Why is local anaesthetic used in a nerve root block?

A small amount is placed near the nerve root under image guidance. It reduces the nerve's ability to carry pain messages for a limited period, which may make movement or examination easier. A noticeable, short-lived change can give the treating team useful diagnostic information, although it does not by itself prove the only cause of back or leg pain. The injection may also include another medicine intended to calm irritation; that medicine has a different, slower role.

Follow the clinic's instructions about medicines, eating, transport and activity. Tell the team about allergies, blood-thinning medicines, diabetes, infection, pregnancy or new weakness before the procedure. Arrange a safe way home if your leg feels numb or weak, and avoid driving until normal sensation and control have returned. Note your pain and function before and after the block so you can describe the change accurately.

Contact the treating service promptly for worsening weakness, spreading numbness, severe or increasing pain, fever, or redness and drainage at the injection site. Seek urgent medical help for new loss of bladder or bowel control, numbness around the groin, fainting that does not settle, or trouble breathing. Temporary numbness can occur, but it should be discussed if it is not improving as expected.

Which nerve root is being targeted, and what finding led you to choose it? How long might the numbness last? What result would count as useful information? Which activities should I avoid today, and what symptoms require an urgent call?