Role of I-123-IMP SPET in the early diagnosis of borderline chronic hydrocephalus after aneurysmal subarachnoid haemorrhage

Chronic hydrocephalus after aneurysmal subarachnoid haemorrhage (SAH) is ea sily diagnosed in most cases, However, the diagnosis is sometimes difficult ill borderline cases, in which (a) pathognomonic clinical deterioration du e to hydrocephalus is masked by the neurological deficits caused in the acu te stage of SAH and (b) ventricular enlargement is not so marked on CT scan . The pul pose of this study was to investigate whether or not iodine-123 l abelled N-isoDropyl-p-iodoamphetamine (I-123-IMP) single-photon emission to mography (SPET) is of value fur the early diagnosis of borderline chronic h ydrocephalus after SAH. Fifteen patients who met the criteria of borderline chronic hydrocephalus were selected for the study, and underwent a shunt o peration. The patients were divided into a shunt-effective group and a shun t-ineffective group according to neurological improvement after the shunt o peration. I-123-IMP SPET was performed in the acute stage of SAH, within 1 week before the shunt operation, and 2 weeks after the shunt operation. Reg ional cerebral blood flow was estimated by the I-123-IMP autoradiographic m ethod. Pre-shunting periventricular low-perfusion areas showed statisticall y significant differences between the two groups (P<0.05), Tn the shunt-eff ective group, periventricular low-Dcl fusion areas on pre-shunting SPET wer e significantly enlarged compared with those in the acute stage of SAH (P<0 .05), and they were significantly reduced after the shunt operation (P<0.05 ). In the shunt-ineffective group, periventricular low-perfusion areas show ed no significant changes during the course. These results suggest that per iventricular low-perfusion areas enlarge in the early stage of chronic hydr ocephalus after SAH, and that I-123-IMP SPET can be used for both the early diagnosis of borderline chronic hydrocephalus after SAI-I and the predicti on of shunt effectiveness.