症例
Effective high-frequency spinal cord stimulation for neurosarcoidosis-induced lower back and limb pain: a case report
2022 年 29 巻 4 号 p. 60-63
詳細
2022 年 29 巻 4 号 p. 60-63
Sarcoidosis is a multi-organ disease of unknown cause, resulting in damage to diverse organs. We report a case in which sub-perception high-frequency spinal cord stimulation (SCS) was remarkably effective in improving lumbar pain due to neurosarcoidosis lesions in the spinal cord, which had not resolved with conventional conservative treatment. A man in his 70s developed sudden left lower back and lower limb pain, muscle weakness, and spasticity. Steroid therapy was effective in temporarily relieving symptoms, but medication and nerve blocks were not effective in treating severe pain relapse. Therefore, SCS was performed as the next step in pain relief. High-frequency SCS was particularly effective in alleviating symptoms, and activities of daily living significantly improved.
The annual incidence of sarcoidosis is 10–20 per 100,000, and it develops in any part of the body. Neurosarcoidosis accounts for about 10％ of cases, and spinal cord lesions are rare1). Because symptoms depend on the lesion site, disease-specific findings are few and diagnosing and treating the disease is often difficult. We report a case in which spinal cord stimulation (SCS) was remarkably effective in improving intractable low back and leg pain due to neurosarcoidosis, which had not been relieved by conventional conservative treatment. This study was approved by the Saitama Medical Center Bioethics Committee (reception number 21–11). Written informed consent to publish this case report was obtained from the patient's family.
A man in his 70s complained of intractable pain in the left leg. Comorbidities included hypertension, chronic renal failure, and diabetes.
Eight years before, the patient had developed weakness in the left lower limb and pain and numbness on the outside of the left thigh. A few days later, his symptoms worsened, making it difficult to walk. He visited A University Hospital. Neurological findings included spasticity of both lower limbs, weakness of the left iliopsoas muscle, sensory impairment below the left T12 level, and enhanced tendon reflexes in both upper and lower limbs. The pathological reflex was negative, and no abnormalities were found in blood or cerebrospinal fluid. Magnetic resonance imaging (MRI) from the head to the lumbar region was normal. No disorders of the lower motor neurons were observed on the electromyogram. No definitive diagnosis was made and follow-up was performed. Five years before, positron emission tomography conducted a third time showed positive findings in the anterior mediastinal lymph nodes. Biopsy revealed noncaseous necrotic epithelial granulomas, which were diagnosed as sarcoidosis. Simultaneously, thoracic spine MRI showed mild spinal cord deformity at the T6/7 level. The symptoms were possibly caused by spinal cord sarcoidosis (Figure 1).
Plain thoracic spine magnetic resonance imaging, showing T6/7 level spinal cord deformity
One year before he visited our department, the pain gradually recurred, and lumbar MRI showed mild spinal canal stenosis (L3/4/5 level). He visited A University Hospital Pain Clinic. Limaprost alfadex, mecobalamin, and acetaminophen 1.2 g/day were ineffective in treating the pain. Mirogabalin 5 mg/day provided some pain relief; the dose was staggered with an increasing dose of 10 mg/day. Continued treatment with drugs was difficult. The patient underwent trigger point injections and lumbar epidural block several times, but his symptoms did not improve and treatment was interrupted.
At his first visit to our department, the patient was in a wheelchair. Symptoms included spontaneous hyperesthesia of the left lower extremity from the lumbar spine of the left hip. The Numerical Rating Scale (NRS) was 5/10 in sitting position and 8/10 in body movement. He couldn't walk because of the severe pain when he moved his lower limbs. This pain made him sleepless. Epidural block was performed twice at our department, but no analgesic effect was achieved. The patient did not wish to receive oral treatment. Owing to wide area of pain from the left hip to the lower limbs and difficulty of conservative treatment, we planned a percutaneous SCS study.
The surgical procedure was performed under local anesthesia in the prone position. Epidural access was obtained at the L1/2 interlaminar space, and applying stimulation at a frequency of 50 Hz and a pulse width of 600 µm when the tip reached the lower T7 end. Paresthesia occurred over the entire pain area of the left lumbar and lower extremities, and the irritation was not unpleasant for the patient. Therefore, we switched to a surgical trial. The second lead was placed on the left side of the first lead and the tip was positioned at the lower T8 end (Figure 2). The operation time was 93 minutes. On the same day, 3.5 mA, 600 Hz, and 90 µs sub-perception high-frequency SCS was initiated. Although the numbness remained, it provided pain relief and his spasticity improved. He was able to stand and walk using a cane the next day onward. During the 1-week test period, the same sub-perception high-frequency stimulation, differential target multiplexed stimulation (DTM, Medtronic), and tonic stimulation (5–100 Hz) were sequentially evaluated. NRS decreased from 8/10 at the first visit to 2/10 at 600 Hz, 3/10 on DTM stimulation, and 5/10 on tonic stimulation. In the sitting position, the pain nearly disappeared, although some discomfort persisted in his lower back. One week later, a stimulus generator was implanted, and the patient was discharged with a 600 Hz high-frequency stimulus, which had the highest pain-relieving effect. He did not need regular analgesics. He was monitored by the Department of Neurology, but no signs of sarcoidosis were found. Three months after the operation, his pain level continued to be halved without analgesics, and his activities of daily living improved, including being able to walk the dog.
Fluoroscopy image of the spinal cord stimulator
Two epidural leads in the epidural space were positioned at T7–T10.
SCS therapy is a pain-relieving treatment used for chronic intractable pain. Conventionally, a pain-relieving effect is achieved by matching a tonic stimulation having a relatively low frequency of 5–50 Hz to the pain site. However, in recent years, sub-perception stimulation methods (high-frequency or burst stimulation) that do not cause irritation have been developed, and their effectiveness has been reported in patients who cannot achieve sufficient pain relief with tonic stimulation2). SCS may also be less effective for lower back pain, but high-frequency SCS is considerably more effective in reducing lower back pain and leg pain than conventional stimulation3).
In our case, identifying the cause of the pain at onset was difficult. However, a biopsy 3 years later strongly suggested neurosarcoidosis. The effectiveness of SCS is generally considered low for central lesions such as in this case. The British Pain Society recommends an intermediate SCS level for spinal cord injury (SCI)4). However, the usefulness of SCS therapy for SCI has been reported5,6).
Thus, SCS may be worth trying if long-term central intractable pain is difficult to relieve using conventional treatments. There are various theories about the effectiveness of high-frequency SCS, such as the involvement of spinal cord glial cells, but the mechanism of action has not yet been elucidated7). One advantage of high-frequency SCS is that the tip position of the lead only needs to be placed at T8, and the stimulus does not need to be closely matched to the pain site. Therefore, the operation time is shortened. Thus, in this case as well, treatment was switched to surgery, but the surgery time was short.
Recently, although studies regarding ultra-high frequency stimulation using new devices have been reported3,7), the usefulness of high frequency stimulation (300–1,200 Hz) has also been reported8). For patients who no longer respond to tonic stimulation, simply increasing the frequency may produce new effects. The disadvantage of high frequency stimulation is that it consumes power to a large extent and needs to be charged frequently.
The use of SCS for improving post-SCI nerve function has been studied in the past, but no consensus has been obtained9). However, it may improve spasticity in patients with SCI10). In our case, activities of daily living significantly improved in a short period after SCS. Thus, high-frequency SCS may have had a positive effect not only on pain but also on motor function.
The limitation of this report is that peripheral neuropathy cannot be completely ruled out because it has not been histologically diagnosed as neuro (spinal) sarcoidosis. No preclinical or clinical studies have been conducted on the effectiveness of sub-perception SCS for SCI.
High-frequency SCS therapy may be effective for intractable lower back and lower limb pain caused by neurosarcoidosis.
