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There is an interesting interaction between newborn hearing screening programs (which typically use OAE), and AN.
Where we practice in Chicago, AN is not a common diagnosis, even though some authors report a prevalence as high as 27% of AN in hearing loss in 10-12 year olds. Another problem with AN case finding is the vulnerability of the definition to diagnostic error. A third problem with AN is that it is just implausible that there should be selective nerve damage to the hearing part of the 8th nerve, without damage to the vestibular part as well. To summarize this section, there are significant questions about the definition, existence and prevalence of AN.
Logically, the diagnostic process might not necessarily prove that the site of lesion is the auditory nerve. McMahon and others pointed out that a brainstem disorder could also cause similar testing pattern as that said to be diagnostic of an auditory neuropathy (2008).
In the authors opinion, in adult patients diagnosed with AN, a more generalized peripheral neuropathy should be considered including testing for the more common treatable types of neuropathy (i.e.
One would expect that other heavy metals might also cause neurotoxicity (such as arsenic or lead). One would expect that cochlear implants (CI)would be useless for AN caused by cochlear nerve damage (or absence), but potentially useful for AN caused by cochlear damage. Ji et al, reported that only a single one of their 8 implanted subjects attained speech capability (2015).
Budenz et al (2013) reported that "Children with a diagnosis of AN without associated cognitive or developmental disorders have speech and language outcomes comparable to other children who received a CI.
Can et al (2015) reported that 2% of late preterms with hyperbilirubinemia had AN (same as controls).
Gibson and Sanli (2007) studied 39 children with auditory neuropathy and concluded that the more likely mechanism was selective loss of inner hair cells. Zong et al (2015) reported a mutation in a family containing variation in a gene termed AIFM1. Lepcha et al (2015) reported that ANS occurred in 1.12% of patients in an Indian ENT clinic. Morelet et al (2014) reported a group of 9 Amish persons, who were interrelated, with a mutation in SLITRK6, who had a syndrome with some aspects of AN.
Auditory nerve tumor is benign slowly growing tumor which is usually unilateral but in some cases may be bilateral. Early detection of the tumor at the time of minimal hearing defect or facial motor difficulty is important. Tags: amicus,medical,brain,auditory,pathways,geniculate,body,quadrigeminal,lemniscus,medulla,oblongata,olivary,nucleus,chochlear,nuclei,vestibulocochlear,nerve,cochlear,ear,drum,malleus,incus,stapes,vestibular,labryrinth,temporal,lobe,receiving,centers,cerebral,cortex.
Topic category and keywords: amicus,medical,brain,auditory,pathways,geniculate,body,quadrigeminal,lemniscus,medulla,oblongata,olivary,nucleus,chochlear,nuclei,vestibulocochlear,nerve,cochlear,ear,drum,malleus,incus,stapes,vestibular,labryrinth,temporal,lobe,receiving,centers,cerebral,cortex. This webpage also contains drawings and diagrams of brain medical which can be useful to attorneys in court who have a case concerning this type of medical regarding the brain. This illustration also shows amicus, medical, brain, auditory, pathways, geniculate, body, quadrigeminal, lemniscus, medulla, oblongata, olivary, nucleus, chochlear, nuclei, vestibulocochlear, nerve, cochlear, ear, drum, malleus, incus, stapes, vestibular, labryrinth, temporal, lobe, receiving, centers, cerebral, cortex, to enhance the meaning.
Topographic maps of this sort are a big deal - we'll see many examples in the visual system of how information about various aspects of vision gets laid out amongst a collection of neurons in a systematic way. Two cues for localizing a sound source are: inter-aural intensity difference (IID) and inter-aural timing difference (ITD).
In above figures, the sound arriving at the ear that is furthest from the sound source is delayed (time difference) and lower in amplitude (intensity difference). LSO contains neurons that are selective to intensity differences and MSO contains neurons that are selective for timing differences.
This graph shows the responses (firing rates) of an example LSO neuron that response strongly when the sound arriving at the ipsilateral ear is louder than the sound in the contralateral ear (Recall that there are two superior olives, one on the right and the other on the left, and note that ipsilateral means same side and contralateral means opposite side).
This graph shows the responses (firing rates) of an example MSO neuron to different interaural timing differences.
Konishi took a close look at the anatomy of the MSO (also called the nucleus laminaris) and found that the neurons are connected in a way that looks remarkably like the wiring diagram predicted by Jeffries. A related acronym, ANSD -- auditory neuropathy spectrum disorder -- is a less well defined version of AN. On the other hand, it may be that the AN syndrome is just so imprecise that there is little clinical attention devoted to it and it deserves to remain obscure. One would expect that AN would be always missed in these programs, because AN is defined by present OAEs. Of course, the logical defense to this is that diagnostic methods for vestibular function are missing vestibular nerve damage.
Gibson and Sanli recently pointed out that a selective loss of inner hair cells might create a similar testing configuration (2007).
This seems possible to us, but unlikely in the absence of imaging or clinical findings supporting a brainstem disorder.

Somewhat contrary to this idea that nerve disease can be detected with a VEMP is the observation that VEMPs are generally normal in vestibular neuritis. This is not a common observation however, and of course, steroids are not a practical long term treatment. If a child grows up with no hearing, they may not develop the central circuitry to hear (or it may die off). On the other hand, Fernandez et al (2015), from Brazil, reported that An patients had similar response to CI as children with CI.
Our comment -- is the huge cost of CI justified by "at least partial measurable auditory benefit" ? Tang et al (2015) reported no coherent genetic anomaly in 71 patients including some with AN. They had progressive hearing gloss, were nearsighted, had no DPOAE's (of course AN should have present OAE's), and had poor ABR's. Frequency-Specific Electrocochleography Indicates that Presynaptic and Postsynaptic Mechanisms of Auditory Neuropathy Exist. With the progress of lesion, number of cranial nerves are involved (VII, V, IX and X) and there is contra lateral hemiplegia and hemianaesthesia due to compression of brain stem. Diagnosis is made by X-ray of the base of skull (Town’s view) which shows erosion of internal auditory meatus. This diagram should be filed in Google image search for medical, containing strong results for the topics of brain and auditory. Doctors may often use this drawing of the medical to help explain the concept they are speaking about when educating the jury. So if you are looking for images related to amicus, medical, brain, auditory, pathways, geniculate, body, quadrigeminal, lemniscus, medulla, oblongata, olivary, nucleus, chochlear, nuclei, vestibulocochlear, nerve, cochlear, ear, drum, malleus, incus, stapes, vestibular, labryrinth, temporal, lobe, receiving, centers, cerebral, cortex, then please take a look at the image above. These synapse on spiking neurons in the spiral ganglia, the axons of which form the auditory (8th cranial) nerve. Sounds arriving from the right side also arrive at the right ear first because it's closer. Indeed, this amount of time is actually smaller than the amount of time it takes to develop an action potential in the auditory nerve.
Konishi (at CalTech) and his colleagues have performed a large number of auditory experiments on barn owls. Then the firing rates of neurons in the right cochlear nucleus are higher than those in the left cochlear nucleus. It responds most strongly when the sound in the right ear leads that in the left ear by about 50 microseconds. And, the temporal tuning of these nerve cells has precisely the property that Jeffress predicted.
Geometrically, the set of locations in the world that are, say, 5 cm closer to one ear than the other is (approximately) a cone with its apex at the center of the head. However, we also have a certain degree of loudness constancy (sounds appear equally loud as the sound source changes in distance, despite the change in intensity at the ear). Some reports find cochlear aplasia -- a small cochlear nerve or bony aperture for the cochlear nerve (Jeong et al, 2013). Ascertainment of hearing thresholds is intrinsically subjective -- if you don't admit to hearing the tones -- you fail the test.
Of course, in neonates with brain damage associated with a premature or rough delivery, this might be more likely. As AN patients are almost all children, perhaps there should be an aggressive attempt to implant very young children. This is easy to understand -- if there is no nerve to transmit hearing signals to the brain, a CI is wasted money and effort. Tumor occurs in the extramedullary part of VIII nerve and is located in the cerebellopontine angle in the posterior cranial fossa.
As the lesion further progresses there is development of hemiplegia and sensory loss on the same side. Further confirmation is made by brain stem auditory evoked responses, CT and MRI with contrast injection. Given the nature of this drawing, it is to be a good visual depiction of brain medical, because this illustration focuses specifically on Auditory Pathways to the Brain.
These then lead to the cochlear nucleus, then to the superior olive, then to the inferior colliculus, then to the medial geniculate nucleus, and finally on to auditory cortex. You can, if you wish, attend to the violin part, and then listen specifically to the line played by the cellos.
This cue is especially easy to use with abrupt sounds, as you can compare the onset (beginning) of the sounds in each ear. Remarkably enough, this very precise temporal information is made available to your perceptual experience. While studying the inputs to the medial superior olive (MSO) and lateral superior olive (LSO), they discovered neural circuits and neurons that appear to be well-suited to representing these two types of information, both timing and intensity differences.

This hypothetical LSO neuron computes a difference between the firing rates (right cochlear nucleus firing rate minus left cochlear nucleus firing rate) and it responds strongly. There are other neurons in the MSO that respond best to different interaural timing differences.
The neurons communicating signals from the two ears converge in a very orderly fashion, with increasing delay in the transmission length. Sound sources located at any position in the cone (above-right, in front and to the right, behind and to the right, closer, further) generate exactly the same IID and ITD cues for the listener and thus can not be distinguished using IIDs or ITDs. Thus, there must be other cues to distance (as loudness constancy works, to some extent, even with your eyes closed). This group, lacking the wiring for hearing, would be expected to do very poorly concerning acquisition of hearing.
Otherwise, it would be very puzzling how a disorder of the 8th nerve could selectively damage the auditory portion or vestibular portion as the two parts of the nerve are extremely close and one would think that the same process that damages one would also damage the other.
With different investigators setting their criteria for AN differently -- perhaps this is why we have such wide variation.
So in other words, a combination of normal OAE, very abnormal ABR (only a wave 1 or a present cochlear potential on ECOG, and very impaired conventional hearing testing given that it can be performed at all, given that one can believe the results, would seem somewhat (not definitely) likely to identify an auditory nerve disorder. This is a thorny issue, made worse by the fuzziness if the definition of AN or ANSD as you prefer. If one has a vaguely defined ANSD, that could include inner hair cell damage, one could argue that there might be a reason to give it a try. This illustration, showing medical, fits the keyword search for brain medical, which would make it very useful for any educator trying to find images of brain medical. But in fact, the physical stimuli (the sound pressure waveforms) from these two groups of string instruments are very similar - entirely overlapping and intertwined with each other. That's what I need to know about to survive and function in the world, whether the event was you clapping your hands or a tiger in the jungle stepping on a twig. For continuous pure tones, this is more difficult as it involves a phase difference between the sound in the two ears. Another LSO neuron does the opposite comparison (left minus right) and it would respond strongly only if the sound in the left ear is stronger than than in the right ear.
Some prefer it when the sound in the right ear leads and others prefer it when the sound in the left ear leads. The inputs from the two ears are combined to generate neurons whose preference for inter-aural time differences varies systematically.
There are two ways to disambiguate the direction (azimuth and elevation) from which a sound is coming. All sounds arrive at your ear both directly, and as echoes and reverberations involving reflections off the ground and other environmental surfaces. So we don't hear (and most of the time we don't want to hear) a large portion of the physical stimulus (the sound waves) coming to our ears. Jeong et al (2013) reported patients with radiologic abnormalities of their cochlear nerve did much worse concerning CI response. Others prefer 50 microseconds, 55 microseconds, 70 microseconds, 100 microseconds, 200 microseconds, etc.
However, the timing of these reflections and the number and intensity of them is a cue to the kind of space you are in (hallway, concert hall, living space, outdoors) and to the distance to the sound source. It would be very easy to combine a normal OAE (which doesn't require any cooperation),with several tests that are greatly impaired by lack of cooperation (such as ABR), and diagnose AN. This use of words is similar to saying that ALS (motor neuron disease) was a subtype of peripheral neuropathy. The outer ears (the pinnae) are asymmetrically shaped, and filter sounds differently depending on where the sound sources are located and what frequency the sound has. If AN is truly a neuropathy, one would think that AN should increase with age as do neuropathies in general.
Of course, the logical defense to the assertion that AN is an artifact of uncooperative patients is that everybody else is doing bad testing.
When you know about oblongata and olivary and what they have in common with brain medical, you can begin to really understand nucleus. Since nucleus and chochlear are important components of Auditory Pathways to the Brain, adding chochlear to the illustrations is important.
Along with chochlear we can also focus on nuclei which also is important to Auditory Pathways to the Brain. Overall it is important to not leave out vestibulocochlear which plays a significant role in Auditory Pathways to the Brain.
In fact, vestibulocochlear is usually the most common aspect of an illustration showing Auditory Pathways to the Brain, along with medulla, oblongata, olivary, nucleus, chochlear and nuclei.

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