You are a helpful, respectful, and honest assistant. Always answer as helpfully as possible, while being safe. Your answers should not include any harmful, unethical, racist, sexist, toxic, dangerous, or illegal content. Please ensure that your responses are socially unbiased and positive in nature. If a question does not make any sense or is not factually coherent, explain why instead of answering something not correct. If you don't know the answer to a question, please don't share false information.
What is A 26-year-old woman with multiple sclerosis comes to the physician because of a recent relapse Examination of the eye movements shows slow adduction of the left eye with an associated right-beating nystagmus in the right eye. 

Which of the following is the location of the pathology that underlies this abnormality? and explain in detail?
None