma develops and grows,
always progressing according to the presence of facilitating factors..
CONCLUSIONS
Fig. 1 Histological cut (HE,400X) at
lateral process level (Ct. Ap). Malleus
(M) separated from tympanic fibers (MT)
by cartilaginous cells that constitutes a
surgical cleavage point.
Fig. 2 Histological cut (HE,400X)
showing relation malleus (M) has with
tympanic membrane (MT) at
manubrium. Plicca mallearis (pm) also
an excellent surgical cleavage point.
Fig. 4 Superior tympanic pocket pointed
out between pars flaccida (PF), external
lateral ligament (LLE) and neck of the
Fig. 3 Histological cut(HE,400X), lamina malleus (M). B-Incus; PT-Pars tensa; TEpropria fibers involving umbo (M), most Left temporal.
fixated point between malleus and MT.
Fig. 5 Malleus superior ligament
(LS). CAE-External auditory canal;
LLE-External lateral ligament; MMalleus;Pr-Promontory.
The malleus arises in the anatomy of the tympanic cavity as a point of
important support in the physiology and pathophysiology of the middle
ear. A number of structures exist, which are directly related, that are
fundamental in the progression and understanding of the cholesteatoma
as like in the interpretation of imaging exames and the surgical
approach to the middle ear.
REFERENCES
1. Amiri C., 1977, “Hypothesis Based in Anatomical Aberration and Certain
Conditions Responsible for Cholesteatoma Formation”. In Cholesteatoma,
First International Conference.
Fig. 6 Vertical cut of right temporal,verifying that malleus
(M) is not part of tympanic membrane thickening. Ca-lateral
process; IR-Rivinus notch; PT-Pars tensa; PF-Pars
flaccida; F-Facial; pc-Processus cochleariformis.
Fig. 7 Walls of posterior tympanic pocket(BTP). nct-chorda tympani nerve;
A)-Inner view of MT showing posterior pocket and coronal cut (C)
corresponding to images B and C; B)-BTP is separated from the superior
(BTS) since posterior malleolus fold (PMP) attaches directly on MT; C)-BTP
and BTS unite as PMP joins LLE.
Fig. 8 Affiliation of BTS with cavity levels and anterior and posterior
pockets. tmm-Malleus muscle tendon; A) Coronal cut. BTS is found in
the epitympanum; B) Inner view of MT. Connecting points at this level
are shown between tympanic pockets, BTA, BTP and BTS.
2. Arnold W. J., Laissue J. A., Friedmann I., Naumann H. H., 1987, “Diseases
of the Head and Neck, an Atlas of Histopathology”, Georg Thieme Verlag,
Thieme Medical Publishers, Inc. New York.
3. Testut L., Latarjet A., 1949, “Traité d’Anatomie Humaine”. G. Doin edt.,
Paris, 9th Edition.