Decrease in pituitary apparent diffusion coefficient in normal appearing brain correlates with hypopituitarism following traumatic brain injury

Introduction Following traumatic brain injury (TBI), there may be persistent pituitary deficits despite the presence of normal conventional magnetic resonance (MR) images. Little is known about the association of microstructural changes in the pituitary with pituitary function in TBI patients with normal appearing brain on conventional MR images. Our aim was to quantify changes in pituitary apparent diffusion coefficient (ADC) of normal appearing brain in human traumatic brain injury. Methods Forty-two patients admitted with a diagnosis of mild head injury having normal appearing brain imaging were scanned at 7 days after injury using a quantitative echo planar imaging acquisition to obtain ADC parametric map. Mean pituitary ADC values were compared with a control group (n = 30). Results The TBI group showed a significant decrease in pituitary ADC compared to the controls. Furthermore, the mean ADC was much less in TBI patients with pituitary dysfunction compared to those with normal pituitary function. There was also a correlation between the development of pituitary dysfunction and decreasing ADC (r = 0.82, P < 0.01). Conclusion Our findings suggest that pituitary ADC is a sensitive and independent marker of pituitary damage following traumatic insult, which is useful to detect the microstructural damage in pituitary in normal appearing brain.