1 0 7 BackgroundandObjec tive:Period ic la te ra lize d e pil ept iform discha rge s (PLEDs) are EEG abn orm a lities consisting of repetitive spike or sharp wave discharges, which are focal or lateralized over one hemisphere and that recur at almost fixed time intervals. When present bilaterally and independently, the y have be en te rme d BIPL EDs. PL EDs ha ve m ost com m onl y be en a ssociate d with cere bra l infarctions but are also seen in other cerebral diseases such as encephalitis, tumour or demyelination. I t stil l rem a ins co ntrove rsia l whe the r PLEDs repre se nt a ctu a l icta l a ctivity, pred ispose to e pil e ptic seizures or are simple indicators of underlying aetiology. 1 -5 Th e o b je ct iv e o f t h is s t u d y w as to investigate the a e tiology of PLEDs an d th e co-existe nce of EEG seizure a ctivity. Methods:A retrosp ect ive re vi e w of EEG rep orts in a te rtiary hosp ita l be twee n 19 98 – 2004 was con du cte d. The EEG rec ordings of rep orts with p e riodic l a te rali se d or l oca lise d e pil e ptiform disch a rge s (PLEDs or BI PL EDs) we re se le cte d a nd a na lyse d. Clinical da ta o f these pa tie nts we re a lso tra ce d spe cifica lly for the res ul ts of i m a gi ng stu di e s (MRI/CT brain), liver/ren al fun ctiontests a ndce reb rospinal fluid (CSF) an a lyse s. EEG seizure s we re d e fined wh e n there were rhyth mic EEG act ivity (PL EDs themselves &/or other concomitant activity) with progression in field, frequency &/or amplitude with or without clinical seizure correlate. Results:Forty-f ive of 7,5 00 pa tien ts (0.6% ) had EEG crite ria fulfilling PL EDs (37 PL EDs; 8 BI PL EDs). T he m ea n a ge was 6 6 yea rs (ran ge , 26- 92), wi th 21 m ales a nd 24 f em ales. The ae tiologie s correspo nding to the PL EDs were ce reb rovascular acci de nt (53%), ce ntral nervous syste m infection (16%), encephalomalacia (7%), tumour (7%), demyelination (2%), metabolic (2%) and idiopathic (13%). Eigh te e n pa tie nts (40 %) had conc om ita nt EEG se izure s, all ips ila te ral to the rec orde d PL EDs. Nine of these patients had cerebrovascular accident (7 ipsilateral, 2 contralateral). Two patients each had central nervous system infection, ipsilateral encephalomalacia/gliosis, ipsilateral tumour, and normal neuroimaging. No neuroimaging was found in 1 patient. Morta lity was e ncounte red in 15 pa tie nts (33% ), 1-50 da ys post-EEG. Eigh t pa tie nts h a d cerebrovascular accident, 3 had central nervous system infection, 2 had tumour, 1 had significant metabolic derangement and the remaining 1 had no discernible aetiology. Only 4 of 18 patients (22%) with con com ita nt EEG se izure s died. Of tho se who d ie d, 73 % ha d PL EDs i n > 75 % of the ir EEG. Mortal ity was a lm ost 50 % am ong th ose with > 75% of PL EDs i n the ir EEG versu s 20 % am ong th ose with < 75 % of PL EDs in th e ir EEG. Discussion and Conclusion: Th e ma jo r it y o f our p atien t s w it h PLEDs had cereb r ovascular disease in the same reg ion. Concomitant EEG seizures in th e region of PL EDs were recorde d i n ove r 1/3 of our pa tients. TheEEG seizures sug ge st p ossi ble e pilep toge nic pote ntial of PL EDs. Our pa tients hada high m ortali ty rate (33%). A highe r pe rcen tag e of PL EDs was a ssoci a ted with h ighe r m ortality, perha ps representing greater severity of the underlying aetiology. Presence of EEG seizure was not associated with higher mortality. References 1. Cha trian GE, Sha w C-M, L e ff man H. T he sign if icanc e o f pe riod ic la tera lize d e pile pt iform d ischa rge s in EEG: An electrographic, clinical and pathological study. Electroencephalogr Clin Neurophysiol 1964 ; 17: 177-93. NEUROPHYSI OLOGY AND I M AGING Periodic lateralized epileptiform discharges: A et i o l ogy an d asso c i at i on w i t h EEG s ei zures Y F D an, ABS Pa n, S H Lim Nationa l Neu rosc ie nce Ins titut e -Singap ore Gen e ral Hosp ital Cam pu s (NNI-SGH), Sing apo re Neurology Asia 2004; 9 (Supplement 1) : 107 – 108
