Page 415 - Canine Lameness

21.3 ­Neurorogico giNciNi AANicgio ctNe Nolgi gim 387

injuries are neuropraxic and will often resolve in one to two months. Cutaneous sensation is typi-
cally preserved in these cases and supports a better prognosis. However, markedly decreased or
absence of pain perception suggests severe injury. Similar to brachial plexus injuries, limb amputa-
tion may need to be considered if self‐mutilation or injury from dragging the limb occurs.

21.3.2.2 Fibular (Peroneal) Nerve Injury
The fibular nerve is most susceptible to injury as it crosses the lateral aspect of the stifle joint.
Injury to the fibular nerve can occur as a result from a damaging insult to the lateral aspect of the
stifle; this can occur with trauma, surgery (such as lateral suture placement for cranial cruciate
ligament rupture), or inadvertent intraneural injections.
Clinically affected animals will have weak hock flexion, the hock may be overextended, and the
foot may also “knuckle over.” There will be decreased cutaneous sensation on the dorsal surface of
the paw and cranially overlying the hock and tibia; however, the dorsal surface of the foot does not
tend to get as ulcerated as with more proximal sciatic nerve lesions. Most dogs learn to accommo-
date by greater flexion at the hip and extension at the stifle giving the impression of a “high‐
stepping gait” and the classic “sciatic gait” (Video 21.1). This must not be confused with hypermetria
associated with cerebellar ataxia or the overreaching stride sometimes seen in GP ataxia (Chapter 4).
Hock flexion will be severely decreased during testing of the withdrawal reflex and the conscious
response will be diminished with stimulation to the dorsal aspect of the foot or digits; if the plantar
surface of the digits is pinched (tibial nerve), then the animal will have a conscious response (affer-
ent arm of the reflex) but the flexor reflex will be reduced (efferent arm of the reflex). Proprioceptive
deficits are usually present.

Video 21.1:

Fibular nerve injury gait (sciatic gait).

Treatment and prognosis are variable depending on cause and severity as for other injuries.
Removal of inappropriately placed sutures usually results in improvement and therefore should be
performed immediately if severe pain is noted after stifle surgery (lateral suture).

21.3.2.3 Tibial Nerve Injury
Tibial nerve injury is less common than fibular nerve injury but can occur secondary to similar
causes. In most animals, tibial nerve injuries occur together with fibular nerve lesions. Animals
presenting with pure tibial nerve injury will display loss of hock extension, loss of sensation on the
plantar surface of the paw, and proprioceptive deficits. The hock is dropped when the dog walks or
when weight is supported on the limb. Trophic ulceration on the plantar surface can occur. The
flexor withdrawal reflex is decreased when the plantar surface of the paw is stimulated but may be
present when the dorsal surface is pinched. Dogs with tibial nerve dysfunction alone can usually
accommodate well, and therefore treatment is conservative in most cases. Pantarsal arthrodesis
and/or the use of orthotic devices may be helpful in those animals who do not improve. If sensory
function remains intact, then the animal has a fairly good prognosis and conservative treatment is
recommended. The presence of sensory deficits (decreased or absent nociception) carries a more
guarded to poor prognosis.