Abstract
The surgical indications of severe aneurysmal subarachnoid hemorrhage (SAH) are controversial. We consider that early surgery should be carried out on selected cases.
Therefore we try to estimate SAH not only by the neurological state but also by electrophysiological examination (Brain stem evoked potential or short somatosensory evoked potential) for precise evaluation and determination of the indications.
Either brain stem auditory evoked potential (BAEP) or somatosensory evoked potential (SSEP) were performed in 33 cases (W.F.N.S. Grade N, 13 cases; Grade V 20, cases) of 153 severe aneurysmal subarachnoid hemorrhage within 24 hours after onset.
BAEP were recorded between the vertex (Cz) and the ipsilateral mastoid process. Changes in BAEP were classified into 4 grades as follows: Grade 1 was normal i.e. I-V interpeak latency was 4.1+0.2 msec; in Grade 2, I-V interpeak latency was over 4.5 msec on either side; Grade 3, each wave was obscure except for probably wave V, and in Grade 4, there was no response on either side. SSEP were obtained by median nerve stimulation at the wrist. A recording electrode was placed over the surface of the spine at the C-2 vertebral level and over the areas of the somatosensory cortex bilaterally in the C3'/C4' position in the international 10-20 system. The central conduction time (CCT) was the delay between the N14 peak recorded at the C-2 electrode and the N20 peak recorded at the somatosensory cortex. Changes in the SSEP in SAH were classified into 5 grades as follows: Grade 1 was normal, i.e. CCT was 5.8 ± 0.4 msec; in Grade 2, there was prolongation of CCT on the affected side (CCT>6.6 msec); in Grade 3 there was no response on the affected side and the CCT was normal on the unaffected side; in Grade 4, there was no response on affected side and the CCT was prolonged on the unaffected side; and in Grade 5, there was no response on either side.
The outcome was poor if BAEP were abnormal, but the outcome varied in normal BAEP cases. There was a good positive relationship between the SSEP grade and outcome. When both BAEP and SSEP were measured simultaneously on admission, the SSEP grade and the outcome were variable even if BAEP were normal and SSEP were always abnormal whenever BAEP were abnormal.We speculate that brain damage in severe aneurysmal subarachnoid hemorrhage was not caused by primary brain-stem damage, but mainly caused by cerebral perfusion injury in the basal ganglia or thalamus due to direct injury of hemorrhage or secondary intracranial hypertension. Therefore, the SSEP seems to be superior to the BAEP for evaluation of brain damage in severe aneurysmal subarachnoid hemorrhage.
In conclusion, in the treatment in severe aneurysmal subarachnoid hemorrhage, we consider that early surgery should be performed in cases of SSEP Grade 1 or 2, while conservative therapy is recommended in cases of SSEP Grade 3 or more.
