Meningitis – causes, symptoms, diagnosis, treatment, pathology (YouTube Video Transcript)

(00:00:00) Your YouTube transcript will appear here (00:00:04) With menitis, mening refers to the (00:00:06) meninges which are three protective (00:00:09) membranes that cover the brain and (00:00:10) spinal cord and itis refers to (00:00:13) inflammation. So menitis is an (00:00:16) inflammation of the meninges. (00:00:18) More specifically, it refers to (00:00:19) inflammation of the two inner layers (00:00:21) which are called the lepto meninges. (00:00:28) The outer layer of the meningis is the (00:00:29) dura mater. The middle layer is the (00:00:31) arachnoid m and the inner layer is the (00:00:34) pomater. (00:00:36) These last two the arachnoid and (00:00:38) pomoders are the leptomening. (00:00:42) Between the leptomening there's a (00:00:44) subacoid space which houses cerebral (00:00:47) spinal fluid or CSF. (00:00:49) CSF is a clear watery liquid which (00:00:52) pumped around the spinal cord and brain (00:00:54) cushioning them for impact and bathing (00:00:56) them in nutrients. (00:00:59) In one microL or cubic millimeter there (00:01:03) are normally just a few white blood (00:01:04) cells up to five. If we look at a bigger (00:01:07) sample like say a desileer then around (00:01:10) 70% of those will be lymphosytes 30% (00:01:13) will be monocytes and just a few will be (00:01:16) polymorphonuclear cells or PMN's like (00:01:19) neutrfils (00:01:22) that same volume will have some proteins (00:01:24) in it as well about 15 to 50 mg as well (00:01:27) as some glucose about 45 to 100 mg which (00:01:32) is close to 2/3 of the glucose we'd find (00:01:34) in the same volume of blood. The (00:01:36) cerebral spinal fluid is held under just (00:01:38) a little bit of pressure below 200 mm of (00:01:41) water which is just under 15 mm of (00:01:44) mercury which is less than a fifth of (00:01:46) the mean arterial pressure. (00:01:50) Now at any given time there's about 150 (00:01:53) milliliters of cerebral spinal fluid in (00:01:55) the body and this is constantly (00:01:57) replenished with around 500 milliliters (00:02:00) of new cerebral spinal fluid produced (00:02:02) every day and the excess or 500 minus (00:02:05) 150 or 350 is absorbed into the blood. (00:02:10) But for any nutrients to enter or leave (00:02:12) the cerebral spinal fluid and the brain (00:02:14) itself for that matter, they have to go (00:02:17) through the tightly regulated bloodb (00:02:18) brain barrier. (00:02:20) The bloodb brain barrier is a special (00:02:22) name given to the blood vessels in the (00:02:23) brain. That's because the endothelial (00:02:26) cells in the blood vessels are so (00:02:27) tightly bound to one another that they (00:02:29) prevent leakage and only allow certain (00:02:31) molecules to slip through them. (00:02:34) Menitis is the inflammation of the lepto (00:02:37) meninges which remember are the inner (00:02:39) two membranes around the brain and (00:02:40) spinal cord. It is not the inflammation (00:02:43) of the brain itself. That's encphylitis. (00:02:47) But sometimes they can happen together (00:02:48) and when that happens it's called (00:02:49) meningo and sephilitis. (00:02:54) So menitis needs some kind of trigger (00:02:56) for the inflammation and this could be (00:02:58) an autoimmune disease where the body (00:03:00) attacks itself like lupus or the body (00:03:03) having an adverse reaction to some (00:03:05) medication which can happen with (00:03:07) intratheal therapy when medication is (00:03:09) injected directly into the cerebral (00:03:11) spinal fluid. But by far infection is (00:03:14) the most common trigger for menitis (00:03:16) across all age groups like with the (00:03:19) neria menitis bacteria or herpes simplex (00:03:22) virus. (00:03:25) Now there are two routes that an (00:03:26) infection can take to reach the cerebral (00:03:28) spinal fluid and lepto meninges. The (00:03:30) first way is direct spread which is when (00:03:33) a pathogen gets inside the skull or (00:03:34) spinal column and then penetrates the (00:03:36) meninges eventually ending up in the (00:03:38) cerebral spinal fluid. (00:03:41) Sometimes the pathogen will have come (00:03:42) through the overlying skin or up through (00:03:44) the nose. But it's more likely that (00:03:46) there's an anatomical defect to blame. (00:03:49) For example, it could be a congenital (00:03:50) defect like spinoipida or an acquired (00:03:53) one like a skull fracture where there (00:03:55) might be cerebral spinal fluid leaking (00:03:57) through the sinuses. (00:04:00) The second way is hematogenous spread (00:04:02) which is when a pathogen enters the (00:04:04) bloodstream and moves through the (00:04:05) endothelial cells in the blood vessels (00:04:07) that make up the bloodb brain barrier (00:04:09) and get into the cerebral spinal fluid. (00:04:12) To do this, the pathogens typically have (00:04:14) to bind to surface receptors on the (00:04:16) endothelial cells in order to get (00:04:17) across. (00:04:19) Otherwise, they have to find areas of (00:04:20) damage or more vulnerable spots like the (00:04:22) koid plexus. (00:04:26) Once the pathogen finds a way into the (00:04:28) cerebral spinal fluid, it can start (00:04:30) multiplying. (00:04:31) Soon enough, the handful of white blood (00:04:33) cells surveilling the cerebral spinal (00:04:34) fluid identify the pathogen and release (00:04:37) cytoines to recruit additional immune (00:04:39) cells. (00:04:41) Over time, a microl of cerebral spinal (00:04:43) fluid might go on to contain thousands (00:04:45) of white blood cells, but any more than (00:04:48) five usually defines menitis. (00:04:51) In most bacterial cases, they'll be (00:04:53) above 100 white blood cells per microl (00:04:56) and more than 90% polymorphuclear cells. (00:05:00) In most viral cases, there'll be 10 to (00:05:02) a,000 white blood cells and over 50% (00:05:06) lymphocytes and under 20% PMN's. (00:05:10) In most fungal cases, there'll be 10 to (00:05:12) 500 white blood cells with over 50% (00:05:15) being lymphocytes. (00:05:17) In most cases of tuberculosis menitis, (00:05:20) there'll be 50 to 500 white blood cells (00:05:22) with over 80% being lymphocytes. The (00:05:25) additional immune cells attract more (00:05:27) fluid to the area and start causing (00:05:28) local destruction as they try to control (00:05:31) the infection. As a result, the cerebral (00:05:34) spinal fluid pressure typically rises (00:05:36) above 200 mm of water. The immune (00:05:39) reaction also causes the glucose (00:05:41) concentration in the cerebral spinal (00:05:42) fluid to fall to below 2/3 of the (00:05:45) concentration in the blood. It also (00:05:47) makes the protein levels increase to (00:05:49) over 50 mg per deciliter. (00:05:52) When it comes to the causes of menitis, (00:05:55) viruses and bacteria usually cause acute (00:05:57) menitis whereas fungi usually causes (00:06:00) chronic menitis. (00:06:02) Now for bacteria, there are a lot of (00:06:04) possibilities. In newborns, the most (00:06:06) common causes are group B streptooxy, (00:06:09) E.coli and Lysteria monocytogens. (00:06:13) In children and teens, the most common (00:06:15) causes are neria meningitis and (00:06:18) streptoccus pneumoni. (00:06:20) In adults and the elderly, the most (00:06:22) common causes are streptococcus pneumoni (00:06:24) and lististeria monocytogens. (00:06:27) There are also tickborn causes of (00:06:28) menitis like borellia burgdafori (00:06:31) bacteria which is the cause of Lyme (00:06:32) disease. (00:06:34) As for viruses, the main culprits are (00:06:36) interero viruses, especially coxsaki (00:06:39) virus as well as herpes simplex virus. (00:06:43) HIV is usually contracted through body (00:06:45) fluids and can also cause viral menitis. (00:06:49) Less common causes include the mums (00:06:51) virus, vericella zoster virus and (00:06:54) lymphocitic coromeitis virus. (00:06:58) There's also the fungi like those from (00:07:00) the cryptocus and coxidioides genuses (00:07:03) which mainly affect imunocmpromised (00:07:05) individuals (00:07:07) and then of course there's tubercular (00:07:08) menitis which is caused by the (00:07:10) mcoacterium tuberculosis bacteria and (00:07:14) finally parasitic causes of menitis like (00:07:16) pelipum which is the main cause of (00:07:18) malaria. (00:07:22) Now the classic triad of menitis (00:07:24) symptoms are headaches, fevers and nucal (00:07:27) rigidity or neck stiffness. (00:07:30) It can also cause phototohobia which is (00:07:31) discomfort with bright lights or (00:07:33) phonophobia which is discomfort with (00:07:35) loud noises. (00:07:38) Maningo andphilitis can cause an altered (00:07:40) mental state or seizures. (00:07:43) The diagnosis of menitis starts with a (00:07:45) physical exam. One maneuver is when a (00:07:48) person lies flat on their back facing (00:07:49) upwards and one of their legs is raised (00:07:51) with the knee flexed to a 90° angle. (00:07:54) Then the leg is supported and slowly (00:07:56) straightened at the knee. If this causes (00:07:59) back pain, then it's called kernig sign. (00:08:03) Another maneuver is when a person again (00:08:05) lies flat on their back facing upwards (00:08:07) and then has their neck supported and (00:08:09) flexed. If this causes them to (00:08:11) automatically flex their knees or hips, (00:08:13) then it's called the Brazinski sign. (00:08:17) If menitis is suspected, a lumbar (00:08:19) puncture can be done. This is when a (00:08:21) needle goes through the lower lumbar (00:08:23) vertebral levels of the spinal cord (00:08:25) between L3 and L4. For example, the (00:08:28) needle penetrates into the subacoid (00:08:30) space and a few milliliters of cerebral (00:08:32) spinal fluid is taken. The opening (00:08:35) pressure can be measured and the (00:08:37) cerebral spinal fluid can be analyzed (00:08:38) for white blood cells, protein and (00:08:41) glucose. (00:08:43) Polymerase chain reaction or PCR might (00:08:45) also be used to find specific causes (00:08:48) like HIV, interroviruses, HSV or (00:08:52) tuberculosis. (00:08:54) If a particular infection seems like an (00:08:56) obvious cause, then a test for that (00:08:58) might be used like the western blot for (00:09:00) borellia burgdory bacteria or a thin (00:09:03) blood smear for malaria. (00:09:06) The treatment of menitis depends on the (00:09:08) underlying cause. For bacterial menitis, (00:09:11) it's common to administer steroids and (00:09:13) then antibiotics to prevent massive (00:09:16) injury to the leptomening from the (00:09:17) inflammation caused as the antibiotics (00:09:19) destroy the bacteria. (00:09:22) In general, drug treatments like (00:09:24) antivirals, antibacterials, antifungals (00:09:27) or antiparasitics are aimed at the (00:09:29) specific cause of menitis. (00:09:32) Prevention with a vaccine is appropriate (00:09:34) for some causes like neria men anditis (00:09:37) but also for mumps and for disseminated (00:09:39) tuberculosis. (00:09:42) Prophylactic antibiotics can also be (00:09:44) administered to avoid outbreaks of (00:09:46) bacterial menitis like in households (00:09:48) where individuals haven't been (00:09:49) vaccinated against necessaria menitis. (00:09:53) All right, as a quick recap, menitis is (00:09:56) an inflammation of the lepto meninges, (00:09:58) which is the inner two membranes that (00:10:00) surround and protect both the brain and (00:10:01) the spinal cord. It normally starts when (00:10:04) a foreign substance, oftentimes (00:10:06) bacteria, makes its way inside the (00:10:08) leptomening (00:10:10) either by direct contact or hematogenous (00:10:12) spread through the bloodb brain barrier. (00:10:15) The immune system responds to the (00:10:16) antigen by flooding the subberacttoid (00:10:18) space with white blood cells which (00:10:20) release cytoines and create (00:10:22) inflammation. And this results in the (00:10:24) classic triad of symptoms which is (00:10:26) headaches, fevers and neck stiffness. (00:10:34) Hey guys, what's up? Thanks for watching (00:10:35) that video on menitis. Hopefully you (00:10:37) learned a thing or two. Uh if you are (00:10:39) interested in learning more about that (00:10:40) topic, you should for sure head over to (00:10:42) our uh platform called Osmosis at (00:10:45) osmosis.org. (00:10:46) Uh we have a bunch more flashcards and (00:10:48) quiz questions that you can help test (00:10:50) your knowledge on that topic. And also (00:10:53) uh in addition to that, we have a lot (00:10:54) more videos as well. We have a whole (00:10:56) series on ECG and we're starting to (00:10:57) build up a bunch of embryology videos uh (00:11:00) as well as some more physiology videos. (00:11:02) So if you are interested in checking (00:11:03) those out, I would highly encourage (00:11:05) heading over to osmosis.org and making (00:11:07) an account. Um, otherwise you can always (00:11:09) support us by donating on Patreon and (00:11:11) subscribing to our channel and following (00:11:12) us on social media. All right, guys. (00:11:15) Till next time. See you.