Background: Third ventricular colloid cysts account for 0.5% - 1.5% of all intracranial tumors. A thorough search of the world literature since 1858 revealed 1167 cases, for which a more than one-third (36%) management mortality was estimated. One third of the reported cases had modern diagnostics and surgery with minimal morbidity and nearly no mortality. The primary goal of this study was to assess the incidence and present-day management outcome of these lesions in the strictly defined area of Eastern Finland.
Methods: In a series of 2000 patients with brain tumors from our catchment area (870,000 inhabitants in eastern Finland) during a 14.5-year period (years 1980-1994), 40 patients (mean age, 45 years; range, 19-75 years, with 21 females) had a third ventricular colloid cyst. Thirty-one patients had transcallosal extirpation of their cysts. One additional tumor was extirpated by the infratentorial supracerebellar route to include simultaneous biopsy of a tectal tumor (lipoma). One elderly male with severe cardiac disease received a ventriculoatrial shunt. Five patients, admitted deeply unconscious, died. In two of these five patients, desperate shunting operations were done, but, in the remaining three moribund patients, no treatment was considered to be of any benefit. Two patients with small tumors are being followed up.
Results: The far lateral transcallosal transforaminal extirpation of the cyst has served our patients well. There was no surgical mortality. The outcome was excellent in 30 patients and good in 3 patients. Follow-up time ranged from 2 months to 14.5 years (mean, 4.3 years). There were no tumor recurrences. Despite good surgical results, management mortality was as high as 13%,
Conclusions: The incidence of third ventricular colloid cysts is at least 3.2/1 million/1 year. Even nowadays, up to one fifth of these completely benign and treatable tumors are detected too late, with calamitous consequences.