Approach Considerations
Individual centers have their own protocols and preferences for catheters and guidewires for performing inferior petrosal sinus sampling (IPSS). The technique described below is the one detailed by Prabhu et al. [3]
Inferior Petrosal Sinus Sampling
The patient is placed supine on the fluoroscopy table in the interventional radiology suite and given intravenous sedation.
Both groins are prepared with antiseptic solutions and draped with sterile drapes.
A urinary catheter may be introduced, as the procedure may last for approximately 90 minutes.
Using the Seldinger technique, two 7F and 6F sheaths are introduced into the right and left femoral veins.
Either 5000 IU of heparin is injected intravenously as a bolus or a heparin drip for the entire duration of the procedure is started, per the interventional radiologist’s preference.
Under fluoroscopic guidance, a 5F multipurpose catheter and straight Terumo guidewire (Terumo Corporation, Tokyo) are threaded through the right atrium, through the superior vena cava, and into the left brachiocephalic vein. One wire is advanced in to the right and the other into the left IJV. Slight difficulty may be encountered while entering the left IJV, as there is a valve at the junction of the left IJV and left subclavian vein. Prabhu et al recommend gentle probing while advancing into the left IJV during deep inspiration as the valve opens during this time. In some cases, it may be necessary to give the patient a head low position to distend the IJV, facilitating visualization and catheterization. Rarely, if all other methods fail, the IJV may be directly punctured with ultrasound guidance. [3]
Once the IJV is entered, the multipurpose catheters are replaced with 5.5 H1 Headhunter catheters, which act as guiding catheters for the microcatheter-microwire combination to enter the IPS. Another IU of heparin is given intravenously unless continuous heparin perfusion has already been initiated.
The interventional radiologist must have thorough anatomical knowledge of the inferior petrosal venous drainage and its anatomical variations and should be able to identify hypoplastic sinus or multiple small channels instead of a single inferior petrosal vein.
The procedure may have to be abandoned in rare cases if the inferior petrosal vein drains into the condylar vein and has no communication with the internal jugular.
Lateral and anteroposterior views may be acquired at this stage to mark the ostium of the IPS.
A Tracker 10 or Tracker 18 microcatheter (Target Therapeutics, Freemont, CA) with a Seeker 10 or Seeker 16 wire (Target Therapeutics, Freemont, CA) is introduced through the diagnostic catheter, which is gently manipulated to point anterolaterally 1 cm or so below the superior jugular bulb until the IPS is entered.
The diagnostic catheter should never be pushed into the sinus and should be allowed to rest at the ostium.
After entering the sinus, the microwire is removed and diagnostic venography performed to check the position of the microcatheter tip. Venography opacifies the ipsilateral IPS, superior petrosal sinus, cavernous sinus, and contralateral IPS. Sluggish flow of contrast indicates a hypoplastic sinus. Based on the initial venogram, the contralateral wire and catheter can be placed.
Sampling is started after confirming the position of the microcatheter and positioning it well in the IPS.
Before each sample is drawn, the catheters are aspirated, saline-diluted blood discarded, and the position of the catheters confirmed.
Samples are drawn simultaneously from the IPS and the peripheral veins for plasma ACTH 5 minutes and 1 minute before administration of oCRH. One µg/kg to a maximum of 100 µg of oCRH is given intravenously in a peripheral vein, and samples for plasma ACTH are collected at 2, 5, and 10 minutes after administration. A peripheral sample for plasma cortisol is also taken along with each sample of ACTH.
Blood samples are immediately placed in specially labeled EDTA-containing tubes and placed on ice. Centrifugation and plasma decantation of the sample should be performed within one hour and samples analyzed immediately or frozen until ACTH assay.
The patient should be monitored for slurred speech, hemifacial paraesthesia, sensation of enlarged tongue, perioral tingling, and labile hypertension, any of which could indicate brainstem ischemia. The procedure is terminated immediately if any of these signs appear.
When aberrant anatomy or inferior vena cava filter or thrombosis prevents BIPSS via a femoral approach, direct IJV access may be obtained. If there is no anastomosis between IJV and IPS, the catheters are placed at the C1-2 level for sampling. However, sampling at this level may be associated with false results due to transverse or sigmoid sinus contamination.
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Inferior Petrosal Sinus Anatomy
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IPS variant type 1
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IPS variant type 2
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IPS variant type 3
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IPS variant type 4
