What is Claude Bernard Horner syndrome in dogs?
Claude Bernard Horner syndrome is a neurological disorder of sympathetic ocular innervation which manifests itself in dogs by ophthalmological disorders. This syndrome is caused by dysfunction of the sympathetic nerves in the eyes and surrounding facial muscles that normally help control eye blinking or muscle tone.
The condition usually comes on suddenly and usually affects one side of the head but can be bilateral if the nerve damage is located between the hypothalamus and the nerve roots from T1 to T3.
What causes Horner's syndrome?
In 50-90% of cases in dogs, Claude Bernard Horner syndrome is often classified as idiopathic, meaning it has no known cause. Labradors are thus racially predisposed to this condition like Cockers, Collies and Golden Retrievers.
In other cases, Claude Bernard Horner syndrome can be secondary:
- to hypothalamic lesions caused by tumor or trauma,
- brain stem lesions, caused by tumour, infection, trauma or inflammatory process,
- to spinal cord injuries following trauma, herniated disc or fibrocartilaginous embolism,
- nerve root damage between T1 and T3 in the event of avulsion of the brachial plexus (tearing of a nerve following a trauma),
- lesions of the sympathetic trunk and the cranial cervical ganglion occurring as a result of trauma, surgery or the development of a mediastinal tumor,
- middle ear damage following otitis, trauma, development of a tumor or nasopharyngeal polyp,
- retrobulbar lesions secondary to trauma or the presence of a tumor or abscess.
How does Claude Bernard Horner syndrome manifest in dogs?
The most common clinical signs of Claude Bernard Horner syndrome are:
- a ptosis (sagging) of the upper eyelid,
- a narrowed pupil (miosis),
- a third eyelid that appears red and raised on the eye,
- redness of the conjunctiva,
- an eye that looks more sunken (enophthalmos).
Other symptoms may accompany ophthalmological signs. They vary depending on the location of the nerve damage and can include, among other things, vestibular syndrome or paralysis of the limbs.
What is the treatment for Claude Bernard Horner syndrome?
Treatment depends on the causative condition.
Thus, if your dog has Claude Bernard Horner syndrome, several diagnostic tests may be indicated among eye and ear exams, cervical x-rays, and possibly a brain scan or MRI. Tests may include the instillation of neosynephrine drops placed in the affected eye to help locate the source of the problem.
However, most cases of Horner's syndrome are idiopathic and can be treated with symptomatic treatment using eye drops.
If no underlying pathological cause is present, the problem tends to resolve spontaneously, but it may take weeks or months depending on its severity.