American Board of Internal Medicine (ABIM) Certification Practice Exam

The diagnosis of Idiopathic Intracranial Hypertension (Pseudotumor Cerebri) is confirmed by a CSF opening pressure greater than what level?

1. 200 mm H2O

2. 250 mm H2O

3. 300 mm H2O

4. 350 mm H2O

The correct answer is: 250 mm H2O

The diagnosis of Idiopathic Intracranial Hypertension (IIH), also known as pseudotumor cerebri, is confirmed through a lumbar puncture, where the opening pressure of the cerebrospinal fluid (CSF) is evaluated. A CSF opening pressure greater than 250 mm H2O is typically considered supportive of the diagnosis of IIH. In clinical practice, the standard threshold for diagnosing IIH has been established at this level, where patients usually present with symptoms such as headaches, visual disturbances, or other neurological signs linked to increased intracranial pressure. It is important to note that elevated CSF opening pressures alone are not indicative of IIH, as other conditions can also present with increased pressure. Hence, a thorough clinical correlation and consideration of other findings (like the visual field tests and the absence of identifiable secondary causes for increased intracranial pressure) are essential for accurate diagnosis. The emphasis on the 250 mm H2O mark aligns with established guidelines and the collective clinical experience that this pressure level is significant in identifying those with IIH, leading to further management and monitoring of the condition.