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CANS Testing
What are the 4 categories of CANS dysfunction tests? - correct answer 1. Dichotic speech tests
- Binaural interaction tests
- Temporal ordering tests
- Monaural low redundancy speech tests On what physiologic premise are dichotic speech tests based? - correct answer On the physiologic premise that contralateral pathways are more numerous and robust than ipsilateral pathways Which means that if we use monaural stimulation, the information can be processed equally well by both ipsilateral and contralateral pathways. But in dichotic stimulation situations, the weaker ipsilateral pathways are believed to be suppressed by the stronger contralateral pathways. In dichotic testing, where do we expect the deficit to be if one hemisphere is compromised? - correct answer at the contra ear Where do we expect the deficit to be if the compromised hemisphere is the person's language-dominant hemisphere? - correct answer We may see bilateral deficits or a deficit at the contra ear. What type of lesion are dichotic tests sensitive to? - correct answer All dichotic tests are sensitive to cortical lesions, but, generally, they don't tend to be sensitive to brainstem lesions. What are the 5 types of dichotic speech tests? - correct answer 1. Dichotic digits
- Dichotic CVs
- Dichotic rhymes
- Staggered spondaic words
- Competing sentences Explain how the dichotic digits test works. - correct answer Present 4 digits simultaneously (2 to each ear) at 50 dB SL relative to spondee threshold. Patient repeats back all the digits they hear. Derive a % correct for each ear and compare to norms. What are the norms for dichotic digits? - correct answer 11 years old or older: abnormal = <90% at either ear What result would you expect on dichotic digits for a person with a right temporal lobe lesion? - correct answer <90% correct for the left ear Why would you expect a bilateral deficit in a dichotic speech test for patients with left temporal lobe lesions? - correct answer Most people's left hemisphere is the language-dominant hemisphere, and they have to use language to report their answers. When would a left hemisphere lesion maybe no show a bilateral deficit in dichotic speech tests? - correct answer If the lesion is deep within the left hemisphere,a s they tend to affect the corpus callosum. Explain how the dichotic CVs test works. - correct answer Present CVs dichotically at 50 dB SL relative to spondee thresholds; can be presented simultaneously or in lead-lag fashion. Patient repeats what they heard. Derive a % correct for each ear and compare to norms. What are the norms for dichotic CVs? - correct answer Abnormal adult performance = <43% for either ear in simultaneous condition OR <90% for either ear in lead-lag condition
What type effect would an interhemispheric pathway lesion have on a person? - correct answer They would have trouble transferring information from one side of the brain to the other. Explain how staggered spondaic words works. - correct answer Present 40 pairs of spondee words in an overlapping, staggered fashion, so that the first half of the first word and last half of the second word are in a non-competing condition. Derive a % correct for each ear and compare to norms. What are the norms for SSW? - correct answer Abnormal adult performance = <90% correct in either ear What does SSW tend to tease out? - correct answer Contralateral ear deficits where the hemisphere that is impacted is lesioned in the temporal lobe, specifically involving the primary auditory areas. Explain how competing sentences test works? - correct answer Present 25 pairs of simple sentences (5-7 words long) dichotically, with the target sentence softer ( dB SL relative to spondee threshold) than the competing sentence (50 dB SL relative to spondee threshold). 5 sentences are for practice, 10 where target sentence is in the right ear, and 10 where target sentence is in the left ear. Patient repeats the target sentence. Derive a % correct for each ear and compare to norms. Does competing sentences require accurate identification of every word in the sentence? - correct answer No, it just wants to know that they are hearing, processing, and understanding the meaning of the target sentence. What are the norms for competing sentences? - correct answer Abnormal adult performance = <90% correct for either ear What is competing sentences sensitive to? - correct answer It is more sensitive to kids with auditory processing issues than it is to CANS lesions in adults.
What is a limitation of competing sentences? - correct answer There is some subjectivity in scoring. What is a type of binaural interaction test? - correct answer 1. Masking level difference test Explain how the masking level difference test works. - correct answer A tone (typically a 500 Hz pulsed tone) is presented binaurally in the presence of broadband noise (noise at 60 dB HL). Tone is pulsed on and off at a rate of 200 ms (200 on, 200 off). Intensity of tone is increased until the patient says that they can hear the tone in the midst of the noise. Then, obtain the detection threshold of the tone using 2 dB step changes. Find this threshold for SoNo and SpiNo conditions. Calculate MLD and compare to norms. Why do you typically use a 500 Hz pulsed tone in MLD? - correct answer There is usually less hearing loss in the low frequencies. It is less likely to have an asymmetry in the lower frequencies. Can you change the frequency of the tone in MLD? - correct answer Yes, it doesn't have to be 500 hz. You can use a different frequency is the hearing loss configuration calls for it. What are the SoNo and SpiNo conditions in MLD? - correct answer SoNo = both signal and noise are presented to each ear in phase with the other ear SpiNo = signal is presented 180˚ out of phase with the signal in the other ear (still introduced at same time, just not in the same phase); noise is presented in the same phase to both ears. In which MLD condition is it easiest to hear the tone? - correct answer In the SpiNo condition
What are 2 types of temporal ordering tests? - correct answer 1. Frequency pattern sequences test
- Duration pattern tests What are temporal ordering tests sensitive to? - correct answer Temporal ordering tests tend to be sensitive to cortical and interhemispheric lesions. What do temporal ordering tests give us an opportunity to examine? - correct answer integration across processing regions On what idea are temporal ordering tested based? - correct answer They are based on the idea that linguistic information, for most people, is processed in the left hemisphere and suprasegmental information (pattern recognition, etc.) is processed in the right hemisphere, BUT there has to be some integration of these regions, and that is what these tasks are measuring. What are the advantages of temporal ordering tests? - correct answer 1. Easy to administer
- Can be really useful for assessing non-native English speakers Explain how frequency pattern sequences works. - correct answer Present 30 test sequences monaurally at 50 dB SL, with each sequence containing 3 tonebursts made up of patterns using a high and a low toneburst. Patient either verbally labels what they heard or hums it back. Derive a % correct for each ear and compare to norms. What are the norms for frequency pattern sequences? - correct answer Abnormal adult performance = <75% correct in either ear What are the typically high and low frequencies for frequency pattern sequences? - correct answer High = 1122 Hz Low = 880 Hz
What are all of the possible sequences possible for frequency pattern sequences? - correct answer HHL HLH HLL LHL LLH LHH Do we usually have the patient label or hum in frequency patterns sequences? - correct answer Typically, we have them do both conditions because tehh combined information can give us more clues to the site of lesion. Which condition will patients have trouble in for frequency pattern sequences if they have a lesion in the right, the left, or in interhemispheric pathways? - correct answer Patient who have a lesion in either hemisphere or in the interhemispheric pathways will have difficulty verbally labeling what they are perceiving in the monaural stimulus presentation. Why would a patient have difficulty verbally labeling patterns if their lesion was in the left hemisphere? - correct answer Even though the pattern is processed in the healthy right hemisphere and it crosses over via the healthy interhemispheric pathways, they will have difficulty expressing it verbally because the left hemisphere is usually the language-dominant hemisphere. Why would a patient have difficulty verbally labeling patterns if their lesion was in the right hemisphere? - correct answer They will have difficulty processing the pattern, so they won't be able to verbally express it correctly because it was never processed correctly. Why would a patient have difficulty verbally labeling patterns if their lesion was in the interhemispheric pathways? - correct answer Even though the right hemisphere is healthy and could process the stimuli correctly and the left hemisphere is healthy and the person could verbally express it, the processed information cannot be properly transferred to the other hemisphere.
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Is labeling or humming done most often in duration pattern test? - correct answer labeling What are the norms for duration pattern test? - correct answer Abnormal adult performance = <70% correct for humming <70% correct for labeling What type of deficit patterns for lesions do you expect to see with duration pattern test? - correct answer You will see the same patterns concerning site of lesion as you did with frequency pattern testing. What are 2 types of monaural low redundancy speech tests? - correct answer 1. Low-pass filtered speech
- Compressed speech What are monaural low redundancy speech tests sensitive to? - correct answer They are moderately sensitive to central nervous system lesions and are more useful for things like APD monitoring. Explain how LPFS works. - correct answer Present 50 monosyllabic words monaurally at 50 dB SL, with the words low-pass filtered at 500 Hz with a filter skirt of 18 dB per octave. Patient repeats the word that they hear and are encouraged to guess if unsure. Derive a % correct for each ear and compare to norms. What are the norms for LPFS? - correct answer Abnormal adult performance = <70% correct for either ear What happens when we low-pass filter speech? - correct answer We remove a lot of the redundancy available in the speech signal.
Patient with temporal lobe lesions tend to show abnormal results where in LPFS? - correct answer in the contra ear What is LPFS not as sensitive to? - correct answer LPFS is not as sensitive to interhemispheric pathway lesions and tends to be normal in these patients. Could you have normal peripheral testing with a temporal lobe lesion and deficits in LPFS? - correct answer Yes, peripheral hearing may look fine, but you could still see deficits in LPFS in these patients. What type of APD usually pairs with difficulty on LPFS? - correct answer integrative Explain how compressed speech works. - correct answer Present 6 NU word lists monaurally at 40 dB SL that have been time compressed with a 60% compression ratio. Patient repeats what they hear and are encouraged to guess if unsure. Derive a % correct for each ear and compare to norms. What compression ratio is used for compressed speech tests? - correct answer 60% What are the norms for compressed speech? - correct answer Abnormal adult performance = <82% in either ear In which ear do you usually see deficits in compressed speech? - correct answer contra ear What is compressed speech sensitive to? - correct answer Intra-cranial lesions that involve the temporal lobe and tends to be more sensitive to lesions that are diffuse rather than specific What is ABR dependent on? - correct answer synchrony
T/F: The cortex and auditory system don't carry a lot of redundant information. - correct answer False - They do carry a lot of redundant information. Because the cortex and auditory system carry a lot of redundant information, what happens when the brain is damaged? - correct answer Certain areas can be damaged and we may not see much effect on function. There may be a focal lesion in an area that seems important to function, but the person can still function fine because the other redundant areas of the brain are working and will make up for this lesion. What is the most common finding in CANS testing with subcortical and cortical lesions? - correct answer a contralateral lesion Why is a contralateral lesion the most common finding in CANS testing with subcortical and cortical lesions? - correct answer There are more contralateral fibers than there are ipsilateral fibers. Therefore, if the contra pathway is compromised, the weaker ipsilateral tract has to assume a larger workload to compensate, but it may not be able to do that because it is weaker. So, you may see deficits because you are pushing the system, which will cause it to break down. More complex signals, like in the CANS tests, require more neurons to process them, and the ipsi pathways may not have enough neurons to do this and keep up. Why might you see normal peripheral test results but deficits in CANS tests? - correct answer The tasks and signals for the peripheral tests are not as complex as for the CANS tests. You can see a breakdown in processing ability when signals are distorted. How may signals become distorted? - correct answer 1. You distort the signal purposefully, like with LPFS.
- Perception could be distorted by presenting stimuli to the contralateral ear because the contralateral pathway is damaged and can't preserve the signal, so it is distorted.
- A lesion could be big enough to distort or block info coming through both the ipsi and contra pathways, which would results in major deficits and would cause whatever information that does make it through to be distorted.
In what type of CANS tests may you see more of a laterality effect? - correct answer You may see more of a laterality effect (meaning more of a contralateral deficit) with dichotic speech tests than with monaural low redundancy speech tests, especially if the lesion is limited to a single cortex. Which hemisphere recognizes/processing patterns and which is typically the language-dominated hemisphere? - correct answer The right will recognize the pattern. The left is typically the language-dominated hemisphere. How can having a patient label AND hum during a frequency or duration pattern test help identify the site of lesion? - correct answer It is difficult to determine whether it is a right, left, or interhemispheric issue just by labeling. However, if they can hum accurately but label inaccurately, it is a left hemisphere issue. If they inaccurately hum AND label, it could be a right hemisphere or interhemispheric issue (difficult to tell). What would you expect the results on frequency pattern labeling and MLR to be for a patient with a left hemisphere stroke? - correct answer MLR: electrode effect with MLR responses being abnormal over the left hemisphere despite ear of stimulation, OR ear effect with MLR responses abnormal when the right ear is stimulated Frequency pattern test: bilateral deficits
