Retinal artery pressure and cerebral artery perfusion pressure in cerebrovascular occlusive disease

Abstract

The objectives of the investigation were to measure the retinal artery pressure (RAP) and cortical artery pressure (CAP) in patients undergoing superficial temporal artery to middle cerebral artery (STA-MCA) bypass, to study the relationship between these pressures, and to evaluate our ability to predict CAP on the basis of RAP. The 44 patients undergoing bypass surgery included 26 with ipsilateral internal carotid artery (ICA) occlusion (Group I), 5 with bilateral ICA occlusion (Group II), 4 with inaccessible ICA stenosis proximal to the ophthalmic artery (OA) (Group III), 2 with ICA stenosis distal to the OA (Group IV), 3 with ICA occlusion distal to the OA (Group V), 2 with MCA stenosis (Group VI), and 2 with MCA occlusion (Group VII). Five patients undergoing craniotomy for an asymptomatic saccular aneurysm were used as controls. Mean RAP (MRAP) was measured by ophthalmodynamometry (ODM) and was expressed as a ratio of the mean systemic arterial blood pressure (i.e., MRAP/MSAP). The mean MRAP/MSAP for combined Groups I, II, and III with ICA occlusion proximal to the OA was significantly lower than both the control group (P = 0.0001) and the combined Groups IV, V, VI, and VII with occlusive lesions distal to the OA (P = 0.0001). Six patients in Groups I and II with venous stasis retinopathy had a mean MRAP/MSAP of 0.18 + 0.11. Mean cortical artery pressure (MCAP) was measured by inserting a 26 gauge needle into a small cortical artery and was expressed as the MCAP/MSAP ratio. Mean MCAP/MSAP was less than 0.50 for all groups except Group III. The mean MCAP/MSAP for combined Groups IV, V, VI, and VII was significantly lower than in combined Groups I, II, and III (P = 0.02). RAP measured by ODM was moderately predictive of CAP in patients with an occlusive lesion of the ICA proximal to OA (r = 0.50). The degree of correlation was highest for those patients with a very low MCAP/MSAP (i.e., ≤0.25) ratio (r = 0.74). These findings indicate that ODM may be helpful in identifying patients with severe cerebral hypoperfusion secondary to ICA occlusive disease proximal to the OA. (Neurosurgery 18:716-720, 1986)