Equine Pathology Workbook

CHAPTER 21: LOCATION OF NERVOUS SYSTEM LESIONS

Introduction

In general, locating a nervous system lesion requires that careful observations of the signs & symptoms are made & that useful conclusions are drawn based on these clues. In diagnosis of neurologic lesions, a diagnosis method is used, where other possible causes are ruled out & pinpointing the actual location of a lesion is done by testing the function of the target organs, such as muscles and glands, to determine their function. In human & small animal practice it is more practical to use technologies such as electromyography ( ) to evaluate nerve function directly & in human medicine the patient can communicate his symptoms, but the equine practitioner must use the skills of detection to discover the areas of the body that are malfunctioning & combine this information with their knowledge of equine physiology & anatomy to make an informed guess as to where the nervous lesion is located.

Diagnosis and Location of Nervous Tissue Lesions

The first step in the diagnosis of nervous system lesions is to rule out the possibility that musculoskeletal dysfunction is responsible for the clinical signs and symptoms. This is done through the taking of an extensive case history to note any occasions of illness or trauma, gait analysis, testing reflexes, flexion tests, nerve blocks, palpation and disease specific tests. At this stage EMG should be used to detect the functionality and contractility of skeletal muscle if such technologies are available. If skeletal muscle is determined to be functioning normally it can be assumed the dysfunction is occurring in the nervous tissue or in the neuromuscular junction. Now it must be determined if the lesion is located in the central nervous system (CNS), the peripheral nervous system (PNS), or at the neuromuscular junction. Generally, dysfunction of the neuromuscular junction can be ruled out by the case history and by blood analysis revealing no signs of infection or toxins. To differentiate between CNS lesions and PNS lesions one must examine the clinical presentation of the dysfunction. Dysfunction of each part of the brain can be related to distinct clinical presentations, which can be used to determine the probable location of brain lesions.

are located in the brain and spinal cord, so lesions

presenting with UMN symptoms must be located in the central nervous system.

are outside the spinal cord or brain, so lesions

presenting with LMN symptoms must be located in the peripheral nervous system.

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