My Husband Had An MRI Of The Spine Due To

My husband had an MRI of the spine due to sciatica pain. The MRI showed a herniated disc and four bulging discs. In addition, it said he had a heterogenous lesion in the L5-S1 pars interarticularis and sclerotic lesion of uncertain etiology. What does that mean? This is a 70 year old male. Ht. 6 feet - weight 217. Thank you