You are dispatched to a residence for a 32-year-old woman who is complaining of a severe headache and blurry vision in her left eye. When you arrive at the scene, she meets you at the door and leads you toward the kitchen. As you follow her, you notice that she appears to be relying on the wall to assist her balance. When you question her, she tells you that the headache began the previous day and got worse as the day went on, forcing her to leave work early. When she awoke this morning, she noticed the dizziness and vision change in her eye and decided not to drive herself to the doctor. She denies any history of trauma. As you perform your examination, you notice that she winces when you touch the left parietal area of her head. When asked, she remembers that she was struck on the left side of the head by an object that she thought was thrown by a lawn mower as she walked past it three days ago while walking her dog. She states that the object did not hurt very much, so she figured it was unimportant and forgot about it. With the provided information, on which field diagnosis would you base your treatment plan?