What is the appropriate treatment for a patient with a history of seizures, presenting with a recent seizure, and requiring classification of seizure type to guide treatment decisions?

Seizure Classification to Guide Treatment

Classify seizures as provoked versus unprovoked first, then determine if focal or generalized, as this fundamental distinction directly determines treatment approach and prognosis. 1

Primary Classification Framework

Provoked vs. Unprovoked Seizures

The most critical initial classification is determining whether the seizure is provoked (acute symptomatic) or unprovoked, as provoked seizures require treatment of the underlying cause rather than antiepileptic drugs. 1

• Provoked seizures occur at the time of or within 7 days of an acute neurologic, systemic, metabolic, or toxic insult 1, 2
• Unprovoked seizures occur without acute precipitating factors and include remote symptomatic seizures (from insults >7 days prior) and idiopathic seizures 1, 2

Common Provoked Seizure Etiologies to Identify

Look specifically for these reversible causes through history, examination, and targeted laboratory testing:

• Metabolic derangements: Hypoglycemia, hyperglycemia, hyponatremia, hypocalcemia, hypomagnesemia, and uremia 1, 2
• Toxic ingestions: Cocaine, tricyclic antidepressants, antihistamines, theophylline 2
• Withdrawal states: Alcohol withdrawal (diagnosis of exclusion, especially in first-time seizures) 1
• CNS infections: Encephalitis, meningitis (particularly in immunocompromised patients) 2
• Acute structural lesions: Intracranial hemorrhage, stroke, CNS mass lesions 2

Secondary Classification: Focal vs. Generalized

After determining provoked versus unprovoked status, classify the seizure type as focal or generalized, as this determines antiepileptic drug selection and need for neuroimaging. 3

Focal Seizures

Any focal feature to a seizure mandates neuroimaging due to high yield for clinically relevant structural abnormalities. 3

Focal seizure features include:

• Motor asymmetry: Hemiparesis, unilateral clonic movements 3
• Sensory symptoms: Referable to specific brain regions 3
• Cortical signs: Aphasia, visual field defects, specific sensory disturbances 3
• Impaired awareness: Focal seizures with altered consciousness 3
• Evolution pattern: Focal onset that evolves to bilateral tonic-clonic activity 3

Focal seizures have recurrence rates up to 94% compared to 72% for generalized seizures, making accurate classification prognostically important. 3

Generalized Seizures

• Generalized seizures rapidly affect both hemispheres and both sides of the body from onset 3
• These may still result from focal lesions but manifest with bilateral involvement immediately 3
• Neuroimaging yield is low (only 2%) in neurologically normal patients with generalized seizures given their typical genetic basis 3

Diagnostic Approach by Clinical Presentation

For Otherwise Healthy Patients Returned to Baseline

In patients who have returned to baseline neurologic status, history and physical examination predict the majority of laboratory abnormalities. 1

• Check glucose in all patients, as hypoglycemia is the most common unsuspected abnormality (though rare at <1% of cases) 1
• Check sodium if history suggests water intoxication or other risk factors 1
• Routine calcium, magnesium, and phosphate testing is not supported by evidence in otherwise healthy patients 1

For Patients with Red Flags

Patients with altered mental status, fever, or new focal neurologic deficits require extensive evaluation including neuroimaging and broader laboratory testing. 1

• Fever warrants strong consideration of CNS infection 2
• Focal neurologic findings have 97% correlation with symptomatic (provoked) seizures 2
• Persistent focal deficits or failure to return to baseline within several hours mandates emergent neuroimaging 2

Neuroimaging Strategy

CT Scanning

Non-contrast CT is the initial imaging modality for acute seizure presentations to rapidly identify hemorrhage, stroke, mass lesions, or hydrocephalus requiring immediate intervention. 3

• Detection rate is 50% when neurologic findings are focal versus only 6% without focal features 3

MRI Scanning

MRI is superior to CT and should be the primary imaging modality for newly diagnosed seizures, particularly focal seizures, as it detects abnormalities missed by CT in 47% of cases. 3

• Use dedicated epilepsy protocols with 3T scanners including T1-weighted volumetric acquisition with 1mm isotropic voxels 3
• Include high-resolution coronal slices optimized for hippocampal pathology 3
• MRI is rarely indicated in neurologically normal patients with generalized seizures given low yield 3

Treatment Implications by Classification

Provoked Seizures

Treat the underlying cause; antiepileptic drugs are not indicated for provoked seizures. 4, 5

• Correct metabolic abnormalities 5
• Manage infections appropriately 5
• Control blood pressure in renal failure patients with seizures 5
• Phenytoin is ineffective for alcohol withdrawal seizures and seizures from theophylline or isoniazid toxicity 5

Unprovoked Seizures

Antiepileptic drug selection depends on whether seizures are focal or generalized. 4

For focal (partial-onset) seizures:

• Most antiepileptic drugs are effective as monotherapy 4
• Options include lamotrigine, topiramate, and others 6, 7, 4

For generalized seizures:

• Valproate, lamotrigine, and topiramate are preferred 4
• These agents show superior efficacy for primary generalized tonic-clonic seizures 7, 4

Common Pitfalls to Avoid

• Do not label first-time seizures as alcohol withdrawal without excluding other causes, as this should be a diagnosis of exclusion 1
• Do not assume all patients with seizures have epilepsy—most medically ill patients with secondary seizures do not have epilepsy and this should be explained to patients and families 5
• Do not continue long-term antiepileptic drugs for provoked seizures unless recurrent seizures occur with uncorrectable predisposing factors 5
• Do not skip neuroimaging in patients with focal features, as yield is high and treatment may be altered 3