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The absence of scalp-recorded-electroencephalographic seizures during a paroxysmal motor event excludes a convulsion unless the events consist of paroxysmal giggling and smiling. Paroxysmal giggling and smiling in a neonate may be signs of gelastic epilepsy. Gelastic epilepsy is a rare and peculiar type of convulsion associated with hypothalamic hamartomas in neonates. The clinical manifestations of an event of gelastic epilepsy consist of a burst of hyperpnea, followed by repeated cooing, giggling, and smiling (laughing seizures). Limbs jerks may also be present. The convulsions usually last for 20 to 30 seconds and occur in clusters lasting from 1 to 3 minutes. The convulsions do not interfere with normal neonatal activities and may be present from birth. Scalp electroencephalographic recordings do not demonstrate electroencephalographic seizures during gelastic convulsions. In one patient with gelastic seizures, an ictal single photon emission computed tomography demonstrated increased uptake in the area of the tumor, whereas the interictal single photon emission computed tomography did not.

Pathological Reflexes
Pathological reflexes occur in encephalopathic neonates with significantly depressed EEG background activity (Figure 9.1) or in neonates with hyperexcitability syndrome.
Pathological reflexes in encephalopathic neonates with significantly depressed EEG background activity are also called subcortical release phenomena or brainstem release phenomena. They consist of paroxysmal motor events that show fatiguability, spatial and temporal summation, and variability with positioning, and do not have characteristics of physiologic reflexes nor meet the criteria for benign jitteriness (click on clips, below).

These paroxysmal motor events are characterized by repetitive eye or eyelid movements, pedaling or stepping, jitteriness, rolling arm movements, decorticated and decerebrated postures, and trunk, head writhing, or both (click on clips, below).


They are not associated with concomitant electroencephalographic seizures (Figure 9.1[A]), nor with focal increase in cerebral hemispheric perfusion by single photon emission computed tomography (Figure 9.1[B]).

A B

Figure 9.1 [A] EEG: depressed electroencephalographic background and no electroencephalographic seizure pattern. Clinical: pathological reflex activity characterized by raising both arms while isotope for single photon emission computed tomography is being injected; [B] Single photon emission computed tomography demonstrating no focal increase hemispheric perfusion.

 

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Alfonso,1997 Sher, 1976 DiFazio, 2000 Mizrahi, 1985 Alfonso, 2000 Click on figure to enlarge.