Tuesday, December 28, 2010

Mastoid Surgery

Myringoplasty
It is an operation in which reconstructive procedure is
limited to repair of tympanic membrane perforation.
Tympanoplasty without Mastoidectomy
(tympanum = middle ear)
It is an operation to eradicate disease in the middle ear
and to reconstruct the hearing mechanism without mastoid
surgery, with or without tympanic membrane grafting.
This means ossicular reconstruction only or ossicular
reconstruction with myringoplasty.
Tympanoplasty with Mastoidectomy
It is an operation to eradicate disease in both the mastoid
and middle 'ear cavity, and to reconstruct the hearing
mechanism with or without tympanic membrane grafting.
Cortical Mastoidectomy (Simple
Mastoidectomy or Schwartz Operation)
It is an exenteration of all accessible mastoid air cells preserving
the posterior meatal wall.
Modified Radical Mastoidectomy
It is an operation to eradicate disease of the attic and mastoid,
both of which are exteriorised into the external auditory
canal by removal of the posterior meatal and lateral
attic walls. Tympanic membrane remnant, functioning
ossicles and the reversible mucosa and function of the
eustachian tube are preserved. These structures are necessary
to reconstruct hearing mechanism at the time of surgery
or in a 2nd stage operation.
Radical Mastoidectomy
It is an operation to eradicate disease of the middle ear
and mastoid in which mastoid, midd le ear, attic and the
antrum are exteriorised into the external ear by removal
of posterior meatal wall. All remnants of tympanic membrane,
malleus, incus (not the stapes) chorda tympani and
the mucoperiosteal lining are removed, and the opening
of eustachian tube closed by packing a piece of muscle or
cartilage into the eustachian tube.
Meatoplasty
Meatoplasty is an operation in which a crescent of concha 1
cartilage is excised to widen the meatus. It is invariably
combined with all canal wall down procedures, i.e. modified
radical for periodic cleaning or inspection, and radical
mastoidectomies for easy access to the mastoid cavity, or it
is done as an isolated procedure in a sagging auricle seen in
older people. Sagging auricle obstructs the ear canal and
causes hearing loss and retention of wax.
Mastoid Obliteration
It is an operation to eradicate mastoid disease, when
present, and to obliterate the mastoid cavity.
Obliteration of mastoid cavity is done with pedicled temporalis
muscle or musculofascial tissue raised as flaps.
SURGICAL APPROACHES TO THE
EAR AND INCISIONS
1. Endomeatal or transcanal approach. It is used to
raise a tympanomeatal flap in order to expose the middle
ear. Rosen's incision is the most commonly used for
stapedectomy. It requires the meatus and canal to be wide
enough to work. It consists of two parts; (a) a small vertical
incision at 12 o'clock position near the annulus and (b) a
curvilinear incision starting at 6 o'clock position to meet
the 1st incision in the posterosuperior region of the canals,
5-7 mm away from the annulus (Fig. 76.1) Posterior
meatal canal skin is raised in continuity with tympanic
membrane, after dislocating the annulus from the sulcus. It
gives a good view of the middle ear and ossicles. Stapes, if
still covered by posterosuperior overhang of bony meatus,
can be exposed by removing this part of the overhang. This
incision is also used commonly for exploratory tympanotomy
to find cause for conductive hearing loss, inlay
myringoplasty or ossicular reconstruction.2. Endaural approach. It is used for:
(a) Excision of osteomas or exostosis of ear canal.
(b) Large tympanic membrane perforations.
(c) Attic cholesteatomas with limited extension into
the antrum.
(d) Modified radical mastoidectomy where disease is
limited to attic, antrum, and part of mastoid.
Endaural approach is made through Lempert's incision
(Fig. 76.2). It consists of 2 parts:
Lempert I-It is semicircular incision, made from 12
o'clock to 6 o'clock position in the posterior meatal wall
at the bony-cartilaginous junction.Lempert II-Starts from the 1st incision at 12 o'clock
and then passes upwards in a curvilinear fashion between
tragus and the crus of helix. It passes through the incisura
terminalis and thus does not cut the cartilage. Both mastoid
and external canal surgery can be done.
3. Postaural (or Wilde's) incision (Fig. 76.3). It starts
at the highest attachment of the pinna, follows the curve
of retroauricular groove, lying 1 cm behind it, and ends at
the mastoid tip. In infants and children up to 2 years of age,
the mastoid process is not developed and the facial nerve
lies exposed near its exit, and the incision therefore is slanting
posteriorly, avoiding lower part of the mastoid. Some
surgeons prefer to make the postaural incision in the sulcus
(retroauricular groove) . Postaural incision is used for:
(i) Cortical mastoidectomy.
(ii) Modified radical and radical mastoidectomy.
(iii) Tympanoplasty: when perforation extends anterior
to handle of malleus.
(iv) Exposure of CN VII in vertical segment.
(v) Surgery of endolymphatic sac.
CORTICAL MASTOIDECTOMY
Cortical mastoidectomy, known as simple or complete
mastoidectomy or Schwartz operation, is complete exenteration
of all accessible mastoid air cells and converting
them into a single cavity. Posterior meatal wall is left
intact. Middle ear structures are not disturbed.
Indications
1. Acute coalescent mastoiditis.
2. Incompletely resolved acute otitis media with reservoir
sign.
3. Masked mastoiditis.
4. As an initial step to perform:
(a) endolymphatic sac surgery
(b) decompression of facial nerve
(c) translabyrinthine or retro-Iabyrinthine procedures
for acoustic neuroma.
Figure 76.4 shows the various structures and landmarks
seen after cortical mastoidectomy.
Anaesthesia
General anaesthesia.
Position
Patient lies supine with face turned to one side and the
ear to be operated upper-most.
Steps of Operation
1. Incision. A curved postaural incision about 1 em
behind but parallel to the retroauricular sulcus, starting
at the highest attachment of pinna to the mastoid tip
(Fig. 76.3B).In infants and children up to 2 years, the incision is
short and more horizontal. This is to avoid cutting facial
nerve which is superficial in the lower part of mastoid
(Fig. 76.3C).
Incision cuts through soft tissues up to the periosteum.
Temporalis muscle is not cut in the incision.
2. Exposure of lateral surface of mastoid and
MacEwen's triangle. Periosteum is incised in the line of
first incision. A horizontal incision may be made along
the lower border of temporalis muscle for more exposure.
Periosteum is scraped from the surface of mastoid and
posterosuperior margin of osseous meatus. Tendinous
fibres of sternomastoid are sharply cut and scraped down.
A self-retaining mastoid retractor is applied.
3. Removal. of mastoid cortex and exposure of
antrum. Mastoid cortex is removed with burr, or gouge
and hammer. Mastoid antrum is exposed in the area of
suprameatal triangle (MacEwen's triangle). In an adult,
antrum lies 12-15 mm from the surface. Horizontal semicircular
canal is identified.
4. Removal of mastoid air cells. All accessible mastoid
air cells are removed leaving behind the bony plate
of tegmen tympani above, sinus plate behind and posterior
meatal wall in front.
5. Removal of mastoid tip and finishing the cavity.
Lateral wall of the mastoid tip is removed, exposing muscle
fibres of posterior belly of digastric. Zygomatic cells situated
in the root of zygoma, retrosinus cells lying between
sinus plate and cortex, behind the sinus, are removed. A
finished cavity should have bevelled edges so that soft
tissue can easily sit in and obliterate the cavity.
6. Closure of wound. MastoiJ cavity is thoroughly
irrigated with saline to remove bone dust, and the wound
is closed in two layers. A rubber drain may be left at the
lower end of incision for 24-48 hours in case of infection
or excessive bleeding. A meatal pack should be kept to
avoid stenosis of ear canal. Mastoid dressing is applied .
Post-operative Care
1. Antibiotics started pre-operatively are continued
post-operatively for at least one week. Culture swab
taken from the mastoid, during operation, may dictate
a change in the antibiotic.
2. Drain, if put, is removed in 24-48 hours and sterile
dressing done.
3. Stitches are removed on the 6th day.
Complications
1. Injury to facial nerve .
2. Dislocation of incus.
3. Injury to horizontal semicircular canal. Patient will
have post-operative giddiness and nystagmus.
4. Injury to sigmoid sinus with profuse bleeding.
5. Injury to dura of middle cranial fossa.
6. Post-operative wound infection and wound
break-down.

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