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Handbook of Genetic Counseling/Epilepsy and Seizures

< Handbook of Genetic Counseling

Epilepsy and Seizures

Background

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  • 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

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  • 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

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  • 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

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  • 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

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  • 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

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  • 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

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  • 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

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The information in this outline was last updated in 2002.

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