From the Guidelines
Direct visualization and intraoperative neurophysiological monitoring are the most recommended methods for nerve monitoring during carotid endarterectomy to minimize the risk of nerve injury. Several nerve monitoring methods are recommended during carotid endarterectomy to minimize nerve injury risk. Direct visualization remains the primary approach, where surgeons carefully identify and preserve cranial nerves X, XII, and the marginal mandibular branch of VII throughout the procedure. Intraoperative neurophysiological monitoring is highly beneficial, including continuous somatosensory evoked potentials (SSEPs) to detect cerebral ischemia and electromyography (EMG) with needle electrodes placed in relevant muscles to detect nerve irritation. Intermittent direct nerve stimulation using a handheld probe (typically 0.5-2.0 mA) can verify nerve integrity and function during critical dissection phases. Some centers employ continuous laryngeal nerve monitoring using endotracheal tube-mounted electrodes that detect vocal cord movement when the recurrent laryngeal nerve is stimulated. Local anesthesia with an awake patient allows real-time neurological assessment through speech and movement tests, providing immediate feedback about potential nerve dysfunction. These monitoring techniques are complementary rather than mutually exclusive, with the combination of direct visualization and electrophysiological monitoring offering the most comprehensive nerve protection. The choice of monitoring should be tailored to institutional expertise, with the goal of early detection of potential nerve injury when intervention might prevent permanent damage 1.
Some key points to consider:
- Carotid endarterectomy is a procedure that carries risks, including neurological and nonneurological complications, such as hypertension or hypotension, hemorrhage, acute arterial occlusion, stroke, MI, venous thromboembolism, cranial nerve palsy, infection, arterial restenosis, and death 1.
- The risk of stroke or death is related mainly to the patient’s preoperative clinical status, with symptomatic patients having a higher risk than asymptomatic patients 1.
- The benefits of carotid endarterectomy over medical management in randomized trials were conveyed by low perioperative complication rates, achieved by high-volume surgeons in low-risk patients 1.
- Early carotid endarterectomy is believed to reduce the risk of recurrent stroke, and data indicate that patients who are neurologically stable after presenting with a nondisabling stroke or TIA may undergo surgery early on without any incremental risk compared with delayed surgery 1.
Overall, the most effective approach to nerve monitoring during carotid endarterectomy involves a combination of direct visualization and intraoperative neurophysiological monitoring, tailored to institutional expertise and the individual patient's needs.
From the Research
Nerve Monitoring Methods
The following methods are recommended for nerve monitoring during carotid endarterectomy to minimize the risk of nerve injury:
- Somatosensory evoked potentials (SEPs) and motor evoked potentials (MEPs) in conjunction with electroencephalography (EEG) 2
- Multichannel somatosensory evoked potentials (SEPs) after median nerve stimulation at wrist, recording from 2nd cervical and from the scalp parietal and central positions 3
Prevention of Nerve Injury
Prevention of nerve injury during carotid endarterectomy can be achieved by:
- Knowledge of regional anatomy and the mechanisms of nerve injury 4
- Minor modifications in technique to avoid nerve injury 4
- Routine examination of patients before and after surgery by a neurologist to identify cranial nerve injuries 5
Risk of Cranial Nerve Injury
The risk of cranial nerve injury after carotid endarterectomy is:
- 5.1% of patients, with 3.7% of patients having a residual cranial nerve injury 5
- 0.5% of patients having a deficit that persists beyond hospital discharge 5
- Accessory nerve injury is rare, with an incidence of 0.47% 6
Mechanisms of Nerve Injury
The mechanisms of nerve injury during carotid endarterectomy include: