Yesterday's Shortcuts are Today's Nightmares: Dangers of Presuming Idiopathic Intracranial Hypertension Without a Lumbar Puncture

Idiopathic intracranial hypertension (IIH) is characterized by papilledema in the setting of elevated intracranial pressure (ICP) and predominantly occurs in young obese women. Diagnosis is confirmed with lumbar puncture (LP) showing elevated cerebrospinal fluid-opening pressure (CSF-OP) and normal CSF contents without evidence of other intracranial etiologies on MRI/MRV. Despite strict diagnostic criteria,1 some argue that IIH can be diagnosed without an LP, the diagnosis purely based on the presence of papilledema, body habitus, clinical symptoms and radiologic signs of increased ICP.2,3 This is a timely question as the incidence of obesity continues to rise (with nearly 1 of 2 US-adults projected to be obese in 2030).4 We present 3 cases where LP was critical in the diagnosis of non-IIH pathologies in patients who were diagnosed with IIH prior to LP.

Poster 62 Yesterday’s Shortcuts Are Today’s Nightmares: Dangers of Presuming Idiopathic Intracranial Hypertension without a Lumbar Puncture Amy (Mung Yan) Lin1, Sachin Kedar1, Nancy Newman1, Valerie Biousse1 1 Emory University School of Medicine, Atlanta, Georgia, USA Introduction: Idiopathic intracranial hypertension (IIH) is characterized by papilledema in the setting of elevated intracranial pressure (ICP) and predominantly occurs in young obese women. Diagnosis is confirmed with lumbar puncture (LP) showing elevated cerebrospinal fluid-opening pressure (CSF-OP) and normal CSF contents without evidence of other intracranial etiologies on MRI/MRV. Despite strict diagnostic criteria,1 some argue that IIH can be diagnosed without an LP, the diagnosis purely based on the presence of papilledema, body habitus, clinical symptoms and radiologic signs of increased ICP.2,3 This is a timely question as the incidence of obesity continues to rise (with nearly 1 of 2 US-adults projected to be obese in 2030).4 We present 3 cases where LP was critical in the diagnosis of non-IIH pathologies in patients who were diagnosed with IIH prior to LP. Description of Case(s): Case 1. 36 year-old woman (BMI 58) with headaches, papilledema and elevated CSF-OP was started on acetazolamide with a presumed diagnosis of IIH. CSF studies ultimately showed pleocytosis with positive herpes simplex virus (HSV) PCR. She was treated for HSV meningitis. Case 2. 27 year-old woman (BMI 24) with headaches, papilledema, normal brain imaging and elevated CSF-OP. She was diagnosed with carcinomatous meningitis revealing a primary CNS neuroendocrine tumor. Case 3. 55 year-old man (BMI 35) with headaches, papilledema, elevated CSF-OP and an empty sella. CSF studies allowed the diagnosis of neuro-syphilis in the setting of a new HIV diagnosis. Conclusions, including unique features of the case(s): LP with CSF analysis and CSF-OP is crucial in presumed IIH patients to avoid a detrimental misdiagnosis and to initiate appropriate treatment.1,5 Furthermore, the LP, which induces an immediate dramatic decrease in CSF-OP beyond the threshold level of the unstable CSF equilibrium present in IIH, can result in reset of the CSF-pressure, a lower stable pressure state, and is the first step in treatment of IIH prior to initiating acetazolamide.6 References: 1. Friedman DI, Liu GT, Digre KB. Revised diagnostic criteria for the pseudotumor cerebri syndrome in adults and children. Neurology, 81(13), 1159-65, 2013. 2. Bidot, Samuel et al. Brain Imaging in Idiopathic Intracranial Hypertension, Journal of Neuro-Ophthalmology, 35(4), 400-411, 2015. 3. Margolis MS et al. Lumbar puncture for diagnosis of idiopathic intracranial hypertension in typical patients. Journal of Neuro-Ophthalmology, 41, 375-8, 2021. 4. Ward ZJ et al. Projected U.S. State-level prevalence of adult obesity and severe obesity. N Engl J Med, 381, 2440-50, 2019. 5. Mollan SP et al. Idiopathic intracranial hypertension: consensus guidelines on management. J Neurol Neurosurg Psychiatry, 89, 1088-100, 2018. 6. Bateman GA, Stevens SA, Stimpson J. A mathematical model of idiopathic intracranial hypertension incorporating increased arterial inflow and variable venous outflow collapsibility. J Neurosurg, 110, 446–456, 2009. Keywords: pseudotumor cerebri, high intracranial pressure/headache Financial Disclosures: The authors had no disclosures. Grant Support: None. Contact Information: None provided. 126 | North American Neuro-Ophthalmology Society