Last edited: 10/2012
- What are Destructive Treatments of Vertigo?
- Gentamicin Injections
- Surgical Treatments
What are Destructive Treatments of Vertigo?
Destructive treatments of vertigo refer to medical or surgical procedures that deaden the inner ear. They are considered when it is clear that vertigo is coming from the inner ear, that the vertigo cannot be otherwise controlled, and generally also when the disease process is confined to one ear. Destructive treatments are usually a last resort treatment for persons who have severe cases of episodic vertigo, such as due to Meniere’s disease. Occasionally destructive treatments are advocated for tinnitus, but these are not discussed here.
Destructive treatments all involve a trade-off between partial or full immunity to vertigo due to fluctuation of the inner ear, and overall inner ear function. All persons with destructive treatment can expect to have worse inner ear function than a normal person with two functioning inner ears. As these procedures are nearly always done for vertigo, in general, there is an attempt to preserve hearing. Once it is clear that a destructive procedure is indicated, what remains is to choose among several possibilities outlined below. In recent years, this process has become simpler as one procedure, Gentamicin injection, has become much better understood, popular, and generally preferable.
Gentamicin injection into the ear is presently the most common destructive procedure for vertigo. Surgical procedures (vestibular nerve section and labyrinthectomy) are also available, but these days they are falling from favor.
A substantial advantage of gentamicin injections is low cost, compared to surgical procedures. Most authors find that the control of vertigo is comparable to surgical vestibular nerve section (about 90%). Gentamicin injections are also intrinsically of very low risk, especially compared to nerve section. Compared to labyrinthectomy, the lowest risk surgical procedure, gentamicin injections are also lower in risk because there is no need for general anesthesia.
Injections of gentamicin are given through the ear drum, by way of a small needle (see Figure 1). This process may be called either transtympanic gentamicin treatment (TTG) or intratympanic gentamicin treatment. This procedure allows the doctor to treat one inner ear, without affecting the other. Typically four injections are given in total, administered on a once-per-week basis.
The procedure is not (very) painful: a local anesthetic is used to numb the ear drum. The treatment is stopped when vertigo ensues, indicating that the gentamicin is affecting the inner ear. Rarely, even after six injections, vertigo cannot be induced and vestibular function remains normal. At this point, treatment is stopped and another method of eliminating vestibular function is used (such as labyrinthectomy).
After treatment is stopped, vertigo usually lasts from seven to ten days, but may take as long as a month to resolve. Symptoms are controlled with vestibular suppressants and medications for nausea. Good family support or admission to the hospital is required at this point. Unsteadiness usually resolves after several months, but in older individuals, some unsteadiness may be permanent (although vertigo spells are nearly always stopped).
The main risk is that hearing may worsen. As protocols evolve, the percentage of treatments associated with hearing reduction continues to gradually be reduced; however, there is still some risk of hearing loss. Currently, there is risk of approximately 30% that a patient will develop a mild reduction in hearing (Blakeley et al., 2009). Gentamicin injection is associated with a higher rate of hearing loss than surgical nerve sectioning (Colletti, 2007; Hillman, 2004).
We believe, based on pharmacokinetic considerations, that protocols where the gentamicin is administered gradually, on a once-per-week schedule (or less frequently), are less risky to hearing than protocols where a large amount of medication is administered over a week or less. If a patient has already lost usable hearing on the “bad” side, then the risk is eliminated, and either a slow or quick protocol can be used.
Results, in terms of relief from vertigo, are typically very good. Hearing is generally unaffected or worsened, and may continue to worsen even after vertigo spells are stopped. Tinnitus is also generally unaffected but some recent studies report reduction in tinnitus. Some patients get relief from Meniere’s disease symptoms in spite of a subtotal ablation of vestibular function. This is attributed to selective damage of gentamicin to the dark cells of the labyrinth (Okuda et al., 2009; Atlas, 1999; Pender, 1985). Disability is lessened in patients with Meniere’s disease after TTG treatment (Boleas-Aguirre et al., 2009)Some studies have found that subjective quality of life is unchanged (Soderman et al, 2001), while others have found an improved quality of life following treatment (Suryanarayanan et al., 2009; Banerjee, 2006). Dizziness may reoccur one year later, requiring another series of injections. Several authors have reported that tinnitus or the sensation of fullness may improve substantially after TTG (for example, Herraiz et al., 2010).
Variant Gentamicin Injection Procedures
Many variants of this protocol have been reported. Streptomycin injection has been tried in two published studies (for example, Schuknecht, 1951), with much worse hearing results than gentamicin. This may be caused by the relative selectivity of gentamicin for the vestibular hair cell, compared to dihydro-streptomycin. It would seem however that streptomycin sulfate might be equally effective as gentamicin.
A single dose treatment was reported by Driscoll et al (1997) at the Mayo clinic, with 84% response rate in terms of vertigo, and no change in hearing. These results are attributed to claims that gentamicin destroys the endolymph secreting dark cells before destroying the sensory vestibular epithelium (Beck, 1978). Variant procedures where gentamicin is administered less frequently (such as once-per-month), or in a more dilute solution than is conventional also seem well worth considering.
Injection of gentamicin directly into the vestibular system, rather than through the tympanic membrane or round window may result in less damage to the cochlear hair cells responsible for hearing (Lii, 2004). More research is necessary before this method will become widely available.
Some studies suggest transtympanic dexamethasone treatment (dexamethasone is a steroid, and not related to gentamicin). At this update, (9/2012), the benefit of this procedure has not been clearly shown. It may be worth trying in situations where all else has been tried and there is little to loose. For example, its use might be considered when the remaining ear affected by Meniere’s disease is the only-hearing ear. Casani et al. (2011) found TTG to be far more effective than dexamethasone; for the latter treatment, hearing was only preserved in those who had non-recurring vertigo.
What if TTG Fails?
There are a number of reasons why TTG might fail. First, the diagnosis might be wrong. The patient might have a central disorder (such as Migraine), the patient might have a nerve disorder (such as microvascular compression), or the patient might have bilateral Meniere’s disease.
Second, the drug might be ineffective. This could happen if it isn’t delivered to the inner ear (perhaps due to adhesions over the round window); if the individual being treated might have an idiosyncratic resistance to gentamicin (idiosyncratic susceptibility has been documented, perhaps there is also resistance); or if there might be recovery. It is common for Meniere’s disease attacks to return one or two years after the first TTG treatment.
When TTG fails, careful consideration should be made to exclude wrong diagnosis. If the diagnosis still appears to be sustainable, then one may wish to consider more radical procedures such as vestibular nerve section or labyrinthectomy.
Where Can I Get Gentamicin Injection Treatments?
Nearly all major medical centers now offer transtympanic gentamicin treatment through their otolaryngology service. However, recall that the treatment series, for persons with usable hearing on the side to be treated, requires four to six weeks to complete. Before having transtympanic gentamicin treatment, we also think that it is prudent to try all reasonable medical avenues of treatment.
If gentamicin injections fail, there are surgical treatments available: vestibular nerve section and labyrinthectomy.
Vestibular Nerve Section
A vestibular nerve section describes the process of cutting the vestibular part of the cochleovestibular cranial nerve. This is generally done in an attempt to eliminate recurrent attacks of vertigo.
The usual reason for a vestibular nerve section is control of unilateral Meniere’s disease, where there is some hearing (better than 80 dB PTA). On extremely rare occasions it is performed for other reasons such as recurrent vestibular neuritis. Relative contraindications are bilateral vestibular disease, old age, poor medical condition, or central nervous system involvement.
If hearing is not an issue then a labyrinthectomy can be done. Results presented by De La Cruz et al. 2007 demonstrated that labyrinthectomy and vestibular nerve section provide similar control of vertigo, however the authors reported that the latter showed more improvement with regard to imbalance and functional disability .
The vestibular nerve may be sectioned (cut or severed) via the middle fossa, retrolabyrinthine, and retrosigmoid approaches, with similar efficacy. Surgical treatment is traditionally felt to be indicated when the patient is incapacitated with unilateral Meniere’s disease and quality of life is affected. Historically 20% of patients eventually have had surgery done (Silverstein and Rosenberg, 1992), but with the advent of transtympanic gentamicin treatment, operative treatments are being replaced by outpatient procedures.
Figure 2 is a picture of the inner ear which can be used to appreciate the route of the most common operation, the retrolabyrinthine approach. This entails an attempt to cut the nerve(labeled #8 on the right side of this diagram) going through the mastoid sinus (behind the plane of the picture) and the cranial cavity to get access. The picture on the right was taken by Dr. Alan Micco, and shows the actual appearance of the surgery.
The middle fossa approach is similar, but access to the cranial cavity is obtained with the assistance of a neurosurgeon, from a slightly higher location. In the retrosigmoid approach, access to the nerve is obtained by going through the posterior (back of head) part of the skull.
Complications of vestibular nerve section
Although 95% of patients are satisfied with the procedure immediately after their surgery, there are substantial risk of a serious complication in all of the described surgical procedures. All available procedures — retrolabyrinthine, retrosigmoid, and middle-fossa have significant risks.
Failure of Vestibular Nerve Section
Although from the name of the procedure one would expect that the entire vestibular nerve would be cut, in reality this is not always possible. According to Eisenmen (2001) there is evidence for retained vestibular function in about half of patients following nerve section or labyrinthectomy. Some of the fibers of the vestibular nerve run very close to the cochlear (hearing nerve), and because of this they may be spared. Saccule derived nerve fibers may be purposefully spared because they tend to run close to the cochlear nerve (Silverstein et al, 1994). Sometimes there is an attempt to cut these fibers at another site with a singular neurectomy. Singular neurectomies, however, are somewhat difficult and unreliable even in very experienced hands.
Some individual factors may help to predict who will have poor outcomes after surgery. In one study, a high rate of disability and more frequent vertigo attacks were factors associated with a poorer result (Teufert, 2007). Patients with Meniere’s disease had better outcomes.
Cerebrospinal Fluid (CSF) Leaks From Vestibular Nerve Section
About 10% of cases with retrolabyrinthine nerve sections develop a cerebrospinal fluid (CSF) leak, which is treated with continuous lumbar drainage for several days.
Facial Weakness From Vestibular Nerve Section
The facial nerve (#7 on the diagram above) runs adjacent to the vestibular nerve, and it can be damaged by procedures that intend to damage the vestibular nerve. This complication is rare in recent times due to better surgical technique and the availability of facial nerve monitors.
Postoperative headaches are common in the retrosigmoid approach. Approximately 25% of patients undergoing this procedure develop severe headaches requiring medication two years later.
The middle-fossa approach is essentially a neurosurgical approach. The skull must be opened and the brain retracted. Neurosurgical procedures intrinsically have considerably more risk than those where the brain is not exposed. Our view is that middle fossa nerve sections are rarely indicated, as gentamicin injection treatment has similar effectiveness with much less risk.
Labyrinthectomy refers to surgical removal of the inner ear (labyrinth). It is appropriate for patients in whom there is no hearing in the ear which is causing vertigo. Labyrinthectomy offers excellent control of vertigo, with fewer complications than nerve section. Patients report a significant improvement in quality of life after labyrinthectomy despite hearing loss (Diaz, 2007). Labyrinthectomy results in greater improvement in dizziness than nerve sectioning (Badke, 2002).
Labyrinthectomy can also be performed in combination with vestibular nerve section. In one small study, patients who had labyrinthectomy concurrently with nerve section experienced greater improvement in disability and imbalance than patients who underwent labyrinthectomy alone (De la Cruz, 2007).
Considerable research is ongoing regarding destructive treatments. The greatest amount of interest right now is in refining the technique of gentamicin treatment. Methods of reducing the amount of hearing impairment, and smaller dose protocols are of considerable interest. At the American Hearing Research Foundation (AHRF), we are interested in projects that might lead to improved treatments of vestibular disorders. Click here if you would you would like more information about contributing to the AHRF’s efforts.
Figures are courtesy of Northwestern University, Chicago, Illinois.
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