Structural and acquired epilepsies arise when a detectable abnormality, injury or disease affecting the brain contributes to an enduring tendency to have seizures. The structural change may have been present from early development, may have resulted from stroke, trauma, infection or tumour, or may reflect a specific lesion that alters the way local and wider brain networks function.
This section brings together the major structural and acquired causes that can sit behind focal epilepsy and some forms of drug-resistant epilepsy. It is designed to complement — not duplicate — the broader Causes of Epilepsy, MRI and Neuroimaging in Epilepsy and Epilepsy Surgery and Presurgical Assessment pages.
What “structural” means in epilepsy
In modern epilepsy classification, a structural aetiology means that a structural brain abnormality is believed to increase the risk of seizures. The abnormality may be acquired, such as after stroke, trauma or infection, or it may arise from abnormal brain development.
Finding a structural lesion does not automatically prove that it is the source of every seizure. Clinicians compare MRI, seizure semiology, EEG findings, neuropsychology and other investigations to determine whether the lesion and the epilepsy are concordant.
Why this section matters
Structural epilepsies are clinically important because the underlying cause can affect prognosis, medicine choice, the likelihood of drug resistance and whether a person should be considered for epilepsy surgery or other advanced treatment.
Some lesions are highly epileptogenic, while others are discovered incidentally. Some remain stable for decades; others may progress. Some are best treated medically, while others may become surgical targets in carefully selected patients.
Anchor topics in this section
- Hippocampal Sclerosis
- Focal Cortical Dysplasia
- Post-Stroke Epilepsy
- Post-Traumatic Epilepsy
- Autoimmune Epilepsy
- Brain Tumour-Related Epilepsy
- Epilepsy After CNS Infection
- Cavernomas and Epilepsy
- Hypothalamic Hamartoma and Epilepsy
- Tuberous Sclerosis Complex and Epilepsy
Additional rarer structural causes are listed below.
Structural does not mean visible on every MRI
Some lesions are subtle. Focal cortical dysplasia, small cavernomas, mild hippocampal sclerosis and other abnormalities can be missed on routine imaging, particularly if the scan was not performed using an epilepsy protocol or reviewed by an experienced neuroradiologist.
A normal routine MRI therefore does not exclude a structural epilepsy.
Structural does not mean surgically curable
Even when a lesion is visible, surgery is not automatically appropriate. The epileptogenic network may extend beyond the lesion, the abnormality may involve eloquent cortex, or seizure onset may not clearly localise to the structural change.
Presurgical evaluation exists to answer those questions before treatment decisions are made.
More rare structural causes
Sturge–Weber Syndrome and Epilepsy →
Hemimegalencephaly and Epilepsy →
Polymicrogyria and Epilepsy →
Schizencephaly and Epilepsy →
Periventricular Nodular Heterotopia and Epilepsy →
Dysembryoplastic Neuroepithelial Tumour (DNET) and Epilepsy →
Structural does not mean static
A structural lesion may be congenital, acquired, progressive or biologically stable. Some lesions are visible at birth; others appear after stroke, trauma, infection, tumour or inflammation.
Imaging-negative does not exclude structural epilepsy
Small focal cortical dysplasias and subtle malformations can remain invisible on routine MRI. Dedicated epilepsy-protocol MRI, expert neuroradiology review and post-processing can reveal lesions that standard imaging misses.
Structure and network must both be considered
The visible lesion is not always identical to the full epileptogenic zone. Presurgical assessment integrates semiology, EEG, imaging, neuropsychology and sometimes PET, SPECT, MEG or SEEG.
Sources
World Health Organization — Epilepsy fact sheet
WHO/ILAE/IBE — Epilepsy: a public health imperative
Evidence checked: September 2026.