MENINGITIS

Meningitis

Causes:

Infectious	Non Infectious
Viral § Commonest cause § Usually benign and self-limiting § Complete recovery w/o specific Rx is the norm. § Common organisms: echoviruses, mumps. Less commonly HSV & zoster, coxsackie Bacterial – high mortality & morbidity Fungal	malignancies, autoimmune diseases eg. SLE drugs (NSAIDS, trimethoprim)

Causes of bacterial meningitis by population groups:

Neonatal – 3months	1. Group B strep 2. Gram negative bacilli (E coli, proteus) 3. Listeria monocytogenes
Pre-school child	1. H. influenzae 2. N. meningitides 3. Strep. Pneumoniae 4. M. TB
Older child / Adults	1. N. Meningitidis 2. Strep. Pneumoniae 3. M. TB
Elderly / DM/ debilitated	1. Strep. Pneumoniae 2. N. Meningitidis 3. H. influenzae 4. L. monocytogenes 5. M. TB
Immuno-compromised	1. Strep. Pneumoniae 2. N. Meningitidis 3. H. influenzae 4. L. monocytogenes 5. C. Neoformans 6. Toxoplasma gondii 7. S. aureus

§ Meningococcus: Spread by air-borne route. May result in meningococcaemia.

~ Cxs of meningococcaemia: meningitis, purpuric rash, shock, DIVC, renal failure, peripheral gangrene, arthritis (rxtive or septic), pericarditis (rxtive or septic)

§ H. influenzae: a/w ottitis media

§ Pneumococcus: a/w ottitis media and pneumonia, esp in elderly, alcoholics & immunocompromised.

§ TB: chronic or acute on chronic, a/w chronic headache, isolated CN6 palsy due to ­ICP, and S/S of TB eg fever, nightsweats.

Risk factors:

Environment	Overcrowded closed communities, schools, day care centres
Head injury	skull #, cranial or spine surgery
Septic site	pneumonia, mastoiditis, sinusitis, OM
Host	Complement or antibody deficiency Immunosuppression (CA, AIDS, hyposplenism, sickle-cell dz, hypogammaglobinaemia, DM
Foreign body	§ CSF shunt/ VP shunt (prone to staph. Meningitis)

Pathophysiology

Meningeal infection followed by bacteriemia

Host response to infection

Release of inflammatory mediators/ activated leucocytes

Endothelial damage

Cerebral edema/ raised ICP/reduced cerebral blood flow

DDx:

1. Any acute infections eg malaria

2. Local infections causing neck stiffness

3. Encephalitis

4. Subarachnoid hemorrhage

S/S:

Meningism	§ Headache § Photophobia § Neck stiffness	§ Kernig’s sign § Brudzinski’s sign (hip flexion on flexion of neck) § Opisthotonus
­ ICP	§ Headache § Vomiting § Irritability § Drowsiness § ¯consciousness/coma § Focal neuro signs	§ Fits § Bulging of fontanelle § Cushing’s reflex: ­BP & ¯pulse § Irregular respiration § Papilloedema
Septicaemia	§ Malaise § Fever § Rash – petechiae/purpura suggests meningiococcus.	§ DIC § ¯BP, ­pulse, tachypnoea § Arthritis § Odd behaviour

ComplicationS

Acute	chronic
· Seizures · Cerebral herniation · Increase in ICP · Cranial nv palsies · Subdural effusions ( H.influenza/strep.pneumonia) · Thrombosis of subdural sinuses · SIADH · Waterhouse Frederickson syndrome	· Neurological deficit · Deafness (damage to cochlear hair cells) · Aphasia · Ocular palsies · Cerebral palsy · Mental retardation · Brain abscess · Hydrocephalus/microcaphaly · Epilepsy · Diabetes insipidus

Investigations:

Blood	Full Blood Count		leukocytosis
	Blood C/S		find the specific organism
	Acute Phase Reactants (CRP/ESR)
	BUSE/ creatinine		SIADH
	Random Blood Glucose		for CSF glucose result interpretation
	DIVC screen		Especially if meningococcaemia is suspected
	LFT
Urine Urine	UFEME		UTI
	Urine C/S
Lumbar puncture CSF	§ Exclude ­ ICP by CT head, fundoscopy & clinical signs. § Tubes Cell count, cytospin for cell and differential count Protein & glucose Microbiology – gram stain, C&S, AFB smear, TB culture, Indian ink stain, fungal culture Cryptococcal antigen, bacterial antigens (S. pneumonia, N. meningitides, H. influenzae, GBS) Latex agglutination for bacterial antigens PCR ( herpes simplex)
CT head	Indications for CT scan in Meningitis (Mainly useful to detect complications) - Prolonged depression of consciousness - Prolonged focal or late seizures - Focal neurological abnormalities - Enlarging head circumference - Suspicious of subdural effusion or empyema Exclude ­ICP (eg cerebral abscess, head injury, brain tumour) pre-LP. Cerebral odema Hemorrhage Typical site of virus
CXR	If susupected TB

Contra indication for lumbar puncture

• GCS<= 8
• Cardiorespiratory instability
• Increased in ICP

- Coma

- High BP

- Reduced HR

- Papilodema

- Tense fontanelle

• Focal neurological signs
• Caogulopathy
• Thrombocytopenia
• Local infections at the site of LP

Typical CSF in meningitis

	Normal	Pyogenic	TB	Viral (‘aseptic’)
Appearance	clear	Turbid	Fibrin web forms on standing	Clear
Predominant cell		Neutrophils	Lymphocytes	Lymphocytes
Cell count/ mm3	0-5/mm3	90-1000+	10-1000	50-1000
Glucose	> 50% blood	¯ (< 1/2 plasma)	¯ (< 1/2 plasma)	N (> 1/2 plasma)
Protein (g/L)	0.15-0.4	­ (>1.5)	­ (1-5)	N (<1)
Culture / smear		Positive	Usually not seen	Negative

Treatment:

§ Monitoring: BP, pulse, RR, temp, SpO₂, conscious level

§ Supplemental O₂

§ ABx if bacterial (see below)

§ Antipyretics and antiemetics

§ Corticosteroids for ­ICP (controversial): 0.15mg/kg dexamethasone

Viral

§ Supportive treatment

§ Completer recovery without specific therapy is the norm.

Bacterial

§ IV penicillin stat on suspicion of bacterial meningitis

§ Modify ABx regimen according to CSF invx results

Meningococcal	Benzyl penicillin (2.4g/4hr slow IV)
Pneumococcal	Ceftriaxone (2g/12 hrly IV)
H. influenzae	Ceftriaxone
GBS/ Gram negative bacilli	Ceftriaxone + Gentamicin + ampicillin (50mg/kg/6 hr IV)
L. monocytogenes	Gentamicin + ampicillin
M TB	Pyrazinamide, isoniazid, rifampicin, ethambutol 6-12 mths
C. neoformans	Amphotericin + flucytosine

§ Treatment for pyogenic meningitis of unknown cause

Neonate	Ampicillin + Ceftriaxone or gentamicin
Infant	Ampicillin + Ceftriaxone
Pre-school child	Ceftriaxone
Older child / adults	Penicillin G (400K units/kg/day) + Ceftriaxone
Elderly (>50YO)	Ampicillin + Ceftriaxone

§ Prophylaxis for close contacts--meningococcus:

~ Children: 2 days of oral rifampicin (3-12mths 5mg/kg 12 hrly; >1yr 10 mg/kg 12 hrly)

~ Adults: single dose of 500mg ciprofloxacin OR rifampicin 600mg 12 hrly for 2 days.

§ Vaccination: available for groups A & C meningococci, but not group B.