Abstract
There has not been established method for treatment for "persistent vegetative state (PVS)", which was defined by P.Jannette. Although it has a small difference, "vegetative state" was similarly defined by Japanese Association of Neurological Surgery. In this decade, an electrical stimulation of deep brain (DBS) or upper cervical spinal cord (SCS) has been applied to clinical trials, in attempt to treat patients with such a prolonged severely-damaged consciousness. In spite of many cases treated by DBS or SCS, what is its best target is still inquired. Thus, this manuscript reviews DBS or SCS study in Japan in order to postulate its best indications that may be tentative criteria for patient selection. The following problems are hampered to provide a correct answer to the above question. Q1. Even if a patient gets better following this stimulation, the extent of improvement is not able to be quantitatively evaluated, because of a lack of a standard scoring system in estimating how much impaired the consciousness of the chronic state is. Q2. DBS or SCS has begun to be carried out without proving how it works or improves dysfunctioned brain. Thus, nobody knows what is a more reliable parameter, in clinical and neurophysiological examination, to judge whether or not DBS or SCS is useful. As to Q1, the Society for Treatment of Coma has made an attempt to establish a standard scoring system, which consists of 2 kinds of clinical scales [state scale (SS), reaction scale (RS)], several neurophysiological and neuroradiological parameters. Both SS and RS are categorized, base up on 6 items defined by Japanese Association of Neurological Surgery. The preliminary use of the clinical scales showed an extreme usefulness in classifying PVS patients, to evaluate how much responsible to DBS or SCS. Regarding Q2, several important factors are drawn from results of a few of representative institutes. First of all, DBS was enforced mainly at the Deparment of Neurosurgery, Nihon Univ., which proposed its best indication. On the other hand, seven to eight hundreds of patients underwent SCS. Through these experiences, tentative standard indications of SCS may be summarized as follows, 1.Younger than 30 year old, 2.Traumatic origin, 3.Detectable III and Vth wave in auditory brain stem response, 4.Detectable N20 in somatosensory evoked potential, 5.Detectable P300 or P250 6.Only small area of low density in CT 7. Only mild brain atrophy on CT or MRI 8.Within a year after diagnosed as PVS 9.Better than 4 points of SS and 5 points of RS when diagnosed as PVS Since the above criteria is still tentative, further trials are required to elucidate the best indication of SCS. Furthermore, combined established clinical scoring system and neurophysiological examination may open up a refined therapeutical strategy to apply this way of treatment.
