Chapter 66. Electroencephalography

• Suspected epilepsy.

• Suspected ongoing seizures or subclinical status epilepticus.

• Epilepsy characterization.

• Unexplained encephalopathy or coma.

• Monitoring medication-induced coma.

• Paralyzed patients with possible seizures.

• Medication titration.

• Scalp abrasion after prolonged monitoring is a minor risk.

• Automatic spike and seizure detection paradigms are not sensitive or specific enough to base clinical decisions on at this time.

• Cardiac and respiratory artifacts are often misinterpreted as epileptiform.

• Patients with focal (localization related) epilepsy may have normal or near normal interictal electroencephalograms (EEGs).

• In neonates, there is a paucity of clear epileptiform abnormalities even in patients with frequent seizures, thus prolonged monitoring should be strongly considered in place of routine studies.

• EEG must be considered in clinical context.

• An abnormal EEG is not always suggestive of epilepsy and may reflect a nonepileptic encephalopathy.

• The EEG is not painful or dangerous, although the placement of the electrodes may require the child’s restraint for a few minutes.

• Patient’s hair should be washed and free of oils and chemical agents prior to the study; any braids in hair need to be removed.

• Metal EEG electrodes are placed over the scalp in standardized positions and fixed with a variety of specialty adhesives.

• • The glue can leave a small red welt on the scalp, which will resolve in a few days.

  • Alcohol can be helpful in removing stuck adhesive.

• Impedance is checked to determine appropriate electrical connectivity.

• The electrode wires are attached to the head box, which is then attached to the monitoring unit (usually a computer with screen for EEG display).

• The study is performed by placing electrodes each approximately the size of a pea on the scalp and affixing them with some type of adhesive (usually paste or glue).

• Most commonly, 21 electrodes are affixed.

• The electrodes are connected to the EEG machine by thin wires usually pulled together into a “ponytail.”

• The patient may be asked to perform certain “maneuvers” that may bring out EEG abnormalities.

• • Intermittently closing his or her eyes.

  • Watching flashing strobe lights.

  • Hyperventilating for 2–3 minutes.

• Sleep is often important to capture as well, and parents may be asked to keep their child awake on the night before the study.

• A routine outpatient EEG usually is performed for approximately 45–60 minutes but longer studies may be required.

• After the EEG is complete, the electrodes can be easily removed after the EEG machine is turned off.

• A normal EEG result rarely rules out the possibility of seizures just as an abnormal EEG may not diagnose epilepsy or risk of recurrent seizures.

• EEG must be used in the context of a neurologic evaluation and only rarely can replace it entirely.

• Appropriate filters should be placed on the recording to minimize electrical and mechanical interference.

• A montage (display paradigm ...