CONVULSION & EPILEPSY Dr. Kifah Alubaidy

CONVULSION Seizure Is an intermittent derangement of the nervous system due to abnormal hypersynchronous discharges of cortical neurons. The manifestation of seizures depend on the location and extent of propagation of the discharge of cortical neuron.

Epilepsy Epilepsy is the occurrence of at least 2 unprovoked seizures. Recurrent seizures due to a chronic underlying process in the brain Manifested as repeated, stereotypic occurrence of the same experience Epilepsy is a clinical phenomena rather than a single disease entity.

prevalence Single seizure prevalence 5 – 10 %, with highest incidence at childhood & adult active epilepsy is only 0.3 - 0.5 %. Over two-thirds of all epileptic seizures begin in childhood (most in the first year of life)

Epilepsy Incidence Rates by Age

Mortality/Morbidity Sudden unexpected death in epilepsy is about 2.3 times higher than the general population. abrasions and tongue, facial and limb lacerations, Serious injury. fracture (crush a vertebral body) Periorbital hemorrhages, subdural hematoma burns

physiology

Pathophysiology Seizures require three conditions: A population of pathologically excitable neurons. An increase in excitatory glutaminergic activity through recurrent connections in order to spread the discharge. A reduction in the activity of the normally inhibitory GABA-nergic projections. A seizure results when a sudden imbalance occurs between the excitatory and inhibitory forces within the network of cortical neurons

Pathophysiology Generalized seizures are generated in the neocortex and are enhanced by the synchronizing influences of subcortical structures (midbrain reticular formation and its diencephalic projection to the thalamic systems). activity originates in these deep activating structures altere thalamocortical rhythms.

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Here is a diagram that shows a conceptual network for generalized seizures involving the corticothalamic circuitry. Theoretically a generalized seizure could start at different points in the network and engage bilaterally distributed networks. Thus a seizure could start frontally or even parietally. Here the conceptual diagram of the network is superimposed on a functional MRI of generalized spike wave activity. 11

Pathophysiology Severe seizures may be accompanied by a systemic lactic acidosis, reduction in arterial oxygen saturation, and rise in PCO2. These effects are secondary to the respiratory arrest and excessive muscular activity. If prolonged, they may cause hypoxic-ischemic damage to remote areas in the cerebrum, basal ganglia, and cerebellum. Heart rate, blood pressure, and particularly CSF pressure rise briskly during the seizure.

EEG

EEG

Classification of epilepsy Generalized seizures (10%) • Tonic–clonic • Absence Typical Atypical Absence with special features • Myoclonic absence • Eyelid myoclonia • Myoclonic Myoclonic Myoclonic atonic Myoclonic tonic • Clonic • Tonic • Atonic

Classification of epilepsy Focal seizures 80% of adult epilepsies Simple partial seizures Focal motor Focal sensory Complex partial seizure Secondarily generalized seizures Tonic Clonic Tonic–clonic