A 31-year-old woman with a two-week history of new-onset headaches experiences pain that worsens when lying down but occurs during various activities throughout the day. She has no accompanying symptoms like nausea or vision changes. Despite trying over-the-counter pain relievers, her headaches persist. She has an unremarkable medical history and no prior headaches. She's currently on isotretinoin and vitamin A supplements for acne treatment. Her temperature is 98.5 °F (36.9 °C), her heart rate is 60 beats/min, her blood pressure is 120/60 mm Hg, and her respiration rate is 16 breaths/min. Her Neurological and ophthalmologic exams are normal except for papilledema in the right eye. Electrolyte levels and a complete blood cell count are normal. The results of a brain CT scan are also normal. Which of the following diagnoses is most likely,