Preventing Ischemic Injury During MCA Aneurysm Clipping with SSEP Monitoring
November 22, 2025
Cerebral aneurysms are unpredictable and potentially devastating. A rupture can result in hemorrhage, stroke, or even death. Among these, middle cerebral artery (MCA) aneurysms account for roughly 20%, making them one of the most common—and most dangerous—locations for intervention.
This case demonstrates how intraoperative neuromonitoring (IONM) helped detect early signs of vascular compromise during a right MCA aneurysm clipping, allowing the surgical team to intervene before lasting deficits occurred.
Why Neuromonitoring Matters in Aneurysm Surgery
Microsurgical clipping is often the treatment of choice for ruptured or high-risk aneurysms. But temporary vessel occlusion, a standard step in these procedures, can also cut off critical blood flow. Even a few minutes of ischemia may result in sensory or motor deficits postoperatively.
Somatosensory Evoked Potentials (SSEPs) and EEG monitoring provide continuous, real-time feedback on cerebral perfusion and neural pathway integrity. This makes them invaluable for detecting reversible changes before irreversible injury occurs.
Case Study: Patient History and Surgical Plan
A 58-year-old female presented with a right MCA aneurysm suspected as the cause of subarachnoid hemorrhage within the basal cisterns and sulci. Her risk profile included uncontrolled hypertension, thrombocytopenia, tobacco abuse, and a positive methamphetamine screen—complicating the anesthetic and surgical plan.
The patient was scheduled for microsurgical clipping with intraoperative neuromonitoring. The monitoring strategy included:
- Median and tibial SSEPs to assess sensory pathways
- EEG to evaluate cortical activity and perfusion
Neurophysiology Findings Intraoperatively
During dissection, the left median SSEP showed a transient decrease that resolved with immediate adjustments. However, a more concerning change occurred shortly after placement of the temporary clip: the left median SSEP disappeared completely.
The monitoring technologist increased stimulation from 20mA to 30mA without improvement and promptly alerted the surgeon. In response, the surgeon raised the patient’s blood pressure and removed the temporary clip. Within moments, the SSEP signal returned to baseline.
When the clip was reapplied under optimized conditions, SSEPs remained stable through the remainder of the case. By closure, EEG demonstrated symmetric, continuous activity, indicating preserved cerebral function.
Why This Intervention Mattered
The transient SSEP loss indicated that the temporary clip was compromising blood flow in the MCA distribution. Without IONM feedback, this ischemic episode could have gone undetected, leading to postoperative hemiparesis, sensory deficits, or aphasia.
Instead, real-time neuromonitoring allowed:
- Early Detection of Ischemia – Identifying loss of sensory conduction within minutes
- Immediate Surgical Response – Removal and reapplication of the clip with improved hemodynamics
- Improved Patient Outcome – Preservation of neurologic function and avoidance of long-term deficits
Elevating Safety in Cerebrovascular Surgery
This case highlights the critical role of SSEPs and EEG in aneurysm clipping:
- Continuous monitoring provides a safeguard during temporary vessel occlusion
- Neuromonitoring ensures reversible changes are recognized before they cause permanent harm
- Patient outcomes improve when vascular compromise is detected and corrected intraoperatively
Make Neuromonitoring Standard in Aneurysm Cases
Temporary occlusion is sometimes necessary for safe aneurysm clipping—but it comes with risk. This case shows how quickly ischemic injury can occur, and how neuromonitoring provides the window of opportunity needed to prevent it.
For more on how intraoperative neuromonitoring can improve safety and outcomes in cerebrovascular surgery, contact our team at 888-344-2947.
