2025 American Academy of Neurology Abstract Website

Objective:

We present a novel case of encephalopathy following isolated levamisole ingestion to better characterize the clinical and radiographic findings of levamisole-associated multifocal inflammatory leukoencephalopathy.

Background:

Levamisole is a synthetic imidazothiazole first developed in 1966 for use as an anthelmintic. Levamisole was removed from the US market in 2000 due to concerns regarding agranulocytosis, vasculitis and leukoencephalopathy. Despite its removal from US and Canadian markets, levamisole continues to be available with or without a medical prescription in other countries and has been increasingly used as an adulterant in cocaine and other illicit substances. Although very rare, levamisole-associated multifocal inflammatory leukoencephalopathy remains a severe and devastating central nervous system adverse effect following levamisole exposure.

Design/Methods:

Case study

Results:

Brain MRI showed multiple diffusely increased T2/FLAIR signal abnormalities with enhancement in the bilateral cerebral hemispheres, confluent hyperdense lesions at the gray-white junction across the bilateral frontal and temporal lobes. Cerebrospinal fluid (CSF) analysis showed elevated protein without pleocytosis. Microbiological testing for a wide array of bacterial, viral and fungal pathogens was unremarkable, as was testing for heavy metals, paraneoplastic and autoimmune antibodies and free light chains.

After treatment with intravenous methylprednisolone and PLEX, patient showed significant improvement.

Three months after the initial clinical presentation, the patient’s cognitive-linguistic skills were improved in all measured domains. Both brain MRI (6/10/24) and EEG (5/13/24) showed remarkable improvement.

Conclusions:

In patients presenting with encephalitis-like symptoms, an extensive history should be taken regarding supplement and drug use, especially among people with recent travel to countries endemic for parasitic infections, where it is available with or without a prescription. Although levamisole-adulterated cocaine has been more commonly seen in the US, clinicians should also be aware of sole ingestion of levamisole as a possible cause of encephalopathy.