title: Toxic leukoencephalopathies, including drug, medication, environmental, and radiation-induced encephalopathic syndromes.
abstract: Toxic leukoencephalopathies can be secondary to the exposure to a wide variety of exogenous agents, including cranial irradiation, chemotherapy, antiepileptic agents, drugs of abuse, and environmental toxins. There is no typical clinical picture, and patients can present with a wide array of signs and symptoms. Involvement of white matter is a key finding in this scenario, although in some circumstances other high metabolic areas of the central nervous system can also be affected. Magnetic resonance (MR) imaging usually discloses bilateral and symmetric white matter areas of hyperintense signal on T2-weighted and fluid-attenuated inversion recovery images, and signs of restricted diffusion are associated in the acute stage. In most cases, the changes are reversible, especially with prompt recognition of the disease and discontinuation of the noxious agent. Either the MR or clinical features may be similar to several nontoxic entities, such as demyelinating diseases, leukodystrophies, hepatic encephalopathy, vascular disease, hypoxic-ischemic states, and others. A high index of suspicion should be maintained whenever a patient presents recent onset of neurologic deficit, searching the risk of exposure to a neurotoxic agent. Getting to know the most frequent MR appearances and mechanisms of action of causative agents may help to make an early diagnosis and begin therapy, improving outcome. In this review, some of the most important causes of leukoencephalopathies are presented; as well as other 2 related conditions: strokelike migraine attacks after radiation therapy syndrome and reversible splenial lesions.
authors.affiliation: Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Carolina de Medeiros
authors.initials: Cde M
authors.lastname: Rimkus
authors.affiliation: Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Celi Santos
authors.initials: CS
authors.lastname: Andrade
authors.affiliation: Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil.
authors.forename: Claudia da Costa
authors.initials: Cda C
authors.lastname: Leite
authors.affiliation: Department of Radiology/Neuroradiology, University of Minnesota and Hennepin County Medical Centers, Minneapolis, MN.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: McKinney
authors.affiliation: Department of Radiology, Faculdade de Medicina da Universidade de São Paulo, São Paulo, Brazil. Electronic address: ltlucato@uol.com.br.
authors.forename: Leandro Tavares
authors.initials: LT
authors.lastname: Lucato
mesh_terms: D000970:Antineoplastic Agents / Q000009:adverse effects*; D004785:Environmental Pollutants / Q000506:poisoning*; D006801:Humans; D056784:Leukoencephalopathies / Q000209:etiology* / Q000473:pathology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D011832:Radiation Injuries / Q000175:diagnosis / Q000209:etiology*; D020266:Radiotherapy, Conformal / Q000009:adverse effects; D019966:Substance-Related Disorders / Q000150:complications* / Q000175:diagnosis; D013577:Syndrome
chemical_list: D000970:Antineoplastic Agents; D004785:Environmental Pollutants