 Anaesthesia
Surgery is performed under local anaesthesia with sedation (Xylocaïn
or Lidocaïn 1% and Adrenalin or Epinephrin 1/40.000). Sedation is a Valium
perfusion. The patient lies on a "vacuum mattress" in order to
turn his body instead of turning his neck sharply to one side. Excessive
torsion-extension of the neck reduces the blood flow in the vertebral arteries,
and thus the blood supply to the inner ear. Moreover, as the proteolytic
enzymes hyalinize the spiral ligament of the stria vascularis in the cochlea,
reduction of the blood supply to the inner ear is more likely to occur.
Jean-Bernard CAUSSE vertebral artery insufficiency nystagmus test, performed
under nystagmography recording prior to the operation, will show poor blood supply to the inner ear when the head is sharply turned to one
side.
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Incision
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Increasing sizes of speculae are tried in order to compress the skin and
thus avoid bleeding, and in order to achieve the best exposure. The speculae
are of nickel and silver and are malleable.
The incision is performed at the limit of the speculum in order to enable the
Vaseline wick to press upon the tympano-meatal flap and consequently avoid
bleeding in the middle ear even if the patient coughs or strains postoperatively.
After the tympano-meatal flap is elevated, the bony canal of the chorda
tympani is opened with a strong hook or scraped by the curette.
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Posterior canal wall |
The posterior canal wall is removed with a curette to give a good exposure
(Fig. 9a). The bone removal should not involve the superior aspect of the
canal wall, as draping of the drum may occur postoperatively. Stagnating
blood may form adhesions in the middle ear. The drum should rest as far
as possible from the long process of the incus. Adhesions may retract, elevating
the long process of the incus. The gauge may only be used in the inferior
part of the bony rim. The curette (named Super Curette) and gauge are part
of the "Causse Instrument Set" as developed by the XOMED-TREACE
Company and MICROFRANCE Company.
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 Fig.9 a : Only the posterior canal wall is resected.
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Incudo-stapedial joint |
The incudo-stapedial joint is divided with a small flat right angle hook
(Fig. 9b). The left hand should at the same time hold the long process
of the incus to avoid any harm to the spiculae in the incudo-mallear joint,
or to the suspensor ligaments of the incus, or to the capsule that surrounds
that joint. If the capsule tears, it will incur a leak of the dense fluid
contained within which the incudo-mallear joint buffers excessive vibration
in case of acoustic trauma with a blast effect. |
 Fig. 9b Disarticulation with a small flat right angle
hook
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The ossicles are gently palpated |
The ossicles are gently palpated to be sure that only the stapes is
fixed, that the incus and malleus are normally mobile. This assessment of
ossicular chain proves the diagnosis of stapes fixation to be correct. |