CNS/Opthalmic Infections Flashcards
3 causes of bacterial meningitis in the neonate
- E. coli
- GBS
- Listeria monocytogenes
Common causes of viral meningitis
- Enteroviruses (coxsackieviruses, echoviruses)
2. Herpesviruses
Causes of bacterial meningitis in adults
- S. pneumoniae
- N. meningitidis
- H. influenzae
Patho of bacterial meningitis
- Nasopharyngeal colonization
- Local invasion
- Bacteremia
- Endothelial cell injury
- Increased BBB permeability + meningeal invasion
- Subarachnoid space inflammation -> cerebral vasculitis
- Problems
Complications of bacterial meningitis
- Edema (vasogenic, interstitial, cytotoxic) results in increased ICP
- Increased ICP leads to decreased cerebral blood flow –> death
- Cerebral vasculitis can cause cerebral infarction, which may also decrease cerebral blood flow, causing death
Classic triad of meningitis
- Fever
- Neck stiffness
- Headache
Clinical Sx associate with meningitis
- Photophobia
- N/V
- Petechial rash = meningococcal meningitis
- Neurological symptoms (seizures etc.)
Findings suggestive of meningitis on physical exam
- Fever
- Petechial rash
- Neck stiffness
- Kernig sign
- Brudzinski sign
- Increased headache with jolt
- Cranial nerve palsies
What is Kernig’s sign?
Resistance or pain in lower back or posterior thigh when the knee is extended (when hip flexed to 90 degrees)
What is Brudzinski’s sign?
When passive neck flexion in the supine pt results in flexion of the knees and hips
What is papilledema?
Blurring of the edges of the optic disk, which indicates increased ICP
What investigations might you perform for suspected meningitis?
- LP to obtain CSF for: WBC diff, protein, glucose, Gram stain, culture
- CT or MRI head
When is a head CT indicated prior to doing a LP?
Concerned about increased ICP, where LP leads to cerebral herniation and death
- Immunocompromised state
- Focal neuro deficits
- Hx of CNS disease
- New onset seizures
- Papilledema
- Altered LOC
Tx of meningitis
- Start antibiotics ASAP
- If LP delayed, do blood cultures and start antibiotics
- Empiric Tx = Ceftriaxone + Vancomycin
- Can also add Ampicillin and/or dexamethasone
What is the prognosis for meningitis?
- Overall 15% mortality
2. 28% have neuro complications
What differentiates meningitis from encephalitis?
Encephalitis presents with brain function abnormalities, such as:
- Altered LOC
- Motor or sensory deficits
- Change in behaviour/personality
- Speech or mvmt disorder
Infectious causes of encephalitis
- Viral: HSV-1 (life threatening), VZV, other herpes viruses, Arboviruses, Enteroviruses, Measles
- Non-viral: tick-borne, bacteria, protozoa
Clinical presentation of encephalitis
- Fever
- Headache
- Altered mental status
- Seizures
- +/- rash
Dx approach to encephalitis
- LP and CSF analysis (culture, WBC, protein, glucose)
- PCR the CSF sample
- Serology for Arboviruses
- Brain biopsy as last resort
- CT head or MRI
- EEG
Tx for encephalitis
- Acyclovir IV
Risk factors for a brain abscess
- Immunosuppression
- Chronic cardiopulmonary conditions
- Penetrating head trauma
Cause of brain abscess
- Immunocompetent = polymicrobial
2. Immunocompromised = Toxoplasmosis, Cryptococcus, TB
Clinical presentation of brain abscess
- Headache
- Fever
- Focal neuro deficits - dependent on location in brain affected
- Change in mental status
- Seizures
- N/V
- Neck stiffness
How to Dx a brain abscess
- CBC - normal WBC
2. CT scan with contrast or MRI
Tx for brain abscess
- Aspiration
- Ceftriaxone + Metronidazole +/- Vancomycin, OR
- Meropenem +/- Vancomycin
- Dexamethasone when significant swelling
Risk of epidural abscess?
Can expand and compress the spinal cord, leaving neuro complications
Risk factors for epidural abscess
- Manipulation of epidural space
- Spread from other infection
- IVDU
- DM, alcoholism, HIV
- Trauma
Top 4 causes of epidural abscess
- S. aureus
- Gram -ve bacilli
- Streptococci
- CNS
Patho of epidural abscess
Damage to spinal cord from:
- Direct compression
- Cutting of blood supply
- Bacterial toxins and inflammatory mediators
Clinical presentation of epidural abscess
Initially non-specific (fever and malaise)
Classic triad = Fever, back pain, neuro deficits
Progression of untreated epidural abscess
Back pain -> nerve root pain -> motor weakness, sensory changes, bladder or bowel dysfunction -> paralysis