Central Deafness and Other Auditory Processing Disorders

Question 1

What are some other conditions that may be considered true auditory processing disorders due to the current definition?

Answer 1

Tinnitus (modality specific and non-speech stimuli are used for assessment; may interfere with hearing causing issues with work and social life)
ANSD (characterized by normal function of sensory cochlear cells but abnormal structure/function of auditory neurons/synapses; modality specific)
Cerebrovascular accidents (lesions that can be diagnosed with scans; word-finding difficulties (anomia))
Concussion
Central deafness

Question 2

What characterizes ANSD?

Answer 2

Normal OAEs
Recordable cochlear microphonic

Question 3

Will people with ANSD have abnormal responses for all tests involving CN VIII?

Answer 3

Yes
ARTs, ABR, ECochG, and MLDs

Question 4

Are pure tone thresholds a measure of neural synchrony?

Answer 4

No
That means that ANSD thresholds can range from normal to profound SNHL

Question 5

What are the similarities between ANSD and CAPD?

Answer 5

Both peripheral disorders with central implications
No single cause
Evidence of familial history in some cases

Question 6

Are some risk factors associated with both CAPD and ANSD?

Answer 6

Yes
Both hyperbilirubinemia and a positive family history
*CANS is highly sensitive to bilirubin toxicity

Question 7

Did many professional guidelines recommend that auditory evoked responses (AERs) be included as a diagnostic measure for CAPD?

Answer 7

Yes
But there are no definitive diagnostic characteristics of AERs that are associated with (C)APD

Question 8

What are AERs like with ANSD?

Answer 8

Generally abnormal
Absent/abnormal ECochG and ABR
Possible abnormal auditory mid latency and late latency responses; P1 maybe a possible biologic marker for ANSD
Possible abnormal P300
In many cases of ANSD, middle & late AERs may be normal with an abnormal ABR

Question 9

What is cochlear synaptopathy?

Answer 9

Hidden hearing loss
Acquired (CAPD is congenital) condition that permanently interrupts synaptic communication between sensory IHCs and afferent VIII N fibers before overt hearing loss is diagnosed
Typically seen with NIHL and aging
Typically considered an auditory processing disorder

Question 10

What are the clinical manifestations for cochlear synaptopathy?

Answer 10

Decreased wave I amplitude with normal ABR thresholds
Various supra-threshold perceptual abnormalities not captured by the audiogram such as speech-in-noise difficulties, tinnitus, and hyperacusis

Question 11

What is the most common cause of cerebral damage?

Answer 11

Cerebrovascular accidents (CVA) aka strokes

Question 12

What are risk factors for CVAs?

Answer 12

High blood pressure
Heart disease
Diabetes
Cigarette smoking
Increasing age
Prior stroke

Question 13

What are the major signs and symptoms of a stroke?

Answer 13

Sudden numbness or weakness of the face, arm, or leg
Sudden confusion or trouble speaking or understanding others
Sudden trouble seeing in one or both eyes
Sudden dizziness
Trouble walking or loss of balance/coordination
Sudden severe headache with no known cause

Question 14

What are the two mechanisms of strokes?

Answer 14

Ischemia (can be caused by thrombus aka blood clot or embolus aka part of a clot)
Hemorrhage (blood vessel ruptures)

Question 15

What is a CVA caused by thrombus?

Answer 15

Single most common cause of CVAs
May occur in any large cerebral blood vessel
It obstructs blood flow through the affected vessel
Area of the brain supplied by the blood vessel becomes ischemic
Brain cells ultimately die
Functions performed by that area are diminished or lost

Question 16

What is a CVA caused by embolus?

Answer 16

A small blood clot that has dislodged from a larger blood clot elsewhere in the body
Usually from the heart following a recent heart attack
From one of the carotid arteries
From the leg veins following a long journey with long hours of immobility such as transatlantic flights
If it is a small clot it may pass on and the patient may recover completely from the ischemic attack (transient ischemic attacks (TIAs))
Eventually, they may lead to a full blown CVA

Question 17

What is a CVA caused by a hemorrhage?

Answer 17

When a blood vessel in the brain ruptures and bleeds
Most common cause is uncontrolled significantly high blood pressure
Can also be caused by aneurysms and arteriovenous malformations (AVMs)
Less common occurrence than an ischemic stroke, but can cause damage for two reasons
First, the blood itself is an irritant and damages the surrounding neural tissue
Second, the affected blood vessel usually goes into spasm effectively cutting off blood supply to distal areas

Question 18

Is the end result of a CVA similar for both ischemic and hemorrhage?

Answer 18

Yes

Question 19

What does the CVA damage depend on?

Answer 19

The size of the blood vessel(s) affected
The volume of brain tissue damage
Anastomosis of blood vessels in that area
In severe cases, the degree and extent of brain damage can be fatal
In other cases, a small blood vessel may be affected supplying a small area of the brain and the patient may have no symptoms

Question 20

Can a CAV cause auditory symptoms?

Answer 20

Sometimes
If the portion of the brain carrying the auditory pathways or the auditory cortical area is affected, there may be auditory symptoms
As with cortical tumors, peripheral tests may be normal
There may be significant decrease in speech understanding abilities that may not improve with appropriate amplification
If the patient is already a hearing aid user, the hearing aid of the ear opposite to the side of the stroke may appear less effective

Question 21

Can concussions cause lasting effects?

Answer 21

Yes
Especially for NFL players
Named the disorder chronic traumatic encephalopathy (CTE)

Question 22

What is a concussion?

Answer 22

A diffuse, nonpenetrating TBI caused by a sudden external force
It is caused by a bump, blow, or jolt to the head, or by a hit to the body that causes the head and brain to move rapidly back and forth
This sudden movement can cause the brain to bounce around or twist in the skull, creating chemical changes in the brain and sometimes stretching/damaging brain cells

Question 23

Why are concussions deemed as a mild traumatic brain injury?

Answer 23

Because they are usually not life threatening
Even so, the effects of a concussion can be quite serious

Question 24

What are the 4 categories of concussion symptoms?

Answer 24

Cognitive impairments (difficulty concentrating and short term memory problems)
Physiological impairments (blurred visions and hearing problems)
Emotional problems (feelings of sadness or depression)
Sleep disturbances

Question 25

Can type and severity of symptoms vary for concussions?

Answer 25

Type and severity of these symptoms can vary substantially
Further, the same force that causes a concussion in one individual may not cause a concussion in another

Question 26

What are the dangerous signs and symptoms of a concussion?

Answer 26

One pupil larger than the other
Drowsiness or inability to wake up
A headache that gets worse and does not go away
Slurred speech, weakness, numbness, or decreased coordination
Repeated vomiting or nausea, and/or seizures
Unusual behavior, increased confusion, restlessness, or agitation
Loss of consciousness (passed out/knocked out)
Even a brief loss of consciousness should be taken seriously

Question 27

Are concussions a public health risk?

Answer 27

Yes
Since 2000, nearly 300,000 U. S. service members have been diagnosed with a concussion, which maybe an undercount
In the U. S., 1.6 million to 3.8 million sports-related concussions occur annually

Question 28

What are subconcussive injuries?

Answer 28

Which are not severe enough to cause acute concussion symptoms
But the accrual of concussive and subconcussive events over time are believed to lead to progressive brain atrophy, a disease known as Chronic Traumatic Encephalopathy, or CTE
Common in contact sports such as football or boxing

Question 29

What is CTE?

Answer 29

A rare neurodegenerative injury the symptoms of which do not manifest until years after
CTE leads to mood disorders including emotional instability, short-term memory loss, depression, cognitive decline, and dementia

Question 30

Is concussion an invisible injury?

Answer 30

Yes
Affects function, not macrostructure
It is, therefore, undetectable using conventional imaging methods such as MRI or CAT scans
But those tests are performed to rule out bleeds/hematomas, skull fractures, and other issues
Diagnosis relies heavily on a patient’s symptoms
Repeat concussions are much more dangerous than single concussions

Question 31

Why could concussions impair the auditory brain?

Answer 31

The auditory system has more relays connecting the sensory organ to the brain than any other sensory systems
It contains some of the longest axonal tracts (e.g., the lateral lemniscus)
Axons bi-directionally link each of the auditory relays, traversing between the ear, brainstem, midbrain, and cortex
In addition to blood vessels, axons are believed to bear the brunt of damage from a concussive force (stretched and sheared by the movement)
Can initiate a dysfunctional metabolic cascade, which can lead to improper signaling among cells, or potential death of axons

Question 32

Could temporal aspects of sound be affected by concussions?

Answer 32

Yes
The axon damage, inflammation, and bruising can disrupt temporal precision
Leads to poor encoding of sound
The auditory system responds to input more than 1000 times faster than photoreceptors in the visual system
Bottom line: Concussion can impair listening abilities and processing auditory information

Question 33

What does the data report with veterans with concussion?

Answer 33

Nearly half of the blast-exposed veterans treated for concussion at VA hospitals and clinics complained of hearing difficulty, yet only 35% of these patients showed elevated audiometric thresholds
For the remaining 65%, the auditory symptoms were not in the periphery but were more central, i.e., difficulty understanding
Veterans with blast exposure who displayed normal audiometric thresholds performed more poorly than veterans without blast exposure on listening skills
Symptoms persisted at least 4+ years

Question 34

Is it difficult to determine if a blast caused PTSD or concussion?

Answer 34

Yes
Because PTSD also can lead to sleep disturbance or anxiety, it is difficult to determine if the blast exposure resulted in PTSD, concussion, or both
Blast exposures can often result in both concussion and PTSD, which then makes the symptoms of each worse

Question 35

What are other auditory complaints that individuals with concussions can have?

Answer 35

Tinnitus
An inability to ignore distracting sounds
Inability to remember and follow oral directions
Difficulty understanding speech in noisy environments

Question 36

Do university athletes that have a history of concussion perform more poorly on tests than those without concussion?

Answer 36

Yes
Especially on tests that require integrating auditory information binaurally

Question 37

Do children during the acute stage of recovery from concussion have a difficult time understanding speech in noise?

Answer 37

Yes
Performance during later parts of the test for the concussed children declined in contrast to a steady performance by their peers, suggesting that
Both fatigue and auditory processing problems affect speech-in-noise abilities in concussed children

Question 38

What is central deafness?

Answer 38

A rare disorder of the CANs most commonly secondary to CVA or head trauma (acquired)
Rare because most patients with this severe of an injury do not survive
Occurs in both heschls gyri and possibly the subcortical areas
Patients present with generally preserved peripheral auditory function but an inability to meaningfully perceive speech and/or environmental sounds
Symptoms severity varies
The ability to speak, read, and write is typically preserved
Cognitive ability is generally intact unless it is affected secondary to the underlying pathology

Question 39

What are other terms for central deafness?

Answer 39

Cortical deafness
Pure word deafness
Auditory agnosia (subset of individuals with aphasia who can hear and see but cannot identify or recognize sounds)

Question 40

What is the etiology for central deafness?

Answer 40

Cerebrovascular accidents (strokes - most common)
Degenerative brain diseases, like Creutzfeldt-Jakob (mad cow) disease
Encephalitis

Question 41

What is the site of lesion for central deafness?

Answer 41

Bilateral involvement of the primary auditory cortex (heschl’s gyrus) (most common)
Secondary and associated auditory areas
Subcortical areas; internal capsule (highway of the nerves, pass through before projecting out to the cortex; a lesion of the right size and location can cause a disconnect b/w the periphery and CANS resulting in central deafness)
Parietal lobe
Frontal lobe
Medial geniculate body & Pons

Question 42

What do you need to do to diagnose someone with central deafness?

Answer 42

Complete peripheral audiologic assessment (pure tones, speech, immittance, OAEs)
Behavioral CAPD tests (non-linguistic tests may be performed to rule out (C)APD, if the patient can perform the test reliably)
Early to late auditory evoked responses (ABR will generally be normal, these will be abnormal depending on the size and site of lesion)
MRI with contrast (to assess for space-occupying lesions and CVAs)
CT scan (to assess for CNS abnormalities)
*Patient may not be able to perform SRT or WRS in quiet or noise, which may appear inconsistent with hearing levels

Question 43

How is central deafness managed?

Answer 43

Depends on the etiology
Central deafness due to vascular accidents may resolve showing partial or near complete recovery
Speech and language therapy and auditory training may be helpful
Hearing aids are generally not helpful
Use of visual cues/devices to communicate may be necessary
Many patients will recover at least some auditory function over time

Question 44

What are the differential diagnoses for central deafness?

Answer 44

Non-organic hearing loss (needs to be ruled out) -
Inconsistency between pure tone thresholds and speech audiometry is common with central deafness
But these individuals are not malingering, rather they have difficulty responding reliably to pure tones, which raises the suspicion of NOHL
In addition, they may appear to understand some environmental sounds and not others, which again appears suspicious for NOHL
(C)APD
Dementia
Tumors