Timothy C. Hain, MD Page last modified: March 20, 2017
Figure 1. Anatomy of the inner and middle ear. A fistula is an abnormal connection between the air-filled middle ear and the fluid filled inner ear. The two weakest points are membranes located at the stapes foot plate (the "oval window"), #4 here, and just below, a small niche called the "round window".
There can also be fistulae at other points, such as the superior semicircular canal, but they require erosion of bone.
A perilymph fistula, or PLF, is an abnormal opening in fluid filled inner ear. There are several possible places that there can be an opening-- between the the air-filled middle ear/mastoid sinus, into the intracranial cavity, or into other spaces in the temporal bone. In most instances it is a tear or defect in one or both of the small, thin membranes between the middle and inner ears. These membranes are called the oval window and the round window.
A dehiscence is similar to a fistula, but not as severe. Bone is missing, usually over the top (superior) semicircular canal, uncovering a membrane. This dehiscence makes the ear more sensitive to pressure and noise.
|Figure 2. Round window fistula. An opening in the round window allows perilymph to leak out into the middle ear. In this artist's depiction, for clarity, bone is not shown between the middle and inner ears. While it is difficult to be sure, it seems likely that in most cases there is only a small oozing of fluid between the perilymphatic space and the air-filled middle ear.|
PLF is a very rare condition compared to most other causes of dizziness and hearing loss. PLF surgery became immensely controversial in the 1980's due to widely varying patterns of practice, as exemplified by the practice of Dr. F.O. Black in Portland, as well as several other otologic physicians. (Black, 1992; Hornibrook, 2012) This has resulted in a peculiar situation with PLF in the USA in that many ENT doctors publically endorse the opinion that "Fistulae do not exist". As a PLF is a structural mechanical problem, this really is a "policy" statement of the physician saying that they just don't want to have anything to do with PLF. Somewhat like the "see no evil" monkey with the hands over the eyes. It is not a factual statement.
We have provided several case examples
The video above is of a fenstration.
The changes in air pressure that occur in the middle ear (for example, when your ears "pop" in an airplane) normally do not affect the inner ear. When a fistula is present, changes in middle ear pressure will directly affect the inner ear, stimulating the balance and/or hearing structures within and causing typical symptoms. There are a number of other conditions that can also cause pressure sensitivity such as Meniere's disease and vestibular fibrosis.
Supplemental material on the site DVD: Movie of nystagmus elicited by pressure
The symptoms of perilymph fistula may include dizziness, vertigo, imbalance, nausea, and vomiting. Usually however, patients report an unsteadiness which increases with activity and which is relieved by rest. Some people experience ringing or fullness in the ears, and many notice a hearing loss. Some people with fistulas find that their symptoms get worse with coughing, sneezing, or blowing their noses, as well as with exertion and activity. This sort of symptom goes under the general rubric of "Valsalva induced dizziness", and it can also be associated with other medical conditions in entirely different categories --for example, the Chiari malformation, and a heart condition called "IHSS". Returning to fistula, it is not unusual to notice that use of ones own voice or a musical instrument will cause dizziness (this is called the "Tullio's phenomenon").
Supplemental material on the site DVD: Movie of nystagmus elicited by sound
A closely related condition is "alternobaric vertigo" (Wicks, 1989). Here dizziness is associated with a difference in pressure between ears. This condition remains difficult to document. Some patients with sleep apnea on CPAP may have vertigo due to this mechanism. This page has more material about alternobaric vertigo.
Head trauma is a common cause of fistulas, usually involving a direct blow to the ear. Fistulas may also develop following rapid or profound changes in intracranial or atmospheric pressure, such as may occur with SCUBA diving (see case 2), or even just dives into a swimming pool (Klingmann et al, 2007; Rozsasi et al, 2003). The damage of pressure fluctuations probably arises via coupling through the middle ear as tympanic membrane perforations protect animals from barotrauma (Meller et al, 2003).
Forceful coughing, sneezing or straining as in lifting a heavy object may rarely cause a fistula. In pregnancy, collagen changes throughout the body, and fistulae may arise spontaneously or in association with delivery.
Children are likely more prone to develop fistulae because of more widely open pathways between the inner ear and the spinal fluid.
According to Remenschneider and asociates, other openings in the temporal bone that might present similarly to fistula include" skull base deficits through the tympanomeningeal fissure, the petromastoid canal, or an extension of the subarachnoid space into the fallopian canal. "(Remenschneider, Kozin, Curtin, & Santos, 2015) As some of these potential fistulae are only visualized at autopsy, it may not be possible to diagnose them no matter many MRI's or similar procedures that one undergoes.
Ear surgery, particularly "stapes" surgery for otosclerosis (stapedectomy or stapedotomy), often creates an oval window fistula. These are thought to generally heal spontaneously. If vertigo persists for a week following stapes surgery, exploration for fistula may be recommended. Vertigo may also occur in a delayed fashion -- months to years after stapes surgery. In these cases, exploration and patching of fistula has also been reported to be effective. (Albera, Canale et al. 2004). In some of these cases, the stapes prosthesis has become displaced into the oval window. This type of fistula is an "oval window" fistula, and may be an entirely different "animal" than round window fistulae.
Some patients develop symptoms attributed to fistula following airplane descent. This symptom would seem suspicious for a round window fistula.
We have encountered a patient with a probable fistula related to rapid removal of an music ear-phone from his ear, with suction and hypermobility to the TM.
Fistulas may be present from birth (usually in association with deafness) or may result from chronic ear infections called "cholesteatomas".
Another type of dehiscence was the intended result of an obsolete surgical procedure for otosclerosis called a "fenestration"). The purpose of fenestration is to improve hearing. In animals, fenestrations create pressure sensitivity (Hirvonen et al. 2001), and this is nearly always the case in people who have had this obsolete surgery. A movie of the nystagmus that is seen in Fenestration can be found here. It is easy to see, and horizontal in direction. There are very few people still alive who have had fenestration surgery, as it went out of style many years ago.
Fistulae are usually associated with some event, most commonly barotrauma or head injury (Lehrer et al, 1984), but rarely, fistulae occur spontaneously (Kohut, 1996).
Fistulas may occur in one or both ears, but bilateral fistulas are thought to be exceedingly rare (Sismanis et al, 1990).
A case example of a fistula is documented here (see links to other cases above).
There is considerable controversy about how to make the diagnosis of fistula. Meniere's disease, which is much more common than fistula, can have identical symptoms, including pressure sensitivity. For this reason, fistula diagnoses made in patients without barotrauma are easily questioned.
A second problem is that at the time of surgery, diagnosis is entirely based on the surgeon's judgment, and these judgments have been variable. In non-emergency cases, especially where there has been no barotrauma, we think it is prudent to get two opinions prior to proceeding with surgical remedies. Situations where the diagnosis of fistula is likely to be incorrect is that where fistula is diagnosed without a reasonable cause, and a diagnosis of bilateral fistula.
Our general impression is that oval window fistulae are often accompanied by hyperacusis and tinnitus. In our experience, oval window fistulae are largely caused by very loud noises. Round window fistulae are mainly characterized by exercise induced dizziness. In our experience, these types of fistulae are mainly induced by more conventional barotrauma, such as airplane flights or SCUBA diving.
Tests recommended when fistula is strongly suspected:
A fistula test , which entails making a sensitive recording of eye movements while pressurizing each ear canal with a rubber bulb, is occasionally helpful. A positive test is good grounds for surgical exploration but as a general rule, the test results in little or no nystagmus even in persons with surgically confirmed disease. In window fistulae, very little nystagmus is produced, and a positive test may consist only of a slight nystagmus after pressurization (Hain and Ostrowski, 1997). In superior canal dehiscence (SCD), a stronger nystagmus may be produced, but the Valsalva test is a better method of diagnosing SCD. Simple observation of the patient's eyes with appropriate equipment (such as VNG) may also provide the diagnosis of PLF, as in some cases, there is a pulse-synchronous oscillation (Rambold, 2001). Vestibulofibrosis causes much larger responses to pressure than fistulae. (Nadol 1974; Nadol 1977)
The Valsalva test changes pressure in perilymph, and thus might be positive in fistula. Our general impression is that there are small amounts of horizontal nystagmus in many persons with dizziness, lacking a diagnosis, and we think the noise level is very high. Nevertheless, sometimes the test can be positive. In persons with cholesteatoma or persons who have had the old fenestration surgery for otosclerosis, Valsalva may provoke a very strong nystagmus. The video below shows an example of a case that looks like SCD, but after conservative management the Valsalva vanished, leading the clinician to think that this patient had a fistula rather than SCD.
Supplemental material on the site DVD: Movie of positive then negative Valsalva (thanks to Dr. Dario Yacovino).
Audiometry and an "ENG" is nearly always necessary in order to establish the side, and to exclude other potential causes of symptoms. Rotatory chair can also be helpful. Audiometry may show sensorineural hearing reduction. In patients with SCD, audiometry may show bone conduction scores better than air (conductive hyperacusis). If there is a simultaneous sensorineural hearing loss in SCD, the overall picture may mimic the conductive hearing loss pattern of otosclerosis (Mikulec et al, 2004).
An "ECochG", or electrocochleography may be of help also, although only in rare instances. The main role of ECochG is to diagnose Meniere's disease, which is a common alternative source of pressure sensitivity. ECochG is technically challenging and it may be difficult to locate a laboratory that does it well. An example of an ECochG in a patient with a confirmed fistula is shown in the case
A temporal bone CT scan should not generally be obtained except in trauma cases or when there is good evidence for SCD (e.g. positive Valsalva).
CT of the temporal bone is very accurate in identifying canal fistulae (Fuse et al, 1996), although as there is really no other good way to identify canal fistulae, it is hard to be sure that it is picking them all up. Temporal bone CT is completely useless in identifying the most common types of fistulae involving the oval and round windows. In other words, a normal T-bone CT scan does not rule out fistula. As temporal bone CT scans entail considerable radiation, they should not be ordered lightly or by using a successive approximation to getting it right approach. In other words, it is generally not a good idea to have a CT scan of the temporal bone done at your community hospital.
There are often areas of thinning of the bone between the inner ear and other spaces in the head. There are often persons with a "high jugular bulb", persons who have had openings made into their inner ear during the course of surgery for miscellaneous ear conditions (e.g. cochlear implant, endolymphatic shunt), and just other areas where the bone is thin (e.g. dehiscence of the facial canal). These spaces presumably account for some types of pressure sensitivity. We do often see small amounts of horizontal nystagmus associated with the "Valsalva" test. We suspect that this small amount of nystagmus is due to these common internal plumbing quirks. Very little formal study has been made of these conditions.
MRIs are unlikely to be abnormal in fistulae.
Fistulae are just too small to be seen on MRI. Furthermore, MRI doesn't show the bone and resolution is not as good as CT scan. However, MRI is the best way of showing other possibly confounding problems such as acoustic tumors, cholesteatoma, or multiple sclerosis plaques. Acutely (i.e. right after the trauma), 3T MRI might be useful to identify air and blood in the inner ear, as it has been reported to be helpful with experiments in animals (Pierce et al, 2015). Recently 3T MRI's with double-dose contrast are used to identify Meniere's. Whether or not these will work for PLF as well as uncertain, as we lack a gold-standard for diagnosis. In other words, even if a 3T MRI shows hydrops, aside from some investigational tests (such as the CTP test), we have no good way to confirm that the fistula exists even at surgery.
A CSF leak can occur from the ear as well as from other places in the head. CSF leaks mainly are a consequence of head injury or surgery (for example, they are fairly common after acoustic neuroma surgery). CSF leaks in the ear can be documented by CT cisternography with a spinal injection of a contrast material. The head is tilted down for 3 minutes with the patient prone, and a CT scan is done with high resolution cuts (spiral), in the coronal plane immediately after the prone positioning, to cover the frontal sinus through the mastoid sinus region.
Air in the labyrinth (pneumolabyrinth) seen on a scan is the most convincing finding of fistula. It is very rare however.
Practically, this only occurs after trauma (e.g. temporal bone fracture, or mastoid surgery -- generally for cholesteatoma). Middle ear effusions may also be suggestive of fistula. Variants in the stapes structure are sometimes a clue that there is a congenital fistula of the oval window. Round window fistulae are generally unaccompanied by temporal bone CT abnormalities, although an effusion would seem to be possible in this situation. Other congenital abnormalities of the cochlea, vestibule, and vestibular aqueduct may also be documented by CT of the temporal bone (Swartz and Harnsberger, 1998). Unfortunately, these procedures are not 100% accurate for all types of fistulae, and in some cases, only direct inspection of the inner ear will confirm or rule/out a possible fistula.
Sound evoked vestibulocollic evoked potentials have been described as useful in diagnosing Tullio's phenomenon (sound induced dizziness) from superior canal dehiscence (Brantberg et al, 1999; Watson et al, 2000). These are also called "VEMP" for vestibular evoked myogenic potential. The side with the larger VEMP or lower threshold is the abnormal side. The quality of this test varies remarkably.
VEMPS are mainly useful in distinguishing PLF's from SCD. VEMP should be positive on the symptomatic side in SCD. They should be normal or reduced in PLF.
This test was described very recently by Halmagyi and others (2003). Event triggered averaging is used to detect electro-oculographic responses to loud clicks -- intensities ranging from 80 to 110 DB. 128 clicks were delivered at a rate of 5/s from 60 to 110 dB, in 10 dB steps. Normal subjects have no or a very low amplitude response of < 0.25 deg at 110. The latency was 8 msec. This test is not generally available.
A method of documenting a fistula without operation is to inject a fluorescent material that gets into perilymph, and observe it with an endoscope (Kleeman et al, 2001). There are several difficulties. First, getting the dye into the perilymph may be problematic. While perilymph is connected to some extent to CSF, the connection is not as open in some people as in others. Injection of dye into other fluids, such as intravenously, leaves open the question as to whether the fluid seen that fluoresces is serum or perilymph. This procedure is not widely available.
The "cochlin-tomoprotein test", or CTP, has been reported as being sensitive to PLF, done during surgery or with middle ear lavage. (Ikezono et al, 2011; Komori et al, 2016). Middle ear lavage is modestly invasive, involving putting in saline and then washing it out and sending it for assay. This is a promising test for PLF, that might make it much easier to diagnose them.
There are several tests for fistula which we do not think are necessary or reliable.
The algorithm sheet below illustrates how we (Chicago Dizziness and Hearing) manage potential fistulas:
Conservative treatment approach to perilymph fistula:
In many cases, perhaps 90%, a window fistula fistula will heal itself if activity is restricted. In the past, strict bedrest was suggested. This is no longer thought necessary, but avoidance of activities where there is a possibility of creating high pressure (e.g. airplane travel, Scuba diving, power lifting, horn playing, etc) is usually advised.
It is usual to wait 6 months before embarking on surgical repair, given that hearing function is reasonable and is stable or improving.
With respect to air travel, while it is certainly safest to avoid air travel altogether, in some instances it may be unavoidable. In this case, we suggest using a nasal decongestant at least one half hour prior to landing. Some of our patients have indicated that ear plugs are helpful in this situation also. The "ear plane" ear plugs are designed to reduce pressure fluctuation, and may be useful. Ventilation tubes are another option (see next).
It is our opinion and experience that frequently a placement of an ear ventilation tube will help. The rationale for this is that the ill effects of barotrauma appear to require an intact tympanic membrane (Meller et al, 2003). We conjecture that this positive effect is due to reduced movement of the tympanic membrane, ossicular chain, and stapes foot plate. There are two routes for pressure to affect a PLF -- "implosive" and "explosive" -- from the inside or outside (Goodhill, 1981). A PE tube only blocks the "implosive" mechanism. Pressure can still fluctuate in the inner ear, such as due to straining.
Once a tube has been placed, airplane flight should be without problem as there is no longer a mechanism for pressure to fluctuate in the middle ear as a result of the airplane flight.
Sometimes there are suggestions (generally from reluctant otologic surgeons) that putting a tube into the middle ear, in an individual with a fistula, will provide a portal for bacterial infection and result in a labyrinthitis. While theoretically possible, we think that this logic is unlikely to be generally valid, as the middle ear communicates very freely with the nasal cavity through the eustachian tube. If this logic was valid, persons with PLF should be developing infections with or without a tube. This is not a clinical problem, and we have never encountered anyone in our practice who developed labyrinthitis after insertion of a ventilation tube for fistula.
Case example: a woman in her 30's began to complain of dizziness during the second trimester of pregnancy. She complained of spinning, fainting, and nausea. Fistula testing induced nausea. A VEMP test revealed a much larger response on the right side. The Tullio test elicited upbeating nystagmus on the right side only. A ventilation tube was recommended on the right. After the tube was placed, symptoms were "75% better". However, it plugged up and symptoms returned after that. A bigger tube was placed a few months later, and symptoms again resolved. Nevertheless, surgery was recommended. On surgery there was an active round window fistula. This was patched, and the patient remained much better at last followup (2 months later).
The case example also illustrates a person who responded to a tube.
Surgery for perilymph fistula: Exploratory Tympanotomy:
If you have a canal fistula, if your symptoms are significant and have not responded to the conservative approach outlined above, or if you have a progressive hearing loss, surgical repair of the fistula may be recommended. The frequency that this surgery is recommended has fluctuated dramatically. At the moment (2010), this surgery is used as a last resort. In the past, this surgery was very prevalent.
In general, PLF surgery should not proceed until superior canal dehiscence (SCD) has been ruled out. PLF surgery will generally not help persons who have SCD.
For a window fistula, surgery involves opening up the middle ear, and placing a soft-tissue graft over the fistula defect in the oval and/or round window. Otic capsule fistulae do not, in general, heal by themselves.
Unfortunately, in our opinion anyway, surgical procedures are not well worked out. Cure rates (with respect to vertigo) are reported to be about 60%. For example Meldrum and Prinsley (2016) reported that the vertigo symptom scale impored greatly just after surgery. As there was no "sham" surgery, this study cannot be controlled.
But in our experience, we think that failures occur at least 2/3 of the time, if one looks at patients one year out. Patients often seem to be "better" for several months or a year. Patients are often reoperated when it is decided that the graft has failed. Some otologic surgeons operate the same patient many times (e.g. 14 times in one publicized case). In our opinion, one or two retries should be the limit (i.e. the "three strikes and you are out policy).
We think that the surgery doesn't work very well because it is not aggressive enough. We are dubious that placement of some loose soft tissue over a fistula is a reliable method of closing off a leak. It would seem to us that this is similar to using putty to close a leak in your bathtub. It might work for a while, but it is likely to eventually fail.
It is not unusual for a person following a PLF repair to develop hearing symptoms on the other side. The cause of this is unclear. The most reasonable conjecture is that it is due to autoimmune inner ear disease, Another conjecture that it is due to CSF leak, and a third is that the original diagnosis was incorrect and the patient actually had Meniere's disease.
The surgical treatment outlined above is not always effective, and on many occasions, nothing works. Patients fail tubes, and also fail exploratory tympanotomy, or get worse again a few weeks after the exploratory surgery with soft tissue plug.
We have now had experience with two cases of middle aged patients, who were disabled, and who underwent vestibular nerve section, with very good results. Both have returned to work ! This is a gigantic improvement in quality of life for these patients. The recovery trajectory in these cases is slow, as would be expected from VNS surgery. VNS is truly a last resort procedure. We think it best to avoid unless the disability is severe and the side of the PLF is very clear. This usually means that the PLF is post-traumatic. We think it is very reasonable to consider a VNS for someone who has been disabled for a year or more, with clear evidence that there is a fistula, and who would be otherwise "employable" -- in other words -- has no disabling conditions beyond the PLF.
In most instances, shunt of the endolymphatic sac or spinal fluid pathways (e.g. lumbar shunts) are not appropriate treatments for fistulae. When done, the rationale is to reduce CSF and perilymph pressure, possibly allowing the ear to heal. A recent paper by Weber and others suggests that fistula surgery does not worsen things in children (Weber et al, 2003)
There have been sporadic reports of endoscope-guided fistula repair (Karhuketo and Puhakka, 2001). While one must admire the skill of the surgeons in these cases, in our opinion, this approach seems ill-suited to general use as fistula diagnosis and repair is difficult even when using a wider exposure.
There is considerable variability among otologic surgeons regarding their diagnosis and surgical management of fistulae (Hughes, 1990). We recommend getting a second opinion when fistula surgery is suggested.
Medications: For persons with plugged up eustachian tubes (such as due to a cold or allergy), decongestants, allergy medication, and ventilating tubes may be of use.
Medications in the minor tranquilizer family such as diazepam ("Valium"), klonazepam and lorazepam help some individuals. "Antivert" and "phenergan" are also medications which some find helpful.
A trial of bed rest for 1-2 weeks may be recommended. In this situation, one attempts to minimize pressure changes in the ear, hoping that scar tissue will seal the leak. For persons with superior canal dehiscence, no treatment will close the bone, so the only reasonable options are avoidance and surgery.
Ear plugs are sometimes helpful for those who develop dizziness related to loud noise or rapid fluctuation in air pressure. Custom ear plugs, such as the ER/15 which seal the affected ear seem to work the best. A baffled ear plug called the "Ear Plane" may be helpful, is available over the counter, and is much cheaper than the ER/15.
You may find that modifications in your daily activities will be necessary so that you can cope with your dizziness. For example, you may need to have someone shop for you for a while if going up and down supermarket aisles tends to increase your symptoms.
You should take special precautions in situations where clear, normal vision is not available to you. For example, avoid trying to walk through dark rooms and hallways; keep lights or night-lights on at all times. Don't drive your car at night or during stormy weather when visibility is poor.
Make sure your hallways at home are uncluttered and free of obstructions. Most important, do not place yourself in a situation where you might lose your balance and be at risk for a fall and serious injury; stay off of chairs, stools, ladders, roofs, etc. If your balance continues to be a serious problem, you may need to consider using a cane or walker for added safety.
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