Perilymphatic Fistula

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Chapter 27 Perilymphatic Fistula

George T. Singleton, Teresa M. Lo

Perilymphatic fistula (PLF) is a condition resulting from an abnormal connection between inner ear perilymph and the middle ear space. Its etiology has been described as being congenital, acquired, or idiopathic. Congenital middle or inner ear defects are believed to play a role in the development of PLF. PLFs exist in association with stapedectomies and other invasive procedures of the cochlea. Likewise, severe head injury, abdominal blows, and rapid shifts in environmental pressure are accepted causes of PLF. Acute and chronic mastoiditis with erosion into the labyrinth, and chronic granulomatous diseases, such as syphilis and tuberculosis, have also led to the development of PLF. In the absence of a clear antecedent traumatic event, idiopathic PLF remains a diagnostic and treatment challenge.

Iatrogenic poststapedectomy PLFs were first described in the mid-1960s. Steffen and colleagues1 reported findings of gross perilymph flow at the oval window in poststapedectomy patients with hearing loss, tinnitus, and vertigo. Fee2 reported three patients who presented with vertigo, fluctuating hearing loss, and tinnitus, who also had known or suspected recent head trauma. Intraoperative findings showed perilymph leak at the oval window. Repair of the leak resulted in significant improvement in symptoms.

In 1971, Goodhill3 coined the terms implosive (Valsalva-induced) and explosive (increased intracranial pressure) to describe pressure changes that can result in PLF. In reference to implosive, Goodhill stated that increased negative pressure from the tubotympanic region can be directed via the ossicles to the perilymphatic space. These external forces can result in a tear in the oval or round window membranes, driving air into the inner ear and displacing perilymph into the middle ear. The explosive route results from increased intracranial pressure possibly secondary to a severe blow to the head or abdomen. Increased intra-abdominal pressure transmits via the vertebral veins to increase the cerebrospinal pressure with resultant increase in intracranial pressure. Increased intracranial pressure can be transmitted to the inner ear via the cochlear aqueduct or internal auditory canal, potentially causing subsequent rupture, from inside out, of the oval or round window, or both.3

Homeostasis of the pressure differentials between endolymph and perilymph is maintained by patency of the endolymphatic duct and sac. If this pressure/volume balance is disrupted, as might occur in the case of a PLF, endolymphatic hydrops may result in damage to the hearing apparatus. Animal models with experimental PLF have shown hydrops, usually resolving within 3 weeks.4,5 The cochlear aqueduct provides an important communication between the subarachnoid and perilymphatic space. The only outlet from increased intracochlear pressure is via a tear of the oval or round window membranes. Tears of the oval window annular ligament occur most frequently anteroinferiorly, rarely superiorly around the stapes footplate. The round window membrane tears less frequently.6 Tears of the round window membrane have occurred when its position was 45 degrees to the promontory, and there was little or no overhanging promontory, allowing direct visualization of the round window membrane transtympanically (Fig. 27-1B).7,8

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FIGURE 27-1 A, Right middle ear: surgeon’s view with tympanomeatal flap and drum folded forward. Sites of oval window fistula are numbered in order of occurrence (1 and 2 most common). B, Abnormal round window (RW) membrane at 45 degree angle to promontory and no overhanging lip. C, Normal RW membrane hidden from view in depths of niche, with lip of bone overhang. Mucosal folds frequently appear to seal niche partially, with a hole in the center. EAC, external auditory canal; PLF, perilymphatic fistula; TM, tympanic membrane.

The cribriform areas at the depths of the internal auditory canal are another area of potential transmission of increased cerebrospinal fluid pressure to the perilymphatic space. Rarely, these sites of communication are widely open, allowing direct connection of cerebrospinal fluid to perilymph, such as in Mondini’s malformation. Cerebrospinal fluid gushers can result in these patients after any invasive operative procedure of the cochlea.

Microfissures of the otic capsule in the area of the oval window, round window niche, and posterior canal ampulla have been previously theorized to lead to PLF. This theory was based on temporal bone studies by Kohut and colleagues,9 who noted “loose fibrous composition in the fissula ante fenestra” in patients with PLF. A follow-up study by El Shazly and Linthicum10 showed that these microfissures are commonly present in temporal bones. No association between the presence of microfissures and sudden sensorineural hearing loss was found, and no evidence of PLF was noted.

Animal studies have tried to examine the pathophysiologic mechanism contributing to the hearing loss noted in PLF patients. Weisskopf and colleagues11 generated perforations in the round window membrane of guinea pigs. The resultant hearing loss recovered with time, and the authors concluded that perforations alone did not explain the degree of hearing loss present in PLF. Some research has shown pneumolabyrinth to cause sizable auditory threshold shifts, with removal of the air bubble from the cochlea resulting in resolution of hearing loss.12

Early stapedectomy procedures were more likely to result in PLF than methods practiced today. The entire stapes and footplate were often removed and replaced with a pointed polyethylene strut or wire loop prosthesis placed atop a thin piece of absorbable gelatin sponge (Gelfoam) or tissue seal. The wire could migrate, and the thin tissue membrane could rupture, both increasing chances of PLF. The current small fenestra, small piston, tissue seal techniques have dramatically reduced the incidence of PLF.13–17 Lesinski18 prospectively reviewed 19 cases of revision stapedectomy performed for symptoms of possible oval window fistula. The 14 of 19 patients who were noted to have an active PLF had undergone prior complete stapedectomy with migration of the prosthesis eccentrically, close to the edge of the oval window.

Invasive procedures of the stapes footplate, including the Fick or Cody tack procedure for Meniere’s disease (sacculotomy) were ultimately abandoned because of the high incidence of sensorineural hearing loss. Later exploration of many of these ears revealed a persistent PLF.19 Likewise, the 20% sensorineural hearing loss associated with cochleostomy or cochleosacculotomy, as it was originally described, was probably related to a persistent round window PLF.19

As awareness of PLFs increased, the number of diagnoses and surgical explorations for PLF did as well. Lower rates of positive exploration and of successful repair were being reported, however. In many cases of re-exploration for possible persistent PLF, prior operative records had described the presence of a hole in the round window membrane. Re-exploration findings showed a normal-appearing round window membrane deep in the niche (Fig. 27-1C). It is likely the prior surgeon had sealed the mucosal folds surrounding the round window niche.

Similarities in symptoms may have led to the misdiagnosis of Meniere’s disease or superior semicircular canal dehiscence as PLF. Attempts at identifying predictive tests, such as glycerin challenge testing or electrocochleography, to differentiate Meniere’s disease from PLF have been unsuccessful.20–23 The classic symptoms of Meniere’s disease are episodic vertigo, fluctuant hearing loss, tinnitus, and, in 80%, a sense of fullness in the involved ear. Patching of windows in these cases with no visible leak would give the same result as allowing time to pass. In Minor’s24 review of 65 patients with superior semicircular canal dehiscence, 54 (83%) had vestibular symptoms elicited by loud sounds, and 44 (67%) had pressure-induced (sneezing, coughing, and straining) symptoms. In addition, a 10 dB or greater conductive hearing loss was present in 70%. (See Chapter 42 for further discussion.)

Previous studies of children with sensorineural hearing loss of unknown etiology showed a rate of 6% to 16% positive PLFs on exploration.25–27 In the largest prospective series by Reilly25 of 244 children with sensorineural hearing loss, 17% underwent exploration, all of whom had prior abnormal computed tomography (CT) scan findings. Of the children who underwent exploration, 26% had active congenital PLF. A more recently published retrospective series reported 64% of ears with suspected PLF to have a leak confirmed visually.28 Middle ear malformations have been noted in 81% of PLF patients at the time of surgery, most commonly an anomalous stapes.29

PATIENT SELECTION

Patient presentation is variable with PLF. Symptoms have been reported to be present from days to decades. The typical patient with a PLF presents with a sudden onset of hearing loss or mild vertigo or dysequilibrium, or both hearing loss and vertigo, associated with a traumatic event. Trauma includes invasive middle or inner ear surgical procedures, abdominal or head blows, blast injuries, or severe changes in environmental pressure, particularly in the presence of an upper respiratory infection or an acute allergic attack. In some series, one third to one half of patients recall no potential triggering event.30,31

In cases of surgically proven PLF, patients present with some degree of vestibular and auditory disturbances. Patients reported vestibular complaints including episodic or positional vertigo, dysequilibrium, lightheadedness, and motion intolerance 46% to 91% of the time.31–35 A chief complaint of hearing loss was present in 28% to 93% of patients.31–35 Although only 28% reported noting hearing loss in the Iowa series, 54% had abnormal audiograms.32 Hearing losses are most commonly reported to be sudden or rapidly progressive; however, in some series they were also noted to be fluctuant, raising debate as to whether the disease was actually Meniere’s disease.

Tinnitus has been reported as a chief complaint in 25% to 76% of patients with PLFs, always in combination with vestibular or auditory symptoms or both.31,32,35,36 In some series, no patients reported tinnitus as a presenting symptom.34

PREOPERATIVE EVALUATION

Vestibular signs are commonly present in PLF. Positional nystagmus may have a very short or no latency and relatively long duration. Repeated testing shows nystagmus with minimal or no fatigue, no direction reversal when changing from inducing position to sitting position, and less violent than seen with benign paroxysmal positional vertigo. The nystagmus is rarely rotatory. From most to least frequent, the nystagmus may be horizontal, diagonal, or vertical.27,37 The direction of the nystagmus is of no diagnostic value in determining which ear is involved.

Hearing loss is typically sensorineural, without a specific pattern. Conductive hearing loss is rarely observed. This hearing loss has been attributed to a slipped stapes prosthesis or possible presence of air within the labyrinth. The speech reception threshold is usually worse than anticipated from the pure tone average, and the discrimination score is usually lower than expected.38

Most series report usage of a fistula test by applying positive or negative pressure to an intact tympanic membrane with a pneumatic otoscope. Resultant nystagmus indicates a positive test and is present only about 25% of the time.45 A sensation of dysequilibrium suggests a positive test. Modifications, such as administration of the test with the patient standing and eyes closed30,39 or on a moving posture platform (platform fistula test), have been used to try to improve test sensitivity. Electronystagmography has also been performed concurrently. Several studies noted no significant difference with electronystagmography-enhanced fistula testing.34,41 High positive exploration rates have been reported in cases using the moving platform fistula test; however, these findings have not been supported by others.42,43

The Quix test involves having the patient stand erect with feet together, eyes closed, and arms outstretched. The examiner looks for deviation of the arms to the side of the lesion. The result is positive in only about 20% of cases.44

The eyes-closed-turning test has shown high sensitivity and specificity for PLF. It is performed by having the patient walk in a straight line with eyes closed. The examiner taps the subject’s shoulder, indicating to the patient to turn 180 degrees either right or left and stop in a position of attention with the eyes still closed (Fig. 27-2). A positive test is readily recognized by the patient’s swaying or having a tendency to lose balance when he or she has turned to the side of the lesion.45,46

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FIGURE 27-2 Eyes-closed-turning test. The patient walks with eyes closed, turns quickly right or left, then stops in position of attention with eyes still closed. A positive test result consists of staggering or swaying on turning to the involved side.

Electrocochleography has been used in attempts at improving diagnostic ability; however, results have shown limited clinical utility. Because of pathophysiologic overlap with other conditions such as Meniere’s disease, electrocochleography lacks sensitivity in identifying PLF.21,47

Radiographic assessment has not proven to be helpful in diagnosis of PLF because adequate evaluation of the oval and round window regions is difficult. In patients with confirmed PLF, congenital anomalies of the middle or inner ear or both were able to be visualized on high-resolution CT only 50% of the time.48

Rigid and flexible endoscopy via myringotomy have been proposed to help in middle ear visualization before definitive exploration. Some authors report adequate visualization, whereas others have reported limited view of the round and oval window niches, often with mucosal adhesions obscuring the site.49–51 Negative findings were not followed up with formal exploration.

Visualization of clear fluid in the middle ear does not confirm presence of PLF. Injected local anesthetic pooling in the middle ear can confuse the picture. The volume of perilymph has been reported to be approximately 75 μL; visualization of such small volume can be difficult. Large fluid volume pooling in the middle ear raises the question of cerebrospinal fluid leak. Provocative testing, such as Trendelenburg position, Valsalva maneuver, and jugular vein compression, and application of mineral oil in the middle ear have been attempted; the usefulness of these techniques has not been proven.52,53

Numerous objective assays have been attempted to improve identification of perilymph in the middle ear. Technetium-labeled albumin was tried early on, but the albumin did not migrate into the perilymph. Intrathecal and intravenous fluorescein administration has not been shown to be useful given the potential neurologic complications and uncertainty of accurate perilymph labeling.54,55 Glucose measurement of approximately 100 mg/dL of middle ear fluid, in the absence of blood product, has been used to help identify perilymph. Silverstein56 reported on the use of indicator paper to identify protein concentration in middle ear fluid. The color change and correlation with known differing protein concentrations in perilymph, cerebrospinal fluid, and serum were used to determine presence of perilymph. Possible errors in identification could be due to local anesthetic dilution. Protein markers such as β2-transferrin57,58 and beta-trace protein,59 which are present in cerebrospinal fluid and perilymph, have also been investigated as possible diagnostic markers for PLF. Measurements of these markers in perilymph have been unreliable, owing to difficulty with collection methods and small sample volumes. In addition, processing time precludes use of these assays for intraoperative decision making.

PATIENT COUNSELING

Most clinicians consider PLF to be a surgically correctable problem, particularly in cases in which antecedent surgery or trauma is present. Conservative or medical therapy has been advocated in patients seen soon after presentation with stable hearing. Recommendations are for bed rest for 5 to 7 days, elevation of the head, stool softeners, avoidance of Valsalva maneuvers, and serial audiometric evaluation. If hearing deteriorates, or the vestibular symptoms fail to abate, surgical intervention should be considered. If hearing loss is present, waiting more than 2 weeks from the onset of PLF significantly reduces the likelihood of improving hearing with operative intervention.

The goal of surgical intervention is to cover the leak with autologous tissue, such as fat, fascia, perichondrium, or areolar tissue. As previously discussed, however, identification of the fistula site can be a challenge.

Patients are recommended to undergo the procedure under local anesthesia with monitored anesthetic care in an ambulatory surgical setting. If there are concerns of claustrophobia, anxiety, or difficulty with positioning, a general anesthetic should be considered. No preoperative laboratory work or testing is required for healthy young adults; older patients and patients with systemic diseases should undergo testing as relevant to their respective medical comorbidities. Patients are advised to discontinue aspirin and nonsteroidal analgesic therapy 10 to 14 days before surgery. For anticoagulants such as warfarin or clopidogrel, clearance should be obtained from the prescribing physician to discontinue in an appropriate time frame.

Patients are instructed to wash their hair the night before surgery. Patients are counseled regarding possibility of a small postauricular or tragal incision if graft material needs to be harvested. If a leak is found intraoperatively, patients require bed rest for 5 days with bathroom privileges, and restrictions of no heavy lifting, straining, and sexual activity until at least 2 weeks postoperatively.

SURGICAL PROCEDURE

Preoperative Preparation

Patients have an intravenous line started in the preoperative holding area. They are asked to go to the bathroom immediately before coming back to the operative suite. The operative ear is confirmed with the patient and marked accordingly. If unusually nervous, patients may receive a small amount of midazolam before coming back to the operative suite. Dexamethasone (Decadron) can be administered at the beginning of the case to help alleviate potential postoperative nausea. No routine systemic antibiotic therapy is administered.

Patients are placed backward on a standard operating table, allowing room for the surgeon’s legs. The anesthesiologist places the electrocardiographic monitors and pulse oximetry on the patient. An automatic blood pressure cuff is placed on the arm opposite the operative ear to prevent accidental movement of the surgeon’s arm during insufflation. Any loose hair from around the ear is taped back with wide paper adhesive tape. No shaving is usually necessary. The patient’s head is positioned with the nonoperative ear turned toward the shoulder and gently secured with paper adhesive tape, followed by silk adhesive tape for reinforcement. A sedative-hypnotic agent is administered by the anesthesiologist (e.g., methohexital, propofol). Supplemental oxygen is administered via nasal cannula or mask as needed.

Local anesthetic (1% lidocaine with 1:100,000 epinephrine) is administered via a ring block completely around the operative ear. The operating microscope is brought into position, the ear canal is cleaned, and four-quadrant injections are performed. Care is taken to produce no excessive injection or blistering of the ear canal skin. The inferior injection is placed posteroinferiorly at the bony cartilaginous junction, with care taken to place the bevel of the needle against bone and under the periosteum. Administering the injection is a slow, deliberate process, with the surgeon watching carefully for blanching, and ensuring that the fluid diffuses all the way to the annulus inferiorly. All desquamated epithelium from the ear canal is removed with a small suction.

The operative microscope and all instrumentation are removed from the patient to allow for sterile preparation of the patient and operative site. An “ether screen” is secured to the table, opposite the operative site, to keep the drapes from resting on the patient’s face. The operative site is painted with povidone-iodine (Betadine) solution and blotted from around the ear. A 3M adhesive drape with a 2 inch hole is placed over the ear. The drape is precut so that it does not fall over the patient’s mouth and nose. A disposable, lint-free, paper ear-draping pack is used to cover the patient and the remainder of the operative field. A small hole is cut near the patient’s upper face so that he or she can see the anesthesiologist’s or nurse’s face.

Surgical Instruments

A standard tympanostomy setup is used. Disposable straight and angled Beaver ear blades are used for flap incisions. A skeeter microdrill with 1 to 1.4 mm diamond burrs is used for removing the scutum. A sharp 0.5 mm right angle pick is altered slightly by bending its shaft 20 degrees, 2 inches from the end to allow better visualization of the tip. A straight pick with an angled handle is used for work around the stapes footplate and to place grafts.

Surgical Technique

The sterile-draped operative microscope is brought into the field. Ear canal injections are repeated as necessary. The ear canal is copiously irrigated with normal saline to remove povidone-iodine.

The inferior incision is made first by use of the No. 1 straight Beaver blade. A cut is made from the 6 o’clock position and is angled to about 1 cm lateral to the annular ring on the posterior ear canal. The No. 2 angled Beaver blade is used to make an incision superiorly from 2 mm lateral to the short process of the malleus to join the tip of the other incision in the posterior ear canal. A duckbill elevator is used to elevate the skin of the posterior canal down to the annulus. A House No. 2 knife can be used to elevate fibers adherent in the suture line. Hemostasis must be achieved before entering the middle ear and can be completed by using a 20 gauge suction placed on the bleeder and low-setting cautery.

The middle ear is opened at the notch of Rivinus by use of a Rosen needle. The chorda tympani nerve is identified, and the beginning of the annular ring is raised with the Rosen needle or drum elevator. The chorda tympani is gingerly dissected free of the tympanic membrane, and the posterior half of the tympanic membrane and ear canal flap are folded forward so that the middle ear may be inspected (see Fig. 27-1A).

Frequently, clear fluid is seen in the oval window recess and in the round window niche. The fluid is usually local anesthetic that has seeped into the middle ear space, and a 24 gauge suction should be used to remove it. The patient is asked to perform a Valsalva maneuver to observe if fluid reaccumulates. If the fluid reaccumulates, and it is unclear whether a fistula is present, the fluid may be quickly checked to try to determine if it is perilymph. A small piece of Gelfoam can be placed on an angled straight pick to soak up the solution, taking care to avoid any blood product. The Gelfoam is placed on a Clinistrip for glucose testing. If the reading is 100 mg/dL, this is most consistent with perilymph. Another method is to measure protein concentration in the perilymph using the Xomed Treace protein-measuring kit. A micropipette is used to obtain fluid, which is placed on indicator paper. The color change is compared with a standard, which can help to identify the presence of perilymph.

No bony work or mucosal manipulation (other than initial suctioning of the middle ear) has been performed to this point. The scutum has been left intact, and the round window niche and lip of the promontory have not been disturbed.

If the round window membrane is immediately visible when the middle ear is opened—that is, at about a 45 degree angle to the plane of the promontory—the surgeon should become suspicious of a probable PLF in the round window membrane. After checking for the recurrence of fluid in these recesses, the surgeon removes the scutum and gets complete exposure of the oval window area. If no fluid was noted in the oval window region earlier with Valsalva maneuver, a straight pick can be placed on the lenticular process of the incus and pressed gently, looking for accumulation of fluid around the annular ligament or in the round window niche. If no fluid accumulates in either place with Valsalva maneuver and pressure on the stapes, no repair is performed. We believe there is a risk for creating some degree of conductive hearing loss and the possibility of injuring the inner ear by patching the oval or round window with no PLF. Other authors advocate patching the oval and round windows without obvious leak present.

Most PLFs at the oval window are located directly anterior to the anterior crus or immediately below it; a few are superior to the anterior crus (Fig. 27-3). Generally, there is good visualization of this region. Leaks in this area are best repaired by teasing away the surface mucosa either with a straight pick or with a small right angle pick. A graft of adventitia is obtained from over the temporalis fascia. This graft is compressed and cut into the shape of a small set of trousers, approximately 3 mm long and 1.5 mm wide, and a 2 mm slit is created up the middle to form the pants’ legs (see Fig. 27-3A). The graft is draped around the anterior crus and packed in place with Gelfoam (see Fig. 27-3B) soaked in Ringer solution. Some authors have advocated adding fibrin glue to the graft for increased stability. Gelfoam is packed to the level of the tympanic membrane followed by a sheet of absorbable gelatin film (Gelfilm) to prevent adhesions to the tympanic membrane.

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FIGURE 27-3 Details of oval window fistula sites in order of occurrence. Sites are in the annular ligament site. A, Pants graft of areolar tissue 3 × 1.5 mm with legs 2 mm long. B, Pants graft in place over denuded mucosa around perilymphatic fistula (PLF).

FIGURE 27-4. Congenital defects in posterior footplate.

If there is a congenital defect of the stapes footplate, it may be present in the middle of the footplate, or may incorporate the entire posterior half of the footplate (Fig. 27-4). In these cases, the mucosa must be denuded completely around the footplate. With larger perforations, perichondrium from the tragus is used because it is thicker and easier to handle to effect a seal. The area between the crura is packed full with Gelfoam to hold the graft in place.

If there is a round window PLF, the membrane is in clear sight with no overhang of the round window niche. Generally, the tear is readily visible around the annular ring of the membrane. Occasionally, it is in the center, particularly if the injury was created by a myringotomy knife or foreign body. If the fistula is less than 2 weeks old, a fibrin clot or granulation tissue may be seen around the leak. The area surrounding the perforation is roughened with a small right angle pick. A thicker graft of tragal perichondrium is used. The graft is held in position by packing with Gelfoam and placement of Gelfilm to prevent formation of adhesive bands. The tympanic membrane is replaced to its native position, and the skin flap in the ear canal is laid flat. Gelfoam moistened in antibiotic solution is placed over the tympanic membrane and skin flap to fill the ear canal, and a cotton ball is placed. The postauricular and tragal graft harvest sites are closed with absorbable sutures.

Dressing and Postoperative Care

Patients are returned to the recovery room in a semisitting position. If a PLF was identified, patients are counseled regarding the need for bed rest for 5 days with bathroom privileges only. They are to sleep either in a recliner chair or in a bed with the head elevated 4 to 6 inches. Patients are advised that when they rise from bed, they are to roll on to their side and push up with their arms to avoid tensing abdominal musculature. They are to use ototopical antibiotics, 5 drops twice daily, until their postoperative appointment in 2 weeks. The cotton ball should be changed as necessary. Patients are placed on postoperative stool softeners for 2 weeks and sedatives as necessary. After 5 days of bed rest, patients should avoid heavy lifting, straining, and sexual activity until 2 weeks postoperatively. At 2 weeks, they may return to sedentary work. Avoiding heavy manual labor is recommended, however. The patient is advised to sneeze with the mouth open and to avoid blowing the nose for 2 weeks.

Pitfalls

There are two potential pitfalls of PLF surgery: (1) inability to obtain adequate hemostasis and anesthesia, particularly in the lower portion of the flap, and (2) inability to obtain adequate visualization of the oval window area without removing the scutum. Some patients also experience discomfort when the surgeon denudes the area around the stapes or over the round window membrane in preparation for graft placement. We avoid placing 4% lidocaine in the middle ear, as is often done for stapedectomy or singular neurectomy. If lidocaine enters the inner ear, the patient becomes violently dizzy and may completely lose hearing in the ear for a short time.

Adhesive band formation between the tympanic membrane and round window graft should be avoided if possible. We advise placement of Gelfilm just medial to the tympanic membrane to help prevent this. If adhesions do form, the patient experiences an apparent sensorineural hearing loss combined with a conductive loss, both of which clear when the adhesion is lysed.

RESULTS

Most series report subjective improvements in vestibular and hearing symptoms, noting better response of vestibular disturbances to PLF surgery. After repair of PLF, 72% to 100% of patients report significant improvement of vertigo or dysequilibrium.31,32,34,40,60 Black and colleagues60 noted objective improvement in dynamic posturography after PLF surgery, with 12 of 32 patients having normal tests after PLF repair. Hearing outcomes after PLF surgery have not shown as much improvement. Hearing improvement has been reported in 13% to 49% of PLF repairs,32,34,40 and stabilization of hearing has been reported in 40% to 67%.33,35,60 Deterioration of hearing has been noted in 11% to 17% of PLF repairs.31,32,40

Negative exploration rates of 40% to 50% for suspected PLFs have been reported. Management of these suspected PLFs differ; some surgeons place grafts in the oval and round windows,34,35 whereas others avoid patching if no leak is visualized.

Fitzgerald and associates35 reported a negative exploration in 78% in their series of 197 patients. They patched the oval and round windows in all cases, and noted positive outcomes in 86% of their patients, leading them to define a proven PLF based on a positive surgical outcome, as opposed to positive intraoperative findings.

Hughes and colleagues61 surveyed 167 otologists in the United States, and noted 78% would place grafts on the oval and round windows at the time of exploration. Advocates of patching both windows in cases of negative exploration cite the possibility of minute62 or intermittent33 leaks. Overall improvement has been reported to range from 29% to 44% of negative explorations with prophylactic patching.33,34 The possibility of placebo effect of PLF surgery has also been considered.

Tissue allografts to patch the oval and round windows have included fat, fascia, perichondrium, and areolar tissue. Multiple authors recommend avoiding use of fat because it has been noted to have increased failure rate.32 Graft sites have also been covered with fibrin glue in hopes of improving postoperative outcome.31,35,63

RECURRENT PERILYMPHATIC FISTULA

If instability and mild vertigo persist after the repair has healed, and if the turning or fistula test results remain positive, re-exploration should be considered. Six weeks should be allowed for the wound to heal completely. Failure occurs most frequently in cases with deep recesses of the oval window, where good access to the anterior crus cannot be obtained to denude the bed adequately and pack the graft tightly into the fistula tract.

Surgeons should attempt re-repair of an oval window PLF at least three times before considering doing a stapedectomy to close the fistula. PLF ears seem more sensitive than others to stapedectomy. High-frequency sensorineural hearing loss has occurred commonly when stapedectomy has been done for a PLF.

Some patients have postoperative improvement with the balance disturbance and motion intolerance symptoms typical of PLF, but develop episodic whirling vertigo typical of Meniere’s disease. Potter and Conner64 raised the issue of possible endolymphatic hydrops secondary to membranous labyrinthine damage caused by PLF. Damage to the membranous labyrinth resulting in hydrops has been theorized to be a result of the initial trauma causing the PLF, the PLF leak itself causing stresses on the membranous labyrinth, or from trauma during surgical repair of the PLF.32 It is far more likely this group of patients had Meniere’s disease to begin with, not PLF.

Lollis and coworkers65 reported a retrospective review of a small series of patients with PLF refractory to otologic surgical management. For patients who showed improvement of their vertiginous symptoms, a ventriculoperitoneal shunt placement was performed. Subjective improvement in symptoms was reported in all patients so treated. No preoperative and postoperative objective measures were available for comparison in this study, however.

SUMMARY

PLF remains a diagnostic and therapeutic challenge. Diagnosis relies on a combination of history-taking, physical examination, and objective audio and vestibular testing. Ultimately, surgical exploration is the gold standard in confirming the presence of a fistula. Patients must be counseled regarding the controversies surrounding the need for and extent of surgical intervention. Alternative diagnoses must also be considered.

REFERENCES

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3. Goodhill V. Sudden deafness and round window rupture. Laryngoscope. 1971;81:1462-1474.

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10. El Shazly M.A., Linthicum F.H. Microfissures of the temporal bone: Do they have any clinical significance? Am J Otol. 1991;12:169-171.

11. Weisskopf A., Murphy J.T., Merzenich M.M. Genesis of the round window rupture syndrome: Some experimental observations. Laryngoscope. 1978;88:389-397.

12. Nishioka I., Yanagihara N. Role of air bubbles in the perilymph as a cause of sudden deafness. Am J Otol. 1986;7:430-438.

13. Douek E. Perilymph fistula. J Laryngol Otol. 1975;89:123-130.

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