Bolt of lightning – very, very frightening
Whilst it is unusual for horses to survive lightning strikes, this gelding, along with 5 stable mates, was struck by lightning whilst in his stable. Obviously, it was not a “direct” hit as the chances of survival is far less.
The gelding suffered damage to his nervous system and exhibited severe neurological abnormalities and related traumatic injuries.
From the outset, he was recumbent, blind and deaf.
He suffered damage to the vestibular system which is responsible for maintenance of the normal orientation of the trunk, limbs and eyes with respect to the position and movement of the head.
Radiographs of the head were taken to rule out fractures which could lead to similar clinical signs.
Basilar skull fractures occur when horses flip over backwards and impact their poll. These fractures, most commonly involve the basisphenoid, basioccipital and temporal bones. Basisphenoid fractures often occur at the suture (join) between the basisphenoid and basioccipital bones.
Immediately, loss of consciousness for minutes to hours is common, however some horses, may never regain consciousness. Other clinical signs include vestibular dysfunction, facial nerve paralysis, depression, haemorrhage (from ears or nostrils) and ataxia. Leakage of spinal fluid or haemorrhage from the ears indicates a fracture of the petrous temporal bones. Basisphenoid fractures can lacerate the basilar artery and can result in massive life threatening haemorrhage.
In many cases the history will provide the diagnosis. However, in some cases, the history is unknown.
Diagnostics include skull radiographs and/or endoscopic examination. These fractures usually have minimal displacement and a fracture line can be difficult to detect.
An endoscopic examination will usually reveal blood in the pharynx or guttural pouches, or haemorrhage within the walls of the upper airways.
All signs are exacerbated by blindfolding the animal.
Some abnormalities exhibited by this horse included the following:
– Variable nystagmus: horizontal, rotatory or vertical (this is abnormal movement of the eye in relation to head movement)
– General proprioceptive deficiencies (not aware of positioning of body or limbs)
– Head tilt towards or away (rare) from lesion
– Paresis (weakness)
– Cranial nerve deficits: muzzle deviation away from the affected side. Lack of menace and palpebral reflexes, ear droop, buccal impaction of feed, decreased tear production with subsequent corneal ulceration.
– Wide, swinging head movements
– Deafness (happens when the cochlear branch of cranial nerve VIII is involved bilaterally)
Prognosis is dependent on the cause of the neurological deficits. Affected animals often centrally accommodate with time and can return to their previous function, although signs can still be elucidated by blindfolding.
If blindness is present the prognosis worsens because of the loss of visual compensation for vestibular malfunction.
Associated facial and other cranial nerve deficits often remain with only a slight improvement over time. If there is even a mild improvement of facial nerve function noted in the first 4 months, full function may return.
Remember, extreme care should always be taken when riding horses with vestibular disease in reduced light situations. It can exacerbate the clinical signs or cause anxiety in the horse, which in turn could be dangerous to the rider.
This particular horse was treated symptomatically and recovered slowly over a period of 12 months. He still exhibits mild central vestibular signs, but is now a successful jumper.