Triggered Electrooculography for Identification of Oculomotor and Abducens Nerves during Skull Base Surgery.

OBJECTIVE: Electrooculography (EOG) records eyeball movements as changes in the potential difference between the negatively charged retina and the positively charged cornea. We aimed to investigate whether reliable EOG waveforms can be evoked by electrical stimulation of the oculomotor and abducens nerves during skull base surgery. METHODS: We retrospectively reviewed the records of 18 patients who had undergone a skull base tumor surgery using EOG (11 craniotomies and seven endonasal endoscopic surgeries). Stimulation was performed at 5 Hz with a stimulus duration of 200 µs and an intensity of 0.1-5 mA using a concentric bipolar probe. Recording electrodes were placed on the upper (active) and lower (reference) eyelids, and on the outer corners of both eyes; the active electrode was placed on the contralateral side. RESULTS: Reproducibly triggered EOG waveforms were observed in all cases. Electrical stimulation of cranial nerves (CNs) III and VI elicited positive waveforms and negative waveforms, respectively, in the horizontal recording. The median latencies were 3.1 and 0.5 ms for craniotomies and endonasal endoscopic surgeries, respectively (p=0.007). Additionally, the median amplitudes were 33.7 and 46.4 µV for craniotomies and endonasal endoscopic surgeries, respectively (p=0.40). CONCLUSION: This study showed reliably triggered EOG waveforms with stimulation of CNs III and VI during skull base surgery. The latency was different according to the point of stimulation and thus predictable. As EOG is noninvasive and relatively easy to perform, it can be used to identify the ocular motor nerves during surgeries as an alternative of electromyography.

Acute post-operative airway complications following anterior cervical spine surgery and the role for cricothyrotomy.

Anterior cervical spine surgery (ACSS) is a common procedure, but not without its own risks and complications. Complications that can cause airway compromise occur infrequently, but can rapidly lead to respiratory arrest, leading to severe morbidity or death. Knowing emergent post-operative airway management including surgical airway placement is critical. We aim to review the different etiologies of post-operative airway compromise following ACSS, the predictable timeline in which they occur, and the most appropriate treatment and management for each. We place special emphasis on the timing and proper surgical technique for an emergent cricothyrotomy. Angioedema is seen the earliest as a cause of post-operative airway compromise, typically within 6-12 hours. Retropharyngeal hematomas can be seen between 6-24 hours, most commonly within 12 hours. Pharyngolaryngeal edema is seen within 24-72 hours. After 72 hours, retropharyngeal abscess is the most likely etiology. Several studies have utilized delayed extubation protocols following ACSS based on patient risk factors and found reduced postoperative airway complications and reintubation rates. The administration of perioperative corticosteroids continues to be controversial with high-level studies recommending both for and against their use. Animal studies showed that after cardiac arrest, the brain can recover if oxygenation is restored within 5 minutes, but this time is likely shorter with asphyxia prior to cardiac arrest. Experience and training are essential to reduce the time for successful cricothyrotomy placement. Physicians must be prepared to diagnose and treat acute postoperative airway complications following ACSS to prevent anoxic brain injury or death. If emergent intubation cannot be accomplished on the first attempt, physicians should not delay placement of a surgical airway such as cricothyrotomy.