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, 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 level 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 us see, 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 Hence, your protein levels will be higher.

    06:27 The main cause of protein level elevation is the severe disruption of the CSF blood barrier, which is also responsible for the markedly elevated WBC counts seen in bacterial meningitis.

    06:40 In the cerebral spinal fluid with bacterial meningitis.

    06:43 Don't memorize that part. You understand the concept.

    06:48 Then if you want to memorize some of these values.

    06:51 Are we okay so far? Let's go on to fungal and viral meningitis group these together.

    06:56 So under fungal, let's say that this patient is HIV positive, maybe.

    07:01 Unfortunately, goes on to contract cryptococcal type of meningitis.

    07:05 Viral meningitis.

    07:06 I'll walk you through a few of these.

    07:08 A little bit different before we move on.

    07:10 Once again, if an infection you can expect the WBC count to be elevated, but definitely not as high as what you find with bacterial.

    07:18 Next.

    07:20 If the viral, what kind of WBC would you expect? Not so much neutrophil, huh, not so much neutrophil.

    07:27 Granted, maybe a little bit, but not so much.

    07:29 More maybe lymphocytes, in fact.

    07:32 RBC count relatively normal, and then glucose.

    07:35 Remember, these are viruses and fungal.

    07:37 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.

    07:50 Protein here is mildly elevated, because the disruption of the CSF blood barrier in viral meningitis is minimal.

    07:58 So therefore, take a look at the difference is contrast please the protein content, and CSF, and bacterial, which is higher and viral, granted? Yes.

    08:09 It's a little bit higher, but definitely not as high as what you find with bacterial.

    08:13 Let's move on.

    08:15 Let's say that your patient is suffering from HSV encephalitis.

    08:19 Remember, you can have a combination of meningoencephalitis, can't you? So be careful there. Use it as a continuum.

    08:26 You know that the meninges are adjacent to the parenchyma.

    08:29 There's every possibility that both of the structures could be affected.

    08:33 Here, the WBC count, we're talking about a virus.

    08:36 So therefore it will be elevated.

    08:38 But here, the WBC type would not be neutrophil predominantly Granted? A little bit, but not predominantly.

    08:47 Here, the RBCs would be elevated with the HSV, because now we're talking about involvement of the brain parenchyma as well.

    08:54 So this becomes important for us, doesn't it? 10 to 500.

    08:58 So I need to stop here, digest this, under HSV encephalitis, please.

    09:05 Let's move on.

    09:06 What about glucose? Remember, once again, this is a virus.

    09:09 Therefore, you're not going to consume as much and so therefore, glucose could be greater than 30.

    09:14 And then hear the protein, once again, higher but definitely not as high as what you find with bacterial.

    09:21 So be careful when you're doing herpes.

    09:23 And when you do encephalitis, it's also the meninges that could be affected.

    09:28 And if you're evaluating your CSF, RBCs will play a role.

    09:32 We'll talk more about the pathogenesis of each one of these categories.

    09:36 Do not worry.

    09:37 Let's talk about brain abscesses.

    09:39 Brain abscesses, you should be thinking about bacterial more or less.

    09:42 WBC's will be elevated.

    09:44 Brain abscess here though, we're talking about neutrophils not being as high.

    09:49 RBCs would be elevated more so because you're talking about, once again the brain being affected.

    09:55 And so, therefore, the CSF is reflecting the damage to the brain.

    10:00 Same concept.

    10:01 Here, the glucose could be elevated and the protein would be higher.

    10:05 We'll talk a little bit more about brain abscess in the form of ring forming lesion.

    10:09 You will know for sure that you're dealing with the brain abscess.

    10:12 But overall, here's a really good extensive table for you to evaluate some of your cerebral spinal fluid.

    About the Lecture

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

    • Acute Meningitis
    • Acute Bacterial Meningitis: CSF Findings

    Included Quiz Questions

    1. Herpes meningoencephalitis
    2. Bacterial meningoencephalitis
    3. Fungal meningoencephalitis
    4. Mollaret's meningoencephalitis
    5. Prion disease
    1. Severe disruption of the CSF blood-brain barrier leads to markedly elevated protein and WBC levels.
    2. Severe disruption of the CSF blood-brain barrier leads to markedly elevated protein levels only.
    3. Severe disruption of the CSF blood-brain barrier leads to markedly elevated WBC levels only.
    4. Elevation of the protein level is due to lysis of the bacterial walls.
    5. Elevation of CSF glucose levels is seen.
    1. Lymphocytes
    2. Neutrophils
    3. Monocytes
    4. Basophils
    5. Eosinophils
    1. Acute bacterial meningitis
    2. Parasitic meningitis
    3. Herpes meningoencephalitis
    4. Fungal meningitis
    5. Viral meningitis

    Author of lecture Acute Meningitis

     Carlo Raj, MD

    Carlo Raj, MD

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    Very useful content
    By olanipekun o. on 24. May 2020 for Acute Meningitis

    Great material and the table was just super fantastic. I would appreciate the Lecturio team makes an update to this video, describing the general clinical presentation of meningitis, that will be a big booster.

    Very helpul table
    By Rodrigo C. on 06. November 2019 for Acute Meningitis

    Very good table explained and I appreciate the extra details added to it.