Long-term delta-9-tetrahydrocannabinol treatment. Computed tomography of the brains of rhesus monkeys.

High-resolution computed tomographic (CT) scanning of the brain was performed on three groups of rhesus monkeys for the detection of ventricular or cisternal enlargement. These three groups comprised four age-matched controls that had no prior drug usage--four monkeys receiving short-term (two to ten months) orally administered delta-9-tetrahydrocannabinol (delta 9-THC [now known nonproprietarily as dronabinol] and four monkeys receiving long-term (five years) orally administered delta 9-THC. Our results show a statistically significant enlargement of the frontal horns and the bicaudate distance in the long-term group as compared with the control and less significant enlargement of these areas in the long-term group compared with the short-term group. These findings suggest atrophy of the head of the caudate nucleus and the frontal portion of the brain of rhesus monkeys receiving long-term treatment with delta 9-THC.