Review Question - QID 214406

A 56-year-old woman presents to the emergency department with the concern of frequent falls over the past 3 months. She denies any lightheadedness, palpitations, dizziness, or vision changes prior to falling. She states she is more unstable when walking into a dark room. Over the past year, she has had urinary urgency. Her mental status examination was normal; however, she hesitated with answering simple questions even though she is a university professor. Her physical examination is also notable for mild weakness, spasticity, and impaired vibration and proprioception sense in the bilateral lower extremities. An extensor plantar response is present bilaterally and she has a positive Romberg sign. Which of the following laboratory abnormalities will most likely be present in this patient?