A 33-year-old woman complains of generalized, throbbing headache that is worse in the morning and with coughing. She occasionally feels dizzy and nauseated. Examination is significant only for obesity and bilateral papilledema. CT scan of the head is nominal. At lumbar puncture the opening pressure is 220 mm H2O; CSF is clear, with protein of 12 mg/100 mL (normal is 15 to 45), glucose of 68 mg/100 mL (normal is 45 to 80), an d no cells are seen. The most likely diagnosis is:

**Core Concept**
The patient's symptoms and signs, including headache, dizziness, nausea, bilateral papilledema, and elevated opening pressure, suggest an abnormality in cerebrospinal fluid (CSF) dynamics, likely due to impaired CSF reabsorption.

**Why the Correct Answer is Right**
The patient's CSF analysis shows normal protein, glucose, and cell counts, which makes an infectious or inflammatory process less likely. The elevated opening pressure with normal CSF analysis is characteristic of idiopathic intracranial hypertension (IIH), also known as pseudotumor cerebri. This condition is thought to result from a combination of impaired CSF reabsorption and increased intracranial pressure, possibly related to obesity and hormonal factors.

**Why Each Wrong Option is Incorrect**
**Option A:** This option is not provided, but based on the clinical scenario, conditions like subarachnoid hemorrhage, meningitis, or brain tumor would typically present with abnormal CSF analysis or other localizing signs.

**Option B:** This option is not provided, but conditions like normal pressure hydrocephalus would typically present with a triad of gait disturbance, dementia, and urinary incontinence, which are not seen in this patient.

**Option C:** This option is not provided, but conditions like cerebral venous sinus thrombosis would typically present with signs of increased intracranial pressure and focal neurological deficits, which are not seen in this patient.

**Option D:** This option is not provided, but conditions like Chiari malformation would typically present with signs of brainstem compression and other localizing neurological signs, which are not seen in this patient.

**Clinical Pearl / High-Yield Fact**
Idiopathic intracranial hypertension is a condition that predominantly affects young, obese women and is characterized by elevated intracranial pressure without a clear cause, often presenting with headache and visual disturbances.

**Correct Answer: C. Idiopathic intracranial hypertension.**

✓ Correct Answer: D. Pseudotumor cerebri