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Acoustic Neuroma

Acoustic Neurinoma

Acoustic neuroma is a rare tumor that originates from the Schwann cells of the eighth cranial nerve, also known as vestibulocochlear nerve. This condition is characterized by unilateral hearing loss but has other sequelae as well.


Presentation

Acoustic neuromas are unilateral in greater than 90% of patients [1]. The bilateral cases are confined to neurofibromatosis type 2 [7].

The most common presenting feature in acoustic neuroma is the unilateral sensorineural hearing loss, which is slow and gradual in the majority of patients. This occurs secondary to either vascular insufficiency or direct injury to the cochlear nerve. The hearing deficit can be sudden or it can fluctuate depending on cochlear perfusion and its interruption. Some patients may recover their hearing spontaneously. Note that hearing impairment is not related to the size of the acoustic neuroma.

Unilateral tinnitus very often coexists with hearing loss. Although if present alone, the presence of tinnitus should prompt suspicion for acoustic neuroma.

The majority of patients will have low speech discrimination scores as displayed on audiological tests. According to one study, almost 65% of individuals demonstrated a link between hearing loss severity and reduced speech discrimination [8].

Approximately half of acoustic neuroma patients will experience balance disturbance although vertigo and disequilibrium are not present initially.

At least half of the patients exhibit headaches especially in cases with growing tumors and those with obstructive hydrocephalus.

Another manifestation is facial numbness, which is exhibited in approximately 25% of patients. Up to 70% of those with large tumors exhibit hypoesthesia on exam but are not aware of it.

Facial weakness is rare and should prompt investigation of differential diagnoses such as arteriovenous malformation (AVM), meningioma, hemangioma, and facial neuroma.

Impaired Balance
  • Although acoustic neuromas mostly originate from the upper part of the balance nerve, vertigo and impaired balance rank only in third place as a symptom of an acoustic neuroma.[acoustic-neuroma-brain-tumour.org]
Lymphedema
  • The patient had chronic difficulty with left-sided lymphedema, requiring frequent manual lymphatic drainage.[ncbi.nlm.nih.gov]
Rhinitis
  • No significant associations were found between acoustic neuroma and history of any allergic diseases, such as asthma, eczema, and seasonal rhinitis.[ncbi.nlm.nih.gov]
Diarrhea
  • One patient sustained temporary palsy of the vocal fold and another reported antibiotic-associated diarrhea. CONCLUSION: Acoustic neuroma surgery via the MFA can be conducted with low morbidity and mortality.[ncbi.nlm.nih.gov]
Venous Insufficiency
  • A limited AICA syndrome caused by loss of its distal ramifications seems a more plausible explanation for peduncular infarction than either venous insufficiency or direct surgical trauma.[ncbi.nlm.nih.gov]
Tinnitus
  • […] without preoperative tinnitus.[ncbi.nlm.nih.gov]
  • […] of posttreatment tinnitus distress.[ncbi.nlm.nih.gov]
  • Of these, 71.8% suffered from tinnitus: 50% grade I, 17.9% grade II, 10.7% grade III, 21.4% grade IV and 0% grade V. We found no statistical association between tinnitus and the different variables measured preoperatively.[ncbi.nlm.nih.gov]
  • OBJECT: Tinnitus is a known presenting symptom of acoustic neuromas, but little is known about the impact of observation or treatment on tinnitus. Most patients experience improvement with treatment, while others may worsen.[ncbi.nlm.nih.gov]
  • RESULTS: Of the 53 patients who completed the survey, 17% reported that their tinnitus resolved; 9% reported improvement; 23% reported no change; 43% reported that their tinnitus worsened; and 8% were unsure.[ncbi.nlm.nih.gov]
Sudden Hearing Loss
  • A 15-year-old boy experienced a sudden hearing loss in the left ear.[ncbi.nlm.nih.gov]
  • Two patients had normal hearing function but reported tinnitus; two patients reported sudden hearing loss, with partial recovery; two patients had a history of fluctuating hearing loss; two patients reported neurologic symptoms (one reported trigeminal[ncbi.nlm.nih.gov]
  • Acute acoustic and blast trauma and coexisting acoustic neuroma (AN) contributed to, and mutually modified, the course of sudden hearing loss.[ncbi.nlm.nih.gov]
  • Less than 2% of patients presenting with sudden hearing loss will ultimately prove to have an AN. Other forms of hearing loss are relatively frequent.[hopkinsmedicine.org]
Hearing Impairment
  • OBJECTIVE: In patients with acoustic neuroma, the site and severity of hearing impairment are important in discussing surgical approaches.[ncbi.nlm.nih.gov]
  • It would be pointed out that the delayed facial plasy has favourable prognosis, while the hearing impairment may recover with a greater difficulty even after an antiviral treatment as in our case.[ncbi.nlm.nih.gov]
  • Early symptoms include mild unilateral hearing impairment , tinnitus (ringing in the ear), and sometimes dizziness.[britannica.com]
  • Unilateral hearing impairment should warrant a high index of suspicion for acoustic neuroma.[symptoma.com]
  • Hearing Impairment and Acoustic Neuromas The natural course of an untreated acoustic neuroma is hearing loss in the affected ear. Surgery or radiosurgery can also result in hearing loss. Many patients adjust well to hearing in only one ear.[utswmed.org]
Hearing Problem
  • If your GP thinks you could have an acoustic neuroma, you'll be referred to a hospital or clinic for further tests, such as: hearing tests to check for hearing problems and determine whether they're caused by a problem with your nerves an MRI scan , which[nhs.uk]
  • If your GP thinks you could have an acoustic neuroma, you'll be referred to a hospital or clinic for further tests, such as: hearing tests to check for hearing problems and determine whether they're caused by a problem with your nerves a magnetic resonance[nhsdirect.wales.nhs.uk]
  • Those affected often notice the hearing problem very late or by chance, for example when telephoning or during a routine examination.[acoustic-neuroma-brain-tumour.org]
Pulsatile Tinnitus
  • The typical presentation is with adult-onset sensorineural hearing loss or non-pulsatile tinnitus . In some patients, this goes unnoticed, and presentation is delayed until the lesion is much larger and presents with symptoms related to mass effect.[radiopaedia.org]
Psychiatric Symptoms
  • Facial palsy caused by microsurgery treatment may be a key factor triggered and involved in the psychiatric symptoms and clinicians must be aware that early involvement of a clinical psychologist may be very helpful.[ncbi.nlm.nih.gov]
Facial Numbness
  • However, there was a significantly higher incidence of facial numbness and diminished facial sensation, but not facial weakness, compared with the whole series.[ncbi.nlm.nih.gov]
  • Five-year actuarial rates for any new facial weakness, facial numbness, hearing-level preservation, and preservation of testable speech discrimination were 1.1 0.8%, 2.6 1.2%, 71 4.7%, and 91 2.6%, respectively.[ncbi.nlm.nih.gov]
  • Symptoms that worsened or newly developed following SRT in this series were deafness (41%), dizziness (35.9%), facial numbness (25.6%), tinnitus (20.5%), facial nerve palsy (7.7%), and facial pain (7.7%).[ncbi.nlm.nih.gov]
  • As it grows, an acoustic neuroma can produce a number of characteristic clinical features, such as: Hearing loss Tinnitus (ringing in the ear) Dizziness Facial numbness (when the tumour is 2.5cm ) Severe imbalance, headaches, nausea, facial weakness ([sunnybrook.ca]
  • Symptoms include loss of hearing, tinnitus (buzzing or ringing in the ear), dizziness/loss of balance, facial numbness, facial weakness or paralysis on the side of the tumor. Early detection of the tumor is sometimes difficult.[ugr.es]
Facial Pain
  • Two (5.1%) patients with slight increase of the mass underwent surgical resection because of development of unbearable facial pain.[ncbi.nlm.nih.gov]
  • The larger end of the “pear” may compress the trigeminal nerve, causing facial pain. It may also compress the brainstem and cerebellum, causing hydrocephalus or interfering with vital functions.[columbianeurosurgery.org]
  • Physicians may choose surgery for people with large tumors or tumors that are causing serious problems with balance; persistent headaches or facial pain; or hydrocephalus , a buildup of fluid in the brain.[nyulangone.org]
Headache
  • We classified postoperative headache as grade 0 (no headache), 1 (tolerable headache without medication), or 2 (headache requiring medication). The period of headache was defined as the interval in days between surgery and achievement of grade 0.[ncbi.nlm.nih.gov]
  • These findings suggest that patients presenting with chronic postoperative headache should be screened for the presence of surgically treatable occipital nerve injuries. 2012 American Headache Society.[ncbi.nlm.nih.gov]
  • Headache. 2009 Feb;49(2):302-3. doi: 10.1111/j.1526-4610.2008.01145.x. Epub 2008 Jun 11. Author information 1 Thomas Jefferson University Hospital, Jefferson Headache Center, Philadelphia, PA 19107-2060, USA.[ncbi.nlm.nih.gov]
  • […] total symptoms, and higher headache severity scores (p CONCLUSIONS: Non-elderly acoustic neuroma patients with larger tumors, growing tumors, significant hearing loss, and worse headaches are more likely to pursue surgical resection rather than active[ncbi.nlm.nih.gov]
  • Abstract A 47 year old man developed severe headaches after resection of an acoustic neuroma ipsilateral to non dominant venous drainage.[ncbi.nlm.nih.gov]
Dizziness
  • Patients with vertigo or dizziness experienced a poorer QoL according to the SF-36 (Social Functioning and Emotional Role Limitation dimensions) and to the PANQOL scale (Balance and Energy dimensions).[ncbi.nlm.nih.gov]
  • METHODS: A 60-year-old woman was investigated for recent onset of acute dizziness. Laboratory and radiographic investigations are presented, as well as the surgical management of the patient and pathological examination of the aneurysm.[ncbi.nlm.nih.gov]
  • The majority of respondents reported functional impact attributed to hearing loss, balance disturbance, dizziness, eye problems, headache and fatigue; balance disturbance was the symptom most often reported to have a severe functional impact.[ncbi.nlm.nih.gov]
  • The reported clinical symptoms of the acoustic neuroma are hearing deficits (60 to 97%), tinnitus (50 to 66%), vestibular disturbances (46 to 59%), numbness or tingling in the face (33%), headache (19 to 29%), dizziness (23%), facial paresis (17%), and[ncbi.nlm.nih.gov]
  • METHODS: Thirty-eight patients were tested using caloric irrigation, static posturography, and the Dizziness Handicap Inventory (DHI) before, and one week to nine months after surgery.[ncbi.nlm.nih.gov]
Vertigo
  • Of the 178 patients studied, only 10 had both cystic change of the tumor and rotatory vertigo, and 120 had neither cystic tumor nor rotatory vertigo.[ncbi.nlm.nih.gov]
  • The vertigo of the vestibular schwannoma patients differed from vertigo in other diseases by the absence (63%) or low intensity (18%) of nausea.[ncbi.nlm.nih.gov]
  • Hyperventilation is a simple bedside test that should be performed when assessing a subject with vertigo or when there is a clinical suspicion of an acoustic neuroma.[ncbi.nlm.nih.gov]
  • Patients with vertigo or dizziness experienced a poorer QoL according to the SF-36 (Social Functioning and Emotional Role Limitation dimensions) and to the PANQOL scale (Balance and Energy dimensions).[ncbi.nlm.nih.gov]
  • Abstract A 55-year-old man with hearing loss presented with vertigo and vomiting. CT tomography and MRI demonstrated a cerebellopontine angle mass with foci of haemorrhage.[ncbi.nlm.nih.gov]
Ataxia
  • Abstract A 22-year-old male with unilateral facial, cochlear and glossopharyngeal cranial nerve dysfunction and ataxia that was slowly progressive over one year is described.[ncbi.nlm.nih.gov]
  • Examination revealed mild ataxia, which led to repeat magnetic resonance imaging (MRI) and a diagnosis of cerebellar abscess.[ncbi.nlm.nih.gov]
  • Although little information is available on its exact incidence, truncal (trunk, abdomen, chest) ataxia appears to be more common than limb ataxia.[hopkinsmedicine.org]
  • […] tinnitus) the sensation that you're moving or spinning (vertigo) A large acoustic neuroma can also sometimes cause: persistent headaches temporary blurred or double vision numbness, pain or weakness on 1 side of the face problems with limb co-ordination (ataxia[nhs.uk]
Nystagmus
  • Hyperventilation for 30 seconds provoked an ipsilateral beating nystagmus and reproduced the vertiginous sensation in both subjects.[ncbi.nlm.nih.gov]
  • Twenty-six patients with unilateral acoustic neuroma (mainly intracanalicular type) were studied with a full audio-vestibular test battery (pure tone and speech audiometry, caloric bithermal test, vibration-induced nystagmus test (VIN), cervical and OVEMPs[ncbi.nlm.nih.gov]
  • Spontaneous nystagmus was present in 56 patients (46%), and caloric asymmetry ( 25%) was observed in 66% (n 69). Caloric asymmetry increased with tumor size. The prevalence of headache was 18% (n 21). Sudden slips seldom (7%) occurred.[ncbi.nlm.nih.gov]

Workup

Individuals presenting with unilateral sensorineural hearing deficits should be presumed to have an acoustic neuroma. The diagnosis should be confirmed through evaluation of the clinical picture, history, a physical exam with focus on hearing and neurologic assessment, and imaging studies.

Imaging

The confirmatory imaging modality is the gadolinium-enhanced MRI, which detects small lesions measuring 1 to 2mm in diameter. This is contraindicated in patients with ferromagnetic implants. Adding a fast-spin echo feature to MRI imaging is rapid and inexpensive but is ineffective in diagnosing differentials such as demyelinating disease. Fine-cut CT with contrast can identify medium or large tumors in the internal auditory canal but fail to discover lesions less than 1 to 1.5cm.

Histology

Histologic analysis of tissue samples of portrays characteristic histologic findings. There are two types of tissues: Antoni A and Antoni B. The former exhibits a pattern of spindle cells with palisading nuclei referred to as Verocay bodies while the latter displays loose stroma with fewer cells.

Other

While previously common, audiometric studies are not used for diagnostic purposes anymore.

Hyponatremia
  • RESULTS: Wrong diagnosis in case of central nervous system disorder associated with hyponatremia can have fatal consequences.[ncbi.nlm.nih.gov]

Treatment

The are three main therapeutic approaches in the treatment of acoustic neuroma which include observation, stereotactic radiation therapy, and surgical removal of the lesion.

When deciding the best course of management, the medical team should assess numerous factors [9] such as the parent's hearing status, the size and growth rate of the tumor, the patient's life expectancy, the probability of developing facial nerve paralysis, and the risks of surgery. The latter includes outcomes such as hearing loss and other postsurgical complications. Another variable for consideration is whether the patient has NF2.

Observation

These tumors are typically benign and slow growing. Therefore, careful observation is appropriate for those with small tumors, particularly in the elderly. Groups who are good candidates for observation are the elderly, those with comorbid medical conditions that render them risky for surgery, and patients with the tumor presenting on the side of the unaffected ear. Furthermore, patient preference may favor observation.

Studies have indicated that up to 40% of patients under observation will eventually warrant intervention and many will become ineligible for surgery during this time period.

Stereotactic radiotherapy

As an alternative to microsurgery, this treatment modality applies radiation to target tissues hence minimizing the potential exposure to nearby tissues. The goals of radiation are to inhibit the growth of the tumor cells and to obliterate the lesion's vascular perfusion. One study reported that Gamma Knife radiation is effective in tumor control [10]. although another investigation observed that these tumors are resistant to low dose radiation [11].

Surgery

Surgical excision is the preferred treatment for the elimination of acoustic neuroma. There are numerous techniques that may be utilized depending on the surgeon's technical skills, size and location of the tumor, and the desire for hearing preservation.

When choosing between radiation and microsurgery, there are many variables to be considered such as postsrgical morbidity and mortality, hospital length of stay and cost, etc.

Follow-up

The patient is monitored with periodic imaging studies and hearing tests.

Prognosis

The prognosis can be evaluated by the outcome of each symptom. For example, cases with hearing preservation have been noted to increase during the last decade. It is likely that post-radiation and post-surgical patients have similar rates of conservation. However, hearing impairment has been observed in patients who underwent surgery.

Although tinnitus may improve after surgery, it can actually worsen in a minority of patients. Furthermore, it may develop postoperatively as well. The post-surgical recurrence rate of acoustic neuroma is less than 5%. Note that patients may have residual tumor since intraoperative visualization is quite challenging in many cases.

Rehabilitation

Hearing loss following surgical resection may require rehabilitation such as the bone-anchored hearing aid (BAHA) or contralateral routing of signals (CROS) hearing aid. Additionally, patients with post-surgical facial weakness warrant artificial tears and other eye care products until the nerve recovers. Generally, facial nerve recovery is associated with tumors that are smaller than 1.5cm. Moreover, the utilization of intraoperative facial nerve monitoring may lead to the improvement of function.

Etiology

The major known risk factor for developing an acoustic neuroma is high-dose ionizing radiation, although the majority of affected individuals do not have apparent risk factors. Some studies suggest that exposure to loud noise [1] [2] and nonmedullary thyroid cancer [3] may be risk factors for developing this tumor.

Neurofibromatosis type 2

Acoustic neurofibroma is the major clinical feature of the genetic disorder, neurofibromatosis type 2, which is the result of a mutation of a tumor suppressor gene that is found on chromosome 22.

Epidemiology

The incidence of acoustic neuroma is 1 per population of 100,000 annually. The incidence is rising which may be explained by the widespread utilization of various imaging modalities such as MRI and computed tomography (CT), leading to a higher number of incidental diagnoses [4] [5]. The prevalence in the population is likely higher according to autopsy studies [6] [7].

With regards to patient demographics, the median age at diagnosis of the condition is about 50 years old [5]. This tumor comprises almost 8% of adult intracranial tumors and at least 80% of cerebellopontine tumors.

Sex distribution
Age distribution

Pathophysiology

Acoustic neuromas are benign, slow growing, and noninvasive. They rarely undergo malignant transformation. Additionally, there are three distinct patterns of growth as some will remain dormant, while others may grow slowly or rapidly. While most are slow growers, tumors may erratically alternate between these patterns.

Location of tumor and symptomatology

In addition to its size, the tumor is also characterized by its location. It may develop in the auditory canal and expand into the cerebellopontine angle. The symptoms result from the compression of nerves, vessels, spinal fluid spaces, as well as the displacement of the brain stem.

Most of acoustic neuromas arise from Schwann cells located on the vestibular segment of the vestibulocochlear nerve. When these tumors compress the vestibular fibers, the resultant damage ensues in a gradual and slow manner. Therefore, vertigo is not a prominent feature.

Note that lesions emerging in the internal auditory canal may compress and impinge upon the vestibular nerve, cochlear nerve, or labyrinthine artery. These mechanisms result in hearing loss and vestibular disturbance.

When these tumors grow, they may extend into the cerebellopontine angle, which is an empty space that contains spinal fluid. Larger lesions can compress other cranial nerves, impinge on neighboring structures, and shift the position of the brain stem. If greater than 4cm, they cause hydrocephalus.

Prevention

There are no preventative measures. However, it is important for patients with hearing loss to seek medical care in a timely manner.

Summary

Acoustic neuroma, also referred to as vestibular schwannoma, is a benign tumor that derives from the Schwann cells of the vestibulocochlear nerve. Specifically, the vestibular branch of the nerve accounts for almost all cases of this condition. Most tumors are slow growing and some can expand from the internal auditory canal to the cerebellopontine angle. If the lesion enlarges, it may encompass the brainstem, cerebellum, and compress other cranial nerves. The etiology is unknown but there are potential risk factors.

The chief symptom at initial presentation is the unilateral sensorineural hearing loss. Other symptoms that develop as the tumor progresses include tinnitus, disequilibrium, headache, and other abnormalities that reflect affected anatomic structures.

Unilateral hearing impairment should warrant a high index of suspicion for acoustic neuroma. The workup consists of a detailed assessment of the patient's clinical picture and history, a physical examination with a hearing evaluation, and imaging tests. Due to the availability of gadolinium-enhanced magnetic resonance imaging (MRI), the detection of acoustic neuromas is on the rise.

Patients with acoustic neuroma can be managed by observation, radiation therapy, or microsurgery. The appropriate treatment depends on variables such as the size, location, and growth rate of the tumor, as well as the patient's age, comorbid medical issues, and patient preference.

Patient Information

What is an acoustic neuroma?

This is a rare tumor that grows on the cranial nerve called vestibulocochlear nerve which travels from the brainstem to the ear canal. Specifically, this nerve is responsible for hearing and balance maintenance. The exact cause of this condition is unknown.

This benign tumor rarely becomes cancerous. Also, most are slow growing and non-invasive.

What are the risk factors for developing this condition?

Exposure to loud noise may increase the probability of developing acoustic neuroma. Also, having a personal or family history of neurofibromatosis type 2 (NF2) may also be a risk factor.

What are the signs and symptoms?

Although this is a benign tumor, it can cause serious problems for the patient. Early signs and symptoms are as follows:

  • Hearing loss in one ear (while the other ear is normal)
  • Tinnitus: ringing in the same ear as hearing loss
  • Difficulty with discriminating between sounds

The growing neuroma can cause:

How is it diagnosed?

The clinician will assess the patient's symptoms, obtain the medical history, perform a physical exam and a detailed hearing evaluation. Also, imaging tests such as the following will be ordered:

  • MRI
  • CT scan

How is it treated?

The medical team will choose the most appropriate treatment by considering factors such as the size, location, and growth of the acoustic tumor. Also, the patient's age, overall health, and preference will also be important factors. There are 3 main options for treatment:

  1. Observation: small tumors can be monitored, especially in the elderly
  2. Radiation: this kills tumor cells and prevents further growth. It is an option for small tumors that are difficult to operate on.
  3. Surgical removal of the tumor: this is warranted when the tumor grows and hearing loss occurs. There are complications such as deafness and paralysis of the muscles on the face.

The patients will follow-up with their doctor and undergo periodic imaging and hearing tests.

What is the prognosis?

The probability of the tumor recurring after surgery is less than 5%.

Hearing may be preserved in patients who have undergone surgery as well as those who received radiation. However, hearing loss may occur after surgery as well.

References

Article

  1. Edwards CG, Schwartzbaum JA, Lonn S, et al. Exposure to loud noise and risk of acoustic neuroma. American Journal of Epidemiology. 2006;163(4):327–333.
  2. Preston-Martin S, Thomas DC, Wright WE, et al. Noise trauma in the aetiology of acoustic neuromas in men in Los Angeles County, 1978–1985. British Journal of Cancer. 1989;59(5):783–786.
  3. Hemminki K, Eng C, Chen BW. Familial risks for nonmedullary thyroid cancer. Journal of Clinical Endocrinology and Metabolism. 2005;90(10):5747–5753.
  4. Lin D, Hegarty JL, Fischbein NJ, et al. The prevalence of "incidental" acoustic neuroma. Archives of Otolaryngology - Head and Neck Surgery. 2005; 131(3):241-4.
  5. Propp JM, McCarthy BJ, Davis FG, et al. Descriptive epidemiology of vestibular schwannomas. Neuro-Oncology. 2006;8(1):1-11.
  6. Tos M, Stangerup SE, Caye-Thomasen P, et al. What is the real incidence of vestibular schwannoma?. Archives of Otolaryngology - Head and Neck Surgery. 2004;130(2):216-20.
  7. Eldridge R, Parry D. Vestibular schwannoma (acoustic neuroma). Consensus development conference. Neurosurgery 1992;30(6):962.
  8. Lee SH, Choi SK, Lim YJ, et al. Otologic manifestations of acoustic neuroma. Acta Oto-Laryngologica. 2015;135(2):140-6.
  9. Telian SA. Management of the small acoustic neuroma: a decision analysis. American Journal of Otolaryngology 1994; 15(3):358-65.
  10. Boari N, Bailo M, Gagliardi F, et al. Gamma Knife radiosurgery for vestibular schwannoma: clinical results at long-term follow-up in a series of 379 patients. Journal of Neurosurgery. 2014; 121 Suppl:123-42.
  11. Hansen MR, Clark JJ, Gantz BJ, et al. Effects of ErbB2 signaling on the response of vestibular schwannoma cells to gamma-irradiation. Laryngoscope. 2008 Jun; 118(6):1023-30.

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Last updated: 2018-06-22 08:06