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Timothy
C. Hain, MD 
Page last modified:
March 29, 2009
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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 footplate (the "oval window"), #4 here, and just below, a small niche called the "round window". There can also be fistulae at other points, 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-- betwen 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.
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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.
The changes in air pressure that occur in the middle ear (for example, when
your ears "pop" in an airplane) normally do not affect your 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 the most 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, 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.
Ear surgery, particularly "stapes" surgery for otosclerosis (stapedectomy or stapedotomy), often creates a 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.
Some patients develop symptoms attributed to fistula following airplane descent.
Fistulas may be present from birth (usually in association with deafness) or may result from chronic ear infections called "cholesteatomas".
Fistulae are also created by a surgical procedure usually done for otosclerosis ("stapedectomy").
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.
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.
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 judgement, and these judgements 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 proceding 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.
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, will almost always be needed. A positive test is good grounds for surgical exploration. In window fistulae, very little nystagmus is produced, and a positive test may consist only of a slight nystagmus after pressurization. In superior canal dehiscence (SCD), a strong nystagmus may be produced. 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 per se. (Nadol 1974; Nadol 1977)
Audiometry and an "ENG" is nearly always necessary in order to establish the side, and to exclude other potential causes of symptoms. 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 mimick the conductive hearing loss pattern of otosclerosis (Mikulec et al, 2004).
An "ECOG", or electrocochleography may be of help also, although only in rare instances. The main role of ECOG is to diagnose Meniere's disease, which is a common alternative source of pressure sensitivity. ECOG is technically challenging and it may be difficult to locate a laboratory that does it well. An example of an ECOG in a patient with a confirmed fistula is shown in the case
An CT scan should generally be obtained. CTof 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.
MRI is not the best test for fistulae because it 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.
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) is the most convincing finding of fistula. Middle ear effusions may also be suggestive of fistula. Variants in the stapes structure are sometimes a clue that there is a congential fistula at the level of the oval window. Round window fistulae are generally unaccompanied by 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.
Recently 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. This test is not generally available however.
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, but appears promising.
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.
There are several tests for fistula which we do not think are necessary or reliable.
The pressure posturography test is one -- this test involves measuring postural sway after pressurization of the ear. This test appears to us to be prone to false positives.
The glycerin test has also been advocated for fistula (Leherer, 1980). We are concerned that this test is diagnosing Meniere's (hydrops) rather than fistula.
Conservative approach: In many cases, perhaps 90%, a window fistula fistula will heal itself if your activity is restricted. In such cases, strict bed rest is recommended for one week or more to give the fistula a chance to close. 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.
It is our opinion that frequently a 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 footplate.
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: 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 required.
For a window fistula surgery involves 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%, 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 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.
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. One conjecture is that it is due to autoimmune inner ear disease, another 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.
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 therebye 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.
Surgery may be recommended to close the leak. If hearing is good, or the diagnosis not that clear, most persons are advised to wait for 6 months before proceeding with a surgical exploration. The hope is that the body will repair the leak on its own. This is a reasonable hope, as most fistulas do indeed appear to close spontaneously. On the other hand, if in the judgement of your doctor, hearing appears to be at risk, then surgery may be advised more quickly.
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 nightlights 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.
Acknowledgement: Figures 1 and 2 are courtesy of Northwestern University.
| © Copyright May 22, 2009 , Timothy C. Hain, M.D. All rights reserved. Last saved on May 22, 2009 |
