INTRODUCTIONRadiologists may encounter bilaterally symmetrical abnormalities of the basal ganglia on magnetic resonance imaging (MRI), typically in the context of diffuse systemic, toxic or metabolic diseases. A systematic approach and broad knowledge of pathology causing this uncommon group of conditions would be useful.

MATERIALS AND METHODSThis review uses illustrative images to highlight metabolic conditions, such as Leigh's syndrome, citrullinaemia, hypoglycaemia or carbon monoxide poisoning, as well as other causes of bilateral basal ganglia lesions such as osmotic myelinolysis, deep cerebral venous thrombosis and Creutzfeldt-Jakob disease.

RESULTSCareful assessment of radiological findings outside the basal ganglia, such as involvement of the cortex, white matter, thalamus and pons, together with clinical correlation, may be helpful in narrowing the differential diagnosis, and directing further radiological, biochemical or genetic investigations. Recent advances in MR technology have resulted in newer techniques including diffusion-weighted (DW) MR imaging and MR spectroscopy (MRS); these may be helpful if appropriately used.

CONCLUSIONSAbnormal MRI findings in the basal ganglia should not be interpreted in isolation. A systematic approach including DW MR imaging, MRS, and a broad knowledge of diffuse systemic, toxic or metabolic diseases is helpful.