Response to Dr. Doan's comment on chiropractic manipulation as a treatment of hearing loss.
Dr. Doan cites the case of D.D. Palmer in September 1895 treating one Harvey Lillard for hearing loss suffered after Harvey heard a "pop" (in his back) while bending over some 17 years previously. Palmer examined Lillard, found a "lump" between his shoulders, and reasoned the lump and hearing loss were related. Palmer then administered a thoracic thrust and Harvey reported his hearing to be better.
Hearing loss can be broken into conductive or sensorineural categories. Conductive hearing loss is the disruption of sound transduction to the inner ear. It can be caused by obstruction of the ear canal, ear infection, tympanic sclerosis (ear drum scarring), or physical damage (calcification, trauma) to the the middle ear bones. Sensorineural loss is caused by insensitivity of the inner ear, most commonly noise-induced death of auditory hair cells (that's all us house rumbling ht lovers here at the shack
), or by impaired auditory processing.
The outer ear collects sound with the pinna (floppy thing with/without earrings on the side of our head) and directs it to the eardrum by the auditory canal. Sound pressure vibrates the tympanic membrane (eardrum), pushing on the malleus (1st of three middle ear bones). The middle ear uses mechanical leverage, amplifying the SPL in order to overcome loss caused by the sound-medium change from air to liquid. The stapes (last of the middle ear bones) transfers this amplified signal by pressing on the oval window (like a small eardrum) of the cochlea.
Once inside the cochlea (inner ear), the sound waves stimulate auditory hair cells which transmit their signals to the brain via the auditory portion of the vestibulocochlear nerve (VIII cranial nerve). The non-auditory portion, vestibular (balance system), is also located in the inner ear and shares the VIII cranial nerve.
The inner ear is embedded in the densest bone of our body, the temporal bone. The VIII cranial nerve runs directly from the inner ear to the brainstem (brainstem damage = vegetable
), where the auditory pathways proceed to the auditory cortex via the ventral and dorsal cochlear nuclei, superior olivary nuclear complex, inferior colliculus and the medial geniculate nucleus. It does not interact in anyway with the peripheral nerves or the spinal cord, it is a wholly "cranial" nerve, as opposed to the vagus nerve, cranial nerve X, which sends some efferents (outgoing nerve path) to the heart, lung and digestive tract (parasympathetic system).
The vestibular signals from the inner ear travel to the vestibular nuclei, located in the brainstem, via the vestibular portion of the VIII nerve. The vestibular nuclei send outputs that join with descending motor systems, and they are responsible for maintaining balance, eye tracking, head & neck position, and muscle tone. This is the system that gets messed up when you spin in circles around a bat at the office picnic party.
No chiropractic manipulation of the outer, middle or inner ear is possible, thus, ruling out chiropractic treatment of conductive hearing loss. This leaves the more complex sensorineural loss. Again, no direct manipulation of the inner ear or vestibulocochlear nerve is possible. At least not without severe pain and threat of "vegetableness."
One concept of chiropractic treatment attempts to send a signal from the location of manipulation, typically the spine, along a nerve pathway to the brain or other nervous tissue and regulate or modulate the target tissue's activities. No spinal nerve fibers make connection (input or output) with auditory processing nuclei. However, they do make connection with vestibular nuclei. As previously stated, vestibular and auditory pathways are distinct.
Therefore, only vestibular pathways could feasibly be modified by a thoracic chiropractic manipulation (thrust to the spine between your shoulder blades). So, given a balance or vertigo problem, I might be convinced that chiropractic treatment could work. As for treating hearing loss, however, chiropractic medicine only offers wishful thinking.