Table 2.

Differential table for pontine radiation necrosis

Pontine lesion	MRI T1 signal	MRI T2 signal	Other MRI features	MRS	Nuclear Imaging
Radiation necrosis	Low	High, extending beyond area of irradiation	Round, irregular, “Soap bubble” or “Swiss cheese” appearance. Nodular or peripheral contrast enhancement. Increased diffusion on DWI. Decreased perfusion and blood volume.	Elevated lactate and lipid peaks with reduced NAA, choline, and creatine peaks	Reduced uptake on 18FDG-PET, 11C- MET PET, 123IMT SPECT and 201Tl SPECT
High-grade glioma	Normal or low	High	Peripheral contrast enhancement (may be uniform in low grade). Increased perfusion and blood volume. Restricted diffusion on DWI.	Lactate may be elevated if necrosis present, decreased NAA and increased choline	Increased uptake on 18FDG-PET, 11C-MET PET, 123IMT SPECT and 201Tl SPECT
Primary lymphoma CNS	Normal or low	Low, normal or high	Irregular contrast enhancement. Increased perfusion and blood volume. Restricted diffusion on DWI.	Elevated lactate and lipid peaks with decreased NAA and creatine, increased choline	Increased uptake on 18FDG-PET, 11C-MET PET, 123IMT SPECT and 201Tl SPECT
Toxoplasmosis	Low	Low, normal or high	Nodular or peripheral contrast enhancement. Restricted diffusion on DWI.	Elevated lactate and lipids with absence of other metabolites	Reduced uptake on 18FDG-PET, 99mTc SPECT, 201Tl SPECT and sestamibi SPECT
Listerial/viral rhomb-encephalitis	Normal or low	High	Patchy, peripheral, gyriform or leptomeningeal contrast enhancement. Increased diffusion on DWI.	Not adequately studied	Reduced uptake on 99mTc SPECT