Neurological Disorders INAG 120 – Equine Health Management November 7, 2011 Photo © UC-Davis, Center for Equine Health

Overview The Equine Central Nervous System The Equine Central Nervous System Differentiating between neurological disease and lameness – The neurological exam Differentiating between neurological disease and lameness – The neurological exam EPM EPM EMND EMND EDM EDM CVM and Vertebral Fractures CVM and Vertebral Fractures Plant Toxicities Plant Toxicities Viruses – covered in separate lecture Viruses – covered in separate lecture

The Equine Central Nervous System Brain, brainstem, spinal cord Brain, brainstem, spinal cord Brain Brain –Enclosed and protected by the cranial cavity –Horse is amazingly trainable and possesses a remarkable memory –Possesses, integrates, and stores sensory information Brain Stem Brain Stem –Also called the lower brain, coordinates and controls respiration, blood pressure, and many other life processes Spinal Cord Spinal Cord –Connects the brain with the peripheral nerves –Many of the simpler motor responses occur as "spinal reflexes" without directly involving the higher levels of the nervous system.

The Neurologic Exam Goal: establish presence of neurologic problem and determine location Goal: establish presence of neurologic problem and determine location Cervical radiography Cervical radiography Cerebrospinal fluid (CSF) analysis Cerebrospinal fluid (CSF) analysis Electrodiagnostic testing Electrodiagnostic testing Physical Exam Physical Exam –5 categories

Neurologic Physical Exam 1. Head and Mental Status 2. Gait and Posture Postural reactionsPostural reactions Spinal reflexesSpinal reflexes Gait abnormalitiesGait abnormalities

Neurologic Exam…Localizing the problem 3. Neck and Forelimbs Gait abnormalities in all 4 limbsGait abnormalities in all 4 limbs 4. Trunk and Hindlimbs If limited to hind limbs, damage done caudal to 2 nd thoracic spinal cord segmentIf limited to hind limbs, damage done caudal to 2 nd thoracic spinal cord segment 5. Tail and Anus Abnormal use  lesion caudal to sacral vertebraeAbnormal use  lesion caudal to sacral vertebrae

Video of Horse Suffering from Neuro-EHV

Neurological Disorders Nervous tissue does not respond well to damage Nervous tissue does not respond well to damage Capacity for repair is limited Capacity for repair is limited

Equine Protozoal Myeloencephalitis (EPM) Protozoan Parasite Sarcocystis neurona Neospora hughesei Protozoan Parasite Sarcocystis neurona Neospora hughesei Infects spinal cord and brain Infects spinal cord and brain Infection does not mean clinical disease! Infection does not mean clinical disease! Hosts and carriers Hosts and carriers  Doesn’t pass horse- horse

EPM… Clinical Signs: Clinical Signs: –Asymmetric lameness –Asymmetric facial paralysis –Muscle atrophy –Weakness –Ataxia Photos © UC-Davis, Center for Equine Health

EPM… Risk Factors: Risk Factors: –< 6 years old –Season (higher in spring and summer) –Region –Opossums –Previously diagnosed cases on farm –Stress –Racehorses and show horses Photo ©

EPM… Diagnosis: Diagnosis: –POLITICAL –MUST BE A CLINICAL DIAGNOSIS with both clinical signs and changes in cerebrospinal fluid –Can show antibodies in CSF from previous exposure (not necessarily infection) –Must rule out wobbler and equine degenerative myeloencephalopathy

EPM… Treatment: Treatment: –Feasible if damage is not too severe –Marquis –Navigator –Long term therapy with anti-folic-acid drugs such as TMS (Trimethoprim-sulfadiazine) plus pyrimethamine –Vitamin E may be given for antioxidants –Levamisole may be given to stimulate immunity –DMSO for anti-inflammatory Prognosis depends on severity of symptoms; horses often show permanent neurological damage Prognosis depends on severity of symptoms; horses often show permanent neurological damage

More on EPM Opossum = definitive host Opossum = definitive host –Up to 1 billion sporocysts in one gram of opossum feces Horse = aberrant host Horse = aberrant host Raccoons, cats, armadillos and skunks = intermediate hosts Raccoons, cats, armadillos and skunks = intermediate hosts Photo © Dr. Martin Furr, VMRCVM

EPM Prevention Keep feed and water sources “clean” Keep feed and water sources “clean” –Make feed unavailable to wildlife Confine horses Confine horses Limit stress Limit stress Vaccine? Vaccine?

Equine Motor Neuron Disease Degenerative disorder of lower motor neurons Degenerative disorder of lower motor neurons First described in 1990 First described in 1990 Most likely caused by Vitamin E deficiency Most likely caused by Vitamin E deficiency Affects horses over the age of 2 Affects horses over the age of 2

EMND – Clinical Signs Weight loss Weight loss Acute onset of trembling Acute onset of trembling Constant shifting of weight in hind legs Constant shifting of weight in hind legs Excessive recumbency Excessive recumbency Elevated tail + abnormally low carriage of head and neck Elevated tail + abnormally low carriage of head and neck 40% horses deteriorate and are euthanized 40% horses deteriorate and are euthanized 40% respond to treatment 40% respond to treatment 20% remain debilitated 20% remain debilitated Photo © Dr. Martin Furr, VMRCVM

EMND – Diagnosis Biopsy of tail head Biopsy of tail head Blood tests: Blood tests: –Mild-moderate increase in CK and AST –Vit. E consistently low –Selenium normal –Vit. A low-normal –Serum iron = high Spinal cord Spinal cord –Copper is increased –Low Vitamin E Glucose absorption impaired Glucose absorption impaired

EMND – Treatment Horses with EMND = dead motor neurons and alive but dysfunctional motor neurons Horses with EMND = dead motor neurons and alive but dysfunctional motor neurons If numbers of dysfunctional > dead  clinical imrovement If numbers of dysfunctional > dead  clinical imrovement Seems to affect neurons that supply muscles with highly oxidative type 1 fibers Seems to affect neurons that supply muscles with highly oxidative type 1 fibers Feed green forages Feed green forages Vitamin E supplementation (commercial concentrates already have added E due to recent research) Vitamin E supplementation (commercial concentrates already have added E due to recent research)

Equine Degenerative Myeloencephalopathy VERY similar to EMND but a distinctly different disorder VERY similar to EMND but a distinctly different disorder  Most commonly seen in sucklings and weanlings; very rarely after the age of 2 Loss of neurons in the brain stem and spinal cord Loss of neurons in the brain stem and spinal cord Vitamin E deficiency, along with a familial component Vitamin E deficiency, along with a familial component Vitamin E has a protective effect against oxidative damage in the spinal cord of horses with the neuroanatomical site differing based on age? Vitamin E has a protective effect against oxidative damage in the spinal cord of horses with the neuroanatomical site differing based on age?

Vertebral Fractures Treatment possibilities depends on nature, extent and stability of fracture Treatment possibilities depends on nature, extent and stability of fracture Each case must be observed individually Each case must be observed individually Forelegs unstable  located in neck or front of thoracic spine Forelegs unstable  located in neck or front of thoracic spine Mild cases may resolve on their own Mild cases may resolve on their own

Cervical Vertebral Malformation “Wobbler” Syndrome Leading cause of non-infectious spinal cord ataxia Leading cause of non-infectious spinal cord ataxia Especially seen in rapidly-growing well-nourished horses Especially seen in rapidly-growing well-nourished horses Male > Female Male > Female Highest incidence in Thoroughbreds Highest incidence in Thoroughbreds Evidence that it’s due to aberrations of bone development Evidence that it’s due to aberrations of bone development Excess forces and trauma may predispose the animal to deformities Excess forces and trauma may predispose the animal to deformities

Wobblers… Cervical Vertebral Instability (CVI) Cervical Vertebral Instability (CVI) –6-12 months old –Instability of cervical joint  excess movement  pressure on spinal cord Cervical Static Stenosis (CSS) Cervical Static Stenosis (CSS) –Older horses, usually 1-4 years –Degenerative joint disease of less mobile joints of neck –Excess bone impinges on spinal cord

Wobblers… Clinical Signs/Diagnosis: Clinical Signs/Diagnosis: –History of recent trauma –Signs of ataxia –“Hindlimbs affected worst and first” –Weakness –Spinal cord lesions usually symmetrical Treatment: Treatment: –NSAIDS, steroids, or DMSO to reduce inflammation –Stall rest

Wobblers Video Yudc&feature=related Yudc&feature=related

Sudan Grass Toxicity Consumption of sudan grass (Johnson grass, shattercane) Consumption of sudan grass (Johnson grass, shattercane) Urinary incontinence (no bladder control) Urinary incontinence (no bladder control) Ataxia and paresis Ataxia and paresis Treatment usually unsuccessful once signs are prominent Treatment usually unsuccessful once signs are prominent Early cases recover when removed from pasture Early cases recover when removed from pasture

Johnsongrass, Sudangrass

Brackenfern Moderately toxic Moderately toxic Plant contains thiaminase Plant contains thiaminase –All plant parts, especially roots –Causes Thiamin deficiency Blindness, depression, weight loss, staggering Blindness, depression, weight loss, staggering Rx: Thiamin supplementation, blood transfusion for bone marrow destruction Rx: Thiamin supplementation, blood transfusion for bone marrow destruction Pteridium aquilinum

Brackenfern