Acoustic neuroma differential diagnosis

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2], Arash Azhideh,

Overview

Acoustic neuroma must be differentiated from meningioma, intracranial epidermoid cyst, facial nerve schwannoma, trigeminal schwannoma, ependymoma, leiomyoma, intranodal palisaded myofibroblastoma, malignant peripheral nerve sheath tumour (MPNST), gastrointestinal stromal tumor, neurofibroma, Meniere's disease, and Bell's palsy.

Differential Diagnosis

Acoustic neuroma must be differentiated from:

• Meningioma
• Intracranial epidermoid cyst
• Facial nerve schwannoma
• Trigeminal schwannoma
• Ependymoma
• Metastasis
• Leiomyoma
• Intranodal palisaded myofibroblastoma
• Gastrointestinal stromal tumor
• MPNST - schwannoma with ancient change has no significant mitotic activity
• Neurofibroma
• Meniere's disease
• Bell's palsy

Differentiating features of common differential diagnoses are:

Differentiating features of common differential diagnosis
Disease/Condition	Differentiating Signs/Symptoms	Findings on CT or MRI
Meningioma	Hearing loss is less common	Usually more homogeneous in appearance: significant signal heterogeneity with cystic or hemorrhagic areas is more typical of vestibular schwannoma than meningiomas (although cystic meningiomas do occur) Meningiomas tend to have a broad dural base Usually lack trumpeted internal acoustic meatus sign Calcification is more common
Intracranial epidermoid cyst	Hearing loss is less common	No enhancing component Very high signal on DWI (Diffusion weighted imaging) Does not widen the internal auditory canal
Facial nerve schwannoma	Facial weakness is common and occurs early Sometimes associated with neurofibromatosis	CT and MRI imaging results are similar to acoustic neuroma but enhancement extends into the geniculate ganglion of the facial nerve and facial canal
Trigeminal schwannoma	Clinically associated with facial numbness Hearing loss is less common	CT and MRI imaging display a dumbbell-shaped mass over the petrous apex affecting Meckel cave. The trigeminal nerve enhancement extends proximal to the tumor and does not extend into the internal acoustic meatus

Differential diagnosis for SSNHL:

Since the most common outcome of acoustic aeuroma is hearing loss, the differential diagnoses for SSNHL (Sudden Sensorineural Hearing Loss ) are listed below.

Identifiable Causes of Sudden Sensorineural Hearing Loss
Autoimmune	Autoimmune inner ear disease	Neurologic	Migraine
	Behcet’s disease		Multiple sclerosis
	Cogan syndrome		Pontine ischemia
	Systemic lupus erythematosis	Otologic	Fluctuating hearing loss
Infectious	Bacterial Meningitis		Meniere’s disease
	Cryptococcal meningitis		Otosclerosis
	HIV AIDS		Enlarged vestibular aqueduct
	Lassa fever	Toxic	Aminoglycosides
	Lyme disease		Chemotherapeutic agents
	Mumps		Non-steroidal anti-inflammatory drugs
	Mycoplasma infection		Salicylates
	Syphilis	Traumatic	Inner ear concussion
	Toxoplasmosis		Iatrogenic trauma/surgery
Vascular	Cardiovascular bypass		Perilymphatic fistula
	Temporal bone fracture		Cerebrovascular accident/stroke
	Sickle cell disease	Metabolic	Diabetes mellitus
Neoplastic	Acoustic neuroma		Hypothyroidism
	Cerebellopontine angle or petrous meningiomas	Functional	Conversion disorder
	Cerebellopontine angle or petrous apex metastases		Malingering
	Cerebellopontine angle myeloma

Differentiating Acoustic Neuroma from Meningioma in CT Scans

The most important differential diagnosis of acoustic neuroma is meningioma of the pontine angle. Below given diagram demonstrates the difference between acoustic neuroma and meningioma of the pontine angle based on CT scan findings:

<13cm3

Volume

>35cm3

No

Increased attenuation

Yes

No

Marked calcification

Yes

No

Oval shape

Yes

Yes

Round shape

Mostly No

Acoustic Neuroma

No

Tumor reaches dorsum sellae anteriorly

Yes

Meningioma

Mostly No

Apparently broad attachment to bone

Yes

No

Center of tumor anterior to porus

Sometimes Yes

No

Tumor reaches > 2 cm above dorsum

Mostly Yes

Sometimes

Peripheral edema

No

Mostly Yes

Widening of porus or other bone changes

No