pathological reflexes require the same evaluation as neonates with convulsions.
The causes of subcortical release phenomena or brainstem release phenomena
are the same as those that produce seizures. The most frequent cause of
pathological reflexes is hypoxic-ischemic encephalopathy. Pathological
reflexes do not require treatment with antiepileptic drugs. Pathologic
reflexes originate either from a transient cortical dysfunction producing
a release of normally inhibited preprogrammed brainstem activity or an
intrinsic irritability of the brainstem structures. Pathological reflexes
do not originate from electroencephalographic seizures and are not associated
with scalp or nasopharyngeal electroencephalographic seizures.
Pathological reflexes also
occur in neonates with hyperexcitability syndrome. The triad of signs
referred to as hyperexcitability syndrome consists of coarse tremor, brisk
deep tendon reflexes, and a low threshold for Moro reflex. Hyperexcitability
syndrome may be associated with hypermotility and increased resistance
to passive movements of the limbs. Local anesthetic intoxication and withdrawal
from opiates may produce hyperexcitability syndrome.
Startle disease or hyperekplexia
is characterized by a pathological intensification of the startle response.
Startle disease is due to glycine receptor abnormalities in the spine
and brainstem reticular neurons. It is transmitted as an autosomal recessive
trait mapped to chromosome 5. The clinical manifestations of startle disease
are tonic contraction of all four extremities and massive myoclonic jerks
(click on clips, below). Tonic contraction
may be associated with apnea. There are no changes in EEG activity during
the episodes, except for slowing secondary to hypoxia if apnea is prolonged.
Startle may be triggered by tactile stimulation, especially of the face
(specially the nose), or may occur spontaneously. Forced flexion of the
head and legs toward the trunk ends the episode of tonic contraction and
apnea (click on clips, below). Heart rate
initially increases at the onset of the event and then decreases after
a few minutes if a prolonged apnea occurs. Clonazepam may help.
may be seen at 2 to 3 months of age in premature neonates with bronchopulmonary
dysplasia. Extrapyramidal movements are characterized by oral-buccal-lingual,
limb, neck, and trunk repetitive movements. Oral-buccal-lingual movements
often interfere with feeding. Clonazepan may help.