Hi Jayne, Welcome to HealthcareMagic Forum.
Since you said you have Prolapsed Discs, there might be some amount of Nerve compression of nerves which are arising from the spinal cord
. The itching which you are suffering from is indeed due to this nerve compression and is called Brachioradial Pruritus
which happens if there is nerve damage
. Kindly consult a Orhtopedist at the earliest as he shall examine you and prescribe medications like, anti depressants, anti convulsants, creams for Local application or Local anesthetics.