Symmetrical cerebral T2/FLAIR hyperintensities are seen in a broad range of pathologies. The differential depends essentially on the location of the lesions.

Symmetrical corticospinal tract lesions

• amyotrophic lateral sclerosis: symmetrical T2/FLAIR hyperintensities along the corticospinal tract from the cortices extending inferiorly to the brainstem and finally into the anterolateral column of the spinal cord

Symmetrical central tegmental tract lesions

• central tegmental tract T2 hyperintensity : symmetrical hyperintensities of the extrapyramidal tract connecting the red nucleus and the inferior olivary nucleus ¹

Symmetrical basal ganglia lesions

• Leigh syndrome: distribution tends to be symmetrical in periaqueductal grey matter, medulla, brainstem, midbrain, putamen (not always present, but characteristic), globus pallidus, heads of the caudate nucleus, substantia nigra, subthalamic nuclei and thalami

• carbon monoxide poisoning: globus pallidus is most commonly affected

• methanol poisoning: involves usually the putamen, optic nerves, and retina, but can also affect other basal ganglia nuclei, subcortical white matter, and cerebellum

• cyanide poisoning: affects the basal ganglia, especially the striatum; the sensorimotor cortex may also be involved

• organophosphate poisoning: affects putamen and caudate nuclei

• ethylene glycol toxicity: basal ganglia and thalami, brainstem as well as amygdala and hippocampi

• hypoglycemic encephalopathy: can involve the posterior limb of the internal capsule, cerebral cortex (specifically the insula and parieto-occipital), hippocampi, and/or basal ganglia

• uremic encephalopathy: symmetrical lesions in the basal ganglia, thalamus, midbrain, and mesial temporal lobes

• hypoxic-ischemic brain injury

• extrapontine myelinolysis: generally associated with central pontine myelinolysis, but can (rarely) be isolated, it shows symmetrical lesions in the basal ganglia, the internal, external, and extreme capsule

• Wilson disease: involves basal ganglia (especially putamen), followed by midbrain, pons, and thalami ²

Symmetrical thalamic and mamillary bodies lesions

• pulvinar sign: symmetrical bilateral T2/FLAIR hyperintensities involving the pulvinar thalamic nuclei

  • Creutzfeldt-Jakob disease

  • acute disseminated encephalomyelitis (ADEM)

  • status epilepticus

• Wernicke encephalopathy: symmetrical lesions in mammillary bodies, dorsomedial thalami, tectal plate, periaqueductal grey matter, around the third ventricle

Symmetrical hippocampi lesions

• CHANTER syndrome

• opioid-associated amnestic syndrome

Symmetrical pontine lesions

• osmotic demyelination syndrome: located at the central portion of the pons

• poliomyelitis-like syndrome: symmetric hyperintensities within the pons, substantia nigra, medulla, anterior horns of the spinal cord, and ventral nerve roots ³

• ^​LBSL: symmetrical lesions involving the posterior limbs of the internal capsules, the tracts of the trigeminal nerves, cerebellum, the dorsal columns and lateral corticospinal tracts of the medulla oblongata and spinal cord

• heroin-induced leukoencephalopathy

Symmetrical middle cerebellar peduncle lesions

Please refer to our article on the middle cerebellar peduncle sign for the differentials of symmetrical lesions in this region.

Symmetrical temporal or insular lesions

• hepatic encephalopathy: symmetric high signal within the insula, thalamus, and posterior limbs of the internal capsule, and cingulate gyrus

• herpes simplex encephalitis: generally asymmetrical but symmetrical lesions may be seen ⁴

• Wilson disease

Symmetrical cerebellar lesions

• Leigh syndrome: may involve the dentate nuclei, inferior cerebellar peduncles, periaqueductal grey matter, medulla, brainstem, midbrain, basal ganglia, substantia nigra, and thalami

• CHANTER syndrome

• heroin-induced leukoencephalopathy