Electrical stimulation systems may be used to deliver electrical stimulation therapy to patients to treat a variety of symptoms or conditions such as chronic pain, tremor, Parkinson's disease, multiple sclerosis, spinal cord injury, cerebral palsy, amyotrophic lateral sclerosis, dystonia, torticollis, epilepsy, pelvic floor disorders, or gastroparesis.  An electrical stimulation system typically includes one or more stimulation leads coupled to an external or implantable electrical stimulator.  The stimulation lead may be percutaneously or surgically implanted in a patient on a temporary or permanent basis such that at least one stimulation electrode is positioned proximate to a target stimulation site.  The target stimulation site may be, for example, a spinal cord, pelvic nerve, pudendal nerve, stomach, muscle, or within a brain or other organ of a patient.  The electrodes located proximate to the target stimulation site may deliver stimulation therapy to the target stimulation site in the form of electrical signals. 
Electrical stimulation of a sacral nerve may eliminate or reduce some pelvic floor disorders by influencing the behavior of the relevant structures, such as the bladder, sphincter and pelvic floor muscles.  Pelvic floor disorders include urinary incontinence, urinary urge/frequency, urinary retention, pelvic pain, bowel dysfunction, and male and female sexual dysfunction.  The organs involved in bladder, bowel, and sexual function receive much of their control via the second, third, and fourth sacral nerves, commonly referred to as S2, S3 and S4 respectively.  Thus, in order to deliver electrical stimulation to at least one of the S2, S3, or S4 sacral nerves, a stimulation lead is implanted proximate to the sacral nerve(s). 
Electrical stimulation of a peripheral nerve, such as stimulation of an occipital nerve, may be used to induce paresthesia.  Occipital nerves, such as a lesser occipital nerve, greater occipital nerve or third occipital nerve, exit the spinal cord at the cervical region, extend upward and towards the sides of the head, and pass through muscle and fascia to the scalp.  Pain caused by an occipital nerve, e.g. occipital neuralgia, may be treated by implanting a lead proximate to the occipital nerve to deliver stimulation therapy. 
In many stimulation applications, including stimulation of a sacral nerve, it is desirable for a stimulation lead to resist migration following implantation.  For example, it may be desirable for the electrodes disposed at a distal end of the implantable medical lead to remain proximate to a target stimulation site in order to provide adequate and reliable stimulation of the target stimulation site.  In some applications, it may also be desirable for the electrodes to remain substantially fixed in order to maintain a minimum distance between the electrode and a nerve in order to help prevent inflammation to the nerve and in some cases, unintended nerve damage.  Securing the stimulation lead at the target stimulation site may minimize lead migration.