Neonatal seizures with tonic clonic sequences and poor developmental outcome
Introduction
Tonic clonic seizures are “a sequence consisting of a tonic followed by a clonic phase” (Blume et al., 2001). Such sequences are commonly seen in children and adults but have been rarely described in neonates. Neither Volpe (2001) nor Mizrahi and Kellaway (1998) include tonic clonic or tonic myoclonic seizures in their neonatal seizure classification. However, tonic clonic sequences have been reported in infants with benign familial neonatal convulsions (BFNC) (Ronen et al., 1993). Similar to other neonatal seizure types, the presentation of tonic clonic or tonic myoclonic sequences differed from those observed in older children. The reason for this difference is most likely related to the immature status of neuroanatomical and neurophysiological development in the neonatal period (Volpe, 2001).
Screening our video archive of 105 neonates with seizures or suspected seizures we identified six patients with tonic clonic or tonic myoclonic sequences. Two of those had known pyridoxine dependent seizures (PDS) but the etiology of the seizures in the remaining four patients was unknown. We analyze the electro-clinical patterns, the clinical course and neurodevelopmental outcome in the two groups of patients and demonstrate a possible genetic relationship between BFNC and the second group through the identification of a formerly unknown ion channel mutation.
Section snippets
Methods and subjects
The patients were selected from all neonates hospitalized in the Intensive Care Units of the University Children's Hospital, Zurich between 1991 and 2004. Most children were outborn and transferred for tertiary level neonatal care. Neonates (age 1–28 days) with suspected seizures underwent one or more EEG examinations, most of them with simultaneous video-recording. One hundred and five neonates were identified as having seizures or suspected seizures during the video-EEG. We reviewed all
Results
We identified seven children with tonic clonic or mixed tonic myoclonic seizure sequences. One child was excluded because the tonic sequence could not be differentiated from movements at awakening.
Discussion
We could identify two types of neonatal seizures with tonic myoclonic or tonic clonic sequences. One type showed mixed seizures with erratic or generalized myoclonic jerks, associated intermittent tonic posturing or spasms, eye deviations and abnormal oral and mimic movements. These seizures were long-lasting (>10 min) and did not coincide with ictal EEG changes. The other seizure type was better structured, started with slowly progressing bilateral tonic posturing of the trunk and limbs
Acknowledgment
We thank Stephanie Stücheli for her detailed neurodevelopmental examination. This work was supported by a grant from the Nationales Genomforschungsnetz 2 (NGFN2) to OKS.
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