Journal of Clinical Neurophysiology 18(6):565–569, Lippincott Williams & Wilkins, Inc., Philadelphia © 2001 American Clinical Neurophysiology Society Periodic Lateralized Epileptiform Discharges After Complex Partial Status Epilepticus Associated With Increased Focal Cerebral Blood Flow *Imran I. Ali, *Noor A. Pirzada, and †Bradley V. Vaughn Summary: Periodic lateralized epileptiform discharges (PLEDs) are typically associated with encephalitis, cerebral abscess, cerebral infarct, and status epilepticus. There is considerable debate as to whether this pattern is ictal or interictal when seen in association with status epilepticus. We present a patient with complex partial status epilepticus who developed PLEDs and remained comatose despite optimal drug therapy. Technetium 99m single-photon emission computed tomography (SPECT) showed hyperperfusion that resolved with further aggressive antiepileptic drug therapy, indicating that this pattern may indeed be ictal. Further studies are needed to define the significance of PLEDs in patients with status epilepticus. The role of SPECT in differentiating PLEDs as an interictal or ictal pattern also requires further study. Key Words: PLEDs—Status epilepticus— SPECT—Interictal and ictal pattern. EEG pattern in association with seizures is of unclear clinical significance. In patients with focal motor seizures and PLEDs, the pattern is considered ictal; however, in the absence of any overt seizure activity, there remains considerable controversy as to whether this pattern is ictal or interictal. Treiman (1995) has described progressive stages of generalized status epilepticus, with PLEDs occurring in the final stage. There is also some debate as to whether this pattern in this clinical situation is ictal or interictal and if it should be treated aggressively. This is of great practical importance, because ongoing nonconvulsive ictal activity may also result in serious morbidity and mortality (Krumholz et al., 1995; Lothman, 1990). There are some reports in the literature suggesting that PLEDs may represent an ictal pattern (Terzano et al., 1986), especially when seen in association with status epilepticus (Handforth et al., 1994). We report on a patient with complex partial status epilepticus who developed PLEDs after termination of clinically overt seizure activity. The single-photon emission computed tomography (SPECT) scan showed focal increased Periodic lateralized epileptiform discharges (PLEDs) are defined as complexes that occur at regular intervals and persist for longer than 10 minutes or are continuous (Kuroiwa and Celsia, 1980; PohlmannEden et al., 1996). Using this definition, the incidence of PLEDs in most EEG series is approximately 0.4% to 1.0% (Kuroiwa and Celesia, 1980; Snodgrass et al., 1989; Walsh and Brenner, 1987). Periodic lateralized epileptiform discharges have been described in association with encephalitis, tumors, cerebral infarcts, and seizures (Brenner and Schual, 1990; Kuroiwa and Celesia, 1980; Raroque at al., 1993; Reiher et al., 1991; Snodgrass et al., 1989). The presence of this *Department of Neurology, Medical College of Ohio, Toledo, Ohio; and †University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, U.S.A. Presented at the American Clinical Neurophysiology Meeting, Montreal, Quebec, Canada, September 22, 2000 [abstract C110]. Address correspondence to Dr. Imran I. Ali, Associate Professor and Director, Comprehensive Epilepsy Program, Department of Neurology, Medical College of Ohio, 3120 Glendale Avenue, Toledo, OH 43617; email: iali@mco.edu. 565 566 I. I. ALI ET AL. FIG. 1. EEG showing periodic lateralized epileptiform discharges. cerebral blood flow corresponding to the location of PLEDs, indicating the possibility that this pattern may indeed be ictal. CASE REPORT A 51-year-old right-handed woman who had metastatic lung adenocarcinoma to the left parietal lobe resected 6 months previously presented to the Medical College of Ohio Emergency Department with generalized tonic-clonic seizures. She was prescribed 100 mg of phenytoin by mouth three times a day and discharged. The following day, she presented again to the emergency room with confusion and aphasia. Before arrival in the Emergency Department, she had reported right upper extremity paresthesiae and had involuntary clonic activity of the right arm. An initial examination revealed evidence of partial expressive J Clin Neurophysiol, Vol. 18, No. 6, 2001 and receptive aphasia and mild right-sided weakness. She was given an additional 10 mg/kg of phenytoin intravenously without significant improvement. EEG showed continuous rhythmic left temporal and parietal spike and wave activity consistent with complex partial status epilepticus. The patient was then given 15 mg/kg of intravenous valproic acid followed by infusion of 1 mg/kg/h of valproic acid for 6 hours with partial resolution of the aphasia. EEG monitoring continued to show frequent electrographic seizures, and the findings of the patient’s neurologic examination fluctuated. She was transferred to the intensive care unit, intubated, and loaded with 20 mg/kg of phenobarbital. The ictal EEG pattern persisted, and another 10 mg/kg of phenobarbital was administered intravenously. This EEG pattern remained refractory to phenobarbital, midazolam, and propofol infusions at optimal doses. On the eleventh day after presenta- PERIODIC LATERALIZED EPILEPTIFORM DISCHARGES AFTER COMPLEX PARTIAL STATUS EPILEPTICUS 567 FIG. 2. Coronal section of technetium 99 single-photon emission computed tomography scan showing increased blood flow in the left temporal and parietal region. tion, PLEDs were noted over the left temporal and parietal region (Fig. 1) with no electrographic or clinical seizure activity. A computed tomography and MRI scan of the brain with contrast did not show evidence of tumor recurrence. A technetium 99 SPECT scan was performed and showed focal increased blood flow over the left parietal and temporal region (Figs. 2 and 3). Pentobarbital infusion at 5.5 mg/kg/h (loading dose: 12 mg/kg) resulted in resolution of this pattern. The patient subsequently recovered with some residual memory and attention deficits. A repeat SPECT scan after termination of the PLEDs showed resolution of focal increased cerebral blood flow (Fig. 4). The patient remained stable and has not had any recurrence of the tumor in the brain. DISCUSSION There is considerable debate regarding the significance of PLEDs in patients with status epilepticus. Handforth and Treiman (1995) have previously reported a patient with PLEDs who had focal increased cerebral metabolism on positron emission tomography. Our patient developed PLEDs after resolution of complex partial status epilepticus. Because of persistent coma and inability to differentiate between medication-related coma and continuing seizure activity, a SPECT scan was performed. The SPECT scan showed increased cerebral blood flow in the left posterior temporal and parietal region, suggesting that this pattern was indeed ictal. If this pattern were interictal, SPECT would be expected to show hypoperfusion. A SPECT scan shows increased localized isotope uptake during a seizure, with a decrease in isotope uptake in the postictal state (Duncan, 1997). In complex partial seizures, the seizure focus has been correctly identified in 69% to 93% of ictal SPECT studies; therefore, the presence of cerebral hyperperfusion as seen in this case is likely a sensitive indicator of increased cerebral blood flow related to ictal activity. Other causes for the increased cerebral blood flow such as tumor recurrence or infection were excluded based on serial imaging as well as cerebrospinal fluid analysis. AgJ Clin Neurophysiol, Vol. 18, No. 6, 2001 568 I. I. ALI ET AL. FIG. 3. Sagittal section of technetium 99 single-photon emission computed tomography scan showing increased left parietal blood flow. gressive treatment of this pattern resulted in clinical as well as electrographic improvement. This case illustrates a number of important principles. First, PLEDs can occur after complex partial status epilepticus, although they have most often been associated with focal motor seizures (Pohlmann-Eden et al., 1996). Secondly, PLEDs in association with status epilepticus are likely to be ictal, especially if they are accompanied by persistent alteration of neurologic status as was the case in our patient. Our patient remained comatose despite appropriate therapy, and we were unable to differentiate between medication-induced coma and persistent ictal activity as a cause for this state of unresponsiveness. The presence of cerebral hyperperfusion with persistent altered neurologic function after status epilepticus may indicate that PLEDs are ictal and need to be treated aggressively. Alteration of neurologic function, which occurs in all patients with status epilepticus, usually resolves with appropriate treatment. A persistent state of altered neurologic function (e.g., coma, encephalopathy) that does not resolve over an J Clin Neurophysiol, Vol. 18, No. 6, 2001 expected time frame in the presence of PLEDs, especially in association with therapy that may impair neurologic function, however, requires further evaluation. Our approach is most useful in patients in whom PLEDs develop after status epilepticus and expected clinical improvement does not occur. In conclusion, in patients who develop PLEDs after status epilepticus, SPECT seems to be a useful method for detecting focal cerebral hyperperfusion and may provide confirmatory evidence that PLEDs are ictal. Further research needs to be performed regarding the significance of PLEDs and the role of SPECT scanning in such patients with status epilepticus, because this may have broad implications for management of this condition. REFERENCES Brenner RP, Schaul N. Periodic EEG patterns. Classification, clinical correlation, and pathophysiology. 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