Electroencephalography Correlates of Intracranial Hypertension in 4 Patients with Leptomeningeal Metastases (P4.219)

OBJECTIVE: To characterize the electrographic features of transient neurological attacks associated with elevated intracranial pressure due to leptomeningeal metastases. BACKGROUND: Leptomeningeal metastases are uncommon complications of solid and hematologic malignancies. Transient neurological attacks in these patients may result from seizures or plateau waves_sustained periods of intracranial hypertension. Electroencephalography (EEG) is a useful tool to distinguish these two entities, though few descriptions exist of the EEG correlates of plateau waves in patients with leptomeningeal metastasis. DESIGN/METHODS: We retrospectively reviewed the charts and video-EEGs of four patients with leptomeningeal metastasis, diagnosed with intracranial hypertension after presenting with recurrent transient neurological attacks. Video-EEG recordings were reviewed for clinical events and temporally associated EEG changes. RESULTS: The background EEG for all revealed mild to moderate diffuse slowing, symmetric N2 sleep transients, and absence of focal findings or epileptiform discharges. In total, 42 clinical events were captured on video-EEG. Phenotypic features of clinical events were stereotyped for each patient, including decreased responsiveness (3/4), neck arching (1/4), arm stiffening (1/4), and/or nausea and dizziness (1/4). For 34/42 (81[percnt]), a clear electrographic correlate preceded the clinical event by six seconds to two minutes and was characterized by >30[percnt] increase in diffuse polymorphic theta and delta frequency range slowing compared to baseline. These findings persisted for 10 seconds to 14 minutes with a mean duration of five minutes. Events were not associated with focal findings, epileptiform discharges, evolution, or N2 sleep transients. CONCLUSIONS: The electrographic correlates of transient neurological attacks from intracranial hypertension are unmistakably distinct from seizures and vital for proper diagnosis and management of patients with leptomeningeal metastasis. Future prospective studies of transient neurological attacks in these patients can validate the sensitivity and specificity of EEG and clinical hallmarks, provide insight into the pathophysiology, or even guide management of intracranial hypertension from leptomeningeal metastases. Disclosure: Dr. Gold has nothing to disclose. Dr. Odom has nothing to disclose. Dr. Haggiagi has nothing to disclose. Dr. Schaff has nothing to disclose. Dr. Odia has nothing to disclose.