Epilepsy and Pain
Questions pair a seizure semiology and MRI finding with a surgical option, or a pain syndrome with an ablative or neuromodulatory procedure.
Presurgical evaluation
You must show that the epileptogenic zone is resectable and does not overlap eloquent cortex. The sequence is a dedicated 3T MRI with thin slices perpendicular to the hippocampus, video-EEG capturing an ictal event, neuropsychology, then functional imaging with ictal SPECT, FDG-PET or MEG, and invasive recording with depth electrodes or subdural grids when non-invasive data conflict.
Surgical options
- Hippocampal sclerosis is the commonest remediable lesion; anterior temporal lobectomy gives Engel class I outcome in roughly 60 to 70 percent at two years.
- Lesionectomy for focal cortical dysplasia, tuberous sclerosis tubers and low-grade tumour.
- Hemispherotomy for hemispheric disease such as Sturge-Weber, Rasmussen encephalitis and hemimegalencephaly.
- Corpus callosotomy for drop attacks, particularly in children.
- Palliative options: vagus nerve stimulation and responsive neurostimulation; ketogenic diet in children.
Status epilepticus
Escalate in stages: a benzodiazepine such as intravenous lorazepam, repeated once; then a second-line agent in full dose, levetiracetam, valproate or fos-phenytoin; then anaesthesia with midazolam, propofol or thiopentone under EEG monitoring. Always check glucose, sodium, calcium, drug levels and infection.
Pain surgery
- Anterolateral cordotomy for unilateral cancer pain below the neck.
- Dorsal root entry zone lesioning for brachial plexus avulsion and root avulsion pain.
- Intrathecal opioids or baclofen for diffuse pain and spasticity; spinal cord stimulation for failed back surgery syndrome and complex regional pain syndrome.
- Glossopharyngeal neuralgia may cause syncope; microvascular decompression is effective.
Worked example
A 30-year-old has monthly focal impaired awareness seizures. MRI shows right hippocampal atrophy with T2 hyperintensity and video-EEG confirms right temporal onset; the Wada test shows left language dominance. Anterior temporal lobectomy is offered with counselling on superior quadrantanopia, verbal memory risk and a realistic chance of seizure freedom.
Traps
- Operating on a non-lesional case without an ictal recording.
- Under-dosing second-line agents in status epilepticus.
- Choosing vagus stimulation when a curative resection is possible.
- Forgetting that cordotomy is for unilateral pain.