The objective is to highlight the diagnostic challenges of identifying toxic leukoencephalopathy due to opioid exposure, emphasizing the importance of thorough patient history and recognizing less common causes associated with fentanyl and "Chasing the dragon."

A 24-year-old woman with a history of migraines, anorexia, anxiety, depression, marijuana use, and tobacco vaping presented with a 3-day history of slurred speech, cognitive slowing, and generalized weakness. Her symptoms, including "cognitive fog" and the need for assistance with ambulation, worsened over time. She also reported increased urinary frequency and occasional vomiting. Examination revealed bradyphrenia, mild dysarthria, generalized weakness, ataxia, bradykinesia, hyperreflexia, and a positive Romberg test.

During hospitalization, a positive urine drug screen for fentanyl and norfentanyl supported the diagnosis of toxic leukoencephalopathy. Blood tests revealed vitamin B12 and vitamin D deficiencies, while other lab results, including complete blood count, liver function tests, and CSF studies, were normal. MRI of the neuro-axis showed mild cerebral volume loss and multiple symmetric bilateral cerebral white matter hyperintensities, extending into the gray matter of the spinal cord.

Further investigation with the patient and family members revealed a prolonged history of using "Blues," a street drug often containing fentanyl, oxycodone, and other opioids, typically inhaled using aluminum foil. This history led to the consideration of a diagnosis of toxic leukoencephalopathy (TL).

The prognosis of toxic leukoencephalopathy varies widely, influenced by factors such as exposure duration, patient age, organ function, and existing health conditions. This case report emphasizes the importance of a thorough history for accurate diagnosis and highlights fentanyl and blue heroin as additional causes of “Chasing the dragon.”