A male of 50 years is having cramping in lower limbs with tingling and numbness for many years, his symptoms have now progressed with bearable pain an?

See a neurologist: The lesion could be in the spinal cord (most likely cervical or lumbar, less likely thoracic), in the lumbar roots, or in the peripheral nerves. Your description is insufficient. A complete history & neurologic exam by a neurologist are essential to localize the lesion & then diagnose the problem. In neurology it's ALWAYS "where" first, THEN "what." Never trust a "what" without a "where" first.