RT Book, Section A1 Stark, Christopher L. A2 Knoop, Kevin J. A2 Stack, Lawrence B. A2 Storrow, Alan B. A2 Thurman, R. Jason SR Print(0) ID 1181038132 T1 Facial Nerve Injury T2 The Atlas of Emergency Medicine, 5e YR 2021 FD 2021 PB McGraw-Hill PP New York, NY SN 9781260134940 LK accessemergencymedicine.mhmedical.com/content.aspx?aid=1181038132 RD 2024/11/09 AB Facial paralysis can be a devastating consequence of blunt or penetrating trauma. The facial nerve is injured in 7% to 10% of temporal bone fractures. After facial nerve injury, the ensuing paralysis is immediate in 27% of cases and has a delayed presentation in 73% of patients. Penetrating trauma can occur anywhere along the nerve tract but is especially vulnerable after it exits the skull, just posterior to the styloid process of the temporal bone, traveling anterior to the external ear to the parotid gland. Within the gland, the nerve terminates splitting into five branches. Injury to the nerve extracranially causes purely motor deficits to the muscle of facial expression. Intracranial injury, proximal to the stylomastoid foramen, produces mixed motor and sensory deficits. The signs and symptoms differ depending on the distance from the origin of the nerve and any branches from the nerve before and after the area of injury. Possible deficits include ipsilateral hyperacusis (sound hypersensitivity); ipsilateral loss of taste to the anterior two-thirds of the tongue; reduced parasympathetic innervation to the mucus glands of the oral cavity, nose, and pharynx (decreasing salivation); ipsilateral reduced lacrimal fluid production; and motor paresis as seen with extracranial injury.