Indications in MRI Scanning

MRI scanning in emergency medicine is becoming increasingly common. Machines are becoming more widespread, but the skills to provide radiographic support on a 24/7 basis remain limited. Clinicians are more likely to have access to facilities in larger institutions operating at the tertiary level.

Stroke management

An important indication for seeking an MRI of the brain is to support the management of stroke and distinguish haemorrhage from ischaemia.

The Royal College of Radiologists recommends using a diffusion-weighted protocol for its greater sensitivity in detecting ischaemia [4].

However, the need to access imaging within 3 hours of symptom onset makes MRI a difficult option, even with its accuracy. MRI scanning requires a stable patient with all steps already taken to ensure safety during the scanning process.

The American Heart Association/American Stroke Association Stroke Council regards CT and MRI as being equal first-line interventions in stroke, with CT preferred when MRI is contraindicated [5].

The above view conflicts with that of Chalela et al, who found that MRI was superior in sensitivity for all forms of stroke and, in particular, was more effective in detecting ischaemic stroke within 3 hours of onset [6]. This would have implications for teams planning a stroke thrombolysis service.

Learning bite

MRI is superior to CT in the diagnosis of stroke.

Alternative techniques for stroke management

Some centres have chosen CT perfusion scanning as an equally effective yet quicker method, but this is largely confined to tertiary centres. Other centres use enhanced techniques such as MR angiography to assess obstruction in major vessels within or without the cranial cavity.

The image displays a normal MR angiogram of the head and neck with gadolinium in coronal plane.

Other indications for MRI of the brain

Other indications for MRI scanning include detecting cerebral abscess or meningitis in the immunocompromised [7-8].

Paediatric neurologists may use MRI to differentiate encephalomyelitis from encephalitis.

Most brain imaging uses the T1 weighted protocol, allowing enhanced display of any lesion disrupting the blood-brain barrier (e.g. tumour, haemorrhage, infection).

Emergency spinal MRI

MRI has an increasing role in the diagnosis of spinal disorders in the ED, where a rapid diagnosis is required to support definitive care

The indications for emergency spinal MRI include [4]:

• Symptoms of spinal cord compression and cauda equina syndrome
• Spinal infection (abscess, meningitis)
• Demyelination
• Transverse myelitis
• Spinal trauma (contusion, epidural haemorrhage, ligamentous injury, etc)