Overview
Definition:
Presurgical evaluation for epilepsy surgery in children aims to identify candidates with medically intractable focal epilepsy who are likely to benefit from surgical resection or disconnection, while minimizing risks of neurological deficits
It is a multidisciplinary process involving neurologists, neurosurgeons, neuroradiologists, neuropsychologists, and EEG technologists.
Epidemiology:
Epilepsy affects approximately 1% of the pediatric population worldwide, with a significant proportion experiencing drug-resistant epilepsy (up to 30-40%)
Surgical intervention is considered for a subset of these children after comprehensive evaluation, potentially offering seizure freedom or significant seizure reduction.
Clinical Significance:
For pediatric residents preparing for DNB and NEET SS examinations, understanding the presurgical workup is crucial
It enables accurate patient selection, appropriate referral, and comprehension of the multidisciplinary approach required for optimal outcomes in children with intractable epilepsy
This can lead to improved quality of life, cognitive development, and reduced morbidity.
Clinical Presentation
Symptoms:
Seizures refractory to at least two appropriately chosen and dosed AEDs
Frequent seizures impacting daily life, schooling, and development
History suggestive of a specific ictal semiology that may localize to a particular brain region
Developmental delay or cognitive impairment potentially related to frequent seizures or underlying etiology.
Signs:
Focal neurological deficits (e.g., hemiparesis, visual field defects) on examination
Evidence of dysmorphism or stigmata of a neurocutaneous syndrome
Abnormal EEG findings, including focal interictal epileptiform discharges or ictal onset patterns.
Diagnostic Criteria:
The primary criterion for surgical consideration is medically intractable epilepsy, defined as persistent disabling seizures despite adequate trials of at least two AEDs
Seizures must be focal and originate from a brain region that can be safely removed or disconnected without causing unacceptable neurological deficits
The underlying etiology should ideally be identified to aid localization and prognosis.
Diagnostic Approach
History Taking:
Detailed seizure history including frequency, duration, semiology, and timing
Family history of epilepsy or neurological disorders
Developmental milestones and educational progress
Previous treatments and their efficacy
Any history of brain injury, infection, stroke, or genetic syndromes
Red flags include prolonged postictal confusion, stereotyped seizures, and a lack of response to multiple AEDs.
Physical Examination:
Comprehensive neurological examination including assessment of cranial nerves, motor strength, sensation, reflexes, coordination, and gait
Detailed scalp and funduscopic examination
Assessment for stigmata of genetic or congenital syndromes (e.g., facial features, skin lesions).
Investigations:
Electroencephalography (EEG): Routine scalp EEG, prolonged video-EEG monitoring to capture habitual seizures, identify ictal patterns, and determine seizure onset
Ictal SPECT (single-photon emission computed tomography) to localize hyperperfusion during seizures
MRI brain: High-resolution structural MRI with epilepsy protocol to identify structural lesions (e.g., cortical dysplasia, tumors, hippocampal sclerosis, vascular malformations)
Functional MRI (fMRI) for language and motor mapping
MEG (magnetoencephalography) for non-invasive localization of epileptogenic zones
Neuropsychological testing: Assessment of cognitive function, memory, and behavior to establish baseline and predict the impact of surgery
Invasive EEG monitoring (stereo-EEG or subdural grids) may be required for complex cases or when non-invasive methods are inconclusive.
Differential Diagnosis:
Conditions that may mimic epilepsy include syncope, psychogenic non-epileptic seizures (PNES), movement disorders, migraines with aura, and transient ischemic attacks
Careful clinical correlation with ictal semiology, EEG findings, and neuroimaging is essential to differentiate these from true epileptic seizures and to localize the epileptogenic zone accurately.
Management
Initial Management:
Comprehensive presurgical evaluation as described above is the initial step
This involves a multidisciplinary team assessment to determine eligibility for surgery and to identify the epileptogenic zone
Detailed discussion with the family regarding risks, benefits, and expected outcomes of different surgical options.
Medical Management:
Although the focus is on surgical candidates, appropriate medical management with AEDs continues until surgery to control seizures as much as possible and to minimize risks
Decisions regarding AED withdrawal or continuation are made in consultation with the surgical team.
Surgical Management:
Surgical options include resective surgery (e.g., temporal lobectomy, extratemporal resection of lesions like cortical dysplasia or tumors) or disconnection procedures (e.g., corpus callosotomy, hemispherotomy)
Laser interstitial thermal therapy (LITT) is an emerging minimally invasive option for select lesions
The choice depends on the location and extent of the epileptogenic zone and the potential neurological deficits.
Supportive Care:
Psychological support for the child and family is paramount
Nutritional assessment and support
Ongoing monitoring of seizure control and potential complications post-surgery
Rehabilitation services may be required.
Complications
Early Complications:
Surgical site infection
Bleeding or hematoma
Stroke
Neurological deficits (e.g., aphasia, hemiparesis, visual field deficits)
Seizure worsening or status epilepticus
Hydrocephalus.
Late Complications:
Persistent neurological deficits
Cognitive decline
Development of new seizure types
Psychiatric complications
Impact on growth and development
Visual field defects impacting daily life and schooling.
Prevention Strategies:
Meticulous surgical planning to avoid eloquent brain areas
Careful intraoperative monitoring
Prophylactic antibiotics and antiepileptic medications
Prompt recognition and management of post-operative seizures or complications
Thorough pre-operative neuropsychological assessment to predict and mitigate cognitive deficits.
Prognosis
Factors Affecting Prognosis:
Location and extent of the epileptogenic zone
Etiology of epilepsy
Extent of resection
Presence of pre-existing neurological deficits
Age of the child at surgery
Quality of pre-surgical evaluation and multidisciplinary team expertise
Degree of seizure reduction or freedom post-surgery.
Outcomes:
Successful epilepsy surgery can lead to significant seizure reduction or complete seizure freedom in 50-80% of appropriately selected pediatric patients
This can result in improved cognitive function, academic performance, social integration, and overall quality of life
However, some children may continue to have seizures or develop new neurological deficits.
Follow Up:
Regular follow-up appointments with the neurology and neurosurgery teams are essential
This includes ongoing seizure monitoring, neurological examinations, and periodic neuropsychological assessments
Long-term AED management may still be required, although dosages can often be reduced or discontinued if seizure-free
The goal is to optimize long-term neurological and developmental outcomes.
Key Points
Exam Focus:
DNB/NEET SS exam questions will likely focus on identifying candidates for surgery, interpreting EEG and MRI findings in the context of presurgical evaluation, and understanding the common investigations and multidisciplinary team roles
Differentiating between focal and generalized epilepsy, and understanding the concept of intractable epilepsy are key.
Clinical Pearls:
Always consider epilepsy surgery in children with drug-resistant focal epilepsy
A coordinated multidisciplinary team approach is non-negotiable for optimal patient selection and care
Video-EEG is the gold standard for characterizing seizures and localizing the onset
Neuropsychological testing is vital for predicting outcomes and guiding surgical decisions.
Common Mistakes:
Delaying referral for presurgical evaluation in children with presumed intractable epilepsy
Inadequate history taking regarding seizure semiology
Misinterpreting EEG or imaging findings
Overlooking the importance of neuropsychological assessment
Failure to involve the entire multidisciplinary team in decision-making.