Following the medical history and physical/neurological examinations, TCH patient are evaluated by unenhanced CT of the brain. If a diagnosis cannot be established by a brain CT, a lumbar puncture is then performed (if there are no contraindications) (1).
- brain CT without contrast
- is the study of choice in the detection of subarachnoid haemorrhage (SAH)
- should be carried out as soon as possible to maximize sensitivity (preferably within 12 hours of onset.)
- sensitivity of CT SAH drops from 98% at 12 hours to 93% by 24 hours (1)
- in addition unenhanced CT of the brain may indicate other aetiologies
- intracerebral/intraventricular haemorrhage
- acute subdural haemorrhage
- brain infarct (after three hours)
- tumour (third ventricle colloid cyst, posterior fossa tumour)
- hydrocephalus (aqueductal stenosis, Chiari type 1 malformation)
- acute sinusitis (exclusion diagnosis)
- lumbar puncture (LP)
- performed in patient with normal CT of the brain
- the following studies are recommended
- if bloodstained, it should immediately be centrifuged to visualize xanthochromia (bilirubin and oxyhaemoglobin) of the supernatant which indicates SAH
- spectrophotometry -
- some recommends that LP should be carried out 12hours after headache onset to differentiate traumatic taps from SAH. This is controversial since it leads to delay in treatment or early rebleeding in those with a ruptured aneurysm
- opening pressure - high pressure may indicate cerebral venous thrombosis
- while low pressure can be due to intracranial hypotension
- white and red blood cell counts, Gram staining, protein and glucose concentrations
There is conflicting opinions on further investigations in patients with normal CT and LP results.
- causes that may present with normal CT and normal or near normal cerebrospinal fluid includes:
- dissection of cervical arteries (extracranial, intracranial, carotid, or vertebral)
- reversible cerebral vasoconstriction syndrome
- pituitary apoplexy
- symptomatic aneurysm with mass effect (painful third nerve palsy)
- additional testing often includes
- brain MRI
- magnetic resonance angiography (MRA)
- computed tomographic angiography (CTA) (1)
Reference: