Bacterial meningitis differential diagnosis

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Aysha Anwar, M.B.B.S[2]

Differential diagnosis

Bacterial meningitis may mimick other diseases in terms of clinical signs and symptoms. It is important to differentiate meningitis from other diseases with similar presentation. Once the diagnsis of meningitis is confirmed, the next step may be to differentiate different types of meningitis on the basis of CSF examnination:

Differentiating bacterial meningitis from other diseases

Diseases	Diagnostic tests				Physical Examination					Symptoms			Past medical history	Other Findings
	Na+, K+, Ca2+	CT /MRI	CSF Findings	Gold standard test	Neck stiffness	Motor or Sensory deficit	Papilledema	Bulging fontanelle	Cranial nerves	Headache	Fever	Altered mental status
Brain tumour Determination of creatine kinase BB and carcinoembryonic antigenhelps in differentiating.		✔	Cancer cells	MRI		✔	✔	✔	✔	✔		✔		Cachexia, gradual progression of symptoms
Delerium Tremens		✔		Clinical diagnosis		✔	✔		✔	✔	✔	✔	Alcohal intake, sudden witdrawl or reduction in consumption	Tachycardia, diaphoresis, hypertension, tremors, mydriasis, positional nystagmus, tachypnea
Subarachnoid hemorrhage		✔	Xanthochromia	CT scan without contrast	✔	✔	✔	✔	✔	✔	✔	✔	Trauma/fall	Confusion, dizziness, nausea, vomiting
Stroke		✔	Normal	CT scan without contrast		✔	✔		✔	✔		✔	TIAs, hypertension, diabetes mellitus	Speech difficulty, gait abnormality
Neurosyphilis		✔	↑ Leukocytes and protein	CSF VDRL-specifc CSF FTA-Ab -sensitive	✔	✔	✔	✔		✔		✔	Unprotected sexual intercourse, STIs	Blindness, confusion, depression, Abnormal gait
Viral encephalitis		✔	Increased RBCS or xanthochromia, mononuclear lymphocytosis, high protein content, normal glucose	Clinical assesment	✔	✔	✔		✔	✔	✔	✔	Tick bite/mosquito bite/ viral prodome for several days	Extreme lethargy, rash hepatosplenomegaly, lymphadenopathy, behavioural changes
Herpes simplex encephalitis		✔		Clinical assesment			✔	✔	✔	✔	✔		History of hypertension	Delirium, cortical blindness, cerebral edema, seizure
Wernicke’s encephalopathy			Normal				✔	✔			✔		History of alcohal abuse	Ophthalmoplegia, confusion
CNS abscess		✔	↑ leukocytes >100,000/ul, ↓ glucose and ↑ protien, ↑ red blood cells, lactic acid >500mg	Contrast enhanced MRI is more sensitive and specific, Histopathological examination of brain tissue	✔	✔	✔		✔	✔	✔	✔	History of drug abuse, endocarditis, ↓ immune status	High grade fever, fatigue,nausea, vomiting
Drug toxicity											✔	✔		Lithium, Sedatives, phenytoin, carbamazepine
Conversion disorder				Diagnosis of exclusion		✔		✔		✔	✔	✔		Tremors, blindness, difficulty swallowing
Electrolyte disturbance	↓ or ↑			Depends on the cause						✔		✔		Confusion, seizures
Febrile seizures			Not performed in first simple febrile seizures	Clinical diagnosis and EEG					✔	✔	✔	✔	Family history of febrile seizures, viral illness or gastroenteritis	Age > 1 month,
Subdural empyema		✔		Clinical assesment and MRI	✔	✔	✔	✔	✔			✔	History of relapses and remissions	Blurry vision, urinary incontinence, fatigue
Hypoglycemia	↓ or ↑			Serum blood glucose HbA1c		✔				✔		✔	History of diabetes	Palpitations, sweating, dizziness, low serum, glucose

Differentiating bacterial meningitis from other causes of meningitis

Cerebrospinal Fluid
	Normal Levels	Acute Bacterial M.	Acute Viral M.	TB M.	Neuroborreliosis
Cells/ul	< 5	In the 1000s	In the 100s	In the 100s	Some 100
Cells	Lymph:Monos 7:3	Gran. > Lymph.	Lymph. > Gran.	Various leukos	Lymph. monocytic
Total Protein (mg/dl)	45-60	Typically 100-500	Typically normal	Typically 100-200	Typically up to 350
Glucose Ratio (CSF/plasma)	Typically > 0.5	< 0.3	> 0.6	< 0.5	Normal
Lactate (mmol/l)	< 2.1	> 2.1	< 2.1	> 2.1	-
Others	ICP: 6-22 (cm H2O)		PCR of HSV-DNA	PCR of TBC-DNA	IgG/IgM CSF/Serum Ratio

References

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