The most common codes for continuous ICU EEG monitoring are 95951 and 95956. They code for 24-h EEG recordings. Both codes require that interpretations can be made throughout the recording time, and, based upon those interpretations, some clinical and technical interventions can be made to alter or end the recording or to alter the patient care during the recordings as needed. In other words, these are true monitoring codes that can affect patient care. They are not simply prolonged EEG recordings. They allow for active influence of patient care during the recording period.

Code 95951 specifies, “monitoring for localization of cerebral seizure focus by cable or radio, 16 or more channel telemetry, combined EEG and radio recording and interpretation (e.g., for presurgical localization), each 24 h.” This code typically and traditionally is used in the inpatient epilepsy monitoring unit (EMU). It requires video recording and review along with EEG. Cable-hardwired recording systems may be substituted for radio telemetry. The service describes monitoring in which a clinician can read the record during the recording as needed. The recording is continuously monitored. Note that it requires at least 16 channels.

Code 95956 specifies “monitoring for localization of cerebral seizure focus by cable or radio, 16 or more channel telemetry, EEG recording and interpretation, each 24 h, attended by a technologist or nurse.” Like the EMU code above, this code requires a clinician who can review the record during the recording as needed and make changes in patient care during the time of the recording. This code differs from 95951 because it does not include video monitoring or review. It specifies that the recording be attended by a nurse or technologist, i.e., someone is keeping an eye on this EEG continuously, either at the patient’s bedside or at a central station. This code also requires at least 16 channels.

Two other EEG codes deserve special mention: codes 95813 and 95827. Code 95813 specifies, “extended EEG, greater than 1 h.” This code has several original purposes. One such purpose was as a bedside EEG machine in the early days of ICU EEG monitoring in which the paper recording might last for only 4–8 h during the day. It does specify more than 1 h of recording. Because it was originally defined during the paper EEG era, the original definition allowed the EEG to be turned on and off at the bedside by the nurse or technologist so as to save paper. In the digital era, an analogous procedure is that the record may be reviewed in portions instead of reviewing the entire digital record, i.e., auditing a record. Another use of this code is for neonatal EEGs that may take 90 min to record quiet and active sleep and awake state. This code allows interpretation to be made after the record is completed. The present use of 95813 is for certain insurance companies that have not yet approved the use of 95951 or 95956 but will allow for 95813 for ICU EEG monitoring. Those companies have yet to update their carrier policies to the modern era of ICU EEG monitoring.

Code 95827 specifies “overnight EEG.” This code is a predecessor to polysomnography codes. It is used most commonly in sleep labs for patients receiving a full EEG during an overnight stay in order to assess for seizures as a cause of a parasomnia. It has been used for the physician interpretation of that EEG record. It is not typically used in the ICU setting but might occasionally be used when a simple overnight EEG is desired without true monitoring.

Coding requires a 24-h clock for monitoring services 95951 and 95956. Modifier 52 is used if less than 12 h is recorded. There is no clear definition of the lower limit of time for use of the 52 modifier. Hospitals should decide how they code time. In very short stays, it is most convenient to use a simple 24–h clock. If a test started at 3 PM on Tuesday and ended at 11 AM on Wednesday, code for one unit of 95951 or 95956. However, when a service is extended for several days, many hospitals and professionals often use the calendar day rule. Under this rule, each calendar day is coded separately. If a test started at 3 PM on Tuesday and ended at 11 AM on the following Monday, code for Tuesday and for the next Monday using a 52 modifier and code for Wednesday through Saturday as full days without the 52 modifier.

Reporting can be done by event, by day, or for the entire monitoring period. This is for the formal final written signed report of the monitoring itself. For ICU monitoring, the frequency of feedback to the critical care team varies with patient care needs. In some hospitals, critical care and clinical neurophysiology teams are integrated. In many others, these are two separate services that must maintain excellent communication.

Reports generally include several components. These are the time of monitoring, reason for monitoring, techniques used, interpretation of events individually or collectively, and overall impression and comments about clinical meaning of the results. In some hospitals, separate notes are entered daily. In others, the notes are cumulative with periodic updates added to the same note so that progression of change is more easily tracked over time. Any form of written note is acceptable. What is most important is to have a system in place that communicates well the EEG findings so as to integrate that into the care plan for the critical care patient.

Trending is a tool used for monitoring. Monitoring of EEG over extended periods of time in an ICU is enhanced by trending some EEG features. This substantially assists with identifying EEG variability and intermittent events. It allows the reviewing physician to more quickly find particular recording times that need focused attention. It also allows a view of EEG variability over long stretches of time, changes that might be missed if one is evaluating only the visual EEG on individual pages. Trending does not change the CPT code used. There is no additional code for the use of trending as a part of monitoring. Just as for spike and seizure detection in the EMU, these digital tools are a part of the service included in codes 95951 and 95956.

Modifier 52 is described above for flagging a 24-h service that was provided for less than 12 h.

Modifier 25 is used with the evaluation and management (E/M) code provided on the same day by the same physician as a procedure. For most carriers, it is not necessary to use modifier 25 when providing an EEG service, e.g., EEG monitoring. Occasionally, a carrier might insist on using modifier 25 with an E/M on the same day as an EEG. There is no disadvantage to doing so other than the slight additional work of entering the modifier itself while coding. Modifier 25 is required on the E/M code when also providing some other types of procedures. For example, when performing a spinal tap or trigger point injection on a patient, modifier 25 is required with an E/M procedure on the same day by the same physician.

Modifier 59 is used to identify when two different procedures in the same family of services are performed on the same day. This code signifies that the two different procedures are separate and both should be coded. For example, an inpatient EEG test might be performed in the morning, and it indicates that the patient is at risk for nonconvulsive seizures. That EEG leads to the patient being placed on continuous monitoring later the same day. Those are two separate procedures because they were separated in time. Modifier 59 is used with those procedures to identify that they are separate in time and separate procedures. Some carriers also use modifier XS in place of modifier 59 to specify that these are two separate services. Some carriers use modifier XP in place of modifier 59 if the two procedures were read by different physicians. It specifies that not only were the two procedures separate procedures and separate in time but also that they were interpreted by separate physicians. Not all carriers use the XS or XP modifiers.