A current perspective of pituitary adenoma MRI characteristics: a review

ABSTRACT

Introduction

MR imaging is an essential and fundamental tool in the diagnosis, management, and follow-up of patients with pituitary adenomas (PAs). Recent advances have continued to enhance the usefulness of this imaging modality.

Areas covered

This article focuses on signal intensity patterns of PAs and associated clinical characteristics, vertical extension patterns, and cavernous sinus invasion with a special focus on the clinical implications that arise. A search using Medline and Google Scholar was conducted using different combinations of relevant keywords, giving preference to recent publications.

Expert Opinion

A higher proportion of GH-secreting PAs are hypointense on T2 weighted images compared to other tumor subtypes. Hypointense tumors are generally smaller compared to hyperintense ones, and among the GH-secreting subgroup, a better response to somatostatin analogue treatment was noted together with an association for a densely granulated pattern. Nonfunctional PAs show a predilection to extend upwards while GH-secreting PAs and prolactinomas show a predominantly inferior extension growth pattern. Further studies to better understand the mechanisms responsible for this behavior are anticipated. Further development, refining and validation of predictive scoring systems for tumor behavior might be useful adjuncts in the management of patients with PAs.

KEYWORDS:

• MRI
• pituitary adenoma
• T2 signal intensity
• vertical extension
• cavernous sinus invasion

Article highlights

• MR imaging is an essential tool in the diagnosis, work up and follow up of patients with pituitary adenomas (PAs). Recent developments in the study of some MR characteristics of PAs have continued to enhance the clinical implications and significance of these characteristics. The importance of obtaining good quality T2 weighted MR images is further reiterated.

• Hypointensity on T2 weighted MR images is more prevalent among GH secreting PAs compared to other PA subtypes. T2 hypointensity could be related to secretory granule content with a significant majority of densely granulated GH-secreting PAs exhibiting such intensity pattern.

• Among GH secreting PAs, hypointense T2 weighted ones showed higher IGF-1 levels, smaller tumour size, less tumour invasiveness, and a better response to somatostatin analogue treatment.

• MR signal intensity patterns amongst prolactinomas are much less studied. A minority of prolactinomas are hypointense on T2 weighted images with some reports suggesting that the latter group can have a higher rate of dopamine agonist resistance.

• Vertical extension patterns among various PA subtypes have shown a greater propensity for non-functional PAs to extend predominantly suprasellarly while GH secreting and prolactinomas exhibiting a predominantly inferior extension pattern.

• Various mechanisms were postulated to explain this difference in vertical extension patterns in the different PA subtypes including growth hormone induced increased sellar size and increased erosion of bone density, and an increased degree of pneumatization of the sphenoid sinus. However further studies are warranted to better understand the mechanisms at play which result in the demonstrated differences in tumour growth behaviour.

• A strong positive relationship was shown in various studies between PA tumour size and cavernous sinus involvement.

Acknowledgments

The author would like to thank Prof J Vassallo for her guidance and support and Dr Lianne Camilleri, Dr Jessica Mangion and Dr Sarah Craus for their assistance in proofreading and manuscript editing.

Declaration of interest

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Reviewer disclosures

Peer reviewers on this manuscript have no relevant financial or other relationships to disclose.

Supplementary material

Supplemental data for this article can be accessed online at https://doi.org/10.1080/17446651.2022.2144230

Additional information

Funding

This paper was not funded