Unilateral blindness following superior laryngeal nerve block for awake tracheal intubation in a case of posterior cervical spine surgery

Background: Superior laryngeal nerve block (SUPLANEB) is a popular airway anesthesia technique utilized for successful awake endotracheal intubation in patients with significant cervical spine instability. If not performed by an expert, it carries the risk of general/neurologic complications that are typically minimal/transient. However, permanent blindness and/or upper cranial nerve neuropathies may occur. Here, we describe a case in which a young patient underwent an atlantoaxial fusion for a C2 nonunion (e.g., following a fracture) complicated by unilateral blindness due to a SUPLANEB.

Case description: A 25-year-old neurologically intact male underwent a C1-C2 posterior arthrodesis to address a nonunion of a C2 fracture. To perform the awake nasotracheal intubation, a SUPLANEB was performed using a video laryngoscope. Although the operation was uneventful, postoperatively, the patient reported left visual loss accompanied by left-sided facial numbness and hearing loss. On examination of the left eye, the anterior segment and fundus examinations were normal, but the OCT (optical coherence tomography) and retinal angiography demonstrated left-sided postischemic retinal edema with permeability of the intraocular vessels. Although the cranio-orbital computed tomography scan showed only mild pneumocephalus, the CT angiogram scan revealed abnormal air in the left carotid sheath accompanied by diffuse subcutaneous emphysema. Further, brain and orbital magnetic resonance imaging scans were normal. The patient was treated with pure oxygen, systemic steroid therapy, and nimodipine. The pneumocephalus and subcutaneous emphysema resolved on day 3. At 2 months follow-up, the patient remained blind on the left side, but had no further neurological deficits.

Conclusion: Blindness and upper cranial nerves neuropathies should be considered as potential complications of SUPLANEB. Notably, these deficits were not directly related to the operative positioning or neurosurgical spinal procedure.

Keywords: Anesthesia; Blindness; Complication; Pneumocephalus; Spinal surgery; Superior laryngeal block.