Chronic periodic lateralized epileptiform discharges during sleep in a patient with caudate nucleus atrophy: insights into the anatomical circuitry of PLEDs

Objective: Periodic lateralized epileptiform discharges have been recognize d for 33 years; however, little is known about the underlying mechanism cau sing periodic discharges. The following case provides an opportunity to stu dy PLEDs in a patient with precisely localized subcortical grey matter lesi ons. Methods: Routine EEGs and overnight polysomnography were performed on the s tudy patient. Standard 10-20 electrode positions were used, as well as EOG and chin EMG for polysomnography. Results: The study patient was a 39-year-old woman with severe left caudate nucleus atrophy and right hemi-dystonia. She had left ventral-lateral (VL) thalamotomies in 1989 and 1991, pallidotomy in 1992, and centromedian thal amic stimulator implantation in 1997. EEGs prior to surgical intervention d emonstrated left hemisphere PLEDs during sleep. Following CM nucleus stimul atory implantation, the patient had overnight polsomnography. EEG during wa kefulness and REM sleep was normal. With stages I-IV sleep left hemisphere PLEDs at 1-2 Hz were seen with fronto-temporal predominance. Sleep spindles were present bilaterally. There was no history of seizures, before or afte r surgery. Conclusions: The finding of PLEDs confined to synchronized sleep which were not affected by surgical manipulation of the motor basal ganglia circuit s uggests a role of the associative basal ganglia circuit in the generation o f periodic phenomenon. (C) 1998 Elsevier Science Ireland Ltd. All rights re served.