Page 414 - Canine Lameness

386 21 ­Neurorogico giNciN rAectNe Nolgi gim

Treatment of discospondylitis most commonly involves pain management and long‐term
antibiotic therapy (typically 12–24 months). Since relapse is very common following cessation of
antibiotics, follow‐up diagnostic imaging is suggested prior to stopping therapy. There is no
published data to guide the best method in decision‐making for discontinuation of treatment.
Serial radiographs performed until there is no evidence of disease has been recommended by some
authors. Radiographic markers of quiescence used include absence of the lytic focus, smoothing
and then loss of the lytic focus, and replacement by bridging of the involved vertebrae. However, it
can be difficult to differentiate discospondylitis from normal healing processes, as well as degen-
erative end plate changes or new infection superimposed with degenerative spinal disease. Nuclear
imaging, MRI, and CT have all been used for monitoring disease resolution and may be more reli-
able, but with limitations, including general anesthesia requirements, expense, and availability.
The author typically performs radiographs at three‐ to six‐week intervals until there is evidence of
static changes over at least three serial studies.

21.3.2 Neuropathies (Nerves and Lumbosacral Plexus)

21.3.2.1 Sciatic Nerve Injury
The anatomic location of the sciatic nerve makes it particularly subject to injury from lumbosa-
cral fractures and subluxations, lumbosacral stenosis, and pelvic or femoral fractures. The
proximal portion of the nerve can be damaged by fractures of the ilium, acetabulum, and proxi-
mal femur. Iatrogenic injury can occur during surgical procedures (e.g. retrograde intramedul-
lary pin placement in the femur, suture entrapment during hernia repair). More distal portions
of the sciatic nerve (i.e. the fibular or tibial nerves along the caudal aspect of the femur) can
incur injury from intramuscular injections given in the caudal thigh or distal femoral fractures.
Less commonly, severe hip dysplasia can be associated with sciatic nerve damage (Sorjonen
et al. 1990).
Clinical signs will depend on the location of the injury. Traumatic injuries to the lumbosacral
region rarely result in a mononeuropathy since axons forming other nerves, such as pelvic, puden-
dal, and caudal nerves, are also injured. If there is damage to the nerve fibers in the spinal canal,
at the level of the cord, then the injury and deficits will usually be bilateral. Lesions at, or proximal
to, the lumbosacral trunk will result in complete loss of sciatic nerve function as well as signs of
fibular and/or tibial nerve dysfunction where the patient will be unable to extend the hip, flex the
stifle, or flex and extend the hock and digits. The animal will be able to extend the stifle and thus
bear weight on the limb since femoral nerve function is intact but may stand or walk on the dor-
sum of the foot “knuckled over” or otherwise assume a plantigrade stance. Sensation will be com-
promised laterally (fibular nerve), caudally (tibial nerve), and dorsally (fibular nerve) but preserved
medially from the intact saphenous branch of the femoral nerve. The withdrawal reflex is weak or
absent with lack of flexion in the stifle, hock, and digits, especially with stimulation of the lateral
digits. Stimulation of the medial digits might still elicit a conscious response and flexion of the hip
due to femoral innervation. Severe pain may occur with nerve entrapment and self‐mutilation may
be an accompanying sign.
Treatment will vary with the cause and severity of the neuropathy but at minimum should
include intense physiotherapy and adequate skin care. Nerve regeneration following iatrogenic
injury is determined by the degree of injury (Chapter 16), with crushing injuries having a worse
prognosis. When due to impingement from an intramedullary pin, removal of the pin usually leads
to clinical improvement. Prognosis depends on the severity of injury making careful assessment of
both sensory and motor function crucial to determine distribution and nerve involvement. Most