Indications:
Peripheral nerve stimulation (PNS) is a neuromodulation technique where electrical current is applied to peripheral nerves to relieve chronic pain. A variety of techniques have been developed since 1967, and applied to various pain problems.
Examples include occipital nerve stimulation and subcutaneous peripheral nerve stimulation. Occipital neuralgia and supraorbital neuralgia are common disorders treated with cranial PNS.
Tibial neuralgia and inguinal neuralgia are extremity and trunk peripheral nerve disorders which respond well to treatment with PNS. Cranial peripheral nerve stimulation is currently being investigated for the treatment of a variety of headache disorders, including migraines and cluster headache.
Technique:
Similar to other forms of neurostimulation, patients undergo a psychological screening to rule out psychological amplifiers of pain, such as depression and substance abuse. The use of a local anesthetic injection along the peripheral nerve may be used as a screening tool to select those patients who are most suitable for PNS. The effectiveness of this as a screening tool is still to be determined.
A trial period generally lasts about a week (using temporary electrodes). Depending on the outcome, a permanent system may be implanted. Depending on the physician, either percutaneous or paddle leads may be used. Paddle leads appear to be less prone to migration, such as for spinal cord stimulation. This is fairly important, as PNS electrodes could be located in areas of excessive movement and stress.
For superficial peripheral nerves, such as the occipital nerves, individual leads are placed just below the skin, overlying the nerves. Fluoroscopic guidance may be used. Intraoperative testing confirms that stimulation is in the appropriate location.
For larger peripheral nerves, an open approach is generally used to lessen the risk of injury. The target nerve is subjected to an external neurolysis, and the leads are placed in the vicinity of the nerve. If a paddle lead is used, a layer of fascia is left between the nerve and the electrode array to lessen the painful levels of direct stimulation.
The permanent leads are connected to an implantable pulse generator and intraoperative testing confirms appropriate coverage.
