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<.0005), with the anteroposterior diameter through the substantia nigra (R = -.33, P<.004) and with the interpeduncular distance (R = -.24, P<.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. Conclusion: Volumetric and linear measurements of midbrain morphology with MR may prove useful in the investigation of neurologic disorders such as Parkinson disease.