▁se iz ures ▁commonly ▁involve ▁mus cle ▁rig id ity , ▁conv uls ions ▁and ▁loss ▁of ▁conscious ness . ▁Gener ally , ▁the ▁rec urrence ▁is ▁one ▁to ▁two ▁times ▁per ▁month . ▁In ▁the ▁years ▁following ▁the ▁on set ▁of ▁se iz ures , ▁a ▁notice able ▁decrease ▁in ▁intellectual ▁capacity ▁is ▁observed . ▁ ▁Ad oles c ence ▁ ▁During ▁pub ert y , ▁se iz ure ▁frequency ▁increases ▁to ▁one ▁to ▁two ▁times ▁per ▁week . ▁M ental ▁function ▁has ▁a ▁rapid ▁decl ine , ▁as ▁observed ▁by ▁a ▁lack ▁of ▁coord ination , ▁failure ▁to ▁complete ▁education ▁and ▁fine ▁motor ▁activities . ▁In ▁rare ▁cases , ▁some ▁suffered ▁from ▁loss ▁of ▁vision . ▁ ▁Ad ul th ood ▁ ▁Se iz ure ▁frequency ▁is ▁reduced ▁to ▁four ▁to ▁six ▁se iz ures ▁per ▁year . ▁By ▁this ▁time , ▁they ▁are ▁ment ally ▁and ▁phys ically ▁in cap able ▁to ▁live ▁without ▁assistance ▁due ▁to ▁the ▁total ▁mental ▁de grad ation . ▁Life ▁expect ancy ▁is ▁at ▁least ▁ 5 0 ▁years ▁of ▁age , ▁which ▁is ▁shorter ▁than ▁the ▁average ▁world wide ▁age ▁of ▁ 7 0 . ▁ ▁Gen etic ▁causes ▁ ▁Northern ▁ep ile ps y ▁synd rome ▁is ▁caused ▁by ▁an ▁inherited ▁aut os om al ▁re cess ive ▁mut ation ▁in ▁the ▁tel omer ic ▁region ▁of ▁the ▁short ▁arm ▁of ▁chrom os ome ▁ 8 . ▁There ▁are ▁at ▁least ▁ten ▁mut ations ▁within ▁the ▁chrom os ome ▁that ▁cause ▁the ▁disease