Variant sella morphology and pituitary gland height in adult patients with Chiari II malformation: potential pitfall...

To systematically evaluate the sella morphology and pituitary gland height on brain MRI of Chiari II malformation (C2M) patients to understand the observed high incidence of apparent enlargement of the pituitary gland.

Brain MRIs of C2M patients at a single tertiary care adult institution were retrospectively reviewed. We also evaluated two age and gender-matched control groups-patients with normal brain MRI (C1 group) and chronic ventricular shunts (C2 group). The heights of tuberculum sella, dorsum sella, and pituitary gland were measured and compared. The presence or absence of dural thickening was noted.

21 patients were included in each group. In C2M group, a pituitary adenoma was suggested on 24% of the MRIs. The dorsum sella was significantly smaller in the C2M group (4.8 mm) compared to both the C1 group (7.4 mm, p < 0.001) and the C2 group (7.1 mm, p < 0.001). The pituitary gland was also larger in the cranial-caudal dimension in C2M group (8.6 mm) as compared to both the C1 group (6.6 mm, p < 0.01) and the C2 group (6.0 mm, p < 0.001). One C2M patient with a pituitary gland<10 mm was suggested to have a pituitary adenoma on outside MRI, although a normal pituitary gland was seen on pathology.

C2M patients have shallow sella which can accentuate the pituitary gland height. The mean pituitary height was larger in C2M patients, but no functional pituitary pathology was present. It is important to consider sella morphology when evaluating the pituitary gland of C2M patients to avoid unnecessary medical and surgical interventions.