Status Epilepticus (≥ 5 min)
0–5m: ABCs + Fingerstick Glucose (+ Thiamine before Dextrose) → 5–20m: IV Lorazepam → 20–40m: Levetiracetam / Fosphenytoin / Valproate → >40m: Propofol / Midazolam + Intubation
Absence vs. Juvenile Myoclonic
Absence = 3-Hz Spike-and-Wave, No Postictal Confusion → Rx: Ethosuximide (blocks Thalamic T-type Ca2+ channels). JME = Morning Myoclonic Jerks + GTC → Rx: Valproate / Levetiracetam
Antiepileptic Teratogenicity
Valproate (#1 Most Teratogenic) & Carbamazepine = Neural Tube Defects; Phenytoin = Fetal Hydantoin (Cleft Palate); Lamotrigine & Levetiracetam = SAFEST in Pregnancy!
AED Signature Toxicities
Lamotrigine & Carbamazepine (HLA-B*1502) = Stevens-Johnson/TEN; Carbamazepine = SIADH + Aplastic Anemia; Topiramate = Kidney Stones + Acute Angle-Closure Glaucoma
Myasthenia Gravis vs. LEMS
MG = Postsynaptic Anti-AChR/MuSK + Thymoma + Worsens with Use + Preserved Reflexes. LEMS = Presynaptic Anti-P/Q VGCC + Small Cell Lung Cancer + Improves with Use + Hyporeflexia
Guillain-Barré Syndrome (AIDP)
Campylobacter jejuni → Ascending Paralysis + AREFLEXIA + CSF Albuminocytologic Dissociation (High Protein, Normal WBCs) → Rx: IVIG or Plasmapheresis (NEVER Steroids!)
Acute Ischemic Stroke Windows
Non-Contrast Head CT FIRST! → IV Alteplase / Tenecteplase (≤ 4.5 hours, BP < 185/110) → Mechanical Thrombectomy (≤ 24 hours for Large Vessel Occlusion)
Subarachnoid Hemorrhage (SAH)
Thunderclap Headache → Non-Contrast Head CT (≤6h) → LP for Xanthochromia → Nimodipine (Oral for 21 Days to Prevent Vasospasm / Delayed Cerebral Ischemia!)
Stepwise Status Epilepticus Emergency Resuscitation Protocol
Status epilepticus leads to permanent neuronal injury and systemic acidosis if seizure duration exceeds 30 minutes. The resuscitation protocol is structured into time-critical phases:
0–5 Minutes: Stabilization Phase
Airway, breathing, circulation. Check bedside capillary fingerstick blood glucose immediately. Administer IV dextrose + thiamine if hypoglycemic. Obtain IV access.
5–20 Minutes: First-Line Therapy (Benzodiazepines)
IV Lorazepam (Ativan): 4 mg IV over 2 min (repeat once at 5-10 min). If IV access unavailable: IM Midazolam 10 mg (or rectal diazepam).
20–40 Minutes: Second-Line Therapy (Urgent Control)
Administer non-sedating IV antiepileptic: IV Levetiracetam (Keppra) 60 mg/kg (max 4500 mg), IV Fosphenytoin 20 mg PE/kg, or IV Valproate sodium 40 mg/kg.
40+ Minutes: Refractory Status Epilepticus
Endotracheal intubation and continuous general anesthetic infusion: Propofol, Midazolam, or Ketamine with continuous bedside EEG monitoring for burst suppression.
| Resuscitation Phase | Target Time Window | First-Line Pharmacotherapy & Dosing | Mechanism & Refractory Escalation |
|---|---|---|---|
| Phase 1: Stabilization & Glucose Check | 0 to 5 Minutes | ABC stabilization, lateral decubitus positioning, supplemental O2, fingerstick blood glucose (if <60 mg/dL: give IV Thiamine 100 mg BEFORE D50W) | Prevents aspiration, hypoxia, and precipitates of Wernicke encephalopathy in malnourished/alcoholic patients |
| Phase 2: First-Line Benzodiazepine | 5 to 10 Minutes | IV Lorazepam (0.1 mg/kg, max 4 mg/dose, repeat x1) OR IM Midazolam (10 mg IM if no IV access) OR IV Diazepam | Positive allosteric modulator of GABA-A chloride channels (increases frequency of channel opening); underdosing benzodiazepines is the #1 cause of progression to refractory status |
| Phase 3: Second-Line Antiseizure Loading | 10 to 20 Minutes | IV Fosphenytoin (20 mg PE/kg), IV Valproate (40 mg/kg), OR IV Levetiracetam (60 mg/kg, max 4500 mg) | ESETT trial demonstrated equal ~50% efficacy among fosphenytoin, valproate, and levetiracetam; fosphenytoin requires cardiac telemetry due to hypotension/arrhythmias from propylene glycol/phenytoin |
| Phase 4: Refractory Status Epilepticus | 20 to 60+ Minutes | Endotracheal Intubation + Continuous EEG monitoring + IV Anesthetic Infusion (Midazolam, Propofol, or Pentobarbital) | Continuous EEG is mandatory once paralyzed/sedated to detect non-convulsive status epilepticus (NCSE) |
The 5-Minute Definition of Status Epilepticus & First-Line Benzodiazepine Receptor Allosteric Modulation
Convulsive Status Epilepticus (SE) is defined operationally by the International League Against Epilepsy (ILAE) as a generalized tonic-clonic seizure lasting ≥5 minutes OR ≥2 discrete seizures between which the patient fails to recover baseline consciousness. The 5-minute threshold reflects critical synaptic receptor trafficking: after 5 minutes of continuous ictal firing, inhibitory postsynaptic GABAA receptors are internalized via clathrin-mediated endocytosis while excitatory NMDA and AMPA glutamate receptors are mobilized to the synaptic membrane—causing progressive benzodiazepine resistance, excitotoxic neuronal necrosis, rhabdomyolysis, hyperthermia, and lactic acidosis. In the initial 0-to-5-minute stabilization phase, secure the airway (lateral decubitus positioning, supplemental O2, never place objects in the mouth), check a stat fingerstick blood glucose (infuse IV Thiamine 100 mg before D50W if hypoglycemic), and establish IV access. At Minute 5 (Phase 1), administer a full-dose First-Line Benzodiazepine (positive allosteric modulator that increases the frequency of GABAA chloride channel opening): IV Lorazepam (0.1 mg/kg, max 4 mg/dose, may repeat once) is preferred if IV access is present due to its smaller volume of distribution and longer CNS duration of action (~12 hours) than diazepam; if IV access is absent, give IM Midazolam (10 mg IM) or rectal Diazepam.
Second-Line Antiseizure Loading (Fosphenytoin vs. Levetiracetam vs. Valproate) & Refractory SE Coma Induction
If seizure activity persists at 10 to 20 minutes (Phase 2) despite two benzodiazepine doses (or immediately after a single benzodiazepine breaks the acute convulsion, to prevent recurrence), load a Second-Line Intravenous Antiseizure Medication (demonstrated by the ESETT trial to have equivalent ~47% efficacy across the three major agents): (1) Fosphenytoin (20 mg PE/kg IV) (water-soluble prodrug of phenytoin that blocks voltage-gated Na+ channels; preferred over IV phenytoin because phenytoin is dissolved in propylene glycol/ethanol, which causes hypotension, arrhythmias, and necrotic 'Purple Glove Syndrome' upon extravasation); (2) Levetiracetam (60 mg/kg IV, max 4,500 mg) (binds synaptic vesicle protein SV2A; fewest drug-drug interactions, ideal in hepatic disease or pregnancy); or (3) Valproic Acid (40 mg/kg IV) (blocks Na+ channels and increases GABA; contraindicated in pregnancy [neural tube defects] and severe liver disease/urea cycle defects). If seizures continue beyond 30 to 40 minutes (Refractory Status Epilepticus, Phase 3), perform endotracheal intubation (avoid long-acting paralytics that mask ongoing electrical seizures!), attach continuous EEG monitoring to detect non-convulsive status epilepticus, and initiate a continuous anesthetic infusion of Midazolam, Propofol, or Pentobarbital (which directly opens GABAA channels by increasing duration of opening).
Neuromuscular Junction Disorders: Myasthenia Gravis vs. Lambert-Eaton
Neuromuscular junction (NMJ) transmission disorders are divided anatomically into postsynaptic receptor destruction (Myasthenia Gravis) and presynaptic calcium channel blockade (Lambert-Eaton Myasthenic Syndrome and Botulism). Distinguishing postsynaptic fatigable weakness from presynaptic facilitation with repetitive contraction requires correlating diurnal symptom progression, extraocular vs. proximal limb predominance, autonomic preservation, and underlying paraneoplastic associations (thymoma vs. small cell lung carcinoma).
| Feature | Myasthenia Gravis (MG) | Lambert-Eaton Myasthenic Syndrome (LEMS) |
|---|---|---|
| Target Antigen | Post-synaptic Nicotinic Acetylcholine Receptors (AChR) or MuSK | Pre-synaptic Voltage-Gated P/Q-type Calcium Channels (VGCC) |
| Effect of Repetitive Use | Muscle weakness worsens with use (fatigability) | Muscle strength improves with exercise (facilitation) |
| Ocular Involvement | Ptosis and diplopia common initial presentation (> 50%) | Ocular involvement rare; proximal limb weakness dominates |
| Autonomic Symptoms | Absent | Present: Dry mouth, erectile dysfunction, constipation |
| Deep Tendon Reflexes | Normal | Decreased or absent (may return after brief exercise) |
| Underlying Neoplasm | Thymoma (15%) or thymic hyperplasia (65%); chest CT mandatory | Small Cell Lung Carcinoma (SCLC) (> 50%) |
Synaptic Physiology: Why Repetitive Nerve Stimulation Depletes MG but Facilitates LEMS
In a normal neuromuscular junction, a single presynaptic action potential opens presynaptic P/Q-type voltage-gated calcium channels (VGCCs), triggering exocytosis of ~60–100 vesicles of acetylcholine (ACh) that bind abundant postsynaptic nicotinic ACh receptors (nAChRs) with a large 'safety factor.' In Myasthenia Gravis (MG) (Type II hypersensitivity: autoantibodies against postsynaptic nicotinic AChRs [85%] or Muscle-Specific Kinase [MuSK, 10%]), complement-mediated destruction flattens the postsynaptic motor endplate folds. With repetitive nerve stimulation (2–3 Hz) or sustained exertion across the day, normal physiological rundown of presynaptic ACh release rapidly drops endplate potentials below threshold—producing fatigable muscle weakness that worsens in the evening, presenting first in high-firing motor units as asymmetric ptosis and diplopia (improving with the bedside 2-minute Ice Pack Test, which inhibits acetylcholinesterase), bulbar dysarthria/dysphagia, and intact deep tendon reflexes. Conversely, in Lambert-Eaton Myasthenic Syndrome (LEMS), paraneoplastic autoantibodies (50%–60% from Small Cell Lung Carcinoma) block presynaptic P/Q-type VGCCs, preventing baseline ACh release. However, high-frequency repetitive stimulation (20–50 Hz) or 10 seconds of maximal isometric exercise floods the presynaptic terminal with residual Ca2+, overcoming the blockade and improving muscle strength and restoring absent patellar reflexes!
Myasthenic Crisis vs. Cholinergic Crisis, Contraindicated Medications & Thymectomy Indications
Because Lambert-Eaton Syndrome blocks presynaptic VGCCs at both somatic motor endplates and cholinergic autonomic ganglia, LEMS patients exhibit prominent autonomic dysfunction (dry mouth [xerostomia], erectile dysfunction, orthostatic hypotension, sluggish pupils), proximal lower-extremity hip-girdle weakness, and hyporeflexia (treated by treating the underlying SCLC and administering Amifostine / 3,4-Diaminopyridine [3,4-DAP], a presynaptic K+ channel blocker that prolongs action potential depolarization to increase Ca2+ influx). In Myasthenia Gravis, pupils, autonomic function, and reflexes are completely normal; every newly diagnosed MG patient requires a Contrast Chest CT to evaluate for thymic hyperplasia (65%) or Thymoma (10%–15%), with thymectomy indicated for all thymomas and generalized AChR+ MG under age 65. Outpatient MG is managed with Pyridostigmine (reversible acetylcholinesterase inhibitor) plus corticosteroids/azathioprine/mycophenolate. If an MG patient develops acute respiratory failure (Forced Vital Capacity [FVC] <15–20 mL/kg or Negative Inspiratory Force [NIF] worse than -20 to -30 cmH2O), intubate immediately, HOLD pyridostigmine (which increases airway secretions and could worsen a cholinergic crisis of SLUDGE/fasciculations), and initiate Plasmapheresis or IVIG. Never give MG patients aminoglycosides, fluoroquinolones, macrolides, magnesium sulfate, beta-blockers, or succinylcholine!
Seizure Classification, EEG Signatures & Pediatric Epilepsy Syndromes
A seizure is a paroxysmal, transient clinical event caused by abnormal, excessive, hypersynchronous electrical neuronal discharge within the cerebral cortex, whereas epilepsy is defined by at least 2 unprovoked seizures occurring > 24 hours apart (or 1 unprovoked seizure with a ≥ 60% recurrence risk on EEG/MRI). Every seizure is classified by its anatomical site of onset and level of consciousness: (1) Focal (Partial) Onset Seizures originate within networks limited to one cerebral hemisphere—subdivided into Focal Aware (formerly simple partial: consciousness remains completely intact; e.g., focal motor Jacksonian march along the motor homunculus, somatosensory paresthesias, or visual flashes) and Focal Impaired Awareness (formerly complex partial: impaired consciousness, most commonly originating in the Medial Temporal Lobe / Hippocampal Sclerosis, heralded by a visceral rising epigastric aura, olfactory hallucination of burning rubber, or déjà vu followed by blank staring and repetitive oroalimentary automatisms [lip smacking, chewing, picking at clothes] and postictal confusion); and (2) Generalized Onset Seizures rapidly engage bilateral cerebral hemispheres simultaneously from onset, always impairing consciousness (except isolated myoclonic jerks).
| Generalized / Pediatric Syndrome | Age of Onset & Triggers | Clinical Seizure Semiologies & Postictal State | Pathognomonic EEG Pattern | First-Line Treatment & Contraindicated Drugs |
|---|---|---|---|---|
| Childhood Absence Epilepsy (Petit Mal) | Children 4–10 years old; reliably provoked at bedside by hyperventilation for 2–3 minutes or photic stimulation | Brief (5–20 seconds) abrupt behavioral arrest and blank staring (± subtle eyelid fluttering), occurring dozens of times per day ('daydreaming' in school); NO aura and ZERO postictal confusion (resumes speaking mid-sentence!) | Generalized symmetric 3-Hz Spike-and-Slow-Wave discharges (normal interictal background) | 1st Line: Ethosuximide (blocks Thalamic T-type Ca2+ channels). If concurrent GTC seizures: Valproic Acid or Lamotrigine. AVOID Carbamazepine & Phenytoin! |
| Juvenile Myoclonic Epilepsy (JME / Janz Syndrome) | Adolescents 12–18 years old; triggered by sleep deprivation, early morning awakening, alcohol intake, and strobe lights | Classic triad: 1. Myoclonic jerks within 1 hour of waking up in the morning (dropping toothbrush/coffee cup/cereal bowl with intact consciousness!) + 2. Generalized Tonic-Clonic seizures + 3. Absence seizures | Generalized 4–6 Hz Polyspike-and-Slow-Wave discharges | 1st Line (Males): Valproic Acid. 1st Line (Females of childbearing age): Levetiracetam or Lamotrigine (lifelong therapy required!). AVOID Carbamazepine & Phenytoin! |
| Infantile Spasms (West Syndrome) | Infants 3–12 months old; strongly associated with Tuberous Sclerosis (TSC1/TSC2 hamartin/tuberin, ash-leaf spots, cardiac rhabdomyoma) or perinatal hypoxic brain injury | Clusters of sudden symmetric jackknife flexion or extension spasms ('salaam attacks') of the neck, trunk, and extremities upon waking + developmental regression | HYPSARRHYTHMIA (chaotic, high-voltage, asynchronous multifocal spikes and slow waves) | 1st Line (Overall): Intramuscular ACTH (Corticotropin) or high-dose Prednisolone. 1st Line if Tuberous Sclerosis: Vigabatrin (irreversible GABA transaminase inhibitor; causes permanent concentric visual field constriction!) |
| Lennox-Gastaut Syndrome | Early childhood (1–7 years old); often evolves from Infantile Spasms (West syndrome) | Classic triad: 1. Multiple refractory seizure types (especially Atonic 'Drop Attacks' causing facial/head trauma + Tonic seizures) + 2. Severe Intellectual Disability + 3. Slow Spike-and-Wave EEG | Slow (< 2.5 Hz) Generalized Spike-and-Wave discharges | Valproate, Lamotrigine, Rufinamide, Topiramate, Clobazam, Felbamate (causes aplastic anemia/hepatotoxicity), or Cannabidiol |
| Benign Rolandic Epilepsy (BECTS) | Children 6–10 years old; occurs characteristically at night during sleep | Nocturnal focal motor seizure involving unilateral facial twitching, tongue/cheek paresthesias, hypersalivation/drooling, and speech arrest (anarthria) with preserved consciousness | Centrotemporal spikes (over the Rolandic fissure) | Spontaneously resolves by puberty (age 15–16)! Often requires no medication (or low-dose Levetiracetam/Carbamazepine if frequent) |
| Simple vs. Complex Febrile Seizures | Children 6 months to 5 years old with fever ≥ 38.0°C (HHV-6 Roseola infantum is the #1 viral trigger!) and NO CNS infection | Simple (80%): Generalized tonic-clonic, lasts < 15 minutes, and does NOT recur within 24 hours. Complex (20%): Focal features, lasts ≥ 15 minutes, OR recurs (≥ 2 episodes) within 24 hours | Normal EEG (EEG and MRI are NOT indicated for a simple febrile seizure!) | Simple: Reassurance + Antipyretics (Acetaminophen/Ibuprofen) (NO daily antiepileptic prophylaxis!). Perform LP only if meningeal signs or unvaccinated infant < 12 mos |
Differentiating Absence Seizures vs. Focal Impaired Awareness (Complex Partial) Seizures
One of the highest-yield neurology vignette comparisons is distinguishing a child or adult who 'stares blankly into space': Absence Seizures occur in children (4–10 yrs), last < 20 seconds, occur 10–100 times per day, are provoked by hyperventilation, have NO preceding aura and ZERO postictal confusion, show a generalized 3-Hz spike-and-wave EEG, and are treated with Ethosuximide. In contrast, Focal Impaired Awareness (Temporal Lobe) Seizures occur at any age, last 1 to 3 minutes, occur infrequently (weekly/monthly), are preceded by an epigastric/olfactory/déjà vu aura, feature prominent automatisms (lip smacking, hand fumbling), are followed by 10–30 minutes of postictal confusion and fatigue, show unilateral temporal lobe spikes on EEG, and are treated with Levetiracetam, Lamotrigine, or Carbamazepine/Oxcarbazepine!
Postictal Todd Paralysis & Convulsive Syncope vs. Generalized Tonic-Clonic Seizure
Following a focal motor seizure or generalized tonic-clonic seizure, patients may exhibit transient unilateral hemiparesis, gaze palsy, or aphasia (Todd Paralysis) caused by temporary metabolic exhaustion and postictal neuronal inhibition in the epileptogenic motor cortex; Todd paralysis spontaneously and completely resolves within 1 to 36 hours. When evaluating a patient who collapsed with brief limb jerking, how do you distinguish Generalized Tonic-Clonic Seizure from Convulsive Syncope (vasovagal or cardiogenic)? A true GTC seizure features lateral tongue biting (highly specific!), urinary incontinence, cyanosis, a prolonged postictal confusional state (> 15–30 minutes), and an elevated anion-gap lactic acidosis with elevated serum creatine kinase (CK) and prolactin, whereas syncope features a brief prodrome (lightheadedness, diaphoresis, tunnel vision) and immediate return to baseline alertness within seconds of lying flat.
Etiologies of New-Onset First Seizure in Adults by Age & Metabolic Reversibility
When an adult with no history of epilepsy presents with a first-time generalized tonic-clonic seizure, the immediate priority is ruling out reversible metabolic, toxic, and infectious causes before diagnosing epilepsy: check a bedside fingerstick glucose (hypoglycemia), serum sodium (acute severe hyponatremia < 120 mEq/L), serum calcium/magnesium (hypocalcemia/hypomagnesemia), pregnancy test (eclampsia!), urine toxicology (cocaine, amphetamines, tramadol, bupropion, TCA overdose, or alcohol/benzodiazepine withdrawal), and non-contrast Head CT / brain MRI. By age group, the #1 structural cause of new-onset adult focal epilepsy in young/middle-aged adults (18–60 yrs) is brain tumors (glioblastoma, meningioma, brain metastases), traumatic brain injury, or arteriovenous malformations (AVMs), whereas the #1 cause of new-onset epilepsy in older adults (> 60 years old) is prior cerebrovascular disease (ischemic/hemorrhagic stroke scar!).
Antiepileptic Drug (AED) Pharmacology, Ion Channel Targets & Teratogenicity Master Matrix
Antiepileptic drugs suppress cortical hyperexcitability through three primary neurochemical mechanisms: (1) Blocking voltage-gated Na+ channels (prolonging the inactivated state to prevent high-frequency repetitive action potential firing); (2) Blocking voltage-gated Ca2+ channels or SV2A synaptic vesicle proteins (inhibiting presynaptic excitatory glutamate release or thalamic pacemaker currents); and (3) Enhancing inhibitory GABAA transmission (via Cl- channel frequency/duration or inhibiting GABA transaminase/reuptake).
| Antiepileptic Drug | Molecular Mechanism of Action | Clinical Spectrum of Efficacy | CYP450 Profile & Signature Board Toxicities |
|---|---|---|---|
| Levetiracetam (Keppra) | Binds presynaptic SV2A (Synaptic Vesicle Glycoprotein 2A), modulating neurotransmitter exocytosis | Broad-spectrum (#1 first-line for Focal, Generalized Tonic-Clonic, JME, and second-line Status Epilepticus; SAFE in pregnancy!) | ZERO hepatic CYP450 interactions (renally excreted — ideal for patients on chemotherapy, anticoagulants, or OCPs!). Key Toxicity: Neuropsychiatric irritability, agitation, aggression, and depression ('Keppra rage' — mitigated by Vitamin B6) |
| Lamotrigine (Lamictal) | Blocks voltage-gated Na+ channels and inhibits presynaptic glutamate release | Broad-spectrum (Focal, GTC, Absence, Lennox-Gastaut, and Bipolar Depression maintenance; SAFEST in pregnancy!) | Metabolized by glucuronidation (Valproate inhibits Lamotrigine clearance → doubles levels!). Key Toxicity: Stevens-Johnson Syndrome (SJS) / Toxic Epidermal Necrolysis (TEN) — requires very slow dose titration! |
| Valproic Acid (Valproate) | 1. Blocks voltage-gated Na+ channels. 2. Blocks T-type Ca2+ channels. 3. Inhibits GABA Transaminase (increases brain GABA) | Broadest-spectrum AED (GTC, Myoclonic [JME], Absence, Focal, Bipolar mania, Migraine prophylaxis) | Potent CYP450 INHIBITOR. Key Toxicities: #1 MOST TERATOGENIC AED (Neural Tube Defects / Spina Bifida — inhibits folate & histone deacetylase!), Fulminant Hepatotoxicity & Hyperammonemic Encephalopathy (treat with L-Carnitine), Acute Pancreatitis, thrombocytopenia, weight gain, tremor, alopecia |
| Carbamazepine & Oxcarbazepine | Blocks voltage-gated Na+ channels (stabilizes inactive state) | Narrow-spectrum: Focal seizures ONLY (& #1 first-line for Trigeminal Neuralgia [Tic Douloureux]!). Worsens Absence & Myoclonic seizures! | Potent CYP450 INDUCER (also induces its own metabolism — autoinduction!). Key Toxicities: SIADH (euvolemic hyponatremia!), Agranulocytosis / Aplastic Anemia (check CBC!), SJS/TEN (screen Asians for HLA-B*15:02!), diplopia/ataxia, neural tube defects |
| Phenytoin & Fosphenytoin | Blocks voltage-gated Na+ channels; exhibits Zero-Order Elimination Kinetics at therapeutic doses | Focal & Generalized Tonic-Clonic seizures; Status Epilepticus (IV Fosphenytoin) | Potent CYP450 INDUCER. Key Toxicities: Gingival Hyperplasia (via PDGF), Cerebellar Ataxia, Nystagmus, Diplopia, hirsutism, coarsened facial features, Osteopenia/Osteomalacia (catabolizes Vitamin D), Megaloblastic Anemia (folate), drug-induced lupus, SJS, and Fetal Hydantoin Syndrome (cleft lip/palate, nail hypoplasia, microcephaly). Rapid IV Phenytoin (propylene glycol) causes hypotension & arrhythmias! |
| Ethosuximide | Blocks low-threshold T-type Ca2+ channels in Thalamic relay neurons | Childhood Absence Seizures ONLY (has zero efficacy against tonic-clonic or focal seizures!) | Mnemonic EFGHIJ: Ethosuximide causes Fatigue, GI distress (nausea/vomiting/pain), Headache, Itching/urticaria, and Johnson (Stevens-Johnson syndrome) |
| Topiramate | Blocks Na+ channels, enhances GABAA, antagonizes AMPA/kainate glutamate, and weakly inhibits Carbonic Anhydrase | Focal & GTC seizures, Lennox-Gastaut, and #1 Migraine Prophylaxis | Key Toxicities ('Dopamax'): Cognitive slowing / word-finding difficulty, Weight LOSS, paresthesias, Calcium Phosphate Kidney Stones (via proximal RTA / hypocitraturia!), and Acute Bilateral Secondary Angle-Closure Glaucoma / Myopia (ciliary body edema!) |
Interactive 2K Master Atlas Plate
Zero-Order Elimination Kinetics & Free Phenytoin Levels in Hypoalbuminemia
Phenytoin is one of the three classic drugs (Phenytoin, Ethanol, and high-dose Aspirin) that exhibit capacity-limited (Zero-Order) elimination kinetics once hepatic CYP2C9 enzymes become saturated: small dose increases cause an exponential spike in plasma concentration, precipitating acute cerebellar toxicity (horizontal nystagmus → ataxia/dysarthria → lethargy). Furthermore, because phenytoin is 90% bound to serum albumin and only the 10% unbound (free) fraction crosses the blood-brain barrier, patients with severe hypoalbuminemia (cirrhosis, nephrotic syndrome, malnutrition) or uremia (ESRD) can develop severe phenytoin neurotoxicity even when the reported 'total serum phenytoin level' appears normal—always check a Free Phenytoin level or apply the Sheiner-Tozer albumin correction!
Enzyme-Inducing AEDs & Oral Contraceptive Failure
Potent hepatic CYP450 inducers (Carbamazepine, Phenytoin, Phenobarbital, Primidone, and high-dose Topiramate) accelerate the hepatic metabolism of ethinyl estradiol and progestins, causing breakthrough ovulation and unplanned pregnancy in women taking combined Oral Contraceptive Pills (OCPs)! In reproductive-age women with epilepsy, either prescribe non-inducing Levetiracetam or Lamotrigine, or recommend a Copper or Levonorgestrel Intrauterine Device (IUD) whose local efficacy is unaffected by hepatic CYP450 induction.
GABAergic & Gabapentinoid Pharmacology: Benzodiazepines vs. Barbiturates vs. Gabapentin
Three supplementary drug classes are tested in seizure and neuropathic pain vignettes: (1) Benzodiazepines (Lorazepam, Diazepam, Midazolam, Clonazepam) bind the allosteric BZ site between the α and γ subunits of the GABAA Cl- channel to increase the FREQUENCY of Cl- channel opening (only in the presence of endogenous GABA; antidote = Flumazenil, though flumazenil is contraindicated in chronic benzodiazepine users or TCA co-ingestion because it precipitates refractory seizures!); (2) Barbiturates (Phenobarbital, Pentobarbital, Thiopental) bind the barbiturate site on the GABAA receptor to increase the DURATION of Cl- channel opening (and can directly open the channel at high doses, causing lethal medullary respiratory depression; Phenobarbital is the #1 first-line AED for Neonatal Seizures!); and (3) Gabapentin and Pregabalin: despite being structural analogs of GABA, they DO NOT bind GABA receptors! Instead, they bind the α2δ-1 subunit of presynaptic voltage-gated Ca2+ channels to inhibit excitatory neurotransmitter release (first-line for diabetic neuropathy, postherpetic neuralgia, and fibromyalgia; causes peripheral pedal edema and sedation/ataxia in renal failure).
Neuromuscular Junction & Motor Neuron Disorders: Myasthenia Gravis, LEMS, Botulism, GBS & ALS
When a patient presents with acute or subacute generalized weakness without cortical upper motor neuron findings (or with combined UMN + LMN findings), localizing the lesion along the motor unit—Anterior Horn Cell (ALS, Polio, SMA) → Peripheral Nerve Myelin (Guillain-Barré Syndrome) → Presynaptic NMJ (Lambert-Eaton, Botulism) → Postsynaptic NMJ (Myasthenia Gravis)—is tested on every clinical board examination:
| Disorder | Anatomical Site & Molecular Mechanism | Hallmark Clinical Presentation & Reflexes | Confirmatory Diagnostics & First-Line Treatment |
|---|---|---|---|
| Myasthenia Gravis (MG) | Postsynaptic NMJ (Type II hypersensitivity): IgG autoantibodies against Postsynaptic Nicotinic ACh Receptors (85% — associated with Thymic Hyperplasia or THYMOMA!) or MuSK (Muscle-Specific Kinase, 10%) | Bimodal (young women 20–30s; older men 60–70s). FATIGABLE weakness that WORSENS with repetitive use and at the end of the day: asymmetric Ptosis & Diplopia (#1 initial symptom!), bulbar dysarthria/dysphagia, proximal limb weakness. Pupils, Sensation, and Deep Tendon Reflexes are completely NORMAL! | Bedside Ice Pack Test (cooling inhibits AChE → improves ptosis in 2 min!); Anti-AChR / Anti-MuSK antibodies; Decrement on repetitive nerve stimulation; CT Chest to rule out Thymoma! Symptomatic Rx: Pyridostigmine + Prednisone/Azathioprine + Thymectomy. Myasthenic Crisis: Intubate + Plasmapheresis or IVIG |
| Lambert-Eaton Myasthenic Syndrome (LEMS) | Presynaptic NMJ (Paraneoplastic): IgG autoantibodies against Presynaptic P/Q-type Voltage-Gated Calcium Channels (VGCC) → prevents Ca2+-dependent ACh vesicle exocytosis | > 60% associated with Small Cell Lung Cancer (SCLC)! Presents with Symmetric PROXIMAL lower extremity weakness (difficulty rising from a chair) that IMPROVES with repetitive muscle contraction + Autonomic dysfunction (dry mouth, impotence, sluggish pupils) + HYPOREFLEXIA/AREFLEXIA (reflexes return after 10 sec of exercise!) | Anti-P/Q VGCC antibodies + Incremental response on high-frequency repetitive nerve stimulation + CT Chest for Small Cell Lung Cancer! Rx: Amifostine / 3,4-Diaminopyridine (Amifampridine — blocks K+ channels to prolong presynaptic depolarization!) + treat SCLC |
| Botulism (Clostridium botulinum) | Presynaptic NMJ: Botulinum neurotoxin (protease) enters presynaptic terminal and cleaves SNARE proteins (Synaptobrevin, SNAP-25, Syntaxin), blocking ACh release | Infants (< 1 yr): ingestion of raw HONEY or soil spores → constipation (1st sign!) → 'Floppy Baby Syndrome'. Adults: ingestion of preformed toxin in improperly home-canned vegetables/fish or black-tar heroin wounds. Presents with DESCENDING symmetric flaccid paralysis: 4 Ds (Diplopia, Dysarthria, Dysphagia, Dyspnea) + DILATED poorly reactive pupils (Mydriasis) + Dry mouth! | Stool/serum toxin assay. Adults: Equine Heptavalent Botulinum Antitoxin. Infants: Human Botulism Immune Globulin (BIG-IV / BabyBIG) (do NOT give antibiotics in infant botulism—lysing gut bacteria releases more toxin!) |
| Guillain-Barré Syndrome (AIDP) | Peripheral Nerve Schwann Cell / Myelin: Molecular mimicry (anti-GM1 ganglioside antibodies) 1–3 weeks after Campylobacter jejuni (#1!), CMV, EBV, Zika, or Mycoplasma | Symmetric ASCENDING flaccid paralysis starting in feet/legs with distal paresthesias + AREFLEXIA (absent deep tendon reflexes!) + Bilateral CN VII facial palsy + Autonomic instability (labile BP, arrhythmias — #1 cause of death alongside respiratory failure!) | CSF: Albuminocytologic Dissociation (Elevated CSF Protein > 45–100 mg/dL with NORMAL WBC count < 5/μL!); slowed nerve conduction velocity. Rx: Monitor serial FVC & NIF + IVIG OR Plasmapheresis (NEVER Corticosteroids!) |
| Amyotrophic Lateral Sclerosis (ALS / Lou Gehrig Disease) | Upper AND Lower Motor Neurons: Degeneration of lateral corticospinal tracts (UMN) AND anterior horn cells / brainstem motor nuclei (LMN) (SOD1 or C9orf72 mutation in familial cases; glutamate excitotoxicity) | COMBINED UMN signs (spasticity, hyperreflexia, Babinski+, pseudobulbar affect) AND LMN signs (asymmetric muscle atrophy, FASCICULATIONS, tongue fasciculations/dysarthria). Sensation, Bowel/Bladder sphincter tone, and Extraocular eye movements (CN III/IV/VI) are SPARED! | Clinical/EMG diagnosis across multiple body regions. Rx: Riluzole (inhibits presynaptic glutamate release — prolongs survival by 3–6 mos), Edaravone (free radical scavenger), and Non-Invasive Positive Pressure Ventilation (BiPAP) |
Myasthenic Crisis vs. Cholinergic Crisis & Respiratory Mechanics Monitoring (FVC & NIF)
When a patient with Myasthenia Gravis develops acute worsening weakness and dyspnea, it is almost always a Myasthenic Crisis (triggered by respiratory infection, surgery, tapering steroids, or contraindicated drugs like fluoroquinolones/aminoglycosides/beta-blockers), though massive overdosage of Pyridostigmine can cause a Cholinergic Crisis (distinguished by DUMBBELSS muscarinic overload: Diarrhea, Urination, Miosis [pinpoint pupils!], Bronchospasm/Bronchorrhea, Bradycardia, Lacrimation, Salivation, plus muscle fasciculations). In either crisis, NEVER wait for arterial blood gas hypoxemia or hypercapnia to intubate—ABGs remain normal until the diaphragm completely fails! Instead, monitor bedside Forced Vital Capacity (FVC) and Negative Inspiratory Force (NIF / Maximal Inspiratory Pressure): perform elective endotracheal intubation if FVC falls < 15–20 mL/kg OR NIF becomes weaker than -20 to -30 cm H2O (the '20-30-40 rule'), temporarily discontinue Pyridostigmine once intubated (to prevent excessive airway secretions), and initiate Plasmapheresis or IVIG + High-Dose Corticosteroids.
Miller Fisher Variant of Guillain-Barre Syndrome (Anti-GQ1b Antibodies)
Whereas classic Guillain-Barré syndrome (AIDP) presents with ascending lower-extremity weakness and areflexia, the Miller Fisher Variant presents with a descending triad of 1. Ophthalmoplegia (external eye muscle paralysis / diplopia), 2. Ataxia, and 3. Areflexia without prominent limb weakness! It is strongly associated with Anti-GQ1b ganglioside IgG autoantibodies and is treated with IVIG or Plasmapheresis.
Multiple Sclerosis (MS): Oligoclonal Bands, Internuclear Ophthalmoplegia (MLF) & Disease-Modifying Rx
Always contrast peripheral Schwann cell demyelination (Guillain-Barré) with Multiple Sclerosis (MS)—autoimmune Type IV T-cell-mediated demyelination of CNS oligodendrocytes in young women (20–40 yrs, northern latitudes, HLA-DR2) presenting with neurologic deficits separated in both SPACE and TIME: (1) Optic Neuritis (painful monocular vision loss, central scotoma, and Marcus Gunn relative afferent pupillary defect [RAPD]); (2) Internuclear Ophthalmoplegia (INO) from demyelination of the Medial Longitudinal Fasciculus (MLF) (ipsilateral eye FAILS to ADDUCT on conjugate lateral gaze + contralateral abducting eye exhibits horizontal nystagmus, while CONVERGENCE remains intact!); (3) Lhermitte sign (electric shock shooting down the spine upon neck flexion), Uhthoff phenomenon (worsening of symptoms in hot showers/heat), and Charcot neurologic triad (scanning speech, intention tremor, nystagmus); and (4) UMN Neurogenic Bladder (detrusor hyperreflexia → urge incontinence). MRI shows periventricular white matter plaques ('Dawson fingers'), and CSF shows IgG Oligoclonal Bands. Treat acute flares with High-Dose IV Methylprednisolone (or plasmapheresis if refractory) and prevent relapses with Disease-Modifying Therapy (Ocrelizumab [anti-CD20], Natalizumab [screen for JC virus!], Fingolimod, Dimethyl fumarate, or Interferon-β/Glatiramer).
Cerebrovascular Emergencies: Acute Ischemic Stroke, Vascular Syndromes & Subarachnoid Hemorrhage
Stroke is the fifth leading cause of death and the number-one cause of permanent adult disability. 85% of strokes are Ischemic (thrombotic, embolic from atrial fibrillation or carotid stenosis, or lacunar lipohyalinosis from chronic hypertension), and 15% are Hemorrhagic (Intracerebral Hemorrhage or Subarachnoid Hemorrhage). When a patient arrives with acute focal neurologic deficits, the #1 immediate diagnostic step is always a Non-Contrast Head CT (plus a bedside fingerstick blood glucose, since hypoglycemia mimics focal stroke!) to exclude hemorrhage before administering thrombolytics.
| Vascular Territory / Syndrome | Neuroanatomical Structures Infarcted | Pathognomonic Clinical Presentation |
|---|---|---|
| Anterior Cerebral Artery (ACA) | Medial frontal and parietal lobes (leg/foot motor & sensory homunculus) + prefrontal cortex | Contralateral LOWER EXTREMITY > upper extremity weakness & sensory loss + Urinary incontinence + Abulia (apathy/personality change) and primitive grasp/suck reflexes |
| Middle Cerebral Artery (MCA) (#1 Most Common Embolic Stroke!) | Lateral frontal, parietal, and temporal cortex (face/arm homunculus) + language areas (Dominant Left) or spatial attention (Non-Dominant Right) | Contralateral FACE & ARM > leg weakness and sensory loss + Ipsilateral gaze preference (eyes look TOWARD the cortical lesion!) + Contralateral homonymous hemianopia. • Dominant (Left) MCA: Broca (Superior div) or Wernicke (Inferior div) Aphasia. • Non-Dominant (Right) MCA: Contralateral Hemispatial Neglect & anosognosia |
| Posterior Cerebral Artery (PCA) | Occipital lobe primary visual cortex (calcarine sulcus); collateral perfusion from MCA protects the macula | Contralateral Homonymous Hemianopia WITH Macular Sparing (+ alexia without agraphia if left PCA involves splenium of corpus callosum) |
| Lateral Medullary (Wallenberg) Syndrome (PICA — Posterior Inferior Cerebellar Artery / Vertebral Artery) | Spinothalamic tract, Spinal trigeminal nucleus (CN V), Nucleus ambiguus (CN IX, X), Vestibular nuclei, Inferior cerebellar peduncle, Descending sympathetics | NO motor paralysis (pyramids spared!). • Contralateral: loss of body pain & temperature. • Ipsilateral: loss of facial pain & temperature + Hoarseness, Dysphagia, Loss of Gag Reflex, Uvula deviates AWAY from lesion (Nucleus Ambiguus = unique to PICA!) + Horner Syndrome + Vertigo/Nystagmus/Ataxia + Intractable Hiccups |
| Lateral Pontine Syndrome (AICA — Anterior Inferior Cerebellar Artery) | Facial nucleus (CN VII), Vestibulocochlear nucleus/labyrinthine artery (CN VIII), Spinothalamic tract, Spinal CN V, Sympathetics | Same crossed pain/temp + Horner + ataxia as Wallenberg, EXCEPT replace Nucleus Ambiguus (dysphagia/hoarseness) with IPSILATERAL CN VII Facial Paralysis + IPSILATERAL CN VIII Sensorineural Deafness & Tinnitus! |
| Lacunar Strokes (Lenticulostriate / Thalamoperforating Arteries) | Small penetrating arteries damaged by Hyaline Arteriolosclerosis (Lipohyalinosis) from Chronic Hypertension & Diabetes | NO cortical signs (no aphasia, no neglect, no visual field cut!): 1. Posterior Limb of Internal Capsule: Pure Motor Hemiparesis (equal face, arm, leg). 2. VPL/VPM Thalamus: Pure Sensory Stroke (or Dejerine-Roussy thalamic pain syndrome) |
Intracerebral Hemorrhage (ICH) Etiology by Brain Location: Basal Ganglia vs. Lobar
When a Non-Contrast Head CT reveals a hyperdense parenchymal Intracerebral Hemorrhage (ICH), the anatomical location immediately identifies the underlying etiology: (1) Deep Hemorrhage in the Basal Ganglia (Putamen #1!), Thalamus, Pons (pinpoint reactive pupils + locked-in/coma), or Cerebellum is caused by Chronic Hypertension rupturing microaneurysms (Charcot-Bouchard microaneurysms) on small penetrating lenticulostriate arteries; whereas (2) Superficial Lobar Hemorrhage (frontal, parietal, occipital cortex) in an older adult (often with Alzheimer dementia) is caused by Cerebral Amyloid Angiopathy (CAA)—deposition of β-amyloid peptide (Aβ) in the walls of small/medium leptomeningeal and cortical arteries!
Traumatic Intracranial Hemorrhages: Epidural vs. Subdural vs. Subarachnoid
Mastering the three extra-axial intracranial hemorrhages on Non-Contrast Head CT is mandatory: (1) Epidural Hematoma: trauma fracturing the squamous temporal bone (pterion) lacerates the Middle Meningeal Artery (a branch of the maxillary artery passing through the foramen spinosum); presents with brief loss of consciousness followed by a 'Lucid Interval' and rapid uncal herniation (ipsilateral blown pupil [CN III] + contralateral hemiparesis); CT shows a hyperdense BICONVEX (LENS-SHAPED) hematoma that DOES NOT cross cranial suture lines; (2) Subdural Hematoma: acceleration-deceleration shearing of low-pressure Bridging Cortical Veins (draining into the superior sagittal sinus), classic in elderly patients, chronic alcoholics (brain atrophy stretches bridging veins!), anticoagulated patients, and shaken baby syndrome; CT shows a CRESCENT-SHAPED hematoma that CROSSES suture lines (but cannot cross dural reflections like the falx cerebri); and (3) Subarachnoid Hemorrhage (SAH): rupture of a Saccular (Berry) Aneurysm at Circle of Willis bifurcations (Anterior Communicating Artery #1; Posterior Communicating Artery #2 [CN III palsy!]); presents with a sudden 'Thunderclap' headache ('worst headache of my life') + meningismus; CT shows hyperdense blood filling the basal cisterns and cortical sulci, and oral Nimodipine (dihydropyridine Ca2+ channel blocker) MUST be given for 21 days to prevent cerebral arterial vasospasm / delayed cerebral ischemia!
Secondary Stroke Prevention & Carotid Endarterectomy (CEA) Stenosis Thresholds
After stabilizing an acute ischemic stroke or Transient Ischemic Attack (TIA), workup includes Transthoracic/Transesophageal Echocardiography, telemetry/Holter monitoring for occult Atrial Fibrillation, Carotid Duplex Ultrasound, fasting lipid panel, and HbA1c: (1) If Atrial Fibrillation is discovered, long-term Oral Anticoagulation (Apixaban, Rivaroxaban, Dabigatran, or Warfarin) is indicated rather than aspirin monotherapy; (2) If non-cardioembolic atherosclerosis is the cause, start Antiplatelet therapy (Aspirin, Clopidogrel, or dual antiplatelet therapy [DAPT] for 21–90 days in minor stroke/high-risk TIA) + High-Intensity Statin (Atorvastatin 80 mg or Rosuvastatin 20–40 mg) + BP control; and (3) When is Carotid Endarterectomy (CEA) indicated for internal carotid artery stenosis? Perform CEA within 2 weeks in SYMPTOMATIC patients (recent ipsilateral TIA, amaurosis fugax, or non-disabling stroke) with 70–99% carotid stenosis (and consider in symptomatic men with 50–69% stenosis). Never perform CEA for < 50% stenosis or for 100% complete chronic carotid occlusion (medical management only!).
COMLEX / OMM Integration
NBOME High-Yield Correlate
OMM in Seizures, Stroke Rehabilitation & Neuromuscular Respiratory Failure: Vagal Somatovisceral Reflexes, Cranial Venous Sinus Drainage & Contraindications
Osteopathic management across acute neurologic emergencies integrates autonomic neuroanatomy, respiratory biomechanics, and strict safety contraindications. First, in Refractory Epilepsy and Postictal States, afferent vagal stimulation via the nucleus tractus solitarius (NTS) desynchronizes epileptiform thalamocortical rhythms (the physiological basis of implanted Vagus Nerve Stimulators); osteopathically, somatic dysfunction at the occipitoatlantal (OA) and atlantoaxial (AA) joints and the jugular foramen (occipitomastoid suture) compresses or facilitates the vagus nerve (CN X). Gentle Suboccipital Inhibition and Cranial Venous Sinus Drainage reduce dural congestion and normalize parasympathetic vagal tone after a seizure has been pharmacologically terminated. Second, in Acute Stroke and Subarachnoid Hemorrhage, cervical High-Velocity Low-Amplitude (HVLA) thrusting is ABSOLUTELY CONTRAINDICATED due to the risk of vertebral or carotid artery dissection, plaque embolization, and elevating intracranial pressure (ICP); similarly, cranial manipulation and thoracic/lymphatic pumps are contraindicated during acute intracranial hemorrhage or elevated ICP. In the subacute/chronic post-stroke rehabilitation phase, Muscle Energy, Counterstrain, and Myofascial Release reduce upper motor neuron spasticity by resetting hyperactive gamma-motor neuron and Ia muscle spindle gain. Third, in Myasthenia Gravis or Guillain-Barré Syndrome, while mechanical ventilation/IVIG/plasmapheresis is definitive for respiratory crisis, gentle thoracic inlet myofascial release, doming of the respiratory diaphragm (T10–L3, phrenic nerve C3–C5), and rib raising optimize chest wall compliance during recovery.
Board Traps & Common Distractors
- Trap: Prescribing Carbamazepine, Oxcarbazepine, or Phenytoin to a child with Absence Seizures or an adolescent with Juvenile Myoclonic Epilepsy (JME). Narrow-spectrum voltage-gated sodium channel blockers (Carbamazepine and Phenytoin) paradoxically exacerbate and precipitate absence and myoclonic status epilepticus! Treat typical Absence Seizures with Ethosuximide and JME with Valproate or Levetiracetam (or Lamotrigine).
- Trap: Administering IV Corticosteroids (Methylprednisolone or Prednisone) to treat Guillain-Barré Syndrome (AIDP). Unlike MS, CIDP, or Myasthenia Gravis, corticosteroids have ZERO efficacy in Guillain-Barré Syndrome and can delay recovery! Treat Guillain-Barré exclusively with IVIG or Plasmapheresis (Plasma Exchange) (giving both offers no extra benefit over either alone).
- Trap: Administering Fluoroquinolones (Ciprofloxacin, Levofloxacin), Aminoglycosides (Gentamicin), Macrolides (Azithromycin), or Non-Selective Beta-Blockers to a patient with Myasthenia Gravis. These medications directly impair neuromuscular transmission and precipitate life-threatening Myasthenic Crisis (acute diaphragmatic respiratory failure)!
- Trap: Rapidly lowering blood pressure to normal (120/80 mmHg) in an acute ischemic stroke patient who is NOT receiving tPA and whose BP is 195/105 mmHg. The ischemic penumbra relies on collateral cerebral perfusion pressure; in patients NOT receiving tPA, practice permissive hypertension and only lower BP if > 220/120 mmHg (or if receiving tPA, lower carefully to < 185/110 mmHg before infusion and < 180/105 mmHg for 24h after)!
- Trap: Stopping the diagnostic workup for Subarachnoid Hemorrhage (SAH) after a Non-Contrast Head CT comes back negative in a patient who presented 14 hours after the onset of a sudden 'thunderclap' headache. While Non-Contrast Head CT is ~98–100% sensitive within the first 6 hours, sensitivity drops significantly after 6 hours as blood dilutes into CSF; you MUST perform a Lumbar Puncture to look for Xanthochromia (yellow bilirubin pigment from lysed RBCs)!
- Trap: Misdiagnosing Psychogenic Non-Epileptic Spells (PNES / Pseudoseizures) as refractory status epilepticus and intubating the patient. Clues to PNES include forceful resistance to eyelid opening (eyes tightly closed!), side-to-side head shaking, asynchronous pelvic thrusting, crying/vocalization during the convulsion, rapid return to baseline without postictal confusion, normal serum prolactin/lactate/CK, and a normal background alpha rhythm on Video-EEG (gold standard!).
- Trap: Giving Succinylcholine for rapid-sequence endotracheal intubation in a patient with Guillain-Barré Syndrome, Amyotrophic Lateral Sclerosis (ALS), Stroke/Spinal Cord Injury (> 48–72 hours old), or Extensive Burns/Crush Injury. Denervated muscle membranes upregulate extrajunctional nicotinic ACh receptors across the entire sarcolemma; depolarizing them with Succinylcholine causes massive potassium efflux and lethal hyperkalemic cardiac arrest! Use a non-depolarizing agent (Rocuronium) instead.
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Volume 2: Organ System Clinical Pathology • Chapter 18 of 60