A 23-year-old woman complains of progressive loss of vision and papilledema. Investigations show normal findings on CT scan. A lumbar puncture shows marked elevation of pressure. What is the most likely diagnosis?
**Core Concept**
The patient's presentation of progressive loss of vision and papilledema, combined with elevated cerebrospinal fluid (CSF) pressure on lumbar puncture, suggests an obstruction of CSF flow within the central nervous system (CNS). This condition can lead to increased intracranial pressure (ICP) and subsequent visual disturbances.
**Why the Correct Answer is Right**
The correct diagnosis is likely a condition that affects the brain's ventricular system or the subarachnoid space, where CSF circulates. The normal CT scan findings rule out acute hemorrhage or significant mass lesions. The increased CSF pressure on lumbar puncture indicates a blockage in CSF reabsorption or circulation. A possible cause is a condition that affects the arachnoid granulations or the choroid plexus.
**Why Each Wrong Option is Incorrect**
* **Option A:** This choice is incorrect because it does not directly relate to the patient's symptoms of progressive vision loss and elevated CSF pressure. While aseptic meningitis can cause increased CSF pressure, it typically presents with symptoms such as headache, fever, and stiff neck.
* **Option B:** This choice is incorrect because it does not account for the patient's normal CT scan findings. While a brain tumor could cause increased ICP and vision loss, the normal CT scan makes this diagnosis less likely.
* **Option D:** This choice is incorrect because it does not directly relate to the patient's symptoms of progressive vision loss and elevated CSF pressure. While a subdural hematoma can cause increased ICP, it typically presents with symptoms such as headache and altered mental status.
**Clinical Pearl / High-Yield Fact**
In cases of suspected increased ICP, it is essential to perform a lumbar puncture to assess CSF pressure and composition. A normal CT scan does not rule out conditions that can cause increased ICP, such as idiopathic intracranial hypertension (IIH) or pseudotumor cerebri.
**Correct Answer: C. Idiopathic Intracranial Hypertension (IIH)**