The effects of mannitol and melatonin on MRI findings in an animal model of traumatic brain edema.

OBJECTIVE

The aim of this study was to compare the effects of mannitol and melatonin on brain edema secondary to trauma using magnetic resonance imaging (MRI).

METHODS

A mild traumatic brain injury with the Feeney method was performed upon twelve New Zealand rabbits. Three hours after the trauma was inflicted, MRI images were obtained, then the subjects were divided into two groups: a mannitol group and a melatonin group. The mannitol group (n = 6) was given 2 gr/kg of 20% mannitol IV over 10 minutes and the melatonin group (n = 6) received 100 mg/kg of melatonin IV over 30 minutes. Thirty-three hours after the first MRI, MRI was repeated. The 3-hour and 36-hour post-trauma MRI images in both groups were scored regarding signs of edema and extent of brain tissue protrusion in a blinded fashion by a staff radiologist. Intragroup and intergroup comparisons were made using the Fisher exact test and chi square test. Comparison of brain tissue protrusion measurements was done using the Mann Whitney U test.

RESULTS

Signs of raised intraventricular pressure, contusion and parenchymal edema were more prevelant, and parenchymal protrusion was more prominent on the 36-hour MRI in both mannitol and melatonin groups. No significant difference was found between the melatonin and mannitol groups in any parameter in the MRI images performed 3 and 36 hours after the head trauma.

CONCLUSIONS

In this animal model, melatonin and mannitol had similar effects on brain edema, as demonstrated on MRI 3 and 36 hours after head trauma.