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Neuroscience > Week 1 - Role of ion channels in epilepsy > Flashcards

Week 1 - Role of ion channels in epilepsy Flashcards

1
Q

definition of a seizure

A

abnormal excessive and synchronous electrical discharges of brain neuronal network
-paroxysmal events characterized by clinical signs and/or symptoms

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2
Q

aura

A

ictal; very short part of seizure (symptoms)

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3
Q

prodrome

A

pre-ictal; feeling that a seizure is coming, but not part of a seizure yet

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4
Q

ictal

A

seizure period or events due to seizure

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5
Q

interictal

A

period between 2 seizures (symptom-free)

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6
Q

post-ictal

A

when seizure is over (symptoms like fatigue, temporary loss of function)

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7
Q

ILAE classification of epileptic seizures

A
  1. partial/focal (one hemisphere, size doesn’t matter)
    - simple (no loss or impaired consciousness, but motor symptoms present)
    - complex (impaired consciousness)
    - both may lead to secondary generalized (start from one hemisphere and spread to another
  2. generalized (both hemispheres)
    - convulsive (most common)
    - non-convulsive (no clinical manifestations except unconsciousness)
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8
Q

types of simple partial seizures

A
  • motor signs
  • somatosensory or special sensory symptoms
  • autonomic symptoms or signs
  • psychic symptoms
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9
Q

types of complex partial seizures

A
  • simple partial onset followed by impairment of consciousness
  • with impairment of consciousness at onset
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10
Q

types of partial seizures evolving to secondarily generalized seizures

A
  • simple partial seizures evolving to generalized seizures
  • complex partial seizures evolving to generalized seizures
  • simple partial seizures evolving to complex partial seizures evolving to generalized seizures
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11
Q

types of generalized seizures

A
  1. absence seizures (most common in kids via behavioral arrest for a few seconds, then resume)
    - typical or atypical absence
  2. myoclonic seizures
  3. clonic seizures
  4. tonic seizures
  5. tonic-clonic seizures
  6. atonic seizures
  7. unclassified epileptic seizures
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12
Q

what is epilepsy?

A

disease of brain characterized by enduring predisposition to generate epileptic seizures (acute change in electrolytes)

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13
Q

what is an epilepsy syndrome?

A

an electroclinical syndrome

-complex of clinical features, signs, and symptoms that together define a distinctive, recognizable clinical disorder

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14
Q

ILAE classification for epileptic syndromes

A
  1. idiopathic - presumed genetic etiology
  2. symptomatic - consequence of a known or suspected disorder of CNS
  3. cryptogenic - unknown cause
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15
Q

epileptic channelopathies

A

lowered seizure threshold based on mutation causing changes in current carried by channel

  • enhanced (gain of ion channel function) or reduced (loss)
  • majority are autosomal dominant or de novo mutations
  • rarely autosomal recessive
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16
Q

variations of alpha subunit of Na+ channels

A

9 variations, mostly in CNS

  • Nav1.1 and Nav1.3 in cell bodies
  • Nav1.2 in unmyelinated axons and dendrites
  • Nav1.6 in myelinated axons and dendrites
17
Q

severe myoclonic epilepsy of infancy

A

SMEI or Dravet syndrome; due to Nav1.1 mutation

  • 1st year of life: seizures associated with elevated body temp (fever or bathing)
  • -progressively prolonged and cluster seizures
  • -status epilepticus
  • 2nd year of life: psychomotor delay, ataxia, and cognitive impairment
18
Q

pathophysiology of SMEI

A
  1. loss of high-frequency APs
  2. loss of inhibitory function of GABA-ergic cortical interneurons (leads to seizures) and Purkinje cells (leads to ataxia)
19
Q

pharmacological transcription for SMEI

A

try to re-establish GABA-ergic transmission

  • tiagabine –> decrease reuptake of GABA
  • benzodiazepine (clonazepam) –> increase in response of post-synaptic GABA receptors
20
Q

generalized epilepsy with febrile seizures plus

A

GEFS+; milder than SMEI, usually no cognitive impairment

  • first mutation was found in SCN1B (encoding B-1 subunit)
  • later SCN1A mutations were found
21
Q

pathophysiology of GEFS+

A

mutations (usually missense) –> loss of function of fast inactivation –> gain of function of Na+ channel –> persistent Na+ current

22
Q

treatment of GEFS+

A

antiepileptic medications that can potentially bind to mutant channels and stabilize folding of PRO

23
Q

ILAE definition of febrile seizures

A

seizure occuring in childhood after 1 month of age

  • associated with febrile illness not caused by infection of CNS
  • w/o previous neonatal seizures or previous unprovoked seizure
24
Q

what causes febrile seizures?

A

mutations in Nav1.1

  • reduction of peak Na+ currents
  • positive shift in voltage dependence of activation
25
Q

Nav1.1 mutation severity (from mild to severe to truncation)

A

febrile seizures –> GEFS+ –> SMEI

26
Q

2 types of K+ channelopathies in epilepsy

A
  1. Kv7.2 and Kv7.3 subunit, mostly in cells with M current
    - M current is close to the resting potential, and is regulated by muscarinic and other G-PRO coupled receptors
    - missense mutation –> impaired flux of K+ (loss of function) –> decreased M current
  2. pore-forming subunit encoded by KCNMA1
    - mutation –> larger K+ flux (gain of function)
    - generalized epilepsy and paroxysmal dyskinesia
27
Q

benign familial neonatal convulsion (BFNC)

A

missense mutation causing decreased M current (impaired flux of K+)

  • normal development and behavior
  • brief generalized and partial seizures resolve by age 6 weeks
28
Q

Ca++ channelopathies in epilepsy

A

T-type Ca++ channels

  • can have rhythmic burst-firing b/c
  • -activated with small depolarization
  • -inactivated with maintained depolarization
  • mostly in thalamic cells
  • subtypes are Cav3.1/2/3 encoded by CACNA1G/H/1l
  • mutations –> gain of function –> excessive synchronous rhythmic burst firing –> idiopathic generalized epilepsy
29
Q

Cl0 channelopathies in epilepsy

A

12 trans-membrane segments

  • maintain Cl- gradient required for GABAergic synapses and hyperpolarization
  • mutations in CLCN2 gene can lead to idiopathic generalized epilepsy
30
Q

antiepileptic drugs

A

AED; decrease hyperexcitability of neurons

  • Na+ channel blockers/stabilizers
  • -prevent return of channels to active state by prolonging inactive/refractory state
  • increasing inhibitory function of neurons
  • -GABA-ergic medication
31
Q

epilepsy surgery

A

not all seizures are channelopathies, so surgery considered in localization related epilepsy that is medically refractory

  • given if fail to respond to 2 medications
  • if seizure onset zone can be identified, and is not in eloquent cortex

Neuroscience (39 decks)

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