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Hi! I have a few questions regarding the 1st exam i took. I would like some clarification one several questions.
#8 regarding type of validity seen for the researcher who failed at developing a new quality of life survey. Can I get further explanation of the differences of face validity and construct validity? I am having difficulty understanding the difference of “testing an abstract” vs “testing what it appears to test”. I see that your definition of construct includes quality of life, but I want to understand the relationship and differences of the two types as oppose to memorizing what belongs where.
#19 regarding type of intervention for a person with motion sensitivity. the correct answer is Habituation. I was confusing habituation with VOR exercises which I though required the creation of a retinal slip, which I now learned (by looking back into the powerpoint) that I am confusing that with adaptation. So my question is, what would determine if one picks adaptation or habituation? Is the key clue in the question the statement ” increased symptoms with head impulse test but does not have a notable lag either direction”. Also, would VOR exercises fall under the category of adaptation? And how do habituation exercises even look like?
#37. It ask about what oculomotor impairments are not associated with cerebellar dysfunction. the correct answer is impaired VOR. But doesnt the vestibulocerebellum have some control or involvement in VOR?
#72. Question askes about what symptoms are effected by dopamine medications and the answer is dysarthria. I do not disagree, but why can the answer equally be postural instability? Why is disarthria the better answer if postural instability is listed as a “cardinal sign”?
– Alex
I apologize for taking so much of your time with all these questions. -
Hi Alex,
No need to apologize; these questions are why I’m here!
I’ll do my best to clear some of this up:
#8 – This researcher found that her new quality of life survey was not *actually* measuring quality of life. Quality of life is the abstract concept she was trying (and failing) to measure, so the survey lacks construct validity. Face validity is a fairly superficial and the least scientific measure of validity; it means that a test *looks like* it is measuring what it is supposed to measure. To determine face validity, we would ask an untrained person to read the survey and see what they think it is measuring. We don’t have any details about the new survey in question, so we cannot speak to what someone would think it is measuring and its face validity. Face validity is subjective – and there are times when we would actually desire low face validity (for example, a test for mental illness when an individual may be motivated to answer questions to avoid an undesirable diagnosis).
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#19 – Adaptation exercises are aimed at inducing neurorecovery by improving an abnormal vestibulo-ocular reflex. Adaptation exercises include gaze stabilization (VORx1 and VORx2) that induces an error signal (retinal slip). Those occasional errors drive neuroplasticity to improve our VOR gain (note: As with inducing neuroplasticity in other populations, a task that is too easy or too difficult with not drive change. Occasional errors are critical for learning, but constant errors shut down learning.). An individual with an abnormal vestibulo-ocular reflex would demonstrate an abnormal head impulse test and would report symptoms primarily with tasks that involve head turns.This patient is reporting dizziness with all movement, not isolated to head turns. She does not have a positive head impulse test and she only feels relief when she is still. This indicates general motion sensitivity rather than a diagnosis that would warrant vestibular adaptation exercises (like unilateral vestibular hypofunction).
Motion sensitivity is treated with habituation exercises. Habituation exercises are repeatedly exposing a person to the stimulus that creates symptoms with the goal of desensitization. I think about this as riding a spinning ride at an amusement park. The first time I ride the ride, I might feel very dizzy. If I ride it 10 times in a row, I won’t feel as dizzy from the 9th to 10th time as I do from 0-1 times.
In this case, we would select certain movements that cause dizziness. These can be selected through interviewing the patient and/or by administering a standardized measure like the Motion Sensitivity Quotient. We would select 3-5 specific movements and have the patient perform them repeatedly a couple times per day. Examples of movements often selected for treating motion sensitivity are rolling supine to sidelying, turning the head horizontally, and performing 180-degree turns.
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#37 – Great point! I’ve flagged this question to review in the off-season. The point of the question was to emphasize that the vestibulo-ocular reflex is primarily a peripheral function and impairments are consistent with peripheral vestibular dysfunction (like neuritis or labrynthitis) and the cerebellum is a central structure for which dysfunction would cause central vestibular dysfunction. VOR cancellation, smooth pursuits, and saccades are purely central functions. However, you are correct that there are some central influences to the VOR itself and cerebellar dysfunction could cause problems here. The *best* answer here is VOR because it is the only one that is not driven purely by central functions and I like some ambiguity because the NCS exam will ask you to pick the “best” option from multiple “good” ones, but I think the question could maybe use some tweaking.___
#72 – Postural instability is a cardinal sign of Parkinson’s disease, but it does not respond to dopamine replacement therapy. The other cardinal signs do respond to medications. Cognitive and autonomic symptoms are also unresponsive to medications. Therefore, dysarthria is the best choice.Chrissy
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for #19, does the sentence “She verbalizes increased symptoms with head impulse test but does not have a notable lag either direction.” eliminate adaptation as an appropriate intervention? Head impulse test checks the VOR, but if she had no “lag” then this is a negative test thus her VOR is intact. Is this a correct interpretation?
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The lack of a catch-up saccade during head impulse testing tells us that her vestibulo-ocular reflex is presumably intact and, therefore, she likely does not require adaptation exercises. In reality, there are some weeds that make this messier – but they are likely beyond the scope of the NCS. If the patient did not have so many signs of motion sensitivity and she reported symptoms only during head impulse testing but still did not have an overt retinal slip, I would consider implementing gaze stabilization exercises for the purposes of adaptation.
Additionally, if the patient doesn’t respond to physical therapy interventions, I might recommend more sophisticated testing. Some physical therapy clinics can do video head impulse tests (vHIT) that can detect covert catch-up saccades that would indicate an abnormal VOR that is not observable without equipment. Audiologists who complete full vestibular function test batteries can also do vHIT – and I might recommend complete vestibular function testing for this patient that would quantify how well the peripheral vestibular system is functioning and detect any asymmetries. Vestibular function testing is summarized in the vestibular lecture under “diagnostic and medical management”.
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