Intracranial neurostimulation for pain control: a review

Intracranial neurostimulation for pain relief is most frequently delivered by stimulating the motor cortex, the sensory thalamus, or the periaqueductal and periventricular gray matter. The stimulation of these sites through MCS (motor cortex stimulation) and DBS (deep brain stimulation) has proven effective for treating a number of neuropathic and nociceptive pain states that are not responsive or amenable to other therapies or types of neurostimulation. Prospective randomized clinical trials to confirm the efficacy of these intracranial therapies have not been published. Intracranial neurostimulation is somewhat different than other forms of neurostimulation in that its current primary application is for the treatment of medically intractable movement disorders. However, the increasing use of intracranial neurostimulation for the treatment of chronic pain, especially for pain not responsive to other neuromodulation techniques, reflects the efficacy and relative safety of these intracranial procedures. First employed in 1954, intracranial neurostimulation represents one of the earliest uses of neurostimulation to treat chronic pain that is refractory to medical therapy. Currently, 2 kinds of intracranial neurostimulation are commonly used to control pain: motor cortex stimulation and deep brain stimulation. MCS has shown particular promise in the treatment of trigeminal neuropathic pain and central pain syndromes such as thalamic pain syndrome. DBS may be employed for a number of nociceptive and neuropathic pain states, including cluster headaches, chronic low back pain, failed back surgery syndrome, peripheral neuropathic pain, facial deafferentation pain, and pain that is secondary to brachial plexus avulsion. The unique lack of stimulation-induced perceptual experience with MCS makes MCS uniquely suited for blinded studies of its effectiveness. This article will review the scientific rationale, indications, surgical techniques, and outcomes of intracranial neuromodulation procedures for the treatment of chronic pain.