Chapter 8 The Structure and Philosophy of the EEG Report
IDENTIFYING INFORMATION
The EEG report generally starts with clinical identifiers, including the patient’s name and date of birth, the name and location of the laboratory performing the study, the date of the study, and the name of the referring physician. Next, a brief clinical history is given that includes the general indications for which the study was ordered. This brief summary may reflect a combination of the clinical information that has been provided by the referring physician and additional history that has been obtained from the patient or family by the EEG technologist. The medications taken by the patient and the date of the most recent seizure may also be given, if applicable. This history is usually recounted in a concise fashion:
This 60-year-old woman is referred because of episodes of confusion lasting 1 to 2 minutes that started approximately 1 month ago. There is a history of a left-sided stroke 3 years previously. The EEG is requested to rule out seizures.
This clinical description serves multiple purposes. First, it may alert the EEG technologist to the necessity of using specific recording techniques. For instance, absence seizures are suspected, the technologist may concentrate particularly on hyperventilation, perhaps even performing it twice. If temporal lobe epilepsy is suspected, the technologist may place extra electrodes over the temporal areas. Second, when the EEG report is completed, issues surrounding the clinical indications for the study are often addressed in the final “Clinical Correlation” paragraph at the end of the report. For example, if the referring physician suspected temporal lobe epilepsy, the EEG report may include additional pertinent negatives that directly address the clinical question posed, such as a comment that no epileptiform or slow-wave activity was noted in the temporal areas. Finally, the clinical history may also alert the technologist and the reader to special situations such as skull defects from previous surgeries, areas of the scalp that are inaccessible because of a bandage or other instrumentation on the head, or perhaps the fact that this is the fourth EEG in a sequence obtained on a patient in a coma.
TECHNICAL SUMMARY
Next, a technical description of the procedure used for the recording is provided. Because in any given laboratory most EEGs are recorded by a standard technique, this descriptive paragraph is usually standardized and only requires revisions when there are deviations from the laboratory’s routine procedure. Because the technologist is responsible for the recording procedure, this paragraph is typically produced by the technologist. An example of a procedure description for a routine EEG is as follows:
A 21-channel digital electroencephalogram was performed in the Clinical Neurophysiology Laboratory of The Particular Hospital at a sampling rate of 256 samples per second. The 10-20 international system of electrode placement was used and both bipolar, and referential electrode montages were monitored. Additional electrodes were placed at FT9 and FT10. The patient was sleep-deprived. No sedation was administered. The patient was recorded during the waking, drowsy, and sleep states. The total recording time was 41 minutes.
The next three sections represent the core of the EEG report and are produced by the interpreting electroencephalographer. These include a description of the appearance and findings of the EEG, a summary of the findings or interpretation of the EEG (which may include an “abnormality list”), and a clinical correlation paragraph discussing the clinical implications of the findings. Each of these sections is now discussed in more detail.
DESCRIPTION
Here the electroencephalographer provides a concise description of the appearance of the EEG. Precise technical terms are used in this part of the report, including electrode names from the international 10-20 system and a variety of other EEG terminology. The goal of this portion of the report is to allow another electroencephalographer to visualize the appearance of the recording without actually having seen the original tracing. Provided with a well-written description, an experienced electroencephalographer should ideally be able to draw up the same abnormality list and clinical conclusions that would have been made had he or she personally reviewed the tracing. To provide this level of detail, the technical description paragraph may include EEG terminology that is not necessarily completely understandable by an internist or other general physician, or even in some cases by a neurologist who does not specialize in electroencephalography.
A good description allows a second electroencephalographer either to confirm the identifications of waveforms given in the interpretation paragraph or perhaps to disagree with them. For instance, if low-voltage sharps waves in sleep in the occipital areas with positive polarity were described as epileptiform activity, such a description may lead a second (more experienced) electroencephalographer to reject this interpretation and reidentify them as POSTS (positive occipital sharp transients of sleep), a normal variant (see Chapter 11, “Normal Variants in the EEG,” for further discussion of POSTS). Formally, the description paragraph should consist of pure description of the visual appearance of the EEG; conclusions as to whether a described wave is normal or abnormal are not absolutely required in this paragraph and would usually appear in the interpretation section. In practice, for clarity’s sake, some readers will flag findings as normal or abnormal in the description, especially if there are multiple findings, so that the message of the report is as clear as possible.
A moderate amount of 11- to 12-Hz medium-voltage rhythmic waves are seen posteriorly that suppress with eye opening. A small amount of symmetric 18–30 Hz low-voltage fast activity is seen anteriorly bilaterally.
Stage II sleep is seen with vertex waves and a moderate amount of 14-Hz bicentral sleep spindles. Low- to medium-voltage sharp waves are seen occasionally in T8.
These two paragraphs describe the background activity during wakefulness and the presence of normal sleep elements. It is also clear that the right anterior temporal sharp waves were seen in sleep but not during wakefulness.
INTERPRETATION
This paragraph generally starts by clearly stating whether the EEG is considered normal or abnormal, assuming that this determination can be made. Terms such as “probably normal” or “probably abnormal” should be avoided whenever possible as they limit the usefulness of the report and are often found frustrating by the clinician who receives the report. Such noncommittal terms should only be used in the small minority of cases in which a determination of normality is not possible.
At this point in the report, it is also useful to give an abnormality list, an example of which follows:
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