neurology

 

HomeDisorderse-TextbooksHandbooksAll JournalsMeetingsTell A FriendContact Us

EEG Guidelines

Patient Preparation

  • The technician explains the EEG procedure to the patient.
  • Technician obtains all patient and clinical data needed for the EEG report and billing.
  • Patient information includes correct spelling of patient's name, medical record number, date of birth, referring physician, patient location, procedure number.
  • Clinical information includes type of procedure requested, reason for EEG, relevant symptoms, description of seizure and current medications.
  • Medications are listed and spelled correctly.
  • The patient data are logged in correctly.
  • The technician verifies physician signature on request form

Machine operation

  • The technician adjusts EEG machine settings to obtain optimum accurate recording. This includes calibration and correct montages.
  • Technician applies electrodes correctly within 30 minutes. This includes 10/20 electrode placement or cap.
  • The technician verifies that the electrodes are functioning correctly.
  • The technician tests the system by having the patient blink rapidly, look to right and left repeatedly, count to 30 and open and close eyes.
  • Technician identifies & responds appropriately to significant EEG patterns.
  • Significant EEG patterns include normal variants, artifact patterns and abnormal EEG patterns.
  • Appropriate responses include: label the correct type of pattern, eliminate artifacts when present, apply additional electrodes, add additional channels to montage, use activation procedures or change the recording method so that the pattern may be interpreted most accurately.  The technician may add additional monitoring electrodes for eye movements, ECG, respiration and limb movements.
  • The technician records 20 minutes for routine studies and 30 minutes for sleep deprived studies.
  • Technician removes electrodes correctly, cleans the patient's scalp, cleans the electrodes and sterilizes electrodes when appropriate.
  • Technician completes all needed forms and transfers the EEG data for interpretation.

Patient monitoring

  • The patient's state of alertness is measured periodically.
  • Patients with coma or altered mental state may be tested with auditory or tactile stimulation.
  • Patients with seizures or pseudoseizures are tested for responsiveness.

Photic stimulation and hyperventilation

  • The patient performs 3 minutes of hyperventilation when there are none of the following contraindications:
    • cardiac disease
    • respiratory disease
    • sickle cell disease
    • severe hypertension
    • acute stroke
  • The technician performs photic stimulation at 1, 3, 6, 9, 12, 15, 20, 25 and 30 Hz.

Maintenance

  • The technician archives files on CD-ROM correctly.
  • The technician records any adjustments for inventory and orders supplies as needed.

Additional actions taken for other specialized studies are listed below:

EEG - Video

  • The technician maintains good quality video recording
  • EEG -video is reviewed and clinical events and seizures are labeled.
  • EEG-video recordings are edited
  • Video and EEG are archived

Electrocerebral silence recordings: Body temperature and barbiturate levels are recorded.  The technician performs the study in accordance with "Guideline three: Minimum technical standards for EEG recordings in suspected cerebral death".

Neonatal recordings:

  • Apgar scores, conceptional age, post natal and gestational age are recorded.
  • Respiratory, ECG, eye movement and chin EMG channels are recorded
  • A reduced set of scalp electrodes is used
  • The technician give notations for eyes open, eyes closed, frown, smile, grimace, sucking, eye movements, penile erections, quiet sleep, active sleep and awake.
  • The minimum recording time is 30 minutes

Operative EEG monitoring

  • The technician records the type of surgery performed
  • The technician records: 
    • The type, time and method of administration of all drugs given during surgery.   Method of administration refers to bolus injections, inhalation or continuous intravenous infusion
    • Periodic blood pressure measurements
    • Keys steps in the surgical procedure
  • The technician identifies significant reductions in EEG amplitude, lateralized or generalized slowing and reports this to the physician.
  • The technician records the location of all implanted electrodes.  
  • The technician records the superior - anterior, superior - posterior, inferior - anterior and inferior - posterior contacts of all subdural arrays.
  • The technician also records the electrode contacts that overly the Sylvian fissure. 

Multiple sleep latency test

  • Four trials of 30 minutes each are completed
  • The technician notes when there are 30 seconds of continuous stage I sleep

EEG Label

Electrode location

  • Always review with average reference because this is the easiest montage to interpret.
  • Give electrode locations in order of amplitude as seen on referential average montage.
  • Only the first few locations need to be given.

Labels

  • Label the seizure when the first seizure related EEG feature occurs.
  • Label the clinical onset when the first seizure related behavior occurs.
  • Label the spell when the first behavior of the spell occurs.
  • Avoid an excessive number of labels.  Describe only seizure or spell related events.

EEG labels

Feature Label method Example
Scalp EEG seizure onset Sz + location Sz Sp2, F8
Intracranial EEG seizure onset Sz + location Sz LOT 4,5
Subclinical seizure Sub Sz + location Sub Sz LOT 4, 5
Non-epileptic event Spell Spell
Clinical onset Clinical onset Clinical onset
Epileptiform discharge Electrode location Sp2, F8
Slowing Slow + location Slow F8, T8
Uncertain seizure ?Sz + location ?Sz F8, T8
Uncertain epileptiform discharge ?electrode location ?Sp2, T8
Uncertain slowing ?slow + location ?Slow F8, T8
Descriptive comments Text comments Lip smacking
 

EEG Report Guidelines

  • Reports consist of the following sections: introduction, description, impression and clinical correlation.
  • Introduction
    • Describe the reason for the EEG with an appropriate diagnosis. 
    • Describe when sphenoidal or intracranial electrodes are used.
    • Intracranial electrodes are described the electrode type, anatomical descriptive name, abbreviation in parentheses and number of contacts.  
    • The intracranial electrode types are sudural strip, subdural array and depth electrode.
    • Subdural array contact locations are designated by listing the contact numbers for the most anterior inferior, anterior superior, posterior inferior and posterior superior contact locations.
    • The neurosurgeon names all intracranial electrodes.  The nomenclature describes the electrode using the deepest and then most superficial anatomical location.
  • Description:
    • Describe any significant background abnormalities.
    • Describe the location of epileptiform discharges.
    • Describe the most frequent sites of epileptiform discharges.
    • For scalp EEG recordings of temporal lobe discharges, describe if the discharges are lateralized to one side more than 90% of the time.
    • List the seizure types and onset times for all seizures.  The times indicate the earliest onset of an ictal EEG pattern.  The seizure types are ILAE designated seizure categories e.g simple partial, complex partial etc.
    • Describe the observed behavior for all seizures.  Important behaviors include, arrest of motor activity, automatisms, dystonic posture, versive head or eye movements or stereotyped posture.   
    • Describe the time of the first seizure related behavior.
    • For ictal SPECT injections, describe the injection time, time of secondary generalization and time of seizure cessation.
  • Impression:
    • Describe if the seizure was normal or abnormal.
    • If abnormal, list the abnormal EEG findings.
    • If a non-attending wrote the report:
    • The attending physician is required to verify the EEG findings, edit the report and then state that the attending has personally reviewed the EEG and edited the above report. 
    • Clinical correlation:
    • The appropriate clinical diagnoses that are supported by the EEG findings should be listed. 
  • Example #1:  

Introduction: This recording was performed for evaluation of intractable complex partial seizures.  The recording was performed with scalp and sphenoidal electrodes.

Description: The background consisted of 10 Hz rhythmic activity.  The patient had right temporal lobe epileptiform discharges (Sp2). The patient had four complex partial seizures at 6:53:40, 8:39:44, 18:06:43 and 22:21:43. The ictal EEG pattern consisted of bilateral 4-5 Hz 2 second burst of slow waves followed by 4-5 Hz rhythmic right temporal lobe (Sp2) within 3-4 seconds of seizure onset. The 
behavioral change began at the same time as EEG seizure onset. The behavior consisted of a head drop, blank stare, right arm picking movements and rocking movements in bed. During the first 2 seizures, the patient had vocalization, sustained head and eye turning to the left followed by tonic-clonic activity. Left facial convulsive activity was seen on the first seizure. He received ictal SPECT injection at 8:40:10, he began convulsions at 8:40:33 and the seizure ended at 8:42:02.

Impression: This was an abnormal prolonged recording because of epileptiform discharges and seizures. 

Clinical correlation: This finding is consistent with the history of epilepsy.

  • Example #2: 

Introduction: This recording was performed for epilepsy surgery evaluation.  The patient has intractable complex partial seizures.  The intracranial electrodes were: rectangular 20 contact left lateral temporal (LLT) electrode, 4 contact left temporal polar (LTP) electrode, 4 contact left anterior subtemporal (LAST) electrode, 4 contact left posterior subtemporal (LPST) electrode and 8 contact left occipital temporal (LOT) depth electrode. The LLT electrode contact #1 was anterior inferior, #5 anterior superior, #16 posterior inferior and #20 posterior superior. The electrodes closest to the Sylvian fissure were LLT 4, 9, 14 and 19.  

Description: Epileptiform discharges were recorded from LLT 1-4 and LOT 1-2.  No seizures were recorded.  

Impression: This was an abnormal prolonged recording because of epileptiform discharges. 

Clinical correlation: This finding is consistent with the history of epilepsy.

American Electroencephalographic Society Guidelines in Electroencephalography, Evoked Potentials and Polysomnography: J Clin Neurophysiol 2006 23(2)