Large Animal Neurology. Joe Mayhew

input from many other regions of the nervous system and are interconnected.

The final concept of clinical neuroanatomy important in interpreting large animal neurologic examinations is that of the specialized areas of relatively well‐developed functional centers that exist in the forebrain, but having brainstem connections, as introduced in Figure 1.8. The frontal and prefrontal cerebral lobes (A) are involved with mentation and behavior, and with fine motor activity at least in primates. As in humans, the parietal lobes (B) integrate conscious proprioceptive and nociceptive input in the large animal species. Certainly, vision appears to require an intact occipital cortex (C). Control of normal learned behavior and perception of sound may be functions of the temporal lobes (D). The hypothalamus and its pituitary gland (E) help control autonomic and endocrine functions of the body, whereas the deeper, old part of the brain known as the limbic system (F) may be involved with innate behavioral patterns. Finally, the basal nuclei (G) do appear to have some motor control at least for cranial nerve function in horses. Irrespective of the regions of the cerebral cortex, large lesions can occur which in their stable state do not result in permanent disability; so‐called silent areas (e.g. Figure 2.5).

Figure 1.8 Functional regions of the forebrain include the frontal cortex A involved with mentation, behavior, and motor activity; the parietal cortex B involved with pain perception particularly from the head and conscious proprioception; the occipital cortex C involved with vision; the temporal cortex D involved with behavior and hearing; the hypothalamus and pituitary E involved with autonomic and endocrine functions; and the deep‐seated limbic system F involved with innate behavior.

      With this understanding of functional neuroanatomy and a little practice, a neurologic examination can be readily performed and interpreted. An outline of such a neurologic examination is given in the next chapter.

References

      1 1 WAVA. Nomina anatomica veterinaria, Nomina histologica veterinaria and Nomina embryologica veterinaria. World Association of Veterinary Anatomists. 2017. Available from: http://www.wava‐amav.org/wava‐documents.html .

      2 2 Jenkins TW. Functional Mammalian Neuroanatomy. Lea & Febiger, Philadelphia, PA. 1972; 410.

      3 3 King AS. Physiological and Clinical Anatomy of the Domestic Mammals, Volume 1: Central Nervous System. Oxford Science Publications, Oxford. 1987; 325.

      4 4 Waxman SJ. Clinical Neuroanatomy. 25th ed. McGraw‐Hill Medical, 2002; 400.

      5 5 Thomson C and Hahn C. Veterinary Neuroanatomy: A Clinical Approach. 1st ed. Saunders Elsevier. 2012; 208.

      6 6 Peele TL. The Neuroanatomic Basis for Clinical Neurology. 3rd ed. McGraw‐Hill Book Company, New York. 1977; 144.

      7 7 de Lahunta A, Glass E, and Kent M. Veterinary Neuroanatomy and Clinical Neurology. 4th ed. Saunders, Elsevier, St. Louis, MO. 2015.

      8 8 Innes JRM and Saunders LZ. Comparative Neuropathology. Academic Press, London. 1962.

      9 9 Vandevelde M, Higgins RJ, and Overmann A. Veterinary Neuropathology: Essentials of Theory and Practice. Wiley‐Blackwell, Hoboken, NJ. 2012; 216.

      10 10 Summers BA, Cummings JF, and de Lahunta A. Veterinary Neuropathology. Mosby, St. Louis, M.O. 1995; 527.

      11 11 Rossignol S, Dubuc R, and Gossard JP. Dynamic sensorimotor interactions in locomotion. Physiol Rev 2006; 86(1): 89–154.

      12 12 Clayton HM. Horse Species Symposium: biomechanics of the exercising horse. J Anim Sci 2016; 94(10): 4076–4086.

      13 13 Dietz V. Spinal cord pattern generators for locomotion. Clin Neurophysiol 2003; 114(8): 1379–1389.

      14 14 Duysens J and Van de Crommert HW. Neural control of locomotion: the central pattern generator from cats to humans. Gait Posture 1998; 7(2): 131–141.

      15 15 Yuste R, MacLean JN, Smith J and Lansner A. The cortex as a central pattern generator. Nat Rev Neurosci 2005; 6(6): 477–483.

2 Neurologic evaluation

      Disease

        Overview

        Signalment

        History

        Procedure for the neurologic examination

        Interpretation of findings Brain and cranial nerve disease Spinal cord disease Peripheral nerve disease

        Where and what is the lesion?

        Initial plan

        References

Overview

Traditionally, a detailed neurologic examination follows the collection of information on a patient’s signalment and history, an evaluation of the environment, and a complete physical examination.^1–13 However, during the evaluation of a large animal suspected of having a neurologic disorder, most busy practitioners include several components of a neurologic examination during variations of the general physical examination as listed in Table 2.1.

      To distinguish between vertebral bodies and spinal cord segments, vertebral bodies and regions will be defined by site and standard numerals, whereas spinal cord segments will be defined by site with subscripted numerals. Thus, the last three cervical vertebrae are C_5–7 and the last three cervical spinal cord segments are C_6–8.

      Sometimes enough evidence is available from this examination to proceed with a tentative diagnosis and therapy. However, if this initial general evaluation is not enough to make an accurate anatomic diagnosis, especially if a thorough case workup is warranted or requested, then a complete neurologic examination should be undertaken that will often uncover further neurologic findings helpful to case workup. In fact, even with second opinion cases, we usually go quite rapidly through a neurologic examination in say 5 min, then return to scrutinize major components of the examination dependent on clues from the history, physical examination, contributory test results, and initial examination. Even then, it can be useful to develop a mental list of further procedures to undertake to assist with this diagnostic process. These may include testing eye responses in dim and bright light, testing nasal and temporal field vision, and spinal reflex testing in