CNS infections Flashcards
CT head
Required prior to LP (to exclude ↑ ICP) if: • GCS <8 • Focal neurological signs • Previous CNS pathology • Immunocompromise May show abscess, meningeal enhancement
MRI head
Greater definition than CT
May show encephalitis, meningeal enhancement
Acute meningitis clinical presentation
Headache Fever Nausea Vomiting Photophobia Confusion Coma Rash - non-blanching
Acute meningitis causes
Bacterial
Viral
Protozoa: Naegleria fowleri, acanthamoeba
Non-infective: SLE, seizures, migraines, post vaccination
Bacterial meningitis
Infection usually begins in the nasopharynx with colonisation by a new pathogenic bacteria → systemic invasion
Splenectomy, complement deficiency and base of skull fracture all predispose
Bacterial causes and treatment 0-4 weeks
Gp B strep E coli L monocytogenes K pneumoniae Salmonella Antibiotic: amoxicillin and cefotaxime
Bacterial causes and treatment 4-12 weeks
Gp B strep E coli L monocytogenes K pneumoniae Salmonella N meningitides S pneumoniae H influenzae Antibiotic: amoxicillin and cefotaxime/ceftriaxone
Bacterial causes and treatment 3 months - 18 years
N meningitis
S pneumoniae
H influenzae
Antibiotic: Cefotaxime/ceftriaxone
Bacterial causes and treatment 18 - 50 years
N meningitides
S pneumoniae
Antibiotic: cefotaxime/ceftriaxone
Bacterial causes and treatment >50 years
S pneumoniae
N meningitides
L monocytogenes
Antibiotic: amoxicillin and cefotaxime/ceftriaxone
Bacterial meningitis CSF
Cells ↑ >100 (usually neutrophils)
Protein ↑ >1g/ml
Glucose ↓ <40% of serum levels
Viral CSF
Cells ↑ 5 - 200 (often lymphocytic)
Protein ↑ 0.5-1g/ml
Glucose normal
TB/fungal CSF
Cells ↑ 5-200 (lymphocytes)
Protein ↑ >1g/ml
Glucose ↓
Antibiotics by organism
H. influenzae: ceftriaxone or cefotaxime 7 days
N meningitides: ceftriaxone or cefotaxime 7 days
S pneumonia: ceftriaxone or cefotaxime 10-14 days
L monocytogenes: amoxicillin 21 days
Gp B strep: amoxicillin 14-21 days
Viral meningitis causes
Enteroviruses Arboviruses Mumps Herpes HIV
Viral meningitis clinical features
Enterovirus: fever, headache, neck stiffness, photophobia
Mumps: CNS symptoms 5 days after onset of parotitis
HSV2: may occur as primary infection without genital lesions
HIV: usually part of primary infection
Viral meningitis diagnosis
Characterised by lymphocytes in CSF
Viral culture rarely used
Serology - IgM Ab of enteroviral infection
PCR on CSF for HSV, VZV, enterovirus and mumps
Viral meningitis treatment
Mostly supportive
HSV - acyclovir IV 10mg/kg for 14-21 days
HIV - consider antiretrovirals
Encephalitis causes
HSV CMV EBV HHV-6 HHV-7 Arboviruses (tick-borne encephalitis, west nile virus, St Louis encephalitis, Japanese B encephalitis, equine encephalitis) Rabies Mumps Measles HIV
Encephalitis clinical features
Irritability Altered personality Drowsiness Ataxia Excessively brisk tendon reflexes/upgoing plantars Signs of cerebral or brainstem failures Signs of brain swelling Fever +/- signs of meningitis
Encephalitis diagnosis
Viral culture rarely used
Serology - IgM Ab of enteroviral infection
PCR on CSF for HSV, VZV, enterovirus and mumps
Cerebral abscess aetiology
Otitis media/mastoiditis Sinusitis Dental sepsis Trauma/neurosurgery Pulmonary/pleural sepsis Endocarditis Congenital heart disease nb. organisms often mixed
Cerebral abscess clinical features
Headache Altered mental state Fever (50%) Seizures Nausea and vomiting Focal neurological deficits Papilloedema
Cerebral abscess diagnosis
CT MRI more sensitive Aspiration of lesion via Burr hole or craniotomy: • Culture • Cytology - exclude malignancy
Cerebral abscess treatment
Empirical: cefotaxime, amoxillin, metronidazole or meropenem
Ideally lesion drained in neurosurgery
MRSA +ve, add linezolid
