Updated: Apr 8, 2009
Benign neonatal convulsions are defined as seizures with onset after birth through day 28 in an otherwise healthy child with no other known medical or neurological problems. Such cases may be familial or isolated. Psychomotor development should be normal for a full-term or near full-term infant with benign convulsions. Between seizures, findings on neurologic examination should be normal. Clinically, the seizures are frequent and brief, occasionally occurring many times within a day. The brief seizures are followed by a short or no postictal state. The episodes usually resolve within days but may continue for several months and have no neurological sequelae.
The occurrence of status epilepticus is common in benign idiopathic neonatal convulsions (BINC) but is uncommon in benign familial neonatal convulsions (BFNC). Because benign idiopathic neonatal convulsions is a diagnosis of exclusion, it is nearly always made in retrospect, when the seizures spontaneously resolve and the infant is found to have neurologically normal development.1,2,3,4
At the outset, considering how broadly to define benign neonatal convulsions is important: for example, whether to include those with myoclonic or partial onset components or those with a known or treatable etiology. Certainly, multiple presentations of seizures that may have a benign long-term outcome are possible in the neonatal period.3,7 Definite advantages exist in approaching the subject from each position. Too broad of a definition in a research situation can lead to confusion when searching for a common pathology. Too narrow of a definition in the clinical setting may result in confusion about a clinical diagnosis. Later, when the mechanisms are more well defined, broader groups not meeting the initial criteria may exist.
Clinically, the more important considerations are taking an appropriate approach to the patient and family, making the correct diagnosis, and pursuing treatment options concordant with the situation. Sometimes, the correct clinical plan may include a decision not to treat a benign condition with medications that often are not so benign. It should also be emphasized that a definitive diagnosis may take some time, given the often retrospective nature of the diagnosis.
For the purposes of this article, myoclonic and partial onset seizures of the neonatal period are considered separate entities. They are mentioned briefly during the discussion on differential diagnosis.The genetics of benign familial neonatal convulsions is currently an area of active investigation. Inheritance is autosomal dominant. Loci on chromosome arm 20q have been identified for most families. At least one family was identified to have a locus on chromosome arm 8q. Some of these loci have been identified further as specific mutations in the KCNQ2 and KCNQ3 M-type potassium channel proteins.8,9,10,11,12,36,37,38 The specific location of the mutation appears to vary from family to family and at least 1 family has been noted to include an increased incidence of rolandic epilepsy.5
Several additional genes have been associated with benign familial neonatal convulsions in single families, including KCNQ5 M-type potassium channel in one family.13 Another family has been noted to have abnormalities in the acetylcholine alpha-4 receptor subunit, which also has been associated with autosomal dominant nocturnal frontal lobe epilepsy.14,15
Expression of the mutated genes in xenopus oocytes has provided some insight into how the potassium channel mutation leads to lowering of the seizure threshold. The potassium current was reduced in the channel expressed by the mutated gene to 5% of that in the channel expressed by the normal gene. However, voltage sensitivity and kinetics were not affected. The effect is therefore to impair repolarization of the neuronal cell membrane, leading to hyperexcitability of the central nervous system.16,17
Given the severity of the impairment to the M-type potassium channel, that these seizures are difficult to treat is not surprising, since no currently used antiepileptic medications are known to increase the efficiency of the potassium channel. What is surprising is the self-remitting nature of the condition, that many individuals never have another seizure, and that the profound abnormalities of the voltage-gated potassium channel do not appear to compromise the nervous system in any other way. Possibly, some intrinsic method exists for up-regulating expression of the normal potassium channel genes, or the neurons may find other ways of normalizing the hyperexcitability, but these theories remain to be demonstrated.18,19,20
A number of cases have been reported where benign idiopathic or familial neonatal convulsions have preceded the development of epilepsy later in life. Similarly, perhaps, febrile seizures early in life may predispose to later development of epilepsy. Given the polygenic etiology of susceptibility to epilepsy, it is not surprising that an abnormality in part of the system maintaining homeostasis within the neuron should render the neuron more prone to dysfunction.21,22,23,24
A complicating factor is that in neonates the action of the GABA-A receptor is excitatory rather than inhibitory in the brain.25,26,27,28
The pathophysiology of BINC has been less well defined and remains somewhat elusive. One issue is that the neonatal brain is more prone to seizures, which has been demonstrated in a number of experimental systems.25,26,27,28
Several etiologies have been proposed as a result of isolated findings of lowered zinc level in the cerebrospinal fluid and low levels of vitamin B-6.29 Both of these compounds are important cofactors in ligand-gated ion channel function. However, these findings have not been robust, and the search continues. These seizures are likely also linked in some way to ion channel dysfunction as is found in the familial seizures, but they may be caused by multiple etiologies or occur as a multigenomic entity.30,31,32 These sorts of multifactorial etiologies are more difficult to define precisely. More research is needed in this area, and apparent monogenic diseases, such as benign familial neonatal convulsions, provide important insight into more complex etiologies.
Benign neonatal convulsions in the United States are uncommon, ie, not rare but not common, either. Underreporting is likely an issue. Seizures that resolve in the early months of life without sequelae and normal neonatal development are often lost to follow up. Exact frequencies are undetermined. Families identified with the familial form thus far have been primarily of western European origin, although one report from Japan exists.33,34 Part of the reason for this is likely the stability of reporting resources in European countries.
Benign neonatal convulsions also are uncommon internationally. Families identified with the familial form thus far have been primarily of western European or Japanese origin.33,34 This is certainly an artifact of observation rather than occurrence.
The risk of seizures later in life is 11-16% in benign familial neonatal convulsions and somewhat less in benign idiopathic neonatal convulsions, perhaps as low as 2%. Other reported problems have been sporadic and within the incidence range expected for the general population.29
All cases to date have been reported in families of European or Japanese origin.33,34
In benign familial neonatal convulsions, the frequency in males is equal to that in females, compatible with simple autosomal dominant inheritance.29
In benign idiopathic neonatal convulsions, males are affected somewhat more frequently than females (62%) in examined cases (N=199).29 With such a small number of cases reported, this may be due to reporting bias or simple sampling error, or it may represent a real difference in frequency.
Physical and neurologic examination findings should be normal during the interictal period.
| Arteriovenous Malformations | Neonatal Injuries in Child Abuse |
| Aseptic Meningitis | Neonatal Meningitis |
| Epilepsy in Children with Mental
Retardation | Neonatal Seizures |
| Febrile Seizures | Partial Epilepsies |
| Frontal Lobe Epilepsy | Tuberous Sclerosis |
| Infantile Spasm (West Syndrome) | Viral Encephalitis |
Vitamin B-6 deficiency
Maternal drug abuse
Although the seizures are benign, general agreement exists that they should be treated, particularly benign idiopathic neonatal convulsions.
No specific antiepileptic medication is preferred for the treatment of benign neonatal convulsions. In general, most epileptologists agree that status epilepticus should be treated when it occurs. Most neonates are best treated at this time with phenobarbital because of long experience with the drug, convenient monitoring, and adequate IV and PO absorption in the neonate. However, treatment has not been shown unequivocally to have an effect except possibly to decrease the duration or severity of the seizures. By definition, the seizures resolve in days (benign idiopathic neonatal convulsions) to weeks (benign familial neonatal convulsions).
Limit the choice of antiepileptic drug to those with no serious potential adverse effects. Most notably, avoid valproate in this age group if benign convulsions are suspected, since neonates are at the highest risk for liver failure due to valproate. Avoid phenytoin because of cardiac adverse effects, the high possibility of extravasation in neonates, and problems with reliable absorption if administered PO. A trial off the antiepileptic drug(s) should begin soon after the seizures stop and the EEG is normal.
An important factor to remember when treating neonates is that pharmacokinetics and pharmacodynamics are very different than in infants. Do not use infant loading dosages, since they may lead quickly to toxic levels that resolve slowly.
Neonatal pharmacology is complex. Maturation of general liver and renal function is in a period of transition from the fetal to infant state. Stresses or lack of stress on the systems in utero greatly affect the function and maturation of both systems.
Normal glomerular filtration rate (GFR) in the neonate varies in individuals from 1-4 mL/min and can increase rapidly as maturation of the renal cortex progresses. Adult values for GFR are not reached before the infant is aged 2.5-5 months.
Blood flow within the hepatic portal system changes at birth with closing of the ductus venosus. Maturation of the glucuronidation pathway often is slowed. Neonates whose mothers have been exposed to drugs (both prescribed and otherwise) may have active cytochrome P-450 enzymes, and unexposed neonates have initial low activities that usually increase rapidly with the introduction of drugs such as phenobarbital.
These agents prevent seizure recurrence and terminate clinical and electrical seizure activity.
DOC for treatment of neonatal seizures. Use care in dosing since toxicity can occur quickly and resolve slowly. Also doses that are initially adequate may need to be increased quickly as cytochrome P-450 becomes more active.
20 mg/kg loading dose IV and 5 mg/kg/day maintenance dosing; take care when administering to neonates whose drug biotransformation and excretion may be reduced at birth due to immaturity of glucuronidation pathway, cytochrome P-450 system, and reduced GFRs
May decrease effects of chloramphenicol, digitoxin, corticosteroids, carbamazepine, theophylline, verapamil, metronidazole, and anticoagulants (patients stabilized on anticoagulants may require dosage adjustments if added to or withdrawn from their regimen); alcohol may produce additive CNS effects and death; chloramphenicol, valproic acid, and MAOIs may increase toxicity; rifampin may decrease effects
Documented hypersensitivity; severe respiratory disease; marked impairment of liver function; nephritis
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
In prolonged therapy, evaluate hematopoietic, renal, hepatic, and other organ systems; caution in fever, hyperthyroidism, diabetes mellitus, and severe anemia since adverse reactions can occur; caution in myasthenia gravis and myxedema
Initially may be used to control status epilepticus in patients with benign neonatal convulsions; however, unsuitable for long-term therapy.
Initial loading dose: 15-20 phenytoin equivalents per kg IV; maintenance should be guided by clinical response and free drug levels and may be as low as 1.5 mg/kg/d in divided doses; in older children, enteral dosing of phenytoin is typically 5 mg/kg/day, or in infants up to 10 mg/kg/day or higher
Amiodarone, benzodiazepines, chloramphenicol, cimetidine, disulfiram, ethanol (acute ingestion), omeprazole, phenacemide, phenylbutazone, succinimides, fluconazole, isoniazid, metronidazole, miconazole, sulfonamides, trimethoprim, and valproic acid may increase toxicity
Barbiturates, carbamazepine, theophylline, diazoxide, ethanol (chronic ingestion), rifampin, antacids, charcoal, and sucralfate may decrease effects
May decrease effects of acetaminophen, corticosteroids, dicumarol, disopyramide, doxycycline, estrogens, haloperidol, amiodarone, carbamazepine, cardiac glycosides, methadone, metyrapone, mexiletine, oral contraceptives, quinidine, theophylline, valproic acid
Documented hypersensitivity; sinoatrial block; second- and third-degree AV block; Adams-Stokes syndrome
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Death from cardiac arrest has occurred after too-rapid IV administration, preceded sometimes by marked QRS widening
Blood dyscrasias have occurred and thus blood counts and urinalyses should be performed when therapy is begun and at monthly intervals for several months thereafter; discontinue use if skin rash appears—if rash is exfoliative, bullous, or purpuric do not resume use; administer cautiously to patients with acute intermittent porphyria; exercise caution when administering to patients with diabetes—may raise blood glucose levels; discontinue drug if hepatic dysfunction occurs
Sulfamate-substituted monosaccharide with broad spectrum of antiepileptic activity that may have state-dependent sodium channel blocking action, potentiates inhibitory activity of neurotransmitter GABA. May block glutamate activity.
Initial starting dose: 1 -3 mg/kg/d PO; increment of 1-3 mg/kg q3-4d
Maintenance dose: up to 9 mg/kg/day though 20 mg/kg/day is used for infantile spasms
Phenytoin, carbamazepine, and valproic acid can significantly decrease topiramate levels; topiramate reduces digoxin and norethindrone levels when administered concomitantly; concomitant use with carbonic anhydrase inhibitors may increase risk of renal stone formation and should be avoided; use topiramate with extreme caution when administering concurrently with CNS depressants since may have an additive effect in CNS depression as well as other cognitive or neuropsychiatric adverse events
Documented hypersensitivity
C - Fetal risk revealed in studies in animals but not established or not studied in humans; may use if benefits outweigh risk to fetus
Risk of developing a kidney stone formation is increased 2-4 times that of untreated population; risk may be reduced by increasing fluid intake; caution in renal or hepatic impairment; patients taking topiramate should seek immediate medical attention if they experience blurred vision or periorbital pain; continued usage after symptoms develop can lead to glaucoma; primary treatment is discontinuation of topiramate; if left untreated, serious sequelae, including permanent vision loss, may occur; oligohidrosis and hyperthermia have been reported predominantly in children during vigorous exercise or exposure to warm environmental temperatures (ensure proper hydration prior and during activity and warm temperatures)
May cause hyperchloremic, nonanion gap metabolic acidosis acute or chronic metabolic acidosis resulting in hyperventilation and nonspecific symptoms, such as fatigue and anorexia, or more severe adverse effects including cardiac arrhythmias or stupor; chronic, untreated metabolic acidosis may increase nephrolithiasis or nephrocalcinosis risk, osteomalacia (ie, rickets in pediatric patients), or osteoporosis with an increased risk for bone fractures; chronic metabolic acidosis in pediatric patients may also reduce growth rates; measure baseline and periodic serum bicarbonate level
Patients with benign familial neonatal convulsions have an increased risk of developing seizures in later life. Depending on the study, 11-20% of patients develop epilepsy in later life. Some families examined also have demonstrated an increased risk of epilepsy in apparently unaffected siblings.
Overall, as the name implies, benign neonatal convulsions have an excellent prognosis and resolve without neurological sequelae.
Other seizure types often are intermixed in families with inherited seizure disorders. This also is observed in families with benign neonatal convulsions. Children (and apparently unaffected siblings) who have benign neonatal convulsions are at an increased risk of seizures in later life.
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benign neonatal convulsions, second day seizures, benign neonatal seizures, benign familial neonatal convulsions, benign idiopathic neonatal convulsions, benign familial neonatal seizures, benign idiopathic neonatal seizures, fifth day disease, fifth day fits, seizure epilepsy treatment, symptoms, BFNC, BINC
Nancy Theresa Rodgers-Neame, MD, Assistant Professor, Department of Molecular Pharmacology and Physiology, University of South Florida; Director, Florida Comprehensive Epilepsy and Seizure Disorders Program
Nancy Theresa Rodgers-Neame, MD is a member of the following medical societies: American Academy of Neurology, American Epilepsy Society, American Medical Women's Association, Society for Neuroscience, Southern Clinical Neurological Society, and Southern Medical Association
Disclosure: Nothing to disclose.
Robert Baumann, MD, Program Director, Professor, Departments of Neurology and Pediatrics, University of Kentucky
Robert Baumann, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, American College of Epidemiology, American Epilepsy Society, and Child Neurology Society
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: Nothing to disclose.
Kenneth J Mack, MD, PhD, Senior Associate Consultant, Department of Child and Adolescent Neurology, Mayo Clinic
Kenneth J Mack, MD, PhD is a member of the following medical societies: American Academy of Neurology, Child Neurology Society, Phi Beta Kappa, and Society for Neuroscience
Disclosure: Nothing to disclose.
Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.
Amy Kao, MD, Assistant Professor, Department of Pediatrics, Division of Pediatric Neurology, Department of Neurology, Oregon Health and Science University; Consulting Staff, Shriners Hospital for Children
Amy Kao, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Pediatrics, American Epilepsy Society, and Child Neurology Society
Disclosure: Nothing to disclose.
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