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Get off my back you pain in the neck: Managing pain in neurologic patients (Proceedings)

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Aug 01, 2010

The inability of our veterinary patients to speak to us can make determining the presence of pain a challenging process. Vocalization is often a clear sign that an animal is painful. However, even this can be misleading at times, as animals with brain disorders may vocalize without being painful. Tremors and muscles spasms may indicate pain. However, dogs with neuromuscular, cerebellar or diffuse CNS disorders may tremor as well. Thus identifying the presence of pain in the neurologic patient can be difficult. Ruling out other causes for vocalization and tremors with a thorough neurological examination is essential. Changes in body posture such as decreased head carriage, kyphosis and lordosis may indicate cervical or back pain. Changes such as tachycardia, tachypnea, decreased grooming, decreased appetite, lethargy and a change in elimination habits can also be general indicators of pain. Several pain scoring systems are available each with benefits and short comings. Pain scoring is helpful in raising hospital staff awareness and recognition of pain. Serial pain scoring enables us to evaluate the efficacy of pain therapy and optimize pain management. The variable pain responses patients manifest make definitive criteria challenging. One patient may vocalize when painful while another is less vocal and reclusive. Inter user interpretation and variation may affect accuracy of pain scoring.

Cervical pain often manifests with decreased head and neck carriage. Muscle spasms at times may be present. Palpating the cervical spine may indicate cervical pain. However, some dogs may resent palpation in general and may exhibit a behavioral response/reluctance to be handled in the head and neck region. Vocalization or reluctance to allow cervical flexion either laterally, ventrally or dorsally is often the best indicator or cervical pain. Voluntarily turning the whole body instead of the neck may also indicate cervical pain.

Kyphosis is a common finding in patients with thoraco-lumbar pain. Other signs may include reluctance to walk, a tense abdomen or apparent pain on paraspinal palpation. Further diagnostic evaluation of the abdomen via serum chemistry, particularly pancreatic enzyme evaluation and abdominal ultrasound can be helpful in distinguishing abdominal diseases vs thoracolumbar pain.

Cauda equina syndrome is a common cause of pain and discomfort in aging large breed dogs. Dogs often present with a history of decreased tail carriage, difficulty rising, jumping and decreased frequency or ability in walking up and down stairs. A stiff pelvic limb gait or lameness may be apparent on examination. Conscious proprioception deficits may be present in the pelvic limbs. In the most severe cases fecal and urinary incontinence, the loss of a perineal reflex and diminished anal tone may be present. On examination palpation of the lumbosacral region and more commonly dorsoflexion of the tail yields an apparent pain response. Stiff gaits may also be caused by degenerative joint disease, polyarthritis and neuromuscular diseases such as polymyopathies and polyneuropathies. Creatine kinase evaluation is extremely important and may be the only other clue that a polymyopathy is present as signs can overlap.

Several diagnostic tools may be utilized to assess the localized area of pain. Plain radiographs may indicate: narrowed disc spaces suggestive of IVDD, endplate lysis consistent with discospondylitis and vertebral lesions (lysis or production) consistent with either neoplasia or infection. MR imaging has become increasingly favored. Advantages of MR imaging include minimal invasiveness, evaluation of contrast enhancement, multiplanar imaging and the ability to detect lesions both within and outside the spinal cord. MR imaging can detect lesions such as discospondylitis and neoplasia before radiographic abnormalities may be present. Myelography in combination with CT scan is also very good at detecting extra-axial spinal cord lesions such as IVDD. In very small/toy breed dogs myelography combined with CT scan may be superior to MR imaging for the diagnosis of IVDD as thinner slice thickness is possible with CT scan compared to MR imaging. The increasing strength of magnets, MRI coil quality and software upgrades may negate this size consideration. When a structural lesion is not apparent or considered potentially incidental CSF evaluation is essential in ruling out inflammatory, infectious causes as well as lymphoma. Electromyography (EMG) is a helpful screening test for neuromuscular diseases. EMG evaluation also may distinguish neurological causes of lameness from orthopedic causes. Animals with purely orthopedic causes have a normal EMG evaluation, while animals with a C6-T2 myeloradiculoneuropathy, neuropathy or myopathy may have an abnormal EMG evaluation. EMG evaluation can be very helpful in dogs with lumbosacral disc disease. The presence of EMG changes with a sciatic distribution is highly suggestive that a lumbosacral disc herniation is a clinical problem. Joint fluid evaluation is clearly indicated in animals with joint pain or joint effusion. It should also be considered when other diagnostic tests are unremarkable and the cause of pain is still in question and when fever of unknown origin is present.