Neonatal Tonic Seizures - Causes, Evaluation, Treatment, and Complications

Introduction:

Neonatal seizures are one of the most commonly encountered neurological conditions requiring emergency care in newborns, that is, from the first four weeks from birth, and are seen mostly in preterm infants. It can be defined as sudden paroxysmal (convulsion), excessive, abnormal alterations in the brain's electrical activity, which causes rhythmic contractions, stiffening of muscles, or non-repetitive contractions involving the upper or lower body. It can be symmetrical or asymmetric. A neonatal tonic seizure is characterized by the stiffening or tightening of muscles. It can be generalized (affecting the whole brain) or focal (part of the brain). Since the neonatal brain is immature and it has different pathophysiology and different electrographic activity. When this condition is encountered, doctors should give rapid diagnosis and treatment to avoid future brain damage.

What Are the Causes of Neonatal Tonic Seizures?

Neonatal tonic seizures can be caused due to the following reasons -

• Premature or low birth weight.

• Loss of oxygen during birth, prolonged labor, placental abruption, or umbilical cord compression.

• Drug withdrawal (mothers addicted to alcohol, heroin, or cocaine).

• Blood clots in the brain.

• Familial neurological seizures called fifth-day convulsions.

• Brain injury or tumor.

• Metabolic errors like urea cycle defects, amino acid disorder, organic acidemias, peroxisomal disorder, hypoglycemia, hypocalcemia, hypomagnesemia, and hypo or hypernatremia.

• Intrauterine infection due to cytomegalovirus, toxoplasmosis, varicella, or zika virus.

• Vitamin and cofactor deficiency like vitamin B6 (pyroxidine) and molybdenum cofactor.

• Thromboembolic, which includes arterial ischemic stroke and sinus venous thrombosis.

• Low oxygen conditions like hypoxic-ischemic encephalopathy (occurs 12 to 24 hours after birth) and perinatal asphyxia.

• Intracranial hemorrhage, which can be intraventricular, intraparenchymal, subarachnoid, or subdural.

• Congenital brain malformation like schizencephaly (developmental birth defect with abnormal clefts in the cerebral hemisphere of the brain), lissencephaly (brain malformation, characterized by absence of folds in the cerebral cortex), holoprosencephaly (failure to divide the embryonic forebrain into hemispheres), and hydranencephaly (a condition where cerebral hemispheres are absent and are replaced with cerebrospinal fluid-filled sacs).

• Neonatal epilepsy syndromes like a benign neonatal seizures, genetic epilepsy syndrome, early infantile encephalopathy, and benign familial neonatal epilepsy.

• Infections such as bacterial meningitis and viral encephalitis.

What Are the Clinical features Of Neonatal Tonic Seizures?

The following characterize clinical features of neonatal tonic seizures -

• Continuous stiffening of muscles.

• Horizontal eye deviation.

• Keeping head or eye to one side.

• Asymmetric neck posture.

• If generalized, it can cause upper and lower body extension or upper body flexion and lower extension.

What Are the Clinical Features of Other Types of Seizures?

Clinical features of other types of seizures are:

1. Subtle Seizure -

• Random eye movements like rolling, fluttering, or staring.

• Sucking.

• Chewing.

• Protruding tongue.

• Bicycling movement.

• Apnea.

2. Focal Clonic Seizure -

• Repetitive, rhythmic jerking contractions, including upper/lower body, neck, or trunk.

3. Myoclonic Seizures -

• Nonrepetitive contractions involving the upper extremity commonly.

• If generalized, it causes bilateral jerking.

4. Tonic-Clonic Seizures -

• Stiffening and then jerking of extremities.

5. Status Epilepticus -

• A seizure for more than 30 seconds. This requires immediate emergency care. It is life-threatening.

What Is The Pathophysiology Of Neonatal Tonic Seizures?

The neonatal brain is unique and immature, and any pathology can cause seizures. Since it is immature, there is an imbalance between neuronal discharge excitation and inhibition, which can affect the development of the brain. Seizures are due to abnormal neuronal discharge, which is repetitive and synchronized. A mature brain has GABA (gamma-aminobutyric acid) receptors, which have a synaptic potential (which makes a postsynaptic neuron less likely to generate action potential) by establishing decreased cellular membrane potential by chloride and potassium channels. In contrast, there is increased cellular membrane potential in the neonatal brain, GABA receptors are stimulated and calcium channels open, and depolarization of neurons occurs, which causes the increased electrical activity of the brain, causing abnormal movements of the upper and lower body.

How Are Neonatal Tonic Seizures Examined And Evaluated?

Neonatal tonic seizures are diagnosed through the following methods -

• A thorough history and physical examination should be carried out.

• History should contain

1. The onset of a seizure.

2. Maternal history of genetics (miscarriages, gestational diabetes, infections such as the sexually transmitted or maternal-fetal transmission of infection, prenatal exposure to drugs, inherited thrombophilias, or bleeding disorder).

3. Birth history (anoxic or lack of oxygen in the brain resulting in brain injury).

4. Family history (early sibling death or history of epilepsy).

• Physical examination includes checking vital signs, head circumference, mental status (level of alertness), quality of fontanelle, and checking for acute intracranial hemorrhage.

• If the neonate's body is stable, doctors should conduct neurological examinations on cranial nerves and structural brain lesions.

• Doctors should conduct an electrolyte panel to exclude the possibility of metabolic abnormalities.

• Complete blood count, C-reactive protein, blood cultures, and cerebrospinal fluid or CSF findings (lumbar puncture) should be done to rule out sepsis, meningitis, or encephalitis.

• Other diagnosis studies include computed tomography (CT) scan, ultrasound, magnetic resonance imaging (MRI) of the brain, meconium analysis, electroencephalography (EEG), and chromosomal studies to rule out genetic disorders.

What Is the Treatment for Neonatal Tonic Seizures?

The treatment for neonatal tonic seizures should include the following -

• Keeping patients away from hard objects and rolling to the side to prevent choking.

• The caregivers should try to stop mouth movements.

• A patent airway should be maintained.

• Continuous EEG monitoring should be done.

• Therapeutic hypothermia should be done for hypoxic-ischemic encephalopathy.

• Antibiotics should be given for sepsis or meningitis.

• Dextrose should be given in case of a severe hypoglycemic condition.

• Correction of electrolytic abnormalities and metabolic derangements should be done.

• Neurological surgery if any intracranial hemorrhage is observed.

• Medications such as Phenobarbitol, Fosphenytoin, Levetiracetam, Lidocaine, or short-acting Benzodiazepines should be given.

What Are the Complications of Neonatal Tonic Seizures?

Prolonged and untreated seizures can cause decreased oxygen levels and can cause permanent damage to the brain. They can cause loss of airway (hypoxemia). Because of these, there can be cerebral palsy, mental retardation, feeding difficulties, cardiac arrest, and myocardial depression. In addition, antiepileptic medications can cause hepatic and renal dysfunction.

What are the Differential Diagnosis of neonatal tonic seizures?

Identifying seizures is difficult in neonates. It can be sucking movements, hiccupping, neonatal sleep myoclonus (sudden movement or jerking of muscle), apnea, infantile spasms, or motor automatisms (involuntary activity).

What Is the Prognosis of Neonatal Tonic Seizure?

The prognosis depends on the etiology, and if electroencephalography (EEG) is normal, the prognosis is good, and if EEG has spikes, there is a 30 percent risk of developing future epilepsy. The mortality rate is up to 20 percent.

Conclusion:

Neonatal epilepsy is a serious emergency and should be treated rapidly. Diagnosis and management require a professional approach, but half of them may have epilepsies in the future. Therefore, parents should be counseled on the symptoms, use of antiepileptic medications, prognosis, and possibilities of impairments. In addition, children with seizures should have routine clinical follow-ups.