Inferior Petrosal Sinus Sampling or IPSS is sometimes used to pinpoint where the source of Cushing’s is coming from, generally when it’s highly suspected to be a tumour on the pituitary gland. I was ‘lucky’ enough to have one of these a couple of days ago as my MRI for my pituitary came back clean but my CRH test strongly indicated a pituitary tumour, plus I have ACTH dependant Cushing’s which is caused by a pituitary tumour in 85% of cases. I read around a lot beforehand but everything is just an overview of the procedure so I wanted to post about the experience from a patient’s perspective to give other people an idea of what to expect.
First up I’ll give you the technical part. I believe it can be done on just one side but in my case was done on both at once, so I had a bilateral IPSS. It’s a day procedure where you are awake (though some people have been sedated or even put under general anaesthetic for it) and barring complications will be free to go home a few hours afterwards. The idea is catheters are inserted into your groin and snaked up to the pituitary gland. A synthetic hormone, CRH, is then injected and blood samples are taken over a 10 – 15 minute period from both the catheters and also your arm. From what I understand the increase in ACTH in a sample can then indicate if you have a pituitary tumour and also, in the case of bilateral IPSS, the side of the gland it is on. It sounds horrendous when put like that but I have to say that it really isn’t so bad (not that I would choose to repeat it of course).
The process requires a good team of mixed specialists. In with me I had 10 people and they all introduced themselves but as I was quite terrified I didn’t pay full attention to who was who. I know I had my 2 endocrine nurses, 1 neuroradiologist, 1 neurological doctor and then a bunch of others in with me; I think possibly 2 ‘normal’ nurses, 2 radiologists and possibly ‘normal’ doctors as well. It was done in something called the angiography suite in my hospital as it requires x-rays to guide the catheters into place.
You’re laid flat on your back on the x-ray table and hooked up to monitors. O2, heart rate and blood pressure were monitored throughout. It’s a little unnerving to hear your heart rate beeping constantly because when it does skip a beat or speed up a little you instantly panic which makes it worse! There was also a huge screen on one side of me that the x-ray pictures were coming up on. Unfortunately they had to take my glasses off and I’m basically blind without them so I couldn’t sneak a look out of the corner of my eye or I’d have been interested to watch that bit. There was also a small x-ray plate at the side of my head and one large one above me that would move over my chest and head as needed. At times this did come very close to me so it may not be great if you are claustrophobic although it isn’t enclosed at all.
Once these bits were in place and everyone was introduced the first step was cleaning me. You have to be completely naked under your gown for this as the catheters are inserted into the veins where your legs meet your abdomen. Iodine was used to clean which is cold and if it dribbles into more sensitive areas it stings for a minute or two! Once this is done you’ll get a shot of local anaesthetic into the area the cannula is going to be placed. This is probably the most painful part of the procedure as it does sting for a minute or two before it numbs you but it’s not too bad, if you’ve had a local before it’s just the same as any other. You shouldn’t really feel the cannula go in then either although I did slightly on my left side; it was a brief pain but again nothing terrible. You’ll also have a cannula put in your arm; mine had already been put in earlier in the day as I’d had to go for some last minute blood tests anyway.
This is the weirdest part of the procedure and is not exactly pleasant but wasn’t painful. The catheters are inserted via the groin cannulas and the x-ray plates are used to guide them to the correct position right by your pituitary gland. I could kind of track where they were based on the x-ray plate position above me as it would move when the neurologist needed to see further up my body. He had trouble with my left one as it moved from chest to head back to chest about 3 or 4 times with that one.
I couldn’t feel a thing until they reached my neck. Once there I could feel it and the only way I can describe how it felt was the way I imagine it feels when you see something in a horror movie infecting someone. You know when you get all those dark veins that look to be bulging a bit as they spread throughout the victim? Like that. A definite sense that something was there but no pain. It’s once it reaches your head it’s most uncomfortable. Whenever it was moving I’d get some slight headache-like pressure in my forehead and a little in the back of my neck. I could also hear a sort of crackling; I assume it’s from whatever they use to control the catheter (radio-controlled with tiny electric signals perhaps?) but as soon as it stopped moving I once again couldn’t feel or hear anything. The closest thing I can describe it as is that it felt and sounded like my ears kept popping. Once both were in position it was over to my lead endocrine nurse.
Now is the important part, taking the blood samples. My arm cannula actually kept messing about and I was worried they wouldn’t get the samples and would make me have to come back another day to repeat it but it worked ok in the end (I hope, have yet to get the results). These must be taken from all 3 sites simultaneously so it requires a lot of co-ordination. A few samples are taken. One baseline is done first then a minute later the CRH is injected. A cycle then follows of taking a ‘discard’ (I assume this is as it sounds and discarded to ensure only a ‘true’ sample is taken), then a sample, then the cannulas are flushed with saline solution. This happens at specific intervals after the CRH; I think it was 1 minute after, 2 minutes, 3, 5 and 10. You won’t feel a thing here as it’s all done through the cannulas except possibly with the flushing. I got mild pain in my arm when the flushing was done and no pain in my head but I could hear the flushing which was an odd experience. Once your final sample is taken it’s all over. You made it! The catheters are pulled out and cannulas are removed which you don’t feel at all. Pressure is applied to the groin “puncture sites” as my nurses kept delightfully calling them for 5 – 10 minutes to stop any bleeding.
Finally is recovery. You’re not allowed to move at all for 2 hours afterwards so you’re lifted back onto your trolley/bed which is a strange experience as you want to help by shuffling but you mustn’t. You then have to lie flat and still for 2 hours. Provided your wounds look ok (I say wounds which sounds like they’re huge but they are tiny) you will then slowly be allowed to sit up and have something to eat if you feel ok. Within maybe 15 minutes of sitting up I was well enough to walk to the toilet and back; only a short distance and I was stiff-legged from all the lying down but it’s a quick recovery. I had a slight headache after but it cleared up once I could sit up so I think that was from lying down more than having the catheters in my head. An hour after sitting up I was allowed to go home with strict instructions on how to look after the wounds and to take it easy for the next 48 hours.
It’s now been 48 hours and I haven’t suffered any major pain. I took some paracetamol before bed that same night and also last night but more as a precaution so I wouldn’t suddenly wake up in agony in the night. However I’ve had pretty much no pain; I am walking with a shortened stride and have had a slight sore moment now and then when just sitting down but nothing I needed painkillers for. I’ve probably done more than I should as well as I had a GP appointment first thing in the morning the following day. They do warn you may get a headache within the first 24 hours but again I seem to have avoided that and so far have noticed no bruising.
Overall the whole procedure took maybe 2 hours. I booked into the ambulatory care ward at 11.45, I went in to theatre at 14.30 and was out just before 17.00 and discharged by 20.00. It really isn’t too bad but if you are very nervous as I said at the start I think you can ask for sedation. You can click here for the leaflet my hospital gives out to anyone having this procedure for the more technical explanation of an IPSS and risks associated with it.