Page 69 - Canine Lameness

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4

The Neurologic Examination

Lisa Bartner

Department of Clinical Sciences, College of Veterinary Medicine and Biomedical Sciences, Colorado State University, Fort Collins,
CO, USA

4.1 Introduction

The most common cause of a gait abnormality is orthopedic disease, yet gait irregularities can also
be associated with neurologic causes. Gait abnormalities resulting from neurologic dysfunction
can be broadly categorized into three components that may be observed in combination or as an
isolated component depending on the nervous structures involved: neurogenic lameness, paresis,
and ataxia (Box 4.1).
Neurogenic lameness is attributable to discomfort caused by pathology affecting the nerve roots
and surrounding meninges (e.g. from a lateralized disc herniation). Thus, this is frequently referred
to as “nerve root signature lameness” (Dewey et al. 2016). These patients commonly have a weight‐
bearing lameness, although in more severe cases, the limb may be held up. This lameness can eas-
ily be confused with orthopedic causes of lameness (Video 4.1).

Video 4.1:

Brachial plexus tumor causing neurogenic lameness and partial Horner syndrome.

Paresis describes a partial loss of voluntary movement that is due to disruption of the signal
transmission from either the level of the upper motor neuron (UMN) or lower motor neuron
(LMN). A UMN paresis results from loss of normal signal transmission from higher motor centers
to the LMN and causes the inability to initiate gait voluntarily (i.e. decrease in voluntary move-
ment). An LMN paresis results from loss of normal signal transmission from the LMN to the mus-
cle and causes the inability to support weight (i.e. decrease in muscle “power”). Lesions causing
UMN paresis generally affect multiple limbs, whereas those causing LMN paresis can involve only
a single limb (monoparesis), which is commonly confused with lameness (Figure 4.1). Some texts
use the term weakness synonymously with paresis; however, since systemic conditions can also

Canine Lameness, First Edition. Edited by Felix Michael Duerr.
© 2020 John Wiley & Sons, Inc. Published 2020 by John Wiley & Sons, Inc.
Companion website: www.wiley.com/go/duerr/lameness