Normal pituitary stalk: high-resolution MR imaging at 3T

Abstract

Background and purpose: Knowing the normal imaging appearance of the pituitary stalk is important for the diagnosis of pituitary infundibular lesions, and more accurate assessment of the stalk may be possible at 3T than at 1.5T. Our purpose was to evaluate the normal pituitary stalk by use of high-resolution MR imaging at 3T.

Materials and methods: Sagittal MPRAGE images and high-resolution oblique-axial T2-weighted images of the pituitary stalk were acquired in 29 healthy volunteers (16 men and 13 women; mean age, 28 years; age range, 21-43 years) at 3T. The diameter and length of the pituitary stalk and the depth of the infundibular recess were measured. Signal intensity of the stalk was visually evaluated on T2-weighted images.

Results: The AP and transverse diameters of the pituitary stalk were 2.32 +/- 0.39 mm and 2.16 +/- 0.37 mm at the pituitary insertion, respectively, and 3.25 +/- 0.43 mm and 3.35 +/- 0.44 mm at the level of the optic chiasm. No significant differences were observed between the AP and transverse diameters at each level. The length of the stalk was 5.91 +/- 1.24 mm, and the depth of the infundibular recess was 4.69 +/- 0.87 mm. The stalk showed central hyperintensity with a peripheral rim of isointensity in 20 subjects (69%) and homogeneous isointensity in 9 subjects (31%).

Conclusions: The data of the current study can serve as standard measurements of the normal pituitary stalk. The central hyperintensity and peripheral rim may represent the infundibular stem and pars tuberalis, respectively.

Fig 1.

The method of measurement of the pituitary stalk and infundibular recess. A, Schematic illustration of the pituitary stalk in the midsagittal plane demonstrates the depth of the infundibular recess (D) and the length of the pituitary stalk (L). The 2 lines indicate the levels at which the diameters of the pituitary stalk were measured (PI = the pituitary insertion of the pituitary stalk, OC = the level of the optic chiasm). B, Median sagittal MPRAGE image shows the depth of the infundibular recess (D) and the length of the pituitary stalk (L).

Fig 2.

T2-weighted oblique-axial images of the pituitary stalk of a 34-year-old healthy woman. Consecutive images with 2-mm intervals are presented from superior (A) to inferior (E), along with a reference line of each imaged level on the midsagittal MPRAGE image. The infundibular recess (arrows) ends at the midstalk level. The parenchyma of the pituitary stalk at its insertion on the pituitary gland shows central hyperintensity with a peripheral rim of isointensity (arrowhead) compared with the cerebral white matter.

Fig 3.

T2-weighted oblique-axial image of the pituitary stalk of a 34-year-old healthy man. The pituitary stalk shows homogeneous isointensity with the cerebral white matter at its insertion on the pituitary gland.

Fig 4.

Schematic sagittal illustration of the pituitary stalk and gland demonstrating its components. The adenohypophysis is shaded in gray. The line indicates the level of the pituitary insertion at which the signal intensity of the pituitary stalk was assessed.