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Acoustic neuroma

Acoustic neuroma (or Vestibular Schwannoma) is a benign tumor of the the myelin forming cells called "Schwann cells" of the 8th cranial nerve, known as the acoustic nerve, (or more properly the vestibulocochlear nerve) just after it has left the brainstem, in the pontine angle; also at the point where the peripheral part of the nerve meets the brain part of the nerve called "Hensen's node". more...

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Multiple names used for this type of tumor include acoustic neuroma, acoustic neuronoma and vestibular schwannoma because it attacks the 8th cranial nerve which branches in to the vestibular and acoustic; and under a microscope the tumor resembles schwann cells.


Associated symptoms are unilateral sensorineural hearing loss/deafness and vertigo. Additionally more than 80% of patients having acoustic neuromas have reported tinnitus. Larger tumors can compress local structures such as the facial nerve, and lead to local symptoms such as hydrocephalus.

If the tumor grows next to the brain stem and grows large enough, the brainstem may become compressed. Also associated with these nerves is the 7th cranial nerve; this nerve controls the muscles of the face, salivation, tearing, and taste. If a significantly large tumor develops it can involve the 5th cranial nerve controlling the sensation face and eyes.

While most cases occur sporadically, acoustic neuroma may be attributable to neurofibromatosis (type 2) in about 5% to 10% of the cases. If the tumor is caused by Neurofibromatosis a slightly different type of tumor grows, then the tumor often involves the whole nerve rather than particular sections of the nerve as does the schwannoma which can make treatment more a greater challenge. Also the tumor is classically bilateral with this syndrome.


Indicated treatments for acoustic neuroma include surgical removal and radiotherapy.

Conservative treatment

Because these neuromata grow so slowly, a physician may opt for conservative treatment beginning with an observation period. In such a case, the tumor is monitored by annual MRI to monitor growth. Records suggest that about 45% of acoustic neuromata do not grow detectably over the 3-5 years of observation. In rare cases, acoustical neuromata have been known to shrink spontaneously. Oftentimes, people with acoustic neruromata die of other causes before the neuroma becomes life-threatening. (This is especially true of elderly people possessing a small neuroma.)

Since the growth rate of an acoustic neuroma rarely accelerates, annual observation is essential.

Acoustic neuromata may cause either gradual or—less commonly—sudden hearing loss and tinnitus. However, the surgical and radiotherapy treatments are even more dangerous to the hearing in the affected ear.


The surgery is done by several approaches and is associated with high incidence of complications and quality of life issues - but it often removes the tumor without recurrence. The vestibular nerve is usually removed on the operated side, resulting in severe imbalance, vertigo and dizziness. However, vestibular function improves rapidly due to compensation by the other ear and other balance mechanisms. Steadiness may never be 100% of the pre-surgical level, but patients are usually walking in the first week after surgery. Surgery also has a risk to the facial nerve which is "monitored" during the surgery. Best results (normal or near normal facial function) are most likely with small acoustic neuromas. The larger the tumor, the higher the risks associated with removing it. Three surgical approaches are commonly used. The first is the translabyrinthine, which destroys hearing in the affected ear. Of the surgical approaches, it tends to be the fastest (less anesthesia time) and allows the most complete removal of the tumor (less chance of recurrence). The two other approaches (suboccipital and middle fossa) are hearing preservation approaches, which have a chance of preserving some or all of the hearing in the affected ear. However, all or most of the hearing in the operated ear is lost approximately 50% of the time. In addition, a number of medical reports indicate that surgically preserved hearing in the operated ear is often not stable, but may deteriorate significantly over a period of years. The hearing preservation approaches tend to require longer surgery, have a higher risk of recurrence and both require brain retraction, which carries a low risk of brain damage. Acoustic neuroma surgery is highly technically demanding, and patients are advised to seek out surgical teams with extensive experience.


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Preoperative computerized dynamic posturography as a prognostic indicator of balance function in patients with acoustic neuroma
From Ear, Nose & Throat Journal, 3/1/05 by Eric Bergson


We conducted a study to determine the prognostic reliability of preoperative computerized dynamic posturography (CDP) in patients undergoing surgical excision of an acoustic neuroma. Our goal was to determine the correlation between objective preoperative assessments of balance function and subjective postoperative patient self-assessments. To that end, we retrospectively reviewed the records of 21 adults who had undergone preoperative CDP, and we subsequently obtained their subjective assessments of balance function by follow-up telephone surveys at least I year postoperatively. We conclude that although CDP has proven to be useful in many aspects of balance evaluation, it did not appear to be a valuable predictor of subjective postoperative balance function in these patients.


Patients who are about to undergo resection of an acoustic neuroma routinely request an assessment of their prognosis prior to surgery. Many are concerned about experiencing prolonged postoperative disequilibrium. To date, no preoperative test has proven to be a valid, reliable predictor of postoperative balance function in these patients.

Computerized dynamic posturography (CDP) has become an increasingly popular modality for evaluating balance function. Most clinicians and researchers use the equipment, protocol, and normative values developed by NeuroCom International of Clackamas, Ore., as the standard for testing and comparison.

A central aspect of the CDP protocol is the sensory organization test (SOT), which is the focus of much current research. The SOT helps the physician evaluate how visual, somatosensory, and vestibular inputs affect a patient's ability to maintain functional balance. This objective test measures the extent of a patient's sway while standing on a force platform during six conditions:

* Condition 1 is a simulation of a common, normal state. With eyes open, the patient stands on a fixed platform amid a fixed visual surround.

* In condition 2, the platform and visual surround are both still fixed, but the patient's eyes are shut.

* In condition 3, the eyes are open and the platform is fixed, but the visual surround tilts in the direction of the patient's sway, thereby delivering inaccurate visual information about orientation in space.

* Conditions 4, 5, and 6 are the same as conditions 1, 2, and 3, respectively, except that the platform moves. The sway-referenced platform tilts with the patient's sway, thereby altering somatosensory input. As a result, conditions 5 and 6 effectively force a patient to rely on vestibular inputs alone to maintain balance.

In this article, we describe our study of the reliability of preoperative CDP as a prognostic indicator of postoperative balance function in patients with acoustic neuroma. We chose subjective patient self-reports of postoperative balance function as an outcome measure because this information represents a direct assessment of how patients feel about an issue that is of primary interest to them during preoperative counseling.

Patients and methods

Twenty-one patients--8 men and 13 women, aged 30 to 71 years (mean: 53.6)--were evaluated by CDP prior to surgical removal of an acoustic neuroma. They were the first 21 patients to undergo CDP after the equipment had been acquired by the senior author (R.T.S.). The test was ordered for all patients regardless of whether or not they had expressed any preoperative complaint of dysequilibrium. The NeuroCom EquiTest equipment, protocol, and standards were used, and SOT results were analyzed for each patient. At surgery, 20 patients underwent tumor removal via a translabyrinthine approach and 1 (patient 5) via a retrosigmoid (lateral suboccipital) approach.

Subjective assessments of postoperative balance function were obtained via a telephone survey conducted no sooner than I year following surgery. The survey was conducted by the lead author (E.B.), who identified himself as a medical student working with the senior author. Patients were asked to rate their balance function on a scale of 0 to 5:

0: I have no balance problems whatsoever.

1: I feel unsteady while walking or standing.

2: I have a spinning sensation while walking or standing.

3: I fell while standing or walking because I felt off balance.

4: I am afraid to walk because I feel off balance.

5: I am wheelchair-bound because of my balance problems.


Preoperatively, abnormal CDP findings were noted in 17 of the 21 patients (81.0%); SOT conditions 5 and 6 were the most troublesome (table).

We were able to contact 19 of the 21 patients during the postoperative survey (table). Findings:

* 6 patients (31.6%) rated themselves with a score of 0.

* 8 patients (42.1%) scored 1.

* 1 patient (5.3%) scored 2.

* 3 patients (15.8%) scored 3.

* 1 patient (5.3%) scored 4.

* No patient scored 5.

Of the 3 patients who reported that they had experienced a fall, 2 were at least 60 years old and 1 had had a larger (3 to 4 cm) tumor.


Black et al studied 14 patients who had undergone unilateral vestibular surgery: 7 labyrinthectomies for Meniere's disease or endolymphatic hydrops, 4 middle fossa excisions of acoustic neuromas, and 3 vestibular nerve sections for Meniere's disease. (1) Patients were evaluated by CDP preoperatively and then at three periods ranging from 0 to 9 days, 10 to 99 days, and 100 to 999 days after surgery.

Their findings:

* Preoperatively, 5 patients (36%) exhibited CDP abnormalities during SOT conditions 5 and 6.

* At 0 to 9 days, all 14 patients (100%) exhibited abnormalities during conditions 5 and 6.

* At 10 to 99 days, 6 patients (43%) exhibited such abnormalities.

* At 100 to 999 days, only 3 patients (21%) exhibited such abnormalities.

These data show that over time, patients tended to adapt to the unilateral loss of vestibular function, and their CDP results either improved or stabilized.

Cass et al evaluated 24 patients who underwent posterior fossa vestibular nerve section for intractable vertigo caused by Meniere's disease, benign paroxysmal positional vertigo, vestibular neuritis, or perilymph fistula. (2) CDP was performed preoperatively and 1 week, 1 month, and 3 months postoperatively. Their findings:

* Preoperatively, 20 patients (83%) had abnormal preoperative CDPs.

* At 1 week postoperatively, 18 of the 24 patients were evaluated by CDP, and 8 (44%) manifested a vestibular deficit pattern with falls during SOT conditions 5 and 6.

* At 1 month, all CDP results were normal.

* However, at 3 months, 5 of the 24 patients (21%) had abnormal CDPs, including 3 whose preoperative CDPs were also abnormal.

This study showed that patients with abnormal preoperative CDPs tended to not maintain good balance function by the late postoperative follow-up.

Shepard et al studied 152 patients with varying diagnoses who were enrolled in a balance rehabilitation program. (3) They found that the results of pretherapy CDP were a reliable indicator of overall therapy outcome. Patients whose SOT patterns indicated severe vestibular dysfunction had significantly poorer posttreatment outcomes (p < 0.05).

Levine et al suggested the possibility of using preoperative CDP to determine whether acoustic neuromas smaller than 1.5 cm originate in the inferior or superior branch of the vestibular nerve. (4) In a series of 6 patients, they found that at a sway-reference gain of 1.5, patients whose neuromas originated in the inferior branch exhibited abnormalities during SOT conditions 5 and 6, whereas patients whose tumors originated in the superior branch had normal CDPs.

In our study, 81.0% of patients with acoustic neuromas had abnormal preoperative CDPs, most during SOT conditions 5 and 6. SOT conditions 5 and 6 force patients to rely on vestibular inputs for balance, even as these inputs are being compromised by the presence of their tumor. We found no correlation between the presence or severity of preoperative CDP abnormalities and postoperative balance function. Furthermore, we found no correlation between a patient's age or tumor size and postoperative balance function. The overwhelming majority of our patients scored 0 or 1 on the postoperative survey, indicating that most patients achieve and maintain adequate balance function postoperatively.

These observations are consistent with the findings of El-Kashlan et al, who used a survey to correlate preoperative symptoms with postoperative subjective balance function in 220 patients who had undergone surgical resection for acoustic neuromas. (5) They used a dizziness handicap inventory (DHI) scaled from 0 to 100, with 100 indicating the poorest balance function. The postoperative DHIs in their patients ranged from 0 to 82 (mean: 17), indicating that most patients had adequate balance function.

El-Kashlan et al also found significant correlations between postoperative balance function and several preoperative factors, including the magnitude of caloric weakness on the side of the acoustic neuroma, preoperative vestibular disability scores, abnormal positional nystagmus, abnormal vestibuloocular reflex asymmetry on rotary chair testing, and the use of postoperative vestibular habituation exercises. (5) On the other hand, they found no correlation between preoperative SOT results during CDP and various postoperative balance outcome measures.

We conclude that although CDP has proven to be useful for many aspects of balance evaluation, it does not appear to be a valuable prognostic indicator for predicting subjective postoperative balance function in patients who are about to undergo surgery for the removal of an acoustic neuroma. Although CDP probably provides an accurate reflection of the level of equilibrium problems experienced by patients, it may not reflect accurately postoperative balance function. Additional research aimed at collecting subjective and objective data from larger samples of patients should he helpful in clarifying the value of preoperative CDP in this important patient population.


(1.) Black FO, Shupert CL, Peterka RJ, Nashner LM. Effects of unilateral loss of vestibular function on the vestibulo-ocular reflex and postural control. Ann Otol Rhinol Laryngol 1989;98:884-9.

(2.) Cass SP, Kartush JM, Graham MD. Clinical assessment of postural stability following vestibular nerve section. Laryngoscope 1991;101: 1056-9.

(3.) Shepard NT, Telian SA, Smith-Wheelock M, Raj A. Vestibular and balance rehabilitation therapy. Ann Otol Rhinol Laryngol 1993;102(3 Pt 1):198-205.

(4.) Levine SC, Muckle RP, Anderson JH. Evaluation of patients with acoustic neuroma with dynamic posturography. Otolaryngol Head Neck Surg 1993:109(3 Pt 1):392-8.

(5.) El-Kashlan HK, Shepard NT, Arts HA, Telian SA. Disability from vestibular symptoms alter acoustic neuroma resection. Am J Otol 1998:19:104-11.

From the Department of Otolaryngology--Head and Neck Surgery, Albert Einstein College of Medicine, Bronx, N.Y. (Dr. Bergson), and the Department of Otolaryngology--Head and Neck Surgery, Thomas Jefferson University and Graduate Hospital, Philadelphia (Dr. Sataloff).

Reprint requests: Robert T. Sataloff, MD, 1721 Pine St., Philadelphia, PA 19103. Phone: (215) 545-3322; fax: (215) 790-1192; e-mail:

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