Trigeminal and sphenopalatine ganglion stimulation for intractable craniofacial pain--case series and literature review.

INTRODUCTION: Facial pain is often debilitating and can be characterized by a sharp, stabbing, burning, aching, and dysesthetic sensation. Specifically, trigeminal neuropathic pain (TNP), anesthesia dolorosa, and persistent idiopathic facial pain (PIFP) are difficult diseases to treat, can be quite debilitating and an effective, enduring treatment remains elusive. METHODS: We retrospectively reviewed our early experience with stimulation involving the trigeminal and sphenopalatine ganglion stimulation for TNP, anesthesia dolorosa, and PIFP between 2010-2014 to assess the feasibility of implanting at these ganglionic sites. Seven patients received either trigeminal and/or sphenopalatine ganglion stimulation with or without peripheral nerve stimulation, having failed multiple alternative modalities of treatment. The treatments were tailored on the physical location of pain to ensure regional coverage with the stimulation. RESULTS: Fluoroscopy or frameless stereotaxy was utilized to place the sphenopalatine and/or trigeminal ganglion stimulator. All patients were initially trialed before implantation. Trial leads implanted in the pterygopalatine fossa near the sphenopalatine ganglion were implanted via transpterygoid (lateral-medial, infrazygomatic) approach. Trial leads were implanted in the trigeminal ganglion via percutaneous Hartel approach, all of which resulted in masseter contraction. Patients who developed clinically significant pain improvement underwent implantation. The trigeminal ganglion stimulation permanent implants involved placing a grid electrode over Meckel's cave via subtemporal craniotomy, which offered a greater ability to stimulate subdivisions of the trigeminal nerve, without muscular (V3) side effects. Two of the seven overall patients did not respond well to the trial and were not implanted. Five patients reported pain relief with up to 24-month follow-up. Several of the sphenopalatine ganglion stimulation patients had pain relief without any paresthesias. There were no electrode migrations or post-surgical complications. CONCLUSIONS: Refractory facial pain may respond positively to ganglionic forms of stimulation. It appears safe and durable to implant electrodes in the pterygopalatine fossa via a lateral transpterygoid approach. Also, implantation of an electrode grid overlying Meckel's cave appears to be a feasible alternative to the Hartel approach. Further investigation is needed to evaluate the usefulness of these approaches for various facial pain conditions.

Motor cortex stimulation for chronic pain.

Motor cortex stimulation produces significant relief of symptoms in many forms of refractory chronic pain disorders.

Chasing map plasticity in neuropathic pain.

OBJECTIVE: Recently, somatosensory cortex stimulation has been proposed as a possible treatment for neuropathic deafferentation pain, based on a simple 4-step concept: (1) pain is associated with increased activity in the somatosensory cortex, (2) allodynia-evoked blood-oxygen-level dependence functional magnetic resonance imaging (fMRI) activation depicts the area involved in the pain, (3) if fMRI-guided, neuronavigation-based transcranial magnetic stimulation can transiently suppress the pain, then (4) an extradural electrode can be implanted targeting the same area. CASE DESCRIPTION: A patient who was successfully treated with this approach for over 6 years for trigeminal anesthesia dolorosa associated with a subjectively malpositioned eye after multiple recurrent facial skin tumor removals developed new pain after more extensive surgery. Reprogramming the implanted electrode was unsuccessful. The presence of the electrode yielded too many artifacts on a renewed fMRI, and therefore a positron emission tomography (PET) scan was performed under evoked allodynia. Fusing the previous fMRI with the new PET images depicted 2 novel targets for stimulation, 1 anterior and 1 posterior of the previous target and beyond the spatial configuration of the implant. After the addition of 2 new electrodes, the pain could again be controlled in a placebo-controlled way, but only when the 2 electrodes were activated. CONCLUSIONS: Combining fMRI and PET scanning can potentially demonstrate continuing map plasticity under progressive somatosensory deafferentation. The functional imaging data can be used as target for pathophysiology-based somatosensory cortex stimulation.