Treatment of Superior Canal Dehiscence (SCD)

Timothy C. Hain, MD   Marcello Cherchi, M.D. Page last modified: July 5, 2020

See also: SCD (overview) SCD diagnosis. SCD references

 

How is Superior Canal Dehiscence Treated?

Basically, one can either avoid things that make you dizzy or cause hearing related symptoms, or you can get an operation.

Conservative approach: Dehiscence is not likely to resolve on it's own, so the real choice is between adjusting ones life, or having surgery done. SCD does not change very rapidly -- people often wait many years, or forever, before having surgery.

Patients with dehiscence may wish to avoid:

These are the things you might wish to do to mitigate symptoms:

1. Avoid loud nose -- for example, if you play a musical instrument, better find another hobby or get used to being dizzy.

2. Avoid pressure fluctuations between your ear and the rest of your body -- this isn't easy, as nearly any type of exertion has the potential for producing pressure fluctuation. It is not that there is a danger from this activity -- it just may give make you dizzy. Weight lifting, straining to do things, strenuous sexual activity - -these are all things that might cause trouble.

3. Avoid pressure fluctuations between your middle ear and external ear -- in other words, avoid situations where your ear might pop. Again, there is no real danger (other than that of falling or driving off the road), but you might get pretty dizzy.

On airplanes, our patients have indicated that ear plugs are often helpful in this situation also. The "ear plane" ear plugs are designed to reduce pressure fluctuation, and may be useful. If these are not possible or available, we suggest using a nasal decongestant at least one half hour prior to landing.

4. A ventilation tube may help. This positive effect is due to reduced movement of the tympanic membrane, ossicular chain, and stapes footplate, and therebye reduction of pressure on the middle ear. This is only useful for vertigo. It does not help hyperacusis or tinnitus.

5. Medications are not terribly useful, but those in the benzodiazepine family are sometimes helpful.

Case example: An otherwise healthy man developed positional vertigo. On examination he was noted to have both a positional nystagmus (downbeating) as well as pulse-synchronous nystagmus (see video above). A VEMP was abnormal and this was followed by a temporal-bone CT scan which documented clear superior canal dehiscence. As his symptoms were minor, he opted to do nothing.

Surgical treatment of Superior Canal Dehiscence (see next section on caution regarding otologic surgeons).

Vlastaros et al reviewed studies of SCD treatment (2009). The treatment of a dehiscence generally involves either closing the dehiscence (resurfacing, roofing or capping) or plugging of the canal. This is appropriate, for example, in superior canal dehiscence. Results are claimed to be good (Mikulec et al, 2005), although in a condition like this without clear cut objective endpoints, it might be difficult to be sure.

Plugging of the canal is the direct approach with respect to dizziness. It eliminates the stimulation of the superior canal by pressure, and also eliminates the normal function of the superior canal on one side. Plugging can be done through the mastoid or the middle fossa. As the dehiscence may include the entire top of the superior canal, one would wonder how the surgeon can successfully plug the canal through this route. Putting in a plug and then cementing it over makes a little more sense. While better exposure is attained through the middle fossa, it is riskier overall as it involves entering the cranial vault, retracting the temporal lobe and lifting up the dura. Middle fossa procedures are far more expensive as well. Van Hasendonck et al (2015) reported excellent results with transmastoid plugging (2015). For dehiscences that are large, it would seem a little difficult to cap this using a side opening such as is the case with the transmastoid approach.

Capping refers to closing of the opening made for the plugging with cement, or closing of the dehiscence with cement. This procedure is intermediate in effectiveness compared to plugging (Vlastarkos et al, 2009).   Plugging and capping would seem even more logical than plugging alone, although somewhat riskier.

The closing of the dehiscence using a bone or fibrous tissue graft (roofing, resurfacing) appears to be the riskier procedure -- sometimes dura is stuck to the membranes of the inner ear and an attempted repair results in deafness instead. Roofing or perhaps plugging and capping, however, would seem to be the logical approach to the hyperacusis of SCD, as one would think that the third window would remain open otherwise. "Boxcar" plugging -- putting a plug on both sides -- would seem to be a reasonable fix for hyperacusis. The outcome of using cartilage to "roof" SCD was reported by Afif et al (2019) in 10 patients, and the results were not encouraging. They wrote:

"However, four of 12 ears (33%) had a second (revision) surgery before achieving these results. Postoperatively, hearing through air and bone conduction tended to decrease at frequencies greater than 2500 Hz. The chance of avoiding a re-operation at 36 months (and up to 120 months) was estimated to be 57.1% (95% confidence interval [confidence interval]: 100%, 32.6%). The most common surgical complication was intraoperative cerebrospinal fluid (CSF) leak, encountered exclusively during dural elevation, seen in four of 12 ears (33%)."

In other words "redos" occured about 1/3 of the time, and spinal fluid leaks, also about 1/3 of the time. This may be related to the tegmen dehiscence commonly seen in patients with SCD (see elsewhere on this page).

Roofing (resurfacing) can also lead to recurrent symptoms due to shifting or resorption of the bone. For all of these these reasons, at this writing (2016), "plugging" with "capping" is favored (Vlastarkos et al, 2009). The best approach is usually the middle fossa. This is an evolving situation as of 2020, and the surgeon's experience with the technique must also be considered.

In our own practice, Chicago Dizziness and Hearing in Chicago Illinois, we have accumulated 100 SCD patients in our database over the last few years. We diagnose a new patient based on symptoms, cVEMP or oVEMP results followed by a temporal-bone CT scan (see comments). However, only about 1/5 patients are operated. Patients have simply generally not opted for surgery because of the risk of hearing loss, and also anxiety about the craniotomy (i.e. drilling of the skull) often recommended for the "roofing" or "capping" procedures. Patients more likely to opt for surgery are those with prominent auditory symptoms (e.g. hearing their voice in their head), or prominent dizziness (e.g. dizziness when doing something as simple as burping).

Patients who undergo surgery are unsteady for roughly 6 weeks after the repair (Janky et al, 2012). We have encountered a few patients who have had plugging done by very experienced surgeons, in which it appeared that a lot more damage was done than intended. It may be that plugging can sometimes lead to collateral damage and occlusion of more canals than anticipated. We have also encountered patients where roofing failed after a year or two -- this seems to be common. . This leads us to continue to be conservative regarding recommendations for surgical intervention.

Round window plugging (not recommended):

Round window plugging is a newly proposed surgery for SCD. The basic idea is that pressure changes in the inner ear can cause fluid shifts only if there there is a place for the fluid to go. There normally is a pressure relief part of the inner ear -- called the round window. When the stapes moves inward, the round window moves outward. When there is abnormal pressure presented to the opening in SCD, presumably the round window also moves back and forth and facilitates fluid movement. This is all quite logical. Several otolaryngologists have suggested that closing the round window, might be a successful treatment of SCD. The advantage of this method is that it is much less invasive than either the plugging or resurfacing approaches.

Recently, Dr. Silverstein and Van Ess reported a single case in which this approach was successful (Silverstein and Van Ess, 2009). The operative approach was do to a very thorough closure of the round window, using 3 layers. This is essentially what is done in perilymph fistula surgery, but using a more vigorous approach. It is too soon to know whether this method will be adopted. One wonders whether or not it might be reasonable to use an even more aggressive approach and "cement" the round window shut.

Biophysical modeling of SCD suggests that RW plugging should be ineffective.

We don't recommend round window plugging procedures.

Endoscopic surgery

We think it is not wise to seek SCD treatments that are "minimally invasive". Here we are explicitly talking about endoscopic approaches to SCD, usually guided with a navigation system. You want your surgeon to see what they are doing. Just because it can be done with an endoscope does not mean that it is as good as the standard approach. Whatever procedure you choose should have some good evidence behind it.

Beware of highly enthusiastic otologic surgeons.

New conditions can sometimes elicit entrepreneurial activity in surgeons. There currently is an oversupply of otologic surgeons in the United States. In the past, a somewhat similar condition to SCD (perilymph fistula), was associated with an immense surge in surgical operations, many later determined to be inappropriate. SCD, being a condition that can have slippery diagnostic criteria, could go this way. For example, is disturbing to see articles about SCD with obvious errors in their title. "Super semicircular canal Dehiscence" ?

Safety tips prior to planning SCD surgery:

Research:

While the diagnosis of SCD has become much easier in recent years, treatment has lagged behind. More work is needed to work out the best approach for treatment.

References: Follow this link for references in the SCD page system.