Page 24 - Demo

Dementia sounds serious butalso covers mild changes in ahorse%u2019s alertness and behavior:%u2022 Depression: a decrease in alertness ofthe horse.%u2022 Semicoma: Severe depression, a profound lack of reaction to what is happening around the horse.%u2022 Aimless wandering, circling, headpressing: The horse moves around butseems unaware of his surroundings, if hecomes to a wall he may continue to tryand move forward.%u2022 Seizure: brain dysfunction due to excessive neuronal discharge and usually associated with some reduction or loss ofconsciousness. The horse may appear tojust faint, and there may or may not bespasms of the muscles.%u2022 Delirium: An altered state of consciousness, consisting of confusion, distractibility, disorientation, disorderedthinking, defective perception (illusionsand hallucinations), prominent hyperactivity, agitation or aggression.Behavioral changes indicate a diseaseof the brain, more specifically the cerebrum or brain stem. Because the brain isclosely integrated with the cranial nervesoften these are affected also. Not all casesof dementia, particularly mild depression,are caused by primary brain disease. Bothfever and colic can cause depression, andliver disease can induce severe brain dysfunction. Not all extreme behaviors or behaviorial changes are a indication ofdisease. Differences exist between individuals, sexes, breeds and ages. Behavioral changes may be seen at the onset ofestrus in mares, aggressive behavior maybe seen in stallions, and changes in tackmay lead to behavior changes (head shaking, chewing) in the performance of racehorses. Certainly pain anywhere in thebody can cause behavorial changes, butusually this is easily interprted as a horse'sreaction to peripheral pain.If dementia is present, the brain has aprimary lesion whether the horse is ataxicor not. This article describes the diseasesof the brain and provides links to articleson these disorders.Dementia: Changes in BehaviorA thorough physical exam of the wholehorse including blood chemistries and bloodcount and differential are indicated whenever signs of nervous system disease occur.A neurological exam of the cranial nervesand signs of ataxia should be completed. Dementia can be localized to the cerebrum orbrainstem by the type of change in behavioror accompanying gait changes:%u2022 Cerebrum: Mild depression, aimlesswandering, mild paresis, seizure, deliriumand blindness with a normal pupillarylight response (PLR) can be localized tothe cerebrum.%u2022 Brainstem: Severe depression, obtunded profound weakness,and semicoma can be localized to the reticularactivating system of the brainstem. Withdiffuse brain stem disease also presentmay be ataxia with spasticity in four limbsturning in narrow circles, and/or cranialnerve signs (strabismus, ptosis, ear droop,deviated muzzle, head tilt, and facial muscle atrophy).Cerebral Diseases: %u2022 Seizure is defined as episodic abnormal activity of the brain that results in alteration or loss of consciousness. Theremay or may not be muscles spasms withthe seizure. A common problem in horsesand foals, several forms are seen includingnarcolepsy where the horse falls asleepwhile standing.%u2022 Liver Failure/ Disease is the mostcommon metabolic cause of cerebral disease. Horses with hepatoencephalopathypresent with dementia, head pressing,aimless wandering, star gazing, and insome cases, icterus. Frequently, theseproblems are most pronounced followingfeeding, especially after a high proteinmeal. Increased serum ammonia and aromatic amino acids are thought to diffuseacross the blood-brain barrier and act asfalse neurotransmitters, leading to the typical clinical problems. Hepatoencephalopathy in young horses can besecondary to portacaval shunts; thoughrare, portacaval shunts should be considered in stunted foals with hepatoencephalopathy.%u2022 Electrolyte Disturbances cause neurologic problems which occur sporadicallyin horses, however ,the predominantsymptom is usually one of muscularweakness:%u2022 Hypomagnesemia and hypocalcemiacan lead to signs of cerebral disease. Theseconditions can occur following stress, seDiagnosing Behavioral Changes, Dementia and Seizures In Horses by Robert N. Oglesby, DVM24 Arizona Horse Connection June, 2026continued on page 26 $('&%$#\#ffl'%u0003 fl