EEG Standards
The current issue of the Canadian Journal of Neurological Sciences contains two articles about EEGs in Canada, Minimal Standards for Electroencephalography in Canada and Canadian EEG Standards: A Quality Issue.
Minimal Standards for Electroencephalography in Canada was prepared by a Task Force of the Canadian Society of Clinical Neurophysiologists to revise an earlier document outlining standards of safety and reliability of EEG in Canada.
In Canadian EEG Standards: A Quality Issue, Dr. Warren T. Blume (London Health Sciences Centre, University of Western Ontario, London, Ontario) points out that, in drawing up their document, the task force responds to two confluent trends: - a growing public awareness of and demand for quality EEG practices; and,
- the emergence of cost effectiveness as a barometer of value by ministries of health.
Dr. Blume clearly shows that although modern neuroimaging techniques have sharpened the diagnostic capability of physicians, they have "also created the false belief by the public and many physicians that MRI or CT offers the premier solution to virtually all clinical neurological problems" and that "high quality EEG affords a functional perspective to several areas of clinical neuroscience".
The following examples, excerpted from Dr. Blume's paper, clearly show the importance of high quality performance and interpretation of EEG.
Diagnosis- Epileptic discharges (spikes) appear in a single awake recording of 50% of persons with epilepsy.
- This rises to 80-85% if sleep is included.
- This compares with 2-3% of people with non-epileptic conditions.
Syndrome Identification- Seizure semiology and EEG play principal roles in establishing the epilepsy syndrome which seizures represent. Syndrome identification is requisite for management decisions and prognosis.
Epilepsy Surgery & Seizure Localisation- Focal interictal spikes on an EEG may help to identify candidates for surgery.
Dementia- EEG abnormalities may appear earlier than those of neuroimaging.
- Prognosis correlates well with the severity of EEG abnormalities.
- A normal EEG suggests either depression masquerading as dementia or the slowly progressive frontal temporal dementia of Pick's disease.
Driving- According to the Canadian Medical Association's Physician's Guide to Driver Examination, evaluation of a patent with a single spontaneous seizure or with seizures exclusively in sleep specifically includes EEG.
- EEG may aid in the evaluation of other questions related to epilepsy and driving.
Comatose States- EEG offers the best laboratory evaluation of cortical function in comatose patients.
- Its patterns help to establish the principal etiology and the prognosis for survival.
- EEG detects recurrent, clinically occult seizures, including non-convulsive status epilepticus.
Source
Canadian Journal of Neurological Sciences. 2002;29
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