Epilepsy is a chronic disease characterised by repeated epileptic seizures, these seizures are the result of uncontrolled neuronal discharge.
Although the cause will be unknown in many cases, epilepsy is associated with traumatic brain injuries, anoxic encephalopathy, infectious processes, brain tumours, among other disorders.
Types of seizure
The same patient may be associated with several types of seizure which can be classified according to the alteration of the consciousness level as:
- Simple seizures: the level of consciousness is maintained during the seizure.
- Complex seizures: there is an alteration of the level of consciousness.
And according to their propagation:
- Partial seizures: only one specific brain area is activated.
- Generalised seizure: both brain hemispheres are activated.
The diagnosis will be mainly clinical, that is through the patient’s clinical record that indicates the types of seizure they suffer. Electrophysiological studies such as an electroencephalogram (EEG) and imaging tests including magnetic resonance imaging may aid in identifying the origin of the seizure and nowadays these tests are mandatory whenever an epileptic a seizure is suspected. In some complex cases other tests may also be required.
The first stage should be medical treatment for primary epilepsies without a clear aetiological factor, whereas in the event of injury related epilepsies and primary epilepsies with poor control of the seizure in spite of pharmacological treatment, surgery may be beneficial. Primary epilepsy requires a battery of preoperative tests that enable locating the epileptogenic focus with the greatest possible accuracy.
Types of surgery:
- Lesionectomy: the purpose is to remove the epileptogenic focus, whether tumoural or sclerotic as is the case of hippocampal sclerosis. This is the most often used technique for the treatment of epilepsy.
- Disconnection of the epileptogenic focus: in some cases the focus is located in an area of large eloquence (important function) where the resection of the area could cause severe post-surgical sequels and so disconnection of this area from the surrounding brain (multiple subpial transection) may be the treatment of choice. In some cases, the whole hemisphere must be isolated from the other healthy hemisphere and this involves a corpus callosotomy or hemispherotomy to isolate the patient’s healthy hemisphere.
- Vagus nerve stimulation: some cases refractory to aetiological treatment may benefit from this technique which consists of implanting an electrical impulse generator in the vagus nerve to provide small electrical stimuli through the nerve to the encephalon to control the seizure.
The type of surgery available will therefore depend on the location of the epilepsy. Epilepsy surgery may be classified as:
- A- Temporal lobe epilepsy surgery (the temporal lobe is the most common location of surgical epilepsy in adults)
- B- Extratemporal epilepsy surgery (frontal, occipital, parietal, insular, several lobes)