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Topic:Nerves
The study of nerves in horses encompasses the structure, function, and disorders of the equine nervous system. This system is responsible for transmitting signals between different parts of the body and coordinating actions and sensory information. Key components include the central nervous system, consisting of the brain and spinal cord, and the peripheral nervous system, which includes nerves extending throughout the body. Research in this area investigates the role of nerves in equine behavior, movement, and response to stimuli, as well as conditions such as neuropathies and nerve injuries. This topic includes a collection of peer-reviewed research studies and scholarly articles that explore the anatomy, physiology, and clinical implications of the nervous system in horses.
Neurologic Diseases in Horses. This article focuses on the gross examination of the brain and spinal cord and outlines the main lesions and neuroanatomic location related to neurologic diseases in horses.
Pathophysiology of free-bullet slaughter of horses and ponies. Forty-six equines were observed during routine commercial slaughter in an abattoir. The animals were shot once with a .22 calibre long rifle with hollow point rounds. Indicators of sensibility/insensibility were evaluated immediately after the shot (prior to exsanguination) and the resulting pathophysiology of free-bullet injury was assessed. All animals were rendered immediately insensible, with only one pony showing signs of a shallow depth of concussion, with an intermittently positive palpebral reflex but no other signs of brainstem function. All animals (100%) had some degree of damage to...
IMAGING DIAGNOSIS – UNILATERAL TRIGEMINAL NEURITIS MIMICKING PERIPHERAL NERVE SHEATH TUMOR IN A HORSE. A 16-year old Warmblood gelding presented with a nonhealing corneal ulcer and absent corneal sensation in the left eye. A lesion affecting the maxillary and ophthalmic branches of the left trigeminal nerve was suspected. Magnetic resonance (MR) imaging identified marked thickening of the ophthalmic and maxillary branches of the left trigeminal nerve. The nerve was iso- to hypointense on T1-weighted and T2-weighted images with heterogeneous enhancement. A peripheral nerve sheath tumor was suspected, however granulomatous neuritis was histopathologically confirmed. These inflammatory changes can...
Laryngeal advancement surgery improves swallowing function in a reversible equine dysphagia model. Pharyngeal dysphagia is a debilitating, sometimes fatal condition in horses, with multiple aetiologies. The pathophysiology is complex and not fully understood. Treatment is largely supportive. Laryngeal advancement surgery may diminish symptoms of dysphagia and improve swallowing in affected horses. Objective: 1) to induce reversible moderate and marked pharyngeal dysphagia by regional anaesthesia of branches of the glossopharyngeal (IX), vagus (X) and hypoglossal (XII) nerves; 2) to characterise the dysphagia produced by each model; and 3) to determine whether laryngeal advancement surgery i...
Ultrasonographic detection of early atrophy of the intrinsic laryngeal muscles of horses. To describe the ultrasonographic changes in the cricoarytenoideus dorsalis (CAD) and cricoarytenoideus lateralis (CAL) muscles of horses before and at various times during the 32 weeks after unilateral neurectomy of the right recurrent laryngeal nerve. Methods: 28 healthy Standardbreds. Methods: For each horse, the appearance of the CAD and CAL muscles on the right (neurectomized) and left (control) sides was serially monitored ultrasonographically by percutaneous (CAD and CAL) and transesophageal (CAD) approaches. The ultrasonographic images were assessed to determine the mean pixel intensity...
ANATOMICAL STUDY OF CRANIAL NERVE EMERGENCE AND SKULL FORAMINA IN THE HORSE USING MAGNETIC RESONANCE IMAGING AND COMPUTED TOMOGRAPHY. For accurate interpretation of magnetic resonance (MR) images of the equine brain, knowledge of the normal cross-sectional anatomy of the brain and associated structures (such as the cranial nerves) is essential. The purpose of this prospective cadaver study was to describe and compare MRI and computed tomography (CT) anatomy of cranial nerves' origins and associated skull foramina in a sample of five horses. All horses were presented for euthanasia for reasons unrelated to the head. Heads were collected posteuthanasia and T2-weighted MR images were obtained in the transverse, sagittal, and do...
Cerebral and brainstem electrophysiologic activity during euthanasia with pentobarbital sodium in horses. An overdose of pentobarbital sodium administered i.v. is the most commonly used method of euthanasia in veterinary medicine. Determining death after the infusion relies on the observation of physical variables. However, it is unknown when cortical electrical activity and brainstem function are lost in a sequence of events before death. Objective: To examine changes in the electrical activity of the cerebral cortex and brainstem during an overdose of pentobarbital sodium solution for euthanasia. Our testing hypothesis is that isoelectric pattern of the brain in support of brain death occurs bef...
Validation of the accuracy of needle placement as used in diagnostic local analgesia of the maxillary nerve for investigation of trigeminally mediated headshaking in horses. Diagnostic local anaesthesia of the maxillary nerve is a valuable aid in the diagnosis of trigeminally mediated headshaking in horses. Our objective is to validate the accuracy of needle placement in this procedure and to identify any correlation between accuracy of the technique and operator experience. Using a small volume of contrast medium, the procedure was performed bilaterally on 30 horse cadaver heads by three groups with different levels of experience with the technique. The location of deposition was then identified using computed tomography (CT). Contrast medium was deposited around...
Vascular hamartoma in the central nervous system of a foal. Vascular hamartomas are non-neoplastic developmental anomalies of vessels. Cases of cerebral vascular hamartomas have been previously reported in dogs and cats. A 4-week-old Freiberger foal had shown persistent problems with breathing and swallowing since birth, and bilateral laryngeal paralysis was diagnosed. The foal subsequently developed left sided facial nerve paralysis and a secondary corneal ulcer in the left eye. Necropsy revealed a pinkish mass in the obex region of the brain. The mass was further investigated by histology and immunohistochemistry. Histologically, the mass consisted o...
Encephalitozoon cuniculi-Associated Equine Encephalitis: A Case Report. A case of encephalitis of unknown origin in the horse was investigated. Postmortem examination findings revealed a nonsuppurative granulomatous meningoencephalitis in the right hemisphere of the cerebral cortex. Testing for West Nile virus, equine herpes virus, equine infectious anemia, , , and were negative. The horse had a titer for , and sections from the affected area of the brain tested positive for the organism using both polymerase chain reaction (PCR) and immunohistochemistry. Amplicons generated using PCR were sequenced, and genotype II was identified. This is the first case of gen...
Tracheal resection and anastomosis after traumatic tracheal stenosis in a horse. To report a resection and anastomosis technique to treat trauma-induced tracheal stenosis. Methods: Case report. Methods: A 9-year-old Warmblood gelding. Methods: Endoscopy, radiography, and ultrasonography were used to diagnose a single ring tracheal stenosis; the stenotic region was resected and adjacent tracheal rings anastomosed with an end-to-end technique. Results: The anastomosis healed completely despite formation of a unilateral partial mucosal stenosis "web," which was subsequently removed by transendoscopic laser surgery. During tracheal anastomosis, the left recurrent laryngeal ner...
The Inferior Alveolar Nerve of the Horse: Course and Anatomical Relationship with Mandibular Cheek Teeth. The precise location of neurovascular structures within the relatively long mandibular canal of the horse is of paramount importance in surgical procedures of the area. The inferior alveolar nerve (IAN) enters the mandibular canal on the medial (lingual) surface of the mandible and innervates all the mandibular teeth. During its course, the nerve moves laterally, crossing the roots of the inferior cheek teeth. However, the exact anatomical relationships occurring between the IAN and the roots of the equine mandibular cheek teeth have not been described in detail. In this study, the mandibles o...
Is anaesthesia of the deep branch of the lateral plantar nerve specific for the diagnosis of proximal metatarsal pain in the horse? To investigate the specificity of anaesthesia of the deep branch of the lateral plantar nerve (DB-LPN). Methods: Twenty horses had DB-LPN anaesthesia performed by a single injection technique as part of a lameness investigation. The mechanical nociceptive threshold (NT) was measured using a handheld force meter at six points on the lateral aspect of the limb: before diagnostic anaesthesia (T0), and at 15 (T15) and 30 (T30) minutes post anaesthesia. Paired t-tests were performed and significance was set at p <0.05. In addition, ten cadaveric limbs were injected with 2.5 ml new methylene blue...
Analgesic effects of intraneural injection of ethyl alcohol or formaldehyde in the palmar digital nerves of horses. To determine analgesic effects of intraneural injection of ethyl alcohol or formaldehyde in the palmar digital nerves of horses. Methods: 6 horses. Methods: Ethyl alcohol was injected in the medial palmar digital nerve of 1 forelimb, and formaldehyde was injected in the contralateral nerve. The lateral palmar digital nerve in 1 forelimb was surgically exposed, but not injected, and the contralateral lateral palmar digital nerve was not treated. For each heel, severity of lameness in response to experimentally induced heel pain (lameness score and peak vertical force), thermal reaction time, an...
Brainstem auditory evoked responses in an equine patient population. Part II: foals. Reports of the use of brainstem auditory evoked response (BAER) as a diagnostic modality in foals have been limited. Objective: To describe BAER findings and associated causes of hearing loss in foals. Methods: Study group 18 foals (15 neonatal, 3 nonneonatal), control group (5 neonatal foals). Methods: Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Clinical data were extracted from the medical records. Foals were grouped under disease categori...
Brainstem auditory evoked responses in an equine patient population: part I–adult horses. Brainstem auditory evoked response has been an underused diagnostic modality in horses as evidenced by few reports on the subject. Objective: To describe BAER findings, common clinical signs, and causes of hearing loss in adult horses. Methods: Study group, 76 horses; control group, 8 horses. Methods: Retrospective. BAER records from the Clinical Neurophysiology Laboratory were reviewed from the years of 1982 to 2013. Peak latencies, amplitudes, and interpeak intervals were measured when visible. Horses were grouped under disease categories. Descriptive statistics and a posthoc Bonferroni test...
Spectral-domain optical coherence tomography evaluation of the cornea, retina, and optic nerve in normal horses. To determine the feasibility of using a handheld spectral-domain optical coherence tomography (SD-OCT) instrument to characterize normal corneal, retinal, and optic nerve head anatomy in vivo in standing horses. Methods: Clinically normal horses under sedation, palpebral nerve blockage, and pharmacologically induced mydriasis were imaged with a SD-OCT instrument (Envisu SD-OCT, Bioptigen, Inc., Morrisville, NC). Radial volumes from the cornea (axial, superior, inferior, nasal, and temporal), and rectangular volumes from the retina (dorsal, ventral, nasal, and temporal) and optic nerve head wer...
Simulation of the Electrical Field in Equine Larynx to Optimize Functional Electrical Stimulation in Denervated Musculus Cricoarythenoideus Dorsalis. Distribution of the electrical field is very important to activate muscle and nerve cells properly. One therapeutic method to treat Recurrent Laryngeal Neuropathy (RLN) in horses can be performed by Functional Electrical Stimulation (FES). Current method to optimize the stimulation effect is to use implanted quadripolar electrodes to the musculus cricoarythenoideus dorsalis (CAD) and testing electrode configuration until best possible optimum is reached. For better understanding and finding of maximum possible activation of CAD a simulation model of the actual entire setting is currently in de...
Comparative quantitative study of astrocytes and capillary distribution in optic nerve laminar regions. Retinal ganglion cell (RGC) axonal structure and function in the optic nerve head (ONH) is predominantly supported by astrocytes and capillaries. There is good experimental evidence to demonstrate that RGC axons are perturbed in a non-uniform manner following ONH injury and it is likely that the pattern of RGC axonal modification bears some correlation with the quantitative properties of astrocytes and capillaries within laminar compartments. Although there have been some excellent topographic studies concerning glial and microvascular networks in the ONH our knowledge regarding the quantitati...
Allometry of left ventricular myocardial innervation. Body mass (BM) of terrestrial mammalian species ranges from a few grams in the case of the Etruscan shrew to a few tonnes for an elephant. The mass-specific metabolic rate, as well as heart rate, decrease with increasing BM, whereas heart mass is proportional to BM. In the present study, we investigated the scaling behaviour of several compartments of the left ventricular myocardium, notably its innervation, capillaries and cardiomyocytes. Myocardial samples were taken from 10 mammalian species with BM between approximately 2 g and 900 kg. Samples were analysed by design-based stereology and e...
The brain of the horse: weight and cephalization quotients. The horse is a common domestic animal whose anatomy has been studied since the XVI century. However, a modern neuroanatomy of this species does not exist and most of the data utilized in textbooks and reviews derive from single specimens or relatively old literature. Here, we report information on the brain of Equus caballus obtained by sampling 131 horses, including brain weight (as a whole and subdivided into its constituents), encephalization quotient (EQ), and cerebellar quotient (CQ), and comparisons with what is known about other relevant species. The mean weight of the fresh brains in o...
Localization of the cutaneus trunci muscle reflex in horses. To determine the magnitude and location of skin movement attributable to the cutaneus trunci muscle reflex in response to localized stimulation of the skin of the dorsolateral aspect of the thoracic wall in horses. Methods: 8 horses. Methods: A grid of 56 reflective markers was applied to the lateral aspect of the body wall of each horse; markers were placed at 10-cm intervals in 7 rows and 8 columns. A motion analysis system with 10 infrared cameras was used to track movements of the markers in response to tactile stimulation of the dorsolateral aspect of the thoracic wall at the levels of T6...
Sensory nerve conduction and somatosensory evoked potentials of the trigeminal nerve in horses with idiopathic headshaking. Idiopathic headshaking (HSK) in horses is a distressing disorder in which the etiology and pathophysiology are unknown. Objective: Differences in sensory function of the trigeminal nerve exist between healthy and affected horses. Methods: Six healthy mature geldings and 6 mature geldings with idiopathic HSK. Methods: Prospective study. Sensory nerve action and somatosensory evoked potentials studies were performed. The stimulus site comprised the gingival mucosa dorsal to the maxillary canine. A pair of recording electrodes was placed along the sensory pathway of the trigeminal complex at the ...
Ultrasound-guided injection of the maxillary nerve in the horse. Infiltration of the equine maxillary nerve with local anaesthetic can be useful for both diagnostic and surgical procedures. The deep location and proximity of the nerve to surrounding vascular and orbital structures make an accurate, complication-free injection a challenge using traditional techniques reliant upon surface anatomical landmarks. Objective: To develop an ultrasound-guided injection technique of the maxillary nerve in equine cadavers and to evaluate its efficacy and potential for complications in vivo. Methods: Descriptive cadaver anatomical and clinical study. Methods: The relev...
Expression of purinergic P2X receptor subtypes 1, 2, 3 and 7 in equine laminitis. Tissue sensitisation and chronic pain have been described in chronic-active laminitis in the horse, making treatment of such cases difficult. Purinergic P2X receptors are linked to chronic pain and inflammation. The aim of this study was to examine the expression of purinergic P2X receptor subtypes 1, 2, 3 and 7 in the hoof, palmar digital vessels and nerve, dorsal root ganglia and spinal cord in horses with chronic-active laminitis (n=5) compared to non-laminitic horses (n=5). Immunohistochemical analysis was performed on tissue sections using antibodies against P2X receptor subtypes 1-3 and ...
Expression of β2 adrenoceptors within enteric neurons of the horse ileum. The activity of the gastrointestinal tract is regulated through the activation of adrenergic receptors (ARs). Since data concerning the distribution of ARs in the horse intestine is virtually absent, we investigated the distribution of β2-AR in the horse ileum using double-immunofluorescence. The β2-AR-immunoreactivity (IR) was observed in most (95%) neurons located in submucosal plexus (SMP) and in few (8%) neurons of the myenteric plexus (MP). Tyrosine hydroxylase (TH)-IR fibers were observed close to neurons expressing β2-AR-IR. Since β2-AR is virtually expressed in most neurons located...
Effects of hypoglossal nerve block and electrical stimulation of the thyrohyoideus muscles on position of the larynx and hyoid apparatus in healthy horses. To determine the effects of hypoglossal nerve block and electrical stimulation of the thyrohyoideus muscles on position of the larynx and hyoid apparatus in resting horses. Methods: 16 healthy horses that underwent hypoglossal nerve block and 5 healthy horses that underwent electrical stimulation of the thyrohyoideus muscles. Methods: Horses underwent bilateral hypoglossal nerve block or electrical stimulation of the thyrohyoideus muscles. Positions of the basihyoid bone, ossified part of the thyroid cartilage, and articulations of the thyrohyoid bones and thyroid cartilage were determined in ...
Unilateral cerebellar hypoplasia and mesencephalic malformation in a Hanoverian foal. Neurological cases, especially in foals, are rare in the daily practical work. The most common causes are traumata and infectious diseases of the central nervous system (CNS). This case report provides further insights into the wide spectrum of possible neuropathological lesions by detailing a complex malformation with unilateral neurological signs that occurred later post natum. Thus, clinicians should also be aware of malformations in case of respective neurological patients. A Hanoverian foal was presented with progressive ataxia. General and blood examination revealed no further alteration...
