Morphometric Changes of the Human Midbrain with Normal Aging: MR and Stereologic Findings

Purpose: To determine the effects of age on estimated midbrain volume.

Patients And Methods: T2-weighted MR imaging and an unbiased stereologic method were used in 75 volunteers; the subjects ranged in age from 21 to 82 years and were without any significant neurologic or psychiatric disorders.

Results: Age was negatively correlated with estimated midbrain volume (R = -.39, P less than .0005), with the anteroposterior diameter through the substantia nigra (R = -.33, P less than .004) and with the interpeduncular distance (R = -.24, P less than .04). The linear measurements for the right and left side were almost identical. These findings are consistent with prior reports of nigrostriatal degeneration with increasing age. Furthermore, they suggest a close symmetry of age-related changes between the right and left side in normal subjects.

Conclusions: Volumetric and linear measurements of midbrain morphology with MR may prove useful in the investigation of neurologic disorders such as Parkinson disease.