Periodic Lateralized Epileptiform Discharges

Dr.Roopchand.PSSenior Resident Academic

TDMC, Alappuzha

• The term periodic lateralized epileptiform discharges (PLEDs), first coined by Chatrian and colleagues in 1964, is a peculiar electroencephalogram (EEG) pattern consisting of unilateral and focal spikes or sharp wave complexes that appear periodically, usually at the rate of 1~2 s.

Description:

• Classically triphasic with a sharply contoured wave followed by a slow wave.

• Incidence of 0.4% to 1%• Usually a singular focus – PLED’s• Duration is between 100 to 300 ms• Amplitude is 100 to 300mV

• It is the conserved recurrence pattern that is more important than morphology.

• The regularity may vary– Can be highly regular– With out any set interval.

• Recurrence frequency commonly fall in the range of one transient every 0.5 to 4 sec– 2 sec interval is mc

• Low amplitude slow activity separates PLEDs.

PLEDs or ECG?

• Both have similar morphology and periodicity.• Simultaneous ECG recording helps.• PLEDs not as regular as ECG.• ECG may be unilateral or bilateral• PLEDs are not bilateraly synchronous.

• BiPED – large frontal fields.• ECG – temporal region.• ECG usually 1Hz. • PLEDs can be differentiated from inter ictal

discharges by periodicity.• IEDs can periodically recur but interval varies

and occur only sporadically.

Clinical significance:

• Indicated focal pathology that is acute or sub acute.

• May indicate a cortical involvement and co existing metabolic abnormality.

• Over all significance is same in children and adults.

• 80% cases there will be a co localized focal deficit.

• PLEDs usually lasts day to weeks.– Rarely years.

• Causes:• Cortical strokes (50%)– Embolism, watershed infarcts

• Tumors and cerebral infections(20%)• Prion diseases, extra-axial hematoma,

epilepsy.

• Rare causes:– Alzheimer's ds– Mitochondrial ds– MS– Intoxication with baclofen, lithium, levodopa,

ifosfamide.– Trauma with out subsequent hemorrhage.

• PLEDs indicate clinically significant risk for seizures.

• Seizure occur in up to 80% of patients with PLEDs.– Focal motor seizure MC

• 20% with PLEDs are comatosed and 80% will have impaired consciousness.

• Among infections HSE is the MC.

• Most HSE shoes PLEDs at some point of time.• MC with in a week of onset of symptoms.• Disappears by 2 weeks after the onset.• PLEDs due to HSE is almost always centered

over one or both temporal lobes.• When B/L are synchronous and time locked.– Interval 1.5 to 2.5 sec

• Inter discharge intervel almost always 1 to 5 sec.

• Other viruses producing temporal PLEDs: influenza B, LaCrosse.

• CJD is the MC prion disease producing PLEDs.– Helps to differentiate CJD from other dementias.– 67 – 100% CJD will have PLEDs.– Recur every 0.5 to 2 sec– Usually hemispheric with focal predominance

when they first manifest.– Present only during wakefulness.– Onset after several months of onset of clinical ds.– Evolve to BiPED as disease progress and

disappears.

Reiher Classification(1991):

• Reiher et al. (1991) described the brief and low amplitude focal stereotyped rhythmic discharges (RDs) closely associated in temporal and spatial distributions to higher amplitude interictal epileptiform discharges.

• They subdivided PLEDs into two categories: • (1) PLEDs plus- associated with RDs and• (2) PLEDs proper-not associated with RD.

• PLEDs proper were subdivided into PLEDs of classes 1, 2, and 3– Based on the metronomicity of the periodicity.

• PLEDs plus could be subdivided into PLEDs of classes 4 and 5.– Based on the duration of RDs

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