What Is Drug-Resistant Epilepsy?
By the international definition, epilepsy whose seizures cannot be controlled despite two appropriately chosen and adequately dosed antiseizure medications is considered 'drug-resistant'. This occurs in about one third of people with epilepsy. In drug-resistant epilepsy the chance that each additional drug will achieve seizure freedom falls markedly; at this point referral to an epilepsy centre for surgical assessment is recommended. Early assessment matters, because prolonged uncontrolled seizures can adversely affect cognition and quality of life. A surgical assessment does not necessarily mean an operation; its purpose is to determine whether the patient is a surgical candidate.
How Is the Seizure Focus Located?
The foundation of epilepsy surgery is to define the brain region where seizures begin (the epileptogenic focus) accurately and safely. This is a multistep process: seizures are recorded with prolonged video-EEG monitoring, and high-resolution epilepsy-protocol MRI is used to look for structural lesions (such as mesial temporal sclerosis, cortical dysplasia, cavernoma or tumor). When needed, PET, SPECT, neuropsychological testing and functional MRI mapping the language and memory areas are added. If the relationship between the focus and functional areas is unclear, further investigation with intracranial electrodes (stereo-EEG / invasive monitoring) may be performed. The decision is always multidisciplinary; the neurologist, neurosurgeon, neuroradiologist and neuropsychologist evaluate together.
Surgical Methods: Resective and Neuromodulation
Epilepsy surgery is not a single operation but a family of methods. In resective surgery the seizure focus is removed; the best-known and most successful example is the anterior temporal lobectomy / amygdalohippocampectomy performed for temporal lobe epilepsy due to mesial temporal sclerosis. For epilepsy caused by a single lesion (cavernoma, dysplasia, small tumor) a lesionectomy is carried out. When the focus is too extensive to remove or lies close to a functional area, 'disconnection' procedures that interrupt seizure spread (such as corpus callosotomy) or neuromodulation methods that aim to reduce seizure frequency when the focus cannot be removed (such as vagus nerve stimulation, VNS) come into question. The choice of method depends entirely on the seizure type, the location of the focus and the patient as a whole.
The Assessment and Recovery Process
The process begins with a detailed neurological history and a review of existing EEG/MRI records. For surgical eligibility, video-EEG and imaging are completed and a decision is made at a multidisciplinary meeting. A resective operation is performed under general anaesthesia; for foci close to language or memory areas, awake surgery and cortical mapping may be used when required. The procedure can take 2–5 hours depending on its type, followed usually by a short period of intensive care and a total hospital stay of a few days. Antiseizure medications are not stopped immediately after surgery; a gradual reduction under the neurologist's supervision is considered over a seizure-free period. Recovery and the establishment of seizure control can take weeks to months.
Risks and Realistic Expectations
Epilepsy surgery is brain surgery and its risks must be discussed honestly: bleeding, infection, and depending on the location of the focus, temporary or permanent effects on the visual field, memory or speech can occur; these risks are minimised by a detailed preoperative assessment. Outcomes vary by epilepsy type: in well-selected mesial temporal lobe epilepsy a substantial proportion of patients may achieve seizure freedom or a marked reduction in seizures over the long term, whereas neuromodulation generally aims at a reduction in frequency rather than seizure freedom. We do not promise a fixed rate or a guaranteed result; each patient's expectation is shared openly before surgery based on their own findings.