**3. Lateralized periodic discharges (LPDs)**

## **3.1 EEG characteristics**

LPDs are stereotyped, repetitive EEG discharges and recurr periodically at regular intervals at 0.5 to 3 Hz; they are broadly lateralized over one hemisphere, particularly over the parasagittal and temporal areas; LPDs are usually epileptiform in appearance; they appear like sharp waves/sharp waves complexes ranging from 50 to 300 uV in amplitude or as blunt delta waves that recur in stereotyped periodic fashion (**Figure 1**). They are maximal in any focal brain lesion, sometimes asymmetrical (**Figure 2**). They are also associated with additional EEG evidence of ipsilateral cerebral dysfunction such as focal slowing, loss of posterior dominant rhythm.

#### **3.2 Frequency**

LPDs frequency on continuous EEG Monitoring (cEEG) varies from 6.2% to 8.6% [9]. In the intensive care unit, LPDs are found in 47% of patients [9]. LPDs are most commonly seen in patients with focal neurological deficit and are associated with varying degree of altered consciousness.

#### **3.3 Etiology**

LPDs are frequently associated with acute, structural brain lesion; very often with Ischemic stroke, viral encephalitis, including autoimmine encephalitis [10], tumors, intracerebral hemorrage (ICH) [11], Anoxic encephalopathy, Creutzfeldjacob disease CJD [12], Subarachnoid Hemorrage (SAH) [13], Multiple Sclerosis (MS), Posterior Reversible Encephalopathy Syndrome (PRES) (**Figure 3**); they have been also reported in Migraine headache, Mitochondrial Encephalopathy with lactic acidosis and stroke like episodes, (MELAS).

LPDs are most commonly associated with cortical gray matter or subcortical gray and white matter lesion [14]; however no structural abnormality is found on neuroimaging in 25–33% of patients with LPDs.

#### **3.4 Significance**

Are LPDs a transient EEG phenomenon following acute neurologic insult resolving usually within days to weeks? or a chronic phenomenon associated with

#### **Figure 1.**

*LPDs in a 70ys old male patient with HTN. Brain MRI compatible with PRES syndrome. Quasi-periodic LPDs lateralized over the left hemisphere. PRES: Posterior Reversible Encephalopathy Syndrome.*

#### **Figure 2.**

*Unilateral, LPDs in a 61 ys old patient with right temporal hemorrhage.*

epilepsy? Studies have reported that LPDs are found in 5–30% of patients with history of epilepsy [15], in 26% of patients with remote brain injury and epilepsy [16] and also in patients with structural brain lesions and symptomatic epilepsy [17];

*Periodic EEG Patterns in the Intensive Care Unit (ICU): Definition, Recognition and Clinical… DOI: http://dx.doi.org/10.5772/intechopen.95503*

#### **Figure 3.**

*"LPDs Plus" with complex morphology and prolonged after discharges; "Ictal appearing" LPDs in a 50 ys old patient with left sided stroke and right sided clonic seizures.*

some authors consider LPDs as an unstable, potentially epileptogenic state, a pattern on the "ictal-interictal continuum [18].

#### **3.5 LPDs and seizures: LPDs ictal pattern??**

The presence of LPDs in patients with altered mental status (AMS) is associated with increased risk of seizures. Clinical seizures are indeed very frequent in patients with LPDs; focal motor seizures are the most common (**Figure 3**) [19]; such seizures can occur prior or at the same time as LPDs [20]; the risk of developing subsequent seizures following LPDs is 10–56% [21]; LPDs may represent an ictal pattern when associated with clinical correlate such as focal clonic seizures (Stroke) and Epilepsia Partialis continua (EPC); LPDs may be ictal when associated with subtle clinical manifestations such as eye deviation, aphasia, hemianopsia in patients with AMS; in this setting both LPDs and clinical symptoms improve with antiseizure drugs (ASD); Claassen et al. have reported that LPDs are highly associated with Non Convulsive Seizures (NCSs), as high as 40% [22]. The frequency of LPDs is correlated with seizure risk [23]: LPDs of less than 1 Hz: 40% risk of seizures, LPDs of 2 Hz or greater: 66% risk of seizures. "Lateralized Periodic Discharges Plus ("LPDs plus") are LPDs with a Complex morphology, a prolonged after discharges and an "Ictal appearing" (**Figures 3**–**5**); in addition, intervening fast activities (LPD + F) (**Figures 3** and **5**), superimposed rhythmic activity (LPD + R) or both (LPD + FR) can complicate this picture. "LPDs plus" have a rapid repetitive rate (>2HZ) and are highly associated with clinical seizures [24].

#### **3.6 Management of patients with LPDs**

There are no clear data regarding the management of the LPDs in patients with AMS. However neuroimaging should be performed in all patients with LPDs; metabolic/reversible conditions should be treated; as mentioned above,

**Figure 4.**

*LPDs at a frequency of 0.5 to 1/s with a spiky appearence running at nearly regular interval.*

**Figure 5.** *64 year old left MCA infarction with jerky movements of the right upper limb. MCA: Middle Cerebral Artery.*

prolonged EEG monitoring (>24 h) is recommended in the presence of LPDs because of their association with seizures, particularly NCSs and NCSE. When LPDs are found in a confused patient, a benzodiazepine trial, such as lorazepam IV should be considered and the patient monitored (**Figures 6** and **7**). The clinical significance and management of LPDs in comatose patients is controversial [25] and there no available data regarding the continuation of ASDs after hospitalization.

*Periodic EEG Patterns in the Intensive Care Unit (ICU): Definition, Recognition and Clinical… DOI: http://dx.doi.org/10.5772/intechopen.95503*

#### **Figure 6.**

*LPDs in a 58 ys old male admitted to ICU with AMS, confused; no abnormal movements; given lorazepam 4 mg IV. AMS: Altered mental status; ICU: Intensive care unit.*

#### **Figure 7.**

*Same patient in Figure 6, 14mn following lorazepam IV. Note the dramatic EEG improvement; the patient also showed an improvement in the level of consciousness.*
