1.Incidence
(1) It is generally believed that the overall incidence of epilepsy observed clinically after craniocerebral injury is 5% to 15%. Other statistics show that the incidence of epilepsy in the general population is 0.5% to 2%, the incidence of post-traumatic epilepsy is 2% to 2.5%, and the incidence of penetrating craniocerebral trauma is as high as 50%. The incidence after open and closed craniocerebral trauma is 20%～50% and 0.5%～5%, respectively, and the incidence of firearm and non-firearm open injuries is 42.1% and 16.4%, respectively.
(2) Early epilepsy accounts for 5%, 1/3 occurs within 1 hour after injury, 1/3 occurs 2 to 24 hours after injury, 1/3 occurs 2 to 7 days after injury, mainly related to intracranial hemorrhage, depressed fracture and foreign body stimulation. Early epilepsy is more common in children, but the incidence of late epilepsy in children is significantly lower than that in adults.
(3) Late epilepsy accounts for about 84%, with more than half occurring within 1 year after injury, 70% to 80% within the second year, and about 1/5 starting 4 years after injury and more persistent; mainly related to brain tissue scar formation, brain atrophy and intracranial infection, brain abscess formation, intracerebral cysts, brain penetrating malformation, foreign body retention and fracture fragments.
(4) Twenty-five percent of early epilepsy can be continued into late epilepsy, but the occurrence of late epilepsy is not related to the type and number of seizures in early epilepsy.
(5) The incidence of epilepsy gradually decreases with time, and the risk of seizures in the majority of patients 5 years after trauma is not different from that of the general population.
2. Risk factors
The incidence of traumatic epilepsy is 12 times higher than that of the general population. Factors associated with causing post-injury epilepsy include
(1) Site of injury: the closer to the cortical motor area or the hippocampus and amygdala of the medial temporal lobe, the more likely epilepsy will occur.
(2) Type, nature and extent of injury.
The incidence of early epilepsy in subdural hematoma and intracerebral hematoma is 30% to 36%, the incidence of epidural hematoma, depressed fracture of the frontal bone or parietal bone is 9% to 13%, and the incidence of mild brain injury without neurological signs is only 1% to 2%.
(3) Age: children under 5 years old have a high incidence of early epilepsy after traumatic brain injury and are prone to persistent status epilepticus; traumatic epilepsy is mainly concentrated in young people, with more males than females.
(4) Whether it is open brain injury: the incidence of severe head trauma with neurological deficit and cortical injury is high, especially in those with dural rupture.
(5) Relationship with complications: the incidence is high in those with post-injury respiratory distress and shock, and is closely related to subarachnoid hemorrhage, acute cerebrovascular spasm, and intracerebral hematoma.
(6) Nature of brain injury.
Cerebral penetrating injuries are higher than non-penetrating injuries (5 to 10 times). The incidence after open brain injury and closed craniocerebral trauma is 20% to 50% and 0.5% to 5%, respectively, and the incidence after firearm and non-firearm open injuries is 42.1% and 16.4%, respectively.
3.Predictors of late-stage epilepsy incidence
(1) Early epilepsy: early seizures after traumatic brain injury.
(2) Risk factors for late seizures
Limited neurological deficit at the first check, projection-induced brain injury, frontal lobe injury, intracerebral hemorrhage, extensive cerebral contusion, prolonged post-injury amnesic symptoms, depressed fracture, and cortical-subcortical injury.
(3) EEG (electroencephalogram): pathologically abnormal EEG manifestations.
(4) Medical factors: such as antiepileptic drugs can cause hypotension, causing hemodynamic instability, resulting in a further decrease in blood flow to the tissue in the brain injury area.
(5) Hematoma and type of brain damage.
Late epilepsy can occur in about 1/5 patients with epidural hematoma and about 1/2 patients with subdural and intracerebral hematoma; late epilepsy can occur in 1/3 of those with open cranial injury, especially firearm injury.