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High Frequency (HF10) Spinal Cord Stimulation for Chronic Neuropathic Pain
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.302470
Keywords: Spinal Cord Stimulation; Failed Back Surgery Syndrome; High frequency; Neuropathic pain; Percutaneous
Spinal cord stimulation is increasingly being used in the multidisciplinary management of patients with chronic neuropathic pain typically from a failed back surgery syndrome. High frequency stimulation with 10 KHz frequency and 30 microseconds pulse width has been shown to be superior to the conventional low frequency SCS in a randomised controlled trial and the 24 month outcome data showed sustained pain relief. HF10 SCS is paraesthesia independent and involves anatomical placement of the electrodes without the need to do any paraesthesia mapping.[1],[2] Newer paradigms and waveforms for subperception SCS have also been introduced in the low frequency SCS with promising results in both low back and leg pain.[3],[4] Patients selected for SCS typically have chronic neuropathic pain above 5/10 on the numerical rating scale, not responding to anti neuropathic pain medication, understand pain management strategies, does not have any psychological issues or medical co-morbidities, and be willing and able to use the device and attend regular follow-ups.
The procedure was performed under intravenous sedation and local anaesthesia. The patient was placed prone on the Montreal mattress. Skin entry point was marked using intra-op C-ARM imaging. The skin was cleaned with antiseptic and draped. Sterile cover was placed over the C-ARM. LA (a mixture of 1% lignocaine with adrenaline and 0.25% Bupivacine) was infiltrated. Left paraspinal incision was made down to the fascia and suprafacial pocket was created. 14g Touhy needle was inserted and placed under C-ARM guidance over the spinolaminar junction of L1. The needle was then walked off the bone and into the epidural space using the loss of resistance to saline technique. It is vital not to advance the needle too much to avoid dural puncture. The electrode is then inserted into the midline posterior epidural space under C-ARM guidance with both AP and lateral views to confirm the lead position. The first lead is inserted till the top of T8 vertebra. The second Touhy needle is inserted at the same or a level below and the second electrode is inserted till top T9 with staggering of the contacts across the T9-10 disc space which is generally the sweet spot. Once the electrode positions are confirmed on C-ARM, stab incision are made in the fascia adjacent to the needles to accommodate the anchors. The needle and stylette is withdrawn under C-ARM guidance and anchor inserted over the lead. Part of the anchor is slid into the fascia and the locking screw tightened and anchor secured to the fascia with non-absorbable suture such as silk. A supragluteal incision is then made and the leads tunnelled using the Touhy needle. The leads are then connected to the extension wires, which are then then tunnelled out using the Touhy needle. Purse string stitch is placed before removing the Touhy needle at the exit site to and the stitch tightened after removing the Touhy needle. It is important to ensure that the exit site is below the level of gluteal incision to allow drainage of any postop collection. Lead impedance is checked and if satisfactory strain relief loops are placed in the pocket in the paraspinal incision as well as in the gluteal incision. Betadine lavage is given and haemostasis is ensured before wound closure with Vicryl and skin clips. Video Link: https://youtu.be/_La2JELa0Gw QR code:
Video timeline with audio transcript: 0.15-0.33: Clinical features. Thoracic high frequency spinal cord stimulator involves anatomical placement of the electrodes in the midline posterior epidural space. This video demonstrates the percutaneous implant technique for a trial. A 51 year old patient was referred with chronic back and leg pain following successful spinal decompression and fusion operation at L5/S1. The screws and rods were later explanted without any pain relief 0.34-0.49: Table and patient position. It is important to plan the position of the operating table to ensure that the base of the table does not hinder the CARM. The base of the table should be towards the foot end to allow cranio-caudal angulation of the CARM as shown here. 0.50-1.28: Marking the skin entry level using C-ARM, LA infiltration, Paraspinal incision and creation of pouch The level is marked using C-ARM. The skin entry point is usually at 3 O’clock (or 9 O’clock if entering from right side) of the pedicle a level below the epidural entry usually the T12/L1 or L1/L2 space 1.29-1.54: Epidural entry. Using continuous fluoroscopy the Touhy needle is inserted and the spinolaminar junction is hit as shown. The needle is then walked into the epidural space using the loss of resistance technique. 1.55-2.46: Insertion of top lead. The percutaneous lead is then inserted and steered in the midline posterior epidural space till top of T8. Lateral view is done to ensure that the lead is in the posterior epidural space. 2.47-3.14: Epidural entry of the second needle. The second Tuohy needle is inserted either at the same level or a level below. 3.17-4.13: Insertion of the bottom lead. The percutaneous lead is inserted till top T9 with staggering of the leads. It is important to confirm the lead location on AP and lateral screening 4.13-6.43: Removal of needle, stylette and anchoring the leads. The needle and stylette is removed under C-ARM guidance ensuring the lead doesn’t migrate. The anchor is placed on the lead and the screw tightened. The anchor is fixed to the fascia with silk stitch. 6.44-7.41: Supragluteal incision and tunnelling the leads. A supra gluteal incision is made and the leads tunnelled using the Touhy needle. Strain relief loops are placed in the paraspinal pouch. 7.42-9.39: Tunnelling the extension wires, purse string stitch, Connecting the leads and extensions, Lead impedance and auto alignment check and closure. Touhy needle is inserted from the exit site to the supragluteal incision and the extension wires tunnelled. They are connected to the leads and secured. Lead impedance and autoaligment are checked and if satisfactory the wound is closed after haemostasis and Betadine wash. 9.40-9.51: Outcome, Conclusions, References. This patient had excellent pain relief following the trial with the VAS score dropping right down to 2 from 7/10.
This patient had a positive trial with the significant reduction (90%) in both low back pain and leg pain. The back pain reduced from 7.5 to 2.9 on the visual analogue scale (VAS) and leg pain from 6.8 to 2.5. Two weeks after the successful trial the patient underwent implantation of the implantable pulse generator (IPG). Pearls and pitfalls
Thoracic high frequency spinal cord stimulation is highly successful in management of chronic pain typically from failed back surgery syndrome and has the ability to manage both back and leg pain. The SENZA-RCT has demonstrated level 1 evidence supporting the use of HF10 SCS in these complex pain patients[1]. It is important to assess and select the patients in a multidisciplinary setting to maximise the outcome. Meticulous technique and attention to details are important points to remember during the surgical procedure.
Thoracic HF10 SCS is a vital tool in the management of chronic neuropathic pain. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.
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