Epilepsy Surgery and Psychiatry Flashcards
What is the candidate criteria for epilepsy surgery?
▪️ Partial seizure with single focus
▪️ Must be possible to define focus accurately
▪️ Medically intractable (severe)
▪️ Benefits outweigh risks - location must not cause significant deficits
What is intractable focal epilepsy?
Epilepsy with focal onset that is very difficult to control or manage, principally diagnosed by history
What operations can be offered for intractable focal epilepsy?
▪️ Focal resection (remove single source, e.g., temporal lobectomy)
▪️ Major resection (remove larger region, e.g., hemispherectomy)
▪️ Disconnection (less common)
▪️ Functional (e.g., DBS, VNS)
What must you be aware of when diagnosing focal onset epilepsy?
Possibility of a psychogenic nature (not really epilepsy)
What does disconnection surgery, such as a callosotomy, do, and when might it be used?
▪️ Wont stop the seizure from happening but stops it from spreading, reducing injuries from loss of consciousness
▪️ When multiple focal sources
▪️ In children with LD who have frequent drop attacks
When might a hemispherectomy be performed?
▪️ Intractable partial epilepsy arising in one damaged hemisphere
▪️ Acceptable to lose all functions of that hemisphere (e.g., stroke during development so already hemiplegic, hemianopic etc)
What is a hemispherectomy?
A major resection involving the complete or partial removal of one hemisphere
What are the benefits and issues with hemispherectomy?
▪️ Very effective - up to 90% seizure freedom with no added deficits
▪️ BUT cerebral superficial haemosiderosis - dementing illness 10-15 years after from multiple injuries as brain moves around
What surgery if not performed instead of hemispherectomy?
Hemispherotomy
What is a hemispherotomy?
Disconnect cortex (callosotomy) and divide around thalamus so that the hemisphere is left in and blood supply is maintained but it is no longer connected to the rest of the brain
Seizures can still occur here but will have no impact
What is hippocampal sclerosis?
Frequent seizures in the temporal lobe get funnelled through the hippocampus, causing scarring and becoming an independent source of epilepsy
Very responsive to surgery (e.g., temporal lobectomy)
What are the main features of mesial temporal lobe epilepsy (hippocampus)?
▪️ Aura (abdominal, cephalic)
▪️ Initial behavioural arrest
▪️ Automatisms (particularly ipsilateral)
▪️ Contralateral dystonic posture
▪️ Post-ictal dysphasia
▪️ Post-ictal psychosis
▪️ Rare generalisation
When does the syndrome of the mesial temporal lobe typically occur?
▪️ Onset ~age 12
▪️ Alongside febrile convulsion (cause or effect?)
▪️ Alongside hippocampal sclerosis?
What surgery can be performed for mesial temporal lobe epilepsy?
En-bloc anterior temporal lobectomy
What surgery is HM a famous case of?
Bilateral hippocampus removal
What is the main risk of bilateral hippocampal/temporal lobectomy?
Profound memory disturbance
What do the Wada/amytal test for?
Hippocampal function to determine laterality of the problem and as a safety test to make sure the right hippocampus is removed
How does the Wada/amytal test work?
▪️ Anaesthetic on one side to imitate lesion
▪️ If damaged, memory won’t be affected
▪️ If healthy, patient will become amnestic
Also can establish language dominance
How might severe epilepsy directly lead to psychiatric disturbance?
▪️ Acute changes in brain chemistry (could also be protective like ECT?)
▪️ Social isolation
▪️ Educational difficulties
▪️ Stigma
What are the major causes of focal onset epilepsy?
▪️ Cavernoma (most common)
▪️ Tuberous sclerosis
▪️ Hippocampal sclerosis/mesial temporal lobe epilepsy
What is a cavernoma?
A cluster of abnormal blood vessels (capillaries) which can irritate the surrounding cortex, causing seizures
Foreign body so much less risky to remove
What is tuberous sclerosis?
A genetic condition that causes growth of benign tumours around the body, typically in cortical development
These tubers can form electrical short circuits - need to find which one is causing seizures (likely just one if all seizures are similar)
How might antiepileptic medications lead to psychiatric disturbances?
▪️ Changes in brain chemistry
▪️ Sedation
▪️ Educational difficulties
▪️ Depression (levetiracetam) - link hard to establish due to study on tumours
▪️ Speech disturbance (topiramate)
How might underlying causes associated with epilepsy increase risk of psychiatric disturbance?
▪️ Structural abnormalities (e.g., frontal meningioma)
▪️ Functional abnormalities
▪️ High comorbidity with psychiatric disease
What psychiatric conditions are most common amongst candidates for epilepsy surgery?
▪️ Anxiety and depression
▪️ Psychosis (inter-ictal, post-ictal, alternative)
▪️ Ictal behaviours (e.g., auditory hallucinations)
(Around half of patients!)
What type of epilepsy is commonly associated with postictal psychosis and how does it typically present?
▪️ Temporal lobe epilepsy
▪️ Hypergraphia, hyper religiosity
What implications might psychiatric diagnosis have on epilepsy surgery?
▪️ More likely to progress due to increased risk-taking? (as seen in PD and ICD with DBS)
▪️ Less likely to progress due to mismatch between predicted and actual operations?
How might surgery effect psychiatric state?
▪️ Structural changes (e.g., frontal lobe, hippocampal lobe)
▪️ Major life event
▪️ Electrochemical changes
▪️ Burden of normality
How might surgery for epilepsy concerning the frontal lobe affect psychiatric state?
Induced apathy, personality change, or theory of mind
How might temporal lobe surgery and hippocampal volume affect psychiatric state?
▪️ Significantly increased risk of depressive illness during first 12 months after
▪️ Risk inversely proportional to size of hippocampus (e.g., shrunken on one side = high risk)
How might the circumstances surrounding surgery increase risk of psychiatric illness?
▪️ Association between major life events and depression
▪️ Anti-climax of still being at risk (expect more than is realistic)
▪️ Some go through a sort of grieving over seizures
▪️ Anxiety of no seizures - rises as time goes on, expecting a big one
▪️ Potential lack of social benefit from too-late
How long does it typically take someone to get used to the idea of seizure freedom post surgery?
Around 9 months - often grieve loss or get increasing anxiety as they expect a big one to come
How might electrochemical changes following surgery contribute to psychiatric disturbance?
▪️ Loss of regular ‘ECT’, exposing underlying depression/mood disturbance?
▪️ Forced normalisation
▪️ Drug changes (e.g., loss of valproate which may have been stabilising mood)
What is forced nromalisation?
The emergence of psychoses following seizure control (~2% following surgery)
Mechanisms not quite understood but due to rapid change from severe seizures to none at all?
What is the burden of normality and how might is cause psychiatric disturbance?
Difficulties re-integrating into ‘normal’ world having been brought up as an ‘epileptic’
May cause disturbance through loss of benefits, loss of ‘sick role’, or too late to re-establish social group
What is the main benefit of awake surgery?
To ensure function is still intact
What can you use instead to avoid awake surgery?
Intracranial mapping - series of electrodes over area (e.g., double density mat over PMC for precise motor mapping)
What is a hypothalamic hamartoma?
A developmental condition that causes an abnormality in the hypothalamus which leads to:
▪️ Appetite issues
▪️ Puberty issues
▪️ Learning difficulties
▪️ Galsatic seizures (laughing)
How can thermocoagulation under local anaesthetic be used to ensure eloquent tissue is preserved during surgery?
▪️ Probe placed in an area, gradually heating up
▪️ At 45 degrees, the tissue stops working
▪️ Check for side effects
▪️ If not side effects, can heat to 85 degrees to burn the tissue and shrink it away
What is stereotactic radiosurgery?
Focused radiation to target precise areas
(102 electrodes producing rays of high frequency radiation directed to specific areas)
What are the advantages of stereotactic radiosurgery?
▪️ Minimal operative trauma
▪️ No disruption of psychosocial life
▪️ Cost benefit
▪️ Reduced hospitalisation
▪️ Promising neuropsychological effects
What are the disadvantages of stereotactic radiosurgery?
▪️ Delayed seizure cessation/transient worsening
▪️ Delayed psycho-social benefit
▪️ Small therapeutic window
▪️ SUDEP risk
▪️ Lack of data evidence
▪️ 9 month ‘crisis’?
What are the main advantages of stereotactic radiosurgery?
▪️ No disruption of psychosocial life
▪️ Cost benefit/reduced hospitalisation
▪️ Promising neuropsychological data
How can you use DBS in refractory epilepsy?
Target areas that are difficult to resect
E.g., anterior nucleus, thalamus, temporal areas
What could you use for seizures originating in eloquent cortex where the risk from surgery is high?
Chronic cortical stimulation
What is Responsive Neurostimulation?
Implanted defibrillator that sends shocks when seizure starts
▪️ Closed loop system
▪️ Detects EcoG evidence of seizure
▪️ Delivers pulse to abort seizure
BUT only in US, tech is a bit outdated
Why is vagus nerve stimulation thought to help with refractory epilepsy?
▪️ Inhibitory effect on glutamate, increasing GABA?
▪️ Training the brain to fight seizures better?
▪️ Antidepressant effect or memory benefits - improves QoL due to improvement in functioning, not seizure freedom?
