Pseudo tumour cerebri is caused by all except:
**Core Concept**
Pseudo tumor cerebri, also known as idiopathic intracranial hypertension (IIH), is a condition characterized by increased intracranial pressure (ICP) without any detectable cause, such as a tumor. This condition is often associated with obesity, female sex, and the use of certain medications.
**Why the Correct Answer is Right**
The pathophysiology of pseudo tumor cerebri involves impaired cerebrospinal fluid (CSF) absorption, leading to increased ICP. This can be caused by various factors, including obesity, which is known to be a significant risk factor. Obesity is associated with increased inflammation and oxidative stress, which can damage the arachnoid villi and granulations, leading to impaired CSF absorption.
**Why Each Wrong Option is Incorrect**
**Option A:** **Tetracycline antibiotics** are known to cause pseudo tumor cerebri as a side effect, particularly in young women. This is thought to be due to the inhibition of CSF absorption by these medications.
**Option B:** **Vitamin A toxicity** can cause pseudo tumor cerebri by promoting the differentiation of astrocytes, leading to increased ICP.
**Option C:** **Oral contraceptives** are also associated with an increased risk of developing pseudo tumor cerebri, particularly in women who are overweight or obese.
**Clinical Pearl / High-Yield Fact**
Pseudo tumor cerebri is often associated with a "empty sella" sign on MRI, which is a result of the herniation of the subarachnoid space into the sella turcica.
**Correct Answer:** D.