Non-Invasive Brain Stimulation in Management of Failed Back Syndrome: A Case Report

Introduction

Low back pain is the most common cause of functional disability and absence from work worldwide.¹ It has a 12-month prevalence of 32.5% - 73.53% in Nigeria.² Over 70% of patients with back pain can be pain free within months with a recurrence rate of about 25%.³ Chronic low back pain (CLBP) having an annual prevalence of 15%-45% is defined as pain lasting two months and above⁴ which has both physical and emotional burden on individuals suffering from it. The standard treatment for chronic low back pain involves use of analgesics (NSAIDs and opioids), physical therapy and surgical intervention. Advances in treatment of chronic low back pain have included non-invasive brain stimulation as a paradigm of treatment of chronic low back pain and chronic pain in general. The understanding about non-invasive brain stimulation (NIBS) techniques such as transcranial direct current stimulation (tDCS) and repetitive transcranial magnetic stimulation (rTMS) has increased on a wide range of different conditions in the last 20 years.^5,6

Transcranial direct current stimulation is a neuromodulatory technique that involves transmission of low intensity direct current to specific area of the brain facilitating or inhibiting spontaneous neuronal activities. Studies have established the effectiveness of transcranial direct current stimulation (tDCS) on pain symptoms in patients with central pain because of traumatic spinal cord injury.⁷ The purpose of this study was to report the effectiveness of NIBS on failed back syndrome.

Case Presentation

A 50 year old woman presented with a complaint of pain in her lower back and heaviness of left lower limb (Lt LL). She first experienced back pain about 10 years ago which has been managed conservatively using pain medications. As time passed, her back pain worsened and she started having heaviness and occasional numbness of her left lower limb. She revisited hospital and was asked to do an MRI after which she was counseled for surgery. She underwent an endoscopic L₄/L₅ repair surgery. However, symptoms persisted after a month and the patient also had pain along the posterior part of the limb. Subsequently she was referred to physiotherapy for rehabilitation.

On observation, patient was noticed walking into the clinic unaided with slow antalgic gait, sat with difficulty and obvious painful distress. She was acyanosed, anicteric, afebrile to touch and in no obvious respiratory distress. Patient had a slightly stooped posture. On examination of back, patient had decreased lumbar lordosis with spasm of para spinal muscles. All spinal movements were painful.

The procedure of treatment was explained to the patient and her consent was sought to report the outcome of her treatment.

Interventions

Patient was treated with non-invasive brain stimulation followed by routine back exercises and LLs strengthening. The procedure was carried out by a physiotherapist certified in brain stimulation and all the five sessions of NIBS were carried out by the same investigator. Patient was required to assume a supine lying position on the couch resting her head on a pillow. Direct current was transferred using sterile acupuncture needles inserted in a clockwise direction at an angle of 45° at D20 (motor representation of lumbar muscles), motor and somatosensory areas of the brain and delivered using a battery driven handheld acupuncture pen stimulator (shastri stimulator) with a maximum output power of 5, giving about 10 stimulations at a time at each area mentioned above. Each NIBS session lasted 30 mins; patient had one session daily with a total of five sessions. Patient received additional 12 sessions (at 3 sessions per week) of core stability and strengthening exercises after NIBS sessions.

Outcome Assessment

This study intended to report the effectiveness of NIBS in addition to strengthening exercises in treating failed back syndrome. The pain level of the patient was assessed subjectively using the numerical pain rating scale (NPRS). Patient was required to rate her pain on a scale of 1-10 (1- minimal pain ever felt and 10- worst pain ever). Muscle power of the affected lower limb (left) was assessed using the gross muscle power (GMP). The GMP has a score of 0-5 (0- no movement, 1- flicker of movement, 2- movement in gravity eliminated position, 3- movement against gravity, 4- movement against gravity with minimal resistance, and 5- movement against gravity with maximum resistance). Other outcome measures such as straight leg raise (SLR), vertical oscillatory pressure (VOP), transverse oscillatory pressure (TOP) was used to determine the level of spinal affectation. Patient vitals were taken pre-treatment which included blood pressure (130/90 mmHg) (she is a known hypertensive and has been on medication for about five years), pulse rate (89 bpm) and SPO₂ (97%). However, there was no change in vitals of patient post treatment.

Table 1 shows the NPRS score through the five sessions of NIBS that was administered. The pre-treatment NPRS score was 8/10 (that is pain at assessment). The NPRS score improved to 7/10, 6/10, 5/10, 4/10 and 3/10 at end of 1^st, 2^nd, 3^rd, 4^th, and 5^th sessions respectively. Each measure was taken and recorded five minutes after NIBS treatment so as to enable relaxation of the patient.

Table 2 shows the pre-and post-treatment score at the end of 12 sessions of exercise therapy. The muscle power of Lt LL improved from 3/5 to 4/5 on GMP scale. The SLR, TOP and VOP which were positive pre-treatment became negative post-treatment.

All outcomes were measured before treatment and at the end of treatment sessions and recorded on a Microsoft Excel sheet. Changes in outcome were calculated by subtracting post-treatment values from pre-treatment scores.

Table 2 shows the pre-and post-treatment scores of outcome parameters measured. NPRS improved from a score of 8 to a score of 3. GMP of the affected lower limb (left LL) improved from a score of 3 to a score of 4. SLR, VOP and TOP which were initially positive became negative.

Discussion

This study aimed to report the effectiveness of NIBS in addition to strengthening exercises in the management of failed back syndrome. There was a significant improvement in NPRS of patient after NIBS which was recorded before and after the treatment. This case report has shown how NIBS was used to manage a patient with a long history of low back pain that led to a back surgery with little improvement. However, after a brief session of NIBS, the patient felt better and the symptoms improved. It can be assumed that patient would have recovered without the requirement of surgery, if the NIBS sessions were started earlier and might have saved the patient cost of the surgery and other healthcare cost due to back pain. Though strengthening exercises were incorporated in the management of this patient, the significant improvement recorded in the patient’s LL muscle strength might not only have resulted directly from the exercises, but also from the analgesia effect of the NIBS that allowed the patient to perform the exercises painlessly.

The process of pain mediation in the brain involves the anterior cingulate cortex which comprises the medial pain pathway with the medial thalamus, anterior insula and posterior parietal cortex. Along with the primary and secondary somatosensory cortices (S1 and S2 respectively),⁸ the anterior cingulate cortex is associated with “second pain sensation” and thus chronic pain.^9,10 Pain is a subjective assessment and pain threshold varies from individual to individual. In this report, the patient presented with severe chronic pain with a NPRS score of 8 associated with compensatory postural deformities. However, after five consecutive sessions of NIBS, a significant improvement was reported. Pain reduction was gradual through the NIBS sessions as reported by the patient with an NPRS score of 3 reported in the last session.

This is in line with the findings of Antal et al.,¹¹ who reported that application of anodal tDCS over the hand area in M1 for five consecutive days showed improvement in visual analog scale (VAS) as compared to sham tDCS. Duration of NIBS application was similar to our study, but with a larger sample size.

The study also reported that patient had significant improvement in radiculopathy and muscle strength of the Lt LL after 12 sessions of strengthening exercises of both lumbosacral muscles and the Lt LL muscle groups. The muscle power of the affected LL improved from a score of 3/5 to 4/5 on the GMP scale. SLR, TOP, and VOP which were initially positive prior to treatment became negative. The improvement in the strength of the back and LLs was due to reduction in pain following NIBS which enabled the patients to carry out exercises effectively.

This is in line with study conducted by Cardenas-Rojas et al.¹² The study by Cardenas-Rojas and co was a meta- analysis which showed significant moderate to large effects of NIBS and exercise combination in treatment of chronic pain.

The outcome of this study suggests that non-invasive brain stimulation and strengthening exercises are effective in treatment of chronic low back pain and failed back surgery syndrome.

Recommendation

Non-invasive brain stimulation is poorly utilized in middle and low income countries. This case report covered only a single patient. More research with larger sample size should be done in this field to properly establish the effectiveness of NIBS in treating chronic low back pain.