Abstract
The location of a hematoma in the internal capsule (IC) was diagnosed using CT scan. However, the changes in the function of the nervous system caused by the hematoma are hard to evaluated even by using CT scan.
Somatosensory evoked potential (SEP) have been used for the evaluation of the functions of diseases of the central nervous system.
The following experiments are designed to examine the changes in the nervous function caused by types of lateral hematomas in the IC. Eleven adult mongrel dogs were used in this series of experiments. An intracerbral hematoma was made laterally to the internal capsule by an injection of 2 ml of homologous blood in each animal. The SEP and intracranial pressure (ICP) were monitored before and for six experimental hours after making the lesion. Systemic blood pressure and respiratory movements were also simultaneously monitored. The location of the hematoma in each dog was examined in detail by continuous coronal sections of the brain.
The types of hematomas were classified into three groups according to the degree of their invasion into the IC : Group I; a hematoma situated laterally to the IC with some brain tissue remaining between them, Group II; a hematoma invading partially into the IC and Group III; the same as Group I except accompanied by petechial hemorrhages. Significant P1 waves of SEP with their peak latency at ca 22 ms were observed during the control stage and were considered to be indicators of the nervous function. In Group I, P1 was largely within the normal range except at five hours where a significant prolongation of the peak latency occurred. ICPs were normal or slightly increased in this group. The frequency of the disappearences of P1 was the highest in Grouo II. However, the wave appeared again transiently throughout the six experimental hours in spite of a gradual increment of ICP which was the highest in this group. In Group III, P1 suddenly disappeared after four to five experimental hours. ICP increased moderately.
The function of the nervous system seemed to be impaired by the degree of the invasion of the IC by the hematoma. Three representative types appeared with changes of SEP. A recovery of P1 generally within six hours. This was independent of increases in ICPs. From this, it appear that disappearences of P1 were probably caused by ischemia rather than by compression at the IC. Pressure waves appeared frequently with the invasion of a hematoma into the IC in Group II, without relation to the appearence of P1·SEP was very useful in the evaluation of the function of nervous system by the lateral type hematoma in the IC.
