Differentials
Brain metastasis
SIGNS / SYMPTOMS
May or may not have systemic disease and/or known history of cancer.
Systemic symptoms may include cachexia, respiratory problems, haemoptysis, chest pain, and bone pain.
INVESTIGATIONS
MRI: typically, more localised lesions that may be multiple, and with proportionally more vasogenic oedema.
Chest-abdominal CT scan, bone scan, and PET scan provide evidence of systemic disease.
Histology provides a definitive diagnosis.
Brain abscess
SIGNS / SYMPTOMS
May or may not have systemic symptoms such as fever, cachexia, and chills.
Risk factors differ and may include pulmonary abnormalities, congenital cyanotic heart disease, bacterial endocarditis, and penetrating head injury.
INVESTIGATIONS
MRI demonstrates a thinner capsule toward the ventricle, with restricted diffusion of pus and elevated lactate level; may show multiple lesions.
Blood tests suggestive of infection: for example, elevated WBC count, elevated erythrocyte sedimentation rate, and elevated C-reactive protein, with sensitivity 90% and specificity 77%.[37]
Biopsy or aspiration provides the definite diagnosis, demonstrating pus (inflammatory cells), no tumour cells, and a positive culture of bacterial agent or fungus.
Multiple sclerosis
SIGNS / SYMPTOMS
Typically presents in women aged 20-40 years, with acute neurological symptoms that wax and wane (dissemination in space and time): for example, optic neuritis, transverse myelitis (spinal cord symptoms), and focal neurological symptoms.
Although rare, glioma may occur in patients with multiple sclerosis.[38]
INVESTIGATIONS
MRI shows multiple lesions in the periventricular white matter; may or may not enhance.
Cerebrospinal fluid shows oligoclonal bands.
Histology provides the definitive diagnosis, demonstrating demyelinating lesions, inflammatory cells, and absence of tumour cells, but usually is not necessary.
Necrosis
SIGNS / SYMPTOMS
Known brain tumour treated with radiotherapy in the past.
May present with progressive neurological symptoms or no symptoms at all.
INVESTIGATIONS
PET scan is cold. MR perfusion with decreased cerebral blood volume (relative CBV).
Histology provides definitive diagnosis (no tumour cells and extensive necrosis).
Acute stroke
SIGNS / SYMPTOMS
Acute onset of neurological symptoms.
Often in older patients with cardiovascular risk factors.
Rarely present with seizures (3% to 5% only).
INVESTIGATIONS
MRI shows typical vasculature distribution and restricted diffusion.
Of note, subacute strokes may exhibit contrast enhancement.
Encephalitis
SIGNS / SYMPTOMS
Systemic symptoms present (fever and cachexia).
INVESTIGATIONS
Cerebrospinal fluid shows leukocytosis, herpes simplex virus antibodies, and/or red blood cells.
Electroencephalogram is characteristic with periodic lateralising epileptiform discharges.
CT or MRI shows oedematous temporal lobes and haemorrhagic transformation.
Brain biopsy is definitive with virus isolation.
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