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 meningite is 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		✔	Cancer cells	MRI	✔	✔	✔	✔	✔	✔				Cachexia, gradual progression of symptoms
Delerium Tremens		✔			✔	✔	✔	✔	✔	✔	✔	✔	Hypertension	Neck stiffness
Subarachnoid hemorrhage		✔	Xanthochromia	CT scan without contrast	✔	✔	✔	✔	✔	✔	✔	✔	Trauma/fall	Confusion, dizziness, nausea, vomiting
Neurosyphilis		✔	↑ Leukocytes and protein	CSF VDRL-specifc CSF FTA-Ab -sensitive	✔	✔	✔	✔		✔		✔	STIs	Blindness, confusion, depression, Abnormal gait
Encephalitis				Clinical assesment			✔			✔			Family history of migraine	Presence of aura, nausea, vomiting
Herpes simplex encephalitis		✔		Clinical assesment			✔	✔	✔	✔	✔		History of hypertension	Delirium, cortical blindness, cerebral edema, seizure
Wernicke’s encephalopathy							✔	✔			✔		History of alcohal abuse	Ophthalmoplegia, confusion
CNS abscess		✔	↑ leukocytes, ↓ glucose and ↑ protien	MRI is more sensitive and specific	✔	✔	✔			✔	✔		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			↑ Leukocytes, ↑ Protein ↓ Glucose	CSF analysis					✔	✔				Fever, neck rigidity
Subdural empyema		✔	↑ CSF IgG levels (monoclonal bands)	Clinical assesment and MRI	✔	✔	✔	✔	✔			✔	History of relapses and remissions	Blurry vision, urinary incontinence, fatigue
Seizure	↓ or ↑			Clinical assesment and EEG	✔					✔	✔		Previous history of seizures	Confusion, apathy, irritability,
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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