Brain abscess differential diagnosis

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

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Overview

Brain abscess must be differentiated from metastatic tumors, necrotic tumors, and lymphomas.

Differential Diagnosis

Brain abscess must be differentiated from:

• Metastatic tumors
• Necrotic tumors
• Lymphomas

Metastatic Tumor

• The big differential is that the abscess is often located in watershed regions, and tumors often enhance diffusely with contrast.

Necrotic Tumor

• Diagnosis of brain abscesses and necrotic tumors is often impossible without conventional MR imaging.
  • Several studies demonstrate the utility of Diffusion-weighted imaging (DWI) to differentiate between necrotic or cystic lesions and brain abscesses.
  • DWI has a sensitivity and specificity of over 90% for distinguishing abscess (low ADC) from necrotic tumors (high ADC).

Lymphoma

• Some studies suggest that indium scans can help differentiate abscess from CA, and thallium SPECT scans can distinguish CNS toxoplasmosis from lymphoma.

Despite these differences, the true diagnosis is sometimes not made until biopsy.

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
Delirium tremens		✔		Clinical diagnosis		✔	✔		✔	✔	✔	✔	Alcohol intake, sudden witdrawl or reduction in consumption	Tachycardia, diaphoresis, hypertension, tremors, mydriasis, positional nystagmus,
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 convulsion			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