perimented with the use of intramuscular injection of camphor to induce seizures in 1934. Italian neurologist Ugo Carletti was the first to use electricity applied cranially to induce seizures.
By 1940, electroconvulsive therapy( ECT) had become an accepted treatment for major depression and schizophrenia. However, movies like the 1975 film One Flew Over the Cuckoo’ s Nest, that portrayed ECT as a tool of punishment and memory erasure, gave it a bad rap. The more recent use of anesthesia and muscle relaxants during ECT has made it much more acceptable, and it’ s used in the management of treatment-resistant depression, bipolar disorder and schizophrenia, especially when rapid therapeutic response is vital.
During the past several decades, the science of neuromodulation techniques and devices has blossomed into an important part of medical care. Every major organ system has benefited from neuromodulating devices, examples being pacemakers, cochlear implants, stimulators to control various organs such as the stomach and urinary blader, in addition to a plethora of gadgets for numerous neurological disorders. These gadgets achieve stimulus delivery through implanted electrodes and hence are considered invasive. The most well-known example of invasive brain modulation is deep brain stimulation( DBS) to influence activity of the thalamus, basal ganglia, substantia nigra, the most common targets. Initially approved by the FDA in 1997 for treatment of essential tremor and severe tremor in Parkinson’ s disease, the indication for DBS has expanded to include conditions like drug-resistant epilepsy and certain psychiatric disorders. The introduction of closed loop DBS has led to more functional adaptive neurostimulation. Implanted vagus nerve and spinal cord stimulators are other examples of invasive stimulators. The implanted hypoglossal nerve stimulator for obstructive sleep apnea and sacral nerve stimulator for bladder / bowel incontinence are also considered invasive neurostimulators. Non-invasive neuromodulators include gadgets that apply various forms of electrical( transcranial electric stimulation: TNS) and electromagnetic( transcranial magnetic stimulation: TMS) pulses to the scalp, and transcutaneous trigeminal, vagus and peripheral nerve stimulators. Invasive neuromodulation gadgets have established their role in management of conditions like Parkinson’ s disease tremors and various movement disorders, drug-resistant epilepsy and several psychiatric disorders. Use of spinal cord stimulators for pain control has increased in utilization after painful diabetic neuropathy became an approved indication.
Vagus nerve stimulation( VNS) has become the center of attraction in recent years. It involves placing an electrode around the cervical branch of the vagus nerve which is thus connected to a sub clavicular pulse generator. It delivers electrical stimuli to the nucleus of the tractus solitarius, which in turn can modulate release of serotonin from the dorsal raphe nucleus and norepinephrine through the locus ceruleus. This is a less invasive procedure than deep brain stimulation. VNS has been found to be effective in patients with drug resistant epilepsy, improving seizure control and quality of life. It has also been found to be useful in treatment-resistant depression. Recent studies are looking at the effect of VNS in Parkinson’ s disease. VNS combined with targeted physical therapy is being increasingly used after stroke to increase neuroplasticity( synaptogenesis and functional reorganization).
The use of non-invasive neuromodulation is becoming a major player in the management of many disorders thanks to the ease of usage and the feverish pace at which such gadgets are coming into the market. TENS are available without prescription and are rapidly becoming a household tool for pain control. The FDA has already cleared six noninvasive neuromodulation devices for headache management. These include external trigeminal neurostimulators as well as gadgets for single pulse transcranial magnetic stimulation( TMS) and noninvasive vagus nerve stimulation with a hand-held device. Non-invasive techniques such as transcranial direct current stimulation( tDCS) and transcranial magnetic stimulation( TMS) are also being evaluated for hastening recovery of speech in patients with aphasia resulting from stroke.
The future of neuromodulation technology is promising, with innovations arriving at warp speed. Let me conclude with a quote from Tom Andriola, Chief Digital Officer at UC Irvine:“ Technology is the enabler, but clinicians and caregivers will always be in the lead.”
References:
1
Kumar K., Rizvi S. Historical and present state of neuromodulation in chronic pain. Curr Pain Headache Rep. 2014 18( 1): 387
2
Xia J et al. Advances in neuromodulation for aphasia rehabilitation. Med Sci Monit 2025 31: e947213
3
Lerman I et al. Next generation bioelectronic medicine: making the case for non-invasive closed-loop autonomic neuromodulation. Bioelectronic Medicine. 2025 11:1
Dr. Iyer practices at the Neurodiagnostic Center of Louisville and is a retired professor of neurology at the University of Louisville School of Medicine.
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