Find policies, billing codes, payers, states, and providers
Grid Monitoring and Intraoperative Electroencephalography
Customize your policy alerts
Sign up for Aetna Policy 0289 alerts
Get alerted when Policy 0289 changes without checking for updates manually.
Monitor payer policy activity
Defines Aetna's medical necessity, investigational indications, coding references, and limitations for intraoperative scalp EEG and invasive grid (electrocorticography, ECoG) monitoring; applies to clinicians and facilities providing perioperative neurophysiologic monitoring and epilepsy surgical evaluation.
No material clinical or coverage changes in this revision.
Coverage Criteria
inv-01: Intraoperative scalp EEG — Medically necessary
Covered when ANY of the following indications are present:
Presence of this indication alone meets medical necessity for intraoperative scalp EEG.
Presence of this indication alone meets medical necessity for intraoperative scalp EEG.
Presence of this indication alone meets medical necessity for intraoperative scalp EEG.
inv-02: Grid monitoring (ECoG) — Medically necessary
Covered when ANY of the following are met in members with intractable seizures:
Any one of these conditions in a patient with intractable seizures supports medical necessity for grid monitoring (ECoG).
Any one of these conditions in a patient with intractable seizures supports medical necessity for grid monitoring (ECoG).
Any one of these conditions in a patient with intractable seizures supports medical necessity for grid monitoring (ECoG).
inv-03: Experimental and Investigational
Not medically necessary because clinical value has not been established for the following:
Considered investigational due to insufficient evidence of clinical value.
Considered investigational because clinical value has not been established.
Considered investigational because clinical value for other indications has not been established.
inv-04: Evidence summaries supporting intraoperative ECoG and mapping
Findings from cited case series and retrospective studies supporting use:
Authors concluded intraoperative ECoG provided exact location of epileptogenic areas and improved postoperative seizure control.
Supports use of awake mapping plus ECoG for lesions near eloquent cortex.
Illustrates utility of mapping and ECoG to identify symptom-correlated cortex and guide resection.
The policy specifies that the use of intraoperative EEG to monitor brain function for anesthetic drug administration (for example, limited‑channel devices such as BIS) is considered integral to the anesthesia service and not separately reimbursed. The document further notes that one‑ or two‑channel EEG devices do not meet minimal technical EEG requirements and that such use is considered experimental and investigational when billed separately.
A Medicare National Coverage Determination and an AAN assessment are cited regarding EEG in cardiac surgery: the CMS NCD states that the value of EEG monitoring during open‑heart surgery is debatable and not an established indication, and the policy treats intraoperative EEG for open‑heart surgery as experimental and investigational. As a result, use of intraoperative EEG for open‑heart surgery is not among the medically necessary indications listed in this policy and may be denied.
The policy references multiple studies documenting procedure‑related risks of invasive monitoring, including reports of complications associated with subdural grid placement and other invasive electrode monitoring. Examples cited include pediatric and adult series describing subdural electrode‑associated complications, seizure‑related intracranial pressure elevations, and surgical morbidity of invasive monitoring, indicating that invasive grid/depth electrode monitoring carries nontrivial procedural risks that should be considered and documented.
Aetna considers intraoperative EEG uses that are not listed as medically necessary — for example, intraoperative EEG for prediction of post‑operative delirium — to be experimental and investigational because their clinical value has not been established. Such indications are therefore considered not medically necessary under this policy.
Within the referenced sections and citations, there are literature listings and reference notes but no standalone, explicit statements formatted as 'not medically necessary' beyond the investigational classifications already described; the policy frames unlisted uses as experimental/investigational rather than presenting separate explicit 'not medically necessary' declarations in these chunks.
Coding and Billing
| 95812 | Electroencephalogram (EEG) extended monitoring; 41-60 minutes. |
| 95813 | Electroencephalogram (EEG) extended monitoring; greater than 1 hour. |
| 95822 | Electroencephalogram (EEG); recording in coma or sleep only. |
| 95940 | Continuous intraoperative neurophysiology monitoring in the operating room, one on one monitoring requiring personal attendance, each 15 minutes (List separately in addition to code for primary procedure). |
| 95941 | Continuous intraoperative neurophysiology monitoring, from outside the operating room (remote or nearby) or for monitoring of more than one case while in the operation room, per hour (List separately in addition to code for primary procedure). |
| 95955 | Electroencephalogram (EEG) during non-intracranial surgery (eg, carotid). |
| 95829 | Electrocorticogram at surgery (separate procedure). |
| 61531 | Subdural implantation of strip electrodes through one or more burr or trephine hole(s) for long term seizure monitoring. |
| 61533 | Craniotomy with elevation of bone flap; for subdural implantation of an electrode array, for long-term seizure monitoring. |
| 61535 | Removal of epidural or subdural electrode array, without excision of cerebral tissue (separate procedure). |
| 61760 | Stereotactic implantation of depth electrodes into the cerebrum for long term seizure monitoring. |
| 95961 | Functional cortical and subcortical mapping by stimulation and/or recording of electrodes on brain surface, or of depth electrodes, initial hour of attendance by a physician or other qualified health care professional. |
| 95962 | Each additional hour of attendance by a physician or other qualified health care professional (List separately in addition to code for primary procedure). |
| 95812-95830 | Electroencephalography (EEG) range referenced. |
| 95954-95967 | Special EEG Tests range referenced. |
| S8040 | Topographic brain mapping. |
| G40.00 - G40.919 | Epilepsy and recurrent seizures. |
| R56.1 | Post traumatic seizures. |
| R56.9 | Unspecified convulsions. |
| C71.3 | Malignant neoplasm of parietal lobe. |
| C79.31 | Secondary malignant neoplasm of brain. |
| D33.0 | Benign neoplasm of brain, supratentorial. |
| D43.0 | Neoplasm of uncertain behavior of brain, supratentorial. |
| D49.6 | Neoplasm of unspecified behavior of brain. |
| G93.89 | Other specified disorders of brain (lesion near the eloquent cortex). |
| F05 | Delirium due to known physiological condition (post-operative delirium). |
| 95812 | Electroencephalogram (EEG) extended monitoring; 41-60 minutes. |
Provider Actions & Documentation Requirements
Prior Authorization Not Specified
Prior authorization is not specified in the provided policy text for intraoperative EEG or grid monitoring. Providers should verify any payer-specific PA requirements separately before scheduling but the policy itself does not list PA triggers.
- No prior authorization specified in policy text
Non‑reimbursable: Anesthetic Depth Monitoring
Intraoperative EEG used solely to monitor anesthetic depth or to guide anesthetic drug administration is considered integral to anesthesia and is not separately reimbursable. This use is also identified in the policy as experimental/investigational and claims for anesthetic depth monitoring may be denied.
- Intraoperative EEG for anesthetic depth: not reimbursable; considered integral to anesthesia
- Policy labels this use experimental/investigational
Clinical Justification Required for Invasive Monitoring
When invasive monitoring (subdural grid or depth electrodes) is proposed, clinical justification must document why noninvasive scalp EEG and other noninvasive modalities were insufficient to localize the epileptogenic focus, and describe the expected diagnostic or therapeutic benefit. Documentation should include seizure history, prior EEG/scalp monitoring results, concordance/discordance with imaging, and rationale for invasive electrode type and planned monitoring duration.
- Document prior noninvasive EEG findings and why they were inadequate
- Describe concordance/discordance with imaging and other studies
- Specify planned electrode type (subdural grid vs depth), number of contacts, and anticipated monitoring period
Indications and Supporting Studies
Indications supported by the policy and cited studies should be documented: intraoperative scalp EEG is medically necessary for cerebral function monitoring during carotid artery surgery, intracranial vascular procedures, and parietal tumor or lesions near eloquent cortex. Grid monitoring (ECoG) is considered medically necessary for localization in intractable epilepsy when seizures arise from functionally important areas, when scalp EEG fails to localize, or when there is discordance among studies. Cite supporting literature (AAN assessments, CMS NCD, and relevant surgical series) when applicable.
- Scalp EEG indications: carotid surgery; intracranial vascular surgery; parietal tumor or lesions near eloquent cortex
- ECoG indications: intractable seizures with functional area involvement; inadequate scalp EEG localization; discordant neurodiagnostic studies
- Supporting evidence: AAN technology assessment, CMS NCD, and case series/retrospective studies (e.g., Yao 2018, Maesawa 2018)
Escalation to Invasive Monitoring
Escalation from noninvasive scalp EEG to invasive monitoring should be documented as a deliberate clinical decision when scalp EEG monitoring is insufficient for localization or functional mapping. The record should show attempts or results of long‑term scalp EEG/video monitoring, reasons scalp data were inadequate, and why subdural grids or depth electrodes are expected to provide additional, actionable information for surgical planning.
- Show prior scalp EEG/video monitoring and why it failed to localize
- Explain how invasive monitoring will change management (e.g., enable resection, preserve eloquent cortex)
No Step Therapy Requirements Specified
The policy does not impose any step‑therapy requirements for intraoperative EEG or grid monitoring.
- No step therapy specified in policy text
Background
Scalp electroencephalography (EEG) records cortical electrical activity via electrodes applied to the head and is commonly used to establish seizure disorders and to monitor cerebral function perioperatively. In the intraoperative context, scalp EEG is indicated for monitoring cerebral function during carotid artery surgery, intracranial vascular procedures, and parietal tumor resections or lesions near eloquent cortex. For patients with intractable seizures when scalp recordings are insufficient to localize the epileptogenic zone, invasive techniques such as subdural grid electrodes (electrocorticography, ECoG) or depth electrodes may be used to record and stimulate cortex for localization and functional mapping to guide resection.
Definitions
OpenPayer is powered by Trek Health's payer performance platform. Trek continuously ingests, validates, and normalizes Transparency in Coverage data alongside payer policies and other commercial payer data to create a structured payer intelligence foundation. OpenPayer uses this foundation to deliver personalized search results, dynamically generated policy pages, and tailored policy monitoring based on each user's payers, specialties, billing codes, and areas of interest. The same intelligence powers broader payer performance workflows, including reimbursement benchmarking, contract evaluation, payer negotiations, and financial decision-making.