Meningitis

Question 1

Meningitis

Answer 1

• An inflammatory disease of the leptomeninges (inner 2 meninges - arachnoid and pia matter)

Question 2

Meninges

Answer 2

• Tissues surrounds the brain and spinal cord (dura matter, arachnoid matter, and pia matter).

Question 3

Pathophysiology of the meningitis

Answer 3

• Most meningeal infections are due to infectious agents that has colonized or established a local infection in the host. The agent may first colonize another area of the body (skin, respiratory tract, GI tract, genitourinary tact, etc) before gaining entery to the meninges via:
  
  • Invasion of the bloodstream followed by hematogenous seeding of the CNS
  • A retrograde neuronal pathway
  • Direct continguous spread - sinuitis, otitis media, congential malformations, trauma, etc.
• Once bacteria and other organisms find there way into the brain they are somewhat isolated from the immune system due to the BBB, allowing them to spread. This means that when the body tried to fight the infection the problem can worsen - blood vessels become leaky adn allow fluid, WBC, and other infection fighting particles to enter the brain. This can lead to brain swelling and decreased blood flow to parts of the brain.
• Depending on severity the inflammatory process may stray confined to the subarachnoid space. In more severe forms, the pia matter is inflitrated and it may lead to cortica destruction.

Question 4

Bacterial Meningitis

Answer 4

• Infection of arachnoid matter and CSF in both the subarachnoid space and cerebral ventricles (system of four interconnected cavities in the brain where CSF is produced).

Question 5

Epidemology bacteria meningitis

Answer 5

Can be community acquried or healthcare associated

• Community acquried
  
  • Streptococcus penumoniae (Gram + cocci)
  • Neisseria Meningitidis (Gram - diplococci)
  • Listeria monocytogenes (Gram + bacilli)
• Healthcare associated
  
  • Staphylococci
  • Aerobic gram negative bacilli

Question 6

Clinical Features Meningitis

Answer 6

• Classic triad
  
  • Fever (>38)
  • Nuchal rigidity
  • Change in mental status
• Headache - described as severe and generalized
• Neurologic complication
  
  • Seizures
  • Focal neurologic defivitis
  • Papilledema

Question 7

Investigations Meninigitis

Answer 7

• CBC - WBC count is usually elevated with a shifft towards immature form. However, in severe infection you may see leukopenia
• Blood cultures - often positive and useful in CSF cannot be obtained before start of antibotics
• Lumbar Puncture - crucial for making diagnosis and identifying the causative organism
  
  • In certain cases you may need to do a CT scan before LP to exclude mass lesion or increased intracranial pressure which may result in cerebral herniation if LP is preformed.
• CSF analysis - gram stain and culture to differentiate between bacterial and biral

Question 8

Treatment Bacterial Meningitis

Answer 8

• There are 3 requirements for antibiotic agents in bacterial meningitis
  
  1. Use of bactericidal (kills bacteria rather than just slowing down growth) drugs effective against the organism
  2. Drugs must be able to enter the CSF (BBB prevents macromolecule entry into CSF)
  3. Structuring regiment to optimize bactericidal efficacy based on pharmocodynamic characteristics of the antimicrobial agents
• Dexamathasone - used to reduce risks of certain complications such as hearing loss, neurologic complications, and mortality
• Supportive care - management of fluid and electrolyte balance

Question 9

Aspetic Meningitis

Answer 9

• Patients who have clinical and laboratory evidence for meningeal inflammation with negative routine bacterial culture
• Most common causes are enteroviruses, but can also be due to other infections (fungal), medications, and malignancies
• Often has similar presentation to bacterial, however, aseptive tends to resolve without specific therapy

Question 10

Treatment Aspetic Meningitis

Answer 10

• Generally, treatment is supportive - rests, acetaminophen (don’t given aspirin in children due to association with Reye syndrome - swelling in the liver and brain following recovery from viral infection), IV fluid if patient is hypovolemic from vomiting
• If the etiology of the meningitis is unclear you should give the patiet antibiotics after obtaining blood and CSF culture.

Question 11

Preparation of Lumbar Puncture

Answer 11

• Find level of entry - with patient sitting upright or standing locate the highest point of the iliac crest via palpation - moving medially from this point is a god guide to L4. Spinal needle can be safely inserted into the subarachnoid space at L3/4 or L4/5 since this is well below the termination of the spinal cord (L1-L2).
• Postition - Patient should be in the fetal position with neck, back, and limbs in flexion. Lower lumbar spine should be flexed with bakc perfectly perpendicular to the edge of the bed. Hips and legs should be parallel to each other and perpendicular to the table.
• Cleaning - skin should be cleaned with alcohol and a disinfectant and allowed to dry
• Anesthetic - lcoal anesthetic lidocaine should be administed to the area

Question 12

Procedure Technique Lumbar Puncture

Answer 12

• Needle is inserted slowly at L3/4 or L4/5, angled slightly toward the head. The flat surface of the bevel of the needle should face the flank to allow the needle to spred rather than cut the dural sac.
• Distance from the skin to the epidural space is 45-55mm. many choose to advance incrementally and check for CSF flow, continuning this until the subarachnoid space is reached. Once fluid starts to flow, patient shouold slowly straighten legs to allow free flow to CSF.

Question 13

Complications of Lumbar Puncture

Answer 13

• Post LP headache - occurs in 10-30% of patients and is the most common complication. Caused by leakage of CSF from dura and traction on pain-sensitive structures. Headache is worse in upright position and improved in supine.
• Infection
• Bleeding
• Cerebral herniation - increase risk in patients with increased intracranial pressure
• Minor neurologic symptoms such as radicular pain or numbness
• Late onset of epidermoid tumors of thecal sac
• Back pain

Question 14

Spleen Anatomy

Answer 14

Question 15

Role of the Spleen

Answer 15

• White Pulp
  
  • Ingests bacteria and other harmful substances (removes antibody coated cells/particles)
  • Contains T cells (periarteriolar lymphoid sheat), B cells (follicles), and macrophages (marginal zone) that plays an important role in immune function - recognizes MHC, produces antibodies, phagocytozes substances, etc.
• Red pulp
  
  • Filters abnormal/old RBCs
  • Recycles irons
  • Metabolizes hemoglobin (globin is broken down into amino acids and heme is metabolied to bilirubin, which is removed from the liver).
• General
  
  • Stores blood and platelets