Epilepsy: Definition and Characteristics

Introduction to Epilepsy

• Epilepsy is a chronic seizure disorder characterized by recurring seizures without a consistent provoking factor.
• Epilepsy is not contagious, not a mental illness, and not a cognitive disability.
• The neurological dysfunction in epilepsy can begin at birth, childhood, adolescence, or adulthood.

Classification of Seizures

• Partial Seizures
  • Simple seizures (without impairment of consciousness)
    • With motor symptoms
    • With special sensory or somatosensory symptoms
    • With psychic symptoms
  • Complex seizures (with impairment of consciousness)
    • Simple partial onset followed by impairment of consciousness
    • Impaired consciousness at onset
  • Secondarily generalized (partial onset evolving to generalized tonic-clonic seizures)
• Generalized Seizures
  • Absence
  • Myoclonic
  • Clonic
  • Tonic
  • Tonic-clonic
  • Atonic
  • Infantile spasms
• Unclassified Seizures
• Status Epilepticus

Partial Seizures

• Common, occurring in 80% of patients
• Simple partial seizures do not cause loss of consciousness
• Signs and symptoms:
  • Motor – convulsive jerking, chewing motions, lip smacking
  • Sensory and somatosensory – paresthesias, auras
  • Autonomic – sweating, flushing, pupil dilation
  • Behavioral – hallucinations, dysphasia, impaired consciousness (rare)

Complex Partial Seizures

• Impairment of consciousness
• Purposeless behavior is common
• Aggressive behavior (violence) automatism (e.g., picking at clothes)
• Visual, auditory, or olfactory hallucinations

Generalized Seizures

• Affecting both hemispheres
• 3 types:
  • Idiopathic epilepsies (age-related, genetic origin)
  • Symptomatic epilepsies (consequence of a known/suspected underlying disorder of CNS)
  • Cryptogenic epilepsies (hidden course, age-related)

Absence Seizures (Petit Mal)

• Alterations of consciousness (absence) lasting 10-30 seconds
• Staring (with occasional eye blinking) and loss of postural tone
• Onset occurs from 3-16 years, disappearing by 40 years

Other Types of Seizures

• Myoclonic: sudden, involuntary jerking of facial, limb, or trunk muscles
• Clonic: sustained muscle contractions alternating with relaxations
• Tonic: sustained muscle stiffening
• Tonic-clonic (grand mal): sudden loss of consciousness, followed by tonic and clonic phases
• Atonic (drop attacks): sudden loss of postural tone, primarily in children

Causes of Epilepsy

• Stroke
• Brain tumor
• Brain infection
• Past head injury
• Drug use, alcohol withdrawal
• Epilepsy may occur with:
  • Metabolic problems
  • Other neurological conditions
  • Genetic factors
  • Developmental disabilities
  • Autism
  • Cognitive impairments

Pathophysiology

• Paroxysmal discharges in cortical neurons
• Abnormal firing of neurons
• Breakdown of normal membrane conductance and inhibitory synaptic currents
• Abnormality of potassium conductance
• Defect in voltage-sensitive ion channels
• Deficiency in membrane ATPase
• Membrane instability promotes deficiency of inhibitory neurotransmitters and increase in excitatory neurotransmitters
• Abnormal neuronal activity

Diagnosis

• Electroencephalogram (EEG)
• Neurological imaging studies:
  • Magnetic Resonance Imaging (MRI)
  • Functional MRI (fMRI)
  • Computed Tomography (CT)
  • Positron emission tomography (PET)
  • Single-photon emission computerized tomography (SPECT)

Management

• Status epilepticus: Diazepam, Phenytoin, Phenobarbital
• Psychomotor seizure: Phenytoin
• Lennox-Gastaut syndrome: Valproic acid, Felbamate, Lamotrigine, Topiramate, Rufinamide