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Tuesday, 22 July 2025

Understanding Seizure Classification 🧠

Hey future doctors! 👋 Let's dive into the fascinating world of seizure classification. 🩺✨


Seizures reflect abnormal electrical activity in the brain, but they don't all look alike. Some involve convulsions, others just subtle lapses in awareness. Classification matters—not just for tidy documentation, but for tailoring treatment and understanding prognosis.


Here's a quick breakdown:

1️⃣ Focal Onset Seizures

  • Start in one hemisphere. Think: a localised electrical storm.

    • With awareness preserved: The patient can describe what’s happening—tingling in one arm, flashing lights, déjà vu. These are often referred to as simple partial seizures (though that terminology is fading).
    • With impaired awareness: The person might stare blankly, fumble with objects, or speak incoherently, often without memory of the event. Historically called complex partial seizures.
    • Motor vs non-motor: Motor includes twitching, automatisms, or abnormal posturing. Non-motor may involve emotional shifts, sensory changes, or autonomic features (e.g. palpitations, epigastric rising).
    • Secondary generalisation: Focal seizures can evolve into bilateral tonic-clonic seizures—a vital detail for diagnosis and management.

    📍 Clinical tip: Ask detailed questions about aura—these sensory or experiential cues often precede focal seizures and offer insight into the cortical origin (e.g. occipital lobe → visual aura).

2️⃣ Generalised Onset:

  • Originate simultaneously in both hemispheres—global from the get-go.

    • Motor types: Includes tonic-clonic, myoclonic, and atonic seizures. Often dramatic and unmistakable.
    • Non-motor types: Most commonly absence seizures—brief lapses in awareness, often mistaken for daydreaming, especially in children.

    🧪 Pathophysiology note: Generalised seizures are thought to involve cortical and thalamic circuitry—disrupting consciousness in milliseconds.

3️⃣ Unknown Onset: When the onset is unclear.
4️⃣ Unclassified: Seizures that don't fit into the above categories.

Not all seizures fit neatly. When onset isn’t witnessed or EEG isn’t available, we label them as unknown onset. Some presentations (like neonatal seizures or those with overlapping features) remain unclassified until more data emerges



🔑 Key Factors in Classification:

  • Awareness: Is the patient conscious during the seizure?
  • Motor Involvement: Are there movements (e.g., jerking)?

🩺 Tip: Always ask about aura symptoms—they can hint at focal onset!

🧬 Why Classification Isn’t Just Academic

  • Medication targeting: Some antiepileptics work better for focal seizures (e.g. carbamazepine), but can worsen absence seizures. Knowing the type prevents harm.
  • Aetiology search: Focal seizures might signal a structural lesion (stroke, tumour). Generalised seizures often have genetic or idiopathic roots.
  • Patient education: Understanding seizure types helps patients explain their experiences, anticipate triggers, and adhere to treatment plans.
  • Safety planning: Motor involvement increases injury risk; awareness loss has implications for driving, machinery, swimming, and childcare.

📌 Risk Factors for Seizures:

  • Genetics: Certain epilepsy syndromes (e.g. juvenile myoclonic epilepsy) run in families.
  • Structural brain lesions: Trauma, post-stroke gliosis, congenital malformations.
  • Infections: Encephalitis, neurocysticercosis, even COVID-related encephalopathy.
  • Metabolic derangements: Hypoglycaemia, hyponatraemia, hepatic encephalopathy.
  • Toxic exposures: Alcohol withdrawal, stimulant use, benzodiazepine cessation.
🧠 Remember: A single seizure isn’t always epilepsy. Transient causes must be excluded before long-term treatment begins.

Knowing these helps with diagnosis & prevention!



🔍 Why Classification Matters:

  • Knowing seizure types helps:
  • Choose the right meds 💊
  • Identify underlying causes 🧠
  • Guide patient education 🗣️
  • 🚨 Did you know carbamazepine can worsen absence seizures?

👩‍⚕️ Case Vignette: Ben in Bega

Ben is a 17-year-old living in rural NSW who collapses at school during morning assembly. His peers report rhythmic jerking of both arms and legs, lasting around two minutes. He’s confused afterward, with no memory of the event. At the local hospital, his creatinine is normal, but they don’t have immediate access to an EEG. The junior doctor suspects a generalised tonic-clonic seizure but wonders if it could have been focal onset with bilateral spread.

Ben’s mother later shares that he’d been describing “weird flashes in his vision” and a metallic taste in the mouth the night before—symptoms dismissed as stress from exams. Now the question becomes: Was this a generalised seizure, or did it begin focally?

🩺 Clinical Reasoning

  • If focal onset is suspected, an MRI may be warranted to look for cortical abnormalities (e.g. gliosis or AVM).
  • If truly generalised from the start, an inherited epilepsy syndrome becomes more likely.
  • Antiepileptic choice matters: carbamazepine could worsen generalised epilepsy, while valproate or levetiracetam might be safer.
  • Without EEG access, history becomes even more vital—and aura reporting is gold.

🌾 Rural Context

In Ben’s case, timely EEG isn't available. Referral to a metropolitan centre means travel delays, and local clinicians rely heavily on history and pattern recognition to guide initial treatment. This isn't just a clinical exercise—it’s a real-world illustration of why seizure classification influences not just treatment, but access, cost, and outcome.

🗣️ Thought Prompt – Clinical Reasoning Edition

Imagine two patients:

  • ·       One with a rising epigastric sensation followed by staring and fumbling.
  • ·       Another who collapses with symmetrical jerking and no warning.

Would you order the same imaging? Choose the same medication? Advise the same lifestyle modifications?

Seizure classification isn’t just semantics—it’s the scaffolding that holds clinical reasoning together.


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