Handbook of Genetic Counseling/Epilepsy and Seizures

Epilepsy and Seizures

Background

• Epilepsies
  • Group of disorders characterized by chronic, recurrent changes in neurologic function
  • Caused by abnormalities in electrical activity of brain
  • An individual with isolated, nonrecurrent seizures who are otherwise healthy do not have epilepsy
  • Prevalence is 0.5-1.0% in general population
• Seizures
  • An episode of neurologic dysfunction
  • Convulsive seizures are accompanied by motor manifestations or other changes in neurologic function
    • Sensory
    • Cognitive
    • Emotional
  • Classification is based on electroencephalographic pattern, clinical seizure type, and clinical context
    • Age of patient
    • Type of seizure
    • Presence of neurologic lesions

Classifications and Clinical Findings

• Partial or focal seizures
  • Begin with activation of neurons in only one part of the brain
  • Specific clinical symptoms depend on area of brain involved
  • Potential causes
    • Birth injury
    • Postnatal trauma
    • Tumor
    • Abscess
    • Infarction
    • Vascular malformation
    • Structural abnormality
  • Two subclassifications
    • Simple if no alteration in consciousness
    • Complex if lose awareness of the environment
  • Simple partial seizures
    • Recurrent contractions of muscles of one part of body without loss of consciousness
    • May remain confined to one area of body or spread to surrounding parts
    • May cause sensory symptoms (hallucinations) or psychic symptoms (unwarranted emotions)
  • Complex partial seizures
    • Episodic changes in behavior causing a loss of conscious contact with environment
    • May begin with illusions, hallucinations, feeling of déjà vu, or unusual smell
    • May see lip smacking, swallowing, walking aimlessly , automatisms, or unconscious performance of highly skilled activities
    • When seizure ends, individual experiences amnesia
  • Secondary generalization of partial seizures
    • Progression of partial seizure to loss of consciousness and convulsive motor activity
    • May happen after a few seconds or a few minutes
• Primary generalized seizures
  • Tonic-clonic (Grand mal)
    • Usually begin without warning
    • Cause sudden loss of consciousness, tonic contraction of muscles, loss of posture control, and cry as respiratory muscles contract
      • Individual may sustain injury when they fall to the floor
      • May suffer cyanosis if respiration inhibited
    • Clonic period of rhythmic contractions of all four limbs that lasts for variable period of time
    • Headaches, drowsiness, amnesia, incontinence, and tongue biting may occur
  • Tonic seizures
    • Sudden occurrence of rigid posturing of limbs and torso
    • Not followed by clonic phase and shorter in duration
  • Absence seizures (petit mal)
    • Sudden cessation of ongoing conscious activity
    • No convulsive muscular activity or loss of postural control
    • So brief they may not be apparent but may cause lapse of consciousness or awareness accompanied by minor motor manifestations
    • Usually begin in children 6-14
      • Often appear neurologically normal
      • Usually sensitive to antiepileptic drugs
      • 1/3 outgrow disorder, 1/3 continue to have only absence seizures, 1/3 have tonic-clonic seizures
  • Atypical absence
    • Similar to absence seizures by coexist with other forms of seizures
    • Occur in children with underlying neurologic dysfunction
    • Resistant to medication
  • Myoclonic seizures
    • Sudden, brief, single or repetitive muscle contractions involving one body part or entire body
    • May occur alone or with other types
    • Symptom of medical conditions
      • Uremia
      • Hepatic failure
      • Creutzfeldt-Jakob Disease
      • Subacute leukoencephalopathies
      • Lafora body disease
      • Juvenile Myoclonic Epilepsy (JME)
  • Atonic seizures
    • Brief loss of posture and consciousness
    • No muscular contraction
    • Usually occur in children
  • Infantile spasms or hypsarrhthmia
    • Occur in infants birth to 12 months
      • All signs of seizures disappear from ages 3-5
      • Suffer other types of generalized seizures later in life
    • Contractions of neck, torso, and both arms
    • Usually occur in children with neurological disease
      • Tuberous sclerosis
      • Anoxic encephalopathy
    • 90% of these children develop mental retardation
  • Febrile seizures
    • Controversial definition, prognosis, treatment, pathophysiology
    • Associated with fever but no evidence of intracranial infection or other cause
    • Usually occur from 3 months to 5 years of age
    • 2-6% go on to develop epilepsy
    • Estimated to occur in 2-5% of all Caucasian children
    • Family history reported in 7-58% of all children with these seizures
      • 8-15%% of first degree relatives may also be affected
      • Multifactorial inheritance
    • Recurrence risks for children of affected proband
      • 18.5% if only proband affected
      • 36.5% if proband and one parent affected
      • 45% if proband and both parents affected

Genetic Etiology

• Genetic influences may be chromosomal, dominant or recessive autosomal, X-linked, or multifactorial
• Environmentally induced seizures carry low recurrence risk for other family members

Differential Diagnosis

• Syncope
  • Fainting or a sudden loss of consciousness not involving convulsions
  • If origin unknown, patient should undergo cardiovascular evaluation, EEG with sleep recording, and prolonged ambulatory EEG monitoring
• Transient ischemic attacks and migraines
  • Transient alteration in neurologic function without loss of consciousness
  • Can undergo MRI or CT scan, carotid studies, and EEG precedures
  • Antiepileptic drugs may help migraines
• Pseudoseizures and "hysterical seizures"
  • Patients may appear emotionally disturbed and receive psychiatric treatment
  • Normal EEG but may have activity in deep temporal lobe not detected
  • May be eliminated or reduced by suggestion

Treatment and Management Options

• Eliminate cause, suppress expression, and deal with psychosocial consequences
• May be treated by correcting metabolic disturbance, hormonal disruptions, etc.
• Pharmacologic control
  • Goal is to prevent seizures without interfering with cognitive function
  • Many patients are resistant to medication
  • Teratogenic
• Neurosurgical treatment
  • Remove structural lesion and nearby diseased part of brain (e.g. - tumor)
  • May not help eliminate psychological disturbances that may occur

Psychosocial Issues

• Anxiety over potential future development of epilepsy
• Complications associated with pregnancy
• Difficulty assessing exact recurrence risks
• Frustration if unknown etiology or explanation
• Social stigma associated with neurological disorders
• Fear of potential seizures at school, in public, etc.

References

• Bird TD. "Epilepsy." The Genetic Basis of Common Disease. New York: Oxford University Press (1992).
• Dichter MA. "The Epilepsies and Convulsive Disorders." Principles of Internal Medicine. McGraw Hill, Inc. (1994).

Notes

The information in this outline was last updated in 2002.