Delayed onset vagus nerve paralysis after occipital condyle fracture in a horse.

This study documents a unique case, where a 7-year-old horse developed late nerve paralysis following a minor head injury, leading to difficulty in swallowing. A fracture in the occipital condyle – a protrusion connecting the skull to the spine – was determined as the cause of this condition. This specific occurrence in horses could serve as a valuable sign for veterinarians in diagnosing fractures in this region.

Background and Case Presentation

• The horse in question, a Friesian breed, presented difficulty in swallowing (dysphagia), which developed several days following a minor head injury. This led the researchers to suspect paralysis in two of the horse’s cranial nerves – the vagus nerve (CNX) and the glossopharyngeal nerve (CNIX).
• An endoscopic examination of the horse revealed a condition called right laryngeal hemiplegia and intermittent dorsal displacement of the soft palate. Laryngeal hemiplegia is typically characterized by dysfunction in the larynx, while dorsal displacement of the soft palate is a shifting of soft tissue in the upper part of the throat.
• In addition, a submucosal hemorrhage (Bleeding under the mucosal lining) and raised area were identified on the dorsal (upper) aspect of the medial compartment of the right guttural pouch, which is an air-filled space in the horse’s head.

Diagnosis and Findings

• A radiological examination was performed in the upper neck region of the horse. It revealed a misalignment of the atlas – the topmost vertebra of the spine which enables head movement – and a large bone fragment located above the guttural pouches.
• Based on these observations, the case was diagnosed as an occipital condyle fracture paired with a delayed onset of cranial nerve paralysis. The delayed onset nerve paralysis was considered as the cause of the horse’s dysphagia.

Implications of the Research

• This research note aims at raising awareness about the potential link between cranial nerve paralysis and occipital condyle fractures in horses. It especially highlights the significance of evaluating the atlanto-occipital articulation (ie., joint between the skull and spine) and skull base in horses exhibiting dysphagia following a head injury.
• The onset of cranial nerve paralysis causing difficulty in swallowing may serve as a noticeable symptom of occipital condyle fracture in horses, thereby aiding in timely diagnosis and treatment.