This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cerebrovascular Diseases, Subject name: Surgery
[{'content': 'A right-sided disc herniation at the L5-S1 level typically may cause: \nSelect and explain. \nA. Low back pain and right sciatica, B. Weakness of dorsiflexion of the right foot, C. A preserved right ankle jerk, D. Diminution of sensation over the medial aspect of the right foot, including the great toe', 'role': 'user'}, {'content': 'Answer: A \nExplanation: A lumbar disc herniation at the L5-S1 or L4-L5 level typically causes low back pain and ipsilateral sciatica. If a ruptured L5-S1 disc causes weakness, it ordinarily involves plantar flexion of the ipsilateral foot. Although a diminished or absent ankle jerk can be caused by either an L5-S1 or an L4-L5 disc herniation, it is more common with the former. The L5-S1 disc herniation ordinarily affects the S1 nerve root, which supplies the lateral aspect of the foot, including the small toe.', 'role': 'assistant'}]