this scenario has many distracters but also some key findings; i will give my opinion but i really don't know if it's a good one.....
from my first read i think this is a scenario of dementia.....from this point, there a quite a few causes which could get dementia:
1. at her age Altzheimer disease might be the very first choice; the problem is with the history: she got lost and forget to turn off the stove only one time.....there is no history of gradually worsening of those symptoms; in my opinion this is not the diagnosis here.
2. normal pressure hydrochepalus......in the scanario it says she has a normal gait and they don't say anything about urinary incontinence; so i think this is not the diagnosis also.
3. Parkinson disease.....her gait is normal but she has that mild tremor which is bilateral; as long as i remenmber, Parkinson disease starts unilateral and ussually occures at rest and improves with activity; here the patient has it when she outstratches the hands and is not present at rest....so i think this is not the right diagnosis also
4. hyperthyroidism.....besides that fine tremor, there is nothing else which could say that this is the right diagnosis.
5. from my point of view, the most important clues to the right diagnosis are the lost of vibration on her toes, decreased DTR's at the ankles and recalling only 1 word out of 3; in my opinion she has vitamin B12 deficiency which would explain most of the symptoms(memory loss=she got lost and forgot to turn off the stove, sensation lost=subacute combined degeneration of the spinal cord-partial explanation because her motor activity is 5/5 all over); so, in my opinion i would check first her serum B12 level and i would focus on that decreased sensation to vibration over the toes(answer B)
her hearing loss and 20/25 vision acuity, even though are not normal, are frequently seen at her age group without any other associated pathology;
again, this is my opinion and i might be wrong; it would be nice if somebody could post the right answer and give some explanations.....i think this is a hard/tricky question