Surgery is a well-established approach to treating epilepsy; nevertheless, it remains an underutilized treatment in this country. Of the 2.5 million patients in the United States with epilepsy, 250,000 are potential candidates for surgery, and each year there are 5,000 new potential surgical candidates. Despite the potential benefits of surgery, many candidates who could benefit from surgery are not referred because patients and doctors are unaware of the option for those whose seizures are not controlled by medications. The success rate for temporal lobe epilepsy surgery is nearly 80 percent.
What is a Seizure?
A seizure is defined as a sudden, electrical discharge in the brain causing alterations in behavior, sensation, or consciousness. The brain is comprised of thousands of neurons – cells that process and transmit information by interacting with each other. Under normal circumstances, neurons communicate in a chaotic but balanced, orderly fashion with few disruptions. Occasionally, small disruptions (neuron misfires) may occur with little consequence. When multiple cells misfire at the same time – depending on the severity and location in the brain – it may cause muscle twitches and spasms. This is a seizure.
The Difference Between "Seizure and Epilepsy"
The two terms are not synonymous, although often mistakenly used together. A seizure is a single occurrence and is different than epilepsy which is defined as two or more unprovoked seizures. Seizures that appear to begin everywhere in the brain at once are classified as generalized seizures, while those beginning in one
location of the brain are classified as partial seizures.
Three Stages of a Seizure
What is Epilepsy?
- Aura- The start of a partial seizure. If the aura is the only part an individual experiences, they've had a simple partial seizure. If the seizure spreads and affects consciousness, it is known as complex partial seizure. If the seizure spreads to the rest of the brain, it is classified as a generalized seizure.
- Ictus- This is simply another word for physical seizure.
- Postictal- Meaning after the attack, it refers to the period following a seizure, e.g., arm numbness, loss of consciousness, partial paralysis, etc.
Epilepsy is defined as two or more unprovoked seizures due to a variety of conditions.
he evaluation of the patient with epilepsy for possible surgical intervention is a multi-disciplinary and multi-step process:
This step is performed by a neurologist who performs the initial assessment in the clinic. The neurologist may decide to change the medication regimen. Imaging studies and other diagnostic tests may be ordered to determine the patient's candidacy for surgery.
If the initial evaluation deems the patient a potential candidate for surgery, the patient is subsequently admitted to a special neurosurgery monitoring unit, where the medical team monitors seizure activity 24 hours a day with video recording and non-invasive scalp electroencephalograph (EEG) electrodes until enough seizures are documented to characterize them fully.
EEG - Electroencephalogram of a patient with intractable epilepsy demonstrating abnormal ictal spikes arising from the temporal and frontal areas.
Additional testing such as positron emission tomography (PET) brain imaging tests, magnetoencephalogram (MEG), as well as tests of memory, perception and other cognitive functions may be performed. These tests help pinpoint the seizure focus by providing additional information about any brain abnormalities.
If the data obtained during the phase I evaluation is unable to accurately localize the exact location of the seizure focus, the epilepsy team will need additional information. During phase II, the patient undergoes an operation where electrodes are placed directly on the surface of the brain or within the substance of the brain (depth electrodes). The patient is subsequently monitored in the neurosurgery monitoring unit for seizure activity.
If the exact location of the seizure focus is identified by the above mention steps, the patient is taken to the operating room during phase III for definitive respective surgery of the seizure focus. Additional tests may be performed in the operating room, including functional brain mapping of language or motor function, electrocorticography (ECoG) and intra-operative image guidance.
The location and type of damage or abnormality determines the type of epilepsy surgery and plays a critical role in treatment outcomes. The Rush-Copley epilepsy surgery program, in affiliation with Rush University offers surgical options for treating the following types of epilepsy:
- Mesial temporal lope epilepsy
- Epilepsy caused by tumors or abnormalities of blood vessels.
- Frontal lobe epilepsy.
- Other extra-temporal lobe epilepsies. - Seizures arising outside the temporal lobe are often generalized, meaning they spread throughout the brain and cause convulsions. They are also difficult to localize and at times are located in functionally eloquent areas of the brain making them less amenable to respective surgery. The success of surgical treatment for epilepsies outside the temporal lobe is approximately 45 percent.
- Epilepsies where the seizure focus is in an area for function - In some cases where the seizure focus is in an area essential for communication, movement or other necessary functions, resection is not recommended. In these cases, a palliative operation called Multiple Subpial Transection (MST) can be performed. While it is not a respective operation, MST can decrease the number of seizures and help improve the quality of the patient’s life.
- Epilespy where resection is not an option - If the patient is not a surgical candidate or the patient is unable to have a resection surgery performed, other procedures may be of benefit in controlling epilepsy such as Surgical placement of a vagal nerve stimulator.
Temporal Lobectomy/Hippocampus Resection
Anterior temporal lobe approach to resection of the amygdala and hippocampus (amygdalohippocampectomy).
Illustration of the surgical approach to the hippocampus
Intraoperative view of the anatomy under microscopic magnificationp
Post operative MRI showing a right sided selective amygdalohippocampectomy
Some causes of epilepsy include head trauma, tumors, abnormal development of the brain in early childhood, and a family history of epilepsy. For the majority of patients, epilepsy can be fully controlled by daily medications. Antiepileptic drugs act on brain cells to make them less likely to fire. In patients who have seizures that are not well controlled even after trying a number of drugs, or whose medications may have side effects that are not well tolerated, surgery should be considered.
The success of epilepsy surgery depends on a number of factors including the type of surgery and location of the seizure focus among other factors. On average approximately 80 percent of patients with temporal lobe epilepsy become seizure free or nearly seizure free after surgery.