Meningitis- Week 2 Flashcards
what is meningitis
inflammatory disease of the leptomeninges, the tissues surrounding the brain and spinal cord, defined by an abnormal number of WBC’s in the CSF
the meninges consist of 3 parts
the pia, arachnoid and dura maters
bacterial meningitis- when?
can be community acquired or healthcare associated- associated with a variety of invasive procedures or head trauma, and in patients with internal or external ventricular drains or following trauma - characteristic features of common causes of bacterial meningitis depends in part upon the route of acquisition and underlying host factors
major causes of community- acquired bacterial meningitis in adults in developed countries are
streptococcus pneumoniae neisseria meningitides
bacterial meningitis- where?
produced by the choroid plexus in the lateral, third and fourth ventricles–> by both filtration and active transport normal adults- CSF volume is 125 to 150ml 20% of CSF contained in ventricles 80% is contained in the subarachnoid space in the cranium and spinal cord
normal rate of CSF production, where does it circulate?
approximately 20ml/ hour circulates through the subarachnoid space between the arachnoid mater and the pia mater. Circulates from the lateral ventricles into the 3rd ventricle and then the 4th ventricle via the cerebral aqueduct *CSF secretion and reabsorption remain in balance in most healthy individuals to maintain a CSF pressure of less than 150mmH20
the major causes of healthcare- associated bacterial meningitis are different but usally
staphylococci and aerobic gram- negative bacilli, often after neurosurgery especially if patient was not put on antimicrobial prophylaxis to prevent surgical site infection
old major cause before vaccination?
haemophilus influenzae
classic triad
change in mental status fever nuchal rigidity but be aware: one or more of the classic findings on history or physical are absent in many patients
important caveat
clinical picture is often “unimpressive” when patient is first seen
HINT
URI interrupted by one of the “meningeal symptoms”: vomiting, headache, lethargy, confusion, stiff neck
pneumococcal meningitis- s. pneumoniae
gram + diplococci most common cause in adults- especially in older adults- 60% of cases in adults up to age 60 and almost 70% in older patients. - watch for neuro changes- hearing loss, seizures, papilledema, cerebral infarction - most common in kids 1 month- 4 years. Mortality 30% in kids, 80% in elderly - prevented by vaccine- PCV7
meningococcal meningitis- neisseria meningitis
characteristic skin changes, petechiae and palpable purpura
listeriosis
listeria monocytogenes- gram negative aerobic rod, usually foodborne; it can be transmitted to fetus - reproduce in phagocyttes often with the classic triad
to determine what kind
perform and interpret CSF examinations
normal findings of CSF
CSF is normally acellular. However, up to 5 WBC’s and 5 RBC’s are considered normal in adults when the CSF is sampled by lumbar puncture
CSF abnormalities
>3 polymorphonuclear leukocytes (PMNs)/ microL are abnormal in adults The CSF cell count determination should be performed promptly since the count may be falsely low if measured more than 60 minutes after the LP is performed
pleocytosis
an elevated CSF WBC
xanthochromia
normal CSF is clear and colorless - but yellow or pink discoloration of the CSF, represents most often the presence of hemoglobin degradation products and indicates that blood has been in the CSF for at least hours (eg, subarachnoid hemorrhage) - both infectious and noninfectious processes can alter the appearance of CSF - as few as 200 WBCs/ microL or 400 RBCs/ microL will cause CSF to appear turbid - CSF will appear grossly bloody > or eqal to 6000 RBCs/ microL are present
indications for lumbar puncture
suspicion of meningitis suspicion of subarachnoid hemorrhage suspicion of CNS diseases such as Guillain- Barre and carcinomatous meningitis therapeutic relief of pseudomotor cerebri injection of drugs and anesthetics
indications for CT prior to LP (in suspicion of meningitis)
patients older than 60 years patients immunocompromised patients with known CNS lesions patients who have had a seizure within 1 week of presentation patients with an abnormal level of consciousness patients with focal findings on neurologic exam patients with papilledema seen on physical exam, with clinical suspicion of elevated ICP
contraindications for LPs
increased ICP of an unidentified origin- can cause cerebral herniation (exception- therapeutic use of LP ro reduce ICP) infections- skin infections at puncture site may cause sepsis abnormal respiratory pattern- HTN with bradycardia and deteriorating consciousness, vertebral deformitites (scoliosis or kyphosis) in hands of an inexperienced clinician bleeding diathesis- coagulopathy, decreased platelet count (<50 x 10/L)
Glasgow Coma Scale
3 is the worst
15 is the best
eye opening, motor response, verbal response
bottom line for CSF
it should be examined in every patient inwhom the clincal finsings are consistent with even the possibility of meningitis, no matter how minimal the manifestations are
Examine the CSF for: pressure, appearance (clear or turbid), wet mount, gram stain (for bacteria), Geimsa stain (for presence of neutrophils or lymphocytes or RBC’s)
