Focal cortical dysplasia is now one of the most important surgically treatable causes of drug-resistant focal epilepsy. Its modern history began with a small series of surgical specimens described in London in 1971.
The 1971 Maudsley series
David Taylor, Murray Falconer, Clive Bruton and J. A. N. Corsellis examined lobectomy specimens from ten people with severe focal epilepsy.
They described a localised cortical malformation containing large abnormal neurons and disorganised cortical architecture. The lesion was often difficult to recognise by eye or touch during surgery.
Why the finding was important
At the time, many people with severe focal epilepsy had no obvious tumour, scar or vascular lesion.
Taylor’s report showed that microscopic malformation of cortical development could itself be epileptogenic.
From ‘Taylor dysplasia’ to focal cortical dysplasia
The lesion became known as Taylor’s cortical dysplasia and later formed part of the broader concept of focal cortical dysplasia, or FCD.
Subsequent pathology showed that FCD is not one single entity. Different patterns of cortical organisation, dysmorphic neurons and balloon cells are associated with different pathological subtypes.
MRI changes detection
Early cases were discovered through pathology after surgery. Modern high-resolution epilepsy MRI can identify many FCDs before an operation, although subtle lesions can still be missed.
Features such as cortical thickening, blurring of the grey-white junction and the transmantle sign can support the diagnosis in some FCD subtypes.
Molecular biology changes the story again
Research has linked many FCD type II lesions to abnormal activation of the mTOR pathway, often through somatic mutations present only in a proportion of brain cells.
This connected FCD with a wider group of developmental ‘mTORopathies’ and strengthened the biological link with tuberous sclerosis.
Why MRI-negative FCD still matters
Some dysplasias remain invisible on standard MRI. Post-processing, PET, MEG, EEG source imaging, SEEG and repeat specialist review can help identify a suspected epileptogenic region.
Surgery can be highly effective when the epileptogenic dysplastic tissue can be localised and safely treated.
A discovery made possible by epilepsy surgery
The history of FCD shows how surgical treatment can generate scientific discovery. Without preserved surgical tissue and careful pathological correlation, this now-familiar epilepsy cause might have remained hidden for much longer.
Related reading
Sources and further reading
- Taylor et al. Focal dysplasia of the cerebral cortex in epilepsy, 1971
- Taylor’s focal cortical dysplasia revisited
Evidence checked: September 2026.