Epilepsy MRI Protocol
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Direct answer
An epilepsy protocol MRI is a targeted hunt for a structural cause of drug-resistant seizures, built around the hippocampus: thin-slice (2-3 mm) oblique coronal T2 and FLAIR sequences perpendicular to the temporal lobe, a high-resolution 3D T1 volumetric acquisition, susceptibility-weighted or T2* imaging for calcification and microhaemorrhage, diffusion imaging, and contrast when a tumour or inflammation is plausible. Mesial temporal sclerosis — the commonest finding in adult surgical series — is diagnosed by a small hippocampus, increased T2 signal, loss of internal architecture, fornix and mammillary body atrophy, and enlargement of the temporal horn. In Indian practice the same protocol must catch neurocysticercosis, calcified granulomas and tuberculoma, which dominate the structural epilepsy lists alongside cortical dysplasias, cavernomas and low-grade tumours such as dysembryoplastic neuroepithelial tumours.
What you must remember
- Sequence set: 3D T1 (MPRAGE) for cortical thickness and volume, oblique coronal T2 and FLAIR at 2-3 mm perpendicular to the hippocampus, T2*/SWI for calcification and haemorrhage, DWI, and contrast if a mass or inflammation is suspected — 3 Tesla where available.
- Mesial temporal sclerosis signs: small hippocampus, hyperintense T2/FLAIR, lost internal digitations, dilated temporal horn, ipsilateral fornix and mammillary body atrophy, and loss of grey-white demarcation in the anterior temporal lobe.
- Why it matters: anterior temporal lobectomy with amygdalohippocampectomy for drug-resistant mesial temporal sclerosis is among the most successful epilepsy surgeries, and MRI laterality is the single strongest predictor of outcome.
- Focal cortical dysplasia: cortical thickening with blurred grey-white junction and the transmantle sign, a tapering abnormality from ventricle to cortex — type II dysplasia, the commonest cause in children.
- Tumour-ish causes: DNET — cortical, bubbly, T2-bright, slow-growing, presents with seizures in the young; ganglioglioma and low-grade astrocytoma complete the list; cavernoma gives a popcorn lesion with a complete haemosiderin ring blooming on T2*.
- Indian structural causes: neurocysticercosis — ring or vesicular lesions with an eccentric scolex, later calcified granulomas that are the commonest imaging finding in adult Indian epilepsy — plus tuberculoma and post-meningitic scarring.
- Complementary functional tests: ictal SPECT shows hyperperfusion, interictal PET hypometabolism, and EEG-video telemetry ties the structural lesion to the seizure onset zone.
Reading one epilepsy study
A 26-year-old has complex partial seizures since adolescence, refractory to two drugs. Coronal FLAIR through the temporal lobes shows a small, bright left hippocampus with loss of its internal grey-white stripes, an enlarged left temporal horn, and a thin left fornix on 3D T1. The rest of the brain, including the periventricular white matter and cortex, is normal. The report reads: left mesial temporal sclerosis, MRI-positive temporal lobe epilepsy. Phase-two evaluation follows — video-EEG confirming left temporal onset, neuropsychology, sometimes functional MRI for language lateralisation — before anterior temporal lobectomy, which offers a substantial seizure-free rate in this phenotype.
The contrast case is a 19-year-old with morning seizures and a lesion in the right temporal cortex: a well-defined, multicystic, T2-hyperintense cortical lesion with a faint nodular area and no surrounding oedema or mass effect — DNET, requiring surgical removal for seizure control rather than oncological resection. A third, a 30-year-old from an endemic belt, has a small calcified granuloma on SWI at the seizure focus — a calcified neurocysticercal granuloma, managed medically first, with surgery reserved for refractory cases; this is the commonest structural finding in Indian epilepsy clinics and the one international exams under-weight.
Where students slip
First, calling every bright hippocampus sclerosis: artefacts and partial volume make asymmetrical hippocampi tricky, and the diagnosis needs at least two of the four signs — atrophy, T2 hyperintensity, architecture loss and fornix atrophy — not signal alone. Second, sequence logic: the coronal plane perpendicular to the hippocampus exists because axial slices cannot show internal architecture; a viva favourite asks why the protocol is "oblique coronal". Third, forgetting that a normal epilepsy MRI does not end the workup — it upgrades the patient to 3 Tesla review, post-processing morphometry, or semiology-led re-evaluation. Indian exam framing: when the vignette mentions pork exposure, epilepsy in a young adult with a ring lesion containing a dot, answer scolex and neurocysticercosis before lymphoma or tuberculoma.
Frequently asked questions
Which MRI features diagnose mesial temporal sclerosis?
A small hippocampus with increased T2 or FLAIR signal, loss of internal architecture, temporal horn dilatation and ipsilateral fornix or mammillary body atrophy.
Why are oblique coronal sequences used in epilepsy MRI?
Thin oblique coronal T2 and FLAIR images perpendicular to the hippocampal long axis display its internal structure and size comparison, which axial sections cannot resolve.
What is the transmantle sign?
A tapering band of abnormal signal extending from the ventricular surface to the cortex, indicating type II focal cortical dysplasia, a leading cause of surgically remediable paediatric epilepsy.
Which imaging features characterise a DNET?
A cortical, multinodular or bubbly T2-hyperintense lesion in a young patient with seizures, with minimal mass effect and no oedema, often remodelling the overlying skull.
What is the role of the scolex sign in Indian epilepsy imaging?
A low-intensity nodule inside a cystic ring lesion represents the neurocysticercus scolex, diagnosing neurocysticercosis, the commonest cause of adult-onset structural epilepsy in India.