Myoclonus epilepsy with ragged-red fibers
Jun. 10, 2021
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Neonatal seizures are seizures occurring within the first 28 days in a full-term infant and extending to the 44 completed weeks gestational age in the preterm infant. The neonatal period is the most vulnerable of all periods of life for development of epileptic seizures. Most neonatal seizures are acute reactive (structural/metabolic) seizures. In term babies, the most common cause is hypoxic-ischemic encephalopathy, stroke, or infection. The age at onset of the seizure typically depends on the etiology. Determining the etiology requires immediate attention in order to diagnose and treat if appropriate. The seizures typically resolve once the underlying trigger subsides. Neonatal seizures, depending on etiology, may or may not be associated with adverse neurodevelopmental sequelae or death, with possible long-term motor and cognitive problems, or with post-neonatal epilepsy.
• The neonatal brain is more prone to seizures than the mature brain.
• Most neonatal seizures are acute reactive seizures, the most common cause in term infants being hypoxic-ischemic encephalopathy, stroke, or infection. Neonatal onset epilepsy syndromes also exist but are less common.
• The most commonly used current classification of neonatal seizures divides the seizures into clonic, tonic, myoclonic, and motor automatisms/subtle. A new classification is being proposed by the International League Against Epilepsy Task Force on Neonatal Seizures.
• About 60% to 70% of neonatal seizures are subclinical and would not be diagnosed/recognized without continuous EEG monitoring.
• Phenobarbital is a first-line treatment for neonatal seizures. Fosphenytoin/phenytoin can also be used or added for additional benefit, as well as midazolam. Additional medications that may be used as an off-label medication include levetiracetam or topiramate. There is a need for new treatments that are age specific.
More than 50 years ago, seizures in the neonatal period were known for their strong relation to permanent handicap in the survivors (08). Our understanding of neonatal seizures has evolved over the years, and the methods of recording seizures by EEG have become more refined (digital EEG and continuous video-EEG monitoring). Conventional EEG is the current gold standard to detect neonatal seizures (84; 82; 68).
Neonatal seizures differ clinically from those of older children and adults as the neonatal brain is not fully myelinated. Neonatal seizures may be difficult to diagnose accurately because movements in sick babies can be misinterpreted and treated as seizures. Additionally, clinical recognition of seizures may be difficult because neonatal seizures are often subtle and imitate reactions and behaviors that are normally seen in neonates (49). There are unique clinical features that distinguish neonatal seizures from seizures in a more mature brain. For example, focal clonic seizures are often asynchronous if they occur bilaterally and do not spread in a typical Jacksonian sequence (11).
Neonatal seizures do not have features of generalized seizures seen in other age groups. With the use of EEG monitoring, neonatal seizures are broadly categorized as 1) epileptic events, when associated with consistent electrographic patterns, 2) nonepileptic events, when there is no electrographic correlate, and 3) electrical seizures, when EEG seizure discharges are not associated with obvious clinical manifestations (54).
Mizrahi and Kellaway use the term “motor automatisms” to describe paroxysmal behaviors such as irregular and disconjugate ocular movements, eye-opening, chewing, oral-buccal movements, and peculiar extremity movements. Not all of them will have an EEG correlate, so the diagnosis will depend on EEG findings.
The International League Against Epilepsy (ILAE) Task Force on Neonatal Seizures was established in 2014 and proposed a neonatal seizure framework that can be integrated into the ILAE classification of the epilepsies (72). The framework uses the same categories and terminology of the current ILAE seizure classification but is adapted to neonates and emphasizes the role of the EEG in the diagnosis (17). The clinical seizure was described as either clonic, tonic, myoclonic, automatisms, epileptic spasms, autonomic, or sequential (72). A sequential seizure was used when there was no predominant seizure type and the clinical features occurred in a sequence. Once the seizure is appropriately classified, the clinical seizure can be used to identify the presumed etiology (Nunes, 2019).
The prognosis of the seizures varies according to the underlying etiology. A proven brain injury generally portends a more serious prognosis. The background activity in the EEG can serve as a prognostic marker; a normal background favors a better prognosis (50). Severely abnormal EEG background at 36 and 48 hours after birth is shown to be associated with severe injury on MRI brain and abnormal neurodevelopmental outcome (98). EEG abnormalities and ictal seizure activity in the EEG are associated with worse prognosis compared to normal EEG findings (43). This is especially true for preterm neonates (80). Typically, the earlier the seizures occur, the worse the prognosis. Seizures occurring within the first 3 days of life were associated with increased risk of intraventricular hemorrhage, white matter injury, and death (96). However, it is the etiology of the seizures that truly determine the outcome. For instance, self-limited neonatal seizures are brief and frequent with a high seizure burden, but the seizures usually remit within 1 year of age, and it is not associated with poor outcome.
The risk of developing epilepsy after neonatal seizures varies in different studies, from 2% to 56%, and largely depends on etiology. Also, depending on the study, the adverse outcome is reported anywhere from 30% to 90% (27). Seizures persisting despite antiseizure treatment in children receiving 2 or more antiseizure drugs were highly prognostic for poor outcome. Treatment failure with 3 or 4 antiseizure drugs, as opposed to 2 antiseizure drugs, increased the risk of poor outcome (47; 93; 79). The outcome of symptomatic seizures depends on the treatment of the underlying condition. The mortality rate is 15% in developed countries and up to 40% in developing countries (64).
The patient is a product of a twin gestation (twin B) born at 38 weeks via vaginal delivery, with Apgar scores of 0, 2, and 4. At delivery, she was described as depressed, floppy, and pale. She met criteria for brain cooling, and the head cooling protocol was initiated. An hour after birth, she was noted to have abnormal twitching of her mouth; therefore, she was loaded with phenobarbital 20 mg/kg. An EEG was obtained, and she was noted to have an electroclinical seizure arising in the right frontal region. Clinically, she was having irregular tonic leg movements associated with the discharge. Phenobarbital was pushed to a level of 40 mcg/ml. During the rewarming, she continued to have electrographic seizure patterns. She was then loaded with fosphenytoin, and the 24-hour EEG did not reveal any electrographic or electroclinical seizures. She was tapered off the fosphenytoin while she was in the NICU and was given a phenobarbital taper schedule on discharge.
Motor seizures of clonic type consist of focal, rhythmic, usually slow (approximately 1 to 3 jerks per second), repetitive movements of the face, proximal or distal arm or leg muscles, or axial structures. They can be multifocal or unilateral and may spread. Focal clonic seizures are usually associated with focal brain lesions such as cerebral infarctions, but can also occur with more diffuse neuropathologic processes (62). These types are most easily identified as a seizure by clinical observation (49).
Myoclonic seizures consist of irregular, erratic rapid twitching or contractions of muscle groups involving the face, limbs, or trunk. They can occur focally or involve all limbs.
Tonic seizures consist of prolonged contraction/posturing in any skeletal muscle group and can be purely focal, or multifocal. This seizure type is typically found with metabolic, vascular, hypoxic ischemic encephalopathy (HIE), and cortical malformations, and seizures of unknown etiology (62).
Motor automatisms are frequent paroxysmal changes in behavior or autonomic functions with minimal motor manifestations. These consist of various irregular and disconjugate ocular movements, eye-opening, chewing, oral-buccal movements, and peculiar extremity movements such as pedaling, stepping, boxing, or swimming movements. Mizrahi and Kellaway found these behaviors to be inconsistently associated with EEG seizure and classify them as nonepileptic. Therefore, it is important to capture these events on EEG before determining if they are epileptic or not.
Epileptic spasms are characterized by sudden flexion or extension of limbs, or both, often occurring in clusters. On EEG, they are associated with a generalized attenuation of the background or a high-voltage slow wave. Spasms are not included in Volpe’s classification scheme.
A systematic review has determined that specific etiologies are associated with a specific clinical seizure type (62). When clonic seizures are present, it is usually associated with a vascular etiology. Sequential seizures followed by tonic seizures were more commonly seen with the genetic etiologies. Additionally, tonic seizures were often seen in sequential seizures regardless of etiology. Tonic seizures were also described in metabolic, vascular, hypoxic ischemic encephalopathy (HIE), and cortical malformations, and seizures of unknown etiology. Sequential seizures followed by myoclonic seizures were often seen in metabolic etiologies.
When EEG monitoring capabilities are limited, the likelihood of a movement being a seizure can be determined based on the clinical semiology (66). A definite seizure (level 1) is confirmed by continuous EEG monitoring (gold standard). A probable seizure (level 2) is defined by a seizure confirmed by aEEG (2a) or a clinically assessed focal clonic or focal tonic seizure witnessed by experienced medical personnel (2b). A possible seizure (level 3) is a seizure suggestive of a neonatal seizure other than focal clonic or focal tonic.
In the neonatal period, a majority of seizures are acute reactive events provoked by severe insults or acute metabolic changes. The etiology of these insults range from vascular, infection, hypoxic ischemic encephalopathy, acute metabolic disturbances, trauma, and neonatal abstinence. Many of these seizures resolve once the underlying etiology is corrected or the acute neurologic disruption of the causal event subsides. The seizures that persist beyond the neonatal period often result from cerebral pathology, such as developmental brain anomalies, or are part of an epilepsy syndrome with or without genetic abnormalities.
Seizures occur more frequently in the neonatal period than at any other time in life (35; 45). In neonates, there is increased neuronal excitability due to an increased receptor expression of glutamate receptors (AMPA, NMDA) with age-specific subunit composition. In the immature brain, potassium tends to accumulate in the extracellular space, secondary to decreased Na+, K-ATPase activity, and immature enzyme systems. This leads to the development of a hyperexcitable state and decreased seizure threshold (90). There is also a delayed development of efficient inhibitory mechanisms (57). It is worth noting that the effects of GABA on chloride conductance change with age. In an immature neuron, there is decreased expression of the chloride pump KCC2. As a result, chloride accumulates in the cell and application of GABA leads to outward chloride movement, which results in depolarization. In the mature cells, GABA application results in hyperpolarization because KCC2 is active. The presence of depolarizing GABA-mediated currents may, on certain occasions, lead to excitatory discharges (07). In animal models, the substantia nigra pars reticularis, which is involved in the control of seizures in adults, has been shown to amplify seizures in immature animals (20).
In the presence of an acute or underlying injury, repeated seizures may lead to a cascade of events such as hypoventilation or apnea, increased blood pressure, and decreased ATP. Hypoventilation may lead to cardiovascular collapse and decreased cerebral blood flow, causing brain damage. Increased blood pressure may lead to increased cerebral blood flow and hemorrhage, also contributing to brain damage. Decreased energy metabolism leads to decreased brain glucose and increased lactate, which harms the brain and is reminiscent of hypoxic-ischemic brain insult. Thus, several factors cooperate in this cascade of events leading to brain injury (97). It is worth noting that the repeated seizures that are the hallmark of the genetic disorder, benign familial neonatal seizures, do not produce brain damage, implying that the underlying cause may contribute to its appearance.
Indeed, the severity of seizures in neonates with perinatal asphyxia has been shown to be independently associated with brain injury and adverse outcome (Miller et al 2002; 22; 79). In response to hypoxemia-ischemia, the preterm brain is most vulnerable in the white matter, whereas a term neonate has gray matter susceptibility (03). MRI and ultrasound studies of preterm neonates with gestational age below 34 weeks identified periventricular hemorrhagic infarct more often in neonates with seizures. Infants with seizures more often showed signs of white matter injury (26). In premature neonates, electrographic seizures tend to occur in relatively sicker and younger infants (80). The presence of neonatal status epilepticus was independently associated with epilepsy later on in life (28). All of the children with epilepsy had injury on neonatal MRI; the majority had injury in the basal ganglia and thalamus, predominantly.
Obvious causes of neonatal seizures are numerous, the most common being hypoxia-ischemia, stroke, trauma, and infections. Other causes include metabolic disorders, malformation of cortical development, drug withdrawal, and toxic exposure. Neonatal seizures may also occur in the setting of benign familial or nonfamilial neonatal epilepsy syndromes from channelopathies, or in more malignant epilepsy syndromes of diverse etiologies.
The prevalence of neonatal seizures is approximately 1.5%, and the overall incidence is approximately 0.5 to 3 per 1000 live births. The incidence in pre-term infants is higher, ranging from 1% to 13% (Berg and Preux 2013). The majority of neonatal seizures occur in the first 1 to 2 days to the first week of life. Most of these epidemiological studies include only clinical seizures, so the exact incidence of electrographic seizures is unknown. A study that looked at preterm seizures found that most seizures in this population are subclinical, have small regions of onset, and do not frequently propagate (39).
Many neonatal seizures result from an external trigger. Causes may include infection, hemorrhage, direct drug effects, metabolic disturbances, or vitamin deficiency or dependency.
The differential diagnosis of neonatal seizures depends on the time of onset of the seizures. If the seizures begin in the first 24 hours of life, the most common causes of seizure are hypoxic-ischemic encephalopathy, hypoglycemia, bacterial meningitis and sepsis, intrauterine infection, direct drug effect, intraventricular hemorrhage at term, subarachnoid hemorrhage, or pyridoxine dependency. With hypoxic-ischemic encephalopathy, the typical onset without cooling is 6 to 8 hours after the hypoxic insult but within the first 24 hours of life. In a group of patients with hypoxic ischemic encephalopathy, the maximum seizure burden was reached within the first 23 hours of life, and the last electrographic seizure was recorded at 55.5 hours of life (46). Over the next 24 to 72 hours, the causes include bacterial meningitis and sepsis, cerebral dysgenesis, cerebral infarction, drug withdrawal, glycine encephalopathy, urea cycle disturbances, hypoparathyroidism, pyridoxine dependency, cerebral contusion and subdural hemorrhage, idiopathic cerebral venous thrombosis, intracerebral hemorrhage, intraventricular hemorrhage in premature newborns, or subarachnoid hemorrhage. Over the next 72 hours to a week, the causes include familial neonatal seizures, cerebral dysgenesis, cerebral infarction, hypoparathyroidism, idiopathic cerebral venous thrombosis, intracerebral hemorrhage, kernicterus, or metabolic disorders. In the next 1 to 4 weeks, that differential includes cerebral dysgenesis, herpes simplex, and metabolic disorders (97; 16). In rare instances, neonatal epilepsy can be the presenting feature of tuberous sclerosis or Sturge-Weber syndrome, though in most cases, onset of seizures is later in infancy (89; 52; 37).
Seizures early in life differ clinically from those of older children and adults because the immature brain is not fully myelinated. The EEG is important to provide clarification of the infant’s movements, as the motor manifestations of seizures in neonates can be subtle and easily misdiagnosed (06; 49; 24). There are several nonepileptic motor phenomena that may be difficult to differentiate from seizures. Tremor, jitteriness, and myoclonus may be benign signs in an otherwise healthy infant, but may also signal a pathological condition. Examples include metabolic disturbance, infection, stroke, drug withdrawal, etc. (36). Benign neonatal sleep myoclonus, mainly during quiet sleep, has normal EEG findings (33). Neonatal hyperekplexia (startle disease) is characterized by muscle rigidity, increased startle reaction, and nocturnal myoclonus and is usually a familial condition that does not have EEG changes (71). Many of the subtle seizures, generalized tonic posturing, and some myoclonic seizures show clinical similarities to reflex behaviors of the neonate; however, the reflexes are not associated with ictal EEG changes.
Neonatal epileptic syndromes are less common and present with different seizure types. In a proposed classification scheme of epilepsies and epileptic syndromes in 1989, neonatal seizures with both focal and generalized fits were listed under epilepsies and syndromes of undetermined type (09). Although the ILAE does not yet have an official classification of syndromes, the following have been often reported:
(1) Benign familial neonatal seizures are based on an autosomal dominant channelopathy (EBN1 from KCNQ2 mutations on 20q13.3, EBN2 from KCNQ3 mutations on 8q24, and SCN2A), with frequent brief seizures within the first days of life. Eighty percent appear on the second or third day of life (44). One third have onset later, up to 3 months of age. This typically occurs in premature infants (54; 74). The diagnosis is suspected when seizures occur without obvious precipitants in an otherwise normal newborn with a family history of similar seizures in the neonatal period. Its diagnosis requires the exclusion of other transient causes for seizures. Prognosis is generally good, with resolution of seizures by 1 to 6 months. There is a normal neurologic outcome in the majority of cases. Even though the seizures may be self-limited, they are typically treated with antiseizure medications because of their frequency.
(2) Benign neonatal seizures (nonfamilial) are characterized by a single episode of repetitive clonic seizures, mainly unilateral, often of alternating sides in a full-term, previous healthy neonate; all investigations, except EEG, are normal (64). Because of the tendency of the seizures to occur on the fourth or fifth day of life, the term “fifth day fits” has also commonly been used. Plouin proposed the following diagnostic criteria: (i) Apgar score greater than 7 at 1 minute, (ii) typical interval between birth and seizures onset (4 to 6 days), (iii) normal neurologic examination before seizures and interictally, (iv) normal laboratory findings (metabolic studies, neuroimaging, and CSF analysis), and (v) no family history of neonatal seizures or postneonatal epilepsy (70). This syndrome may be rare.
(3) Early myoclonic encephalopathy is clinically characterized by erratic or massive myoclonus, partial seizures, tonic spasms, and a suppression-burst pattern on EEG. It is believed to have various prenatal etiologies that often remain unknown; inborn errors of metabolism and genetic disorders are sometimes found. The prognosis is poor.
(4) Ohtahara syndrome (early-infantile epileptic encephalopathy) has a suppression-burst pattern on EEG and poor prognosis similar to neonatal early myoclonic encephalopathy. However, the predominant seizure types are tonic spasms. The etiology is symptomatic, with the majority of cases associated with structural brain damage, but cases due to genetic mutation and metabolic abnormalities have been described. SCN2A is a genetic cause of Ohtahara, in addition to mutations in ARX, STXBP1, CDKL5, KCNQ2, and BRAT1, as well as others (59; 75). There is a suggestion that early myoclonic encephalopathy and Ohtahara may present a continuum of disorders (15).
(5) KCNQ2 encephalopathy is another neonatal epileptic encephalopathy. Seizures typically begin around the first week of life and have a certain electroclinical phenotype. Early recognition of the phenotype can lead to targeted diagnostic testing and early initiation of appropriate treatment. Sodium channel agents, such as carbamazepine, are thought to be first-line therapy in these patients (67). The EEG may reveal a burst suppression or a multifocal pattern (87; 58). The clinical semiology may be focal tonic seizures (61). The seizures of KCNQ2 encephalopathy typically resolve around 3 years of age, but the child typically has severe neurologic impairment.
(6) Vitamin-responsive seizures. Pyridoxine-dependent epilepsy is a rare autosomal recessive disease characterized by a therapeutic response to pyridoxine that is due to a mutation in the ALDH7A1 (antiquitin) gene (10). The diagnosis is determined by intravenously administering a 100 mg therapeutic trial of pyridoxine (maximum of 500 mg) followed by 30mg/kg of either oral or intravenous pyridoxine over 3 consecutive days (maximum daily dose is 200 to 500mg) (69). Pyridoxine-dependent epilepsy requires life-long pyridoxine supplementation in pharmacological doses (15 mg/kg/day). Pyridoxal-phosphate responsive epilepsy, an autosomal recessive disorder due to pyridoxal-5'-phosphate oxidase (PNPO) deficiency, responds to oral treatment with pyridoxal phosphate.
Biotinidase deficiency is a rare autosomal recessively inherited disorder affecting the recycling of biotin, an essential B vitamin. It may present with intractable seizures in infants and young children. Biotin plasma levels can be measured and, if low, treated with daily supplementation of biotin (5 to 20 mg/day).
Folinic acid–responsive epilepsy is a rare inherited syndrome typically manifested in the neonatal period with intractable seizures that are refractory to antiseizure treatment (92). It is caused by pathogenic mutations of the ALDH7A1 (antiquitin) gene, which results in alpha-aminoadipic semialdehyde (alpha-AASA) dehydrogenase deficiency (21). Neonates with this condition usually respond to folinic acid (5 or 10 mg daily) within 24 to 48 hours.
Glucose transporter-1 (GLUT1) deficiency is due to a deficiency usually caused by sporadic mutations in the SLC2A1 gene. It can also be inherited as an autosomal dominant disorder (65). GLUT1 deficiency usually results in a severe metabolic epileptic encephalopathy associated with seizures, hypoglycorrhachia and low lactate concentration without hypoglycemia (12). The diagnosis is suggested on clinical ground and the finding of a CSF:blood glucose ratio of less than 0.4 unit and by genetic testing.
Glycine encephalopathy (neonatal nonketotic hyperglycinemia) usually presents with seizures on the second or third day of life. The EEG demonstrates unusual periodic discharges on a near silent background (77). Treatment is with experimental dextromethorphan (5 to 20 mg/kg/day), Na-benzoate (250 to 750 mg/kg/day), aiming to normalize plasma glycine levels with plasma benzoate.
Family history, pre- and perinatal history, thorough physical examination, and biochemical tests (blood glucose, calcium, urine/blood, CSF cultures, etc.) are standard clinical steps in the evaluation process when neonatal seizures are suspected. In refractory cases, trials with vitamin B6 (pyridoxine), pyridoxal-5 phosphate, and folinic acid may result in seizure resolution if there is an inborn error in metabolism. Additionally, glucose transporter-1 (GLUT1) deficiency, as well as biotinidase deficiency, should be considered in any neonate with poorly controlled seizures. Genetic testing may also be done to further evaluate the etiology. The emergence of new panels has made this easier. Two studies demonstrated a high diagnostic yield in genetic investigations in newly diagnosed early-life epilepsies (05; 86).
The preferred setup for conventional EEG is a polygraphic recording where brain activity; ocular, respiratory, and muscle movements; and ECG are recorded. Continuous EEG monitoring is the gold standard for accurate neonatal seizure detection (82). About 60% to 70% of neonatal seizures are subclinical and will not be recognized without continuous EEG monitoring (06). Electrographic seizures are common and have been identified in nearly half of neonates with hypoxic-ischemic encephalopathy during hypothermia treatment (24). A study found that neonates who underwent continuous EEG monitoring for suspicious clinical events had a seizure captured in nearly all the neonates within 24 hours (101). However, neonates with other high-risk conditions or acute neonatal encephalopathy required a longer duration of monitoring. Another study found that within the first hour of continuous EEG monitoring, a severely abnormal background resulted in a seven-fold increased risk of developing seizures, whereas an abnormal background resulted in a 2.4 times increased risk of seizure during subsequent monitoring (48). Rennie looked at hypoxic-ischemic encephalopathy patients with a high seizure burden and a median maximum hourly seizure burden of 21 min/hour (73). The study found that 19% of infants with no EEG seizures received antiseizure medication, whereas the same percentage with electrographic seizures on EEG seizures did not. Of the 35% with confirmed seizures on cEEG, seizures were generally seen within 6 hours, but only 11% (24/221 seizure episodes) were treated within 60 minutes.
Ictal EEG patterns vary, and may do so even in the same neonate and in the same EEG. The EEG shows repetitive waves with varying frequency and morphology. Focal EEG ictal discharges are usually associated with subtle, clonic, or tonic seizures. The most common locations are centrotemporal, midline, and temporal. The background EEG may be normal or abnormal. Disturbances of background activity in neonatal seizures mainly apply to term neonates and often consist of amplitude depression (general or focal) and/or slowing of the activity (general or focal), a hyperactive background, and spontaneous burst suppression pattern. An abnormal EEG background (particularly suppression or an attenuated EEG background) may be predictive of unfavorable developmental outcome (02; 50).
Particularly in the setting of hypoxic-ischemic encephalopathy, amplitude-integrated EEG is being increasingly adopted by neonatologists to complement conventional EEG in monitoring the status of term neonates (83). Its main utility is in rapid bedside identification of normal and abnormal background patterns that predict favorable or adverse outcomes (88). As a seizure-detection tool, it is limited by its low sensitivity (due to limited channels used and time-compressed tracings that filter out short, low-frequency seizures). However, published studies report good specificity (78; 19). A study found that low amplitudes on aEEG (less than 10uV2) during the first hour of recording were associated with a 90% risk of subsequent seizures (38).
Neuroimaging is essential in order to detect hemorrhage, infarction, abnormalities of cortical development, and other structural pathology. In preterm infants with clinical suspicion of seizures, the MRI seems better at characterizing abnormalities compared to ultrasound (25) and should be performed in all infants presenting with EEG or a-EEG confirmed seizures (99). Ultrasound, CT, and MRI are performed to evaluate maturation and detect cortical abnormalities. MR angiography and venography should be done if a vascular cause is suspected. MR spectroscopy can help diagnose an inborn error of metabolism. Cerebral oximetry, with the use of near infrared spectroscopy, records regional saturation of the brain and may also be used for neuromonitoring in neonates with seizures (91).
In order to initiate treatment, it is important to accurately recognize seizures in the newborn infant and, thus, avoid misdiagnosis (Scher 2002; 49). The next step is to search for an etiologic diagnosis and start treatment accordingly (ie, metabolic disturbance, infection, cardiovascular problem, and other found abnormalities need to be corrected and treated). The current practice is to treat highly suspicious clinical behavior as seizures with antiseizure medications even without initial EEG confirmation. A prospective study looking at 534 neonates with acute symptomatic seizures found that 66% had an incomplete response to the initial loading dose of the given antiseizure medication, especially those with intracranial hemorrhage (30).
Treatment with various antiseizure medications varies in different parts of the world. A retrospective study of 119 infants found that neonatal seizure and etiology negatively affected neurodevelopmental outcomes instead of the choice of antiseizure medication (23). Phenobarbital has often been the first drug of choice (103; 13). The usual loading dose is 20 mg/kg IV, with initial maintenance doses of 3 to 4 mg/kg/day in 2 divided doses. Apparent half-life after 5 to 7 days is 100 hours. Titration of the dose to achieve levels of up to 40 mcg/ml may be necessary in refractory cases. Comparing phenobarbital and phenytoin efficacy in 59 neonates with seizures, 43% of children assigned to phenobarbital as the first drug showed complete seizure control (63). Those first treated with phenytoin showed 45% seizure suppression. Comparing phenobarbital and phenytoin efficacy in 59 neonates with seizures, 43% of children assigned to phenobarbital as the first drug showed complete seizure control. Those first treated with phenytoin showed 45% seizure suppression. Dizon demonstrated the variation in practice for antiseizure medication use (1658 neonates > 36 weeks, 34 ICUs) in patients with hypoxic-ischemic encephalopathy, particularly in patients without electrographic seizures (26%) (14). The study noted that the median cost for antiseizure drug per patient was $89.90.
When phenytoin or phenobarbital was added as a second drug, seizure control increased to 57% and 62%, respectively (63). The phenytoin precursor, fosphenytoin, may be an alternative to phenytoin due to reduced irritation at the injection site as well as lowered incidence of cardiac arrhythmias. A loading dose of 15 to 20 mg PE/kg IV is recommended, with subsequent maintenance doses of 4 to 8 mg PE/kg/day in 2 to 3 divided doses. Average therapeutic range is 10 to 20 mcg/ml. If seizures still persist after administration of optimal dosages of phenobarbital and phenytoin, second-line drugs such as benzodiazepines are usually added. A prospective cohort found that in patients with acute symptomatic seizures, 66% of patients had an incomplete response to the initial loading dose of the specific antiseizure medication that was unrelated to gestational age, sex, medication, or dose (30).
A multicenter, randomized, blinded, controlled trial comparing phenobarbital to levetiracetam found that phenobarbital was more effective than levetiracetam in the treatment of neonatal seizures (81). In this study, 80% of patients randomly assigned to phenobarbital achieved seizure freedom for 24 hours compared to 28% of the levetiracetam group.
Midazolam is a short-acting benzodiazepine suitable for titration in the neonate, with a half-life below 1 hour. Lidocaine is also used for therapy-resistant seizures in neonates (102). As with all drugs administered to neonates, especially premature infants, precaution should be taken to minimize adverse effects. When the neonate has become clinically seizure free and is without electrographic seizure activity, anticonvulsant therapy is withdrawn within a few weeks depending on etiology.
As a consequence of the limited efficacy of many current neonatal antiseizure medications, off-label medications are sometimes used. Topiramate has also been assessed because of its presumed neuroprotective efficacy in animal models of hypoxic-ischemic injury (51). In a small retrospective cohort study of clinical topiramate use in newborns with acute seizures that were refractory to current agents, Glass and colleagues reported reduced occurrence or complete seizure suppression in 4 of 6 infants. Carbamazepine has been found to be safe and effective in neonates with benign familial neonatal epilepsy (76) and in KCNQ2 encephalopathy (67).
Therapeutic hypothermia, in the form of whole body cooling or head cooling, has become the standard of care for term and near-term neonates with hypoxic ischemic encephalopathy. Besides improving developmental outcomes, it has been shown to lower the seizure burden during cooling in hypoxic ischemic encephalopathy (34). When assessing EEG abnormalities and MRI findings in infants with hypoxic ischemic encephalopathy, the infants who received whole body cooling had less prevalent abnormalities on imaging and EEG than the selective head cooling infants (32).
There are no specific guidelines as to when to continue the antiseizure medication. In a survey, antiseizure medications were continued at the time of hospital discharge for 73% of patients with acute reactive seizures; 78% of those with ischemic infarct were discharged home on medication compared to 57% with hypoxic ischemic encephalopathy (85). One study found that the duration of phenobarbital treatment did not prevent postneonatal epilepsy, and seizures after hospital discharge were rare in neonates with acute symptomatic seizures; therefore, early discontinuation of medication was recommended (18; 60). However, in another study that assessed current practice, the majority of the neonates were discharged home on medication; some sites discontinued antiseizure medications in most or all neonates with acute symptomatic seizures prior to discharge (86).
It is important to identify the etiology in order to direct treatment of the seizures and determine prognosis. Seizures persisting despite anticonvulsant treatment in children receiving 2 or more antiseizure drugs were highly prognostic for poor outcome. Treatment failure with 3 or 4 antiseizure drugs, as opposed to 2 antiseizure drugs, increased the risk of poor outcome (47; 93). Electrographic seizures and mortality were greater in preterm infants compared to term infants (29).
Elissa G Yozawitz MD
Dr. Yozawitz of the Albert Einstein College of Medicine has no relevant financial relationships to disclose.See Profile
Emma Laureta MD
Dr. Laureta of Hofstra North Shore-LIJ School of Medicine has no relevant financial relationships to disclose.See Profile
Solomon L Moshé MD
Dr. Moshé of Albert Einstein College of Medicine has no relevant financial relationships to disclose.See Profile
Jerome Engel Jr MD PhD
Dr. Engel of the David Geffen School of Medicine at the University of California, Los Angeles, received honorariums from Cerebel for advisory committee membership.See Profile
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