Shivering in Horses: Symptoms, Causes & Management

Shivering in horses is a neurologically caused movement disorder in which horses show sudden, involuntary twitching and trembling – particularly in the hindquarters. This condition clearly differs from other movement disorders such as stringhalt. In international usage, the term "shivering horse" is also common.

Medically speaking, shivering is a neurodegenerative disorder whose exact cause has not yet been fully clarified. Genetic predisposition, inflammatory processes, and degenerative changes in the central nervous system are among the factors discussed.

Shivering symptoms often occur when the horse is asked to back up. The hind legs are unnaturally lifted and briefly held in the air. This is often accompanied by fine muscle trembling or muscle twitching. A "freezing" of movement can also often be observed. In advanced stages, affected horses have difficulty lifting their hind legs for hoof care, or even tremble all over the body – especially in cold or stress.
This striking movement pattern differs clearly from normal trembling, which can occur, for example, due to cold or fear.

The exact cause of shivering has not yet been fully researched. It is suspected that a combination of genetic predisposition and neurological damage is the main cause. Polysaccharide storage myopathy (PSSM) and similar metabolic disorders are often suspected to be linked to shivering.
Shivering occurs particularly frequently in large warmblood and coldblood breeds; these are affected above average. Whether the condition is congenital remains unclear. However, first symptoms often appear at a young age (usually between 4 and 7 years). It is also notable that geldings and stallions are more frequently affected than mares.

Whether shivering is congenital has not yet been fully clarified. There is evidence that genetic factors play a role, as it occurs more frequently in certain breeds.

The diagnosis of shivering is made by specialized veterinarians, who use neurological examinations, movement tests, and imaging procedures if necessary. A typical sign during the examination is the uncontrolled lifting of the hind legs when backing up. Since similar symptoms can also occur with other neurological conditions, careful differential diagnosis is necessary to distinguish shivering from other diseases.
Shivering symptoms often occur only sporadically at first and can be easily overlooked. However, an early diagnosis helps to recognize the disease in time and to better manage its progression.

A veterinarian can determine, using special neurological tests and imaging procedures, whether a horse has shivering.
Shivering is a progressive condition, and its course varies from horse to horse. Symptoms may slowly worsen over years. However, many affected horses can maintain a good quality of life for many years with adapted management and care.

The life expectancy of a horse with shivering is similar to that of a healthy horse, provided the symptoms are well managed and no further complications occur. A stress-free environment is crucial in this regard. Especially for sport horses, usability in competitive sport may be limited, while leisure horses with mild symptoms often have fewer problems in everyday life.
Depending on the severity of symptoms and the quality of care, horses with shivering can reach an age comparable to that of healthy horses. With adapted care and management, the life expectancy of a horse with shivering can remain nearly normal, even if the symptoms progress over time.

There is no cure for shivering so far. Management focuses on alleviating the symptoms, with the goal of slowing the progression of the disease and maintaining the horse's quality of life. What matters most is a consistent and adapted daily management of the affected horse.

Key measures include a low-stress environment, regular, adapted exercise, and a balanced diet. The horse should ideally stay in motion daily – ideally with plenty of turnout or free movement – so that the muscles stay loose. Excitement and stress should be avoided, as they can worsen the symptoms. Regarding feeding, it is recommended to reduce or avoid starch- and sugar-rich concentrate feed (similar to PSSM management). Instead, sufficient roughage (hay) and a good mineral feed should be available. Supplementary feed with vitamin E, selenium, and magnesium can be helpful to support the muscles and reduce free radicals in the muscle. Medicinal approaches are still being researched; in individual cases, veterinarians may, for example, recommend muscle-relaxing agents or vitamins.

Hoof care also requires attention: many shivering horses have difficulty holding up their hind legs for a long time. It can be helpful to clean the hooves in short intervals and to inform the farrier about the condition. In severe cases, the horse may be lightly sedated by the veterinarian for shoeing, so the procedure can be carried out safely and with less stress.

Whether a horse with shivering can still be ridden depends on the severity of the condition. In early stages, many horses can still be ridden gently, as long as they are handled carefully and no abrupt maneuvers (such as sudden backing up or very tight turns) are demanded. It is important that the muscles are well warmed up before riding and that training is adapted to the horse's abilities. In the advanced stage, intensive sports such as show jumping or competitions are generally no longer advisable. In cases of significant coordination problems or severe trembling episodes, riding should be avoided to prevent injury to horse and rider. An experienced veterinarian should regularly assess whether and to what extent the horse remains suitable for riding. If necessary, its use as a riding horse must be limited or discontinued entirely if the animal's health would otherwise be at risk.

A shivering patient shows symptoms that partly resemble stringhalt from the outside. However, there are clear differences: Stringhalt is characterized by the sudden, uncontrolled jerking up of one hind leg while walking, with the leg immediately set back down again quickly. With shivering, on the other hand, the trembling is accompanied by poor movement coordination, and the raised leg often remains briefly in the air before being slowly set back down. In addition, with shivering, the entire hindquarters can be affected, and there is a brief "freezing" of movement – something not observed with stringhalt. Normal trembling from cold or excitement also has nothing to do with shivering syndrome and must be distinguished from it.

It is also important to rule out other neurological conditions, as they can show partly similar signs but require different causes and treatments. For example, Wobbler syndrome also causes coordination disorders, but these are due to bony narrowing in the neck region rather than a primary muscle-nerve disorder. Kissing spines (narrowing between the spinous processes of the spine) lead to back discomfort and reluctance to move, but present differently than shivering and require different treatment.