ANAESTHETIC IMPLICATIONS IN EPILEPSY SURGERIES

✔️If Awake Craniotomy/ wake up testing is planned, the procedure details should be explained to the patient, including what he/she is expected to hear and feel, inside the O.R.

✔️Get a brief description of the seizures and any prodromal symptoms 

✔️Continue anti epileptics through the morning of surgery

✔️Antiepileptics can reduce duration of action of NMBAs

✔️Usually a preoperative WADA test or fMRI would have been done, to check, whether the side of proposed surgery has any cerebral dominance or speech function 

✔️Abnormal LFTs can be expected with long term Valproate or Carbamazepine therapy

✔️WHAT THE COMMON AEDs DO?

✔️Phenytoin and Phenobarbitone: Reduce Hematocrit

Carbamazepine, Valproate,Ethosuximide and Primidone : Reduce platelet count

Carbamazepine and Primidone: Reduce WBC count

✔️If a difficult intubation is anticipated ( for e.g. After fixation of stereotactic frame ), an awake fibreoptic intubation can be considered 

✔️Moderate Sedation, if required can be achieved with Propofol 25-75 ug/kg/min plus Remifentanil 0.02-0.05 ug/kg/min OR Dexmedetomidine 1ug/kg/min over 10 minutes followed by 0.2-0.7 ug/kg/min

✔️Anticipated Surgical duration: 3 hours

✔️EBL: 250-500 ml ; blood transfusions are seldom needed

✔️Pain score 2-4

✔️If an Asleep-Awake-Asleep technique is used:

GA  continued for positioning, craniotomy and till the exposure of the surgical area. Then patient is allowed to awaken, to monitor neurological function during brain stimulation ( LMA removed OR  if ETT, it is removed over a tube exchanger). When seizure area, is fully delineated, GA is reinstituted.

AETIOLOGIES AND ASSOCIATED CONDITIONS IN PATIENTS COMING FOR EPILEPSY SURGERY

AETIOLOGIES 

〰〰〰〰〰

🏷Idiopathic (Mesial Temporal Sclerosis)

🏷Infectious (Brain Abcess, Encephalitis)

🏷Traumatic (glial scar)

🏷Vascular (AVM, Infarct)

🏷Neoplastic (glioma, hamartoma, ganglioglioma)

🏷Congenital (Cortical dysplasia)

ASSOCIATED CONDITIONS 

〰〰〰〰〰〰〰〰〰〰

🏷Tuberous Sclerosis

🏷Sturge Weber Syndrome 

🏷Infantile Hemiplegia

🏷Encephalitis

EPILEPSY SURGERY: OTHER APPROACHES

💈1) Frontal/temporal or occipital craniotomy for resection of a structural epileptogenic focus e.g. Tumour or AVM

🔺This may use stereotaxic localisation (by using a stereotaxic headframe, which may affect the method of intubation)

💈2) Diagnostic placement of surface or depth electrodes

 🔺Mostly only burr holes outlining the future craniotomy flap are used

🔺After placement, the electrodes are externalised and postoperatively patient’s naturally occurring seizures are recorded in conjunction with video monitoring, to register the clinical presentation, with the onset of seizure activity. This recording period may last for several days.

🔺This will be followed by resection of the epileptic focus, on another date.

💈3) Selective amygdalo-hippocampectomy

🔺Here, a cortical incision is made in the anterior temporal lobe and amygdala & hippocampus are resected

EPILEPSY SURGERY- VARIANT APPROACHES🙇🙇🏻🙇🏼🙇🏾: CORPUS CALLOSOTOMY

✔️Suited for patients with atonic or partial seizures with secondary generalisation 

✔️Either the anterior 2/3rd or the entire corpus callosum is divided in the midline

✔️Uses a bifrontal paramedian scalp incision and elevation of the free bone flap, adjacent to the midline in the region of the coronal suture

✔️Injury to the sagittal sinus can result in massive VAE or haemorrhage 

✔️Preserve the numerous bridging veins across the interhemispheric fissure; otherwise, can result in venous congestion and possible infarction 

✔️Right cerebral hemisphere is gently retracted from the falx: this will expose the paired anterior cerebral arteries and corpus callosum

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EPILEPSY SURGERY: SPECIFIC PROCEDURES & HIGHLIGHTS : TEMPORAL LOBECTOMY

✔️ Head turned 90* and held with pins

✔️ Most commonly a "question mark" temporal incision

✔️ a flap based on temporalis muscle elevated

✔️ a subtemporal craniectomy allows visualisation of entire anterior temporal lobe

✔️ anterior 6-6.5 cms of temporal lobe exposed

✔️ surface or depth electrocorticography employed

✔️ map the lesion

✔️ amygdala, hippocampus/ anterior temporal lobe removed 

✔️ Temporal lobectomy involves resection of both lateral and medial (uncus, hippocampal formation etc) temporal structures, mostly under an operating microscope

✔️ Complications: Injury to brainstem, 3rd and 4th cranial nerves , Middle or Posterior Cerebral arteries

✔️ closure of dura, bone flap and scalp concludes the surgery

#epilepsy , #seizures ,#neurosurgery , #EpilepsySurgery , #NeuroAnaesthesia ,#NeuroAnesthesia , #speech ,#wadatest

☁️EPILEPSY SURGERY: BASIC FACTS

☄Most beneficial in partial seizures secondary to a structural lesion

☄For determining the cerebral dominance and hence the location of speech , a WADA test (intracarotid injection of anesthetic to localize language function ; hence invasive) or recently functional MRI mapping (non invasive) of speech centres are done preoperatively 

☄Simultaneous recordings of video EEG and MRI or PET scans can show the epileptogenic focus

☄Temporal lobe surgery may involve:

✔️removal of only the structural lesion & associated epileptogenic cortex

✔️cortical resection alone

✔️excision of amygdala and hippocampus 

✔️removal of the entire anterior temporal lobe (extent of posterior resection dependent on dominance)

✔️depending on the local protocol, intraoperative Electro Corticogram (ECoG) may be used; anesthesia has to be modified accordingly

✔️if speech centre has to be located intraoperatively, an awake craniotomy is required

✔️ So depending on the surgical plan, choice of anesthesia varies