Management of Acoustic Neuromas
(Vestibular Schwannomas)
File 4: Management and References

by ROBERT G. OJEMANN, M.D.
© Congress of Neurological Surgeons Honored Guest Presentation
Originally Published Clinical Neurosurgery, Volume 40, Chapter 24, Pages 498-535, 1992
Used with permission of the Congress of Neurological Surgeons.
HTML Editor: Stephen B. Tatter, M.D., Ph.D.

Contents

• INTRODUCTION (File 1)
• SURGICAL MANAGEMENT (For surgeons!, File 2)
  • Overview
  • Perioperative Medical Therapy
  • Monitoring
  • Position
  • Incision and Exposure
  • Removal of Small Tumors and Hearing Preservation
  • Removal of Medium and Large Size Tumors
  • Closure
  • Management of Postoperative Complications
    • Hematoma and Cerebellar Infarction
    • Cerebrospinal Fluid Fistula
    • Hydrocephalus
    • Meningitis
    • Wound Infection
    • Neurological Complications
    • Headache
• RESULTS OF SUBOCCIPITAL OPERATION: Summary of the Series, 1979-1992 (File 3)
  • Extent of Tumor Removal and Recurrence
  • Postoperative Complications
  • Cochlear Nerve Function
  • Management of Tumor in the Only Hearing Ear
  • Management in Elderly Patients (70 Years and Older)
  • Management in Patients with Preoperative Hydrocephalus
• RADIOTHERAPY MANAGEMENT (This File)
• OBSERVATIONAL MANAGEMENT (This File)
• MANAGEMENT PLAN (This File)
• REFERENCES (This File)

FIG-24.13: Indication for operation. This 20-year-old woman had transient vertigo while figure skating. Mild hearing loss was noted in her left ear and she developed frontal headaches. The MRI axial Tl image after gadolinium showed a large tumor consistent with an acoustic neuroma. Total removal was done. Facial nerve function was grade 3. She was able to resume figure skating.

FIG-24.14: Indication for operation. This 52-year-old man had decreased hearing in his left ear for >1 year and increased numbness on the left side of his face for 2 months. The MRI axial TI image showed anterior growth of the tumor. Total removal was followed by full recovery and normal facial nerve function.

RADIOTHERAPY MANAGEMENT

In 1971 Leksell (20) reported the first use of stereotactic radiosurgery to treat a patient with an acoustic neuroma. Subsequently, further experience was reported (34). Detailed and comprehensive follow-up reports have been published by Lunsford and his group (26); summarizing the experience at the University of Pittsburgh, which had the first North American 201-source 611C gamma unit. Reports from both these groups show a high rate of tumor growth control and an acceptable rate of complications. These facts have established stereotactic radiosurgery as one of the three treatment alternatives to consider in a patient with an acoustic neuroma.

In January 1992 the results for 74 patients with unilateral acoustic neuromas were reported by the Pittsburgh Group. There was no mortality and all returned to their previous level of activity in 5-7 days. The followup ranged from 3 to 36 months, and two tumors (3%) were larger, 54 (73%) were the same, and IS (24%) were smaller. The measurement error was estimated to be ±1.3 mm, and a change of ±2.6 nun was required to categorize the change as smaller or larger. The two patients with larger tumors had no new symptoms and are being observed.

In the same report, of 70 patients with normal preoperative facial nerve function 24 (34%) developed a delayed facial nerve weakness. At the time of follow-up, 13 of the 24 had made a good recovery (six grade 1 and seven grade 2), leaving 11 of the 70 (16%) with grade 3 or worse. This complication could not be correlated with tumor size or any of the radiation dosage parameters. The preservation of useful hearing, as deflned by at least a 50% SDS and pure tone average of 50 db or less, was 38% at 1 year. This could not be statistically correlated with tumor size. However, it was also noted that of 13 patients with tumors of <1.0-cm diameter none had lost useful hearing. Of 66 patients with normal preoperative trigeminal nerve function 32% developed delayed trigeminal neuropathy. In those with abnormal function it was 46%. Only 10% had resolved completely at follow-up but most seemed to be improving. A significant correlation between radiation dose and delayed cranial neuropathies could not be demonstrated.

Other persistent problems included worsened balance in 20-30% and a small percentage of patients with dizziness or vertigo, persistent nausea, and worsened headaches. Eight patients developed new parenchymal changes in the middle cerebellar peduncle and pons on MRI scans. No associated symptoms were noted, and these changes tended to resolve. Four patients required ventriculoperitoneal shunt 5-16 months after radiosurgery. The cause of the hydrocephalus was thought possibly to be elevated cerebrospinal fluid protein levels.

FIG-24.15: Indication for operation. This 45-year-old man reported increasing difficulty hearing over the telephone with his left ear, for several months. The MRI axial TI image after gadolinium showed a small tumor projecting about 1.0 cm into the posterior fossa. The audiogram showed useful hearing with a SDS of 60%. Total removal was done, with preservation of hearing and facial nerve function.

Other types of radiation therapy have also been reported to have a beneficial effect on an acoustic neuroma. These include fractionated conventional therapy, proton beam therapy, and radiosurgery using the linear accelerator (6, 57).

OBSERVATIONAL MANAGEMENT

Acoustic neuromas usually enlarge slowly. However, it has been well documented that some tumors stop growing, that spontaneous regression may occasionally occur, and that a rare tumor may unexpectedly grow rapidly (2, 32, 56). Bederson et al. (2) reported 70 patients who were initially observed because they did not want surgery or did not have progressive symptoms. The average follow-up was 36 months (range, 6-84 months). During the first year 29 patients (41%) had no detectable tumor growth and, of 18 who had a second-year scan, only one showed detectable growth. In 37 patients (53%) growth ranging from I to 17 mm (average, 3.4 ± 0.5 mm) occurred during the first year and, of 23 patients with a second-year follow-up scan, 21

FIG-24.16: Indication for operation or radiation therapy. This 68-year-old woman had a history of progressive hearing loss in her right ear for 2 years and problems with balance and lightheartedness for 1 year. The MRI axial TI image after gadolinium (A) showed a 1.5cm tumor consistent with an acoustic neuroma. She was initially observed. MRI 6 months later (B) showed enlargement of the tumor. After being presented with the treatment options, she asked to have the tumor removed. She made a full recovery with normal facial nerve function. Radiation therapy would have been an acceptable alternative.

showed further growth. In four patients (6%) there was regression in tumor size. Rapid growth rate in seven and clinical deterioration in two other patients without change in the size of the tumor led to surgical intervention. There was no relationship of tumor growth to age, duration of symptoms, or initial tumor size. Another study also documented that there was no correlation between tumor growth and the patient's age and that, over a period of 8 months to >4 years, 50% showed no change (56). The true incidence of cessation of growth is unknown since these were selected patients, many of whom had stable symptoms.

MANAGEMENT PLAN

With the increasing information available in the literature regarding the three management options, surgery, radiotherapy, and observation, the physician caring for these patients can begin to make informed recommendations.

First, physicians must take the patient's history themselves to have a clear idea of the course of the disease and how the symptoms are affecting the patient's life. An objective assessment of any neurological deficit should be made. Radiographic studies should be carefully reviewed to be sure they are adequate and a decision should be made regarding whether any additional studies are needed.

In some patients there is little doubt as to what should be done.

FIG-24.17: Indication for operation or radiation therapy. This 72-year-old man had progressive hearing loss. The MRI axial TI image after gadolinium (A) showed a 1.0-cm tumor. He was observed and there was no change for I year. However, the MRI scan (B) at 18 months showed definite enlargement. He was treated with radiosurgery. Surgery would have been an acceptable alternative.

In other patients the decision may be difficult (40). To arrive at a decision the physician must have up-to-date knowledge about the natural history and treatment alternatives. With this information the physician can then weigh the management options. What will be the impact on the patient's daily life? Will the treatment improve or arrest the progression of symptoms? Can further growth or recurrence of the tumor be prevented? What are the risks of the treatment? Do the short- and long-term benefits justify these risks? It is important to discuss with patients their hopes and expectations regarding the treatment.

Several factors are considered when making the treatment recommendation. These include the history and findings, age of the patient, size of the tumor, the patient's overall clinical condition, and the expected benefits and risks of the treatment options. It is not practical to defme a specific age which influences the decision to operate, observe the patient, or use radiotherapy. However, in the older patient a clinical judgment is made based on these factors.

My indications for operation are as follows.

1. Recent or worsening symptoms, except for elderly patients with mild symptoms (Figs. 24.13 and 24.14). With small tumors an attempt is made to preserve useful hearing (Fig. 24.15). For large tumors radical subtotal or subtotal removal is considered, especially in older patients, if there is adherence (Figs. 24. 11 and 24.12).
2. Enlargement of the tumor in patients who are being observed (except some elderly patients) (Fig. 24.16).
3. Regrowth after subtotal removal when it is likely that a more extensive removal can be done.
4. The patient's decision after discussion of the treatment options (Fig. 24.16).

My indications for radiation therapy are as follows.

1. Enlarging small or medium size tumor in an elderly patient with n-tild symptoms who is being observed (Flg. 24.17).
2. Regrowth after subtotal removal (Fig. 24.18).
3. Associated major medical illness.
4. The patient's decision after discussion of the treatment options.

FIG-24.18: Indication for radiation therapy. This 70-year-old woman had a history of hearing loss in her right ear and increasing numbness on her face. A subtotal removal of a large acoustic neuroma was done. The residual tumor remained stable for 2 years, after which it started to grow. MRI TI axial (A) and coronal (B) images after gadolinium showed the size and configuration of the tumor. Fractional radiation therapy was given, with arrest of the growth.

My indications for observation are as follows.

1. A long history of auditory symptoms in patient of any age with any size tumor (Fig. 24.19).
2. An elderly patient with rnild symptoms (Fig. 24.20).
3. An incidental finding of the tumor on a scan done for some other reason.
4. The patient's decision after discussion of the treatment options.

Conclusion

The outlook for a patient with an acoustic neuroma is markedly improved over what it was when I saw my first patient with this tumor in 1957. There is every expectation that advances will continue for the benefit of these patients.

REFERENCES

1. Baldwin D. L., King, T. T., and Morrison, A. W. Hearing conservation in acoustic neuroma surgery via the posterior fossa. J. Laryngol. Otol., 104: 463-467, 1990.
2. Bederson, J. B., von Ammon, K., Wichmann, W. W., el al. Conservative treatment of patients with acoustic neuroma. Neurosurgery, 28: 646-651, 1991.

   FIG-24.19: Indication for observation. This patient was first seen at age 55 with a history of sudden loss of hearing in his left ear 9 years previously. There was intermittent facial numbness. He was fully active and ran 50 miles per week. There were no abnormalities except the hearing loss on neurological examination. CT scan showed a large cerebellopontine angle tumor consistent with an acoustic neuroma. Because of the long history of stable symptoms, he was observed. The MRI axial TI image after gadolinium 9 years later, shown here, revealed no change in the size of the tumor and there are no new symptoms.

3. Cohen, J. L. Retrosigmoid approach for acoustic tumor removal. Otolaryngol. Clin. North Am., 25: 295-310, 1992.
4. Cohen, N. J., Berg, H., Hammerschlag, R., et al. Acoustic neuroma surgery: an eclectic approach with emphasis on preservation of hearing. Ann. Otol. Rhinol. Laryngol., 93:21-27,1986.
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    FIG-24.20: Indication for observation. This 76-year-old man presented with a 1 year history of progressive hearing loss in his left ear. This was of little concern to him. The MRI axial TI image after gadolinium shows findings consistent with a small acoustic neuroma that is being followed and has not changed in size.

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