Epilepsy Study Guide

📖 Core Concepts Epilepsy – a set of brain disorders marked by ≥ 2 unprovoked seizures > 24 h apart (or a single seizure with ≥60 % 10‑yr recurrence risk). Seizure – sudden, excessive, synchronized neuronal firing that may cause loss of awareness, motor jerks, or convulsions. Seizure classification (ILAE 2025) – Focal, Generalized, Unknown onset, Unclassified. Ictogenesis – the moment the balance of excitation ↔ inhibition collapses, producing a paroxysmal depolarizing shift and a seizure. Epileptogenesis – progressive changes (cell loss, gliosis, network re‑organization) that turn a once‑normal brain into a seizure‑prone one. Status epilepticus – seizure activity lasting ≥5 min (or repeated seizures without full recovery). Post‑ictal state – recovery period after a seizure; can last minutes to days and may include confusion, headache, Todd’s paralysis, or psychosis. Drug‑resistant epilepsy – failure of ≥2 appropriately chosen, tolerated antiseizure meds at optimal doses. --- 📌 Must Remember Diagnostic criteria: ≥2 unprovoked (or reflex) seizures >24 h apart, or 1 unprovoked seizure + ≥60 % 10‑yr recurrence risk, or A defined epilepsy syndrome. First‑line meds: Generalized seizures: Valproate (first line), Lamotrigine (2nd line). Absence seizures: Ethosuximide or Valproate. Focal seizures: Levetiracetam or Valproate (cost/side‑effect considerations). Teratogenic hierarchy (lowest → highest risk): Leviteracetam ≈ Lamotrigine < Valproate > Phenytoin > Carbamazepine > Phenobarbital > Gabapentin. Driving eligibility: seizure‑free for 3 months–3 years depending on jurisdiction; risk of motor‑vehicle collisions ≈ 2× the general population. SUDEP risk factors: uncontrolled generalized tonic‑clonic seizures, nocturnal seizures, sleeping alone, refractory epilepsy. Seizure clusters: ≥2 seizures within 24 h (or a noticeable rise over baseline). --- 🔄 Key Processes Seizure onset → propagation (ictogenesis) Loss of inhibitory control → paroxysmal depolarizing shift → rapid, synchronous firing → clinical seizure. Epileptogenesis timeline (after an insult) Acute injury → neuronal loss & gliosis → synaptic re‑organization → chronic hyper‑excitable network → spontaneous seizures. Acute management of a generalized tonic‑clonic seizure Stay calm, clear hazards. Gently guide to ground; turn to recovery position. No restraints, no objects in mouth. Time seizure; >5 min → call EMS (possible status). Status epilepticus treatment algorithm Step 1: Benzodiazepine (IV lorazepam or buccal midazolam). Step 2: If still seizing, give levetiracetam, phenytoin, or valproate (levetiracetam preferred). Pre‑surgical epilepsy evaluation Detailed seizure semiology → long‑term video EEG → high‑resolution MRI → neuropsych testing → (optional) PET/SPECT/invasive monitoring → multidisciplinary decision. --- 🔍 Key Comparisons Focal vs. Generalized seizures Onset: one brain region → may spread vs. bilateral simultaneous onset. Consciousness: often preserved in focal‑aware; usually impaired in generalized tonic‑clonic. Valproate vs. Lamotrigine (generalized seizures) Efficacy: Valproate > Lamotrigine. Teratogenicity: Valproate high risk; Lamotrigine low risk. Ethosuximide vs. Valproate (absence seizures) Target: Ethosuximide blocks T‑type Ca²⁺ channels → ideal for pure absence. Broadness: Valproate works on multiple seizure types but higher side‑effect profile. Ketogenic diet vs. Modified Atkins Efficacy: Classic ketogenic ≈ 3× higher seizure‑freedom in children. Tolerability: Modified Atkins better tolerated, slightly less effective. --- ⚠️ Common Misunderstandings “All seizures are epilepsy.” – Provoked (e.g., fever, hypoglycemia) seizures are not epilepsy. “You must put something in the mouth to stop a seizure.” – This is dangerous; never force the mouth open. “If a patient is seizure‑free for 1 year, epilepsy is resolved.” – Resolution requires ≥10 years seizure‑free and ≥5 years off meds. “Valproate is safe in pregnancy.” – It has the highest teratogenic risk; avoid if possible. “All patients need routine drug‑level monitoring.” – Not necessary when seizures are controlled and no toxicity concerns. --- 🧠 Mental Models / Intuition “Excitation‑Inhibition Scale” – Visualize the brain as a seesaw; epilepsy tips the balance toward excitation. Anything that lowers the seizure threshold (sleep loss, stress) pushes the seesaw down. “Seizure spread as a fire” – Focal seizures are a spark; if the fire jumps across the corpus callosum it becomes generalized (focal‑to‑bilateral). “Epilepsy as a “broken circuit” – Structural lesions are “short‑circuits” that bypass normal inhibition, creating a loop of runaway firing. --- 🚩 Exceptions & Edge Cases Reflex epilepsy (≈ 6 %): seizures reliably provoked by specific stimuli (flashing lights, reading). Standard classification may list as “unknown onset” if not recognized. Autoimmune encephalitis – May present with seizures but requires antibody testing; conventional antiseizure meds often insufficient alone. Drug‑induced hormonal contraception failure – Enzyme‑inducing ASMs (e.g., carbamazepine) raise contraceptive failure to 3‑6 %; lamotrigine levels can drop, reducing seizure control. --- 📍 When to Use Which Choose medication based on seizure type Focal: start with levetiracetam (good tolerability) → consider carbamazepine/oxcarbazepine if cost is key. Generalized tonic‑clonic: valproate (unless pregnancy risk) → lamotrigine or levetiracetam as alternatives. Absence: ethosuximide first → valproate if mixed seizure types. Surgery vs. Diet Drug‑resistant focal epilepsy with a clear MRI lesion: prioritize surgery. Drug‑resistant generalized or multifocal epilepsy, especially in children: consider ketogenic diet or neurostimulation. Pregnancy planning Switch to lamotrigine or levetiracetam before conception; supplement folic acid 4 mg daily. --- 👀 Patterns to Recognize Jacksonian march → focal seizure spreading sequentially → think cortical motor area involvement. Auras preceding a seizure → indicate focal onset; ask patient about sensory or psychic phenomena. Sudden loss of tone (atonic) → high risk of falls & injury; often part of generalized epilepsy syndromes. Post‑ictal Todd’s paralysis – focal weakness that resolves within 24 h; clues to seizure focus (contralateral hemisphere). Clusters – multiple seizures <24 h with incomplete recovery → may need rescue medication plan. --- 🗂️ Exam Traps “Any seizure after a head injury is epilepsy.” – Acute symptomatic seizures are not epilepsy unless they become unprovoked. “Valproate is safe for all women of child‑bearing age.” – High teratogenicity; contraindicated when safer alternatives exist. “All focal seizures impair consciousness.” – Focal aware (preserved consciousness) seizures exist; don’t assume impairment. “EEG alone confirms epilepsy.” – Diagnosis requires clinical seizure description plus EEG; a normal EEG does not rule out epilepsy. “If a patient has a single seizure, give antiseizure medication immediately.” – Treatment is usually deferred unless high recurrence risk or specific syndrome. ---