Cerebrospinal .. fluid leaks and meningitis in acoustic neuroma surgery GRAHAM E. BRYCE, MD. JULIAN M. NEDZELSKI, MD, DAVID W. ROWED, MD,and JAMIE M . RAPPAPORT, MD,

Toronto, Ontario, Canada Cerebrospinal fluid leaks and associated meningitis are the most common lifethreatening complications of surgery for acoustic neuromas. This retrospective study reviews 319 patients who had surgery for 321 acoustic tumors at the Sunnybrook Health Sciences Center, University of Toronto, from April 1975 to March 1990. Cerebrospinal fluid leaks occurred after 13.4% of primary tumor operations. Surgical repair was required in 6.2% of all patients; 4.4% needed more than one operation. Meningitis occurred in 5.3%of all patients. These complicationswere more common in larger tumors and after the combined translabyrinthine middle fossa approach. Transnasopharyngeal eustachian tube obliteration was used to stop recurrent cerebrospinal fluid leaks in two patients. (OTOIARYNGOL HEAD NECK SURG 1991,104 81.)

I n 1925, Dandy’ refined the suboccipital approach for total removal of acoustic neuromas. In 1964, House’ introduced the microsurgical translabyrinthine operation for removal of these lesions. Both surgeons observed cerebrospinal fluid (CSF) leaks and meningitis complicating these procedures. These complications have continued to frustrate acoustic neuroma surgeons and threaten the lives of their patient^.^" The frequency of these complications has been reduced by the introduction of improved surgical techniques; however, some series continue to report CSF leaks in up to 20%’,‘j and meningitis in 5%’.’ of patients. Although some authors8-” have reported much lower frequencies of these complications, other recent studies have not duplicated these results. 3-7.1 The purpose of this report is to review our experience with these complications of acoustic neuroma surgery. We propose hypotheses to explain the mechanisms that underlie the development of CSF leaks and present our strategy for the prevention and treatment of CSF leaks and bacterial meningitis. A transnasopharyngeal approach to eustachian tube obliteration used in two cases of recurring CSF leak is described. ‘3’’

From the Department of Otolaryngology (Drs. Bryce and Nedzelski) and the Division of Neurosurgery (Dr. Rowed), Sunnybrook Health Sciences Center, University of Toronto, and Mount Sinai Hospital (Dr. Rappaport), University of Toronto. Presented at the Annual Meeting of the American Neurotology Society, Palm Beach, Fla., April 27-19, 1990. Received for publication May 4, 1990; accepted July 15, 1990. Reprint requests: Julian M. Nedzelski, MD, Department of Otolaryngology, Sunnybrook Health Sciences Center, 2075 Bayview Ave., Toronto, Ontario M4N 2M5 Canada. 231 1125415

METHOD Subjects

Between April 1975 and March 1990, a total of 319 patients had surgery for 321 acoustic neuromas at Sunnybrook Health Sciences Centre, University of Toronto. Patients ranged in age from 16 to 84 years, with a median age of 49. There were 160 men and 158 women and 157 right-sided and 164 left-sided tumors. Among seven patients who had bilateral tumors, two had both tumors excised and five either had had one tumor operated on elsewhere or were having their second tumor observed. Diagnostic Criteria

CSF leaks after surgery for acoustic neuroma can occur through the incision, through a defect in the tympanic membrane, as otorrhea, or via the eustachian tube as otorhinorrhea. CSF leaks were diagnosed when a clinician observed either spontaneous or Valsalva maneuver-induced CSF drainage. When a definite CSF leak was not seen but there was a strong patient history of clear rhinorrhea, the CSF leak was confirmed with radionucleotide studies. Leaks were described as “early” if they began up to the tenth postoperative day and “late” if they occurred after this interval. A diagnosis of associated hydrocephalus was made where there was computed tomographic (CT) evidence of progressive ventricular enlargement or compromise of the fourth ventricle, either before or after surgery for acoustic tumor. Meningitis after excision of acoustic neuroma results from aseptic inflammation or bacterial infection of the meninges. Although they have distinct pathophysio81

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Table 1. Total operations, incidence, site, and treatment of CSF leaks, and incidence of meningitis according to surgical approach Approach Subocclpltal ____

Combined (TLIMF)

All approaches

_____

Total operations for mtervals 48 4/75 - 12/85 1I86 - 3/90 28 4/75 - 3/90 76

CSF leaks for intervals 4/74 - 12/85 1186 - 3/90 4/75 - 3/90

Translabyrinthine

~

4 (83%) 4 (14 3%) 8 (10 5%)

91 112 203

40 0 42

181 140 321

11 (121%) 12 (10 7%) 23 (11 3%)

12 (28 So/) 0 (none done) 12 (28 6%)

27 (14 9Yo) 16 (11 4%) 43 (13 4%)

Site of CSF leak Incision Otorrhea Rhinorrhea Occult

1 3 4 0

12 1 10 0

2 0 7 3

15 (34 9%) 4 (9 3%) 21 (488%) 3 (7 OYO)

Treatment of CSF leaks Expectant Lumbar drain Surgery

1 7 0

3 9 11

'0 3 9

4 (9 3%) 19 (44 2%) 20 (46 5%)

6 (14 3%)

17 (5 3%)

Meningitis

2 (2 6%)

9 (4 4%)

logic mechanisms, it is often difficult to distinguish between the benign sterile process and the potentially lethal infection on the basis of clinical and laboratory criteria. This series reviews all patients who were treated with antibiotics postoperatively for presumed bacterial meningitis. Features Reviewed Tumor size. Tumor size was classified according to the largest diameter of the extracanalicular portion of the tumor. l 3 Small tumors were 5 1 . 5 cm, medium ones >1.5 cm and 1.5 i3.0 cm)

(2large 3.0 cm)

142 8.7

90 9.6

89 23.5

11 (7.7%)

16 (17.8%)

16 (18.0%)

3 (2.1%)

6 (6.7%)

8 (9.0%)

Table 3. Number of Operations and success rate for surgical techniques used to close CSF leaks

Tympanotomy with ET and ME pack Transmastoid pack repositioning Radical mastoidectomy with obliteration of EE, ME, and ET Transnasopharyngeal ET obliteration

No. of operations

No. of successful operations

5

3 (60%)

19

10 (53%)

9

5 (56%)

2

2 (100%)

EE, External ear, ME, mtddle ear, €7, eustachian tube

(34.9%). The leaks that presented as otorrhea (9.3%) after suboccipital surgery were associated with tympanotomy performed to allow placement of a promontory electrode and one case that followed an unintentional surgical defect of the posterior canal wall during a combined approach. Three patients (7.0%) had occult leaks that manifested as persistent or recurrent meningitis. Leaks were more frequent from the ear or nose after the suboccipital operation, whereas with the translabyrinthine approach there were more leaks from the incision. The majority of CSF leaks were treated with either lumbar drainage (44.2%) or surgery (46.5%). None of the patients with CSF leaks after suboccipital surgery required surgical closure, but almost half (47.8%) of the translabyrinthine cases did. The small number of patients in each of these groups did not allow determination of the statistical significance of this difference. Six patients had successful closure of their leaks after one operation, nine after two operations, four after three operations, and one patient required four operations

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an average of 17.7 days, and the 12 who later required readmission for treatment of their leaks spent on average an additional 22.4 days in the hospital.

Table 4. Average values for CSF studies performed on day of diagnosis for patients with bacterial culture-positive and -negative meningitis CSF CSF culture-positive culture-negative ~

CSF glucose (N = 2 8 to 4.2 rnrnol/L) CSF protein (N = 250 to 550 rng/L) CSF neutrophils x 106/L CSF red blood cells x 106/L

130

3 09

1769

749

3070 12,108

650 75,387

before the leak was finally closed. Tympanotomy with temporalis muscle packing of the eustachian tube and middle ear, or repositioning of the mastoid pack, was just as likely to be successful as radical mastoidectomy with obliteration of the external ear, middle ear, and eustachian tube (Table 3). Two patients who had had repeated operations for closure of their leaks had successful closure after obliteration of the nasopharyngeal meatus of their eustachian tubes. Again, the numbers of patients in these groups are too low to give statistical significance to these findings. In the 20 patients who were operated on for closure of leaks after either the translabyrinthine or combined (TL/MF) approach, the most common sites where leakage was noted at surgery were from the area of the mastoid antrum (30%) and the hypotympanum (25%). Other sites included the internal auditory canal, peritubal, retrofacial, and epitympanic air cells, and the vestibule. More CSF leaks were seen early (29 [67%] 510 days) rather than late (14 [32.6%] >10 days), although this difference was not significant (Fisher’s exact test, p = 0.98). Only one of eight CSF leaks after suboccipital surgery began more than 10 days after surgery, whereas one third of those after the translabyrinthine operation started after the tenth postoperative day. More early leaks (18 [62.1%]) were succuessfully treated with lumbar drainage, whereas late leaks were usually operated on (12 [85.7%]). The average initial hospital stay for all patients was 12.4 days. The average length of the initial hospital stay for all patients reported according to tumor size is shown in Table 2. Patients with large tumors had significantly longer hospital stays (23.5 days) than those with small (8.7 days) or medium-sized tumors (9.6 days) (one-way analysis of variance with Turkey’s pairwise comparisons, p < 0.05). Most patients who have recently undergone surgery without complications have been discharged on the seventh day of hospitalization. The 43 patients whose postoperative course was complicated by CSF leakage were initially hospitalized for

Meningitis

Meningitis was diagnosed in 17 (5.3%) patients (Table 1). It was associated with a CSF leak in 14 patients, whereas three had meningitis alone. The incidence of meningitis related to tumor size is shown in Table 2. There was an increase in the frequency of meningitis when those patients who had large tumors (9.0%) were compared with those who had small tumors (2.1%; Fisher’s exact test, p = 0.020). Although there was a trend suggesting a lower rate of meningitis in patients with medium-sized compared to small tumors, the difference was not significant for the numbers of patients in these groups (Fisher’s exact test, p = 0.08). There was no difference in the meningitis rate between the group with medium-sized tumors compared to the groups with large tumors (Fisher’s exact test, p = 0.383). Meningitis was significantly more frequent in the combined (TL/MF) operation (14.3%) than in either the suboccipital (2.6%; Fisher’s exact test, p = 0.023) or the translabyrinthine (4.4%; Fisher’s exact test, p = 0.027) approach. However, the difference in incidence between the latter two operations was not significant (Fisher’s exact test, p = 0.38). Of the 17 patients with a diagnosis of meningitis, eight (47%) had positive CSF bacterial cultures and five of these had bacteria seen on Gram stain. One patient had gram-positive cocci seen on Gram stain, but no growth on CSF culture. The organisms cultured included pneumococcus (two patients), Hemophilus influenzae (two patients), Staphylococcus epidermidis (two patients), P-hemolytic streptococcus (one patient), and Escherichia coli (one patient). Gram stains were positive for each of the positive cultures, except in one of the patients with S. epidermidis and both patients with H . influenzae meningitis. The average maximum temperature on the day of diagnosis of patients with culture-proven bacterial meningitis was 39.1” C compared to 38.8” C in the patients with negative cultures. Thirteen of the 17 patients with a diagnosis of meningitis had stiff necks, 15 had headache, and nine had altered levels of consciousness. The average serum white blood cell count of patients with positive cultures on the day of diagnosis was 19.88 X 109/L with 87% neutrophils compared to 12.07 x 109/L and 80% in patients with negative cultures. The average CSF glucose, protein, cell count, and differential findings for the culture-positive and culture-negative groups on the day of diagnosis are shown in Table 4. CSF glucose tended to be lower and CSF protein higher in the group with positive cultures; however, there was a wide range of results for all tests

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CSF leaks and meningitis in acoustic neuroma surgery 85

in both groups. The presence of blood in the subarachnoid space postoperatively confounded by blood admixing with the sample at the time of the diagnostic lumbar puncture meant that the CSF cell count and differential contributed little to the diagnosis and treatment of meningitis. The wide distribution of temperatures and laboratory values obtained for the small number of patients in the culture-positive and culturenegative groups does not allow reliable statistical comparison of the results. The average initial postoperative stay for the 17 patients with meningitis was 27.3 days, compared to the average 12.4 days for all patients undergoing surgery for an acoustic tumor. Six patients with meningitis later required readmission for an average of 28.0 days. One patient who suddenly collapsed, losing consciousness on the eighth postoperative day, had pneumocephalus on CT scan and was thought to have an occult CSF leak and meningitis. His CSF cultures were negative. In spite of aggressive antibiotic treatment and surgical closure of the CSF leak, he did not regain consciousness and died 6 months postoperatively. Another death occurred in the series of patients with CSF leak alone. This 62-year-old woman had CSF rhinorrhea on the first postoperative day. The following day she collapsed suddenly, and CT scan showed a massive intracerebellar hemorrhage contralateral to the side operated on. She never regained consciousness and died on the fifth postoperative day. The third death in the overall series occurred in a 65-year-old woman. She died after postoperative hemorrhage into the cerebellopontine angle. The overall mortality rate in this series was 0.9%. DISCUSSION CSF leaks

Our 13.4% incidence of CSF leaks is comparable to that of other current investigators.3.S-7.""2The factors that proved to be associated with a significantly increased risk of CSF leak were medium or large tumor size and a combined (TL/MF) surgical approach. The significant increase in the rate of CSF leak in groups with small and medium-sized tumors, both of which had few combined (TL/MF) surgeries, indicates that the increase in leak rate with increased tumor size is not solely an effect of the higher leak rate associated with the combined (TL/MF) approach. The increased CSF leakage rate with larger tumors may relate to there being less of a postoperative ballotting effect of the cerebellum against the surgical dural defect. With a larger tumor, the cerebellum is more medially displaced and expands more slowly than if a small tumor causes only minimal cerebellar compression. We did not find a difference in the rate of CSF leakage between the suboccipital and translabyrinthine operations, although the leaks after the latter surgery required operative

closure more frequently. Late CSF leaks, occurring more than 10 days postoperatively, tended to occur more frequently after the translabyrinthine operation. Because patients may be home when these leaks start, it is important to warn patients at the time of discharge from the hospital about the danger signs of CSF leakage. Most patients in this series had either lumbar drainage or surgical closure as treatment for their CSF leaks. We took an aggressive approach to treating these leaks, because we thought that they were less likely to close spontaneously than, for example, CSF leaks after temporal bone fracture. There are two types of passages that are available to leaking CSF after excision of acoustic neuroma: those created by the surgical defect and those through the pneumatized portions of the temporal bone. CSF gaining access to any air cell has the potential to follow natural air-cell tracts to a number of openings into the mastoid, middle ear, and tympanic meatus of the eustachian tube. A review of the embryology and anatomy of these tracts sheds light on how CSF leaks occur and suggests how they can be prevented. Pneumatization of the temporal bone occurs by extension of air-cell tracts from the middle ear into the mastoid, petrous, and accessory areas. I4 The mastoid is aerated by invagination of the saccus superior to the squamous temporal bone to form the anterolateral air cells and by expansion of the saccus medius into the petrosa to form the posteromedial cells. These areas are separated by the usually incomplete bony Korner's septum. Originating from the antrum, these tracts produce most of the mastoid air-cell system, although some cells may come from the hypotympanum medial to the vertical portion of the facial canal to form a retrofacial group. The petrous temporal bone can be divided by a vertical plane in the axis of the cochlear modiolus into the apical petrous in front and the perilabyrinthine portion behind." These areas are pneumatized by air-cell extensions from the eustachian tube, middle ear, and mastoid. These extensions created cell tracts that follow superior and inferior routes to the petrous apex. The posteroinferior route courses behind the cochlea and carotid canal and below the cochlear aqueduct, above the jugular bulb, and below the internal auditory canal. The anteroinferior path runs in front of the cochlea, above the cartoid canal from peritubal and pericarotid cells directly into the apex. The superior cell tract reaches the petrous apex by skirting the posterior otic capsule and passing above the internal auditory canal. These systems may be separated, forming cul-de-sacs, or may be widely interconnected. Once CSF escaping through a surgical dural defect reaches any point in this honeycomb, the fluid may reach the middle ear. If there is a tympanic or external

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Fig. 1. Posterior view of left temporol bone ofter translabyrinthine dissection. 1, Mastoid antrum; 2, oval window; 3, vestibule; 4, site where opicol cells above internol ouditory conal would be exposed; 5, opicol cells below internol ouditory conol leadingto hypolymponum; 6, sinus tympani; Z retrofociol cells.

auditory canal wall defect, CSF present in the middle ear can either flow out of the ear or pass through the eustachian tube, producing, respectively, otorrhea and/or otorhinorrhea. After surgery for suboccipital acoustic neuroma, CSF may leak directly through the occipital dural defect either out the incision or, by entering the anterolateral mastoid air-cell system through a passage lateral to the sigmoid sinus, gain access via the mastoid antrum to the middle ear. The fluid may also reach the middle ear if either the superior or inferior perilabyrinthine cells are left exposed after removal of the posterior wall of the internal auditory canal. In this case, CSF can reach the middle ear directly through infralabyrinthine cells connected to retrofacial or hypotympanic cells or through the mastoid antrum from superior perilabyrinthine tracts. In the translabyrinthine operation (Fig. l ) , fluid can also pass from the lateral internal auditory canal defect into the vestibule, and from there into the middle ear through the oval window if the stapes has been subluxed. Fluid leaking into the vestibule may also pass through the mastoid antrum into the middle ear. In this approach, CSF can pass into the middle ear through retrofacial cells or through the sinus tympani. if these areas are opened at surgery. Another potential pathways for CSF leakage from the subarachnoid space into the middle ear is through the anteroinferior apical tracts, which may lead to cells immediately adjacent to the tympanic orifice of the emtachian tube. This may occur with either approach. In summary, CSF may cause otorrhea or rhinorrhea after reaching the middle ear through the mastoid antrum, sinus tympani, retrofacial or facial recess cells, a defective oval window, or petrous air cells opening directly into the tympanic cavity.

To prevent the development of CSF leaks after the suboccipital approach, water-tight closure of the retrosigmoid dural incision can usually be achieved. and all air cells opened in the course of performing the occipital crainiectoniy and any cells exposed while taking down the posterior internal auditory canal wall are sealed with bone wax. Mastoid obliteration has the same goal in the translabyrinthine operation, but the latter approach also allows access to the tympanic cavity and eustachian tube, the final common pathway of many CSF leaks. To obliterate the eustachian tube and prevent CSF leaks after the translabyrinthine operation, we remove the incus and head of the malleus and divide the tensor tympani tendon. This allows access through the aditus to the epitympanuni and tympanic meatus of the eustachian tube. The mucosa lining the eustachian tube is then abraded and the lumen packed with temporalis fascia. The middle ear is filled with temporalis muscle and the aditus obstructed with fascia lata impacted with a wedge of bone. Our goal in this assault on the eustachian tube and middle ear is to temporarily prevent flow of CSF through the surgical defect in the iinniediate postoperative period. Decreasing this flow allows the potential channels through which CSF could pass to seal without a constant current of fluid. The eustachian tube obstruction is transient. Every patient, when seen at the 6-month postoperative visit. has had a normally ventilated middle ear. The mastoid and petrous defect is obliterated with fascia lata, which is draped to contact exposed bone and the divided edges of the dura. The resulting pocket of fascia is filled with fat. The mastoid periosteuni, which has been carefully preserved during the earlier phase of the operation. is reapproximated and compresses the fascia and fat. In those

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CSF leaks and meningitis in acoustic neuroma surgery 87

cases that have required re-exploration, we have noted that the fat is richly vascularized and the fascia1 layer is firmly adherent to adjacent bone, providing an excellent seal of the adjacent area. A postoperative CSF leak initially seen at the incision is managed with reinforcement of the wound closure and lumbar drainage. Persistent incisional leaks after the translabyrinthine operation or persistent otorrhea or otorhinorrhea after either approach are best managed with radical mastoidectomy and obliteration of the external and middle ear and the eustachian tube.I6 The nasopharyngeal approach to eustachian tube obstruction can be useful in a patient with a persistent CSF leak. Should this approach be unsuccessful, the eustachian tube can be obliterated through the middle fossa. ” Radical obliteration of the external ear, middle ear, and tympanic eustachian tube meatus was successful in preventing further CSF leakge in 56% of patients who had this procedure for treatment of postoperative CSF leaks. We do not believe the added operative effort required to incorporate these techniques into the primary translabyrinthine operation is justified. Menlngitls

Our incidence of meningitis (5.3%) is similar to that reported by other^.^,'-^.'^ This study found an increased risk of meningitis with medium and large tumor size, as well as with the combined (TL/MF) approach used early in the series. Meningitis was usually associated with a CSF leak. Better prevention and control of CSF leaks should further reduce the frequency of meningitis. No particular clinical or laboratory findings allowed differentiation of patients with bacterial meningitis from those with sterile inflammation. The safest approach in patients with suspected meningitis is to treat them with the appropriate therapeutic course of antibiotics. Intravenous combined therapy with chloramphenicol and ampicillin or ceftriaxone, a third-generation cephalosporin with a high degree of blood-brain barrier penetration, alone is a good initial choice, with subsequent antibiotic selection based on the results of CSF culture. CONCLUSIONS

1. There is no difference in the rate of CSF leakage or meningitis between the suboccipital and translabyrinthine operations for acoustic neuroma excision, although leaks after the suboccipital operation were controlled with lumbar drainage, whereas half of those after the translabyrinthine approach required surgical closure. 2. Meningitis and CSF leakage are more likely to occur with larger tumors and after the combined (TL/MF) approach.

3. Transnasopharyngeal eustachian tube obliteration can be a useful adjunctive technique in patients with persistent postoperative CSF otorhinorrhea. We would like to thank Donald Hayes, MA, for his assistance with the clinical data bases and John P. Szalai, PhD, and Marko Katic, BA, for their help with the statistical preparations.

REFERENCES

1. Dandy WE. Operation for total removal of cerebellopontine (acoustic) tumors. Surg Gynecol Obstet 1925;41:129-48. 2. House WF, ed. Monograph. Transtemporal bone microsurgical removal of acoustic neuromas. Arch Otolaryngol 1964;80:597756. 3. Mangham CA. Complications of translabyrinthine vs suboccipHEAD ital approach for acoustic tumor surgery. OTOLARYNG~L NECKSURG1988;99:396-400. 4. Brow RE. Pre- and postoperative management of the acoustic tumor patient: Acoustic tumors. Vol 11. Management. Baltimore: University Park Press, 1979: 153-73. 5. Hughes GB, Glasscock ME, Hays JW, Jackson CG, Sismanis A. Cerebrospinal fluid ‘‘leaks’’ and meningitis following acoustic tumor surgery. OTOLARYNG~L HEADNECKSURG1982;90:11725. 6. Mercke U, Hams S , Sundbarg G. Translabyrinthine acoustic neuroma surgery as performed by the otoneurosurgical group at Lund University Hospital. Acta Otolaryngol (Stockh) 1988;452: 34-7. 7. King TT,Morrison AW. Translabyrinthine and transtentorial removal of acoustic nerve tumors. J Neurosurg 1980;52:210-16. 8. Montgomery WW. Surgery for acoustic neurinoma. Ann Otol Rhinol Laryngol 1973;82:428-44. 9. Fisch U, Mattox D. Transotic approach to the cerebellopontine angle. Part 1. General considerations. In: Fisch U, Mattox D, eds. Microsurgery of the skull base. New York: Thieme Medical Publishers, Inc, 1988:74-83. 10. House JL, Hitselberger WE, House WF. Wound closure and cerebrospinal fluid leak after translabyrinthine surgery. Am J Otol 1982;4:126-8. 11. DiTullio MV Jr, Malkasian D, Rand RW. A critical comparison of neurosurgical and otolaryngologic approaches to acoustic neuromas. J Neurosurg 1978;48:1-12. 12. Tos M, Thomsen J, Harmsen A. Results of translabyrinthine removal of 300 acoustic neuromas related to tumor size. Acta Otolaryngol (Stockh) 1988;452:38-51. 13. Nedzelski J. Cerebellopontine angle tumors: bilateral flocculus compression as cause of associated oculomotor abnormalities. Laryngoscope 1983;93: 1251-60. 14. Proctor B. Chapter 4. Cavities of the temporal bone: Pneurnatization of the temporal bone. In: Proctor B, ed. Surgical anatomy of the ear and temporal bone. New York: Thieme Medical Publishers, Inc, 198935-8. 15. Allam AF. Pneumatization of the temporal bone. Ann Otol Rhinol Laryngol I969;78:49-64. 16. Hamer SG, Laws Jr ER. Translabyrinthine repair for cerebrospinal fluid otorhinorrhea. J Neurosurg 1982;57:258-61. 17. Glasscock ME, Hays JW, Murphy JP. Complications in acoustic neuroma surgery. Ann Otol Rhinol Laryngol 1975;84:530-40.

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Cerebrospinal fluid leaks and meningitis in acoustic neuroma surgery.

Cerebrospinal fluid leaks and associated meningitis are the most common life-threatening complications of surgery for acoustic neuromas. This retrospe...
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