Within the right aspect of the L4 vertebral body is a well-defined low T1 and mixed low and high T2 signal lesion extending into the right transverse process, pedicle and lamina. Extension into the superior endplate also noted. This lesion is expansile with right L4/5 neural exit foramen narrowing, and demonstrates avid contrast enhancement. There is contact of the exiting right L4 nerve root at this level.
In the anterior aspect of this vertebral body there is a smaller, well-defined lesion with low T1 signal and relatively isointense T2 signal, which demonstrates contrast enhancement.
Minor L4/5 and L5/S1 disc bulge without spinal canal narrowing. The left L4/5 and bilateral L5/S1 neural exit foramen are capacious.
Vertebral height, disc height, alignment and bone marrow signal are otherwise normal.
The conus terminates at the L2 level and is normal in appearance.
Conclusion:
Expansile, enhancing lesion at L4 consistent with known Fibrous Dysplasia.
The lesion narrows the L4/5 neural exit foramen with contact of the exiting right L4 nerve root at this level, which likely accounts for the patient's symptoms.