A ppt about how intratympanic gentamicin injections are helpful in treatment of meniere's disease

1. Intratympanic
Gentamicin
Injections

2. Introduction
Intratympanic Gentamicin injections are the important aspect pf
clinical otologic practice, especially for the management of
Meniere’s disease.
Delivering drugs across the tympanic membrane to the middle ear
space allows one to target the tissues of inner ear while avoiding
risks associated with systemic and surgical therapies.
Both IT Steroids and Aminoglycoside antibiotics are calmly used
in the management of MD.
Aminoglycosides specific ototoxic characteristic is well
established. Directed streptomycin treatment of the middle ear in
the MD patients was first described in the late 1950’s.
Overtime, gentamicin has become favored aminoglycoside for
chemical labyrinthectomy.

3. Gentamicin
Action
Following application of a Gentamicin solution into the
middle ear space, it is primarily passively, absorbed
across the round window membrane and to a lesser
extent oval window.
Once in the peri lymphatic space, inter-scalar exchange,
and interactions of perilymph with CSF at the cochlear
aqueduct, is thought to result in the preferential
concentration of gentamicin in the endolymphatic space
of the vestibule.
In the endolymph of the vestibule, aminoglycoside
antibiotics, including gentamicin, preferentially target
type I vestibular hair cells, leading to their preferential
loss and subsequent vestibular hypofunction.

4. Patient
Selection
Due to the ablative nature of chemical labyrinthectomy, selecting the
appropriate patient is an important initial step in treatment. Although
each patient is intrinsically unique, patients who may be considered for
IT gentamicin treatment include patients suffering from certain MD who
continue to experience troubling vertigo attacks despite maximal
conservative treatment.
Patients must have significant, persistent attacks after treatment with IT
steroids. Pretreatment evaluation includes tests of both cochlear and
vestibular function and a complete history and physical examination
including binocular otomicroscopy. Cochlear functional assessment may
include a complete audiometric evaluation with pure tone audiometry,
speech audiometry, and tympanometry.
Baseline vestibular function may be assessed with videonystagmography
with caloric reflex testing, vestibular evoked myogenic potentials, and
video head impulse testing.

5. Informed Consent/
Complications
When offering IT gentamicin, it is important to discuss the potential risks and benefits.
Notable risks of the procedure include persistent perforation of the TM, failure to
control vertigo, imbalance, the potential need for repeated IT injections, and hearing
loss.
The primary benefit of the procedure is improved vertigo control. Patients should be
counseled that while IT gentamicin is likely to improve their vestibular symptoms, it is
not expected to alter the natural history of hydrops, including ear fullness, fluctuations
in hearing, and progressive decline in hearing.
The principal complication of IT gentamicin treatment is cochleotoxicity experienced as
hearing loss.
Another risk which is difficult to estimate before treatment, but should be considered
in every patient, is the risk of impaired or delayed vestibular compensation.
Research suggests the co-occurrence of MD and vestibular migraine or migraine
symptoms is around 56%-59%.

6. Procedure
The patient is positioned supine in an examination chair or bed. They are
asked to position their head with the car to be treated turned towards the
ceiling. The car is then examined under the microscope, and any cerumen is
debrided using microinstruments.
The TM is topicalized with the phenol at two points: one in anterior inferior
quadrant for the injection, and one in the anterior superior quadrant for a
venting myringotomy.
Prior to injecting the gentamicin solution through the inferior area of phenol
treated TM, the 25 g needed is used to create a small hole in the superiorly
treated TM to act as a vent during injection.
The tip of the needle is then inserted through the inferiorly treated area TM
until the bevel of the needle is fully in the middle ear space, being careful not
to traumatize the middle ear mucosa. Next, the gentamicin solution is slowly
injected into the middle ear.
Slow injection will allow for the middle ear space to fill with the solution while
allowing the displaced air to escape though the vent hole

8. Postprocedural
Monitoring
Postprocedural monitoring includes remote monitoring at home
by the patient, and in-person clinical follow-up.
To minimize the risk of a vertigo associated injury, it is important
to counsel patients to avoid risky activities like driving, operating
heavy machinery, swimming, climbing ladders, activities on
elevated surfaces, and other activities which may cause injury
during a sudden vertiginous attack, for 2 weeks after the
procedure and until they no longer feel off-balance.
A prescription for vestibular suppressant medications
(Clonazepam, Meclizine, and/or Promethazine) may be
prophylactically prescribed to reduce symptoms of dizziness,
nausea and vomiting if patients experience acute vertigo.

9. Conclusion
Not every patient suffering from MD will
require IT gentamicin, it is a treatment
modality that should be considered in patients
who experience persistent, recurrent vertigo
attacks despite maximal medical therapy and
lack of responsiveness to IT steroid treatment.
Appropriate patient selection and counseling is
strongly recommended, given the ablative
nature of theprocedure and the risk of hearing
loss.