Neurology -- Correspondence for Augustijn et al., 57 (6) 1108-1111

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Correspondence published:

Reply to Serrano-Castro: P B Augustijn, "J Parra, C Wouters, P Joosten, D Lindhout, W van Emde Boas" (16 October 2001)

Expanding heterogeneity of seizure pattern in ring chromosome 20 syndrome: Pedro Jesus Serrano-Castro (16 October 2001)

Reply to Serrano-Castro 16 October 2001

P B Augustijn,
MD
"Meer en Bosch" and "De Cruquiushoeve" Stichting Epilepsie Instellingen Nederland, Heemstede, Nether,
"J Parra, C Wouters, P Joosten, D Lindhout, W van Emde Boas"
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Re: Reply to Serrano-Castro

paugustijn{at}sein.nl P B Augustijn, et al.

We would like to thank our Spanish colleague for his interest in our article(1), When our article was in press we became aware of his report on a case of a 40-year-old woman with r(20) and epilepsy including a review of the literature(2). Since his report did not address the ictal electroclinical findings which was part of the focus of our report, we did not consider adding its reference in our proofs.
Contrary to the statement made by Dr. Serrano Castro, our findings suggest a rather homogeneous electroclinical picture, which was observed rather consistently through several continuous video EEGs, with periods of NCSE and overall nocturnal seizures, mostly very subtle. Such detailed video-EEG reports were almost non-existent until our article was published. Furthermore, the young age at which our patients were diagnosed and investigated may have indicated a more homogeneous picture of the syndrome, assuming that the expression patterns may not only depend on the degree of mosaicism or breakpoints-fusion points of the ring chromosome but also may be age-related. As also mentioned by Serrano- Castro, it was interesting to see the apparently circadian rhythm in the distribution of the NCSE and seizures that may indicate involvement of MRC3 gene. We have also checked the melatonin curve in two patients and it came up normal (3). Further investigations are underway.
The purpose of our article was to describe these electroclinical findings that we consider highly suggestive for the diagnosis of this syndrome in children. Obviously, our description of the seizure semiology and the presence of nocturnal seizures made us think that the disorder could be related to the genes located in chromosome 20 responsible of ADFLNE. However, since the chromosomal rearrangement may affect the structure or function of more than a single gene, we have to take into account that the clinical phenotype, through interacting mechanisms, may be different from that of the single genes involved. Further molecular genetic analysis of the ring chromosome will eventually help us to resolve the question of how to related the phenotype with the genotype and to determine the role of currently known epilepsy genes and genes yet to be identified.
References: 1. Augustijn PB, Parra J, Wouters, Joosten P, Lindhout D, van Emde Boas W. Ring chromosome 20 epilepsy syndrome in children: Electroclinical features. Neurology 2001;57:1108-1111.
2. Serrano-Castro PJ, Aguilar-Castillo MJ, Olivares-Romero J et al: Cromosoma 20 en anillo. �Una canalopat�a epil�ptica?. Rev Neurol 2001;32:237-241
3. Augustijn PB, Parra J, Dekker E, Smits M, van Emde Boas W. Melatonin in the Ring chromosome 20 epilepsy syndrome Epilepsia 2000;41(Suppl):163

Expanding heterogeneity of seizure pattern in ring chromosome 20 syndrome 16 October 2001

Pedro Jesus Serrano-Castro,
neurologist
Neurology Section. Hospital Torrecardenas
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Re: Expanding heterogeneity of seizure pattern in ring chromosome 20 syndrome

pserrano{at}meditex.es Pedro Jesus Serrano-Castro

We have read the article by Augustijn et al [1]. The authors describe subtle frontal nocturnal seizures (SNS) as an additional clinical feature of the ring 20 syndrome (r20) and suggest that this syndrome is similar to other epilepsy syndrome phenotypes that involve chromosome 20, especially the Autosomal Dominant Frontal Lobe Nocturne Epilesy (ADFNE). We recently reported a new case of r20 [2] and revised the electroclinical pattern of the 31 cases previously published. We conclude that the main clinical feature in these patients was the semiologic variability of seizure pattern seen in not only non convulsive status epilepticus (NCSE) in 20/32 patients but also tonic-clonic seizures (16/32 patients), simple and complex partial seizures (10/32), and absence-like seizures (8/32). In 3/32 patients the authors reported nocturnal seizures. According to Augustijn et al, the seizure pattern of this syndrome is broadening. We think this semiologic variability is the most essential feature. Since clinical postulates there are several reasons to think that r20 is unrelated to a structural or functional defect in the nicotin acetilcholin receptor (nAChR) gene. Contrary to ADFLNE, r20 is refractory to treatment with carbamazepine. The high experimental inhibitory potential of this drug over the nAChR is already known. In addition, the clinical pattern of ADFLNE is phenotypically persistent whatever the subyacent mutation and is different from the r20 phenotype. It is likely that both syndromes have the same genetic base and the absence of microdeletions in the CHRNA4 gene is expected. It is also likely that r20 is not genetically related to ADFLNE. The author�s reported existence of a circadian rhythm in the seizure pattern is similar to our findings. Our patient suffered NCSE most evenings approximately at the same tima but there were no morning seizures. We think that the genetic analysis of MC3R gene will be significant to the understanding of the physiopathology of this epileptic syndrome.
1. Augustijn, PB, Parra, J, Wouters, CH, Joosten P, Lindhout, van Emde Boas W. Ring chromosome 20 epilepsy syndrome in children: Electroclinical Features. Neurology 2001;57:1108�1111. 2. Serrano-Castro, PJ, Aguilar-Castillo, MJ, Olivares-Romero, J et al. Cromosoma 20 en anillo. �Una canalopat�a epil�ptica?. Rev Neurol 2001; 32 (3): 237-41. http://www.revneurol.com/Web/3203/k030237.pdf