Neuropsychology in Presurgical Epilepsy Assessment

Neuropsychological assessment is a core part of modern epilepsy surgery evaluation. It measures functions such as memory, language, attention, executive ability, processing speed, mood and behaviour before treatment and helps estimate how surgery may affect them afterwards.

It is not an intelligence test

A presurgical neuropsychological evaluation is not simply a measure of IQ.

It builds a profile of strengths and weaknesses across multiple cognitive systems and relates that profile to the suspected seizure network.

Why epilepsy affects cognition

Cognition can be influenced by the underlying brain disorder, repeated seizures, interictal epileptiform activity, sleep disturbance, antiseizure medicines, mood, age at epilepsy onset and developmental history.

Establishing a baseline

Testing before surgery creates a documented cognitive baseline.

This allows meaningful comparison after surgery rather than relying only on impressions of whether memory, language or concentration “feels different”.

Memory

Memory assessment is particularly important before temporal lobe surgery.

Verbal and visual learning tests can provide information about temporal-lobe function, but simplistic rules such as “verbal equals left and visual equals right” are not reliable enough for individual surgical decisions.

Language

Naming, verbal fluency, comprehension, reading and other language skills are assessed when surgery may affect dominant-hemisphere networks.

Neuropsychology complements functional MRI, direct stimulation and—in selected cases—the Wada test.

Prediction of postoperative decline

One important principle is functional adequacy: when tissue targeted for surgery is still supporting strong memory or language function, removing it may carry greater risk of decline.

Conversely, severely dysfunctional tissue may have less useful function left to lose, although outcome prediction is never absolute.

Temporal lobe surgery

Left-sided temporal surgery can carry particular risk to verbal memory and naming, while right-sided surgery can affect other aspects of memory and visuospatial processing.

Individual organisation varies, especially after long-standing childhood epilepsy.

Lateralisation versus localisation

Neuropsychological patterns can contribute evidence about which hemisphere or network is dysfunctional, but they do not directly locate the seizure-onset zone.

They are one component of a multimodal hypothesis.

Mood and psychiatric assessment

Depression, anxiety, trauma, psychosis and adjustment difficulties can affect test performance and quality of life.

Identifying these issues before surgery also allows appropriate support and more realistic interpretation of cognitive results.

Performance validity

Clinicians assess whether results accurately reflect the person’s abilities. Fatigue, pain, sleep deprivation, medication effects, language barriers, low engagement or severe anxiety can influence performance.

This is not the same as assuming poor performance is deliberate.

Children

In children, assessment must consider ongoing brain development, school attainment and developmental trajectories.

The question is not only what function exists today but how epilepsy and surgery may affect future development.

Culture and language

Many neuropsychological tests were developed for specific languages and populations.

Using inappropriate norms can misclassify ability, so interpretation should consider language, education, cultural background and test validation.

After surgery

Repeat testing can identify cognitive change, recovery, compensation and areas needing rehabilitation.

It may also document improvements in attention, processing or quality of life when seizure burden falls.

Neuropsychology and seizure outcome

Neuropsychological data are not used primarily to predict seizure freedom. Their most established role is characterising cognitive networks and helping estimate functional risk.

The central point

Presurgical neuropsychology helps answer a different question from EEG or MRI: not only “where do seizures come from?” but “what important functions does this brain network currently support?”

Sources

Evidence checked: September 2026.