When it is quiet in the house, I can practically hear "a pin drop" or the sound of the cats paws walking across the kitchen floor. My hearing is very good. Most of the time.
However, as a musician, I have been exposed to enormously dangerous sound levels during various concert and rehearsal settings. Horn players often sit in front of the percussion, trumpet, or trombone sections, a situation which can lead not only to pain but to hearing loss.
When one experiences prolonged exposure to sounds greater than 85 decibels, the tiny hairs in the ear which help transmit sound can become permanently damaged. So I have had a good excuse for any "what did you say?" moments.
But I've noticed something which has changed since I developed MS. I can't hear well although I have extraordinary hearing. Doesn't make sense, I know, but it's true.
Let me describe what it feels like. Sound waves traveling through the air that reach my ears first are the sounds which I hear most prominently. If the TV is on and you want to talk to me, then you've got to talk more directly to me and much more loudly than the TV so that your voice reaches my ears first.
If the TV volume is up too loud, then I have trouble understanding what is being said. Turn the volume down to a low level and then I can hear everything It's almost as if too much aural stimulation gets garbled up in the nerves leading from my ears to my brain.
Anything which is too loud is obnoxious, confusing, and sometimes painful. Sudden, loud sounds actually do physically hurt my head. They make me jump and can cause quick muscle spasms in my torso. Other people living with MS have told me that they experience something very similar.
I don't know the reason for the pain and difficulty hearing, but I suspect that it must come down to the nerves involved in hearing.
The ear is comprised of three sections: external ear (auricle), middle ear (tympanic), inner ear (labyrinthine). The external ear functions to collect and amplify sound which is then transmitted to the middle ear. Four different nerves supply sensory information from the outer ear: the auriculotemporal nerve which is the 3rd branch of the trigeminal nerve (5th cranial nerve; the great auricular nerve that originates from the C2-3 branches of the cranial plexus; the lesser occipital nerve that originates from the C2 branch of the cranial plexus; and the auricular branch of the vagus nerve (10th cranial nerve or Arnold nerve).
Bones in the middle ear (the tympanic cavity) transfer sound waves from the outer ear to fluid contained in the inner ear. Muscles connect the three bones referred to as malleus (hammer), incus (anvil), and stapes (stirrup). Contraction of these muscles helps to prevent loud noises from injuring the inner ear. The three nerves that supply this portion of the ear include the auriculotemporal nerve, the auricular branch of the vagus nerve, and the tympanic branch of the glossopharyngeal nerve (9th cranial nerve or Jacobson nerve). According to Medscape, facial nerve paralysis can cause uninhibited movement of the stapes bone and/or tympanic membrane leading to "acuteness of hearing" and possible damage to the inner ear.
It is in the inner ear that sound is conducted to the central nervous system as acoustic (mechanical) energy is converted to electrochemical energy. The inner ear (labyrinthine cavity) is a series of bony cavities which are filled with fluid. The labyrinth includes the cochlea, vestibule, and semicircular canals. The vestibulocochlear nerve (8th cranial nerve) is the primary nerve of the inner ear.
According to NMSS, hearing loss, or impaired hearing, is an uncommon symptom of MS affecting about 6% of people with MS. As multiple sclerosis can cause lesions and disruptions of nerve signals along any nerve of the central nervous system including cranial nerves, it is not surprising that MS can affect hearing. Hearing loss may be associated with other symptoms affecting vision, balance, and equilibrium which are controlled by the brainstem. Deafness due to MS is very rare. Since the trigeminal nerve is involved in hearing, I wonder if people who have trigeminal neuralgia also experience hearing loss.
In a future post, I will review what research there has been regarding hearing loss and MS. A quick search reveals that there may be more information available than I was previously aware.
Have you noticed changes in your hearing since developing MS?
Ear Anatomy - Medscape Reference. Accessed February 14, 2013.
Hearing Loss - National MS Society. Accessed February 14, 2013.