Lecture 21 Flashcards
What are seizures associated with
1) Change in mental state
2) Tonic or clonic movements
tonic–>musculature contractions
clonic–>jerking/repetitive movements
3) Abnormal electrical activity in the brain
What are convulsions
Type of seizure, always accompanied by involuntary jerking movements
Can be seen in epileptic attacks
Requirement for classification of epilepsy
Seizures must be recurrent and spontaneous (Epileptogenesis)
Epilepsy is common in early and late life (infants–>febrile seizures from fever)
What causes seizures
Abnormal brain activity
Diagnosis of epilepsy
1) EEG to pick up abnormal electrical activity (synchronous activity with large amplitude) in the cerebral cortex
2) Anatomical MRI to detect visible brain damage, sometimes found in epileptic brains
3) PET scan, to identify regions of brain with abnormal glucose metabolism, synonymous with abnormal neuronal activity
2 types of seizures
1) Focal onset/partial onset
seizures focused on 1 brain hemisphere, patients are conscious
Focal aware, focal impaired awareness
2) Generalized onset
Seizures occur in both hemispheres, throughout the cortex and more, patients are unconscious
Generalized tonic-clonic, generalized absence seizures
What does Focal aware seizures involve
Either sensory and/or motor systems
Somatosensory (contralateral tingling of limb, face, or side of body), visual (flashes of light, scotomas, unilateral or bilateral blurring), auditory (ringing, hissing), autonomic (sweating, flushing, epigastric sensations), contraversive (head and eyes turned to opposite sides), focal motor (tonic-clonic movements of upper or lower limb)
Focal impaired awareness seizures
1) Affect temporal lobe, most common type of epilepsy
2) Preceded by an aura (intense deja vu, gut feeling, or sensory hallucination)
3) Simple automatisms (involuntary repetitive movements)
4) Psychomotor attacks (may walk and talk (appear conscious) but won’t remember
Characteristic of a Generalized tonic-clonic seizure (grand mal)
Immediate and complete loss of consciousness, loss of balance, and impairment of breathing (leading to hypoxia and acidosis)
3 main phases of generalized tonic-clonic seizures
1) Tonic phase: lasts 30 seconds, muscles of arms, legs, and trunk will stiffen
2) Clonic phase: lasts 1-3 minutes, muscles of arms, legs, and face will rapidly and intensely extend and flex, jerky movements
3) Post-ictal phase: post seizure phase, muscles are sore, regain consciousness, tired, nausea, confusion
Characteristic of a Generalized absence seizure (petit mal)
1) EEG reading presents a recognizable 3Hz pattern
2) Common in children
3) Lose consciousness–>zone out (cessation of talking, staring into space, fluttering eyelids) lasting 10 seconds
Normal EEG
Larger amplitude at occipital cortex–>alpha rhythm
Present in a conscious, awake person at rest
Neuron activity in Generalized TONIC-clonic seizures (grand mal)
Tonic phase–>sustained depolarization of neurons, rapid and continuous firing of action potentials
Neuron activity in Generalized tonic-CLONIC seizures (grand mal)
Clonic phase–>pacemaker activity in neurons, multiple action potentials being fired with each depolarization event
Neuron activity in Generalized absence seizures (petit mal)
Slow pacemaker activity of neurons, depolarization results in multiple action potentials firing hence a SPIKE on 3Hz spike-and-wave EEG pattern
Epilepsy side effects
Head injury, anoxia, stroke, tumors, infections, genetic defects, etc
Some epilepsies are inherited (high concordance for epilepsy between monozygotic twins)
What directly causes Epilepsy
Altered Ion channels (voltage gated Na+ and K+ channels)
Can be inherited mutations and acquired damage to ion channels
BUT NO CURE, nor a drug that is anti-epileptic just anticonvulsant
What is Epileptogensis
The underlying pathological process occurring in the brain that results in the development of spontaneous recurrent seizure activity
No drug can prevent/stop this process, hence chronic treatment
Targets for anti-seizure drugs
Voltage gated ion channel activity, glutamate inhibition, GABA potentiation
Action of many anti-seizure drugs
Mimic or potentiate the GABA inhibitory pathways or inhibit the glutamate excitatory pathways
3 ways to affect GABA system
1) Stimulation of GABA postsynaptic receptors
2) Inhibition of GABA transaminase
3) Inhibition of the GABA transporter
Effect of Stimulating GABA postsynaptically with agonist
Agonist: benzodiazepines, and phenobarbital (barbiturate(
Increases inhibition of postsynaptic neuronal firing, including excitatory neurons
Effect of Inhibiting GABA transaminase
Inhibit metabolism of GABA–>more GABA in synapse–>Increase GABA postsynaptic action
Effect of Inhibition of GABA transporter
Prevents reuptake of GABA by glial cells and neurons–>increases amount of GABA at synapse–>Increases GABA postsynaptic action
