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Genetic counseling: Epilepsy and Seizures

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Epilepsy and Seizures

BackgroundEdit

  • 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 electroencephalograhic pattern, clinical seizure type, and clinical context
      • Age of patient
      • Type of seizure
      • Presence of neurologic lesions

Classifications and Clinical FindingsEdit

  • 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 (unwarrented 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 encepalopathy
      • 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 EtiologyEdit

  • 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 DiagnosisEdit

  • 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 OptionsEdit

  • 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 (eg - tumor)
    • May not help eliminate psychological disturbances that may occur

Psychosocial IssuesEdit

  • 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

ReferencesEdit

  • 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).

NotesEdit

The information in this outline was last updated in 2002.



This material has been imported fom the wikibook "Genetic counseling"[ http://en.wikibooks.org/wiki/Genetic_counseling] under the GNU Free Documentation License.

Heckert GNU white Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License."

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