Meningitis and Encephalitis

Question 1

CM

Why is bacterial meningitis considered a medical emergency?

Answer 1

High mortality and morbidity can result

Question 2

CM

Common pathogens for bacterial meningitis

(adults, children, neonates)

Answer 2

Adults: S. pneumo (70%), also H. flu and N. meningitidis

Children: N. meningitidis

Neonates: Group B Streptococcus

Question 3

CM

How are vaccinations changing bacterial meningitis epidemC

Answer 3

Decreasing the incidence of disease

The population affected is shifting to include more adults because more vaccinations

There are vaccines available against S. pneumo, H. flu, and N. meningitidis

Question 5

CM

Risk Factors for Bacterial Meningitis

Answer 5

General

• Exposure
• travel to endemic areas - meningitis belt in Subsaharan Africa
• Respiratory tract infection
• IVDU
• Penetrating head trauma
• Neurosurgery
• Devices - shunt, cochlear implants

Question 6

CM

Pathophysiology of bacterial meningitis

Answer 6

1. Infections break down blood brain barrier and enter brain
2. Inflammation of meninges–>Meningeal Signs, Neuro complications
3. Cerebral Edema
   
   • blood-brain barrier injury - pressure balances are off adn can lead to brain stem herniations
   • cytotoxins
   • inflammation impedes reabsorption of CSF

Question 7

CM

Meningeal Signs

Answer 7

• Nuchal Rigidity - stiff neck
  
  • indicated by decreased neck flexion - can’t touch chin to chest
• Kernig’s sign
  
  • flexion hip to 90 degrees and pt doesn’t allow knee extension
• Brudzinski’s sign
  
  • flex head and hip comes up (tuck into a ball)

Question 8

CM

Signs of Increased ICP

Answer 8

Mild/Moderate

• HA
• confusion
• irritability
• nausea/vomiting

Severe

• altered mental status
• Cushing reflex - increased BP and decreased pulse

Question 9

CM

Neurological complications from bacterial meningitis

Systemic signs

Answer 9

Neuro complications

• seizures
• focal neurological deficits
  
  • CN palsy - III, IV, VI, VII
  • monoparesis, hemiparesis, quadriparesis
  • visual field defects
  • aphasia
  • ataxia
• cerebrovascular
  
  • thrombosis, vasculitis, acute cerebral hemorrhage, aneurysm
• Sensorineural hearing loss
  
  • damage to CN VIII
  • late, common complication
• Cognitive impairment

Systemic Signs

• fever
• ill appearing
• pericarditis
• arthritis
• septsis/septic shock
• ARDS
• N. meningitidis: rash, arthritis
• meningococcemia rash

Question 10

CM

Classic Clinical Presentation

Answer 10

Classic triad

• fever
• nuchal rigidity
• change in mental status (less common)

+ Headache - severe and generalized

Symptoms

• fever
• HA
• neck stiffness and pain
• decreased consciousness
• N/V
• photophobia
• backache
• seizures

Question 11

CM

Labs - bacterial meningitis

Answer 11

Definitive test: Lumbar Puncture

Blood cultures positive in 50% of pts

CBC: leukocytosis, thrombocytopenia

electrolytes, BUN, Cr, Glucose

Question 12

CM

Lumbar Puncture

General

Answer 12

Indications

• infection
• CNS malignancy
• other neuro illnesses

Complications

• post LP HA
• infection
• bleeding
• cerebral herniation
• back pain
• minor neurological sxs

Method

• pt upright or in lateral recumbant position
• spine flexed
• needle inserted at L3/4 or L4/5 (iliac crest at level of L4)
• usually can safely remove 8-15mls

Routine tests on CSF

• opening pressure with manometer
• clarity and color
• cell count and differential
• glucose
• protein

Special tests

• Gram stain
• bacterial culture
• viral culture
• fungal culture
• PCR
• cytology

Question 13

CM

Meningitis LP Results

Answer 13

Opening pressure elevated

Cloudy CSF

WBC >2000, neutrophils >80%

protein elevated

glucose lowered

Question 14

CM

Treatment - bacterial meningitis

Answer 14

Supportive Therapy + antibiotics + dexamethasone

Question 15

CM

Aseptic Meningitis

• Etiology
• Pathophys
• Sxs
• Labs
• Tx

Answer 15

Clinical and lab evidence for meningeal irritation with negative bacterial cultures

Etiology

• MC’ly viral - enterovirus (MC), HSV 2 (most dangerous + genital symptoms common preceding meningitis)
• aseptic meningitis MC than bacterial
• Bacterial aseptic meningitis - TB, syphilis

Pathophysiology

• virus enters mucus membranes in respiratory or GI tract –> replicate in regional lymph nodes –> viremia
• When doing PE look for things suggestive of etiology

Symptoms

• Generally fewer neuro sxs, less acute in onset and progression, and better survival than bacterial
• Viremia:
  
  • nonspecific viral sxs: fever, HA, malaise, myalgia, anorexia, N/V, viral exanthem
• Meningeal signs
• focal neurological deficits less common

Labs

• LP: WBC and protein slightly elevated, nl glucose
• PCR if suspect etiology
• viral culture

Treatment

• symptomatic tx - can be outpt

Question 16

CM

Encephalitis

Etiology
Sxs
PE
Tests

Answer 16

Inflammation of brain parenchyma itself

Etiology

• MC - West Nile Virus
• Most dangerous - HSV

Sxs

• abnormalities in brain function
• AMS - confused, agitated, obtunded
• seizures
• motor or sensory deficits
• altered behavior and personality
• speech or movement disorders
• focal deficits of meningitis (hemiparesis, flaccid paralysis, paresthesias, CNS deficits
• lack meningeal signs
• fewer nonspecific signs and sxs
• may have signs outside of CNS of specific virus

PE

• no pathognomonic signs
• altered mental status
• focal neurological deficits
• West Nile Virus - flaccid paralysis, maculopapular rash, tremors

Tests

• consider PCR
• may look like viral meningitis on LP
• CT to r/o space occupying lesions or brain abscess
• EEG often abnormal
• Brain bx is last res

Question 17

CM

HSV Encephalitis

Answer 17

Fatal but treatable form of encephalitis

Hemorrhagic encephalitis ==> LP with RBCs in the absence of traumatic tap

Temporal lobe focality in sxs, signs, or imaging

Respiratory sxs followed by encephalitis sxs

Empiric therapy with acyclovir