How to assess and treat intractable epilepsy
About 20% of patients with epilepsy continue to have seizures despite maximized medical therapy. These patients are said to have intractable epilepsy and may be excellent candidates for surgical procedures to help control their seizures. Intractable epilepsy is common in children and should be screened for in all pediatric patients with epilepsy.
Intractable epilepsy can be remarkably disabling and limiting, and surgery for the disorder is generally underperformed throughout the world. Many patients are maintained on multiple inefficacious medications—even as they continue to face seizure after seizure.
What to do when you suspect your patient has intractable epilepsy?
Obtain a history of seizure activity
When following a patient with epilepsy, take a good history of the nature of the seizures. This should include information about what exactly the seizure is like:
- Do the seizures involve shaking, or staring, automatisms?
- Are they tonic-clonic (e.g., grand mal)?
- How long do they last?
- What sets them off?
- Is there an aura associated with the seizure?
- How long is the patient affected afterward?
- Has there been any loss of continence or falls?
Also, ask the patient about seizure frequency, associated neurological symptoms, anticonvulsant medication history, and deleterious effects of the seizures or the medications.
Obtain a thorough medical history
Solicit any other pertinent medical information such as a history of drinking, drug use, or major medical comorbidities, all of which may contribute to poor seizure control. Seizures might be very controllable with anticonvulsants if such exacerbating factors can be controlled.
Focus on anticonvulsant regimens the patient has already tried. Make sure you ask about compliance—seizures can't be considered intractable if the patient isn't taking their medications.
In general, a patient won’t be considered for surgery unless they have gone through several trials of anticonvulsants, taken alone and in combination. Ideally, an epilepsy specialist should help guide anti-seizure medication trials.
Ask the patient to keep a seizure diary
Have the patient keep a seizure diary describing the nature and timing of seizures. The more frequent and debilitating the seizures, the better the risk-benefit ratio of surgery.
Discuss the patient’s psychiatric history
A very common phenomenon seen in seizure centers is pseudoseizures. A pseudoseizure is not an actual seizure; it is a psychological event. The patient may believe they are having a seizure, but the seizure is not due to abnormal electrical activity of the brain.
Pseudoseizures can be seen in patients who also have bona fide seizures. If the patient is experiencing pseudoseizures and their real seizures are well-controlled, surgery would not be indicated. This can often be determined with prolonged video electroencephalography (EEG) monitoring.
How do you treat a patient with intractable epilepsy?
Develop a good understanding of the type of seizure the patient experiences. There are three common types of intractable epilepsy:
- Temporal lobe epilepsy
- Extratemporal epilepsy
- Multifocal epilepsy
Temporal lobe epilepsy
About 80% of epilepsy surgeries are performed for seizures arising from one of the temporal lobes. Temporal lobe epilepsy may be complex partial in nature or secondarily generalized.
Complex partial temporal lobe seizures
Complex partial seizures remain in the region of origin but can result in a change in consciousness. The patient will often experience an aura of disturbing smells, emotions, gastrointestinal sensations, and then stare off while exhibiting automatisms. Automatisms are complex but unintentional movements such as lip-smacking, pacing, or hand wringing. There is often a postictal state of decreased responsiveness and confusion that may last anywhere from a few minutes to half an hour.
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Secondarily generalized temporal lobe seizures
Complex partial seizures in the temporal lobe may become generalized, which means they have spread throughout the brain. These are accompanied by a loss of body tone, convulsing, a complete loss of consciousness, and prolonged postictal states that may last from a few minutes to an hour.
The site of origin and epicenter of a seizure is known as the seizure focus. In temporal lobe seizures, the seizure focus is usually located in the medial (e.g., mesial) portion of the lobe. Intractable epilepsy originating from the temporal lobe often responds quite well to various resective or ablative procedures of the medial temporal lobe structures, such as the hippocampus, amygdala, and regional cortices.
Minimally invasive procedures using fiberoptic laser energy have also been quite effective. In this procedure, a thin laser-equipped probe is passed into medial temporal lobe structures through a burr hole. Computer technology is used to deliver precise levels of heat energy to the structures to destroy them. The recovery is rapid, but long-term seizure control has yet to be conclusively determined.
Stereotactic radiation and focused ultrasound may also be used to ablate temporal lobe structures, although their efficacy has yet to be determined.
Similar to temporal lobe epilepsy, if a patient’s seizures can be localized to a specific area (e.g., a seizure focus) of the brain and resection or ablation of the area will not cause debilitating deficits, the area may be targeted for surgery. When a seizure focus is determined outside of the temporal lobe, it is referred to as an extratemporal focus.
Surgery for extratemporal lobe epilepsy is often not as successful as surgery for temporal lobe epilepsy. This is due to the proximity of the seizure focus to eloquent brain tissue (e.g., speech, motor, or vision areas).
Generalized seizures that arise from multiple areas of the brain will sometimes respond to sectioning the anterior two-thirds to three-quarters of the corpus callosum. This procedure is known as corpus callosotomy.
This is particularly effective in younger patients with drop attacks (also known as atonic seizures) where patients fall precipitously to the ground and often sustain injuries.
In severely affected young patients with a remote history of extensive prenatal hemispheric brain injury and resultant generalized seizures, multiple regions of the damaged tissue may be generating seizures that can rapidly spread to the entire brain.
Disconnection of the affected brain region from the rest of the brain (known as a functional hemispherectomy) can improve seizure control. Remarkably, children undergoing this procedure often improve in their neurological function on the hemiplegic side, and parents may comment after surgery that they feel as though they have gotten their child back.
Which patients with intractable epilepsy are surgical candidates?
All patients with intractable seizures, particularly young patients with temporal lobe epilepsy, should be considered potential candidates for surgery. However, it is important for them and their parents to understand that surgery is a long and involved process. Counsel the patient that consideration for surgery may be a 1–2 year process and will involve several EEG tests, multiple inpatient hospital stays, and possibly invasive EEG monitoring.
Warn the patient that it is possible to come through two years of testing and invasive monitoring and to be told that a definitive surgery cannot be performed. However, these patients will often be given alternative options.
What are some alternative treatments for intractable epilepsy?
Alternative options to surgery for epilepsy include vagal nerve stimulation, responsive neurostimulation, and deep brain stimulation. Vagal nerve stimulators suppress potential seizure activity through chronic pulsatile stimulation of the vagal nerve in the neck. In well-selected patients, a 50% reduction in seizure frequency is common.
Responsive neurostimulation delivers electrical signals to an epileptogenic region in response to epileptogenic activity to potentially suppress further generation of a seizure. On the other hand, deep brain stimulation delivers continuous pulsatile signals to regions of the brain, which may suppress distant electrical activity.
What should you expect after resection or ablation of the seizure focus?
If you are caring for a patient who has undergone recent seizure focus resection surgery, keep in mind that mood swings are common—especially with temporal lobe surgery. Be prepared to manage depression and anxiety. But, mood swings generally improve over a few months.
Do not discontinue anticonvulsant medications after any type of epilepsy surgery. Follow the patient for several months, and if they are seizure-free discuss slowly tapering off one medication at a time. Most patients are not able to eliminate all medications, but many can sustain significant reductions in dosages.
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- Cataltepe, O, and Jallo, G. 2019. Pediatric Epilepsy Surgery: Preoperative Assessment and Surgical Treatment. 2nd Edition. New York: Thieme. 2019.
- Geller, EB, Skarpaas, TL, Gross, RE, et al. 2017. Brain‐responsive neurostimulation in patients with medically intractable mesial temporal lobe epilepsy. Epilepsia. 58: 994-1004. PMID: 28398014
- Passaro, EA. 2020. Identification of Potential Epilepsy Surgery Candidates. Medscape. https://emedicine.medscape.com
- Vossler, DG, and Brandling-Bennet, EM. 2020. Epilepsy. Medscape. https://emedicine.medscape.com