Progressive supranuclear palsy (PSP).

Moderate generalized cerebral , cerebellar atrophy with mild to moderate ventriculomegaly

Focal midbrain atrophy with reduced midbrain width to 0.7 cm in midsagittal plane , demonstrating reduced midbrain to pons width ratio of 0.33. ( hummingbird sign) – of concern for a neuro degenerative disorder , likely Progressive supranuclear palsy (PSP)

Other possibility of multisystem atrophy (MSA) cannot be ruled out.

No evidence of focal parenchymal lesion. No evidence of acute infarct or restricted diffusion on DWI.