Keywords
Meniere disease - vertigo - endolymphatic sac
Palavras-chave
doença de Ménière - vertigem - saco endolinfático
Introduction
The first treatment option for Ménière Disease (MD) is pharmacological, including
the use of diuretic, low sodium and low betahistine diet. A variety of other drug
can be used, including antihistamines, benzodiazepines and corticosteroids. The surgical
treatment is considered only when the vertigo caused by this condition evolves to
such a point as to become clinically incapacitating[1].
The target of all surgical interventions is, primarily, to reduce the number and severity
of the acute attacks of vertigo and, secondarily, to improve or stabilize the hearing
loss and the tinnitus or aural fullness. For patients who still remain incapacitated
and with imbalance attacks after three to six months of conservative therapy and unilateral
development of the disease, surgical intervention can be considered[2].
Surgical interventions on MD can be divided into two groups: conservative and non-conservative
of hearing[1].
The non-conservative processes include labyrinthectomies neurectomies and translabyrinthine,
which remove partially or completely the sick labyrinth, and the insertion of aminoglycoside
in the middle ear to perform a chemical labyrinthectomy, which decreases vertigo,
but can lead to hearing loss[3].
There is another group of non-conservative of hearing techniques that act on the distal
endolymphatic system, equalizing the pressures and connecting the endolymphatic and
perilymphatic spaces, acting at saccule level. Some are performed through the platinum
of the stapes, other through the round window. Through oval window, we have sacculotomy,
the tack procedure and sacculocentesis. From the round window, there is “osmotic diuresis”
with NaCl, cochleostomy, cochleosacculotomy, intracochlear shunt and cochlear dialysis.
There are still other techniques, which act in other sections of the labyrinthine
capsule, such as cryosurgery, determining a fistula on the semicircular side canal
or acting on the promontory with a oticoperotic shunt.
Among the conservative of hearing techniques are the endolymphatic sac surgery by
simple decompression, implant of sheet of Silastic® to the mastoid, through capillary
tube or capillary tube with fluid chamber, shunt with unidirectional valve sensitive
to pressure and, finally, shunt for the subarachnoid space. There are included, also,
as conservative measures, the selective vestibular neurectomy via middle fossa, the
retrolabyrinthine neurectomy and the retrossigmoid neurectomy.
The most used procedure of shunt is the endolymphatic sac. Although these surgeries
are relatively complication free and technically of easy realization, their results
are controversial: some authors affirm that there is no statistically significant
improvement of vertigo in relation to the surgical procedures used as placebo[4]; but others state the opposite[5].
The attempt to perform procedures creating endolymphatic shunts at saccule level is
in disuse, for the high index of hearing loss[4].
Since this is an area about which the otorhinolaryngology has many different and of
difficult application concepts, we find that the conceptual ordination about the theme
and respective discussion provide a consistent contribution for readers. For this,
we created the following objectives:
-
To present a bibliographic review of the main surgical techniques with endolymphatic
shunts, that is, the most employed in the treatment of MD.
-
To discuss their results, highlighting a new surgical alternative in experimental
phase that acts on the utricle.
Literature Review
Endolymphatic shunts at endolymphatic sac level
The first endolymphatic shunt procedure was performed by Georges Portmann in February 26th of 1926[6]. As a result of his own researches and the theory proposed by Guild that the longitudinal endolymphatic flow occurred towards the endolymphatic sac[7], Portmann recognized that MD is caused by an increase of pressure at the endolymphatic compartment
of the inner ear. He imagined that the surgery of endolymphatic sac, designed to decrease
the endolymphatic pressure on the endolymphatic compartment of inner ear through the
incision of the endolymphatic sac, would improve the symptoms associated with endolymphatic
hydropsy (hydrops). In this procedure, the endolymphatic sac is opened for the mastoid
process. The surgery was performed with hammer and gouge instead of otologic drill,
and no microscope was used. The sac was simply incised with a small knife, theoretically
reserving the endolymphatic drainage under increase of pressure towards the mastoid.
With greater use of microscope and surgical drills, several modifications were made
to the original surgery of Portmann with the theoretical intent to improve the drainage of endolymph. In 1954, Yamakawa and Naito removed part of the medial wall of the endolymphatic sac to direct the drainage of
the endolymphatic sac towards the subarachnoid space[8]. To avoid infection and decrease of drainage, House, in 1962, created a tube for the endolymphatic-subarachnoid shunt. To place this
polyethylene tube, an incision was made on the medial wall of the endolymphatic sac,
aiming to create an open surgical fistula. Subsequently, several authors, including
Shea
[9] and Paparella and Hanson
[10], and others[11]
[12]
[13]
[14], described implants of sheets of drainage Silastic®, tubes or covering material, which was used for the drainage of the sac towards the
mastoid, thus avoiding that the drainage entered the subarachnoid space. In 1978,
Arenberg et al. added a direction valve to the shunt tube, as had been done in Europe in 1975
by Stahle
[15]. Kitahara et al., following, based their drainage on the opening of the intra mastoid sac,
folding the lateral wall out and inserting a sponge of absorbent gelatin inside the
lumen[16].
Endolymphatic shunts endolinfáticos at saccule level
Endolymphatic shunt surgeries were planned intending to create a fistula through which
the endolymphatic space can be connected to the perilymphatic space, placing the internal
shunt on the otic capsule. This fistula, theoretically, would drop the pressure as
it drained the flow to the perilymphatic space of low pressure.
The first procedure performed with this intent was named sacculotomy. In 1964, Fick, using histologic evidences of saccule distension in patients with MD, proposed that
the rupture of the distended sacculus might equalize the pressure between endolymph
and perilymph. The author recommended a puncture on the platinum of the stapes with
a needle to make the rupture at the base of the saccule. Cody modified Fick's procedure, placing a stainless steel tack each time there would be distension.
This surgery was performed through the external auditory meatus, proceeding to tympanomeatal
retail. Unfortunately, many patients suffered progressive hearing losses after being
put through these surgeries. Schuknecht noticed that the designers of these procedures
had not predicted that the distended saccular wall was usually attached to the platinum
of the stapes in MD, thus causing, in long-term, a difficulty to generate an efficient
and permanent fistula[18].
Cochleosacculotomy
This procedure was proposed in 1982 by Schknecht, based on scientific observations. He observed, in animal models, that the fistulae
between the perilymph and endolymph compartments on the inner ear were compatible
with the preservation of hearing and demonstrated that the existence of such fistulae
occurred spontaneously in temporal bones in humans. Schukencht believed that these fistulae caused regression of the clinical symptoms of MD and
that they could be permanently created via fracture and rupture of the cochlear duct[6].
Indicated as treatment for elderly patients with incapacitating symptoms, who have
poor hearing, but reveal good vestibular function in electronystagmographic tests[1], and by quickness and simplicity of the procedure, the cochleosacculotomy is performed
under local anesthesia. It starts with the creation of a tympameatal retail, through
which the niche of the round window is exposed. A 3 mm right angle blade is introduced
in all its length through the membrane of the round window, towards the oval window.
At this pont, the instrument advances through the bone spiral lamina and penetrates
the saccule. The blade is removed, and the membrane of the round window is covered
with perichondrium, fat or temporal fascia. The tympanomeatal retail is then reattached.
Endolymphatic shunt at utricle level.
The first surgical procedure of endolymphatic shunt acting in the utricle was proposed
by Lavinsky et al. in 1999[19]. The intention of this procedure was related to the expectation of a smaller auditory
damage, knowing that the utricle doesn't belong to an anatomofunctional unity with
the cochlea, like the saccule. In experimental stage, the method named utriculostomy
consists in obtaining a permanent fistula on the membranous labyrinth, thus communicating
the endolymphatic and perilymphatic spaces at utricle level. The procedure was put
into practice in sheep, through the oval window, using a microcautery by radiofrequency
with exposure time and temperature programming. Localized heat, applied with 0,20mm
needle, generates loss of substance. As observed in histologic exams, there is regeneration
in the treated area, forming a frail membrane that behaves like a valve, breaking
up in moments of endolymphatic hydrops and, thus, communicating both spaces and avoiding
a permanent ionic mix and its known consequences.
Experimental utriculostomy was performed in 12 sheep at the Veterinary Hospital at
Veterinary Medical School of Universidade do Rio Grande do Sul, Porto Alegre, RS.
After anesthesia, the endoperiauricular area of the animals was exposed and the tympanic
membrane removed according to the technique describe by House et al.[20], employed in stapedectomies.
The promontory, oval and round window, facial nerve, chorda tympani, pyramidal apophysis
and tensor ligament of the stapes were exposed. Thus, the tensor ligament of the stapes
was sectioned and the disjunction of the incudostapedian articulation was performed.
The superstructure of the stapes was fractured, and all the platinum was removed.
With a diamond drill, approximately 2mm from the posterior edge of the oval window
were removed towards the facial nerve. The widening of the oval window facilitated
the cautery procedure on the utricle.
The anterior wall of the utricle, partially visible during the otomicroscopy, was
cauterized using a microcautery with 0,2mm tip for 0,5 seconds, at intensity of 3,5
W. the cauterization was repeated in three places close to each other. The oval window
was closed with adipose tissue removed from the region close to the endoperiauricular
incision and covered with Gelfoam®. The tympanum was reinserted, and the external auditory meatus tamponade with Gelfoam®. Finally, the region was covered with compressive bandage.
Three months after surgery, the animal was sacrificed, and its temporal bone was submitted
to relevant histological study at the histopathology laboratory directed by Michael Paparella (University of Minnesota, Minneapolis, EUA). It was possible to demonstrate the effectiveness
and safety of the proposed technique, with positive results.
Discussion
Mechanisms of secretion and reabsorption performed in medium scale through the heterogeneous
epithelium needs to be well balanced to maintain a constant volume of fluid. Failures
at the maintenance of this balance will result in dilatation of the endolymphatic
compartment observed in MD. It's also been admitted that this increase of endolymphatic
pressure might break the membranous labyrinth and originate a mixture between endolymph,
rich in potassium, and perilymph, poor in potassium[21]. Potassium unbalance would prevent the depolarization and originate transitory loss
of function until the membrane was repaired and the sodium-potassium relations were
restored.
We believe that vertigo results from mechanical over-stimulation of the sensorial
cells due to distension of inner ear structures. This is caused by dysfunction of
the sac, damaged by fibrosis, infection or autoimmune or allergic processes. Other
possible mechanism is the exaggerated production of glycoproteins, which would originate
an excessive inflow of endolymph on the sac[21].
Data from literature indicate that at least 85% of the patients with MD will answer
positively to clinical treatment[4]. However, even after 20 years suffering from the disease, 21% of the patients remain
with vertigo[22]. In a prospective study involving 243 patients, there was an increase of cases with
severe or very severe attacks[22], thus showing that, once vertigo becomes incapacitating despite the pharmacological
treatment, surgical procedure is recommended.
The decompression of the endolymphatic sac is a surgical alternative for those patients
who present resistance to the pharmacological therapy. This safe and conservative
of the endolymphatic sac option can be performed with or without the use of a shunt[1].
The logic of this surgery is much debated. On the base is the understanding that the
shunt drains the excess of endolymph and widens the sac's inner space, expanding the
absorption surface, while the osseous decompression reduces the pressure and increases
blood supply and changes[23].
On surgical procedures of the endolymphatic sac without shunt, is performed a wide
osseous decompression of the sac, the sigmoid area and the area of the jugular bulb,
without entering the endolymphatic sac itself. Results of long-term segments showed
that the surgery is safe and efficient for the control of vertigo and the stabilization
of hearing[24]. Improvement indexes go from a scale of 85 to 100%, and the stabilization or improvement
of hearing can reach almost 85%[25].
The shunt surgery of the endolymphatic sac is a modification of the surgery without
shunt. In this case, a shunt is created for the subarachnoid space. The result of
the treatment is compatible to that of the mastoid endolymphatic shunt[26]. However, in long-term, the presence of fibrosis or the closing of the incision
of the endolymphatic sac can prejudice the results. The application of intraoperative
mitomycin C on the incised endolymphatic sac can be beneficial in these cases[27], and the instillation of steroids during surgery can help to control vertigo, to
stabilize hearing and to decrease the tinnitus[28]
[29]. Vertigo control occurs in 60-70% of the cases in shunt surgery of the endolymphatic
sac[26]. Despite that, it has been suggested that the impact of endolymphatic sac shunts
over the symptoms of patients with MD is very similar to the one obtained with placebo[3]
[30], and some studies support the concept of placebo effect in these surgeries. The
insertion of ventilation tube on the tympanic membrane, the complete extra-osseous
removal of the endolymphatic sac and cortical mastoidectomy presented similar results
to the procedure of shunt of the endolymphatic shunt[31]
[32]
[33]. However, the study of Thomsen et al. had a small sample and arguable statistic characteristics. Pillsbury et al.[5] repeated the study and obtained 87% of positive results for shunt, against 47% for
placebo[34].
On the other hand, the surgical procedure itself can be critical, because the anatomy
of the endolymphatic sac shows variations, and the surgeon may have difficulties to
find and widen its internal space in some cases - this condition can affect the results
of the surgery. The preservation of the integrity of the endolymphatic sac is also
important. An appropriate surgery can result in indexes of 90% of vertigo control[35].
The endolymphatic sac surgery can be performed in children or seniors, in patients
with unilateral hearing loss and in cases in which MD coexists with other diseases,
like fistulae, otitis media and otosclerosis. It can be performed bilaterally, but
cannot be applied in vertigo conditions other than endolymphatic hydrops. The surgery
can result in a 2% hearing loss, what can be attributed more to infection or inflammation
than to the surgical procedure itself[36]. Though the results of the endolymphatic sac surgery are conflicting, it's been
one of the most commonly performed surgical procedures in MD[35]
[36]
[37]. A study performed at the same institution using the American Academy of Otolaryngology
- Head and Neck Surgery guide showed that both the shunt surgery of the endolymphatic
sac for the mastoid and the decompression of the endolymphatic sac are effective for
patients with MD[38]. The surgery of decompression of the endolymphatic sac, as described by Paparella and Sajjadi, remains the keystone of surgical therapy for patients with MD. According to the
authors, the procedure resisted to the time test, being a relatively safe procedure,
with a lower than 2% index of significant sensorineural hearing loss and less than
1% risk of paresis of the facial nerve, important control (85%) of vertigo during
2 to 5 years, with excellent results also when reviewing the increase of endolymphatic
sac surgery. Other studies, however, have demonstrated that the endolymphatic sac
surgery does not alter, in long-term, the natural course of vertigo in MD[39]
[40]. In patients with MD for over 20 years and that had been submitted to the endolymphatic
sac surgery, all presented long, intense and frequent vertigo crisis in comparison
to those who hadn't performed the surgery, and 90% considered their attacks to be
severe or very severe[22].
Sacculotomy includes the drainage of the dilated saccule, with the resulting elimination
of hydrops. Despite the present modifications in the sacculotomy techniques, CODY's
tack operation was the most popular of the surgical procedures performed at the saccule.
According to some authors, this surgery can be an option when the patient has a hearing
loss in the ear with hydrops, because almost 50% of the patients will have a worsening
of hearing, despite the vertigo control with indexes over 60%[41]. In recent histopathological study[42] of the temporal bone of patients submitted to tack operation, were observed severe
endolymphatic hydrops and more severe degenerative changes in the Corti organ and
cells of the spiral ganglion when compared to those of the contralateral ear, which
was not operated. Severe degeneration of the saccular macula was also observed on
the operated ear. According to the authors, these findings are consistent with the
results of the study of hydrops in animal model, where the endoperilymphatic surgical
fistulae were not enough to reduce the hydrops and still caused degenerative changes
in structures of the inner ear[43]. Although authors[42] didn't have the means to detect hydrops and structural changes in the inner ear
before and soon after surgery, their findings suggest that this kind of surgery was
successful more by alleviating vertigo through the destruction of ciliated cells of
the saccular macule, than by the resolve of the endolymphatic hydrops. Considerable
damages to Corti organ also demonstrate risks of hearing loss.
Schuknecht developed the cochleosacculotomy, creating a fistula between endolymph and perilymph
with access via round window. Its results were analyzed by the author himself (Schuknecht), designer of the procedure. According to the author, the advantage of this surgery
is its technical simplicity and short realization time. In his revision of 120 cases,
an extended improvement of vertigo was achieved in 70% of the cases[44]. These results are better than the ones obtained with any other endolymphatic sac
shunt procedure, but can be considered poor in comparison with neurectomy of the vestibular
nerve, for example, that reaches 94% of vertigo control. Partial hearing losses were
observed in 25% of the patients, and deep sensorineural deafness occurred in more
than 10%, against less than 5% associated to vestibular neurectomy. Though other studies[45]
[46] demonstrate vertigo control in more than 80% of the cases, the cochleosacculotomy
is not advocated because, in long-term, this control is poor, and 30-80% of the patients
will have significant hearing loss[47]. Currently, cochleosacculotomy is rarely performed, but can be considered for elderly
and cofotic patients with MD[48].
Utriculostomy, surgical alternative in experimental stage designed by Lavinsky et al.[19], consists in obtaining a permanent fistula on the membranous labyrinth, communicating
the endolymphatic and perilymphatic spaces on the utricle. Such objective was put
to practice in sheep through the oval window, using a radiofrequency microcautery
with exposure time and temperature program.
According to the author, the method is based on the fact that, when a puncture is
made on the saccule, this tends to present a very fast closing, since it makes a linear
rupture on the membranous labyrinth. On the other hand, localized heat, applied with
0,20mm needle, generates the loss of substance, and was histologically observed that
there is a regeneration, forming a frail membrane that behaves like a valve, disrupting
itself in moments of endolymphatic hydrops and, thus, communicating the two spaces
and avoiding permanent ionic mixture, with its known consequences. By the smallness
of the perforation, it would tend to remain closed between episodes of MD, generating
the communication only in moments of endolymphatic hydrops. Therefore, utriculostomy
offers clear advantages concerning permanent endo and perilymphatic communication.
Actually, it is probable that utriculostomy might create a new “valve” in replacement
of the malfunction of the utricle-endolymphatic valve, also called Bast valve[49]. Although its function is still uncertain, in the opinion of some authors[50] it would close itself to prevend a larger endolymph loss on the utricular system
in case of a decrease of pressure in all the endolymphatic system - or, as Zechner
[51] proposed, its dysfunction would be the cause of endolymphatic hydrops.
On post-operatory observations, despite the heavy manipulation of the vestibule, authors
relate absence of significant losses of balance and posture. Some animals showed alterations
in dynamic balance, which disappeared 24 hours after the procedure, and no nystagmus
were observed.
By not acting on the saccule, that has intimate anatomical relation with the cochlea,
the authors hope to be able to demonstrate the existence of a smaller cochlear repercussion
in utriculostomy when compared to sacculostomies.
Final Considerations
Literature about endolymphatic shunt surgeries shows many controversies about its
effectiveness in treatment of incapacitating MD, and many studies relate prejudicial
damages to the inner ear. The experimental surgery called utriculostomy appeared as
a new and promising option for the surgical treatment of MD, for presenting advantages
compared to the other modalities. Additional researches must focus on the assessment
of these aspects.
