Vestibular tumor

Template:Vestibular tumor Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] ; Associate Editor(s)-in-Chief:  Aditya Ganti M.B.B.S. [2]

## Overview

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Vestibular tumors are growths that tend to develop in or outside the auditory canal. They may be found anywhere between the chin and the larynx (or voicebox) and are not more inclined to one side of the body than the other. They are predominantly present in adolescent females though they are not directly related to any hygienal issues. While surgery is the most often cure, deaths rarely occur due to the existence of vestibular tumors.

## Historical Perspective

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The first reported case of a vestibular tumor was in 1898 in Lancaster, Pennsylvania. Though there have been stories of growths of the like of vestibular tumors, this was the first medically reported case. At the time, surgery was too dangerous, so Emilia Walfen was forced to live with the tumor, which eventually grew to the size of a Concord grape.

## Pathogenesis

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Recent studies in NF2 patients led to the identification of the neurofibromin 2 gene, which is located on chromosome 22. The NF2 gene produces merlin, also known as schwannomin, a cell membrane-related protein that acts as a tumor suppressor. Bi-allelic inactivation of the NF2 gene is found in most sporadic vestibular schwannomas.

### Microscopic pathology

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* Vestibular schwannomas arise from perineural elements of the Schwann cell.
* They occur with equal frequency on the superior and inferior branches of the vestibular nerve.
* Microscopically, zones of alternately dense and sparse cellularity, called Antoni A and B areas, respectively, are characteristic of vestibular schwannomas.
* Malignant degeneration is extremely rare, with only six cases having been reported.
* Immunohistochemical staining for S100 protein is usually positive in both the benign and the rare malignant forms of this tumor.

## Differentiating Vestibular schwannoma from other diseases

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The differential diagnosis includes meningioma, facial nerve schwannomas, gliomas, cholesterol cysts, cholesteatomas, hemangiomas, aneurysms, arachnoid cysts, lipomas, and metastatic tumor. For more information click here On the basis of seizure, visual disturbance, and constitutional symptoms, meningioma must be differentiated from oligodendroglioma, astrocytoma, hemangioblastoma, pituitary adenoma, schwannoma, primary CNS lymphoma, medulloblastoma, ependymoma, craniopharyngioma, pinealoma, AV malformation, brain aneurysm, bacterial brain abscess, tuberculosis, toxoplasmosis, hydatid cyst, CNS cryptococcosis, CNS aspergillosis, and brain metastasis.

Diseases  | Clinical manifestations | Para-clinical findings  | Gold
standard | Additional findings

|
|
|
|

Symptoms | Physical examination
Lab Findings  | MRI  | Immunohistopathology
Head-
ache  | Seizure  | Visual disturbance  | Constitutional  | Focal neurological deficit
Adult primary brain tumors
Meningioma
| \+  | +/−  | +/−  | −  | \+  | −  |

* Well circumscribed
* Extra-axial mass

* Dural attachment
* CSF vascular cleft sign
* Sunburst appearance of the vessels

* Arachnoid origin

* Psammoma bodies

* Whorled spindle cell pattern

* Biopsy

* Highest incidence is between 40 and 50 years of age.
* Most of the time, focal neurological deficit and epileptic seizure are the presenting signs.

* May be associated with NF-2

Glioblastoma multiforme
| \+  | +/−  | +/−  | −  | \+  | −  |

* Supratentorial
* Irregular ring-nodular enhancing lesions
* Central necrosis
* Surrounding vasogenic edema

* Cross corpus callosum (butterfly glioma)

* Astrocyte origin

* Pleomorphic cell

* Pseudopalisading appearance

* GFAP +

* Necrosis +

* Hemorrhage +

* Vascular prolifration +

* Biopsy

* Highest incidence in fifth and sixth decades of life
* Most of the time, focal neurological deficit is the presenting sign.

Oligodendroglioma
| \+  | \+  | +/−  | −  | \+  | −  |

* Almost always in cerebral hemisphers (frontal lobes)

* Hypointense on T1
* Hyperintense on T2
* Calcification

* Chicken wire capillary pattern

* Oligodendrocyte origin

* Calcification +

* Fried egg cell appearance

* Biopsy

* Highest incidence is between 40 and 50 years of age.
* Most of the time, epileptic seizure is the presenting sign.

Hemangioblastoma
| \+  | +/−  | +/−  | −  | \+  | −  |

* Infratentorial

* Cystic lesion with a solid enhancing mural nodule

* Blood vessel origin

* Capillaries with thin walls

* Biopsy

* Might secret erythropoietin and cause polycythemia
* May be associated with von hippel-lindau syndrome

Pituitary adenoma
[1] | −  | −  | \+ Bitemporal hemianopia | −  | −  |

* Endocrine abnormalities as a result of functional adenomas or pressure effect of non-functional adenomas

* Isointense to normal pituitary gland in T1

* Endocrine cell hyperplasia

* Biopsy

* It is associated with MEN1 disease.

* Initialy presents with upper bitemporal quadrantanopsia followed by bitemporal hemianopsia (pressure on optic chiasma from below)

Schwannoma
| −  | −  | −  | −  | \+  | −  |

* Split-fat sign
* Fascicular sign
* Often have areas of hemosiderin

* Schwann cell origin

* S100+

* Biopsy

* It causes hearing loss and tinnitus

* May be associated with NF-2 (bilateral schwannomas)

Primary CNS lymphoma
| \+  | +/−  | +/−  | −  | \+  | −  |

* Usually deep in the white matter

* Single mass with ring enhancement

* B cell origin

* Similar to non hodgkin lymphoma (diffuse large B cell)

* Biopsy

* Usually in young immunocompromised patients (HIV) or old immunocompetent person.

Childhood primary brain tumors
Pilocytic astrocytoma
| \+  | +/−  | +/−  | −  | \+  | −  |

* Infratentorial

* Solid and cystic component
* Mostly in posterior fossa
* Usually in cerebellar hemisphers and vermis

* Glial cell origin
* Solid and cystic component

* GFAP +

* Biopsy

* Most of the time, cerebellar dysfunction is the presenting signs.

Medulloblastoma
| \+  | +/−  | +/−  | −  | \+  | −  |

* Infratentorial

* Mostly in cerebellum

* Non communicating hydrocephalus

* Neuroectoderm origin

* Homer wright rosettes

* Biopsy

* Drop metastasis (metastasis through CSF)

Ependymoma
[1] | \+  | +/−  | +/−  | −  | \+  | −  |

* Infratentorial

* Usually found in 4th ventricle
* Mixed cystic/solid lesion

* Hydrocephalus

* Ependymal cell origin

* Perivascular pseudorosette

* Biopsy

* Causes an unusually persistent, continuous headache in children.

Craniopharyngioma
[1] | \+  | +/−  | \+ Bitemporal hemianopia | −  | \+  |

* Hypopituitarism as a result of pressure effect on pituitary gland

* Calcification
* Lobulated contour
* Motor-oil like fluid within tumor

* Ectodermal origin (Rathkes pouch)

* Calcification +

* Biopsy

* Initialy presents with lower bitemporal quadrantanopsia followed by bitemporal hemianopsia (pressure on optic chiasma from above)

Pinealoma
| \+  | +/−  | +/−  | −  | \+ vertical gaze palsy  |

* B-hCG rise leads to precocious puberty in males

* Hydrocephalus (compression of cerebral aqueduct)

* Similar to testicular seminoma

* Biopsy

* May cause prinaud syndrome (vertical gaze palsy, pupillary light-near dissociation, lid retraction and convergence-retraction nystagmus

Vascular
AV malformation
[1] | \+  | \+  | +/−  | −  | +/−  | −  |

* Supratentorial: ~85%
* Flow voids on T2 weighted images

* We do not perform biopsy for AVM

* Angiography

* We may see bag of worms appearance in CT angiography

Brain aneurysm
| \+  | +/−  | +/−  | −  | +/−  | −  |

* In magnetic resonance angiography, we may see aneurysm mostly in anterior circulation (~85%)

* We do not perform biopsy for brain aneurysm

* MRA and CTA

* It is associated with autosomal dominant polycystic kidney disease, Ehlers-Danlos syndrome, pseudoxanthoma elasticum and Bicuspid aortic valve
* (Angiography is reserved for patients who have negative MRA and CTA)

Infectious
Bacterial brain abscess
| \+  | +/−  | +/−  | \+  | \+  |

* Leukocytosis
* Elevated ESR
* Blood culture may be positive for underlying organism

* Central hypodense signal and surrounding ring-enhancement in T1
* Central hyperintense area surrounded by a well-defined hypointense capsule with surrounding edema in T2

* We do not perform biopsy for brain abscess

* History/ imaging

* The most common causes of brain abscess are Streptococcus and Staphylococcus.

Tuberculosis
[1] | \+  | +/−  | +/−  | \+  | \+  |

* Positive acid-fast bacilli (AFB) smear in CSF specimen
* Positive CSF nucleic acid amplification testing
* Hyponatremia (inappropriate secretion of antidiuretic hormone)
* Mild anemia
* Leukocytosis

* Hydrocephalus combined with marked basilar meningeal enhancement

* We do not perform biopsy for brain tuberculosis

* Lab data/ Imaging

* It is associated with HIV infection

Toxoplasmosis
| \+  | +/−  | +/−  | −  | \+  |

* Normal CSF

* Multifocal masses with ring enhancement
* Mostly in basal ganglia, thalami, and corticomedullary junction.

* We do not perform biopsy for brain toxoplasmosis

* History/ imaging

* It is associated with HIV infection

Hydatid cyst
[1] | \+  | +/−  | +/−  | +/−  | \+  |

* Positive serology (Antibody detection for E. granulosus)

* Honeycomb appearance
* Necrotic area

* We do not perform biopsy for hydatid cysts

* Imaging

* Brain, eye, and splenic cysts may not produce detectable amount of antibodies

CNS cryptococcosis
| \+  | +/−  | +/−  | \+  | \+  |

* Positive CSF antigen testing (coccidioidomycosis)
* CSF lymphocytic pleocytosis
* Elevated CSF proteins and lactate
* Low CSF glucose

* Dilated perivascular spaces
* Basal ganglia pseudocysts

* Soap bubble brain lesions (cryptococcus neoformans)

* We may see numerous acutely branching septate hyphae

* Lab data/ Imaging

* It is the most common brain fungal infection

* It is associated with HIV, immunosuppressive therapies, and organ transplants
* In may happen in immunocompetent patients undergoing invasive procedures ( neurosurgery) or exposed to contaminated devices or drugs
* Since brain biopsies are highly invasive and may may cause neurological deficits, we diagnose CNS fungal infections based on laboratory and imaging findings

CNS aspergillosis
| \+  | +/−  | +/−  | \+  | \+  |

* Positive galactomannan antigen testing (aspergillosis)
* CSF lymphocytic pleocytosis
* Elevated CSF proteins and lactate
* Low CSF glucose

* Multiple abscesses
* Ring enhancement
* Peripheral low signal intensity on T2

* We may see numerous acutely branching septate hyphae

* Lab data/ Imaging

* It is associated with HIV, immunosuppressive therapies, and organ transplants
* In may happen in immunocompetent patients undergoing invasive procedures ( neurosurgery) or exposed to contaminated devices or drugs
* Since brain biopsies are highly invasive and may may cause neurological deficits, we diagnose CNS fungal infections based on laboratory and imaging findings

Other
Brain metastasis
[1] | \+  | +/−  | +/−  | \+  | \+  | −  |

* Multiple lesions
* Vasogenic edema

* Based on the primary cancer type we may have different immunohistopathology findings.

* History/ imaging

* Most common primary tumors that metastasis to brain:
* Lung cancer
* Renal cell carcinoma
* Breast cancer
* Melanoma
* Gastrointestinal tract
* If there is any uncertainty about etiology, biopsy should be performed

ABBREVIATIONS

CNS=Central nervous system, AV=Arteriovenous, CSF=Cerebrospinal fluid, NF-2=Neurofibromatosis type 2, MEN-1=Multiple endocrine neoplasia, GFAP=Glial fibrillary acidic protein, HIV=Human immunodeficiency virus, BhCG=Human chorionic gonadotropin, ESR=Erythrocyte sedimentation rate, AFB=Acid fast bacilli, MRA=Magnetic resonance angiography, CTA=CT angiography

## Risk Factors

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Common risk factors for the development of vestibular schwaomas include:

* Childhood exposure to low-dose radiation for benign conditions of the head and neck
* Radiofrequency exposure from the use of mobile phones
* Excessive noise exposure

## Epidemiology and Demographics

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### Incidence

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* The overall incidence of vestibular schwannomas is approximately 1 per 100,000 person-years in the United States.
* Bilateral vestibular schwannomas are primarily observed in patients with neurofibromatosis type 2 (NF2).
* The tumors are unilateral in more than 90 percent of cases, affecting the right and left sides with equal frequency.

### Age

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* The median age at diagnosis is approximately 50 years.

### Gender

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* Vestibular schwannomas occur equally in both genders.

## Natural History, Complications, and Prognosis

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Vestibular schwanama pose a major health impediment if left untreated as they might cause pressure on adjacent posterior fossa structures such as cerebellum or brainstem and result in ataxia, brainstem compression, cerebellar tonsil herniation, hydrocephalus, and death can occur in untreated cases. Common complication include seizures and paralysis difficulty swallowing due to the pressure on the tongue or pharynx. The functions of the lower cranial nerves can also become impaired, leading to dysarthria, dysphagia, aspiration, and hoarseness.

## Diagnosis

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### History and Symptoms

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* Symptoms associated with vestibular schwannoma can be due to cranial nerve involvement, cerebellar compression, or tumor progression. Clinical manifestations in this series included the following:

Never involvement  | Incidence  | Symtpoms

|
|

Cochlear nerve | 95 percent  |

* Hearing loss

* Tinnitus

Vestibular nerve | 61 percent  |

* Unsteadiness while walking
* Brief tilting or veering

Trigeminal nerve | 17 percent  |

* Facial numbness (paresthesia), hypesthesia, and pain.

Facial nerve | 6 percent  |

* Facial paresis
* Taste disturbances (due to nervus intermedius impairment).
* Xerophthalmia
* Paroxysmal lacrimation
* Xerostomia

Tumor progression  |  |

* Pressure on adjacent posterior fossa structures such as cerebellum or brainstem and result in ataxia
* Brainstem compression, cerebellar tonsil herniation, hydrocephalus, and death can occur in untreated cases

### Physical Examination

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* Hearing tests are typically abnormal due to involvement of the acoustic nerve.
* The Weber and Rinne tests may be useful in suggesting asymmetric sensorineural hearing impairment.

* Neurologic examination may reveal other cranial nerve deficits
* A decreased or absent ipsilateral corneal reflex and facial twitching or hypesthesia may occur as cranial nerves V and VII become affected.
* Romberg, Hall-Pike, and other common office balance tests are typically normal.

### CT

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Findings of vestibular schwanoma on CT include:

* Erosion and widening of the internal acoustic canal.
* The density of these tumors on non-contrast imaging is variable, and often they are hard to see, especially on account of beam hardening and streak artefact from the adjacent petrous temporal bone.

* Contrast enhancement is present but can be underwhelming, especially in larger lesions with cystic components.

### MRI

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MRI findings of vestibular schwanoma include:

MRI findings of Vestibular Schwanoma

T1 |

* Slightly hypointense to the adjacent brain.
* Isointense to the adjacent brain
* May contain hypointense cystic areas

T2 |

*     * Heterogeneously hyperintense to adjacent brain
* Fluid intensity cystic areas
* May have associated peritumoral arachnoid cysts

T1 C+ (Gd) | Contrast enhancement is intense however, heterogeneous in larger tumors

### Other Diagnostic Studies

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Audiometry

* Audiometry is the best initial screening laboratory test for the diagnosis of vestibular schwannoma.
* Pure tone and speech audiometry should be performed in an acoustically shielded area.
* Test results typically show an asymmetric sensorineural hearing loss, usually more prominent in the higher frequencies.
* Hearing loss does not necessarily correlate with tumor size.
* The speech discrimination score is usually markedly reduced in the affected ear and out of proportion to the measured hearing loss.
* Common audiometry tests that are of current practice include:
* Acoustic reflex testing
* Impedance audiometry
* Bekesy audiometry
* Brainstem-evoked response audiometry (AER/ABR).

Vestibular testing

* Vestibular testing has limited utility as a screening test for the diagnosis of vestibular schwannoma because of the accuracy of evoked response audiometry.
* When testing is performed, a decreased or absent caloric response on the affected side may be seen. When the tumor is small, though, a normal response is often seen.

*     *     *

## Treatment

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Treatment options for patients with a vestibular schwannoma include surgery and radiation therapy.

### Surgery

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Surgery generally results in satisfactory long-term control of vestibular schwannomas. There are three standard operative approaches.

Surgery

Retromastoid suboccipital (retrosigmoid)  | The suboccipital approach can be used for any size tumor with or without attempted hearing preservation.
Translabyrinthine  | The translabyrinthine approach has been recommended for acoustic tumors larger than 3 cm and for smaller tumors when hearing preservation is not an issue.
Middle fossa  | The middle fossa approach is suitable for small (<1.5 cm) tumors when hearing preservation is a goal.

### Radiation therapy

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Radiation therapy for patients with vestibular schwannoma include stereotactic radiosurgery (SRS), stereotactic radiotherapy (SRT), and proton beam therapy, as well as conventional fractionated radiation therapy.

Radiation therapy

Stereotactic radiosurgery |

* SRS is a technique that utilizes multiple convergent beams to deliver a high single dose of radiation to a radiographically discrete treatment volume, thereby minimizing injury to adjacent structures.
* This can be accomplished with either the gamma knife or a linear accelerator.
* Radiosurgery is a viable treatment option for selected patients with smaller tumors (<3 cm) or for enlarging tumors in patients who are not candidates for surgery

Stereotactic radiotherapy |

* Fractionated SRT utilizes focused doses of radiation given over a series of treatment sessions.
* The intent is to reduce radiation injury to critical neural structures while preserving tumor control.

Proton beam therapy |

* Proton beam therapy may provide maximal local tumor control while minimizing cranial nerve injuries.
* The physical characteristics of the beam result in the majority of the energy being deposited at the end of a linear track (the Bragg peak), with the dose falling rapidly to zero beyond the Bragg peak.
* Thus, the use of proton beam therapy permits the delivery of high doses of radiation therapy to the target volume while limiting the "scatter" dose received by surrounding tissues.

## References

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