Case 2: Neonatal seizures

A 16-day-old female infant was brought to the emergency room because of jerking movements of her arms and legs, which occurred since day 2 of life. There was no cyanosis or apnea, and the movements did not stop with restraint. There had been no fever, and she had been bottle feeding well. During pregnancy, the mother tested positive for group B streptococcus, but antibiotics were not given in time because the infant was born precipitously. The patient was born at term with no complications. She had a complete blood count and blood culture, which was negative, and she was discharged after 48 h. On examination, her weight was 3.5 kg, length was 51 cm and her head circumference was 34.5 cm. She was afebrile and her vital signs were normal. She had a normal cardiorespiratory examination and no hepatosplenomegaly. Neurologically, her primitive reflexes were intact, and she had normal tone and deep tendon reflexes. A septic work-up, including complete blood count, blood cultures and all serum electrolytes, were negative. Urine culture from a catheter specimen was negative. There were three failed attempts at lumbar puncture. A head ultrasound was normal. She was started on empirical antibiotics and was admitted to hospital. Further history revealed the diagnosis. The parents reported that the movements only occurred during sleep and were always bilateral. They stopped upon arousal of their infant. There was no family history of seizures or developmental delay. The description was typical for benign neonatal sleep myoclonus (BNSM). A lumbar puncture was not repeated, and her antibiotics were discontinued. She was observed for 24 h and then discharged home, with follow up in her paediatrician's office. BNSM is a condition first described by Coulter and Allen in 1982. It is characterized by myoclonic jerks that can be bilateral or localized, rhythmic or arrhythmic, and occurs only during the drowsy or sleep state, particularly during non-rapid eye movement sleep. They typically last seconds to minutes, although cases of status epilepticus have been described in the literature. Symptom onset is in the first few days of life, and they resolve spontaneously by three to four months of age. The jerking movements cannot be stopped by restraint but will stop abruptly upon arousal. The movements can be triggered by gentle rocking in the head to toe direction. Because electroencephalogram (EEG) results are normal, BNSM is thought to be a sleep-related nonepileptiform phenomenon. No treatment is indicated, and there is always a normal neurological outcome. A family history of sleep myoclonus in adults can be determined in some families. The exact prevalence is unknown. It is important to differentiate between seizures and non-epileptiform movements in the neonatal period. Movements that can be reproduced by sensory stimuli and are stopped with gentle restraint are generally nonepileptic. BNSM is the exception because it stops only upon arousal. Other features of true seizure activity include changes in heart rate and blood pressure, apnea, abnormal eye movements, as well as abnormalities seen on neurological examination, EEG and/or neuroimaging. The etiology of seizures in the neonate includes infection, intracranial hemorrhage, hypoxic ischemic encephalopathy, cerebral malformations, metabolic causes (eg, glucose or electrolyte abnormalities), inborn errors of metabolism, toxic or withdrawal seizures, and neonatal epileptic syndromes. Neonatal epileptic syndromes include benign familial neonatal convulsions, benign idiopathic neonatal convulsions (also known as ‘fifth day fits’), early infantile epileptic encephalopathy and early myoclonic encephalopathy. The latter two are associated with severe seizures and generally poor outcome. Another epilepsy syndrome that does not typically present in the neonatal period is infantile spasms. Seizures in benign familial neonatal convulsions syndrome begin within two to 15 days of birth, most commonly on day 2 or 3 in an otherwise healthy baby. The seizures are usually of the clonic or tonic variety. The condition is auto-somal dominant; thus, a positive family history is crucial. These seizures disappear within the first year of life. Seizures in benign idiopathic neonatal convulsions syndrome typically begin on day 5 of life. They are clonic, either focal or repetitive multifocal, and are often associated with apnea. These seizures are self-limited, and disappear within a few weeks. Early infantile epileptic encephalopathy and early myoclonic encephalopathy are conditions that are characterized by severe recurrent seizures, progressive neurological deterioration, burst suppression pattern on EEG and, generally, a poor prognosis. The underlying etiology may be a structural brain abnormality or an inborn error of metabolism. Infantile spasms typically occur between three and seven months of age, but can occur as early as the first few weeks of life. This syndrome, called West syndrome, includes infantile spasms as the seizure type (clusters of flexor or extensor spasms), an abnormal EEG pattern called hypsarrhythmia, and cognitive plateau or regression. Neonates presenting with unusual movements require careful history and physical examination to rule out nonepileptic phenomenon, followed by careful consideration of all the potential etiologies of seizures. If the presentation is classical for BNSM, unnecessary investigations can be avoided. BNSM is a self-limiting condition with excellent outcome. Essential characteristics include: onset in the neonatal period; myoclonic jerks that are bilateral or localized, rhythmic or arrhythmic, occurring only during the drowsy or sleep state and stopping upon arousal; and a normal neurological examination. A full septic workup is not necessary if the neonate appears healthy and fulfills the criteria for BNSM, although careful consideration of other diagnoses is necessary. True seizures cannot be suppressed, are not elicited by sensory stimuli in most cases, and are associated with changes in eye movements, cardiorespiratory changes and abnormal neurological examination and imaging.

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