Fig. (7) Patient No. 12 showed parallel courses of N20 and 1/vMCA ratios (p <0.01, r = 0.92, C.I. = 0.44 to 0.99). He showed hydrocephalus promptly treated with EVD (point 1) and right parietal oedema (point 2) in MCA area at CT scan (both ratios < 0.65). He maintained N20 amplitude > 1.2 ┬ÁV on the compromised hemisphere and vasospasm (BFV >120 to 180 cm/sec) was detected corresponding to points 2,3,4,5; the patient had clinical transient lateralizing symptoms corresponding to point 2 and recovered a normal clinical picture in subsequent examinations (points 3 to 6); CT scan performed at point 6 was normal (both ratios > 0.65).