Neck and back pain

Pain is a perception ― rather than a quantifiable entity ― resulting from a noxious stimulus.

Hyperaesthesia describes an increased sensitivity to a normal level of stimulation, noted by the behavioural reaction of an animal; this is commonly seen when the animal’s spine is palpated during a physical examination.

Hyperpathia is the behavioural response to an injurious or noxious stimulation.

Many diseases encountered in veterinary medicine cause spinal pain, including multiple neurological diseases, as well as non-neurological diseases such as polyarthritis. Lesion localization is very important in cases of spinal pain, in order to ensure that the correct diagnostics are performed. In addition, interpretation of test results will only be possible with the knowledge of the results of the neurological examination. The treatment of spinal pain must be addressed both by treating the underlying disease and through the pharmacological alleviation of discomfort ().

Clinical signs

Recognition of the signs of spinal pain in animals can be made difficult by the variable reaction to pain seen between individuals. Some animals may give no outward indication that they are in pain, but there are several clinical signs that may be present and are useful for determining the presence of neck and back pain (Clinical signs associated with neck or back pain). Neck pain can be intermittent because of the dynamic nature of the cervical spine. In these cases, an accurate history in addition to video recordings of the episodes can be very helpful.

Clinical signs associated with neck or back pain

  • Decreased general activity levels
  • Depressed mentation
  • Change in normal attitude (i.e. aggression, withdrawal) and unexplained vocalization
  • Ventroflexion of neck
  • Stiff neck posture
  • Increased cervical muscle tone
  • Intermittent jerks or spasms of neck related to movement
  • Pain on palpation of vertebrae and spinal musculature
  • Pain on dorsal and lateral flexion of the cervical vertebrae
  • Gait abnormality: thoracic limb lameness (nerve root signature); stilted gait; stiff limbs; paresis if concurrent spinal cord disease
  • Historical reluctance to go up and down stairs, to climb into a vehicle or on to furniture, or to jump up
  • Historical observation of difficulty to get into resting position; may seem restless
  • Autonomic signs (e.g. salivation, increased respiratory and heart rates, pupillary dilation)
  • Unwillingness or inability to drink or eat from bowls on the floor

Lesion localization

Spinal pain may result from disease of any of the numerous structures in the vertebral column, including: the meninges overthe spinal cord and nerve roots; the nerve roots themselves; the annulus of the intervertebral discs; vertebral periosteum; joint capsules (especially those of the diarthrodial joints of the articular processes); the epaxial musculature; and the ligamentous structures surrounding the vertebrae. It should also be noted that intracranial disease may cause a ‘referred’ type of neck pain, in circumstances or diseases where there is an elevated intracranial pressure that may cause compression or stretching of the cerebral vasculature and meninges, which are densely innervated with nociceptors.

Localization of painful areas is accomplished by a combination of historical evidence, observation (), palpation and manipulation. After looking for the changes listed in Clinical signs associated with neck or back pain, the clinician must systematically palpate the animal, paying special attention to appendicular muscle bellies and appendicular joints. It is usually best to start caudally and work cranially to localize the pain. The vertebral column is palpated by pressing on the spinous processes or squeezing the articular or transverse processes, depending on the size and temperament of the animal (). Evaluation of the neck should also include flexion, extension and turning of the head and neck, with the palm of the hand placed on the side of the neck to evaluate any resistance to movement.

If possible, the pain should be localized to the cranial, middle or caudal cervical segments. When palpating the thoracolumbar spine to rule out diffuse spinal pain, a hand should be placed on the abdomen to detect increased tension in the muscles as painful areas are approached (). Pressing on the ribs may also be helpful in detecting thoracic vertebral pain. A few animals will be in so much pain that localization is impossible. Palpation of the head, temporal muscles and mandible, and opening the mouth are important in assessing cranial structures (), and manipulation of the tail and the hips are important in assessing lumbar and lumbosacral structures ().

Pathophysiology

Pain receptors (nociceptors) are free nerve endings that are especially numerous in superficial layers of skin, the periosteum, arterial walls, joint capsules, muscles, tendons and meninges. Three types of nociceptor exist in tissues:

  • • Those responding to excessive mechanical stress
  • • Those responding to extreme heat
  • • Those responding to stimulatory chemicals, which include bradykinin, serotonin, histamine, potassium ions, acids, and prostaglandins, leucotrienes and proteolytic enzymes released in various quantities during inflammation.

Nociceptors do not ‘adapt’ to the initial stimulus. They discharge continuously in the face of a persistent stimulus and are capable of responding to repeated stimuli. The sensation of pain is transmitted centrally by small type A-delta fibres at 6-30 m / s (perceived as a sharp or pricking sensation), and by type C fibres at 0.5-2.0 m / s (perceived as a slow burning sensation); both of these types of pain can be felt at the same time. The conscious recognition of these sensations is due to their transmission up the multisynaptic and bilateral spinothalamic and spinoreticular tracts. These tracts pass to the pontobulbar reticular system with ongoing pathways to the thalamus, hypothalamus, and the mesencephalic areas, which reinforce the ’emotional’ aspects of pain in humans.

Tissue damage or inflammation produces pain through stimulation of mechanosensitive, thermosen-sitive and chemosensitive nociceptors. The presence and intensity of pain are dependent on two variables:

  • • The presence of nociceptors (the central nervous system (CNS) does not have nociceptors, so damage to grey and white matter is not painful if other structures are not involved)
  • • The density of nocieptors. The meninges have a high density of nociceptors and are a source of spinal pain.

Occasionally, damage to the CNS can produce pain indirectly as a result of muscle spasm, which stimulates mechanosensitive nociceptors, and so pain relief must be directed toward muscle relaxation.

Unlike back pain, neck pain can commonly be present in the absence of any neurological signs; this is due to a lower spinal cord-to-vertebral canal diameter ratio, which allows for space-occupying lesions to irritate the cord and nerve roots without compressing them (). There is a difference between dog breeds, with small breeds having a higher cervical cord-to-canal ratio than large breeds, meaning that small breeds would be more likely to have concurrent neurological signs and neck pain ().

Differential diagnosis

The diseases that frequently cause spinal pain are listed in Causes of neck and back pain. Many of these are discussed in other chapters, as the diseases often cause neurological signs in addition to pain. There are several notable exceptions, including meningitis, polyarthritis and polymyositis, though the latter two may be associated with weak flexor withdrawals due to physical discomfort and weakness. These two conditions may also be difficult to evaluate for the ‘true’ absence of proprioception deficits due to associated weakness. Intracranial disease should also be considered as a cause of cervical pain, especially in the presence of a compatible history and clinical signs.

Causes of neck and back pain

Disease process Specific diseases
Degenerative Calcinosis circumscripta []
Intervertebral disc disease (Hansen Types I, II & III) []
Wobbler syndrome []
Spondylosis deformans []
Synovial cysts []
Anomalous Atlantoaxial instability []
Chiari-like malformations
Dermoid sinus []
Osteochondromatosis[]
Perineurial (Tarlov) cysts []
Scoliosis / Vertebral anomalies []
Syringohydromyelia []
Neoplastic Extradural []:
Metastasis; vertebral tumours (sarcomas, plasma cell tumours); lymphoma
Intradural / extramedullary:
Meningiomas []; nerve sheath tumours []; metastasis []
Intramedullary []:
Ependymomas; gliomas; metastasis; round cell tumours. Less likely to cause pain
Brain tumours:
Primary or secondary with increased intracranial pressure []
Nutritional Hypervitaminosis A []
Idiopathic Arachnoid cysts []
Inflammatory Infectious meningitis / meningomyelitis []
Steroid-responsive meningitis — arteritis []
Granulomatous meningoencephalomyelitis []
Discospondylitis / osteomyelitis []; physitis []
Empyema[]
Polyarthritis
Polymyositis []
Trauma Fractures / luxations []
Spinal cord contusions []
Traumatic disc herniations []
Vascular Spinal / epidural haemorrhages []

Neurodiagnostic investigation

The approach and subsequent tests required to ‘work-up’ the patient with spinal pain will depend on the history, clinical signs, physical and neurological examinations and, ultimately, the lesion or even system localization. Polymyopathies, polyarthritides and soft tissue abnormalities, in addition to neurological disease, all need to be considered as causes of spinal pain.

Certain diagnostic tests are appropriate in cases with spinal pain:

  • • For all cases, initial clinicopathological tests should include haematology, serum biochemistry and urinalysis
  • • Thoracic radiographs should be obtained as part of the minimum database in dogs or cats with spinal pain; this is especially necessary in older animals and those in which cardiorespiratory disease is also suspected
  • • Survey spinal radiography is essential if a neurological disease is suspected
  • • CSF collection and analysis is essential when survey radiographs are normal, to rule out meningitis ()
  • • Myelography, plain and contrast enhanced CT imaging or MR imaging are often necessary to evaluate patients with spinal pain if the above tests do not establish a diagnosis, especially if surgery is a consideration
  • • Muscle disease will need systemic investigation: electrophysiological testing and muscle biopsy may be needed to determine the underlying aetiology ()
  • • Joint disease should be investigated with the aid of survey joint radiographs and joint taps (arthrocentesis), as well as systemic and infectious disease investigations.

Diseases causing neck and back pain

Degenerative diseases

Anomalous diseases

Neoplastic diseases

Spinal cord tumours are relatively common in cats and dogs and are usually classified according to their position in relation to the spinal cord and meninges as either extradural, intradural-extramedullary or intra-medullary (). Intramedullary neoplasia is rarely painful. Further details on this classification and the diagnosis, treatment and prognosis of spinal tumours can be found in site. Peripheral nerve sheath tumours are discussed in site.

Nutritional diseases

Hypervitaminosis A

Abnormally high levels of vitamin A have been reported in cats on predominantly liver diets. These may cause hypertrophic bone formation on the vertebrae, leading to ankylosing spondylosis, primarily of the cervical vertebrae, but in some cases this may extend to the lumbar region. Clinical signs relate to the rigidity of the spinal column and the associated pain. Treatment involves alteration of the diet, but this does not dramatically reverse the bone formation. Pain relief is recommended.

Inflammatory diseases

Idiopathic diseases

Arachnoid cysts

Also termed subarachnoid cysts, meningeal cysts, intra-arachnoid cysts, leptomeningeal cysts and arachnoid diverticula; these developmental abnormalities have been documented in dogs () and, less commonly, cats. Neck pain is a rare feature of this disease.

Traumatic diseases

Spinal fracture or luxation

Vehicle-related injury is the most common exogenous cause of trauma to the spine in small animals; however, falls, trauma from falling objects, and kicks from farm animals and horses are also possible. Depending on the type of force, the area of impact and the inherent strengths and weaknesses of the vertebral column, exogenous spinal injury often results in vertebral fracture, subluxation or luxation. Cervical and thoracolumbar vertebral injuries are discussed in detail in site. The medical considerations for patients with spinal fractures and luxations are discussed in site.

Vascular diseases

Spinal haemorrhages

Intramedullary, intrameningeal or epidural haemorrhage may be due to coagulopathies, or associated with tumours, vascular malformations, acute intervertebral disc protrusion, trauma, parasitic migration or meningitis. Neurological deficits depend on the location of the haemorrhage and usually indicate an acute focal or multifocal myelopathy accompanied by severe pain. A more detailed description of these diseases is contained in site.