Page 74 - Canine Lameness

46 4 The Neurologic Examination

Table 4.1 Comparison between neuroanatomy and clinical signs from lower motor neuron (LMN)
and upper motor neuron (UMN) lesions.

LMN UMN
Neuroanatomy
Neuroanatomic Peripheral nervous system: spinal cord Central nervous system (cerebral cortex,
origins gray matter (cell bodies) and brainstem basal nuclei, brainstem, and spinal cord
(cranial nerves) white matter)
Spinal cord C6–T2 C1–C5
segments L4–S3 T3–L3
S4–Cd segments
Neuroanatomic Neuron (cell bodies and nerve fibers form Neuron (cell bodies and nerve fibers form
components nerve root, spinal nerve, and named nerve) UMN tracts)
Neuromuscular junction
Muscle
Clinical signs
Quality of paresis Flaccid (i.e. loss of muscle “power”) Spastic (i.e. loss of voluntary movement)
or paralysis
Ataxia type None General proprioceptive (GP)
Posture Crouched stance Normal to slightly crouched
Limbs more centered under the trunk to May vary between base‐wide and base‐
help support weight‐bearing narrow stances
Collapse of limbs when weight‐bearing Limbs may be in an awkward state (e.g.
Ventral neck flexion (generalized crossed over, more toward, or away from
conditions) midline)
Inability to support weight (paresis) Standing on dorsum of the paw
Off‐weighting a limb(s) (nerve pain) (spontaneous knuckling)
Gait Gait characterization: Gait characterization:
“Regularly irregular” gait “Irregularly irregular” gait
● ●
a
LMN paresis: UMN paresis and GP ataxia :
Shortened stride Lengthened stride
● ●
Nails or foot pads may drag Nails may drag
● ●
Shuffling gait Stiff
● ●
± “Bunny hopping” in pelvic limbs Delayed initiation and protraction phase
● ●
May prefer to walk rather than stand May vary between base‐wide and base‐
● ●
Normal initiation phase with narrow gait
●
shortened protraction phase
± Muscle fasciculations
●
Inability to support weight (paresis)
●
Neurogenic lameness:
Shortened stride
●
Nails or foot pads may drag
●
Unwillingness to support weight
●
(nerve pain)
Segmental spinal Usually decreased or absent at respective Normal or may be increased caudal to
reflexes anatomic segment (unchanged for others) respective segment
Muscle mass Denervation atrophy within 7–10 days Disuse atrophy after 30 days
(i.e. neurogenic atrophy) Usually mild to moderate; severe with
Usually severe chronicity