Epilepsy - Diagnosis

⚡ Seizure Classification (ILAE 2017)

• Focal onset seizures
  • Originate in one hemisphere of the brain.
  • Defined by awareness at onset:
    • Focal aware seizure → patient remains conscious (previously “simple partial”).
    • Focal impaired awareness seizure → impaired consciousness or awareness (previously “complex partial”).
  • May progress to bilateral tonic-clonic seizure (old term: “secondary generalisation”).
  • Symptoms reflect cortical origin: • Temporal lobe → déjà vu, automatisms. • Occipital → flashing lights, visual distortions. • Frontal → bizarre motor activity, vocalisations. • Parietal → sensory disturbances, tingling.
• Generalized onset seizures
  • Involve both hemispheres from the onset.
  • Motor types: tonic-clonic, tonic, clonic, myoclonic, atonic, epileptic spasms.
  • Non-motor types: absence seizures (typical, atypical, or with special features such as myoclonic absence or eyelid myoclonia).
  • Often associated with strong genetic predisposition (e.g. childhood absence epilepsy, juvenile myoclonic epilepsy).
• Unknown onset seizures
  • Onset not observed or unclear (e.g. unwitnessed falls, nocturnal seizures).
  • Provisional category; may later be reclassified with EEG or clinical data.

🧠 Epilepsy Classification (ILAE 2017)

Epilepsies are classified at three hierarchical levels: 1) Seizure type → 2) Epilepsy type → 3) Epilepsy syndrome (where possible).

• Focal epilepsy – seizures consistently arise from one hemisphere. Examples: mesial temporal lobe epilepsy, post-stroke epilepsy.
• Generalized epilepsy – seizures engage networks in both hemispheres from onset. Examples: childhood absence epilepsy, juvenile myoclonic epilepsy.
• Combined generalized and focal epilepsy – both seizure types occur in the same patient. Example: Dravet syndrome.
• Unknown epilepsy – insufficient evidence to classify.

🧬 Epilepsy Aetiology Framework (ILAE 2017)

Classification also incorporates aetiology, which informs prognosis and management:

• Structural – brain injury or lesion (stroke, cortical dysplasia, tumour, trauma).
• Genetic – inherited or de novo variants, typically channelopathies (e.g. SCN1A mutations).
• Infectious – CNS infections (neurocysticercosis, viral encephalitis).
• Metabolic – inborn errors of metabolism (e.g. mitochondrial disease, GLUT1 deficiency).
• Immune – antibody-mediated encephalitis (e.g. anti-NMDA receptor encephalitis).
• Unknown – no cause identified despite evaluation.

📊 Visual Summary - Seizure Classification (ILAE 2017)

🧑‍⚕️ Case Examples - Seizure Types (ILAE 2017)

• Case 1 (Focal aware seizure - temporal lobe): A 25-year-old student describes sudden déjà vu, a rising epigastric sensation, and brief fear lasting under 1 minute. He remains fully conscious and can recall the event. Diagnosis: Focal aware seizure (temporal lobe).
• Case 2 (Focal impaired awareness seizure - temporal lobe): A 32-year-old woman is observed staring blankly and lip-smacking for about 90 seconds, followed by confusion for several minutes. She recalls nothing of the event. Diagnosis: Focal impaired awareness seizure (previously complex partial).
• Case 3 (Generalised tonic-clonic seizure): A 19-year-old man suddenly collapses, becomes rigid, then has generalised clonic jerks lasting 2 minutes. He is drowsy and confused afterwards (post-ictal phase). Diagnosis: Generalised tonic-clonic seizure.
• Case 4 (Typical absence seizure): An 8-year-old girl has frequent episodes where she suddenly stops talking, stares, and blinks rapidly for about 10 seconds, then resumes activity as if nothing happened. Teachers think she is daydreaming. Diagnosis: Generalised non-motor seizure (typical absence).
• Case 5 (Myoclonic seizure - juvenile myoclonic epilepsy): A 16-year-old boy describes sudden, brief jerks of both arms in the morning, sometimes causing him to drop objects. He later has a generalised tonic-clonic seizure after sleep deprivation. Diagnosis: Generalised motor seizure (myoclonic).
• Case 6 (Atonic seizure - drop attack): A 6-year-old child with developmental delay suddenly loses all muscle tone and collapses forward, recovering within seconds. He has recurrent injuries from similar episodes. Diagnosis: Generalised motor seizure (atonic seizure, “drop attack”).
• Case 7 (Infantile spasms / West syndrome): A 9-month-old infant develops sudden clusters of flexor spasms on waking, with loss of developmental milestones. EEG shows hypsarrhythmia. Diagnosis: Epileptic spasms (infantile spasms, West syndrome).
• Case 8 (Focal sensory seizure - parietal lobe): A 28-year-old man experiences tingling starting in his fingers and marching up his arm over 30 seconds, with full awareness. Symptoms resolve spontaneously. Diagnosis: Focal aware sensory seizure (parietal lobe, Jacksonian march).
• Case 9 (Occipital lobe seizure): A 10-year-old boy reports sudden flashes of bright colours in his visual field, followed by deviation of the eyes and head. Symptoms last under a minute and are stereotyped. Diagnosis: Focal aware visual seizure (occipital lobe).
• Case 10 (Status epilepticus): A 45-year-old man with epilepsy has a generalised tonic-clonic seizure lasting over 5 minutes without recovery, despite benzodiazepine given by paramedics. Diagnosis: Convulsive status epilepticus - a medical emergency.

🧑‍⚕️ Teaching Pearl

The ILAE 2017 classification stresses: • Onset type (focal, generalised, unknown). • Awareness status for focal seizures. • Specific motor vs non-motor features. 🌟 Using these structured terms avoids outdated labels and helps guide investigation (EEG, MRI) and treatment choice.