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Epilepsy (genetic generalised)
GGE is one of the most common forms of epilepsy, affecting people of all ages. It is considered a complex condition, meaning it is influenced by multiple genes and environmental factors, leading to a range of seizure types and severity.
Overview
Genetic generalised epilepsy (GGE) refers to a group of epilepsy syndromes where seizures begin in and rapidly involve both hemispheres of the brain. These seizures are often referred to as generalised seizures. GGE is distinguished from focal epilepsies, where seizures originate in a specific area of the brain [PMID:33671216]. It is one of the most common forms of epilepsy, affecting approximately 0.3-0.5% of the population.
While the term 'genetic' is included, GGE is typically considered a complex or polygenic condition. This means that multiple genes, rather than a single gene, contribute to an individual's susceptibility, often in combination with environmental factors. The specific genes involved can vary between individuals, contributing to the diverse clinical presentations observed in GGE.
Symptoms & clinical features
The main symptom of all epilepsies is recurrent, unprovoked seizures. In GGE, the seizures are generalised, meaning they affect both sides of the brain. Common types of generalised seizures seen in GGE include absence seizures, myoclonic seizures, and tonic-clonic seizures.
Absence seizures involve brief periods of staring or unresponsiveness, typically lasting a few seconds. Myoclonic seizures are characterised by sudden, brief, jerky movements, often affecting the arms or shoulders. Tonic-clonic seizures, also known as grand mal seizures, involve a loss of consciousness, stiffening of the body (tonic phase), and rhythmic jerking movements (clonic phase). The specific seizure types and their frequency can vary significantly among individuals with GGE [PMID:33671216].
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Affected organs
Genetic generalised epilepsy primarily affects the brain, which is the organ responsible for controlling all bodily functions, thoughts, and emotions. The electrical activity within brain cells is disrupted during a seizure, leading to the observed symptoms. While other organs are not directly affected by GGE, the consequences of seizures, such as injuries from falls, can indirectly impact other parts of the body.
Risks & severity
The severity of GGE can vary widely, from individuals who experience infrequent and well-controlled seizures to those with more frequent or difficult-to-treat seizures. Seizure onset typically occurs in childhood or adolescence, but can occasionally begin in adulthood. The lifetime risk of developing GGE is influenced by genetic predisposition, with close relatives of affected individuals having an increased, though still low, risk compared to the general population [PMID:33671216].
While many individuals with GGE achieve good seizure control with medication, some may experience ongoing seizures or associated cognitive or behavioural challenges. Research suggests that a significant number of people with GGE can eventually achieve long-term seizure freedom, particularly with appropriate management.
Genetic causes
Genetic generalised epilepsy is considered a complex genetic disorder, meaning its development is influenced by variations in multiple genes working together, rather than a single gene [PMID:22081554]. Genes associated with GGE often play roles in brain function, particularly in neuronal excitability and communication. For example, variations in genes that encode ion channels, which are proteins that control the flow of electrical signals in the brain, are often implicated.
Specific genes that have been associated with an increased risk of GGE include CACNA1H, GABRA1, and SCN1A. CACNA1H and SCN1A encode subunits of voltage-gated ion channels, which are crucial for generating and transmitting electrical impulses in nerve cells. GABRA1 encodes a subunit of the GABA-A receptor, which plays a key role in dampening neuronal activity. Pathogenic changes in these genes can alter the balance of excitatory and inhibitory signals in the brain, leading to increased susceptibility to seizures.
Inheritance pattern
Genetic generalised epilepsy typically follows a polygenic, or complex, inheritance pattern. This means that genetic susceptibility to GGE is influenced by multiple genes working together, often in combination with certain environmental factors, rather than being caused by a single gene mutation. The inheritance is not straightforward like in single-gene disorders, and not everyone with a predisposing genetic background will develop GGE.
While there may be a family history of seizures or epilepsy, the risk to individual family members can be difficult to predict. The likelihood of a relative developing GGE is generally low but is higher than in the general population. Genetic counselling can provide more personalised information regarding familial risks based on a specific family history.
Diagnosis & testing
Diagnosing genetic generalised epilepsy involves a comprehensive clinical assessment by a neurologist, including a detailed history of seizure types and patterns. An electroencephalogram (EEG) is a key diagnostic tool, as it can help identify the characteristic generalised spike-and-wave patterns associated with GGE. Brain imaging, such as an MRI, is often performed to rule out other causes of seizures.
Genetic testing for GGE is increasingly available, particularly through the NHS Genomic Medicine Service (GMS) pathways. Referral for genomic testing, typically under R-codes like R208 (for suspected genetic epilepsy), is usually made by a neurologist or clinical geneticist. This testing can help identify specific genetic factors contributing to the condition, although a genetic cause is not always found due to the complex nature of GGE. A genetic counsellor can explain the implications of genetic test results.
Management & lifestyle
The management of genetic generalised epilepsy primarily focuses on controlling seizures and improving quality of life. This is typically achieved through antiepileptic medications (AEMs), which help to stabilise brain activity and reduce seizure frequency. The choice of AEM depends on the specific seizure types experienced and individual patient factors. Regular follow-up with a neurologist is essential to monitor seizure control, adjust medication as needed, and manage any side effects.
Lifestyle considerations, such as ensuring adequate sleep, avoiding seizure triggers (like flashing lights or alcohol for some individuals), and stress management, may also form part of a comprehensive management plan. In cases where AEMs are not fully effective, other treatment options, such as dietary therapies (e.g., ketogenic diet) may be considered by specialists. All care is managed within established NHS pathways.
UK care pathway
In the UK, individuals suspected of having epilepsy, including genetic generalised epilepsy, are typically referred to a neurologist. Diagnosis and ongoing management take place within the NHS, following established clinical guidelines. If a genetic cause is suspected, particularly in complex or early-onset cases, referral to a clinical genetics service or for NHS Genomic Medicine Service (GMS) testing (e.g., under R-code R208 for genetic epilepsies) may be offered. Genetic counsellors play an important role in explaining genetic test results and familial implications.
Frequently asked questions
What is the difference between generalised and focal epilepsy?
In generalised epilepsy, seizures begin on both sides of the brain at the same time. In focal epilepsy, seizures start in a specific area of one side of the brain. The symptoms and treatment approaches can differ between these types.
Can genetic generalised epilepsy be cured?
Currently, there is no cure for genetic generalised epilepsy, but for many individuals, seizures can be effectively controlled with medication. Some people may even achieve long-term seizure freedom, making it seem like the condition is in remission.
If I have GGE, will my children also have it?
GGE typically has a complex inheritance pattern, meaning multiple genetic factors contribute to the risk. While there may be an increased risk for your children compared to the general population, it is generally low. Genetic counselling can provide a more personalised risk assessment based on your specific family history.
Does genetic testing always find a cause for GGE?
No, genetic testing for GGE does not always identify a specific genetic cause. Because GGE is often polygenic, involving many genes and potentially environmental factors, current testing methods may not detect all contributing genetic variations. However, as genetic research advances, more genetic factors are being discovered.
What should I do if I think I've had a seizure?
If you think you have experienced a seizure, you should contact your GP as soon as possible. They can refer you to a neurologist for a proper assessment and diagnosis. It's helpful to provide as much detail as possible about what happened during the suspected event.