Acta Neurochirurgica Supplementum, Supplement97/1
The first volume of Operative Neuromodulation is devoted to functional neuroprosthetic surgery. Operative neuromodulation is a multidisciplinary biomedical and biotechnological field, whose rapid development affords new opportunities both for treatment of patients and understanding a role of the nervous system in modulation of all other systems of the body. The book has been edited by Prof. D. Sakas (Greece), E. Krames (USA) and B. Simpson (Great Britain), being President and Ex-President of the International Neuromodulation Society. It promotes worldwide spread of important information, accumulated by different authors and concerning various fields of scientific and clinical research in neuromodulation.
The first article of an Introduction, written by the editors, gives a definition of operative neuromodulation and describes fields of its use and potentialities of functional neuroprosthetics of damaged parts of the nervous system. According to them, neuromodulation is a process by which chemical substances, neurons or neural networks excite, inhibit or tune adjacent or remote neurons or neural networks with the purpose of delivering responses, which are better adapted to the demands of the body environment, and improving the life quality of patients. Besides, there are articles, which deal with historical and modern aspects of electrostimulation and its use for treatment of different diseases of the nervous system, including pain, motor disorders, epilepsy, Tourette’s syndrome, coma, respiratory paralysis, enuresis, impotence, etc.
The section, devoted to pain, considers general problems of using neurostimulation and intrathecal drug therapy in chronic pain, as well as application of particular neuromodulation procedures for management of pain syndrome of different localization. The spinal cord is a target of many neurosurgical procedures, intended to treat pain. Electrical modulation of the spinal cord is effective in different benign pain syndromes and intrathecal administration of opioids is an option for treatment of nociceptive and neuropathic cancer-related pain (A.M. Raslan et al., USA). Neuroablation of the spinal cord pain pathway is used mainly to treat pain syndrome of malignant origin. Targets involved include the spinothalamic tract, the midline dorsal column visceral pain pathway and the trigeminal tract in the upper spinal cord. Spinal neuroablation can also involve cellular elements such as with trigeminal nucleotomy and the dorsal root entry zone (DREZ) operation. The DREZ operation is indicated for phantom type pain and root avulsion injuries. A group of authors (A. Koulousakis et al., Germany) presents their own experience of application of intrathecal opioids. Intrathecal administration of opioids with pump implantation is a method of treatment of malignant and non-malignant pain in selected patients. Pump and catheter implantation in a specialized center allows to avoid technical problems of this procedure, in particular catheter dislocation and obstruction, its kinking, dislocation or rupture. A therapeutic effect of intrathecal opioids should be preliminary tested with an external pump, as it permits to select proper diffusion velocity and doses of an injected drug and to prevent development of possible side-effects (nausea, vomiting, constipation, the CNS suppression). It is known, that neuropathic pain is notoriously difficult to manage. Only a few classes of drugs may provide adequate benefit. A good initial effect of percutaneous stimulation of the spinal cord is reduced after some time. A new strategy of treatment of such cases has been developed in the Karolinska University (G. Lind et al., Sweden). A combination of percutaneous stimulation of the spinal cord with daily intrathecal administration of baclofen ensures a very good result in more than 50% of cases with neuropathic pain and inadequate response to percutaneous stimulation of the spinal cord. Some articles of the section are devoted to neurosurgical treatment of pain syndromes with epidural stimulation of the spinal cord. Selection of patients for epidural stimulation of the spinal cord, surgical aspects of electrode implantation at different levels of the spine, side-effects, complications and outcomes are discussed in detail. A good result can be achieved not only in cases with neuropathic pain of different localization, but also in patients with stable severe angina pectoris, stenosis of coronary arteries, pain refractory to optimal doses of nitrates and no interventional possibility to revascularization. Data of medical literature and personal experience of some authors, gained in the field of stimulation of peripheral nerves in neuropathic craniofacial pain (K. Slavin, USA), migraine (L. Rogers, S. Swidan, USA) and refractory headache (R. Weiner, USA) are presented. In the authors’ opinion, described headache syndromes, which are refractory to drugs, can be treated successfully with peripheral stimulation in the majority of cases.
The second section deals with spasticity and related disorders. As for this pathology, all therapeutic measures should be aimed at rehabilitation. Detailed information on spasticity pathophysiology is given in the article by K. Petropoulou et al. Numerous clinical studies have demonstrated, that spasticity is not a static state. All changes develop during several months or even years after a stroke, for example. Besides, spasticity is effected by external factors and stimuli. Thus, management of this state demands profound knowledge and deep understanding of spasticity evolution, which can increase efficacy of such interventions, as intrathecal use of baclofen. This type of therapy has evolved from experimental into standard treatment of severe spasticity of both spinal and cerebral origin. Different aspects of intrathecal baclofen therapy of spastic hypertonia in different neurological diseases, including dystonia, amyotrophic lateral sclerosis, hereditary Friedreich’s ataxia, a vegetative state due to severe craniocerebral trauma, hypoxic encephalopathy and chronic pain syndromes, are considered in detail. Some articles describe indications, pharmacology and efficacy of intrathecal baclofen, as well as advantages and disadvantages of implanted pumps, technique and complications of pump implantation. One more article by K. Petropoulou et al. (Greece) is a bright example of clinical efficacy of inrathecal baclofen therapy. They have demonstrated a great importance of combining neuromodulation and neurorehabilitation during treatment of patients with tetraplegia, being the result of severe head injury (a small cohort of 8 cases). Following pump implantation, all the patients had considerable decrease of spasticity and improvement of cognitive functions and speech, while 4 of them were able to walk between horizontal bars. Thus, management of spastic syndrome of different etiology is most effective, when intrathecal baclofen therapy is a constituent of a multimodality approach.
The section, entitled Cardiovascular, Cerebrovascular and Respiratory Disorders, describes use of spinal cord stimulation in such states. The articles by S. Vincenzo and T. Kyvenditis (Italy) and L. Claeys et al. (Germany) demonstrate, that epidural stimulation of the spinal cord improves microcirculation and healing of small ulcers, relieves ischemic pain, and reduces the amputation rate in cases with severe arterial occlusion in lower extremities. Assessment of skin microcirculation by means of transcutaneous oxygen pressure measurements and videocapillaromicroscopy is necessary for selection of cases, who will benefit most from treatment with epidural stimulation of the spinal cord. According to the authors, this method cannot be applied in patients with an extensive gangrenous lesion of the foot. The articles by C. Upadhyaya and O. Sagher (USA) and F. Robaina and V. Clavo (Spain) show, that cervical spinal cord stimulation increases cerebral blood flow and metabolism in both animal and human models. These results, though preliminary, are very promising for therapy of cerebral ischemia and post-stroke syndrome. Neurostimulation has turned out to be most useful, safe and effective in patients with refractory angina pectoris (S. Ansari et al., Saudi Arabia). It has resulted in fewer angina attacks, decreased consumption of nitrates and improved quality of life. Mechanisms of the spinal cord stimulation action include primary anti-nociceptive effects, involvement of endogenous opiates, anti-sympathetic effects of the nervous system, increase of coronary blood flow and redistribution of myocardial blood flow, placebo effects. Electrical stimulation of the phrenic nerve is a generally adopted treatment for central hypoventilation syndrome due to dysfunction of the brain stem or cervical spinal cord. The article by T. Taira and T. Hori (Japan) deals with technical parameters of effective use of a spinal cord stimulator in cases with chronic hypoventilation. A follow-up period of four years has demonstrated stable and sufficient ventilation in all patients without any complications. An overview, devoted to neuroprostheses for management of dysphagia and written by D. Tyler (USA), gives a detailed description of a mechanism of swallowing and methods of dysphagia management. Laryngeal elevation and vocal fold closure can be an alternative of conventional treatment.
There is a large section, devoted to neurogenic bladder, bowel and sexual disorders and describing indications, technique, early and late complications of neurosurgical interventions in this pathology. Implantation of a permanent sacral stimulator for management of neurogenic bladder should be proceeded by temporary electrostimulation of sacral nerves with the purpose of determining necessary parameters and estimating neurostimulation efficacy. Sacral neuromodulation has demonstrated good results, when used for treatment of neuropathic defecation disorders, but decision on implantation of a stimulator should be made after preliminary assessment of its efficacy. Careful selection of cases for neural augmentation of sexual function is very important (S. Meloy, USA). A positive effect of epidural stimulation of cauda equina has been revealed in women with secondary orgasmic dysfunction. Neuromodulation is effective in chronic pelvic pain and coccygodynia (S. Kothary, Great Britain).
The next section describes achievements of functional electrical stimulation. It is used in different motor disorders after stroke. Functional electrical stimulation accelerates restoration of functions in limb paralysis or reconstructs motor function in complete and incomplete injury of the spinal cord.
The section on neuroprosthetics is devoted to a new field of neurorehabilitation with applying microelectronics, integrated into biomedical microsystems. Neuroprosthetics ensures higher daily activity of patients and their participation in social life.
The last section deals with emerging applications of neuromodulation. F. Robaina and B. Clavo (Spain) describe an effect of stimulation of the cervical spinal cord on oxygenation of brain tumor. Adjuvant stimulation of the cervical spinal cord in cases with high-grade gliomas can increase perfusion and metabolism of a tumor, leading to higher regional concentration of oxygen and drugs and better efficiency of radio-chemotherapy. I. Morita and T. Kanno (Japan) and M. Keith (USA) present their experience of using dorsal column stimulation for a persistent vegetative state. According to them, this stimulation has been effective in 80% of estimated cases. The review on experimental methods for treatment of chronic pain (N. Rainov and V. Heidecke, Germany) summarizes published data on biological therapy of pain with natural and synthetic agents, acting at specific receptors at the spinal or supraspinal level, or with viruses or cell vectors, promoting expression and secretion of these substances. Such therapy provides greater analgesic efficacy.
In conclusion, it should be noted, that Supplement 97/1 to Acta Neurochirurgica elucidates new spheres of neuromodulation application and contains rather interesting information on urgent problems of modern functional neurorehabilitation, which is useful for those studying and practicing not only neurosurgery and neurology, but also cardiology and vascular surgery.