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Seizure Disorder, Focal

BASICS

  • Definition: Seizures from abnormal synchronous neuronal discharges limited to one hemisphere (“focal” or “partial”).
  • Classification:
  • Focal aware (simple partial): No impairment of awareness
  • Focal impaired awareness (complex partial): Impaired responsiveness/awareness
  • Motor onset: Tonic, clonic, myoclonic, or other motor symptoms
  • Nonmotor onset: Sensory, autonomic, cognitive, or emotional features

EPIDEMIOLOGY

  • Prevalence: ~20 per 100,000 persons in the US
  • Etiology by age:
  • Early childhood: developmental malformation, trauma
  • Young adults: developmental, infection, trauma
  • Middle/older adults: stroke, trauma, infection, neoplasm

ETIOLOGY & PATHOPHYSIOLOGY

  • Focal onset: Abnormal depolarization of neuronal network in one hemisphere; can stay local or spread.
  • Symptoms: Depend on location (motor, sensory, temporal, parietal, occipital)
  • Genetics: E.g., benign rolandic epilepsy (autosomal dominant)
  • Other risk factors: TBI, thiamine deficiency

RISK FACTORS

  • History of TBI
  • Thiamine-deficient formula in infancy
  • Drugs/lower seizure threshold (tramadol, bupropion, cocaine, theophylline)
  • Prior neurologic disease

COMMONLY ASSOCIATED CONDITIONS

  • Depression

DIAGNOSIS

HISTORY

  • Detailed eyewitness account is crucial
  • Duration: seconds–minutes unless status epilepticus
  • Review meds and substance use
  • Ask about prior TBI, comorbidities

FEATURES

Focal aware (simple partial): - Motor onset: tonic/clonic movements, can show Jacksonian march - Nonmotor onset: sensory symptoms, visual/auditory/olfactory hallucinations, déjà vu, autonomic changes - Todd paralysis: temporary weakness post-seizure

Focal impaired awareness (complex partial): - May start with aura (sensory, psychic, autonomic) - Amnesia for the event, postictal confusion - Automatisms: lip smacking, picking, wandering - Commonly temporal or frontal origin

PHYSICAL EXAM

  • Neurologic exam, look for lateralizing signs

DIFFERENTIAL DIAGNOSIS

  • Syncope
  • Psychogenic nonepileptic seizure
  • Hypoglycemia
  • TIA, hemiplegic migraine
  • Other paroxysmal events

DIAGNOSTIC TESTS

  • Lab: CBC, metabolic panel, urinalysis, drug screen, AED levels if relevant
  • Serum prolactin/CK: May be elevated postictally (within 10–20 min for prolactin, 6–24h for CK); may help distinguish true seizure from psychogenic
  • EEG: Consider for all first unprovoked seizures (best yield within 24h, especially with sleep deprivation)
  • Imaging: CT/MRI to rule out acute/structural causes (esp. new seizure, older age, abnormal exam)
  • CSF: If infection suspected
  • Video-EEG: For diagnostic uncertainty

TREATMENT

GENERAL MEASURES

  • Maintain seizure diary (identify triggers: sleep deprivation, stress, drugs, menses, alcohol withdrawal)
  • Driving: Most states restrict driving after seizures; counsel accordingly

MEDICATION

  • After a single unprovoked seizure: Shared decision-making; AEDs decrease recurrence risk over 2 years but do not affect long-term remission/mortality; increased risk of side effects with immediate AED use
  • First-line AEDs for focal epilepsy:
  • Carbamazepine: Sodium channel blocker; SE: GI distress, hyponatremia, diplopia, rare marrow suppression/rash (screen Asians for HLA-B*1502)
  • Oxcarbazepine: Similar to carbamazepine; less marrow suppression; SE: dizziness, diplopia, hyponatremia
  • Lamotrigine: Sodium channel blocker; SE: insomnia, ataxia, serious rash risk (esp. with valproate; titrate slowly)
  • Levetiracetam: Multiple mechanisms; SE: sedation, irritability, ataxia
  • Second-line/adjuncts: Phenytoin, phenobarbital, valproate, topiramate, gabapentin, pregabalin, zonisamide
  • AEDs & pregnancy: All women of childbearing age on AEDs need folate. Avoid valproate and phenytoin if possible (risk of fetal malformation)
  • Monitor: AED levels as appropriate, especially in pregnancy, if toxicity suspected, or for breakthrough seizures

REFERRAL/ADDITIONAL THERAPIES

  • Refer to epilepsy specialist for refractory seizures
  • Vagal nerve stimulator or deep brain stimulation for refractory cases
  • Surgery: Resection for refractory focal epilepsy with localized focus (pre-op Wada test, MRI, etc.)
  • Ketogenic/low-glycemic diet: Can help in some refractory cases

ONGOING CARE

  • Avoid triggers: Alcohol, sleep deprivation, drug use
  • Driving/safety counseling
  • Monitor AED side effects and drug interactions
  • Follow-up: Regular review of seizure diary, labs, and imaging as needed

PROGNOSIS

  • ~30% risk of recurrence after a first seizure
  • Most recurrences occur within 6 months–2 years
  • About 25–30% of focal epilepsies are refractory to current AEDs
  • Benign rolandic epilepsy: good prognosis; temporal lobe epilepsy: often persistent

COMPLICATIONS

  • Injury (accidental, e.g., falls, burns)
  • Depression, anxiety, memory/cognitive impairment

ICD-10

  • G40.109: Local-rel symptomatic epilepsy with simple partial seizures, not intractable, w/o status
  • G40.209: Local-rel symptomatic epilepsy with complex partial seizures, not intractable, w/o status
  • G40.119: Local-rel symptomatic epilepsy with simple partial seizures, intractable, w/o status

CLINICAL PEARLS

  • Focal seizures arise from a discrete focus, classified by awareness and motor/nonmotor onset
  • EEG and neuroimaging (CT/MRI) should be considered in first-time seizures
  • Postictal prolactin and CPK help distinguish physiologic from psychogenic seizures
  • Treatment after a first seizure is controversial; consider AED if structural cause or high risk of injury
  • 50% respond to first AED; many require combination therapy or advanced therapies if refractory