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The nerve from the ear to brain

20 April 2010 No Comment
This colour enhanced axial cross sectional MRI image beautifully demonstrates the 7th and 8th cranial nerve complexes within the internal auditory canals (IAC). This MRI sequence is called a CISS sequence and is a highly specialized sequence to look at these nerves when people have complaints of hearing loss. Sometimes hearing loss is the result of a tumor involving the 8th nerve in the internal auditory canal which is called a vestibular schwannoma or acoustic neuroma. MRI is the best method to diagnose this problem.  Living Art Enterprises, LLC/ Science Photo Library

This colour enhanced axial cross sectional MRI image beautifully demonstrates the 7th and 8th cranial nerve complexes within the internal auditory canals (IAC). Living Art Enterprises, LLC/ Science Photo Library

We are continuing on in our series of posts on the normal ear and balance system. Last time I talked about the Balance Parts of the Normal Inner Ear.  This time I’ll briefly talk about the nerve connecting the ear and the brain.

The nerve is called the Vestibulocochlear nerve and contains parts for both hearing (cochlear) and balance (vestibular).  It runs from the inner ear, throug the skull.  In the skull it passes through a passage called the internal auditory meatus.  As it passes through here is is susceptible to compression from tumours and things called arteriovenous malformations (blood vessel growths).

The most common type of tumour is one called an acoustic neuroma.  These are a very slow growing tumour (10 to 25 years is not uncommon).  Their slow growth can mean that they show very few signs.  MRI scans are the best way to diagnose them.  Overall though they are not very common.

Once on the inside of the skull the nerve joins up with the brain at a region called the pontomeduallary junction in the brainstem (the base of the brain).  Where it goes from there is the subject of the next post.

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