A 77-year-old woman is brought to the physician by her son for a routine health maintenance examination. She says that she feels well. Her son reports that 1 month ago, she got lost while driving home from the local supermarket. Two weeks ago, she forgot to turn off the stove after cooking dinner. She has been wearing bilateral hearing aids since audiometry 2 years ago showed bilateral high-frequency hearing loss. Her visual acuity corrected with glasses is 20/25 in both eyes. Neurologic examination shows mild fine tremors of the hands when the arms are outstretched; the tremor is not present at rest. Muscle strength is 5/5 in all extremities. Deep tendon reflexes are decreased at the ankles and 2+ elsewhere. Her gait is normal. Sensation to vibration is mildly decreased over the toes. On mental status examination, she is awake, alert, and conversant. Her language function is normal. She is oriented to person, place, and time and recalls one out of three objects after 10 minutes. Which of the following findings in this patient warrants further evaluation?
A ) Decreased deep tendon reflexes at the ankles
B ) Decreased sensation to vibration over the toes
C ) High-frequency hearing loss
D ) Memory loss
E ) Tremor of the outstretched hands