From the Guidelines
Lateralized periodic discharges (LPDs) on an electroencephalogram (EEG) are a significant finding that often indicates underlying acute or subacute brain injury and is associated with an increased risk of seizures. These discharges typically appear as sharp waves or complexes that repeat every 0.5-3 seconds and maintain a relatively consistent morphology. LPDs are concerning because they are associated with an increased risk of seizures, particularly focal seizures that may secondarily generalize. According to the American Clinical Neurophysiology Society criteria, LPDs are considered part of the ictal-interictal continuum, which includes rhythmic or periodic patterns that are considered to be possible seizure or status epilepticus even without fulfilling strict electrographic criteria 1.
Causes and Associations
Common causes of LPDs include stroke, traumatic brain injury, brain tumors, encephalitis, or other focal cerebral lesions. LPDs are significant findings that often indicate underlying acute or subacute brain injury. The presence of LPDs can be an indicator of the underlying cause, with specific patterns and locations on the EEG corresponding to different etiologies. For example, in herpes simplex encephalitis, EEG abnormalities include non-specific diffuse high amplitude slow waves, sometimes with temporal lobe spike-and-wave activity and periodic lateralized epileptiform discharges (PLEDs) 1.
Management and Treatment
When LPDs are identified on EEG, patients typically require neurological evaluation and may need antiseizure medication treatment, especially if they have experienced clinical seizures or altered mental status. The management approach depends on the underlying cause, with treatment directed at both the primary condition and seizure prevention if necessary. Continuous EEG monitoring is often recommended to detect subclinical seizures and evaluate treatment response in these patients. The TELSTAR trial suggests that patients with LPDs, particularly those with frequencies reaching at least 0.5-2.5 Hz, may benefit from protocolized, tiered antiseizure treatment 1.
Key Points
- LPDs are abnormal brain wave patterns that indicate underlying brain injury and increased risk of seizures.
- Common causes include stroke, traumatic brain injury, brain tumors, encephalitis, or other focal cerebral lesions.
- LPDs are part of the ictal-interictal continuum and may require antiseizure medication treatment.
- Continuous EEG monitoring is recommended to detect subclinical seizures and evaluate treatment response.
- The management approach depends on the underlying cause, with treatment directed at both the primary condition and seizure prevention if necessary.
From the Research
Lateralized Periodic Discharges on EEG
Lateralized periodic discharges (LPDs) are a type of electroencephalographic (EEG) pattern that can be seen in critically ill patients. The clinical significance of LPDs is uncertain, but they are thought to be associated with a variety of etiologies, including brain injury and epilepsy 2.
Characteristics of LPDs
LPDs are characterized by periodic discharges that occur at regular intervals, typically in one hemisphere of the brain. They can be further classified into different subtypes, including LPDs-proper and LPDs-plus, based on their electrographic features 3. LPDs-plus are thought to be more closely associated with ictal activity and may be a sign of focal non-convulsive status epilepticus.
Clinical Significance of LPDs
The presence of LPDs on EEG has been associated with a range of clinical outcomes, including abnormal consciousness, seizures, and functional decline 4. Patients with LPDs are also less likely to be discharged home from the hospital and may require longer periods of EEG monitoring to detect seizure activity 4, 3.
Risk Stratification of LPDs
The electrographic features of LPDs can be used to risk-stratify patients for the development of electrographic seizures. LPDs with rhythmicity, overlying fast frequencies, or sharply contoured morphology are thought to be more closely associated with seizure activity, while those with blunt delta morphology are thought to be lower risk 5.
Hemodynamic Changes Associated with LPDs
LPDs have been associated with changes in cerebral hemodynamics, including increased cerebral oxygen saturation and total hemoglobin concentration in the affected hemisphere 6. However, higher frequencies of LPDs have been associated with decreased cerebral oxygen saturation and oxygenated hemoglobin concentration, suggesting that LPDs may increase oxygen demand on the ipsilateral hemisphere.
- Key features of LPDs:
- Periodic discharges that occur at regular intervals
- Typically seen in one hemisphere of the brain
- Can be classified into different subtypes, including LPDs-proper and LPDs-plus
- Clinical significance of LPDs:
- Associated with abnormal consciousness, seizures, and functional decline
- Less likely to be discharged home from the hospital
- May require longer periods of EEG monitoring to detect seizure activity
- Risk stratification of LPDs:
- Electrographic features can be used to risk-stratify patients for the development of electrographic seizures
- LPDs with rhythmicity, overlying fast frequencies, or sharply contoured morphology are thought to be higher risk
- Hemodynamic changes associated with LPDs:
- Increased cerebral oxygen saturation and total hemoglobin concentration in the affected hemisphere
- Higher frequencies of LPDs associated with decreased cerebral oxygen saturation and oxygenated hemoglobin concentration