Occlusion effects -the neural challenges

OCCLUSION EFFECTS—THE NEURAL CHALLENGES

• There remain those cases in which occlusion is reduced--almost to the point of elimination--with reported problems of "feeling plugged" still occurring.

• Such instances fall into the category termed here as the "non-acoustic/neural occlusion effect".


The “non-acoustic/neural occlusion effect” is defined as the sensation of stimuli in parts of the body at or away from the ears while wearing hearing instruments, whether amplification is operational or not.


• Non-acoustic/neural occlusion is believed to be caused by the pressure of acoustic coupling shells against the nerves of the outer ear.

• Its effects in individual cases are important to understand, as it may involve both cranial and cervical nerves.


Signs of Neural OcclusionReports of headaches, nausea, numbness, pressure, tension, pain, tearing in the eyes, running noses, tingling sensations, soreness, hoarseness, sore throat, changes in breathing, blood pressure, heart rate, and feelings of being "plugged up" while wearing vented hearing instruments, may be suspect signs of neural occlusion.


• The literature on the nerve endings found in and around the outer ear reveals numerous discrepancies in location of individual nerves.

• This fact demonstrates the broad variability in final development of the structures of the human body.


The descriptions of neural pathways are intended as general guidelines only.

Individual variation should be regarded as a constant possibility.

In addition, the nerves found in the outer ear do not follow straight line courses like those frequently found in anatomic diagrams. They usually form spiraling patterns of individual neurons whose course is often subject to meandering.


• There are four cranial nerves involved in the process of sensory innervations of the outer ear. They are: Cranial nerves V, VII, IX, and X.

• The Cranial nerves originate in the Pons and Medulla in the brainstem (see FIGURE 5).



Please note:Both Cranial and Cervical nerves can generally be regarded as major communication points between the brain and body for intake of sensory (afferent) information and execution of motor (efferent) activities.


The Vth (trigeminal) Cranial Nerve

• The Vth (trigeminal) cranial nerve is divided into three major branches: the ophthalmic, maxillary, and mandibular.

• One division of the mandibular branch is the auricular-temporal nerve, which provides sensory innervations to the top and front walls of the external auditory meatus, to the tragus, and to the crest of the helix.



The ophthalmic branch proceeds across the top of the temporal muscle and around the front of the face just above the brow.

Patients who report headache and/or muscle tension in this area following insertion of their hearing instrument may be triggering a neural arc and stimulating contraction of the muscles above the brow and along the upper side of the face.

Those contractions would then be registered by the Trigeminal (Vth cranial) as feelings of tension, etc.


The mandibular division of Vth cranial nerve provides the sensory input from the lower teeth and jaw, motor control of the tensor tympani and the muscles of mastication.

The external ear canal initiated neural activity leading to stimulation of the muscles and nerves of the mandible, may be reported as pain deep in the ear, lower jaw pain, pain in the lower teeth, tension in the cheeks or mouth, difficulty in chewing, or pain at the temporal-mandibular joint.


Please note:

Since the tensor tympani is directly involved in the acoustic reflex, it is possible that insertion of an acoustic coupling could result in the acoustic reflex “firing” thus, causing damping of the sound transmission through the ossicles and resulting in a reported feeling of occlusion.


The VIIth Cranial (facial) Nerve• The VIIth cranial (facial) nerve, is predominantly

a motor neuron.

• It does have sensory loci on the back of the auricle and in the concha.

• In some reports, the nerve has been found to branch from its sensory array at the tympanic membrane to and through the external ear canal to join the peripheral nerves in the auricle.


The VIIth Cranial (facial) NerveThe chorda tympani branch of Cranial VII controls contraction of the stapedius muscle as well as providing the sensation of taste in the anterior 2/3rds of the tongue.


The VIIth Cranial (facial) NerveThe facial nerve is unique among the twelve cranial nerves, in that it normally is inherently capable of cross-communication with:

• cranial nerves V, VIII, and IX, X, and

• the upper cervical nerves #2 & #3.



Please Note:

The neural cross-communication process is not fully understood, but lends general support to the idea that individual neural stimuli could influence other neural pathway responses.


• Innervations of Cranial VII (facial) nerve could cause muscle tension in the face which would be sensed by neurons of the cranial Vth (trigeminal).

• The Vth (trigeminal), with its' numerous branches, may create changes in the sense of taste, a runny nose, tearing or dryness in the eyes, either dryness or excess saliva in the mouth, and/or tension in the eyelids.


The VIIth Cranial (facial) Nerve

Please note:

Contraction of the stapedius could cause feelings of occlusion as well as increased sensitivity to low frequency sounds—they will have difficulty modulating their own voice.


The IXth (glossopharyngeal) Nerve

• The Glossopharyngeal cranial nerve IX, innervates sensation to the mucous membrane of the tympanic cavity, as well as controlling motor activity in opening and closing the Eustachian tube.

• Branches of cranial IX have been found to extend into the ear canal.


The IXth (glossopharyngeal) Nerve

• The primary sensory divisions of this nerve are involved in the back of the tongue and mouth, and the top of the throat.

• They could produce complaints of numbness, soreness, and tension in these areas.


The Xth (Vagus) Nerve• Most hearing instrument specialists are familiar

with the occasional cough response when inserting an impression block.

• The cough reflex is generated through Arnold's branch of the Vagus nerve, Cranial X.

• The Vagus provides sensory innervations to the bottom and back walls of the external meatus.


The Xth (Vagus) Nerve

Since one branch of Cranial X also provides monitoring of blood pressure, reports of hearing aid wearers with rapid heart rate and increased blood pressure may have much more than an emotional basis!


The Xth (Vagus) Nerve

It travels through the body, innervating the recurrent laryngeal nerves on each side of the larynx, parts of the lungs, the pericardial sac around the heart, and parts of the stomach and intestines.



The Xth (Vagus) Nerve• Identification of this innervation following

insertion of the hearing instrument. May involve: hoarseness in the voice, coughing, chest pain, changes in breathing patterns, changes in heart rate, and nausea.

• Note: reports of heart problems and vomiting are found in the literature, but should be considered an extremely rare instance.


Cervical Nerves #2 & #3• Cervical nerves 2 and 3 join to form the great

auricular nerve, receiving sensory information from the helix, anti-helix, lobule, and the mastoid process.

• This is likely the location of stimulation for the reported problems of tension in the neck and the feeling of tightness in the neck experienced in some hearing instrument users after insertion of their aids.



Cervical Nerves #2 & #3The reported problems of tension and the feeling of tightness in the neck after hearing instrument insertion, is a direct connection between the Xth (Vagus) nerve and Cervical 2 and 3; thus, increasing the potential for these complaints even when the instruments involved do not place direct pressure on the helix, anti-helix, or the mastoid.


Temporal Mandibular Joint (TMJ)

• Of special concern in cases involving non-acoustic occlusion effects is the role of the temporal-mandibular joint.

• Since the TMJ induces movement in the ear canal, the presence of an acoustic coupler could cause more pressure on the nerves in the area of the TMJ than would normally be found.


When neuropathy due to trauma, disease processes, chemical changes, heredity, or aging causes alterations in the normal transfer of neuro-electrical signals, the result could be multiple stimuli from a single sensory event. This neuro-electrical "short circuit" is presumed to be the basic process involved in non-acoustic occlusion.


The presence of and pressure from an occluding object in the ear canal could cause a cross-firing of the nerve, stimulating another nerve. It is likely that the most common cross-firing patterns occur within single major neural pathways.


It becomes increasingly evident that suggestions concerning the value and applicability of the principles of reflexology and acupressure, stemming from the concept of neural interaction as the norm rather than an exception may reflect a true understanding of the afferent/efferent connections and the behavioral effects of these nerve branches.


It is clear that the tactile reality of wearing an instrument must be considered in the fitting of hearing aids along with the acoustic needs of the patient.

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Occlusion effects -the neural challenges