Trembling in dogs – causes, investigations and treatment

Overview

Tremor describes movement, rather than a diagnosis

A true tremor means involuntary, rhythmic back-and-forth movement of a body part. It may be confined to the head or a limb, for example, or involve the whole body. Rhythmicity distinguishes tremor from many other involuntary muscle movements. Not every twitch an owner describes as trembling therefore belongs to the same movement disorder.

Generalised trembling may be caused by poisoning, inflammatory disease or a metabolic disturbance. IGTS means idiopathic generalised tremor syndrome, also called shaker syndrome. Its exact cause remains unknown.

Tremor can result from alternating contractions of muscles acting in opposite directions. Generalised tremor affects both the forelimbs and hindlimbs.

Causes

Cold, pain and a stressful situation

Shivering in the cold indicates that a dog is no longer tolerating the conditions well. Anxiety can also involve trembling alongside other behavioural signs. Pain-related trembling may occur with body tension or avoidance of touch. The explanation is therefore assessed from the setting and other signs.

Poisoning and internal disturbances

Among 198 dogs investigated for generalised tremors in specialist care, 91, or 46%, were diagnosed with poisoning. IGTS was diagnosed in 49 dogs, or 24.7%. Low blood calcium was responsible in 13 dogs, or 6.6%. Low blood glucose explained signs in 6 dogs, or 3%. Causes of poisoning included mould toxins and metaldehyde.

High blood calcium can also cause trembling: it was diagnosed in 5 of the 198 dogs, or 2.5%. Inflammation of the brain and meninges of unknown origin was responsible in 9 dogs, or 4.5%. Other identified causes included brain dysfunction associated with a liver vascular shunt and hereditary degenerative diseases.

IGTS and the immune system

IGTS is suspected to involve abnormal immune system activity. Antibodies targeting nervous system structures were found in 5 of 30 dogs tested in a study. The immune reaction is thought potentially to cause mild cerebellar inflammation. The cerebellum helps coordinate movements, meaning the movements of different body parts work together.

Risk factors

IGTS usually starts in a young adult dog, often at 1–2 years of age. It was originally described in breeds including the Maltese, West Highland White Terrier and Bichon Frise. The syndrome can nevertheless affect dogs of any colour or size. Being a small white dog is therefore not a diagnostic requirement.

Across all causes of generalised tremor, the age range is much wider: the median age at onset in the 198-dog study was 3.2 years. The youngest was 3 months and the oldest 14.3 years. Small, short-haired, elderly and underweight dogs are particularly vulnerable to cold.

IGTS is not confined to the youngest dogs: one IGTS group had an onset range of 0.3–10.0 years. Puppies' limited body fat and immature temperature regulation increase the harmful effects of cold.

Typical symptoms

The appearance of trembling and associated signs help guide investigations. You may notice the following at home:

• The head, limbs or whole body move rhythmically without purposeful movement.
• Trembling intensifies during movement or excitement, as in many dogs with IGTS.
• Trembling makes eating or ordinary walking difficult.
• Your dog wobbles or holds their head tilted.
• The eyes show involuntary back-and-forth movement, called nystagmus.
• Poisoning may involve unusual drooling or altered consciousness.

Of the 198 dogs studied, 173, or 87.4%, had continuous tremors and 25, or 12.6%, had episodic tremors. IGTS signs may ease at rest or disappear during sleep. The end of an episode does not, however, establish its cause.

Complications and consequences

Consequences of trembling and its causes

Severe trembling can prevent normal walking and eating. If shivering in the cold continues, exposure can lead to life-threatening hypothermia. Identifying the underlying cause is therefore essential even when the movement itself looks similar.

Persistent pain can reduce movement and weaken muscle condition. Neuromyotonia, prolonged muscle stiffness associated with peripheral nerve hyperexcitability, can cause stiffness severe enough to make a dog collapse.

Cold exposure can also cause frostbite, particularly of the ears, paws and tail tip. The full extent of frostbite is not always immediately visible and may become apparent only over several days.

Relapse in IGTS

Follow-up of 33 dogs with IGTS found no relapse in 18, or 55%. Controlled relapses occurred in 8 dogs, or 24%. The outcome remained unknown in 7 dogs, or 21%. Median follow-up was 5 months.

Diagnosis at the vet

Characterising the movement and initial tests

Your vet establishes whether trembling occurs at rest, while standing or during purposeful movement. In resting tremor, the affected body part is not actively maintaining posture against gravity. Orthostatic tremor appears in the limbs during standing and disappears during movement or lying down. Action tremor is associated with voluntary movement. These observations help define the possible movement disorder.

A video helps assess movement if the dog has no signs at the consultation. Blood and urine tests investigate diseases such as kidney or liver disease. Blood glucose and calcium are important for identifying possible metabolic causes. Suspected infection may prompt testing for distemper, for example.

Neurological examination assesses alertness, movement, proprioception, reflexes and pain sensation, among other functions.

Further neurological investigations

Neurological examination helps locate disease within the nervous system. Brain MRI assesses brain tissue structure. A cerebrospinal fluid sample is collected under anaesthesia. It can be checked for inflammatory cells and signs of infection.

Normal cerebrospinal fluid does not rule out IGTS: 20 of 33 affected dogs, or 61%, had a normal sample. Not every trembling dog needs MRI and cerebrospinal fluid sampling. IGTS is a diagnosis of exclusion requiring assessment of other medical causes of tremor.

Movements resembling tremor

Myoclonus means brief, electric shock-like jerks that may occur in a series. These are more abrupt than the steady back-and-forth movement of tremor. Myoclonus can also occur during sleep. An electroencephalogram, or EEG, recorded during an episode may help classify it.

A fasciculation is a brief contraction of a small group of muscle fibres, visible as local twitching beneath the skin. In myokymia, the skin over muscle may appear to ripple like a worm. Electromyography, or EMG, can distinguish myokymia from neuromyotonia. Neuromyotonia involves continuous muscle stiffness and delayed relaxation.

Muscle twitching associated with peripheral nerve hyperexcitability may be localised or generalised. Its frequency can vary, whereas true tremor has a regular rhythm.

Treatment

Treatment follows the identified cause

Poisoning may require veterinary fluid treatment and measures addressing the exposure. In pain-related trembling, treatment targets the cause of pain. A dog shivering in the cold is moved to a warm, dry place. Suspected hypothermia requires immediate veterinary assessment.

IGTS treatment and follow-up

IGTS is treated with a corticosteroid that suppresses immune system activity. A muscle-relaxing medicine may also reduce tremors where needed. If the response is incomplete or adverse effects are problematic, your vet may consider other immune-suppressing medication. Medicines are selected by your vet according to the diagnosis.

In many dogs, IGTS tremors resolve completely within 1–2 weeks of starting treatment. This describes reduction of signs, rather than when medication should stop. Some dogs later manage without medication, while others need long-term treatment. A corticosteroid can increase appetite, thirst and urination. Long-term use may also cause adverse effects involving the skin, hormonal function or immune system.

Treating pain and anxiety

Alongside pain medication, care may include rehabilitation, physiotherapy, weight management and adjustment of everyday activity demands. Behaviour modification for anxiety is planned according to the underlying problem. Some dogs also need anti-anxiety medication selected by a vet. A predictable routine forms part of care even when medication is used.

Prevention

Not every cause of trembling can be prevented: no reliable means of preventing IGTS is known. Cold exposure can be reduced by limiting time outdoors according to the dog's tolerance. Clothing may help a small, elderly or thin-coated dog retain warmth.

A predictable daily routine can reduce stress in an anxious dog. Training rewards desired behaviour rather than using harsh punishment. Persistent pain needs treatment because chronic pain does not usually resolve on its own.

Important for dog owners

Recording observations

Record the trembling safely and note the situation in which it started. Separately record whether movement makes it worse and whether it settles at rest. Also note whether your dog can eat and walk normally. This helps monitoring reflect the effect on daily life.

Mention possible toxin exposure as soon as you contact the practice. During IGTS medication, monitor increased drinking and urination. Arrange follow-up with the treating vet to monitor medication effects and adverse effects. Willingness to play does not rule out pain: some dogs continue playing despite it.

Other signs of feeling cold include lifting the paws and reluctance to continue walking. In a noise-sensitive dog, distress associated with trembling may continue after a sudden sound has ended. Record when the situation ended and how your dog recovered as well.

Frequently asked questions

Why does my dog tremble when they are not cold?

Trembling can be associated with pain or anxiety. Medical causes include poisoning and low blood glucose. IGTS can also cause whole-body trembling. A new unexplained sign is investigated by a vet because similar-looking movements can have different underlying causes.

Does shaker syndrome only affect small white dogs?

No. IGTS can affect a dog of any size or colour. The older name relates to the syndrome initially being described in small white breeds. Diagnosis relies on excluding other medical causes. Coat colour therefore does not replace examination.

Is trembling always an epileptic seizure?

Trembling can be caused by many other diseases, such as low calcium or poisoning. A regular rhythm is central to a true tremor. Video can help your vet identify the nature of the signs. Using the word trembling at home does not yet establish the movement disorder or disease involved.

How quickly does IGTS treatment help?

Many dogs' tremors disappear within 1–2 weeks of starting treatment. Medication may nevertheless be needed longer, and some dogs need long-term treatment. Signs can also return after medication stops. Freedom from signs and the end of treatment are therefore different matters.

Does a normal blood or fluid test rule out IGTS?

Blood and urine tests look for other diseases explaining the trembling. Cerebrospinal fluid can also be normal in IGTS: 20 of 33 affected dogs had a normal result. Your vet assesses the need for further tests using the pattern of signs and other findings.