Always consider, whether the possible benefit from the investigation is greater than the harm to the patient due to radiation exposure.
Computed tomography (CT) is the easiest and most rapid method for identifying intracranial haemorrhages and for acute differential diagnosis between cerebral haemorrhage and infarction.
Magnetic resonance imaging (MRI) is the best method for the examination of the brain and the back. It is, however, slower than CT and not so easily available.
Carotid ultrasonography is a non-invasive and easily available first-line procedure for detecting carotid artery stenoses and changes in the arterial walls. It is often used when investigating the aetiology of disturbances of the cerebral circulation.
Usually the first examination especially in the investigation of cerebral events due to its rapidity and easy availability. If needed, it may be combined with angiography and perfusion study.
CT scan is often normal at the initial phase (< 3 hours) of acute cerebral infarction. It can be used to exclude cerebral haemorrhage before initiation of thrombolytic therapy.
Contrast medium enhancement adds accuracy to the diagnosis, if the disease process involves blood-brain barrier damage or abnormal neovascularisation, but MRI is often needed for further evaluation of the findings.
CT scan is not suitable for studying spinal canal processes unless information on bony structures is sought for.
CT angiography
High radiation exposure must be kept in mind.
Can be used for imaging of the carotid arteries e.g. when ultrasonography has aroused suspicion of stenosis and endarterectomy is planned.
Indications for emergency CT angiography
Fresh subarachnoid haemorrhage (CT angiography of the cerebral arteries)
Suspected sinus thrombosis (CT angiography of the venous sinuses)
Suspected carotid artery dissection
Critical/significant stenosis of the carotid artery detected by ultrasonography, if emergency endarterectomy is planned.
Produces image planes of different orientations and several different image types that help in the assessment of the changes.
The examination is targeted according to the problem. A well-formulated referral form is essential for a successful examination.
Well suited for longitudinal examination of the vertebral canal, and often yields more information on the brain than CT. Processes in the posterior cranial fossa and in the brainstem can only be excluded by MRI.
Contraindications
Pacemaker (nowadays not always an absolute contraindication) and other implanted electronic devices
Claustrophobia (sedation may be used if necessary)
Magnetic resonance angiography (MRA)
MRA can be used to visualize blood vessels. It is suited e.g. for screening for aneurysms in SAH families.
MRA of the carotid arteries is used in planning of endarterectomy if CT angiography is not feasible (e.g. in renal failure).
MRA of the cerebral arteries is used e.g. in suspected cerebral vasculitis or aneurysm.
Ultrasonography of carotid arteries
When the examination is performed by an experienced practitioner, the results correlate well with angiographic findings.
The procedure is used
as a screening method when looking for carotid artery stenoses in patients with disorders of the cerebral circulation
before coronary surgery when looking for possible symptomless carotid stenoses that may affect anaesthesia.
Digital subtraction angiography (DSA)
Sometimes neuroradiological angiographies require admitting the patient to the hospital.
Indications for carotid artery angiography
The planning of endarterectomy due to the stenosis of carotid artery is nowadays carried out by CTA or MRA. DSA is used in exceptional cases only (planning and execution of an endovascular procedure).
SAH, suspected aneurysm in exceptional cases (CTA is the primary method); treatment of the aneurysm by endovascular coiling
Investigation of the vascularisation of a known brain tumour or arterio-venous (AV) malformation before surgery. Endovascular treatment is usually performed in association with the investigation.
Indications for vertebral angiography
In principle these are the same as those for carotid angiography, when the lesion is located in the region of vertebrobasilar circulation.
The risk of complications is clearly greater than with carotid angiography, and the examination can only be performed on young patients (ca 50 years or less).
Indications for aortic arch angiography
Subclavian steal syndrome, if endovascular treatment is considered (CTA or MRA are sufficient for diagnostics)
All the mentioned angiography examinations carry a risk of stroke of approximately 1%.
Echoencephalography
Primary investigation in infants with open fontanels
Detection of peri- and intraventricular haemorrhages in neonates and evaluation of the amount of CSF in cerebral ventricles in case of hydrocephalus suspicion
Assessment of the structures in the central parts of the brain
Radioisotope investigations
Radioisotope techniques (PET, SPET) have clinical significance as additional investigations supplementing structural imaging modalities in certain cases where differential diagnosis is problematic.