Damage to the dorsal buccal branch of the facial nerve can result in nasal collapse and difficulty breathing. | Courtesy Dr. Rubén Anguiano

To be able to breathe, a horse’s nostrils and nasal passages must open and close normally. The dorsal buccal branch of the facial nerve innervates these important structures. Thus, neurologic dysfunction can result in nasal collapse and difficulty breathing.

Nasal Collapse Etiology

Neurologic dysfunction of the facial nerve’s dorsal buccal branch can occur for a variety of reasons, including:

• Accidental head trauma;
• Brutality and mistreatment;
• Lack of proper head protection during general anesthesia in lateral recumbency; and
• Iatrogenic conditions, or those inadvertently caused by veterinary care. For example, the veterinarian might accidentally damage the nerve trunk during tooth extractions or procedures to correct overbites or repair maxillary (upper jaw or cheek) fractures.

Case Report

An 18-month-old Andalusian colt developed severe respiratory distress because he could not open his nostrils properly during inspiration. A veterinary exam revealed that the lateral side of the alar cartilage (a ring of cartilage that holds the nostrils open during inhalation) had collapsed inside the nose. Veterinarians learned that the colt had been tied to a post while wearing a bosal during training. At some point, he suffered trauma from the bosal and a martingale, which had resulted in the bilateral nasal passage compression. His caretakers detected his respiratory distress the next day