Utility of Intracranial Pressure Monitoring for Diagnosis of Idiopathic Intracranial Hypertension in the Absence of Papilledema

Background: Idiopathic intracranial hypertension (IIH) is characterized by headaches, visual obscurations, and papilledema, and the diagnosis involves lumbar puncture (LP) with an elevated opening pressure (OP) ≥20 cm H₂0. When papilledema is absent, the diagnosis becomes less clear. Some physicians have argued that the absence of papilledema rules out IIH, whereas others maintain that elevated OP is sufficient for diagnosis. Methods: The authors performed a single-institution 4-year retrospective analysis of patients who underwent invasive intracranial pressure (ICP) monitoring for presumed IIH. Results: A total of 22 patients were reviewed, and 13 had classic symptoms of IIH, documented elevated OP, and absence of papilledema; 5/13 (38%) patients had proven intracranial hypertension as shown by invasive ICP monitoring, whereas 8/13 (62%) had normal ICP. Conclusions: With the use of current diagnostic algorithms of clinical presentation and elevated OP, over half of patients without papilledema in our series would be falsely diagnosed with IIH, which could result in unnecessary medical and surgical intervention. Thus, elevated OP as determined by LP is insufficient to diagnose IIH. On the other hand, the absence of papilledema does not rule out intracranial hypertension.