Comparison of computerized tomography and magnetic resonance imaging for the examination of the pituitary gland in patients with Cushing's disease

MRI-negative Cushing's Disease: Management Strategy and Outcomes in 15 Cases Utilizing a Pure Endoscopic Endonasal Approach

BACKGROUND

Cushing's disease (CD) is among the most common etiologies of hypercortisolism. Magnetic resonance imaging (MRI) is often utilized in the diagnosis of CD, however, up to 64% of adrenocorticotropic hormone (ACTH)-producing pituitary microadenomas are undetectable on MRI. We report 15 cases of MRI negative CD who underwent surgical resection utilizing a purely endoscopic endonasal approach.

METHODS

Endoscopic endonasal transsphenoidal surgery (EETS) was performed on 134 CD cases by a single surgeon. Fifteen cases met inclusion criteria: no conclusive MRI studies and no previous surgical treatment. Data collected included signs/symptoms, pre- and post-operative hormone levels, and complications resulting from surgical or medical management. Data regarding tumor diameter, location, and tumor residue/recurrence was obtained from both pre- and post-operative MRI. Immunohistochemistry was performed to assess for tumor hormone secretion.

RESULTS

Aside from a statistically significant difference (P = 0.001) in histopathological results between patients with negative and positive MRI, there were no statistically significant difference between these two groups in any other demographic or clinical data point. Inferior petrosal sinus sampling (IPSS) with desmopressin (DDAVP®) administration was performed on the 15 patients with inconclusive MRIs to identify the origin of ACTH hypersecretion via a central/peripheral (C/P) ratio. IPSS in seven, five and three patients showed right, left, and central side lateralization, respectively. With a mean follow-up of 5.5 years, among MRI-negative patients, 14 (93%) and 12 patients (80%) achieved early and long-term remission, respectively. In the MRI-positive cohort, over a mean follow-up of 4.8 years, 113 patients (94.9%) and 102 patients (85.7%) achieved initial and long-term remission, respectively.

CONCLUSIONS

Surgical management of MRI-negative/inconclusive Cushing's disease is challenging scenario requiring a multidisciplinary approach. An experienced neurosurgeon, in collaboration with a dedicated endocrinologist, should identify the most likely location of the adenoma utilizing IPSS findings, followed by careful surgical exploration of the pituitary to identify the adenoma.

T2 hypointense signal discovered incidentally at the posterior edge of the adenohypophysis on MRI: its prevalence and morphology and their relationship to age

PURPOSE

T2 hypointense signal at the posterior edge of the adenohypophysis (T2HSPA) on magnetic resonance imaging (MRI) is incidentally encountered. We aimed to investigate the prevalence and morphology of T2HSPA and their relationship to age.

METHODS

A total of 212 cases between 3 and 88 years old were examined. Sagittal T2-weighted image (T2WI) was evaluated for the presence of T2HSPA, which classified by its morphology into two types (belt-like or nodal). The Wilcoxon rank sum test and chi-square test were used to evaluate the differences between the groups. The T2HSPA was extracted by ImageJ software and measured as a cross-sectional area (CSA) quantitatively by threshold setting. We examined the relationship between CSA of T2HSPA and age, and Spearman's correlation coefficients were used for statistical analysis.

RESULTS

Of the 212 cases, 80 (37.7%) were identified with T2HSPA. The groups with T2HSPA were significantly younger than the groups without it (p = .01). Groups with belt-like T2HSPA were significantly younger than the groups with nodal T2HSPA (p = .01). There was a weak negative correlation between CSA of T2HSPA and age (p = .02).

CONCLUSION

T2HSPAs were incidentally detected in 37.7% of all cases, tended to be more common in younger cases, and their morphology was related to age. They seem to have little clinical significance as they tend to decrease in size with age.

Pre- and postoperative 68 Ga-DOTATOC positron emission tomography for hormone-secreting pituitary neuroendocrine tumours

OBJECTIVES

Somatostatin receptors (SSTRs) are potential targets for detecting pituitary neuroendocrine tumours (PitNETs) that can be visualized effectively with ⁶⁸ Ga-labelled PET tracers. With this study, we have evaluated the diagnostic properties of such a tracer, ⁶⁸ Ga-DOTATOC, in patients with hormone-producing PitNETs before and after surgery.

DESIGN/METHODS

This prospective case-control study presents preoperative positron emission tomography (PET) and histopathological data in 18 patients with somatotroph (n = 8), corticotroph (n = 7) and thyrotroph (n = 3) PitNETs. Patients were scanned pre- and postoperatively with ⁶⁸ Ga-DOTATOC PET. For the postoperative part of the study, patients with gonadotroph tumours (n = 7) were also included. Fifteen pituitary healthy controls underwent the same protocol once. The maximum standard uptake value (SUV_max ) was analysed in manually outlined regions around the tumour in patients and around the pituitary gland in controls. specimens were collected during surgery in subjects for assessment of adenohypophyseal tumour cell type and the SSTR expression.

RESULTS

Thyrotroph tumours showed higher uptake (median SUV_max 41.1; IQR 37.4-60.0) and corticotroph tumours lower uptake (SUV_max 6.8; 2.6-9.3) than normal pituitary gland (SUV_max 13.8; 12.1-15.5). The uptake in somatotroph tumours (SUV_max 15.9; 11.6-19.7) was similar to the uptake in the pituitary gland. There was a strong correlation between SUV_max and SSTR2 expression (r = .75 (P < .01)). In the postoperative evaluation, PET was able to correlate tracer uptake with biochemical cure and noncure in patients with an abnormal postoperative magnetic resonance image and a preoperative tumour uptake SUV_max  > 13.8.

CONCLUSIONS

⁶⁸ Ga-DOTATOC PET can be used to detect thyrotroph tumours in the pre- and postoperative imaging assessment. Corticotroph tumours had a significantly lower uptake compared to the pituitary gland but without a distinct increased tumour uptake the clinical postoperative value is limited.

Feline comorbidities: Recognition, diagnosis and management of the cushingoid diabetic

PRACTICAL RELEVANCE

Diabetes mellitus (DM) is a common feline endocrinopathy, and is often driven by underlying insulin resistance with associated pancreatic beta (β)-cell dysfunction. Although spontaneous hyperadrenocorticism (HAC) with hypercortisolemia (hypercortisolism) is relatively uncommon in cats, it is a well-established cause of insulin resistance and is routinely associated with DM in this species.

CLINICAL CHALLENGES

Many of the clinical signs associated with feline HAC are subtle and may be attributed to concurrent DM or the aging process. Failure to recognize HAC in the diabetic cat can impact patient wellbeing and predispose the patient to progressive compromise. Unfortunately, it can be difficult to establish a diagnosis of HAC, as test results may be influenced by poor diabetic regulation, and protocols are different to those used in canine patients. Treatment options depend on the underlying cause, and often require careful, ongoing assessment and modulation of both adrenal function and insulin requirements. However, various approaches have been shown to either improve glycemic control in cats with sustained insulin dependence, or facilitate diabetic remission.

EVIDENCE BASE

This review summarizes the current literature on feline HAC, with a particular focus on cats with concurrent DM. The clinical findings that suggest HAC are discussed, along with an outline of diagnostic options and their limitations. Published outcomes for various medical options, surgical procedures and radiation therapy are provided. The authors also share their thoughts on the safe and effective management of cats with HAC and DM, with an emphasis on the anticipation and recognition of changing insulin requirements.

Pituitary magnetic resonance imaging vs. bilateral inferior petrosal sinus sampling: comparison between non-invasive and invasive diagnostic techniques for Cushing's disease-a narrative review

Cushing's syndrome is a pathological clinical condition caused by an exposure of elevated cortisol levels over a long period of time. It is therefore essential to establish what the cause of hypercortisolism is. In most cases (about 80%) the pathological process is due to adrenocorticotropic hormone (ACTH), while in a minor part of the cases (about 20%) the cause is represented by a pathology of the adrenal glands and therefore not related to ACTH. Most patients with ACTH dependent Cushing's syndrome have a pituitary microadenoma; in the remaining cases (30%), the high level of cortisol is linked to an ectopic secretion of ACTH. Surgical removal of the pituitary adenoma represents the treatment of choice in Cushing's disease (CD) patients; it is therefore necessary to identify and precisely locate the pituitary tumour responsible for the secretion of ACTH. Adequate diagnostic information is very often, even with magnetic resonance imaging (MRI), and in these cases we rely on bilateral inferior petrosal sinuses sampling (BIPSS). This procedure is considered the gold standard method for the diagnosis, but like any other diagnostic method it is not free from erroneous results such as false positives or false negatives.

Transsphenoidal Surgery in Canines: Safety, Efficacy and Patient Selection

Pituitary-dependent hyperadrenocorticism (PDH) is the cause of approximately 80-85% of naturally occurring cases of hyperadrenocorticism(HAC) in canines and is triggered by an adrenocorticotropic hormone (ACTH)-producing pituitary adenoma or hyperplasia of the corticotroph in the pituitary anterior lobe or intermediate lobe. Transsphenoidal surgery(TSS) is an effective treatment that can directly remove pituitary tumors that cause PDH in canines under a single course of general anesthesia. However, careful evaluations of the definitive diagnosis, adenoma size and growth rate, relationship with surrounding tissue, general condition, and neurosurgical procedural skill involved in each case are important to determine TSS suitability. The basic principle is to confirm that the present HAC case is PDH, that is, an ACTH-producing adenoma or the hyperplasia of the corticotroph originating from either the pituitary anterior or intermediate lobe. Evaluations based on endocrinology, particularly plasma ACTH concentration, and imaging diagnosis, particularly MRI is essential for definitive diagnosis. Enlarged pituitary tumors can shorten the post-TSS survival time, increase the recurrence rate of clinical symptoms, and increase the risk for developing permanent central diabetes insipidus. Therefore, complete removal of adenomas of up to Grade IIIA according to the MRI-based classification system is relatively easy to achieve with TSS, and long-term remission and survival can be expected.

Transsphenoidal Surgery for Pituitary Tumors and Other Sellar Masses

Transsphenoidal surgery is an option for dogs and cats with functional and nonfunctional pituitary masses or other sellar and parasellar masses. An adrenocorticotropic hormone-secreting tumor causing Cushing disease is the most common clinically relevant pituitary tumor in dogs, and the most common pituitary tumor seen in cats is a growth hormone-secreting tumor causing acromegaly. Transsphenoidal surgery can lead to rapid resolution of clinical signs and provide a cure for these patients. Because of the risks associated with this surgery, it should only be attempted by a cohesive pituitary surgery group with a sophisticated medical and surgical team.

Metabolic In Vivo Visualization of Pituitary Adenomas: a Systematic Review of Imaging Modalities

OBJECTIVE

Pituitary adenomas (PAs) are the most common intrasellar mass. Functional PAs constitute most of pituitary tumors and can produce symptoms related to hormonal overproduction. Timely and accurate detection is therefore of vital importance to prevent potentially irreversible sequelae. Magnetic resonance imaging is the gold standard for detecting PAs, but is limited by poor sensitivity for microadenomas and an inability to differentiate scar tissue from tumor residual or predict treatment response. Several new modalities that detect PAs have been proposed.

METHODS

A systematic review of the PubMed database was performed for imaging studies of PAs since its inception. Data concerning study characteristics, clinical symptoms, imaging modalities, and diagnostic accuracy were collected.

RESULTS

After applying exclusion criteria, 25 studies of imaging PAs using positron emission tomography (PET), magnetic resonance spectroscopy (MRS), and single photon emission computed tomography were reviewed. PET reliably detects PAs, particularly where magnetic resonance imaging is equivocal, although its efficacy is limited by high cost and low availability. Single photon emission computed tomography possesses good sensitivity for neuroendocrine tumors but its use with PAs is poorly documented. MRS consistently detects cellular proliferation and hormonal activity, but warrants further study at higher magnetic field strength.

CONCLUSIONS

PET and MRS appear to have the strongest predictive value in detecting PAs. MRS has the advantage of low cost, but the literature is lacking in specific studies of the pituitary. Due to high recurrence rates of functional PAs and low sensitivity of existing diagnostic workups, further investigation of metabolic imaging is necessary.

Pituitary magnetic resonance imaging in Cushing's disease

Adrenocorticotropin-secreting pituitary tumor represents about 10 % of pituitary adenomas and at the time of diagnosis most of them are microadenomas. Transsphenoidal surgery is the first-line treatment of Cushing's disease and accurate localization of the tumor within the gland is essential for selectively removing the lesion and preserving normal pituitary function. Magnetic resonance imaging is the best imaging modality for the detection of pituitary tumors, but adrenocorticotropin-secreting pituitary microadenomas are not correctly identified in 30-50 % of cases, because of their size, location, and enhancing characteristics. Several recent studies were performed with the purpose of better localizing the adrenocorticotropin-secreting microadenomas through the use in magnetic resonance imaging of specific sequences, reduced contrast medium dose and high-field technology. Therefore, an improved imaging technique for pituitary disease is mandatory in the suspect of Cushing's disease. The aims of this paper are to present an overview of pituitary magnetic resonance imaging in the diagnosis of Cushing's disease and to provide a magnetic resonance imaging protocol to be followed in case of suspicion adrenocorticotropin-secreting pituitary adenoma.

Multiple Pituitary Adenomas: A Systematic Review

PubMed, Scopus, and Web of Science Core Collection databases were systematically searched for studies reporting synchronous double or multiple pituitary adenomas (MPA), a rare clinical condition, with a vague pathogenesis. Multiple adenomas of the pituitary gland are referred to as morphologically and/or immunocytochemically distinct tumors that are frequently small-sized and hormonally non-functional, to account for the low detection rate. There is no general agreement on how to classify MPA, various criteria, such as tumor contiguity, immunoreactivity, and clonality analysis are being used. Among the component tumors, prolactin (PRL)-immunopositive adenomas are highly prevalent, albeit mute in the majority of cases. The most frequent clinical presentation of MPA is Cushing's syndrome, given the fact that in more than 50% of reported cases at least one lesion stains for adrenocorticotrophic hormone (ACTH). Plurihormonal hyperactivity may be diagnosed in a patient with MPA when more than one tumor is clinically active (e.g., ACTH and PRL) or in cases with at least one composite tumor (e.g., GH and PRL), to complicate the clinical scenario. Specific challenges associated with MPA include high surgical failure rates, enforcing second-look surgery in certain cases, and difficult preoperative neuroradiological imaging evaluation, with an overall sensitivity of only 25% for magnetic resonance imaging to detect distinct multiple tumors. Alternatively, minor pituitary imaging abnormalities may raise suspicion, as these are not uncommon. Postoperative immunohistochemistry is mandatory and in conjunction to electron microscopy scanning and testing for transcription factors (i.e., Pit-1, T-pit, and SF-1) accurately define and classify the distinct cytodifferentiation of MPA.

High-resolution fluorodeoxyglucose positron emission tomography and magnetic resonance imaging findings of a pituitary microtumor in a dog

A 16-year-old, castrated, male English cocker spaniel dog was presented due to generalized alopecia. Routine clinical pathology, endocrine and abdominal ultrasonography results were consistent with a diagnosis of pituitary-dependent hyperadrenocorticism. The adenohypophyseal lesion was clearly visualized on both 3 T and 7 T magnetic resonance imaging (MRI) of the pituitary gland. Although biochemical and MRI findings were consistent with a functional pituitary microtumor, a pituitary lesion was not detected using (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET). This report firstly describes the application of high-resolution FDG-PET to a spontaneous pituitary microtumor in a dog.

High resolution pituitary gland MRI at 7.0 tesla: a clinical evaluation in Cushing's disease

Objective

To evaluate the detection of pituitary lesions at 7.0 T compared to 1.5 T MRI in 16 patients with clinically and biochemically proven Cushing’s disease.

Methods

In seven patients, no lesion was detected on the initial 1.5 T MRI, and in nine patients it was uncertain whether there was a lesion. Firstly, two readers assessed both 1.5 T and 7.0 T MRI examinations unpaired in a random order for the presence of lesions. Consensus reading with a third neuroradiologist was used to define final lesions in all MRIs. Secondly, surgical outcome was evaluated. A comparison was made between the lesions visualized with MRI and the lesions found during surgery in 9/16 patients.

Results

The interobserver agreement for lesion detection was good at 1.5 T MRI (κ = 0.69) and 7.0 T MRI (κ = 0.62). In five patients, both the 1.5 T and 7.0 T MRI enabled visualization of a lesion on the correct side of the pituitary gland. In three patients, 7.0 T MRI detected a lesion on the correct side of the pituitary gland, while no lesion was visible at 1.5 T MRI.

Conclusion

The interobserver agreement of image assessment for 7.0 T MRI in patients with Cushing’s disease was good, and lesions were detected more accurately with 7.0 T MRI.

Key Points

• Interobserver agreement for lesion detection on 1.5 T MRI was good;

• Interobserver agreement for lesion detection on 7.0 T MRI was good;

• 7.0 T enabled confirmation of unclear lesions at 1.5 T;

• 7.0 T enabled visualization of lesions not visible at 1.5 T.

Electronic supplementary material

The online version of this article (doi:10.1007/s00330-015-3809-x) contains supplementary material, which is available to authorized users.

Diagnosis of Cushing's disease

Diagnosis of Cushing's disease frequently remains a challenge. In this review we critically appraise the clinical features, biochemical tests, and imaging modalities used for this purpose. We outline recommendations for approaches to clinical investigation, with a particular focus on developments made within the last two years.

Different imaging characteristics of concurrent pituitary adenomas in a patient with Cushing's disease

We report a patient with Cushing's disease (CD) and two pituitary adenomas that demonstrated different imaging characteristics and therefore suggest an alternative imaging strategy for these patients. A 42-year-old woman presented with signs and symptoms of CD. Biochemical evaluation confirmed hypercortisolemia and suggested CD. On pituitary MRI with spoiled gradient recalled acquisition in the steady-state and T1-weighted spin echo protocols, a 5mm hypoenhancing region typical for a pituitary adenoma was identified on the left. However, after surgical resection the patient remained hypercortisolemic and pathology revealed a non-functional adenoma. At early repeat surgical exploration a 10mm adenoma was found in the right side of the gland. Postoperatively the patient became hypocortisolemic and pathology demonstrated an adrenocorticotropic hormone (ACTH)-staining adenoma. On review of the initial MRI this tumor corresponded to a region of contrast retention best visualized on delayed fluid attenuated inversion recovery (FLAIR) imaging. While the incidentaloma in this case demonstrated classical imaging characteristics of a pituitary adenoma the larger ACTH-secreting tumor was best appreciated by contrast retention. This suggests a role for delayed postcontrast FLAIR imaging in the preoperative evaluation of CD. ACTH-secreting tumors causing CD cause significant morbidity. Due to their small size, a pituitary adenoma is frequently not identified on imaging despite endocrinologic testing suggesting CD. Regardless of improvements in MRI, many tumors are only identified at surgical exploration.

The diagnostic value of fused positron emission tomography/computed tomography in the localization of adrenocorticotropin-secreting pituitary adenoma in Cushing's disease

Despite the high resolution of magnetic resonance imaging (MRI) of the pituitary gland, up to 40% of cases of Cushing's disease (CD) have normal MRI. Fused images of positron emission tomography and computed tomography (PET-CT) may have a potential diagnostic role in CD in general and in such cases in particular. Objective of this study is to explore the diagnostic potential of PET-CT for localization of adrenocorticotropin-secreting pituitary adenomas in CD. PET-CT was performed in 12 cases with de novo (7 cases) or persistent CD (5 cases) that were proven to have CD on biochemical, radiological and/or histopathological findings. These cases had a definite CD confirmed on histopathological and immunostaining examination of the subsequent transphenoidal surgical specimens (10 cases) and/or bilateral inferior petrosal sinus sampling (IPSS, 4 cases). PET-CT was positive in 7 of the 12 cases of CD (58%) showing a focal area of uptake in the pituitary gland. In these seven cases, MRI was positive in six (85.7%) but negative in one case (14.3%). In the other five cases with negative PET-CT, MRI was positive in two and negative in three cases. Of four cases with negative MRI, PET-CT was positive in one case (25%). We conclude that PET-CT is positive in around 60% of the cases of CD. Although the majority of cases with positive PET-CT had positive MRI, PET-CT may detect some cases with negative MRI and thus provides important diagnostic information. If these findings are confirmed in larger studies, PET-CT might become an important diagnostic technique, especially when the more invasive and technically demanding procedure of IPSS is not available or inconclusive.

Management of Cushing's disease using cavernous sinus sampling: effectiveness in tumor lateralization

OBJECTIVE

The aim of this study was to determine the accuracy of bilateral cavernous sinus sampling (CSS) in preoperative tumor lateralization (right/left) within the pituitary in patients with Cushing's disease (CD).

PATIENTS AND METHODS

The study consisted of 26 consecutive patients who had undergone CSS followed by transsphenoidal surgery (TS) for CD between 2000 and 2006 at our institution. The magnetic resonance imaging (MRI) of the selected patients either revealed a normal pituitary or a lesion <or=6mm within the gland. Simultaneous bilateral CSS with corticotropin releasing hormone (CRH) stimulation were performed in all cases and the data was analyzed in relation to the results of the MRI studies, intraoperative and pathological findings and the outcome.

RESULTS

Early remission was achieved in 23 patients (88%) and CSS predicted the correct localization of the adenoma in 22 patients (85%). No lateralization (elevated levels in both sides) was detected during CSS in two patients, due to lesions within the central part of the pituitary. In four cases, there was a false positive lateralization, in which no microadenoma could be located in the lateralized side of the pituitary, resulting in no remission. There were no complications related to the CSS.

CONCLUSION

CSS in CD seems to be a valuable and safe diagnostic tool, which can predict the correct location of the pituitary adenoma in 85% of the cases.

Evaluation and management of Cushing syndrome in cases of negative sellar magnetic resonance imaging

✓ The treatment of patients with Cushing disease and without magnetic resonance (MR) imaging evidence of Cushing disease (that is, negative MR imaging) is discussed in this paper. Magnetic resonance imaging is the diagnostic modality of choice in Cushing disease, but in up to 40% of these patients negative imaging can be caused by tumor-related factors and limitations in imaging techniques. In cases in which the MR imaging is negative, it is critical to make sure that the diagnosis of Cushing disease is correct. This can be accomplished by performing a complete laboratory and imaging workup, including dexamethasone suppression tests, imaging of the adrenal glands, and inferior petrosal sinus sampling when appropriate. If these evaluations suggest a pituitary source of the hypercortisolemia, then transsphenoidal surgery remains the treatment of choice. The authors favor the endoscopic approach because it gives a wider and more magnified view of the sella and allows inspection of the medial cavernous sinus walls. Radiosurgery is an effective treatment option in patients with persistent Cushing disease. When a target cannot be found on MR imaging, one can target the entire sellar region with radiosurgery.

Surgical management of pediatric Cushing's disease

BACKGROUND

Cushing's disease may have a direct effect on growth pattern, pubertal maturation, and long-term survival in pediatric patients.

METHODS

Dexamethasone suppression test was done in 10 children (median age, 15 years) and showed variable suppressibility, with microadenoma seen in 5, macroadenoma in 3, and normal gland in 2 patients. Inferior petrosal sinus sampling (IPPS) was also carried out and confirmed pituitary adenoma as source of ACTH in 2 patients. We adopted sublabial transsphenoidal (n = 9) or pterional transsylvian route (n = 1) in macroadenoma with conchal sphenoid sinus. Serum cortisol level <50 nmol/L was taken as the criteria for biochemical remission.

RESULTS

Clinical remission was achieved in 7 of 10 operated patients. In 2 patients where clinical remission was achieved, postoperative BSC could not be done. Postoperative BSC was less than 50 nmol/L in 2 (25%) of 8 patients and remained elevated in 6. Remission was achieved in both patients with postoperative BSC less than 50 nmol/L and in 3 of 6 with elevated levels. Three patients had neither clinical nor biochemical remission: 2 underwent bilateral adrenalectomy and 1 received radiotherapy. Postoperative CSF leak seen even in microadenomas associated with arachnoidal prolapse. Among 7 patients who initially remitted (median follow-up of 82 months; range, 24-120 months), recurrence of disease occurred in 3 (42.8%) patients after a median interval of 5 years.

CONCLUSIONS

In children with CD, endocrinal manifestations are more frequent than visual symptoms. Transsphenoidal route is the preferred approach, but a nonpneumatised sphenoid sinus may be present. Sellar arachnoidal prolapse may cause postoperative CSF leak even in microadenomas. Surgery is the first line of treatment, but constant monitoring is mandatory to pick up the relapsed cases.

Thin-slice three-dimensional gradient-echo magnetic resonance imaging of the pituitary gland in healthy dogs

OBJECTIVE

To evaluate thin-slice 3-dimensional gradient-echo (GE) magnetic resonance imaging (MRI) of the pituitary gland in healthy dogs.

ANIMALS

11 healthy dogs.

PROCEDURES

By use of a 0.2-Tesla open magnet, MRI of the skull was performed with T1-weighted GE sequences and various protocols with variations in imaging plane, slice thickness, and flip angle before and after administration of contrast medium; multiplanar reconstructions were made. The pituitary region was subjectively assessed, and its dimensions were measured. Image quality was determined by calculation of contrast-to-noise and signal-to-noise ratios.

RESULTS

Best-detailed images were obtained with a T1-weighted GE sequence with 1-mm slice thickness and 30 degrees flip angle before and after administration of contrast medium. Images with flip angles > 50 degrees were of poor quality. Quality of multiplanar reconstruction images with 1-mm slices was better than with 2-mm slices. The bright signal was best seen without contrast medium. With contrast medium, the dorsal border of the pituitary gland was clearly delineated, but lateral borders were more difficult to discern.

CONCLUSIONS AND CLINICAL RELEVANCE

MRI of the canine pituitary gland with a 0.2-Tesla open magnet should include a T1-weighted GE sequence with 1-mm slice thickness and flip angle of 30 degrees before and after administration of contrast medium. The neurohypophysis was best visualized without contrast medium. The MRI examination permitted differentiation between the pituitary gland and surrounding structures.

Bilateral inferior petrosal sinuses sampling in the routine investigation of Cushing's syndrome: a comparison with MRI

OBJECTIVE

Identifying the cause of Cushing's syndrome (CS) is a perplexing issue. Bilateral inferior petrosal sinuses sampling (BIPSS) is an invasive and elaborate but established procedure in distinguishing Cushing's disease (CD) from ectopic adrenocorticotropic hormone (ACTH) syndrome. We compare the diagnostic performance of BIPSS and MRI in detecting an ACTH-secreting source, and we suggest the diagnostic protocol that we found beneficial for the management of patients with CS.

MATERIALS AND METHODS

Seventy-eight consecutive patients with CS were included. All patients underwent biochemical investigation and pituitary MRI. Consequently, patients were routinely referred for BIPSS; 25 received stimulation with corticotropin-releasing hormone (CRH) and 53 with CRH and desmopressin. The diagnosis of CD was established on the basis of complementary biochemical, imaging, and BIPSS criteria. The diagnostic performances of BIPSS and MRI were calculated for patients with final diagnosis.

RESULTS

A final diagnosis was available for 54 patients (46 CD confirmed, five ectopic confirmed, three adrenals). No (known) patient was misclassified based on our suggested diagnostic criteria. MRI rendered 25 false-negatives and two false-positives (incidentalomas). Successful BIPSS yielded two false-negatives and three false-positives (adrenals). The calculated accuracy for detecting a pituitary source of ACTH was 50% and 88% for MRI and successful BIPSS, respectively.

CONCLUSION

MRI is of only limited diagnostic performance, while BIPSS is the most accurate way to establish the diagnosis of CD. The routine use of a multimodality diagnostic approach including BIPSS, MRI, and biochemical tests is suggested to avoid the risk of mismanagement for patients with CS.

[The role of surgery in the treatment of prolactinomas]

TECHNIQUE

Almost all prolactinomas are operated through a transsphenoidal route, even in case of significant suprasellar extension or intracavernous invasion. Since 1996, we use the only endonasal route which is easier, quicker, less haemorrhagic and less aggressive than the sublabial one. If the removal of a large macroadenoma cannot be completed (50-70% of cases), a second procedure, usually transsphenoidal, is performed a few weeks later.

INDICATIONS

Microprolactinomas: usually surgery is proposed as soon as medical treatment is not well tolerated or if the patient wishes to be pregnant. Macroprolactinomas: bromocriptine or quinagolide are sometimes prescribed in a first stage. Surgery beeing indicated in case of inefficacy or intolerance of the medical treatment, or in emergency due to an acute visual pathways compression (tumoral necrosis). Giant adenomas (= 30-40 mm): usually dopaminergic agonists allow a tumoral volume reduction and assure a limitation of visual risks due to rapid decompression of visual pathways. Exceptionally, medical treatment leads to a complete regression of the adenoma.

RESULTS

Morbidity of transsphenoidal procedures: insipidus diabetes: transient 5-15%, definitive: 1-2%; septal perforation: 3-5%; rhinorrhea: 5%; visual aggravation: 2%. The most frequent complaint for patients operated through sublabial route is gum and dental pain, non-existent with endonasal procedures. Operative mortality: 0-1.7% (0% in our series). In men, normalization of prolactinemia is linked to the tumoral volume: 90-100% in case of microprolactinoma, 30-35% for enclosed macroprolactinomas, 0-5% for invasive macroprolactinomas. Conventional, conformational or stereotactic radiotherapy can be useful in case of contraindication to surgery and failure of medical treatment.

Undetectable postoperative cortisol does not always predict long-term remission in Cushing's disease: a single centre audit

OBJECTIVE

An undetectable postoperative serum cortisol has been regarded as a definition of cure in Cushing's disease. However, we noted disease recurrence amongst patients with Cushing's disease despite undetectable postoperative cortisol levels, and this led us to audit our data. We have also previously assessed surgical outcome for acromegaly and microprolactinoma for a single surgeon. The aims of this study were two-fold: (i) to investigate the treatment and surgical outcome of patients with Cushing's disease. In particular, we wished to compare the data with outcome for other pituitary tumours in our centre; and (ii) to determine whether undetectable cortisol following surgery is predictive of long-term cure for Cushing's disease.

PATIENTS AND METHODS

We performed a retrospective audit of 97 patients; mean age 39.1 (range: 14-82) years, 78/97 (80.4%) female, mean follow-up 92 months (range: 6 months to 29 years), with Cushing's disease seen in our unit between 1969 and 1998. We documented diagnostic investigation, immediate surgical outcome and disease recurrence in these patients.

RESULTS

All patients had elevated urinary free cortisol (mean 1270.6 nmol/l, range: 327-3245 nmol/l). In total, 95.5% of patients did not suppress with low-dose dexamethasone suppression testing. Hypokalaemia (K < 3.2 mmol/l) was present in 15.6% of patients; 17.5% of patients did not show cortisol suppression with high-dose dexamethasone and 15.8% of patients did not show an ACTH rise of > 50% following corticotrophic releasing hormone (CRH) administration. There was no significant (> 3) gradient in ACTH or cortisol following CRH during inferior petrosal sinus sampling in 27.3% of patients who had the test. A pituitary tumour was demonstrated on imaging in 55.8% of patients; 10.3% were macroadenomas. Mortality rate following trans-sphenoidal surgery was 1%. Following surgery, the immediate postoperative remission rate (undetectable postoperative cortisol) was 68.5%. However, 11.5% of these patients developed disease recurrence during a mean follow-up period of 36.3 months. Considering microadenomas, Cushing's disease patients had an immediate postoperative remission rate of 63.2% which is significantly lower (P < 0.05) compared to a remission rate of 91.1% in acromegaly. Additionally, new postoperative gonadotrophin deficiency (13.9%) and TSH deficiency (25.8%) was higher in patients with Cushing's disease compared to patients with acromegaly or microprolactinoma. Immediate postoperative remission rates improved from 50% in the first decade of a surgeon's career to consistently above 60% in the second and third decades, demonstrating a trend which may be attributed to surgical experience.

CONCLUSIONS

(i) Despite strict criteria for immediate postoperative remission and recurrence, undetectable postoperative cortisol is not always predictive of long-term remission. (ii) Despite an aggressive surgical approach, immediate postoperative remission rates for Cushing's disease are lower compared to other microadenomas. The development of new pituitary hormonal deficiency following surgery is also commoner than that seen amongst other microadenomas. These data have important implications for the follow-up of patients with Cushing's disease.

Microadenomas hipofisários: revisão de 95 casos

Procedemos a uma revisão de 95 casos de microadenomas hipofisários, evidenciados por ressonância magnética, nas instituições: Hospital Santa Cruz/Beneficência Portuguesa de Niterói e Clínica X-Labs/Rio de Janeiro. O objetivo foi verificar o tipo principal, incidência, proximidade à haste hipofisária, correlacionando-os com dados clínico-laboratoriais. Os equipamentos utilizados foram de 0,5 Tesla (Gyroscan T5 III da Philips e Vectra da GE) e 1,0 Tesla (Signa da GE), sendo realizadas seqüências rápidas, antes e após administração venosa do meio de contraste paramagnético (gadolínio). Predominaram pacientes do sexo feminino, com prolactinomas, sendo as queixas mais freqüentes: galactorréia, amenorréia e hiperprolactinemia. Em contraste à literatura corrente, observamos que mais freqüentemente a haste hipofisária encontrava-se centrada. Na detecção dos microadenomas é fundamental a injeção venosa do gadolínio o mais próximo possível da aquisição das imagens, sendo recomendável utilizar metade da dose do meio de contraste.

Analysis of indirect signs of microprolactinoma at MR imaging

OBJECTIVE

To evaluate the diagnostic reliability/value of microprolactinoma indirect signs at MRI.

METHODS AND MATERIAL

A prospective study was carried out over 3 years on 26 women with microprolactinoma (MiP group) and 106 healthy female volunteers as a control group. Size, glandular morphology, pituitary stalk inclination and sellar bony floor erosion were measured and a comparative statistical analysis between both groups was performed.

RESULTS

Patients from the MiP group showed a significantly bigger glandular size than women in the control group, although the glandular morphology did not present significant differences between both groups. Only 5% of normal glands measured over 7.5 mm in height and none of them reached 9 mm, while up to 42.3% of the MiP group scored over 7.5 mm and 19.2% over 9 mm. Mean stalk inclination for the MiP group was 4.6 +/- 3.1 degrees and 3.5 +/- 2.7 degrees for the control group with no significant differences. Five microprolactinomas were located on the glandular midline, 11 on the left side and ten on the right side. No relationship between the microadenoma location inside the gland and stalk inclination was found. From 21 microprolactinomas with eccentric location, 17 coincided with the sellar floor excavation; eccentric excavation presented significant differences between both groups, but not the central excavation.

CONCLUSION

From all indirect sings of microprolactinoma analyzed in this study, only a gland height over 9 mm, and an eccentric sellar excavation of at least 3 mm are reliable signs to support its diagnosis.

The continuous 7-hour intravenous dexamethasone suppression test in the differential diagnosis of ACTH-dependent Cushing's syndrome

OBJECTIVE

A recent report showing disappointingly low sensitivity and specificity for the oral high dose dexamethasone test in the differential diagnosis of Cushing's syndrome prompted us to re-evaluate the results obtained in our centre using the continuous 7-hour intravenous dexamethasone suppression test for this purpose.

PATIENTS

105 patients with ACTH-dependent Cushing's syndrome were included in this study; 78 with Cushing's disease, 8 with ectopic ACTH-secreting tumours and 19 were classified as 'of unknown aetiology'.

RESULTS

In 74/78 (94.9%) of patients with Cushing's disease and in 3/8 (37.5%) patients with the ectopic ACTH syndrome, a plasma cortisol decrease > 190 nmol/l at 7 h as compared to baseline values was achieved in the continuous 7-hour intravenous dexamethasone suppression test. Using a plasma cortisol decrease > 190 nmol/l at 7 h as compared to baseline values as the cut-off value, the sensitivity and specificity of the continuous 7-hour intravenous dexamethasone suppression test for the diagnosis of Cushing's disease in patients with ACTH-dependent Cushing's syndrome were 94.9% and 62.5%, respectively.

CONCLUSIONS

In patients with ACTH-dependent Cushing's syndrome with a plasma cortisol decrease > 190 nmol/l at 7 h in the continuous 7-hour intravenous dexamethasone suppression test, additional localizing investigations such as bilateral simultaneous inferior petrosal sinus sampling and/or pentetreotide scintigraphy should be performed when no clearly discernible pituitary adenoma is observed on MRI studies. Patients with ACTH-dependent Cushing's syndrome with a plasma cortisol decrease < 190 nmol/l at 7 h in the continuous 7-hour intravenous dexamethasone suppression test should also undergo bilateral simultaneous inferior petrosal sinus sampling and/or pentetreotide scintigraphy to demonstrate the presence of a nonpituitary source of ACTH overproduction.

Cavernous sinus sampling is highly accurate in distinguishing Cushing's disease from the ectopic adrenocorticotropin syndrome and in predicting intrapituitary tumor location

Inferior petrosal sinus sampling (IPSS) is used to distinguish pituitary Cushing's disease from occult cases of the ectopic ACTH syndrome, but is limited in that it requires the use of ovine CRH (oCRH) and is not highly accurate at predicting the intrapituitary location of tumors. This study was designed to determine whether cavernous sinus sampling (CSS) is as safe and accurate as IPSS, whether CSS can eliminate the need for oCRH stimulation, and whether CSS can accurately predict the intrapituitary location of tumors. Ninety-three consecutive patients with ACTH-dependent Cushing's syndrome were prospectively studied with bilateral, simultaneous CSS before and after oCRH stimulation. Prediction of a pituitary or ectopic ACTH source was based on cavernous/peripheral plasma ACTH ratios. Intrapituitary tumor location was predicted based on lateralization (side to side) ACTH ratios. These predictions were compared to surgical outcome in the 70 patients who had surgically proven pituitary (n = 65) or ectopic (n = 5) disease. CSS distinguished pituitary Cushing's disease from the ectopic ACTH syndrome in 93% of patients with proven tumors before oCRH administration and in 100% of patients with proven tumors after oCRH. It was as safe and efficacious as published IPSS results. CSS accurately predicted the intrapituitary lateralization of the tumor in 83% of all patients and 89% of those patients with good catheter position and symmetric venous flow. CSS is as safe and accurate as IPSS for distinguishing patients with pituitary Cushing's disease from those with the ectopic ACTH syndrome. In addition, CSS appears to be superior to IPSS for predicting intrapituitary tumor lateralization.

Comparative evaluation of conventional and dynamic magnetic resonance imaging of the pituitary gland for the diagnosis of Cushing's disease

OBJECTIVES

The ability of MRI to detect pituitary ACTH-secreting adenomas in patients with Cushing's disease is limited. Owing to different dynamics of contrast enhancement between adenomas and normal pituitary tissue, it has been suggested that obtaining images within seconds after gadolinium (Gad) injection using dynamic procedures increases the sensitivity of MRI in the detection of pituitary microadenomas. The objective of this study was to compare the ability of conventional magnetic resonance imaging (CMRI) and dynamic MRI (DMRI) to detect ACTH-secreting pituitary adenomas.

DESIGN

Twenty-six consecutive patients with ACTH-dependent Cushing's syndrome and 10 normal subjects were investigated. According to the results of inferior petrosal sinus sampling, 21 patients had Cushing's disease and five had ectopic ACTH syndrome. Patients with Cushing's disease were operated regardless of the results of imaging studies. All underwent identical MRI and DMRI procedures using a 1.0 T magnet. Image sampling time during DMRI was 19 sec. Scans were randomly mixed and analysed blind, retrospectively and independently by two experienced radiologists. The clarity of the images was assessed by the analysis of agreement among radiologists. MRI findings were compared to surgical and histopathological findings.

RESULTS

Surgical exploration identified three macrodenomas and 14 microadenomas. One microadenoma was found at pathological examination after subtotal hypophysectomy and no tumour was found in three cases. According to the combined opinion of radiologists, the three macroadenomas were identified equally well with CMRI and DMRI. Eight ACTH-secreting microadenomas were detected with CMRI and 11 with DMRI. The three microadenomas detected with DMRI only were visualized within 60 sec following Gad injection. No false positives occurred with CMRI. Three false positives were obtained with DMRI: one in a patient with ectopic ACTH syndrome while a silent microprolactinoma and normal tissue were found at the site of the radiological abnormality in two patients with Cushing's disease. In our study, the sensitivity of DMRI is greater than that of CMRI (0.67 vs. 0.52) but is associated with a loss in specificity (0.80 vs. 1.00). False positives may result from the increased sensitivity of DMRI which detects incidental pituitary lesions, technical artefacts or lowest clarity of images, as suggested by a lower observer agreement of DMRI (Kappa statistic 0.66 vs. 0.83). Overall, the two MR procedures had equivalent diagnostic power (0.72).

CONCLUSIONS

In our hands, dynamic procedures did not improve the usefulness of MRI in Cushing's syndrome.

Effectiveness versus efficacy: the limited value in clinical practice of high dose dexamethasone suppression testing in the differential diagnosis of adrenocorticotropin-dependent Cushing's syndrome

High dose dexamethasone suppression testing has been widely employed in the differentiation between pituitary ACTH-dependent hypercortisolism [Cushing's disease (CD)] and the ectopic ACTH syndrome. We hypothesized that the high dose dexamethasone suppression test as it is performed in practice does not improve the ability to differentiate between these two types of ACTH-dependent Cushing's syndrome. Cases were drawn from 112 consecutive patients with ACTH-dependent Cushing's syndrome, who were then classified based upon results of inferior petrosal sinus sampling for ACTH levels. Analysis of test characteristics of high dose dexamethasone suppression testing was performed in the 73 patients for whom results are available. Statistical modeling was performed using the 68 cases with complete data on all assessed variables. Logistic regression models were used to predict the probability of pituitary-dependent Cushing's syndrome (CD) given the results of high dose dexamethasone suppression testing before and after adjustment for the contribution of a series of potential covariates. Of the 112 patients with ACTH-dependent Cushing's syndrome, 15.2% had the ectopic ACTH syndrome, and the remainder had pituitary-dependent Cushing's syndrome (CD). Patients with the ectopic ACTH syndrome were significantly older (mean, 51.9 vs. 40.2), were more likely to be male (58.8% vs. 27.4%), had shorter duration of clinical findings (mean, 11.6 vs. 39.9 months), were more likely to have hypokalemia (50% vs. 8.6%), had higher baseline 24-h urinary free cortisol [mean, 8317 vs. 1164 nmol/day (3015 vs. 422 microg)] and plasma ACTH levels [mean, 47 vs. 17 pmol/L (210 vs. 78 pg/mL)] and were less likely to suppress urinary free cortisol or plasma cortisol with high dose dexamethasone using the standard criterion of 50% or more suppression compared with patients with pituitary-dependent Cushing's syndrome. Based upon the standard criterion, the sensitivity and specificity of the high dose dexamethasone suppression test for the diagnosis of pituitary-dependent Cushing's syndrome were 81.0% and 66.7%, respectively. Although the mean percent suppression was significantly greater for patients with CD than for those with the ectopic ACTH syndrome (72.2% vs. 41.3%), the range of suppression was 0-99% for each diagnosis. The area under the receiver operating characteristic curve was 0.710 (95% confidence interval, 0.541-0.879). Logistic regression models were used to evaluate the probability of CD given the responsiveness to high dose dexamethasone suppression testing before and after adjustment for the potential contributions of other factors. A model including all of the variables (age, sex, duration, presence of hypokalemia, urinary free cortisol, and plasma ACTH) had a diagnostic accuracy of 92.7%. A model including all of these variables plus a binary variable indicating whether the patient met the criterion of suppression by 50% or more resulted in 95.6% accuracy, whereas substitution of this binary variable by percent suppression resulted in a model with 94.1% accuracy. There were no statistically significant differences among these models; their values for the c statistic, which is equivalent to the area under the curve in a receiver operating characteristic analysis, were all greater than 0.9. Logistic regression models indicate that the results of the dexamethasone suppression test add little to the differential diagnosis of ACTH-dependent Cushing's syndrome, especially after taking other clinical information into account. In our patient population, the sensitivity and specificity of the dexamethasone suppression test were less than those reported by others. However, because 20-33% of cases of ectopic ACTH syndrome are misdiagnosed with these logistic regression models, other techniques are necessary to achieve greater diagnostic accuracy.

Transsphenoidal surgery for pituitary tumours

OBJECTIVES

Transsphenoidal surgery (TSS) is the preferred method for the excision of pituitary microadenomas in adults. This study was carried out to establish the long term efficacy and safety of TSS in children.

STUDY DESIGN

A 14 year retrospective analysis was carried out on 23 children (16 boys and seven girls), all less than 18 years of age, who had undergone TSS at our centre.

RESULTS

Twenty nine transsphenoidal surgical procedures were carried out. The most common diagnosis was an adrenocorticotrophic hormone (ACTH) secreting adenoma (14 (61%) patients). The median length of follow up was 8.0 years (range 0.3-14.0 years). Eighteen (78%) patients were cured after the first procedure. No death was related to the operation. The most common postoperative complication was diabetes insipidus, which was transient in most patients. Other complications were headaches in two patients and cerebrospinal fluid leaks in two patients. De novo endocrine deficiencies after TSS in children were as follows: three (14%) patients developed panhypopituitarism, eight (73%) developed growth hormone insufficiency, three (14%) developed secondary hypothyroidism, and four (21%) developed gonadotrophin deficiency. Permanent ACTH deficiency occurred in five (24%) patients, though all patients received postoperative glucocorticoid treatment until dynamic pituitary tests were performed three months after TSS.

CONCLUSIONS

TSS in children is a safe and effective treatment for pituitary tumours, provided it is performed by surgeons with considerable experience and expertise. Surgical complications are minimal. Postoperative endocrine deficit is considerable, but is only permanent in a small proportion of patients.

Pituitary corticotroph macrotumors. Diagnosis and treatment

Pituitary corticotroph macrotumors occur in 10% to 50% of dogs with PDH. Clinical signs may be only those of hypercortisolism or may include neurologic signs such as stupor, inappetance, circling, or pacing. Currently, CT and MRI are the only tests that can confirm the presence of a pituitary macrotumor in these patients. Results of endocrine testing are not significantly different from those of dogs with a microtumor. When a macroscopic pituitary tumor is identified in a dog with neurologic signs, or if a larger tumor is found in a dog even in the absence of neurologic signs, radiation therapy is currently the treatment of choice. Unfortunately, success rates with treatment are variable. A better response may be seen if the tumor is smaller and neurologic signs are minimal or absent at the time of treatment.

Imaging of pituitary tumours

In the neuroradiological study of pituitary tumours, second generation CT, dynamic CT and MRI provide information about the extent of the tumour and its anatomical relations with the surrounding tissues. Sometimes these techniques can distinguish primary anterior pituitary lesions from primary parasellar lesions with presentations in the sellar region. In general, contrast-enhanced MRI and dynamic CT are more sensitive than conventional CT for the diagnosis of pituitary microadenomas, as well as for the precise delineation of the parasellar invasion of macroadenomas. Radiological techniques usually cannot distinguish clinically non-functioning from functioning pituitary adenomas. BSIPSS is used for confirmation of the diagnosis of Cushing's disease as well as for the lateralization of pituitary microadenomas in Cushing's disease and some other anterior pituitary hyperfunctional states. Neurotransmitter-receptor ligand imaging by SPECT with 123I-IBZM and/or 111In-DTPA-octreotide characterizes the dopamine D2 and somatostatin receptor status of pituitary adenomas, respectively. In selected cases, these techniques may be used for the differential diagnosis of pituitary tumours as well as for the differential diagnosis of primary anterior pituitary lesions and primary parasellar lesions with presentations in the sellar region. If medical therapy of these tumours with receptor agonists is being considered, these techniques can help in selecting the first-line treatment. Furthermore, the effects of medical therapy on the tumour can be evaluated. The introduction of newer and more receptor-specific radioligands may expand the clinical use of these techniques in the future. The availability of PET for the clinical diagnosis of pituitary tumours is still limited, but promising results have been described.