Jean-Louis Dietemann

Computed tomography of the pituitary gland

This book is written entirely to include the imaging of the pituitary gland by computed tomography (CT). The first three chapters illustrated technical aspects of scanning, anatomic depiction of the gland by CT, and the use of dynamic CT scanning for detecting and displaying abnormalities. The chapters discuss and illustrate various types of pathologic processes in and around the pituitary gland. One short but very helpful chapter demonstrates potential pitfalls due to the combination of anatomic variants and the geometry of CT sections. Some illustrations of disease processed are depicted by magnetic resonance imaging. All major types of pituitary diseases are illustrated. Lists of readily available English-language references are available. A small subject index is provided at the end of the book in which the illustrations are identified by use of a special numeric front.

Pituitary MRI characteristics in 297 acromegaly patients based on T2-weighted sequences

Responses of GH-secreting adenomas to multimodal management of acromegaly vary widely between patients. Understanding the behavioral patterns of GH-secreting adenomas by identifying factors predictive of their evolution is a research priority. The aim of this study was to clarify the relationship between the T2-weighted adenoma signal on diagnostic magnetic resonance imaging (MRI) in acromegaly and clinical and biological features at diagnosis. An international, multicenter, retrospective analysis was performed using a large population of 297 acromegalic patients recently diagnosed with available diagnostic MRI evaluations. The study was conducted at ten endocrine tertiary referral centers. Clinical and biochemical characteristics, and MRI signal findings were evaluated. T2-hypointense adenomas represented 52.9% of the series, were smaller than their T2-hyperintense and isointense counterparts (P<0.0001), were associated with higher IGF1 levels (P=0.0001), invaded the cavernous sinus less frequently (P=0.0002), and rarely caused optic chiasm compression (P<0.0001). Acromegalic men tended to be younger at diagnosis than women (P=0.067) and presented higher IGF1 values (P=0.01). Although in total, adenomas had a predominantly inferior extension in 45.8% of cases, in men this was more frequent (P<0.0001), whereas in women optic chiasm compression of macroadenomas occurred more often (P=0.0067). Most adenomas (45.1%) measured between 11 and 20 mm in maximal diameter and bigger adenomas were diagnosed at younger ages (P=0.0001). The T2-weighted signal differentiates GH-secreting adenomas into subgroups with particular behaviors. This raises the question of whether the T2-weighted signal could represent a factor in the classification of acromegalic patients in future studies.

The Pituitary Stalk

The pituitary stalk extends from the anterior part of the floor of the third ventricle to the neurohypophysis. The presence of the hypophyseal portal system accounts for the marked enhancement and the constant visualization of the pituitary stalk on CT scans after intravenous enhancement. Modifications in thickness and in topography due to intra- or suprasellar pathological processes will thus be easily visualized.

Dynamic CT of the Pituitary Gland

Dynamic pituitary CT scan is of major benefit for diagnosis of the smallest pituitary lesions. In 1982, the pituitary dynamic CT technique was suggested in view of the inadequacy of conventional techniques, even using high-resolution systems, for demonstration of the smallest intrasellar adenomas. Visualization of the pituitary capillary bed with this technique is today as fundamental for diagnosis of intrasellar lesions as was demonstration of the calcified pineal gland or internal cerebral vein for identification of the midline of the brain. A brief review of pituitary blood supply is necessary to understand the utility of the dynamic scan (Fig. 3.1).

Pituitary Adenomas with Suprasellar Extension

Since the old category of “chromophobe” adenomas has been abandoned, prolactinomas appear to be the most frequent adenomas with extrasellar extension. Nonsecretory or nonfunctional adenomas are seen less commonly.

The Empty Sella Turcica

The empty sella turcica is characterized by an intrasellar herniation of the suprasellar subarachnoid spaces, favored by a dehiscence of the diaphragma sellae. This intrasellar irruption of subarachnoid spaces determines a flattening of the pituitary gland. An empty sella turcica relative to an opening of the diaphragma sellae is termed “primary empty sella turcica;” it should be distinguished from the “secondary empty sella turcica” seen after treatment of an intrasellar tumor (surgery, X-ray therapy, chemotherapy).

Radiologic Anatomy of the Sellar Region

We will here briefly describe both the normal CT pattern and the major anatomical variants involving the pituitary gland, the sella turcica, the vascular and nervous structures of the cavernous sinus and the suprasellar cistern. The CT slices can be correlated with anatomical sections presented in the sagittal, coronal, and axial planes (Figs. 2.1, 2.2, and 2.3).

CT of the Sellar Region After Surgery and/or Radiotherapy

The transsphenoidal approach has become the procedure of choice for removal of intrasellar lesions. The subfrontal approach is reserved for large suprasellar tumors and adenomas with hourglass expansion. Postoperative CT scans can demonstrate surgical changes, complications, residual or recurrent tumors.

Rare Intrasellar Disorders

The CT appearance of most of rare intrasellar lesions is usually nonspecific and surgical investigation is frequently the final means of a reliable diagnosis. However, the confrontation of CT, clinical and biological results sometimes helps to guide the diagnosis; this is particularly the case with lymphocytic adenohypophysis and sarcoidosis (see Table 1).

Rare Pituitary Adenomas

TSH- and FSH- LH-secreting pituitary adenomas are rather rare. Gonadotropin-producing adenomas may be misdiagnosed as nonsecreting adenomas.