Chronic subdural cortical stimulation for phantom limb pain: report of a series of two cases

Research Trends and Hotspots of Neuromodulation in Neuropathic Pain: A Bibliometric Analysis

BACKGROUND

Neuropathic pain (NeuP), the result of a lesion or disease of the somatosensory nervous system, is tricky to cure clinically. Mounting researches reveal that neuromodulation can safely and effectively ameliorate NeuP. The number of publications associated with neuromodulation and NeuP increases with time. However, bibliometric analysis on the field is rare. The present study aims to analyze trends and topics in neuromodulation and NeuP research by using a bibliometric method.

METHODS

This study systematically collected the relevant publications on the Science Citation Index Expanded of Web of Science from January 1994 to January 17, 2023. CiteSpace software was used to draw and analyze corresponding visualization maps.

RESULTS

A total of 1404 publications were ultimately obtained under our specified inclusion criteria. The analysis showed that the focus of research on neuromodulation and NeuP had been developing steadily in recent years, with papers published in 58 countries/regions and 411 academic journals. The Journal of Neuromodulation and the author J.P. Lefaucheur published the most papers. The papers published in Harvard University and the United States contributed significantly. The cited keywords show that motor cortex stimulation, spinal cord stimulation, electrical stimulation, transcranial magnetic stimulation, and mechanism are the research hotspots in the field.

CONCLUSIONS

The bibliometric analysis showed that the number of publications on neuromodulation and NeuP are increasing rapidly, especially in the past 5 years. "Motor cortex stimulation," "electrical stimulation," "spinal cord stimulation," "transcranial magnetic stimulation" and "mechanism" catch the most attention among researchers in this field.

Management of Phantom Limb Pain through Thalamotomy of the Centro-Median Nucleus

Background: Phantom limb syndrome is defined as the perception of intense pain or other sensations that are secondary to a neural lesion in a limb that does not exist. It can be treated using pharmacological and surgical interventions. Most medications are prescribed to improve patients’ lives; however, the response rate is low. In this case report, we present a case of phantom limb syndrome in a 42-year-old female with a history of transradial amputation of the left thoracic limb due to an accidental compression one year before. The patient underwent placement of a deep brain stimulator at the ventral posteromedial nucleus (VPM) on the right side and removal secondary to loss of battery. The patient continued to have a burning pain throughout the limb with a sensation of still having the limb, which was subsequently diagnosed as phantom limb syndrome. After a thorough discussion with the patient, a right stereotactic centro-median thalamotomy was offered. An immediate response was reported with a reduction in pain severity on the visual analogue scale (VAS) from a value of 9–10 preoperative to a value of 2 postoperative, with no postoperative complications. Although phantom limb pain is one of the most difficult to treat conditions, centro-median thalamotomy may provide an effective stereotactic treatment procedure with adequate outcomes.

Typical somatomotor physiology of the hand is preserved in a patient with an amputated arm: An ECoG case study

Electrophysiological signals in the human motor system may change in different ways after deafferentation, with some studies emphasizing reorganization while others propose retained physiology. Understanding whether motor electrophysiology is retained over longer periods of time can be invaluable for patients with paralysis (e.g. ALS or brainstem stroke) when signals from sensorimotor areas may be used for communication or control over neural prosthetic devices. In addition, a maintained electrophysiology can potentially benefit the treatment of phantom limb pains through prolonged use of these signals in a brain-machine interface (BCI). Here, we were presented with the unique opportunity to investigate the physiology of the sensorimotor cortex in a patient with an amputated arm using electrocorticographic (ECoG) measurements. While implanted with an ECoG grid for clinical evaluation of electrical stimulation for phantom limb pain, the patient performed attempted finger movements with the contralateral (lost) hand and executed finger movements with the ipsilateral (healthy) hand. The electrophysiology of the sensorimotor cortex contralateral to the amputated hand remained very similar to that of hand movement in healthy people, with a spatially focused increase of high-frequency band (65-175 Hz; HFB) power over the hand region and a distributed decrease in low-frequency band (15-28 Hz; LFB) power. The representation of the three different fingers (thumb, index and little) remained intact and HFB patterns could be decoded using support vector learning at single-trial classification accuracies of >90%, based on the first 1-3 s of the HFB response. These results indicate that hand representations are largely retained in the motor cortex. The intact physiological response of the amputated hand, the high distinguishability of the fingers and fast temporal peak are encouraging for neural prosthetic devices that target the sensorimotor cortex.

Pre-motor versus motor cerebral cortex neuromodulation for chronic neuropathic pain

Electrical stimulation of the cerebral cortex (ESCC) has been used to treat intractable neuropathic pain for nearly two decades, however, no standardized approach for this technique has been developed. In order to optimize targeting and validate the effect of ESCC before placing the permanent grid, we introduced initial assessment with trial stimulation, using a temporary grid of subdural electrodes. In this retrospective study we evaluate the role of electrode location on cerebral cortex in control of neuropathic pain and the role of trial stimulation in target-optimization for ESCC. Location of the temporary grid electrodes and location of permanent electrodes were evaluated in correlation with the long-term efficacy of ESCC. The results of this study demonstrate that the long-term effect of subdural pre-motor cortex stimulation is at least the same or higher compare to effect of subdural motor or combined pre-motor and motor cortex stimulation. These results also demonstrate that the initial trial stimulation helps to optimize permanent electrode positions in relation to the optimal functional target that is critical in cases when brain shift is expected. Proposed methodology and novel results open a new direction for development of neuromodulation techniques to control chronic neuropathic pain.