Recording the Electroencephalogram EEG Recording the EEG Analyzing

Recording the Electroencephalogram (EEG)

Recording the EEG

Analyzing EEG Waves Frequency Waveform or morphology Spatial distribution

EEG Frequency Bands 76479 Beta 12. 5 - Hz 23 Hz 64279 Alpha 8 -12 Hz 9 Hz 64727 Theta 4 - 7 Hz 6. 5 Hz 75245 Delta 0. 5 - 3 Hz 1. 7 Hz

Factors That Determine Whether an EEG Feature is Normal or Abnormal • Patient Related: – Age – State of consciousness

Usefulness of the EEG • The Clinical EEG is of greatest value in: Epilepsy Coma – atypical or complicated Other disturbances of consciousness of uncertain cause

The study of the EEG remains essential to the diagnosis and treatment of epilepsy – History / Clinical impression is not always clear • • • Fit, faint or “funny turn” ? Focal or generalised Idiopathic / symptomatic / syndromic

EEG Patterns and their Specificity Signature Patterns

3 /sec Spike and Wave – the signature of Typical Absence Seizures 1 sec Onset epileptiform

Hypsarhythmia – the signature of West Syndrome ( Infantile Spasms)

Usefulness of the EEG in the diagnosis and classification of epilepsy – 13 year-old male child • Recurrent headaches and fainting. • CT normal, neurologically normal. – Description of fainting episodes: • Becomes “quiet”, falls to ground, brief “twitching of limbs”, followed by confusion • First episode 2005. Approximately 3 x year. • Family Hx – Younger sibling with seizures. – Can EEG help to confirm a Sz disorder? • If so, ? generalized or focal • Idiopathic / symptomatic ?

13 yo male EEG Background 76631 P 10 -11 Hz

13 yo male Neurology OPD Bipolar recording 76631 P

Hx of 4 year-old boy • Daily “staring spells” in nursery school • No birth injury or trauma • Neurologically normal • Paternal uncle known with epilepsy Referring doctor: • ? Absences – typical or otherwise

4 year-old boy, awake 75241

Sensitivity of the EEG • In what proportion of subjects with epilepsy can the EEG confirm epilepsy? 50% positive for epilepsy on recording the first routine 20 min EEG. Ways to improve sensitivity: • Sleep can increase the yield by further 40% • Recording during a period of increased number of seizures or shortly after a seizure A negative EEG does not rule out possibility of a seizure disorder.