[False negative results by X scanners in intracranial tumors in adults]

We report a cohort of 34 cases, collected between 1978 and 1992, presenting with symptomatic intracranial tumours with a first negative CT scan. Subsequently, the tumours was revealed with a second CT scan or with an another neuroradiological technique (MRI or angiography). These "false negatives" represented 5% of all intracranial tumours seen during the same period of time in the same institution. Gliomas were observed in 67.7% of cases (a majority of them with a high grade). Initially, seizure was the most common clinical presentation (61.8%). Mean delay between the first scan and the definitive diagnosis was 13.4 months. The localization was supra-tentorial in 79.4% and infra-tentorial in 20.6%. This study leads us to discuss the attitude when a first CT scan is normal, more particularly in cases presenting with seizures, and the different factors that can explain the normality of this first CT scan.