Application of Transcranial Magnetic Stimulation in Consciousness Disorders

Transcranial Magnetic Stimulation,TMS

 

Disorder of consciousness refers to the abnormality of the human body’s perception of itself or the surrounding environment. It is relatively common and usually has an acute onset, mostly caused by diseases of the central nervous system. Typical symptoms include excessively prolonged sleep, no spontaneous eye-opening, and the disappearance of voluntary activities. Medications are required, some patients require surgery, and the prognosis varies with the severity of the disease.

At present, the diagnosis and treatment of disturbance of consciousness caused by severe traumatic brain injury are very difficult.

 

The clinical diagnostic classification of disturbance of consciousness mainly includes vegetative state/unresponsive arousal syndrome and Minimally Conscious State (MCS).

There is a lack of effective diagnostic methods and treatment methods in clinics, so accurate prognostic results cannot be made, and the formulation of treatment strategies is also affected, which seriously affects the recovery of patients.

The existing clinical evaluation methods mainly rely on the clinical behavior scores of patients, and the misdiagnosis rate is as high as 40%.

 

A brief introduction to the current status of diagnosis and treatment of consciousness disorders

Disorders of consciousness are mainly manifested in three clinical forms: coma, minimally conscious state, and vegetative state. Generally speaking, conscious content behavior depends on the integrity of the higher neural activity network and subcortical connections in the functional cortex of the brain, while arousal depends on the integrity of the upward activation system of the brainstem reticular structure. The therapeutic effect of TMS on disturbance of consciousness depends on the stimulation site, stimulation frequency, stimulation intensity, etc. How TMS can effectively act on the functional cortex and ascending reticular activation system of the brain is the content that scholars should study.

Common causes of patients with impaired consciousness include craniocerebral diseases, endocrine and metabolic diseases, cardiovascular diseases, etc., which are caused by various types of disorders of consciousness. In clinical practice, although there are many treatment methods for patients with disorders of consciousness, including drugs, hyperbaric oxygen, and rehabilitation therapy, the therapeutic effect is not significant.

Electrical stimulation techniques, such as spinal cord stimulation and deep brain stimulation, have achieved significant results in the treatment of disorders of consciousness. However, these treatments also have disadvantages: they are invasive and expensive.

In recent years, non-invasive neuromodulation technology has attracted more and more attention in the field of neuroscience and rehabilitation medicine. Related research has revealed the correlation between certain brain structures or neuronal activity and cognitive or motor function.

Among them, the development of TMS is particularly rapid.

Transcranial Magnetic Stimulation,TMS

 

Application of TMS in the field of neuromodulation of consciousness disorders

TMS forms a sufficient dose of the electric field in the brain based on the principle of electromagnetic induction, which can depolarize neurons and achieve the effect of regulating cortical excitability. In the field of neuropsychiatric diseases, TMS is an effective non-invasive means of regulation.

 

Bai etc. made a positive attempt in the neuromodulation of TMS in disorders of consciousness. In the study, 16 patients with disorders of consciousness (including 5 in the micro-conscious state and 11 in the vegetative state).

 

Transcranial Magnetic Stimulation,TMS

 

Research methods

Received 10 Hz TMS treatment on the dorsolateral prefrontal lobe for 20 d. Daily treatment consisted of 1000 TMS pulses divided into 10 sessions, each lasting 10 s with 60 s intervals, and the stimulation intensity was 90% of the relative motor threshold.

The stimulation intensity is relative to the resting state motion threshold, and the motion threshold is the minimum TMS pulse intensity that can induce more than 50μV peak-to-peak value in the dorsal first interosseous muscle of the right hand in the resting state.

 

Research result

The study used TMS-EEG and CRS-R scales to evaluate the treatment effect of TMS.

The results of the study found that the CRS-R scores of the 5 MCS patients and 4 of the 11 VS patients were improved, but the MCS patients were significantly improved than the VS patients. Moreover, before and after treatment, the TEP changes in the brains of VS patients were not obvious, the TEP waveforms were simple, and the changing trend was slow, while the TEP waveforms in the brains of MCS patients were complex and contained many components.

In particular, a patient who received rTMS at a frequency of 10 Hz for 20 days showed significant clinical improvement, the CRS-R score increased from 8 to 13, the level of consciousness recovered from MCS- to MCS+, and the EEG assessment results also improved significantly: The patient’s TEP waveform was more complex, the components increased, and the PCI increased to more than 0.3. Moreover, the theory of integration and differentiation of consciousness indicates that rTMS has a positive regulatory effect on patients. Therefore, TMS is feasible as a treatment for disorders of consciousness

 

Summarize

Diagnosis and treatment of patients with impaired consciousness after severe traumatic brain injury is still a worldwide problem. The emergence and application of TMS technology have achieved encouraging results in the diagnosis and treatment of disorders of consciousness and have also promoted human understanding of the mechanism of consciousness generation, which is of great interest to the vast majority of people. Patients and families brought new hope.

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