gms | German Medical Science

58. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e. V. (DGNC)

Deutsche Gesellschaft für Neurochirurgie (DGNC) e. V.

26. bis 29.04.2007, Leipzig

Inferior petrosal sinus sampling in the preoperative workup of ACTH-dependent Cushing's syndrome: Results of a retrospective analysis

Die bilaterale Katheterisierung des Sinus petrosus inferior für die präoperative Diagnostik des ACTH-abhängigen Cushing-Syndroms: Eine retrospektive Analyse

Meeting Abstract

  • corresponding author T. Knobloch - Klinik für Neurochirurgie, Universitätsklinikum Göttingen
  • R. Fahlbusch - Klinik für Neurochirurgie, Universität Erlangen-Nürnberg, Erlangen
  • W. J. Huk - Abteilung für Neuroradiologie, Universität Erlangen-Nürnberg, Erlangen
  • M. Buchfelder - Klinik für Neurochirurgie, Universität Erlangen-Nürnberg, Erlangen

Deutsche Gesellschaft für Neurochirurgie. 58. Jahrestagung der Deutschen Gesellschaft für Neurochirurgie e.V. (DGNC). Leipzig, 26.-29.04.2007. Düsseldorf: German Medical Science GMS Publishing House; 2007. DocDO.04.09

The electronic version of this article is the complete one and can be found online at:

Published: April 11, 2007

© 2007 Knobloch et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



Objective: To evaluate the diagnostic accuracy of inferior petrosal sinus sampling (IPSS) in the preoperative investigation of patients with ACTH-dependent Cushing's syndrome (CS) in order to confirm the diagnosis and the lateralization of a pituitary microadenoma.

Methods: We retrospectively evaluated the diagnostic accuracy of basal and poststimulated (CRH) IPSS in distinguishing pituitary from ectopic ACTH secretion in 100 cases of Cushing's syndrome,consisting of 97 patients with Cushing's disease (CD) and 3 with ectopic ACTH secretion (EAS). A maximal ratio of inferior petrosal sinus : periphery (IPS:P) ratio >2 before or >3 after stimulation indicated CD. The preoperative lateralization of microadenomas using the intersinus-ratio was also assessed and a clear cut 1,4 gradient was expected in lateral tumors. However, in midline adenomas, the gradient was expected to be less than 1,4. Verification of the diagnosis, localization and extent of the adenomas was made by positive immunohistochemistry and surgical success.

Results: An IPS:P ratio >2 in basal samples identified 76 of the 97 patients with CD (sensitivity 78,3%). A stimulated IPS:P ratio >3 identified 79 patients with CD (sensitivity 82,3%). The sensitivity of both ratios (basal >2 and / or stimulated >3) was 87,6%. No patient with EAS had a basal IPS:P ratio >2 or a stimulated ratio >3 (specifity 100%). The sensitivity rose from 87,6 to 95,7% in patients with proven CD and bilateral excellent catheter positions. The IPS:P ratio suggested by receiver-operator characteristic (ROC) analysis that better distinguished CD from EAS was 2,14 for the basal and / or 1,54 for the stimulated ratios. Using these cutoffs in patients with bilateral excellent catheter placement, the sensitivity rose to 100%. IPSS was less reliable in predicting lateralization of microadenomas. Surprisingly, the intersinus-ratio correctly identified the adenoma site found at surgery in only 47,6% (basal) and 44,4% (stimulated), respectively.

Conclusions: In conclusion, IPSS improved the diagnostic workup in patients with ACTH-dependent Cushing's syndrome, especially in cases with inconclusive results of dynamic testing and negative MRI of the sellar region. More striking results were obtained with bilateral excellent catheter position and when a >2,14 basal and / or a >1,54 stimulated IPS:P ratio were considered as diagnostic cutoffs. The poor prediction of the side of adenoma location suggests performance of a careful pituitary gland exploration irrespective of IPSS results before performing a hemihypophysectomy.