Overview
Definition:
A first unprovoked seizure is a single, sudden episode of abnormal, excessive, or synchronous neuronal activity in the brain that is not caused by an acute precipitating factor such as fever, metabolic disturbance, or head trauma.
Epidemiology:
The incidence of a first seizure in childhood varies, with estimates ranging from 2 to 10 per 10,000 children per year
The risk of recurrence is approximately 30-50% after a single unprovoked seizure
Etiologies are diverse, including genetic predisposition, structural brain lesions, and remote brain injury.
Clinical Significance:
Prompt and accurate diagnosis and management of a first unprovoked seizure are crucial to identify potential underlying serious conditions, reduce the risk of recurrence, prevent injury, and address parental anxiety
Understanding the appropriate use of neuroimaging and EEG guides this process effectively.
Clinical Presentation
Symptoms:
The seizure may manifest as motor symptoms (e.g., tonic, clonic, myoclonic, atonic movements), sensory symptoms (e.g., visual, auditory, or olfactory hallucinations), cognitive symptoms (e.g., déjà vu, jamais vu), or autonomic symptoms (e.g., nausea, flushing)
The presentation is highly dependent on the location and spread of the abnormal neuronal discharge.
Signs:
Physical examination may reveal postictal confusion, focal neurological deficits (transient or persistent), or evidence of trauma sustained during the seizure
It is crucial to perform a thorough neurological examination, including assessment for neurocutaneous markers like café-au-lait spots or shagreen patches.
Diagnostic Criteria:
Diagnosis of a first unprovoked seizure relies on a detailed seizure history, witnessed event description, and exclusion of provoked seizures
Provoked seizures are typically associated with acute insults such as febrile seizures, acute symptomatic seizures due to metabolic derangements (hypoglycemia, hyponatremia), toxic exposures, or acute CNS infections.
Diagnostic Approach
History Taking:
A detailed history is paramount
Key elements include the precise description of the event (onset, duration, motor activity, associated symptoms, any loss of consciousness), any preceding aura, postictal state, family history of seizures or epilepsy, developmental history, birth history (perinatal insults), and exposure to toxins or medications
Red flags include prolonged seizures, status epilepticus, focal neurological deficits, and history of head trauma or CNS infection.
Physical Examination:
A comprehensive physical examination is essential, including vital signs, general physical assessment, and a detailed neurological examination
Pay close attention to cranial nerves, motor strength, reflexes, sensation, coordination, and gait
Screening for developmental delays and dysmorphic features is also important
Examination of the skin for neurocutaneous stigmata (e.g., neurofibromatosis, tuberous sclerosis) should be performed.
Investigations:
Neuroimaging and EEG are key investigations
**Neuroimaging:** MRI brain is the preferred modality for identifying structural abnormalities
Indications include focal neurological deficits, atypical seizure semiology, abnormal neurological exam, and suspicion of a structural lesion
CT brain may be used in emergent situations if MRI is not readily available or if there is suspicion of acute hemorrhage or trauma
**EEG:** A standard 20-minute EEG is often performed, though prolonged or sleep-deprived EEGs may increase the yield
EEG helps characterize seizure type, identify epileptiform discharges, and guide management, but a normal EEG does not rule out epilepsy.
Differential Diagnosis:
Differential diagnoses for a first seizure include syncope (vasovagal, cardiac), psychogenic non-epileptic seizures (PNES), breath-holding spells, migraine aura, transient ischemic attacks, and movement disorders
Distinguishing features often lie in the precise description of the event, witnessed eyewitness accounts, and results of objective investigations like EEG.
Imaging And Eeg Selection
Imaging Indications:
Neuroimaging (preferably MRI brain) is indicated in most children presenting with a first unprovoked seizure
Specific indications include focal neurological deficits, abnormal neurological examination, atypical seizure semiology, developmental delay, suspicion of structural brain lesions (e.g., tumors, malformations, cortical dysplasia), and lack of clear precipitating factor
In infants and young children, brain imaging is generally recommended due to the higher likelihood of identifying an underlying etiology.
Eeg Indications:
EEG is indicated for all children with a suspected first unprovoked seizure
It aids in confirming the diagnosis of epilepsy, classifying the seizure type and epilepsy syndrome, and guiding antiepileptic drug (AED) selection
A normal interictal EEG does not exclude epilepsy, as abnormalities can be transient or provoked by sleep deprivation
Serial EEGs or long-term video-EEG monitoring may be considered in cases of diagnostic uncertainty or refractory seizures.
Interpretation Imaging:
MRI brain can identify a wide range of structural abnormalities including hippocampal sclerosis, cortical dysplasia, tumors, vascular malformations, and evidence of prior insult (e.g., stroke, trauma)
Findings on imaging can significantly influence prognosis and management decisions, potentially guiding neurosurgical intervention for focal epilepsy.
Interpretation Eeg:
EEG findings are categorized as normal, borderline, or abnormal (epileptiform discharges)
Epileptiform discharges include spikes, sharp waves, and spike-and-wave complexes
The location, morphology, and frequency of these discharges, along with the patient's clinical presentation and history, help in localizing the seizure onset zone and diagnosing specific epilepsy syndromes (e.g., absence epilepsy, Lennox-Gastaut syndrome).
Management And Follow Up
Initial Management:
The immediate management focuses on ensuring safety and preventing injury during a seizure
This includes protecting the airway, positioning the child safely, and administering benzodiazepines (e.g., intravenous or rectal diazepam, buccal midazolam) if the seizure is prolonged (e.g., >5 minutes) or in status epilepticus
A thorough metabolic workup (glucose, electrolytes, calcium, magnesium) is essential to rule out treatable causes.
Decision To Treat:
The decision to initiate long-term antiepileptic drug (AED) therapy after a first unprovoked seizure is individualized
Factors influencing this decision include the presence of risk factors for recurrence (e.g., abnormal EEG, abnormal neurological exam, symptomatic etiology, family history of epilepsy, prolonged seizures, nocturnal seizures)
Guidelines suggest that most children with a first unprovoked seizure and no risk factors may be observed without AEDs due to the risk of adverse effects and similar recurrence rates compared to placebo.
Pharmacological Treatment:
If AED therapy is initiated, first-line agents for generalized epilepsy include levetiracetam, valproic acid, and lamotrigine
For focal epilepsy, levetiracetam, carbamazepine, and oxcarbazepine are commonly used
Dosing should be weight-based and titrated to efficacy and tolerability
Careful consideration of side effect profiles and drug interactions is crucial.
Follow Up:
Children with a first unprovoked seizure, whether treated or not, require regular follow-up
This includes monitoring for seizure recurrence, assessing for AED side effects, and evaluating developmental progress
Follow-up frequency is typically every 3-6 months initially
Discontinuation of AEDs may be considered after a prolonged seizure-free period (e.g., 2-3 years) and after carefully weighing the risks and benefits.
Key Points
Exam Focus:
Focus on the indications for neuroimaging (MRI preferred) and EEG in a first unprovoked seizure
Understand the risk factors for recurrence that dictate the decision to start AEDs
Know common AEDs used in pediatric epilepsy and their initial doses.
Clinical Pearls:
Always obtain a detailed, witnessed account of the seizure event
Differentiate unprovoked from provoked seizures meticulously
A normal EEG does not exclude epilepsy
clinical suspicion remains paramount
Counsel parents thoroughly about seizure safety, risks of recurrence, and treatment options.
Common Mistakes:
Over-reliance on EEG alone without considering clinical history
Initiating AEDs empirically without assessing risk factors for recurrence
Failure to consider non-epileptic causes of paroxysmal events
Not performing a thorough neurological and physical examination.