gms | German Medical Science

Objective: In patients (pts) with SAH vasospasms (VS) are the most threatening complication in the first 3 weeks. In daily practice of patients with reduced consciousness the red flag for VS is the increase of blood blow velocity (BFV) in TCD. However, VS of the posterior cerebral artery (PCA) distal to the P1 segment are often insufficiently identified by TCD, due to the angel between the PCA blood stream axis and the sonographic beam. BFV does not inform about functional capacity. However, VEP are depending on the cerebral oxygen metabolism. Recording of prolonged latency (La) and reduced amplitude (Am) might suggest an insufficient metabolism. There is no report in the literature using VEP and TCD as combined techniques in SAH with VS of the basilar artery branches.

Methods: In comatose pts with SAH daily TCD including the PCA was performed from day 3 till days 21. As soon as mean BFV increased above 110cm/s repeated VEP measurements were added. 2 plastic pads (diameter 14 mm), one per eye, equipped with 19 stimulating white LED lights (each diameter 1,5 mm) were connected to an IOM machine (Eclipse MedtronicR), placed on the closed eye lid and covered with black cotton eye patches. Flicker frequency was 2 Hz, intensity was increased till occurrence of peak N1/P1. Stimulation was performed with bilateral alternating light and mono-ocular stimulation. VEP were recorded by needle electrodes at Oz, O1, O2 and Cz. This allowed calculation of VEP La and Am for each occipital lobe.

Results: TCD identified P1 in all pts on both sides, P2 in 4/6 on at least 5 days and in 4 pts on 4 days. In 3 pts mean BFV and VEP (N1 68,5 - 78,4) and P1 (100,4 – 108,3) were normal. CCT did not show infarcts. In 3 other pts (2 with a. basilaris aneurysms, 1 with ACA aneurysm) mean BFV was increased in MCA/ACA and in 2 of these pts also in PCA (above 120 cm/s). DSA confirmed VS. CCT identified Infarcts in the PCA territory in these 3 pts. In these 3 pts VEP La (P1 above 115 ms) after VEP stimulation of one or both eyes was due to the development of an unilateral PCA infarct. In 2 pts VEP La increased before CT-visualization of infarcts.

Conclusion: This is to our knowledge the 1st report on measurements of both TCD and VEP in SAH during the acute state. VEP may indicate an insufficient oxygen metabolism despite increased BFV due to VS. It seems possible that the reliability of TCD in the posterior circulation is supplemented by VEP measurements.