Acoustic neuroma overview
|
Acoustic neuroma Microchapters | |
|
Diagnosis | |
|---|---|
|
Treatment | |
|
Case Studies | |
|
Acoustic neuroma overview On the Web | |
|
American Roentgen Ray Society Images of Acoustic neuroma overview | |
|
Risk calculators and risk factors for Acoustic neuroma overview | |
Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]Associate Editor(s)-in-Chief: Simrat Sarai, M.D. [2]
Overview
Acoustic neuroma, also known as vestibular schwannoma, is a tumor that arises from the vestibulocochlear nerve (CN VIII) and represent ~80% of cerebellopontine angle masses.[1] Acoustic neuroma is a benign primary intracranial tumor of the myelin-forming cells of the vestibulocochlear nerve (8th cranial nerve).[2] Acoustic neuroma may be classified into several subtypes based on MRI scan, microscopic histopathology, and whether or not they are associated with neurofibromatosis type 2. Acoustic neuroma may be classified based on MRI scan into three subtypes: entirely canalicular, intracranial extension without brainstem distortion, and intracranial extension with brain stem distortion. Based on microscopic histopathology, acoustic neuroma may be classified into four subtypes: conventional schwannoma, cellular schwannoma plexiform schwannoma, and melanotic schwannoma.[3] Acoustic neuroma arises from Schwann cells, which are the cells that are normally involved in the conduction of nervous impulses along axons, nerve development and regeneration. On microscopic histopathological analysis, acoustic neuroma may display two types of growth patterns Antoni type A and Antoni type B.[4] Antoni type A growth pattern is composed of elongated cells with cytoplasmic process arranged in fascicles, little stromal matrix and verocay bodies. Antoni type B growth pattern is composed of loose meshwork of cells, less densely cellular matrix, microcysts and myxoid change. The majority of cases of acoustic neuroma are idiopathic.[5] Common risk factors in the development of acoustic neuroma are neurofibromatosis type 2, radiation, exposure to loud noise, history of parathyroid adenoma, and the use of cellular phones.[6]
Symptoms of acoustic neuroma include hearing loss, tinnitus, vertigo, unsteadiness, pressure in the ears, headaches and facial pain.[7] Gadolinium-enhanced MRI scan is diagnostic of acoutic neuroma. On brain MRI, acoustic neuroma is characterized by hypointense mass on T1-weighted MRI and hyperintense mass on T2-weighted MRI.[8] Head CT scan may be diagnostic of acoustic neuroma. Findings on CT scan diagnostic of acoustic neuroma include erosion and widening of the internal acoustic canal.[9] Other diagnostic studies for acoustic neuroma include audiometry, auditory brainstem response test, and electronystagmography.[10] Optimal therapy for acoustic neuroma includes observation, surgery, and radiation therapy.[11] Surgery is the mainstay of treatment for acoustic neuroma.[12]
Classification
Acoustic neuroma may be classified into three subtypes based on MRI, and into four subtypes based on microscopic histopathology.[13]
Pathophysiology
On microscopic histopathological analysis, acoustic neuroma is characterized into two types Antoni A, and Antoni B, based on growth patterns.[14]
Causes
The majority of cases of acoustic neuroma are idiopathic.[15]
Acoustic neuroma differential diagnosis
Acoustic neuroma must be differentiated from meningioma, epidermoid, facial nerve schwannoma, trigeminal schwannoma, ependymoma, leiomymoma, intranodal palisaded myofibroblastoma, malignant peripheral nerve sheath tumour(MPNST), gastrointestinal stromal tumor, neurofibroma, Meniere's disease, and Bell's palsy.[16]
Epidemiology And Demographics
The prevalence of acoustic neuroma is approximately 1 per 100,000 individuals worldwide. The incidence of acoustic neuroma is approximately 2,500 new cases per 100,000 individuals. Women are more commonly affected with acoustic neuroma than men. Aoustic neuroma commonly develops among individuals aged between the ages of 30 and 60 years.[17]
Risk Factors
Common risk factors in the development of acoustic neuroma are neurofibromatosis type 2, and radiation.
Natural History
Common complications of acoustic neuroma include hearing loss, facial numbness and weakness, difficulty with balance, ringing in the ear, hydrocephalus and recurrence of tumor. Due to improved surgical techniques and early diagnosis, the morbidity associated with surgical removal of these lesions is reduced. Acoustic neuroma patients have a very good prognosis with minimal complications if treated.[18][19][20]
History and Symptoms
Symptoms of acoustic neuroma include hearing loss, tinnitus, vertigo, unsteadiness, pressure in the ears, headaches, and facial pain.[21]
Physical Examination
Common physical examination findings of acoustic neuroma include abnormal Weber test, decreased or absent ipsilateral corneal reflex, facial twitching or hypesthesia, and abnormal caloric stimulation test.[22]
MRI
Gadolinium-enhanced MRI scan is diagnostic of acoutic neuroma. On brain MRI, acoustic neuroma is characterized by hypointense mass on T1-weighted MRI, and hyperintense mass on T2-weighted MRI. [23]
CT
Findings on CT scan diagnostic of acoustic neuroma include erosion and widening of the internal acoustic canal.[24]
Laboratory Tests
There are no diagnostic lab findings associated with acoustic neuroma.
Other Diagnostic Studies
Other diagnostic studies for acoustic neuroma include audiometry, auditory brainstem response test, and electronystagmography.[25]
Medical Therapy
Optimal therapy for acoustic neuroma includes observation, surgery, and radiation therapy.[26]
Surgery
Surgery is the mainstay of treatment for acoustic neuroma.[27]
References
- ↑ "Wikipedia acoustic neuroma".
- ↑ "Radiopedia acoustic neuroma overview".
- ↑ "Libre Pathology schwannoma acoustic neuroma subtypes".
- ↑ "Radiopedia acoustic neuroma pathology".
- ↑ "Wikipedia acoustic neuroma causes".
- ↑ "Wikipedia acoustic neuroma causes".
- ↑ "NIH Acoustic neuroma symptoms".
- ↑ "Wikipedia acoustic neuroma diagnosis".
- ↑ "Radiopedia CT findings".
- ↑ "Wikipedia acoustic neuroma diagnosis".
- ↑ "Wikipedia Acoustic neuroma treatment".
- ↑ "Wikipedia Acoustic neuroma treatment".
- ↑ "Libre Pathology schwannoma acoustic neuroma subtypes".
- ↑ "Radiopedia acoustic neuroma pathology".
- ↑ "Wikipedia acoustic neuroma causes".
- ↑ "Radiopedia Differential diagnosis of Acoustic Neuroma".
- ↑ "NIH Acoustic neuroma Incidence".
- ↑ "NIH acoustic neuroma Prognosis".
- ↑ Strasnick B, Glasscock ME, Haynes D, McMenomey SO, Minor LB (1994). "The natural history of untreated acoustic neuromas". Laryngoscope. 104 (9): 1115–9. doi:10.1288/00005537-199409000-00011. PMID 8072358.
- ↑ "NHS choices acoustic neuroma complications".
- ↑ "NIH Acoustic neuroma symptoms".
- ↑ "NIH acoustic neuroma Exam and Tests".
- ↑ "Wikipedia acoustic neuroma diagnosis".
- ↑ "Radiopedia CT findings".
- ↑ "Wikipedia acoustic neuroma diagnosis".
- ↑ "Wikipedia Acoustic neuroma treatment".
- ↑ "Wikipedia Acoustic neuroma treatment".