Somatosensory Evoked Potentials as a Useful Tool to Limit the Temporary Clipping Time during Aneurysm Clipping

Perioperative neurological deficit is one of the known complications of cerebral aneurysm clipping procedures, leading to significant morbidity and mortality of the patients.[1] Neurological deficits noticed immediately in the postoperative period are often due to prolonged temporary or permanent clipping on adjacent vessels. Intraoperative somatosensory evoked potentials (SSEPs) have been in use to predict postoperative neurological deficits.[2]

Here is a 56-year-old male patient presenting with sudden onset of left upper limb weakness lasting for 15 minutes and complete recovery later. After further investigating with computed tomography angiography, a giant saccular aneurysm was detected in the right middle cerebral artery (MCA) of 25.5*9.92 mm in size. The patient was planned for right pterional craniotomy and clipping of the aneurysm along with SSEP monitoring. During dissection, the aneurysm appeared thrombosed; expurgation of the thrombosis was done with temporary clip placed in right internal carotid artery and MCA distal to the aneurysm. SSEPs were continuously monitored during the course. Median and posterior tibial nerve SSEPs were recorded from the scalp electrodes placed at C3 and C4. The current was applied at a voltage of 15 to 25 milliamperes, frequency of 3 Hz, and pulse duration of 300 microseconds with an average of 300 times. Alarm criteria used in this case were reduction in 50% of the amplitude or increase in the latency by 10% from baseline. After 11 minutes of temporary clipping time, a drop in the amplitude of SSEP more than 50% was observed ([Fig. 1]). In another 3 minutes, complete loss of the evoked potentials was observed both in the lower limbs and upper limbs, with a steady-state anesthesia and vitals maintained around the baseline. SSEPs returned to normal immediately after removal of the temporary clips in place. Temporary clips were reapplied after waiting for 10 minutes. Permanent clips were placed at the neck of the aneurysm and excision of the aneurysm wall was done in 7 minutes. No change in SSEP was observed at this time. Further intraoperative course was uneventful and the patient was extubated. The power in the left upper limb decreased to 4/5 in the postoperative period that recovered to baseline in 12 hours.

Fig. 1 Drop in amplitude of somatosensory evoked potential of both lower limb and upper limb indicated by arrows during temporary clipping and recovery after removal of the clipping.

The reduced blood flow during temporary clipping can cause reversible neurological changes. However, if not dealt immediately, there can be irreversible damage.[3] SSEPs can be used to monitor and identify early reversible cerebral damage to decrease the morbidity of the patients. To conclude, SSEPs monitoring must be considered in all the complex aneurysmal surgeries to limit the temporary clipping time and preventing postoperative neurological deficits.

Conflict of Interest

None declared.

• References

• 1 Krayenbühl N, Erdem E, Oinas M, Krisht AF. Symptomatic and silent ischemia associated with microsurgical clipping of intracranial aneurysms: evaluation with diffusion-weighted MRI. Stroke 2009; 40 (01) 129-133
• 2 Kashkoush AI, Jankowitz BT, Nguyen C. et al Perioperative stroke after cerebral aneurysm clipping: risk factors and postoperative impact. J Clin Neurosci 2017; 44: 188-195
• 3 Kashkoush AI, Jankowitz BT, Gardner P. et al Somatosensory evoked potentials during temporary arterial occlusion for intracranial aneurysm surgery: predictive value for perioperative stroke. World Neurosurg 2017; 104: 442-451

Publication History

Article published online:
19 November 2020