Seizures seen in the neonatal period are important since they can disrupt the integrity of the respiratory-circulatory system; besides, uncontrolled seizures cause serious brain damage and adversely affect the long-term prognosis. The convulsion threshold is lower in the immature brain than in the mature brain
3. While the incidence of seizures in full-term neonates is 1 to 3 per 1000 live births, it is reported to be 10 times higher in preterm newborns
1. Neonatal seizures have been reported to be more frequent among male infants
5. A naturally increased excitability was suggested in the neonatal period. The main reason for this is that glutamate, an excitatory neurotransmitter, is more excitatory, and gammaaminobutyric acid (GABA), an inhibitory neurotransmitter, is less inhibitory
6. In experimental studies, it has been shown that the gender- and age-related maturation of the GABAergic system as well as the seizure control function of the substantia nigra pars reticulata were controlled by gonadal hormones and their metabolites
7. While having a birth weight of <1500 gr and male sex are risk factors in preterm babies, delivery by cesarean section and young maternal age were found to be the most important risk factors in full-term babies
1,8,9. In this study, 14.8% of the infants were preterm and 85.2% were full-term newborns. Risk factors were determined in 57.4% of the infants, and the most common risk factors were asphyxia (31.2%), hypoglycemia (8.2%), and intracranial hemorrhage (6.6%). Lower rate of intracranial hemorrhage was attributed to the fact that the number of preterm babies was lower in our study than other studies. In a study by Tekgul et al.
5, cerebral hypoxicischemic encephalopathy and intracranial hemorrhage were reported to be the most common risk factors. Andre et al.
10 reported the etiology of neonatal seizures which were asphyxia in 49.3% of the patients, infections in 24%, intracranial hemorrhages in 14.1%, and metabolic disorders in 5.6%.
It was reported that the risk of seizure was highest in the first 48 hours of the neonatal period 11. Another study showed that the highest risk of seizure was in the first postnatal 24 hours which was an indicator of poor prognosis (4). While the subtle seizure is the most common type of seizures in the neonatal period, and the tonic seizures are least frequent 3. In this study, time of seizure onset was the first 24 hours in 36.1% of the infants, and no significant relationship was found between the time of seizure onset and epilepsy. The most common type of seizure was subtle (57.4%), and the least common was myoclonic (4.9%). Myoclonic seizures are more frequent in preterm than full-term infants 12. In this study 85% of the patients were full-term that may be the reason why myoclonic seizures are the least common. During the follow-up, epilepsy developed in 18.0% of patients, infantile spasm developed in 6.6% of patients and cerebral palsy developed in 3.3% of patients. In a study by Yıldız et al. 13, cerebral palsy was detected in 27.6%, epilepsy in 35.7%, and neurodevelopmental retardation in 50% of 112 newborns. Etiology, Apgar score, need for resuscitation at birth, neonatal status epilepticus, cranial imaging findings, type and duration of antiepileptic treatment, and response to acute treatment were reported to be strong prognostic factors for neurological outcomes. The incidence of epilepsy after neonatal seizures was detected 15.2% in a population-based study 14. It was reported that epilepsy had impact on the development of adverse neurological outcomes 15. In our study, developmental delay was more common among the patients who developed epilepsy (p <0.001).
Neuroimaging is very helpful in determining the underlying etiology of neonatal seizures, especially in full-term babies. While transfontanelle ultrasonography is preferred in the initial acute phase, MRI should be preferred in advanced imaging since it is able to show posterior fossa lesions and migration disorders. In the study by Tekgul et al. 5, good clinical prognosis was observed in all of the patients with normal MRI findings and focal cortical damage. Poor clinical prognosis was observed in 63% of the patients with multifocal-diffuse cortical damage and deep gray matter lesion. In another study, diffuse severe MRI abnormalities were found to be associated with poor prognosis and death 16. In our study, approximately half of the patients had normal or non-specific changes findings in MRI. The most common pathologic findings were porencephaly, periventricular white, and gray matter damage; and no relationship was found between MRI findings and epilepsy or neuromotor developmental retardation.
In another study, 31% of the patients were reported to have cerebral palsy, 43% have to developmental retardation, and 32% have to epilepsy, and also seizure type, time of seizure onset, and fifth minute Apgar scores were reported to be independent predictors of cerebral palsy. The mode of delivery, time of seizure onset, and etiology were found to be determinants of developmental delay 17. Neonatal seizures were reported to have a high mortality risk of 10-35% during the neonatal period 18. The fact that no infant death was observed in our patient sample might be due to the evaluation of patients in the pediatric neurology outpatient clinic.
In conclusion, seizures are most common neurological problems of the neonatal period. The development of epilepsy in patients with neonatal seizures are an important risk factor for neuromotor developmental retardation. Because this is a single-center study with a small number of patients, there is need for multicenter studies to examine the risk factors for, and pathogenesis of longterm adverse neurodevelopmental outcomes following neonatal seizures.
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