PHYSIOLOGIC, ANATOMIC, AND PATHOLOGIC RATIONALE

Meniere’s disease is characterized pathologically by progressive endolymphatic hydrops that is probably related to a disturbance in endolymphatic sac function. This condition must be differentiated from nonprogressive endolymphatic hydrops, in which the hydrops is the result of a single traumatic or inflammatory insult to the labyrinth, causing a permanent but not progressive endolymphatic hydrops.¹

The symptoms of progressive endolymphatic hydrops can be correlated with two principal types of pathologic change: (1) distentions and ruptures of the endolymphatic system,^2,3 and (2) alterations in the cytoarchitecture of the auditory and vestibular sense organs, sometimes accompanied by atrophic changes. Coincident with rupture, there is sudden contamination of the perilymphatic fluid with neurotoxic endolymph (140 mEq/L of potassium) that causes paralysis of the sensory and neural structures and is expressed clinically as episodic vertigo, fluctuating hearing loss, or both. The American Academy of Otolaryngology–Head and Neck Surgery (AAOHNS)⁴ recommended that these episodes be designated the “definitive” symptoms of Meniere’s disease.

As the disease progresses, there are changes in the cytoarchitecture of the sense organs that consist of distortion and atrophy of the sensory cells and supporting cells, and disruption and deformation of their gelatinous aprons. These alterations impair the motion mechanics of the sense organs, resulting in permanent functional deficits. The symptoms for the auditory system are hearing loss and tinnitus, and for the vestibular system are constant or recurring sensations of unsteadiness, described as being off-balance, floating, tilting, falling, or spinning, and are often aggravated by head movement. The AAOHNS recommended that they be known as “adjunctive” symptoms. To be successful, surgical procedures based on facilitating drainage of endolymph should alleviate definitive symptoms and arrest the progression of adjunctive symptoms.

Internal shunt procedures include the sacculotomy of Fick,^5,6 the tack operation of Cody,^7,8 the otic-perotic shunt of Pulec and House,⁹ and the cochleosacculotomy.¹⁰ In the sacculotomy and tack procedures, picks are introduced through the footplate of the stapes to puncture the saccule with the hope of producing a permanent fistula in the saccular wall by which excessive endolymph can drain into the perilymphatic space. This approach fails to consider, however, the histopathologic observation that in Meniere’s disease, the distended saccule often fills the vestibule; its distended wall is adherent to the footplate and could not be fistulized into the perilymphatic space by these maneuvers.¹¹ The otic-perotic shunt, as conceived by House and Pulec, involves the placement of a platinum tube through the basilar membrane to connect the scala media and scala tympani; however, the procedure is not surgically feasible because of the small size of the cochlear duct.

The cochleosacculotomy operation consists of creating a fracture-disruption by impaling the osseous spiral lamina and cochlear duct with a pick introduced through the round window. The rationale is supported by two histopathologic observations and muted by a third:

PATIENT SELECTION

Some otolaryngologists believe that surgery is never indicated for the relief of symptoms of Meniere’s disease because in the normal course of the disease, the vertigo eventually subsides. This approach has merit if the patient is not unduly handicapped. In many cases, however, the dysequilibrium erodes occupational efficiency and recreational and family lifestyle to the extent that invasive therapy is justified. This approach applies to patients having frequent and severe vertiginous episodes unrelieved by medication and patients having falling attacks (Tumarkin’s otolithic catastrophe).¹⁹

Some general considerations need to be addressed before cochleosacculotomy is recommended. The diagnosis of Meniere’s disease must be unequivocal. Other disorders that cause fluctuating hearing loss and episodic vertigo, such as otosyphilis, inner ear autoimmune disease, perilymph fistula, demyelinating diseases, and intracranial neoplasms, must be ruled out. The operation is not recommended for patients who present with audiovestibular symptoms that are atypical for progressive endolymphatic hydrops. There should be no evidence of involvement of Meniere’s disease or other disorders that might be progressive in the opposite ear. It is prudent to require a duration of symptoms of at least 1 year. The opposite ear becomes involved in almost 50% of cases, sometimes many years after the onset of symptoms in the first ear.

Cochleosacculotomy is the procedure of choice for patients who for health reasons are at risk for the stress of postoperative vertigo, and who should not have general anesthesia, and for elderly patients who often compensate poorly to procedures that ablate vestibular function. It has the advantage of being technically simple to perform, is almost totally free of morbidity, and carries little or no risk of mortality. Labyrinthectomy is more certain than cochleosacculotomy to relieve disabling episodic vertigo; however, it has the disadvantage of producing severe postoperative vertigo, permanent hearing loss, and, in some cases, prolonged dysequilibrium. For these reasons, some patients may choose to have a cochleosacculotomy as a first attempt to resolve their vertigo problem.

SURGICAL TECHNIQUE

The ear is prepared and draped similarly to any transcanal procedure. The operation is performed under local anesthesia. With the aid of a nasal speculum, the fibrocartilaginous external auditory canal is infiltrated circumferentially in four positions with 1% lidocaine (Xylocaine) containing 1:100,000 epinephrine, using a 27 gauge, 1.5 inch needle. The ear canal is dilated with the nasal speculum, which also serves to diffuse the anesthetic solution uniformly into the tissues. An ear speculum of the surgeon’s preference is introduced into the ear canal and locked in an adjustable speculum holder, freeing both of the surgeon’s hands. The posterior aspect of the bony canal is exposed, and the skin of the bony canal is infiltrated at two sites with 1% lidocaine containing 1:1000 epinephrine, using a 30 gauge, 1.5 inch needle. The beveled opening of the needle must be introduced flush against the bone at an obtuse angle, and the blanching area of infiltration should extend to the tympanic annulus from the 6 to 12 o’clock position. Adjustments of the speculum and speculum holder are made as often as necessary to achieve optimal exposure of the surgical field.

Incisions are made, and a triangular skin flap is elevated to the tympanic annulus (Fig. 39-1A). Bleeding must be meticulously controlled at all times. The tympanomeatal flap is elevated by lifting the tympanic annulus from its sulcus and folding the flap into the anterior tympanomeatal angle of the ear canal (Fig. 39-1B). The chorda tympani nerve and the ossicles are not disturbed. The ear speculum is locked into a position that exposes the round window niche and posterior aspect of the hypotympanum. In rare cases, the round window niche is partly hidden behind the posteroinferior part of the bony tympanic annulus, in which case a small burr is used to remove sufficient bony annulus to allow access to the round window niche.

FIGURE 39-1 A, Skin incisions are made in the posterior wall of the bony external auditory canal. B, Tympanomeatal flap is elevated and reflected into the anterior tympanomeatal angle. C, A 3 mm right angle pick is advanced through the round window membrane in the direction of the oval window. D, If niche does not accommodate a 3 mm right angle pick, the bony lip of the round window is removed, and a 2 mm right angle pick is used to accomplish the cochleosacculotomy. RW, round window.

Usually, the round window niche accommodates a 3 mm right angled pick without removal of bone. The pick is advanced through the round window membrane, which may or may not be visible. The pick is guided in the direction of the oval window while hugging the lateral wall of the inner ear to ensure that the cochlear duct is traversed (Fig. 39-1C). When the pick has been introduced to its full 3 mm length, the end of the pick is located beneath the footplate of the stapes. Occasionally, the subiculum, which is a ridge of bone lying in the boundary between the round window niche and sinus tympani, interferes with introduction of the pick. It can readily be shaved down with a 2 mm burr. Occasionally, the overhanging bony lip of the round window niche must be removed to accommodate the pick (Fig. 39-1D). In this case, a 2 mm (rather than a 3 mm) pick is used to avoid excessively deep penetration into the vestibule and possible injury to the utricular macula (Fig. 39-2). Rarely, a high jugular bulb blocks access to the round window niche, in which case it may be necessary to abort the operation (Fig. 39-3).

FIGURE 39-2 Vertical section of normal ear shows anatomic features of middle and inner ears that are relevant to cochleosacculotomy. Histologic sections represent similar anatomic characteristics as the drawing. CD, cochlear duct; Dr, ductus reuniens; RW, round window; S, saccule; U, utricle.

FIGURE 39-3. Vertical section of normal ear shows high jugular bulb abutting tympanic annulus and encroaching on round window niche. Other sections show reduced orifice leading to a small niche. It is not feasible to attempt cochleosacculotomy in such cases. IAC, internal auditory canal; OW, oval window; RW, round window; SS, sigmoid sinus.

Occasionally, a slight loss of resistance is felt as the pick passes through the cochlear partition and causes the planned fracture-disruption of the osseous spiral lamina and cochlear duct (Fig. 39-4). Usually, patients experience no sensation as the pick is advanced, but a few have noted momentary vertigo, and several have reported hearing a “click.” The maneuver does not produce vertigo, presumably because the vestibular sense organs are not mechanically disturbed, and the endolymph from the fistulized area drains into the scala tympani rather than into the perilymphatic space of the vestibule. The pick is withdrawn, and the perforation in the round window membrane is sealed by a tissue graft of perichondrium or adipose tissue. The operation is terminated by returning the tympanomeatal flap to its original position. Strips of silk cloth are laid over the incisions, and a round synthetic rubber sponge of appropriate size is placed in the canal to maintain slight pressure on the skin flap. Cotton is placed in the ear canal. A few patients note slight unsteadiness for 1 or 2 days; however, all feel well enough to be discharged from the hospital the next day. The packing is removed 1 week later, at which time the tympanic membrane and canal wall skin should be well healed.

FIGURE 39-4 A and B, A 3 mm right angle pick is shown penetrating dilated cochlear duct and dilated saccule. Dr, ductus reuniens; M, macula; OSL, osseous spiral lamina; RW, round window; S, saccule; ST, scala tympani; SV, scala vestibuli; U, utricle.

Serial hearing tests at weekly intervals show a sensorineural hearing loss for 2 to 3 weeks, followed by recovery in most cases (Ginsberg I, personal communication). The authors first test hearing 6 weeks after surgery, when the hearing has stabilized. The complications of cochleosacculotomy are similar to the complications for stapedectomy and include perforation of the tympanic membrane, tears of the jugular bulb, postoperative otitis media, sensorineural hearing loss, facial nerve injury, and perilymph fistula. The only significant complication in cochleosacculotomies performed by the authors, other than sensorineural hearing loss, was one case of otitis media that resulted in profound sensorineural hearing loss in the infected ear.

RESULTS

The Massachusetts Eye and Ear Infirmary experience currently consists of 142 cochleosacculotomies performed since April 1979.^20–22 Follow-up times average 6.16 years, ranging from 1 month to 7.4 years. Definitive control of vertigo has been achieved in 68.3% of patients. Hearing was made worse in 35.2% (as defined by AAOHNS criteria⁴ of either 15 dB loss in pure tone average or 15% loss in speech discrimination). Postoperative profound sensorineural hearing loss occurred in 11%.

The success rates reported for either internal or external endolymphatic shunt procedures should be viewed with some caution. In a review of 834 articles published on Meniere’s disease between 1952 and 1975, Torok²³ found that almost without exception, advocates of either medical or surgical treatment reported success rates of 60% to 80%. Not only is there a strong placebo effect, but also sudden prolonged remission of symptoms are characteristic of Meniere’s disease. Some patients who had vertiginous attacks on a weekly basis (or more often) had a total cessation of attacks after cochleosacculotomy. In the management of disabling Meniere’s disease, cochleosacculotomy is a useful alternative to vestibular nerve section and labyrinthectomy in selected cases.