Electroencephalography in Neuropsychiatry

Case reports have described patients in whom borderline personality disorder (BPD) was diagnosed but who were subsequently found to have complex partial seizures documented by epileptic discharges over temporal regions.¹⁰ The prevalence of abnormal EEGs among clinic populations ranges from 6.6% in patients with rage attacks and episodic violent behavior to 53% in patients with antisocial personality disorder. ^11,12 A flowchart for evaluation of patients presenting with episodic aggressive behavior is shown in Figure 3.

Whether an abnormal EEG predicts a favorable therapeutic response to anticonvulsants is currently unknown. Anticonvulsants can block epileptiform discharges and can lead to dramatic clinical improvement in persons exhibiting repeated and frequent aggression.¹³ The addition of carbamazepine(Drug information on carbamazepine) to the treatment regimen of patients with schizophrenia who also exhibit EEG temporal lobe abnormalities but no history of seizure disorder can be beneficial.¹⁴ Anticonvulsants also may reduce aggressive tendencies irrespective of EEG abnormalities.¹⁵

Finally, panic symptoms resemble symptoms induced by temporolimbic epileptic activity, particularly that originating from the sylvian fissure. Panic disorder is the most common psychiatric disorder that must be differentiated from temporal lobe epilepsy.¹⁶

Frank¹⁷ reported that 21 (31%) of a sample of 64 children with attentiondeficit/ hyperactivity disorder had abnormal SEEG. Of these, 84% had spikes or spike-wave discharges. Hughes and associates¹⁸ found “definite noncontroversial epileptiform activity” in 53 (30.1%) of 176 children with ADHD. Mainly focal and usually occipital or temporal, the epileptiform activity was less often generalized, with bilaterally synchronous spike and wave complexes seen in 7% of children.

Several large, independently replicated studies have shown that QEEG distinguishes between healthy children and those who have a variety of attention or learning disorders, with accuracies typically exceeding 80%. While autism cannot be diagnosed based on EEG findings, an EEG can help rule out the presence of epileptic activity that is relatively common in this group.

For an adequate SEEG evaluation, the clinical reason for the referral must be considered. If a slow-wave abnormality is suspected, an awake recording is sufficient. The most important caveat is to make absolutely sure that the patient is alert during the procedure. In patients with borderline results, the inclusion of hyperventilation could enhance the abnormality.

If the purpose of SEEG is to rule out epileptiform discharges, an awake EEG is inadequate, and the inclusion of a sleep tracing is important. The EEG report should clearly indicate the stage of sleep during the recording. Serial recordings enhance the likelihood of finding abnormalities, particularly epileptiform abnormalities.¹⁹ In our experience, the yield of more than 2 recordings does not justify the added expense. The second recording may be performed following sleep deprivation.

As a post hoc analytic procedure, QEEG is supplementary and complementary to SEEG. No special recording procedures are required other than ensuring that filters and sampling rates are set at specified levels. Virtually all modern EEG machines can provide a digitized record suitable for computerized analysis. Because QEEG analysis is easily biased by artifacts, the electroencephalographer begins by selecting artifact-free samples of the alert eyes-closed SEEG, which then are analyzed mathematically using commercial software. Abnormalities detected by QEEG are traced back to the original SEEG and interpreted by the electroencephalographer.