Ultrasound guided LP

[NWwildcat2013]

Watched an LP today that was difficult. I found myself wondering "Why can't this be done with US guidance." A quick Google search showed me it definitely can. Is this common and how many of you use US routinely in practice? Do you use an US probe separately to scout the anatomy and plan trajectory or do some probes have ports for the needle and show trajectory on the screen (I've seen this for some US guided biopsy)?

My patient ended up getting a flouro guided LP with rads. Why can't a neurologist do this? Seems like a natural extension of their practice.

Lots of questions, but I am curious. Going in blind seems silly when US is so common.

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[warchild]

I tried US guided LP for the first time recently. Obese patient, I found my landmarks best I could manually, but after sticking him a few times I couldn't get it, and wasn't even sure I was puncturing the right spot. He had a very magnetic gait, and I knew IR wouldn't be walking him before and after. Also their 'high volume tap' isn't very voluminous. So I grabbed the US and identified the interspace better, marked it, and tried again and got it. I'm glad I persisted because he dramatically improved after the tap and is now scheduled for shunting.

 

[kchan99]

At my residency program, we had the same issue with defining "high volume" with IR. To get truly high volume taps from IR, we sent a list of commonly ordered CSF labs with their minimum required CSF volumes. For NPH evals with need for IR help, then we discussed with IR, and sent a resident to personally collect CSF. Fortunately, that didn't happen often.

 

[DrBowtie]

At my residency program, we had the same issue with defining "high volume" with IR. To get truly high volume taps from IR, we sent a list of commonly ordered CSF labs with their minimum required CSF volumes. For NPH evals with need for IR help, then we discussed with IR, and sent a resident to personally collect CSF. Fortunately, that didn't happen often.

Rad here. Please define high volume tap in mL. I'd be curious to see if the "high volume" verbiage amount is standardized amongst neurologists or radiologists.

I'm always happy to oblige when given discrete instructions on the order request.

 

[kchan99]

Rad here. Please define high volume tap in mL. I'd be curious to see if the "high volume" verbiage amount is standardized amongst neurologists or radiologists.

I'm always happy to oblige when given discrete instructions on the order request.

I always write the target volume in mL on my orders, which is customary in the lab test guide published by clinical pathology. For us, high volume is 25+ mL.

For many patients, I also request a few additional mL's to be saved for possible additional testing so the total requested volume will be a little bit more than the sum of the minimum or recommended volumes for tests.

 

[DrBowtie]

We always write the target volume in mL on my orders, which is customary in the lab test guide published by clinical pathology. For us, high volume is 25+ mL.

Great. Sounds like you're doing all you can to get exactly what you want. I'll say the vast majority of orders I get are not that explicit.

 

[clubdeac]

I used to do these commonly for a neurology practice. Used fluoro which is exponentially easier than US and I would say is the standard of care

 

[bretticus]

US is probably not going to be very useful unless we're talking infants. Any kind of bone will severely limit what you can see. Usually patients who are obese or have complex spinal anatomy are the ones referred for imaging guidance, and depth of field will then be a limitation as well. As mentioned, fluoro is going to be much easier.

Why can't a neurologist do fluoro-guided LPs? Nothing stopping them I'd imagine. Most likely just access to/training using the equipment, and maybe desire/reimbursement. Probably more trouble than it's worth considering you can just send to neurorad/IR. We'll be happy to oblige with the volume needed if you specify.

 

[kchan99]

Why can't a neurologist do fluoro-guided LPs? Nothing stopping them I'd imagine. Most likely just access to/training using the equipment, and maybe desire/reimbursement.

Some neurology residency programs provide training in fluoro-guided LPs.

 

[turkeyjerky]

US is probably not going to be very useful unless we're talking infants. Any kind of bone will severely limit what you can see. Usually patients who are obese or have complex spinal anatomy are the ones referred for imaging guidance, and depth of field will then be a limitation as well. As mentioned, fluoro is going to be much easier.

Why can't a neurologist do fluoro-guided LPs? Nothing stopping them I'd imagine. Most likely just access to/training using the equipment, and maybe desire/reimbursement. Probably more trouble than it's worth considering you can just send to neurorad/IR. We'll be happy to oblige with the volume needed if you specify.

The utility of US is in order to define the bony landmarks, and essentially assist with guiding a landmark based approace (it's not done real time like vascular access). It can certainly help w/ fatties (is that an SP or just a subcu chicken wing?) but it's not a game changer with the truly difficulty anatomy. I haven't really seen anything showing it's beneficial in infants though

 

[Neurologo]

Rad here. Please define high volume tap in mL. I'd be curious to see if the "high volume" verbiage amount is standardized amongst neurologists or radiologists.

When "high volume" is used, it usually means a diagnostic tap for NPH with PT eval of gait before and after the tap (immediately after and then every 1-2 hrs upto 4-6 hrs before calling "no improvement"). For it to be effective, the volume should be 40-55 ml. Otherwise, with just 25 ml the test is not reliable to rule out or in the utility of a VP shunt.

The ordering neurologist should always write how much volume is needed in ml. Otherwise, no one should blame the tapping radiologist for not collecting enough fluid.

 

[kchan99]

When I was mentioning a high volume of 25+ ml, I was not referring to NPH evals. I was referring having enough CSF for cytology and/or flow cytometry.

In NPH evals, many centers are using extended lumbar drainage protocols rather than LP.