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Acute Meningitis

by Carlo Raj, MD
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    00:01 Let’s begin with acute meningitis.

    00:03 So what is happening here? Inflammation of the meninges, leptomeningeal, and as I told you earlier, where you will be paying attention to and serious of detail, is going to be the evaluation of the cerebrospinal fluid.

    00:16 That will then tell you or clue you in what’s the cause of my acute meningitis.

    00:21 Bacterial, fungal, viral, whatnot or could be a combination where you have meningoencephalitis.

    00:27 What does that mean? Well, what's adjacent to the meninges again? Of course, the brain parenchyma.

    00:32 So don’t memorize, just take a look.

    00:34 If the meninges are undergoing pathologic processes, then as is at some point in time the adjacent parenchyma of the brain which then brings into what definition? Good.

    00:44 Encephalitis.

    00:46 Both the parenchyma and the meninges undergoing pathologic changes.

    00:51 Acute meningitis, infectious, could be bacterial, viral.

    00:54 You want to keep mycobacterial separate please.

    00:58 Then you have spirochetal, fungal and parasitic.

    01:00 Granted mycobacterial and spirochetal are, in fact, the bacterial, but I need you to keep this separate.

    01:06 Why? Because as we go through meningitis, I need you to be able to diagnose, is my patient suffering from meningitis as tuberculosis being the cause or was it something like Lyme disease referring to Borrelia burgdorferi.

    01:21 Now, overall theme, what’s happening here? CNS infections.

    01:27 What’s my topic? Acute meningitis, inflammatory process, granted infections.

    01:33 Right? And I told you earlier, let's say that there is chemical injury, then what do you think that a particular organ is going to do undergoing inflammatory process, but is it purely infectious? Not really, right? So we’ll talk about this quickly, a couple of points on chemical and also neoplastic.

    01:51 Neoplastic, of course, is not being infectious, but if you have neoplastic, let’s say, changes taking place in the meninges.

    01:59 Once again, you get the point.

    02:01 Inflammation, acute meningitis.

    02:03 Let's continue.

    02:05 Now, here’s a couple of tables here.

    02:07 I’m not going to bore you with the detail and you know how to read your tables.

    02:11 These tables, as you know, are money.

    02:13 Right? And so, by that I mean, if you know these tables well, do everything you're powered to.

    02:19 Somehow, extract these tables out of all of my lecture series.

    02:24 Because, this then summarizes and you will understand what’s going on with your patient.

    02:30 But in order for these tables to really make sense to you, you need to make sure that you have a full understand of the pathogenesis.

    02:38 First, under the column of no infection, WBC 0-6.

    02:43 Now, when you say WBC, what are you referring to? Well, could it be a neutrophil? Could it be a lymphocyte? Keep that in mind.

    02:51 So normally, let’s say 0-6.

    02:53 What are we looking at? We’re looking at the cerebrospinal fluid.

    02:57 What are we looking at? Not the plasma, not the urine, you’re looking at the cerebrospinal fluid.

    03:05 There should normally be no neutrophil.

    03:07 This is the first column.

    03:09 RBCs very minimal.

    03:12 Glucose, know 40-80, memorize that.

    03:16 The reason I say that is because let’s talk about bacterial meningitis for one second.

    03:21 How do you think bacteria survive? They survive by consuming glucose, just as we do, granted the metabolism a little bit different biochemistry.

    03:29 But nonetheless, bacteria is going to consume glucose.

    03:32 So therefore, what’d you expect the glucose able to be in a bacterial meningitis? Obviously decreased.

    03:38 What about viral? Viruses are different beasts, aren’t they? They are magnanimous organisms that know exactly what they’re doing and they’re very manipulative and they use the host.

    03:50 So that it can survive and duplicate, as you know, from microbiology.

    03:54 So the glucose levels, RBC will be different from viral meningitis.

    03:57 Memorize 40-80, please.

    04:00 Protein, once again here, 20-50.

    04:03 So as we go through this, let me give you a little bit of understanding as to why we find certain findings in our cerebrospinal fluid.

    04:13 If it’s acute bacterial meningitis, I have an 18-year-old who has gone to college, staying in dorms and then you know about your signs and symptoms of meningitis that you’ve talked about in microbiology is going to be difficulty with looking at lights.

    04:28 Trust me, here I am in a studio and these lights, if I had meningitis, there is no way that I could be in this room talking to you.

    04:35 Because I’d be whimpering, right? So photophobia, headaches, nuchal rigidity if you heard it before, Brudzinski sign, so on and so forth.

    04:44 Difficulty raising the legs.

    04:46 So that’s your meningitis.

    04:47 An 18-year-old gone to college, at this point, you should know about your bacteria or the species causing the particular meningitis.

    04:55 Maybe it’s a Neisseria species, right? If it’s a teenage college year.

    05:01 What if it was a young baby, a neonate? The bacteria there is a little bit different, isn’t it? You’ve heard of your CAMP-positive Streptococci agalactiae or maybe perhaps E. coli Gram-negative organism.

    05:15 So what I’m saying to you, at this point, it would be a really good idea for you to go back to microbiology and pay attention to what are the most common bacterial organisms that are causing meningitis, based on the age groups.

    05:28 Do that for me now, then come back and then, you memorize some of these numbers or more importantly understand the concepts.

    05:37 Let say, how about acute bacterial, what does that mean to you? What do you mean, what does that mean to you? In immunology, what are you going to bring in? What kind of cells? Neutrophils.

    05:46 So this neutrophil specifically is then going to contribute to that increased WBC count.

    05:51 That shouldn't be even a surprise.

    05:52 Next, well, in terms of RBCs granted, It might be a little bit more elevated, but could be within normal range.

    06:00 Now, here is that all-important fact that I just walked you through.

    06:04 In order for these prokaryotes to function properly and to thrive, they require energy in a form of what? Glucose.

    06:12 They’re consuming glucose.

    06:13 Take a look, please.

    06:15 Cerebrospinal fluid with bacterial infection, meningitis less than 30.

    06:19 Point is, the concept of consumption of glucose.

    06:23 Next, these neutrophils are coming in.

    06:26 And what’d they do? Taking a bite out of these bacteria.

    06:31 And bacteria made up of what? Say that I’m going to breakdown my cells, then I’m going to breakdown myself.

    06:36 Say that I am the bacteria and there is a neutrophil coming in to attack me.

    06:40 What are you going to be left with? My residue, as a human being or bacteria is going to be protein, protein, protein.

    06:47 Hence, your protein levels will be higher and the cerebrospinal fluid with bacterial meningitis.

    06:54 Don’t memorize that part.

    06:56 You understand the concept.

    06:58 Then if you want, memorize some of these values.

    07:01 Are we okay so far? Let’s go on to fungal and viral meningitis and group these together.

    07:07 So under fungal, let’s say that this patient is HIV positive.

    07:10 Maybe unfortunately goes on to contract Cryptococcal leptomeningitis.

    07:16 Viral meningitis, I’ll walk you through a few of these.

    07:19 A little bit different before we move on once again.

    07:22 If you have an infection, you can expect that WBC count to be elevated, but definitely not as high as what you find with bacteria.

    07:28 Next, if viral, what kind of WBC would you expect? Not so much neutrophil, huh? Not so much neutrophil.

    07:37 Granted maybe a little bit, but not so much.

    07:40 Or maybe lymphocytes, in fact.

    07:42 RBC count relatively normal and then glucose.

    07:46 Remember, these are viruses and fungal and so therefore, the glucose consumption is not going to be as dramatic as what we saw with bacterial, correct? Look, your glucose level here could be within normal range.

    08:00 Protein here, viruses, you’ve heard of single-stranded and double-stranded DNA and such.

    08:06 Single-stranded, a little scrawny sucker, right? And if you’re going to break me down as being a little skinny dude, then what’s going to happen? I’m not going to release much protein, am I? No.

    08:18 So therefore, take a look at the differences, contrast please.

    08:21 The protein content and CSF and bacterial, which is higher and viral granted, yes.

    08:28 It’s a little bit higher but definitely not as high as what you'd find with bacterial.

    08:32 Let’s move on.

    08:34 Let’s say that your patient is suffering from HSV encephalitis.

    08:38 Remember, you can have a combination of meningoencephalitis, can't you? So be careful there.

    08:44 Use it as a continuum.

    08:45 You know that the meninges are adjacent to the parenchyma.

    08:48 There is every possibility that both of these structures could be affected.

    08:52 Here, the WBC count, we’re talking about a virus.

    08:56 So therefore, it will be elevated, but here the WBC type would not be a neutrophil predominantly, granted a little bit, but not predominantly.

    09:06 Here, the RBCs would be elevated with the HSV because I were talking about involvement of the brain parenchyma as well.

    09:13 So this becomes important for us, doesn’t it? 10-500.

    09:17 So I need you stop here.

    09:19 Digest this, under HSV encephalitis, please.

    09:23 Let’s move on.

    09:25 What about glucose? Remember once again, this is a virus.

    09:28 Therefore, you’re not going to consume as much.

    09:30 And so therefore, your glucose could be greater than 30.

    09:33 And then here, the protein, once again, higher but definitely not as high as what you'd find with bacterial.

    09:40 So be careful when your doing herpes and we do encephalitis, it’s also the meninges that could be affected.

    09:47 And if you’re evaluating your CSF, RBCs will play a role.

    09:51 We’ll talk more about the pathogenesis of each one of these categories.

    09:55 Do not worry.

    09:56 Let's talk about brain abscesses.

    09:58 Brain abscesses, you should be thinking about bacterial, more or less.

    10:01 WBCs will be elevated.

    10:04 Brain abscess here though, we’re talking about neutrophils not being as high.

    10:08 RBCs would be elevated more so, because we’re talking about once again the brain being affected.

    10:14 And so therefore, the CSF is reflecting the damage to the brain, say in concept.

    10:20 Here, the glucose could be elevated and the protein would be higher.

    10:24 We’ll talk a little bit more about brain abscess in the form of ring-form of lesion.

    10:28 You will know for sure that you are dealing with the brain abscess.

    10:31 But overall, here’s a really good extensive table for you to evaluate some of your cerebrospinal fluid.


    About the Lecture

    The lecture Acute Meningitis by Carlo Raj, MD is from the course CNS Infection—Clinical Neurology. It contains the following chapters:

    • Acute Meningitis
    • Acute Bacterial Meningitis: CSF Findings

    Included Quiz Questions

    1. HSV
    2. Bacteria
    3. Fungus
    4. Rickettsial
    5. Prion
    1. There is an increase in the protein due to the phagocytic breakdown of bacterial wall and release of protein.
    2. There is a decrease in protein due to phagocytic consumption of the bacterial wall by inflammatory cells.
    3. The protein levels are normal in this patient.
    4. The protein level is increased due to secretion of proteinaceous material by the living bacteria.
    5. The protein levels in CSF can vary from being high to low.
    1. Lymphocytes
    2. Neutrophils
    3. Monocytes
    4. Basophils
    5. Eosinophils
    1. Glucose is less in acute bacterial meningitis due to consumption of it by the bacteria.
    2. Glucose level is more in CSF due to the secretion of glucose in bacterial meningitis
    3. Glucose levels vary based on a number of bacteria in CSF
    4. Glucose levels are more as the bacteria prevents the usage of glucose.
    5. Glucose levels are more because of breakage of the cells by the bacteria.
    1. Acute bacterial meningitis
    2. Normal CSF
    3. Brain abscess
    4. Fungal meningitis
    5. Viral meningitis

    Author of lecture Acute Meningitis

     Carlo Raj, MD

    Carlo Raj, MD


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