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Benign Nonfamilial Neonatal Convulsions

The diagnosis of benign nonfamilial neonatal convulsions should be reserved for neonates with characteristics similar to those listed for benign familial convulsions but without a positive family history.

Cryptogenic Neonatal Seizures
Cryptogenic neonatal seizures is a term used for seizures that occur in a neonate with an abnormal neurological examination but with no established cause for the seizures. Many neonates with cryptogenic seizures demonstrate a characteristic EEG pattern that consists of bursts of high-voltage activity followed by periods of attenuation (Otahara syndrome) whereas other demonstrate a nearly continuous multifocal migratory partial seizures (malignant migrating partial seizure of infancy).
The diagnosis of Otahara syndrome is given to neonates with seizures and characteristic EEG pattern of bursts of high-voltage activity followed by periods of attenuation (burst supression pattern). Neonates with Otahara syndrome may have cryptogenic neonatal seizures or seizures with a demonstrable etiology. The possibility of migrational errors or obscure metabolic diseases should be considered in neonates with Otahara syndrome.
The terms migratory partial seizure of infancy or malignant migrating partial seizure of infancy are synonyms. They are used in neonates with criptogenic intractable seizures with initially normal brain imaging studies and an EEG pattern characterized by migratory partial almost continous seizures. No medication, including steroids, has been found to successfully treat this seizures. Bromide was successful in one case.

Cerebellar Seizures

The term cerebellar seizures refers to any clinical paroxysmal event believed or proven to be due to pathological, massive, and repetitive cortical cerebellar neuronal depolarization. Cerebellar seizures are characterized by hemifacial contraction (click on clip), head and eye deviation, nystagmus and autonomic dysfunction; consciousness is usually not affected. They occur with cerebellar tumors.

Facial spasms due to cerebellar seizures may be very subtle. Ipsilateral arm contraction is often present (click on clip).

The patient in the last two clips had tuberous sclerosis and a large cerebellar subependymal giant cell astrocytomas (Figure 57.1).

A
B

Figure 57.1. [A] Sagittal MRI of the brain demonstrating a large posterior fossa tumor (contrast) and dilatation of the third ventricle. [B] Hematoxylin-eosin stain of tumor tissue demonstrating a solid proliferation of large balloon cells with abundant glassy to finely granular or foamy eosinophilic cytoplasm with frequent eccentric uniformly regular nuclei with bland chromatin and a distinct nucleoli. The histology was consistent with a subependymal giant cell astrocytomas.

 

ANTIEPILEPTIC TREATMENT

Antiepileptic drugs and etiological treatment stop seizures by preventing massive repetitive and synchronous neuronal depolarization. During depolarization, the voltage-dependent sodium channels open and sodium enters the cell driven by its concentration (there is more sodium outside the cell than inside the cell) and electrical gradients (there are more negative charges than positive charges adjacent to the inner surface of the membrane). When the inner side of the membrane is flooded with enough positive ions to decrease its normal negativity above the threshold of the voltage-dependent sodium channels, these channels will open. Medications that maintain the inner membrane surface and prevent it from reaching the threshold of the voltage-dependent sodium channel prevent seizures.

 

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Marsh E et al. 2005 Okuda K et al.2000