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increase the conspicuity of lesions, but does not improve the identification of
heterotopias4,5,6,7. In the first two years of life, incomplete myelination results in poor grey-
white matter contrast, making identification of cortical abnormalities difficult, and in these
cases MRI may need to be repeated after 12 years.

In an acute situation when seizures occur in the context of a neurological insult, X-ray CT is
an appropriate initial investigation if MRI is not readily available or not possible for technical
reasons, for instance if the patient has a cardiac pacemaker or requires attention during the
scan. Recent improvements in the design and manufacture of pacemakers and vagal nerve
stimulators have improved MRI compatibility although safety issues at higher field strength
remain an issue.

The best practice is to obtain MRI in all patients with epilepsy, with the exception of those
with a definite diagnosis of idiopathic generalised epilepsy or benign rolandic epilepsy of
childhood with centrotemporal spikes, who go into early remission. MRI is particularly
indicated in patients with one or more of the following:

 Onset of partial seizures, at any age
 Onset of generalised or unclassified seizures in the first year of life, or in adulthood
 Evidence of a fixed deficit on neurological or neuropsychological examination
 Difficulty obtaining seizure control with first-line antiepileptic drugs (AEDs)
 Loss of seizure control, or a change in the pattern of seizures.

In situations in which access to MRI is limited, essential indications for MRI are:

 Patients with partial or secondarily generalised seizures, and apparently generalised

seizures, that are not controlled with AEDs

 Patients who develop progressive neurological or neuropsychological deficits.

A recent survey in the UK shows that optimal practice is not applied universally6, and in a
study in Germany, the quality of MRI scans obtained in community hospitals was
significantly less than those obtained at an epilepsy centre8.

Presurgical candidates
Patients who are being considered for surgical treatment merit the most sophisticated MR
imaging that is available and may also benefit from functional imaging with positron emission
tomography (PET) and single photon emission computed tomography (SPECT).
Identification of a structural lesion, however, does not always indicate the site of seizure
origin. Clinical, EEG and other data all need to be considered.

A typical presurgical MRI protocol would be:

 Volume acquisition T1-weighted data set that is acquired in an oblique coronal

orientation, orthogonal to the long axis of the hippocampi, and covers the whole brain in
0.9 mm partitions. This sequence produces approximately cubic voxels, allowing for
reformatting in any orientation, subsequent measurement of hippocampal morphology
and volumes, and for three-dimensional reconstruction and surface rendering of the brain;

 Oblique coronal spin-echo sequence, with proton density (TE = 30), heavily T2-weighted

(TE = 90 or 120) and FLAIR acquisitions that are orientated perpendicular to the long
axis of the hippocampus, to demonstrate any increase in T2-weighted signal intensity.