Spagnoli et al, talian Journal of Pediatrics2018
Neonatal seizures are the most common neurological event in newborns, showing higher prevalence in preterm than in full-term infants. In the majority of cases they represent acute symptomatic phenomena, the main etiologies being intraventricular haemorrhage, hypoxic-ischemic encephalopathy, central nervous system infections and transient metabolic derangements.
Current definition of neonatal seizures requires detection of paroxysmal EEG-changes, and in preterm newborns the incidence of electrographic-only seizures seems to be particularly high, further stressing the crucial role of electroencephalogram monitoring in this population. Imaging work-up includes an integration of serial cranial ultrasound and brain magnetic resonance at term-equivalent age. Unfavourable outcomes following seizures in preterm infants include death, neurodevelopmental impairment, epilepsy, cerebral palsy, hearing and visual impairment. As experimental evidence suggests a detrimental role of seizures per se in determining subsequent outcome, they should be promptly treated with the aim to reduce seizure burden and long-term disabilities. However, neonatal seizures show low response to conventional anticonvulsant drugs, and this is even more evident in preterm newborns, due to intrinsic developmental factors. As a consequence, as literature does not provide any specific guidelines, due to the lack of robust evidence, off-label medications are often administered in clinical practice.
Neonatal seizures in newborns are clinically defined as abnormal, stereotyped and paroxysmal dysfunctions in the central nervous system, occurring within 44 weeks of gestational age.
From a clinical point of view, neonatal seizures are divided into clonic, myoclonic, tonic and subtle seizures. Clonic seizures consist of repetitive, rhythmic (1–4/s) contractions of muscle groups of the limbs, face or trunk. They can be focal or multifocal. They are usually electrically-confirmed. Myoclonic seizures are isolated or repetitive contractions of proximal or distal muscles, less regular and persistent than clonic jerks. They can be generalized, focal or multifocal. Tonic seizures are classified as generalized or focal. Focal tonic seizures consist of sustained, but transient, asymmetrical posturing of the trunk or extremities or tonic eye deviation, while generalized tonic seizures are bilateral symmetrical tonic posturing (with flexor/extensor predominance or mixed). Electrographic correlate is inconsistent for both seizure types. Subtle seizures include motor automatisms (such as chewing, swallowing, sucking, repetitive tongue movements, “cycling”, “boxing”, “pedaling”, “swimming”) and autonomic signs (changes in heart rate or breathing pattern, flushing, salivation, pupil dilatation).
Neurophysiologically a seizure is defined as the presence of a paroxysmal EEG change with a clear onset and termination, lasting at least 10 s, and an evolution in frequency, morphology and amplitude.
As above said, the prevalence of neonatal seizures is higher in preterm (22.2%) than in full-term newborns (0.5%) but studies about clinically-defined seizures show a larger percentage of neonatal seizures than EEG-based studies, especially aEEG-based ones. For example, a prospective study about infants born before the 32nd week of gestational age found a 5% incidence of neonatal seizures. In contrast, 11.9% incidence has been reported in studies on clinically-diagnosed seizures.
Clinical-only seizures (without any electrographic evidence), are usually considered non-epileptic and related to the loss of cortical inhibition on subcortical structures.
Paroxysmal non-epileptic motor phenomena should be taken into consideration in the differential diagnosis.
No general consensus has been achieved on the definition of neonatal status epilepticus. A commonly adopted definition considers it as continuous seizure activity lasting ≥30 min or the occurrence of recurrent seizures ≥50% of the recording time (1–3 h)