What is the diagnosis and treatment for a patient presenting with their first episode of a generalized tonic-clonic (GTC) seizure?

First Episode of Generalized Tonic-Clonic Seizure: Diagnosis and Management

Initial Diagnosis

A first generalized tonic-clonic (GTC) seizure requires distinguishing between provoked (symptomatic) and unprovoked seizures, as this fundamentally determines both immediate management and long-term prognosis. 1

Key Diagnostic Features to Establish

History from patient and witnesses:

• Circumstances before the event: Look for prolonged standing, pain, medical procedures (suggests vasovagal syncope, not seizure), versus aura, unusual smells, or no clear trigger 1
• During the event: Tonic-clonic movements that start at onset of unconsciousness and are prolonged (>15 seconds), hemilateral clonic movements, automatisms like lip-smacking or chewing, tongue biting, cyanosis, hypersalivation 1, 2
• After the event: Prolonged confusion, muscle aching, disorientation (seizure) versus brief confusion with quick return to baseline (syncope) 1
• Timing and triggers: Identify any acute precipitants like alcohol use, drug ingestion, recent head trauma, fever, or metabolic disturbances 1

Essential Laboratory Testing

For otherwise healthy adults who have returned to baseline neurological status:

• Serum glucose and sodium - these are the most common metabolic abnormalities and occasionally unsuspected 1, 3
• Pregnancy test for all women of childbearing age - affects testing, disposition, and antiepileptic drug selection 1
• Complete blood count (CBC) to evaluate for infection or hematologic abnormalities 3
• Basic metabolic panel including BUN, creatinine, and electrolytes 3
• Calcium and magnesium levels, especially in older adults on medications affecting these electrolytes 3

Additional testing based on clinical context:

• Drug screen if substance use suspected 1, 3
• Extended electrolyte panel (phosphate) for patients with renal insufficiency, malnutrition, or on diuretics 1
• Lumbar puncture after head CT for immunocompromised patients, those with fever, or signs of meningeal irritation 1, 3

Important caveat: Laboratory testing has very low yield in patients who have returned to baseline, with most abnormalities predicted by history and physical examination 1, 3

Neuroimaging Requirements

Head CT scan is indicated for:

• All older adults with new-onset seizures to evaluate for structural lesions 3
• Patients with focal neurological deficits, altered mental status, or suspected structural lesion 1
• When etiology is unknown 1

MRI is preferred when:

• Available and patient is stable 3
• CT is negative but clinical suspicion for structural abnormality remains high 3
• For neurologically normal children with primary generalized seizures, MRI is rarely indicated as the yield is very low (only 2% of low-risk patients have abnormal findings) 1

EEG Timing and Utility

• EEG should be performed within 24 hours after a seizure, particularly in children 2
• If normal during wakefulness, a sleep EEG is recommended 2
• Interictal EEGs are normal in syncope; a normal EEG cannot rule out epilepsy but must be interpreted in clinical context 1

Classification: Provoked vs. Unprovoked Seizures

Provoked (symptomatic) seizures occur in close temporal relationship to:

• Systemic disorders (hypoglycemia, hyponatremia, hypocalcemia)
• Acute brain insults (stroke, head trauma, infection)
• Alcohol withdrawal (though this should be a diagnosis of exclusion in first-time seizures) 1, 4

Unprovoked seizures occur in the absence of acute precipitants but may have:

• Remote symptomatic causes (prior stroke, traumatic brain injury, CNS disease)
• Idiopathic/genetic predisposition
• No identifiable cause 1, 4

Treatment Decisions

For Provoked Seizures

Emergency physicians need not initiate antiepileptic medication in the ED for patients with provoked seizures. 1 Instead:

• Identify and treat the precipitating medical condition 1
• Symptomatic therapy is not justified unless the seizure has characteristics of status epilepticus 2

For Unprovoked Seizures Without Brain Disease

Emergency physicians need not initiate antiepileptic medication in the ED for patients with a first unprovoked seizure without evidence of brain disease or injury. 1

Rationale:

• Approximately one-third to one-half of patients with a first unprovoked seizure will have recurrence within 5 years 1
• Treatment initiated within days to weeks prolongs time to subsequent event, but outcomes at 5 years are no different 1
• Number needed to treat is 14 patients to prevent a single seizure recurrence within first 2 years 1
• Treatment does not improve long-term prognosis of epilepsy 5
• 50% of untreated patients will never experience a second seizure 5

For Unprovoked Seizures With Remote Brain Disease/Injury

Emergency physicians may initiate antiepileptic medication in the ED, or defer in coordination with other providers, for patients with a first unprovoked seizure and remote history of brain disease or injury (stroke, traumatic brain injury, tumor). 1

Rationale:

• History of CNS injury increases seizure recurrence risk substantially 1
• These patients have anatomic or physiologic substrate for recurrent seizures 1
• Treatment is considered appropriate after one seizure in this population 1

For Patients With Generalized Spike-Wave Discharges on EEG

Patients with a first unprovoked GTC seizure and generalized spike-wave discharges on EEG have a 68.8% recurrence risk if untreated versus 14.6% if treated, making treatment strongly advisable. 6

Medication selection for this population:

• Valproate is the most efficacious antiseizure medication for preventing recurrence 6
• Levetiracetam and lamotrigine are less efficacious alternatives 6
• 40% of patients who discontinue medication after 30 months of seizure freedom experience recurrence 6

Disposition

Emergency physicians need not admit patients with a first unprovoked seizure who have returned to their clinical baseline in the ED. 1

Critical Pitfalls to Avoid

• Alcohol withdrawal seizures should be a diagnosis of exclusion, especially in first-time seizures 1, 3
• Do not perform routine calcium, magnesium, or phosphate testing in otherwise healthy patients without specific clinical indicators 1
• Do not perform lumbar puncture on alert, oriented, afebrile, immunocompetent patients 1
• Do not confuse brief myoclonic jerking after syncope with true epileptic seizures - this does not require neurologic investigation 1
• Do not order EEG, carotid ultrasound, or brain imaging when syncope is the most likely cause 1