Transcript: Managing Lower Limb Numbness In Primary Care

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Liz Rohr:
Well, hey, there. It's Liz Rohr from Real World NP and you are watching the Real World NP YouTube channel. We make weekly episodes to help save you time, frustration, and help you take the best care of your patients.

In this week's episode, I'm going to be talking about lower extremity numbness.

This is a really common chief complaint and it can be really stressful. There's a broad differential behind it, and it also can feel just really unnerving for patients. It's just something about it. I don't know. Anecdotally speaking, patients tend to feel a little bit unnerved about it.

In this episode, I'm going to be talking about:

  • the general approach to history,
  • specific history questions not to miss for this chief complaint, 
  • physical exam, differentials,
  • as well as approach to testing and referral when it comes to lower extremity numbness.
Jumping in, whenever I approach a chief complaint, a symptom-based chief complaint, I always use a systematic approach. If you've been with me for a while, you know that I use the OLDCART acronym to help guide my history so that I'm not missing anything.

Again, onset, location, duration, characteristics, associated factors, relieving factors, time, and treatment.

I always ask those questions to make sure that I'm gathering the information that I need. However, when it comes to specific chief complaints, you may have extra history questions not really captured with those questions. I'm going to jump into those.

Actually real quick before I do, another one that I add on to OLDCART is is it getting better, worse, or the same? Every single time. Absolutely every single time. It'll help you with so much information as well as have you had this before? Don't forget that question because it will give you a lot of information.

But the specific questions for history when it comes to lower extremity, one really important place to start is when you're eliciting the characteristics of the numbness.

There's two different kinds that I typically see or that's really seen in medicine.

One is like a stripe. It's some sort of stripe dermatomal pattern of like it's on the outside of my left foot. It's on the outside of my right leg or it's on the top of my foot on the right side, that kind of thing. Pro-tip is if you don't already have that printed out at your workspace, definitely just do a quick Google and print that out because it will help you in that memorization process that feels at first really overwhelming, but then once you start doing it like a thousand million times, you're like, "Oh, okay, this is the dermatome for L5, S1, L4, et cetera."

Then the next option is more of that stocking pattern. You probably heard of that stocking-glove pattern, but basically, instead of it being like a stripe or a side or just a toe or something like that, it's going to be the whole thing, like the whole foot as if they have a stocking on that is numb. Those two differentiators are really helpful when it comes to what path you go down for your differential diagnosis. We'll talk about that in a second.

A couple of other things you want to elicit in the history is about motor deficits. We'll talk about that with the differentials, but you want to see, are they having actual motor deficits that you can assess and evaluate versus is it a perceived like, "Oh, I actually can't move it because it's painful."

Spoiler alert, one of the top differentials is sciatica related to a lower back disc problem. Those patients can have just numbness, they can have pain, or they can actually have motor deficits. And so, you want to elicit on a scale from one to five, your actual assessment of their strength level.

Another PEARL is that when you're touching somebody's body, we always ask permission first. We explain what we're going to do. The other thing that I recommend everyone's cultural experience is so different, but one potential option to be polite and respectful of people's bodies is to use the back of our hands. If we're assessing their dorsiflexion, their plantar flexion, their quadricep muscle, their hamstrings, we have to press on their body a number of times and using the back of our hand, especially on the thigh, can be very respectful for patients because it's slightly more intimate to have your palm facing down. Again, there's different cultural interpretations that everybody has, but that's one potential option that I typically follow with my patients.

I've said this before, if you're not sure how to approach a differential, you just don't have it in the front of your mind with the history, you can always ask about any other associated factors. Just generally speaking, like ROS, review of systems, ask all the questions. But a couple of specific review of systems questions that you want to ask specifically with numbness are things like fatigue, other neurological deficits that they might have. Do they have any vision problems, any speech-related problems? Do they have numbness anywhere else on their body? Do they have other systemic symptoms like a rash, polyphagia, polyuria, or polydipsia? We'll talk about differentials in a second. Then again, I think I mentioned this already in case I didn't say it is, is the numbness spreading?

I sort of said already, is it getting better, worse, or the same, but specifically with numbness, we want to say, "Is this a spreading thing? How is it spreading? What does it look like?"

Actually, I want to segue into the differentials before we get to the physical exam, because hopefully, that will cement all of the questions that I've presented so far for the history.

The top three most common causes of lower extremity numbness in the United States are sciatica related to a disc problem in the lower back. I've already kind of said that. That will help you when you're talking about the distribution of the numbness, if they have motor deficits, if they have other things associated.

I do have a video episode. I don't think I have a podcast, but I have a video episode about back pain I can link to down below, but that's one of the most common causes. And so, that really ties into all those history questions.

The next one is diabetes-related neuropathy. That's more of that stocking pattern, less so than the dermatomal pattern, very common. Then you can also ask those diabetes-specific questions, polyuria, polydipsia, polyphagia, blurred vision, et cetera.

The third most common cause is nerve injury or damage. There isn't necessarily one overarching thing that can lead you to that pathway of differential pursuit. But typically, those patients will have some sort of injury or some sort of trigger that may be associated at the onset of it. I actually had someone in my life who was saying that they had toe numbness and I was like, "Oh, you have toe numbness. Do tell." We were talking about it. We did some digging and I was asking all these different questions and it turns out that she had a pair of boots that is likely the culprit that she had been wearing, and continues to wear, and it may have been pressing on some sort of local nerve versus a sciatica related back thing.

That's where all these history questions kind of get you, but let's talk about some of the other broad categories of differentials. I don't think it's going to be serving for you to go through the laundry list of all of the options, but if you can think about those broad categories and then start to investigate those pieces when you have a patient in front of you with these symptoms, then you can start to cement in that really broad list of differentials.

The categories that we're talking about with differential diagnosis, I've already talked about the nervous system, so we're talking about sciatica-related pain. We're talking about local nerve. We could be talking about some other more rare things like Guillain-Barre or some sort of spinal cord injury or tumor or something like that, but some sort of nerve-related thing. The point is not to memorize all of the little kinds of subcategories of the actual differentials, but if you can at least have nerves, like what kind of nerve-related things are we talking about here?

The next one is chronic condition related. This is kind of a broad category that I lumped together, but these are things like alcohol use disorder over the course of time can lead to some deficiencies and vitamins; diabetes, like I said, diabetes-related neuropathy; multiple sclerosis; thyroid dysfunction; autoimmune conditions. Those are the type of things that I'm talking about. Even if you don't feel super comfortable with rheumatoid arthritis, or Sjogren's syndrome, or lupus, you're like, "Okay, is this a stocking-glove? Is this metabolic? Is there something else going on or some sort of chronic condition related?"

I'm jumping ahead. The next one is metabolic. That's the category that I lumped together. Those are things like iron deficiency anemia, B12 deficiency, heavy metal toxicity, a little bit more of a rare one.

Last two general categories, one is infectious so things like syphilis and shingles potentially.

Then the last one is medications. There's actually a pretty long list of medications that can cause numbness and I can link to some of them below, but that's something to always think about when you're in your differential experience with this person in front of you is especially like, what are the meds that they're taking and is there any risk of numbness associated with those, especially with medications that you're not especially familiar with to look at those potential side effects of a med that you don't see all the time.

Now that we've talked about some of the differentials, let's just recap with the physical exam that pulls in all of those things together.

We want to do a full neurologic exam, including deep tendon reflexes. I know those are not the easiest, but it's good to practice them. We want to look at all the cranial nerves and we want to look at the patient's gait. Even if we're not neurological experts, we do our best, we collect the information, and then we go from there.

We do want to do an assessment of the extremity itself. We want to do a capillary refill. We want to look at pulses to see the circulation. Is there any some sort of potential vascular-related issue causing the numbness, less common of a cause, but something I look at. Then again, I talked about the physical exam of using the back of your hand, but you want to assess the strength, the range of motion, as well as the muscle strength especially of the lower extremities, related especially to lower back disc related problems.

Last things are approach to diagnostics. As you've probably gathered so far, there are some physical things we can assess. There are some history questions that we can get. Then there are some lab and some diagnostic tools that we have to help us with that history-taking process. The way I approach lower extremity numbness in primary care is asking all of those questions, doing the initial blood tests, and then just making a decision of do they need to be referred out? Basically, the majority of the time, we're talking about neurology. That's usually the person that the team you're going to refer out to, but you can start the workup with all of the potential chronic condition and metabolic causes and infectious causes too, of what can you potentially rule out before we get the assistance of neurology.

The labs that typically I do with lower extremity that's recommended, we're looking at blood sugar level, is this diabetes-related; thyroid, TSH, is this thyroid related. We want to do some preliminary potentially, depending on your history and your symptoms, we potentially want to consider some rheumatologic labs, perhaps an ANA, rheumatoid factor, CCP, anti-CCP which is a little bit more specific for rheumatoid arthritis. Again, based on your history and what you're looking at with the patient, not necessarily like a scattershot for every patient, potentially looking at a Lyme or RPR syphilis labs, definitely starting with a CBC, iron studies, and B12, because iron deficiency anemia, B12 deficiency, those are really things that we can handle in primary care.

Those are some of the labs to consider before you send somebody to neurology.

The next kind of last other thing that you may or may not do in primary care is an electromyogram, EMG and nerve conduction studies, NCS, EMG/NCS.

My personal approach, I think my impression is that this is a cultural perspective of your clinic and the culture of your supervising provider. Most of the providers that I have worked with and myself included, I have ordered EMG/NCS tests. The kicker is that you'd have to know how to interpret them and they are not easy to interpret. There is a reason why neurology providers do all the extensive training that they do, and that is their bread and butter.

My philosophy approach to practice is I would love to know how to very confidently interpret EMG/NCS tests. However, they are not easy to interpret and my physician colleagues do not do those either. They let neurology do them, so I do not. That is where I would stand if you are a newer grad, is that collaborate with your collaborator or supervising provider and think very hard before you order a test. Just because you know how to order it, doesn't mean you know how to interpret it, and even experienced physicians that I work with do not order and interpret these.

That would be my guidance and my personal perspective, but you get to decide your own philosophy of practice and what the rules are in your own clinic. The other note about that is that those are painful tests. They stick a needle basically and kind of shock your muscles and nerves and see what is responding. I've seen it in and someone in my life has gotten that done and it looks very painful. I tread very lightly before I do that.

One other test that you may see is an ankle-brachial index, which is assessing for blood flow, but kind of PEARL of practice there, if somebody has two plus or more pulses in their lower extremities, they probably don't need that test. That's really mainly for people who are not showing full signs of circulation in their lower extremities.

That is it.

That is the approach to history, physical exam, differentials, when to refer, and the tests that you want to consider ordering, and that triage-based approach in primary care.

Hopefully, this is a helpful place to work on your knowledge or cement your knowledge so that you feel more comfortable with this chief complaint.

Definitely check out the other episodes that I have linked below and the medication list that I've linked below.

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