Inferior petrosal sinus sampling
Presentation:
ACTH dependent Cushing's syndrome and congestive cardiac failure. CT of the chest, abdomen and pelvis demonstrates no focal abnormality.
Patient Data:
Two 3 millimetre areas of delayed enhancement are seen in the pituitary gland, one on the right just posterior to the level of the stalk and the other more centrally at the same level. Whether both of these are functional microadenomas or whether one is non secretory is uncertain. Pituitary stalk is midline. Chiasm and cavernous sinuses are uninvolved, with normal cavernous carotid flow voids.
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Two possible microadenomas. One seen best on dynamic imaging (red arrow) is the more likely one. On delayed coronals another apparent region of hypo-enhancement (blue arrow) is seen, however as it neither seen on dynamic or sagittal imaging it is unlikely to be real.
Inferior petrosal sinus sampling
Bilateral groin punctures were performed and 5 french catheters passed up the IVC, through the right atrium and SVC into the internal jugulars to the base of skull. Injection of contrast retrogradely opacified the inferior petrosal sinuses which were entered with micro-catheters placed equidistant from the pituitary fossa, their position confirmed with further injections of contrast.
Following this simultaneous sampling of each microcatheter and the peripheral venous blood (via the groin sheath) was performed pre and post administration of CRH.
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The venous ACTH levels obtained from the right and left petrosal sinuses and peripheral blood are as follows (00:00 = baseline, other times are in minutes post CRH administration):
- 00:00 right perosal sinus 14.7
- 00:02 right perosal sinus 243
- 00:05 right perosal sinus 139
- 00:10 right perosal sinus 93.0
- 00:15 rigth perosal sinus 58.4
- 00:00 left perosal sinus 8.06
- 00:02 left perosal sinus 81.7
- 00:05 left perosal sinus 81.3
- 00:10 left perosal sinus 11.5
- 00:15 left perosal sinus 8.50
- 00:00 peripheral 1.40
- 00:02 peripheral 1.51
- 00:05 peripheral 1.43
- 00:10 peripheral 2.53
- 00:15 peripheral 3.29
These results are consistent with a pituitary microadenoma, most likely in the right side of the gland.
Case Discussion:
On the basis of the IPSS and MRI this patient went on to have an exploratory transphenoidal hypophysectomy. Although histological proof of a microadenoma was not achieved, the patient became biochemically normal following surgery and their ACTH levels returned to normal.
At 18 months follow up remains well with normal pituitary function.
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Case courtesy of A/Prof Peter Mitchell, Royal Melbourne Hospital
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