Neuromodulation in Postherpetic Neuralgia: Case Reports and Review of the Literature.

Objective: Postherpetic neuralgia (PHN) is common in the United States. Current treatment options for PHN are fairly limited. Spinal cord stimulation (SCS) and peripheral nerve stimulation (PNS) are considered mostly experimental and still rarely performed in patients with PHN. Design: Two case reports and a review of the literature. Setting: Tertiary academic medical center. Methods: 1) Pubmed, Ovid, and EBMR databases were searched for all reports that had the following key words: postherpetic neuralgia, spinal cord stimulation, and peripheral nerve stimulation. 2) A retrospective chart review was performed for all the patients that underwent PNS for PHN at Mayo Clinic Florida (MCF). Results: There were 20 original reports that described 309 patients with PHN who were treated with SCS. Sixteen reports had a permanent implantation of SCS, with a total of 255 patients, out of which 120 had long-term pain relief. There were six reports of subcutaneous PNS for PHN (in a thoracic area). Four reports provided data on success rates where all five patients received complete pain relief. In our practice, two patients underwent subcutaneous PNS for PHN (in the thoracic area) with good pain relief for 10 months and 2.5 years, respectively. Conclusions: Based on our review of the literature and the two cases at MCF, subcutaneous PNS seems to be a promising intervention in the treatment of PHN.

Needle placement for piriformis injection using 3-D imaging.

Piriformis syndrome is a pain syndrome originating in the buttock and is attributed to 6% - 8% of patients referred for the treatment of back and leg pain. The treatment for piriformis syndrome using fluoroscopy, computed tomography (CT), electromyography (EMG), and ultrasound (US) has become standard practice. The treatment of Piriformis Syndrome has evolved to include fluoroscopy and EMG with CT guidance. We present a case study of 5 successful piriformis injections using 3-D computer-assisted electromagnet needle tracking coupled with ultrasound. A 6-degree of freedom electromagnetic position tracker was attached to the ultrasound probe that allowed the system to detect the position and orientation of the probe in the magnetic field. The tracked ultrasound probe was used to find the posterior superior iliac spine. Subsequently, 3 points were captured to register the ultrasound image with the CT or magnetic resonance image scan. Moreover, after the registration was obtained, the navigation system visualized the tracked needle relative to the CT scan in real-time using 2 orthogonal multi-planar reconstructions centered at the tracked needle tip. Conversely, a recent study revealed that fluoroscopically guided injections had 30% accuracy compared to ultrasound guided injections, which tripled the accuracy percentage. This novel technique exhibited an accurate needle guidance injection precision of 98% while advancing to the piriformis muscle and avoiding the sciatic nerve. The mean (± SD) procedure time was 19.08 (± 4.9) minutes. This technique allows for electromagnetic instrument tip tracking with real-time 3-D guidance to the selected target. As with any new technique, a learning curve is expected; however, this technique could offer an alternative, minimizing radiation exposure.

Spinal cord stimulator--trial lead migration study.

OBJECTIVES: Investigate whether percutaneous spinal cord stimulator (SCS) leads migrate significantly during a 3-day trial, and determine whether the skin anchoring method influences lead migration. MATERIAL AND METHODS: Twenty patients were prospectively enrolled. Ten leads were anchored with suture and tape and 10 were anchored with tape only. A standardized X-ray protocol of lead position was obtained immediately following lead placement and upon completion of the trial. RESULTS: Using a standardized method, SCS leads were measured and movement was calculated. The average movement for leads anchored with tape only was 8.72 mm (SD=5.77), inferiorly; while movement for leads anchored with suture and tape was 24.49 mm (SD=11.3), inferiorly. A t-test revealed a significant difference between the groups (t=3.9, P=0.001). CONCLUSIONS: Percutaneous SCS trial electrodes migrate significantly, inferiorly, during a 3-day trial. Anchoring the trial electrodes to the skin with a suture and tape results in significantly greater inferior migration when compared with anchoring the lead with tape only.