2026 American Academy of Neurology Abstract Website

Objective:

To present a case of acute diethyltoluamide (DEET) toxicity with clinical presentation and imaging findings mimicking limbic encephalitis.

Background:

DEET is a chemical compound frequently used in insect repellents. Rare case reports exist of DEET toxicity leading to global cerebral edema. However, there is a paucity of cases describing other CNS involvement. Here we describe a case of DEET toxicity with findings on MRI brain mimicking limbic encephalitis.

Design/Methods:

N/A

Results:

A 29-year-old female presented to the emergency department via EMS with acute encephalopathy and agitation. She was tachycardic, hypertensive (158/98 mmHg), and had a one-time fever of 38.4 °C. Labs revealed elevated serum lactate (2.7 mmol/L), high sensitivity troponin (4392 ng/L), CK (3,825). Comprehensive serum drug screen was positive for DEET and THC. Video EEG showed continuous generalized slowing. MRI brain with and without contrast was completed showing FLAIR hyperintensity and restricted diffusion within bilateral hippocampi. Lumbar puncture was completed with normal CSF glucose, protein, and cell count. Additional CSF testing including viral/bacterial serology and autoimmune/paraneoplastic autoantibody panel were negative.

She was treated with empiric IVIG, 2g/kg over 5 days, while awaiting CSF autoimmune/paraneoplastic antibody panel. 10 days after her initial presentation, her encephalopathy and agitation began slowly improving, with gradual improvement over the next 4 weeks, though not completely returning to her baseline. She had limited recollection of the events prior to admission and could not report whether her DEET ingestion was accidental or intentional.

Conclusions:

DEET neurotoxicity is rarely reported in the literature, with the few cases reported having imaging findings of global cerebral edema. To our knowledge, this is the first reported case of DEET neurotoxicity with clinical presentation and imaging findings mimicking limbic encephalitis. This serves as a reminder to maintain a broad differential diagnosis, even in the presence of characteristic imaging findings suggestive of another condition.