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Neonates with 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
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.

Extrapyramidal movements
Extrapyramidal movements 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.

 

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Alfonso, 2000 Rosman, 1984 Volpe, 2000