There are various problems associated with the use of intrathecal pumps. Withdrawal from the delivered medication, accidental over sedation or overdose are often caused by human error. Withdrawal can happen when the amount of medication remaining in the pump is miscalculated and runs out. Delivering too much medication can result in accidental over sedation or even overdose. The pump itself can malfunction. Newer units are proving to be more reliable however. Catheter tubing that is attached to the pump and then placed near the spinal cord can break, become clogged or dislodged. A newer complication that has been recognized is the formation of an inflammatory mass called a granuloma at the catheter tip. This can be the source of more serious neurological deficits.