Proc. 15th Ann. Meet. Jap. Soc. Stereotactic and Funct. Neurosurg., Maebashi 1976 Appi. Neurophysiol. 39: 212-215 (1976/77) Correlation between the Neural Noise in the Thalamus after Cerebrovascular Disease and Computerized Tomography A Case Report I tsuo I sobe, K en N ojiri, Y oshio T sukahara, T ohru Shibasaki, M izuho M iyazaki and C hihiro O hye Department of Neurosurgery, Gunma University, School of Medicine, Maebashi Key Words. Neural noise • Thalamus • Cerebrovascular disease ■ Computerized axial tomography • Stroke Abstract. The case is presented of a 45-year-old man who suffered from a sud­ den attack of unconsciousness with right hemiplegia and later developed a spastic hemiparesis accompanied by involuntary movement of the right upper limb. CT scan revealed an old putaminal hemorrhage and almost intact thalamus, but neural noise recordings during the stereotactic thalamotomy of this case showed marked decrease of the neural activity in the thalamus suggesting some functional changes. Introduction Downloaded by: Temple University 155.247.166.234 - 1/6/2020 1:27:22 PM The recent development of computerized tomography has brought new information in the diagnosis of many patients suffering from neurological disorders. It is stated that the system yields approximately 100 times more information than conventional X-ray systems [1], But there are some limitations of CT scan diagnosis. For example, al­ though CT scan is able to detect small differences of the absorption coef­ ficients of each tissue, the absorption coefficients may not always reflect the functional states of the structures. In this report, a peculiar experience of a case of involuntary move­ ment after intracerebral hemorrhage treated with stereotactic thalamoto­ my will be presented. I sobe /N o jiri /T sukahara/S hibasaki/M iyazaki/O hye 213 F ig.l. CT scan showing low absorption abnormality in the area corresponding to the left putamen and pallidum; slight ventricular dilatation, and slight widening of sulci but intact thalamus. Case Report Downloaded by: Temple University 155.247.166.234 - 1/6/2020 1:27:22 PM A 45-year-old man was aware of abnormal movement of the right hand on June 19, 1973 when he was working. He soon became unconscious for several hours with hemiplegia on the right side. Although there was gradual improvement in the hemiparesis, he developed tremor-like involuntary movements in the right upper limb and numbness on the affected side about 3 years later. On admission on July 16, 1976, he was alert and there was no mental impairment. The patient had a right hemiparesis with severe spasticity, sustained clonus and tremor in posture and movement in the right upper limb. A mild right central facial paresis and dysarthria were noted. There was slight disturbance of superficial and deep sensation on the right side accompanied by dysesthesia. The blood pressure was 170/130. After CT scan it was assumed that he had suffered from intracerebral hemorrhage in the left putaminal region (fig . 1). EEG revealed an irregular slow wave focus in the left an­ terior temporal area. The surface electrode EMG from the right biceps and triceps brachii, flexor and extensor carpi muscles showed irregular 6-10 Hz grouping dis­ charges, especially when he raised or abducted his right upper limb. Left thalamoto- 214 I sobe /N o jiri /T sukahara/S hibasaki/M iyazaki/O hye Fig. 2. After simultaneous recording by two electrodes (anterior and posterior), the level of the neural noise at several points of deep subcortical structures in this case is plotted and superimposed on the corresponding thalamic atlas of Schaltenbrand and Bailey (s.l. 15.0). Height of hatched area along the tracks indicates the level of neural noise. CA = Anterior commissure; CP = posterior commissure; MP = midpoint of intercommissural line. my was done for his involuntary movement under local anesthesia using Leksell’s apparatus on July 26, 1976. Prior to making a lesion, the neural noise in the deep subcortical structures was recorded by two semimicroelectrodes inserted in the sagit­ tal plane from the left frontal burr hole to the VIM area under radiological control. During insertion of the electrode, the neural noise level at several points along two tracks was quantitatively estimated with the noisemeter [2], It was revealed that the level of neural noise in the left thalamus was markedly reduced compared with that in the usual parkinsonian case (fig. 2, 3). It is also note­ worthy that the neural noise level at the caudate nucleus and subthalamic region was quite active in this case as in usual case. The involuntary movement was abol­ ished by a thalamocapsular lesion. Discussion Downloaded by: Temple University 155.247.166.234 - 1/6/2020 1:27:22 PM It is said that the anatomical resolution of CT scan with a 160 X 160 matrix is theoretically 1.5 mm square. Under this condition, the present case showed an almost normal thalamus by CT scan. The neural noise in his thalamus, however, showed marked decrease compared with that in parkinsonian cases. Neural noise, multiple-unit background fast activity, has been related primarily to the action potential discharges of cells and fibers surrounding Neural Noise and CT Scan 215 20 15 10 5 0 *- -5 Fig. 3. The same demonsiration of neural noise as in figure 2, but in a case of usual parkinsonism. the recording electrodes. Its amplitude is thought to be more probably a function of cell size than fiber contributions, and synchrony of potential discharges [3]. As the amplitude of the neural noise in the thalamus was very much lower than the usual case, it might be reasonable to assume that function­ al changes took place which could not be detected by CT scan. References 1 T averas, J. M. and W ood, H. E.: Diagnostic neuroradiology, vol. 2, p.997 (Wil­ liams & Wilkins, Baltimore 1976). 2 F ukamachi, A.; O hye, C., and Saito, Y.: Estimation of the neural noise within the human thalamus (in press). 3 G rover, F. S. and Buchwald, J. S.: Correlation of cell size with amplitude of background fast activity in specific brain nuclei. J. Neurophysiol. 33: 160-171 (1970). Downloaded by: Temple University 155.247.166.234 - 1/6/2020 1:27:22 PM Dr. I tsuo I sobe, Department of Neurosurgery, Gunma University, School of Medicine, 3-39-22, Showa-machi, Maebashi (Japan)