Lesionectomy is epilepsy surgery in which a visible structural abnormality believed to be responsible for seizures is removed. The operation may be relatively small compared with larger lobar resections, but its success depends on whether the lesion truly represents the epileptogenic zone and whether it can be removed completely and safely.
What kinds of lesions are treated?
Lesionectomy may be considered for focal cortical dysplasia, dysembryoplastic neuroepithelial tumours (DNETs), gangliogliomas, cavernomas and other well-defined structural causes of focal epilepsy.
Seeing a lesion is not enough
A structural abnormality on MRI must fit the seizure semiology, EEG and other localisation data.
Some lesions are incidental and unrelated to the seizures, while epileptogenic tissue can extend beyond the visible border of a lesion.
Focal cortical dysplasia
For localised focal cortical dysplasia, complete removal of the abnormal cortex is one of the strongest predictors of seizure freedom.
A 2024 study of MRI- and FDG-PET-guided lesionectomy for localised type II focal cortical dysplasia reported favourable seizure outcomes when the lesion was completely removed.
Low-grade epilepsy-associated tumours
DNETs and gangliogliomas are often associated with long-standing focal seizures. Surgery may remove the tumour itself and, where necessary, surrounding epileptogenic cortex.
Early surgery can sometimes reduce the duration of uncontrolled epilepsy before wider networks become established.
Cavernomas
Cerebral cavernous malformations can cause focal epilepsy through irritation of surrounding tissue, including blood-breakdown products such as haemosiderin.
Depending on location and electroclinical findings, surgery may include the lesion and selected surrounding abnormal tissue.
Lesionectomy versus larger resection
The smallest operation is not automatically the best operation.
If evidence shows that the epileptogenic zone extends beyond the lesion, a larger tailored resection may be needed. Conversely, removing normal functional tissue unnecessarily can increase neurological risk.
Eloquent cortex
Lesions near language, motor, sensory or visual cortex require particularly careful planning.
Functional MRI, neuropsychology, direct stimulation, tractography or invasive EEG may be used to define safe boundaries.
When intracranial EEG is needed
A clearly visible lesion with strongly concordant non-invasive data may sometimes be removed without invasive monitoring.
SEEG is more likely when the lesion is subtle, multiple abnormalities exist, MRI and EEG disagree, or the lesion lies within a wider suspected network.
Complete resection
Across many lesional epilepsies, incomplete removal of the epileptogenic abnormality is associated with poorer seizure outcome.
This is why postoperative MRI and pathological confirmation can be important.
Histopathology
Surgical tissue can establish the final diagnosis, such as focal cortical dysplasia, tumour, gliosis or vascular pathology.
Histopathology may also clarify why MRI appearance and seizure behaviour differed.
Risks
Risks depend mainly on lesion location and surgical extent and include bleeding, infection, stroke, weakness, sensory loss, language difficulty, visual-field deficits and cognitive change.
The central point
Lesionectomy works best when the visible lesion, seizure network and surgical target genuinely match. Complete removal of the relevant epileptogenic tissue is more important than simply removing whatever looks abnormal on MRI.
Related reading
Focal Cortical Dysplasia →
DNET and Epilepsy →
Cavernomas and Epilepsy →
Epilepsy Surgery and Presurgical Assessment →
Sources
Evidence checked: September 2026.