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Introduction
Surgical training as well as teaching methods has shown a
technologically driven evolution.
1
Simulation and Synthetic replicas
of temporal bones made of acrylic resins are used for trainee ENT
Surgeons.
2,3
But the traditional dissection on temporal bones remains
simple, feasible, and convenient teaching tool despite technical
advancements. We as an Anatomist promote and encourage the
training of our future surgeons by the use of cadaveric temporal
bone dissection via different approaches. Learning by hands on
training is considered ideal.
1
The temporal bone has a very complex
configuration, containing vital structures known for their anatomical
variations. Different types of pneumatisation of mastoid air cells,
Korner’s septum, facial nerve and ossicular anomalies, low lying
dura and anteriorly placed sigmoid sinus and various other anomalies
yet unnoticed. Dissection on cadaveric bones will suffice to study
of anomalies as well as normal anatomy of this region. Cawthorne
has stated that facial nerve surgery needs experience and should be
performed only after practice on human cadaveric temporal bones.
4
Different approaches to middle ear
Middle ear cavity is a mucous lined air filled irregular space within
the petrous part of temporal bone compared to a cube, containing ear
ossicles and associated muscles. We can reach it via lateral approach
or via dorsal and dorsomedial approaches.
5
Kamal Singh et al.
6
described an innovative procedure-Kobbler’s
cut .By this method one can quickly expose the middle ear cavity
and procure the ear ossicles (Malleus, Incus & Stapes).Moreover,
the view of the internal structures and anatomical features of the
middle ear cavity are more apparent. The ossicles so received can
be used for potential further study for forensic aspects
7
as well as
ENT prospective. This method proves to be the easiest, less time
consuming and least destructive method of dissection as compared
to the traditional methods of piece meal removal of bone, chipping
away the roof (tegmen tympani) or snipping off done for exploring the
middle ear cavity and mastoid air cells.
8
Lisowski FP
9
describes that for the study of the auditory and
vestibular apparatus, the temporal bone and the adjacent parts of
the sphenoid and occipital bones has to be removed and decalcified
in 10% concentrated solution of nitric acid, after following the full
procedure of decalcification bone becomes soft and easy to dissect.
After examining the prosected part bone is gently removed between
the hiatus for the greater petrosal nerve and the geniculate ganglion;
this exposes the course of the nerve and also the coils of the cochlea,
followed by removal of tegmen tympani exposing the small auditory
ossicles. This procedure seems best for specimen preparation as well
as for detailed study of both internal as well as middle ear, but it is
more time taking and will require a patient trainee.
Cunninghams’s manual
10
described tegmen tympani approach,
with a point of rigid knife or seeker a small aperture is made then
it is lifted up with seeker and breaking of tegmen tympani is done
first in anteromedial direction then in the posterolateral direction
towards the junction of transverse and sigmoid sinus. This approach
is conventional and little less precise as the bone may not fracture in
a desired direction cut edges may create confusion with ear ossicle as
they are also situated within the bone.
Repetitive laboratory dissection of human temporal bone
specimens creates an eye–hand familiarity that is essential for safe
operating in the live patient. For post graduate training on temporal
bone surgeries there should be well equipped laboratories in various
colleges that use, high-speed otologic drill (pneumatic or electric),
along with Irrigating suctions, Hosing for both suction and irrigation,
No. 15 blade scalpel, Heavy periosteal elevator, Round knife, Annulus
elevator, Curved needle, microscissor’s all these instruments suffice
in practicing for surgeries related to ear specially for those who opt
for specialisation in ENT.
Grant’s dissector describes approach to middle ear via tegmen
tympani.
11
Now a days, the surgical procedures of the middle ear are
traditionally carried out with the help of microscopes, with few
limitations (Less visualisation of deep and lateral recess).
12
MOJ Anat Physiol. 2016;2(5):128‒129. 128
© 2016 Pandey et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which
permits unrestricted use, distribution, and build upon your work non-commercially.
Dissecting cadaveric middle ear: approaches
Volume 2 Issue 5 - 2016
Krishna Pandey, Nishtha Singh, Badal Singh
Department of Anatomy, MLN Medical College, India
Correspondence: Krishna Pandey, Department of Anatomy,
MLN Medical College, Allahabad, India,
Email kp260683@gmail.com
Received: May 14, 2016 | Published: May 26, 2016
Abstract
Introduction: The temporal bone is a valuable resource for the study of diseases of middle
ear and teaching anatomy to both undergraduate as well as post graduates. It is one of the
most complicated bones of skull and lodges in it the special sense organ for hearing and
balancing and associated nerves.
Objectives: Various books and dissection manuals described different approaches to middle
ear along with intrapetrous course of facial nerve. We have discussed different approaches
to middle ear, their benefits and drawbacks
Data synthesis: Different approaches to middle ear cavity have been described by different
dissection manuals and various authors. Every method or approaches have their own merits
and demerits.
Conclusion: Dissection on decalcified temporal bone and tegmen tympani approach seems
to be the best tool for studying middle ear, course of facial nerve inside the temporal bone
as well as preparing specimen.
Keywords: temporal bone, dissection middle ear, tegmen tympani
MOJ Anatomy & Physiology
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