Tuberous Sclerosis Complex and Epilepsy

How a genetic mTOR-pathway disorder can produce cortical tubers, early-life seizures and drug-resistant epilepsy

Tuberous sclerosis complex (TSC) is a genetic condition that can affect the brain, skin, kidneys, heart, lungs and eyes. Neurologically, epilepsy is one of its most important complications. Seizures often begin in infancy or early childhood, can be difficult to control, and may interact with development, behaviour and learning.

TSC-associated epilepsy is not caused by one single lesion or one single seizure type. It reflects the interaction between altered cell-growth signalling, abnormal cortical development, multiple structural brain lesions and evolving epileptic networks.

What causes tuberous sclerosis complex?

TSC is caused by pathogenic variants in TSC1 or TSC2. These genes encode hamartin and tuberin, proteins that normally restrain activity in the mTOR signalling pathway.

When this regulatory system is disrupted, mTOR activity becomes abnormally increased. The result is altered cell growth, proliferation and differentiation across multiple organs.

This molecular mechanism matters in epilepsy because abnormal mTOR signalling contributes to the formation and behaviour of cortical tubers and other brain lesions, and it also provides a treatment target in some people with drug-resistant TSC-associated seizures.

Cortical tubers and epilepsy

Many people with TSC have cortical tubers, areas of abnormal cortical development visible on MRI. They are strongly associated with epilepsy, but the relationship is not as simple as “one tuber equals one seizure focus”.

A person may have many tubers but only one or a small number may be strongly epileptogenic. In other people, the seizure network can involve cortex around a tuber or span more than one region.

This is why the largest or most visually obvious tuber on MRI is not automatically the one causing the seizures.

Clinical seizure semiology, scalp EEG, prolonged video-EEG, high-quality MRI and, in selected cases, PET, MEG or invasive recordings may all be needed to understand the epileptic network.

Other brain findings in TSC

TSC can also produce:

subependymal nodules along the walls of the lateral ventricles;
subependymal giant cell astrocytomas (SEGAs);
radial migration lines or other white-matter abnormalities;
more widespread network changes that may not correspond neatly to a single visible tuber.

These findings do not all carry the same seizure significance. A SEGA, for example, is clinically important because of its potential to grow and obstruct cerebrospinal fluid pathways, but it is not automatically the source of a person’s epilepsy.

Epilepsy often begins early

Epilepsy is very common in TSC, and seizure onset frequently occurs in the first year of life.

Early-onset epilepsy matters because uncontrolled seizures during infancy occur at the same time that the brain is rapidly developing. In TSC, earlier seizure onset and poor seizure control have been associated with greater risk of developmental and neuropsychiatric difficulties at a population level.

This does not mean that seizures alone determine development. TSC itself affects brain development, and outcomes vary widely between individuals.

Why EEG monitoring can start before the first clinical seizure

TSC is unusual because epilepsy risk can sometimes be recognised before obvious seizures begin.

The 2021 International TSC Consensus recommendations increased the emphasis on early EEG surveillance in infants with known or suspected TSC. Epileptiform abnormalities can sometimes appear on EEG before parents or clinicians have seen a clear clinical seizure.

This has led to research on presymptomatic or preventive treatment, particularly with vigabatrin, in infants who develop epileptiform EEG activity before obvious seizures.

Trials including EPISTOP showed that presymptomatic treatment can delay seizure onset and reduce some measures of epilepsy severity, although questions remain about which infants benefit most and how preventive treatment should be implemented across different healthcare systems.

Infantile spasms

Infantile spasms are a particularly important seizure type in TSC.

They may appear as brief flexion, extension or mixed movements, often occurring in clusters. Because the movements can be subtle, they are sometimes mistaken for colic, reflux, startle or normal infant behaviour.

EEG may show hypsarrhythmia, but not every child with TSC-associated spasms has a textbook pattern at every stage.

International TSC guidance recommends vigabatrin as first-line treatment for infantile spasms associated with TSC, unless there is a specific reason it cannot be used.

Why vigabatrin is important in TSC

Vigabatrin increases inhibitory GABA signalling by irreversibly inhibiting GABA transaminase. It has a particularly established role in TSC-associated infantile spasms and is also used for some focal seizures in TSC.

Its use requires specialist oversight because it can cause adverse effects, most notably retinal toxicity and irreversible visual-field loss in some people. Monitoring practice varies with age, clinical circumstances and local guidance.

The fact that vigabatrin is particularly effective for TSC-associated infantile spasms is one reason rapid recognition of spasms matters.

Focal seizures

Focal seizures are also common in TSC and can begin before, after or alongside infantile spasms.

The clinical appearance depends on the network involved. Episodes may include behavioural arrest, altered awareness, focal motor activity, eye or head deviation, asymmetric tonic posturing, sensory symptoms or autonomic changes.

As epilepsy evolves, some people develop multiple seizure types and more widespread EEG abnormalities.

Epileptic encephalopathy and developmental epileptic encephalopathy

In severe early-onset TSC epilepsy, frequent seizures and epileptiform activity may contribute to worsening developmental function. Modern terminology increasingly distinguishes the developmental effects of the underlying genetic brain disorder from the additional impact of uncontrolled epilepsy.

In practice, both may matter.

Early diagnosis and seizure control are therefore important not only for reducing seizure frequency but also because they may improve the developmental trajectory for some children.

TAND: the neuropsychiatric side of TSC

TSC can be associated with a wide spectrum of neuropsychiatric features collectively called TSC-associated neuropsychiatric disorders, or TAND.

These can include intellectual disability, autism spectrum disorder, attention difficulties, anxiety, mood problems, sleep disturbance, behavioural dysregulation and specific learning difficulties.

TAND is not simply a side effect of epilepsy medication, and not every neuropsychiatric difficulty disappears when seizures improve. However, severe uncontrolled epilepsy can add to cognitive and behavioural burden.

International consensus guidance recommends regular screening for TAND across the lifespan rather than waiting until difficulties become severe.

Why drug resistance is common

Many people with TSC achieve useful seizure control with medication, but drug resistance is common and can develop early.

This is biologically understandable. The brain may contain multiple abnormal cortical regions, and seizure networks can become distributed rather than being driven by a single easily treated focus.

When two appropriate antiseizure medication schedules have failed to produce sustained seizure freedom, specialist assessment for drug-resistant epilepsy should not be delayed.

Antiseizure medication beyond vigabatrin

There is no single universal medication sequence for all TSC-associated epilepsy.

Treatment depends on seizure type, age, comorbidities, previous response, potential adverse effects, interactions and individual circumstances.

Other antiseizure medicines used in focal or mixed TSC-associated epilepsy can include drugs commonly used for focal seizures more generally. The exact regimen should be selected by the treating specialist rather than by the diagnosis of TSC alone.

Everolimus: treating the mTOR pathway

Everolimus is an mTOR inhibitor. Unlike conventional antiseizure medicines, it targets the dysregulated molecular pathway that is central to TSC biology.

Randomised controlled trial evidence has shown that adjunctive everolimus can reduce seizure frequency in some people with TSC-associated drug-resistant focal seizures.

Everolimus is not simply another routine antiseizure drug. It has important adverse-effect, infection, laboratory-monitoring and interaction considerations and is prescribed within specialist care.

Its role is particularly significant because it links molecular pathogenesis directly to epilepsy treatment.

Cannabidiol

Highly purified pharmaceutical cannabidiol is another evidence-based option for some people with TSC-associated seizures.

Randomised controlled trial evidence has shown a reduction in seizure frequency compared with placebo in TSC. Treatment requires attention to liver-function monitoring and drug interactions, particularly with other antiseizure medicines.

This is different from over-the-counter CBD oils or unregulated cannabis products, which are not equivalent in dose, purity, formulation or evidence base.

The ketogenic diet

Ketogenic dietary therapies can be considered for some people with drug-resistant TSC-associated epilepsy.

These diets alter metabolism and can reduce seizures in some children and adults with difficult-to-treat epilepsy. They require specialist dietetic and medical supervision because nutritional, gastrointestinal, metabolic and medication-related issues need monitoring.

Epilepsy surgery

Epilepsy surgery can be highly effective in carefully selected people with TSC, even when MRI shows multiple tubers.

The key question is whether a dominant epileptogenic region can be identified and treated safely.

Presurgical evaluation may combine seizure semiology, prolonged video-EEG, high-resolution MRI, PET, MEG, neuropsychology and, in selected cases, stereoelectroencephalography (SEEG).

The surgical target may be a tuber, cortex around a tuber, or a broader epileptogenic zone. Removing every visible tuber is neither necessary nor realistic.

Updated European recommendations emphasise that surgical evaluation should be considered early in people with TSC and drug-resistant epilepsy rather than left until all other options are exhausted.

Why multiple tubers do not automatically rule out surgery

A common misconception is that surgery is impossible because TSC can produce many brain lesions.

In reality, some people with multiple tubers still have seizures consistently arising from one dominant region.

If the clinical events, EEG, imaging and other investigations converge on that region, resection or ablation may provide substantial seizure improvement or seizure freedom.

The challenge is localisation, not simply lesion count.

SEGA and epilepsy are different questions

Subependymal giant cell astrocytomas are TSC-associated brain tumours that usually arise near the ventricles.

They matter because they can grow and cause hydrocephalus or other neurological problems. Everolimus can also be used in selected people with growing SEGAs.

But the presence of a SEGA does not automatically mean it is causing a person’s seizures. Epilepsy in TSC is more commonly related to cortical epileptogenic networks.

MRI surveillance

Brain MRI is important not only for epilepsy but also for monitoring TSC-related structural abnormalities, especially SEGAs.

International consensus recommendations include periodic brain MRI in younger people with TSC to monitor for SEGA development and growth, with the schedule adjusted according to age, findings and clinical circumstances.

For epilepsy, MRI also helps characterise tuber burden and other cortical abnormalities, but imaging cannot independently identify the seizure-onset zone.

EEG can change over time

EEG in TSC may evolve from focal epileptiform discharges to multifocal or more widespread abnormalities, particularly in severe early-onset epilepsy.

This evolution can reflect maturation, new seizure types and network recruitment.

A single EEG therefore represents one time point rather than a permanent map of the epilepsy.

Similarly, a normal EEG does not exclude epilepsy if the clinical history strongly suggests seizures.

Genotype does not determine one fixed outcome

TSC2 pathogenic variants are, on average, associated with a more severe phenotype than TSC1 variants in many cohort studies, including greater neurological burden. But genotype does not precisely predict an individual’s epilepsy course.

Mosaicism, variant type, brain lesion distribution and many other biological factors contribute to variability.

Two people with TSC can therefore have very different seizure histories even within the same family.

TSC is a whole-body condition

Epilepsy care cannot be separated completely from the rest of TSC.

Kidney angiomyolipomas, renal cysts, cardiac rhabdomyomas, pulmonary lymphangioleiomyomatosis, skin findings, retinal lesions and neuropsychiatric difficulties may all require surveillance or treatment.

Medication choices may therefore need to account for kidney function, other TSC treatments, drug interactions and future procedures.

Adults with TSC and epilepsy

TSC is lifelong. Epilepsy that begins in infancy may continue into adulthood, but some people are first diagnosed later because subtle skin, renal or neurological features were previously missed.

Adult care needs to include transition from paediatric services, continued seizure review, TAND screening, renal and pulmonary surveillance where appropriate, medication review, reproductive counselling and assessment of independence and support needs.

Pregnancy and reproductive counselling

TSC is usually inherited in an autosomal dominant pattern, although many affected individuals have a new pathogenic variant rather than an affected parent.

A person with a pathogenic TSC1 or TSC2 variant may have a 50% chance of passing that variant to each child, although genetic counselling is needed because mosaicism and individual circumstances can complicate risk interpretation.

For people with epilepsy, pregnancy planning also needs to consider antiseizure medication safety, folic acid, seizure control and specialist obstetric care.

The key distinction

Tuberous sclerosis complex is a genetic multisystem disorder. TSC-associated epilepsy is one of its neurological manifestations, but it is not explained by a single tuber, a single EEG abnormality or a single molecular pathway alone.

Cortical tubers can generate seizures, but not every tuber is epileptogenic. Multiple lesions do not automatically exclude surgery. Early EEG abnormalities can precede clinical seizures. Vigabatrin has a special role in TSC-associated infantile spasms. Everolimus targets the mTOR pathway itself. And seizure control has to be considered alongside development, behaviour and the wider medical burden of TSC.

The most useful model is therefore not “many lesions causing many seizures”, but a genetically driven disorder in which molecular signalling, cortical development and epileptic networks interact across the lifespan.

Sources and further reading

Evidence checked: September 2026.

This page is for general education and does not replace individual advice from a TSC specialist, neurologist, epilepsy specialist, geneticist or other member of the multidisciplinary team.