Greetings PRI Community,
I recently received an inquiry from a fellow PRI colleague who was unable to attend this past spring's symposium on the auditory system. The question related to the reasoning behind why one of his client's hearing improved despite a diagnosis of otosclerosis and accompanying prognosis that did not include the ability to get better. Below is my response that I thought was worth sharing with the rest of the PRI community. It was also posted on the Postural Restoration Google Group. If you are not yet a member of this group of practitioners where we have a forum to discuss PRI related topics please email me at HeatherCarrDPT@gmail.com to join.
Our ability to "hear" is determined by a number of factors but here are the ones that are applicable to position and movement from a PRI perspective.
The inner ear is composed of the cochlea (frequency/sound analyzer) and the vestibule (motion/position analyzer). Our cochlea receives auditory afferent sensory input via sound conduction through the air but also via our bones. The latter is particularly important in relaying the true fundamental tones of sound back to the nervous system. When our bones do not vibrate appropriately it is difficult for us to perceive authentic sound characteristics. The vibrations created by the larynx are transferred to the spine and cranial bones providing important auditory afferentation.
Our middle ear is composed of 3 vibrating ossicles (hammer, anvil, stirrup in order from outer to inner) which transmit sound from the outer ear to the inner ear. Therefore, proper vibrational capability of these bones is important for sound conduction. There are two muscles within this complex. The tensor tympani is attached to the hammer and is a flexor. The stapedius is attached to the stirrup and is an extensor. Consistent with PRI's functional perspective of poly-articular chains of muscle, these muscles can also be included in these neuromuscular synergies. Therefore, if there is an excessive degree of extensor facilitation in the the body it will likely translate to the stapedius exhibiting hypertonicity. Likewise, stapedius hypertonicity can impact the rest of the postural extensor system. The same may apply with the tensor tympani. This could be extrapolated a step further when considering the asymmetrical tendencies of the cranial system (R typically more in extension and the L typically more in flexion). Therefore, when the system is not able to spend time in neutrality, it will likely have difficulty producing appropriate neuromuscular tone thus impacting position and vibrational capability of the skeletal system.
The position of the larynx is important for sound generation and that forward head patterns, as described in Cervical Revolution, will negatively impact its ability to properly posture and thus vibrate appropriately. Furthermore, the length/tension relationships of the surrounding laryngeal musculature, ligaments, and tendons are concurrently providing additional somatosensory information also contributing to auditory perception. If these relationships are inefficient so will the corresponding sensory input.
Let's take this a step further and remember that a huge contributor to the position of the neck is the position and poly-articular patterning coming from the thorax/diaphragm and pelvis. Our diaphragm position exerts signficant control over the exhalation power behind the voice.
In summary, our bodies need to have the ability to vibrate. If one is locked into asymmetrical or bilateral patterns that do not allow appropriate range of movement, one's resonance is dampened. This will reduce important sensory input to the system further contributing stress as sensory deficits are ultimately stressors.