Symmetrical cerebral restricted diffusion is seen in a broad range of pathologies. The differential depends on the location of the lesions.

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 centrum semiovale lesions

• methotrexate encephalopathy: bilateral symmetric high signal and diffusion restriction lesions at the centrum semiovale

• mild encephalopathy with reversible splenial lesion (MERS), involves the splenium of the corpus callosum with high signal and diffusion restriction, sometimes with diffuse involvement of the corpus callosum and bilateral symmetrical lesions at the centrum semiovale

• genetic disorders such as Charcot-Marie-Tooth disease

Symmetrical basal ganglia lesions

• Leigh syndrome

  • the 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

  • the 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

  • affetcs putamen and caudate nuclei

• ethylene glycol toxicity

  • basal ganglia and thalami, brainstem as well as amygdala and hippocampi

• hypoglycaemic encephalopathy

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

• hypoxic-ischaemic brain injury

• extrapontine myelinolysis

  • it is generally associated with central pontine myelinosis, but can (rarely) be isolated, it shows symmetrical restricted diffusion in the basal ganglia, the internal, external, and extreme capsule

Symmetrical thalamic and mamillary bodies lesions

• Creutzfeldt-Jakob disease

• acute disseminated encephalomyelitis (ADEM)

• Wernicke encephalopathy

  • symmetrical restricted diffusion 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

• heroin-induced leukoencephalopathy

Symmetrical temporal or insular lesions

• hepatic encephalopathy

  • symmetric retricted diffusion within the insula, thalamus, and posterior limbs of the internal capsule, and cingulate gyrus

• herpes simplex encephalitis ⁴

  • It's generally asymmetrical but symmetrical lesions may be seen ⁴

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