Equine Nervous System Examination (Neuro 1) PDF

Equine nervous system: the examination (Neuro 1) Laura Waitt, DVM, DACVIM 1662 Objectives  Students will demonstrate competence in performing a neurological examination on horses.  With a focus on localization, personnel safety, and biosecurity  Including spinal ataxia and grading schem...

Equine nervous system: the examination (Neuro 1) Laura Waitt, DVM, DACVIM 1662 Objectives  Students will demonstrate competence in performing a neurological examination on horses.  With a focus on localization, personnel safety, and biosecurity  Including spinal ataxia and grading scheme  Including cranial nerves  Students will have knowledge of the pathophysiology and diagnosis of Horner’s syndrome When to perform a neurological examination  Is neurological disease present?  If so, where is the process localized in the nervous system?  “Snapshot” of the disease vs. exams repeated over time to aid in determination of disease progression and prognosis.  Limitations  Subjective  Subtle changes in personality or mentation may be impossible to detect  Listen to your owner  Range of normal  Age and breed  Sedatives effect results  Alpha 2 agonist Information to gather  Chief complaint  Ie: Seizures, weakness, won’t hold up leg for farrier, cross canters behind, unexplained wounds, clumsiness  Signalment  Species, breed, age  History  Define the clinical course  Treatments or diagnostics done up until this point  Physical examination  Systemic diseases can cause neurologic diseases Assessment of mentation and behavior  Watch the animal while you are getting a history, or a video from the owner  Fear, anxiety, aggression unconscious  Dullness, obtundation, stupor  Clinical neuroanatomy  Mental awareness is a function of the higher centers in the brain  Dullness < lethargy < obtundation < stupor < coma  Cerebral cortex  Sensory information reaches the consciousness in the cortex  Voluntary movements initiated here  Ascending reticular activating system (ARAS)  Located throughout the medulla, midbrain and thalamus  Thalamus is the most common location of progressive stupor  Sensory information from the body travels via the ARAS (and other pathways) to the cortex  Assessment of posture  Observe the position of the head and limbs in space  Heat tilt: look for strabismus and nystagmus, blindfold key  Nearly always vestibular disease 1dentit as  Towards the lesion in peripheral disease, and nearly all central disease  cerebellum/midbrain exceptions  Nystagmus “runs away from the disease”  Fast phase away, slow phase towards same me  Head turn  Cerebral and thalamic disease It  Towards the side of the lesion Assessment of posture back ofthe arching  Schiff-Sherrington syndrome: forelimb extensor rigidity without opisthotonus  Thoracolumbar spinal cord disease commonwithcaraccidents  Opisthotonus: head and neck are in extreme extension  Midbrain disease: decerebrate rigidity- all four limbs have extensor rigidity  Cerebellar disease: Decerebellate rigidity- just forelimbs have extensor rigidity, intention tremors  Spinal ataxia- base wide stance, knuckling, sway, dog-tracking Localize the lesion  Mentation change- cerebral  Intention tremors- cerebellar  Ataxia with no mental change – spine  Hind limbs alone – thoracolumbar/sacral spine H  Front limbs and hind limbs (up to a grade worse) – cervical spine  Front limbs worse than hind limbs – thoracic intumescence  No limb reflexes are possible  Hard to distinguish upper from lower motor neuron disease  Cranial nerves  12 pairs of nerves innervate structures of the head  Innervates structure on same side of head (ipsilateral)  Central control of these nerve comes from the opposite cerebral cortex (contralateral)  All originate from the brainstem except CN I and II  Brainstem includes midbrain, pons, and medulla  Review from your 1604 lecture or read Hahn paper.  Numerical order  Groupings by function Localizing lesions in the visual pathway  Optic nerve lesions or primary eye issue (both vision and PLR abnormal)  Cortical lesions (vision is affected but PLR is normal)  *CAN BE BLIND WITH NORMAL PLR*  Efferent arms lesions (vision is normal but PLR is abnormal) Sympathetic innervation to the eye:  Responsible for dilation of the pupil, retraction of the third eyelid, retraction of the upper eyelid and rostral protrusion of the globe.  Horner’s syndrome is caused by disruption of sympathetic innervation to the globe/periorbital area  Clinical signs  Ptosis (droopy lid)-this is most consistent  Miosis (pupil constriction)  Enophthalmos (globe withdrawn)  Protrusion of the 3rd eyelid  Sweating of the ipsilateral face and cranial aspect of the neck may be observed Horner’s syndrome  Guttural pouch and cranial cervical ganglion lesions will result in sweating of the face and cranial neck (C2).  Lesions involving the sympathetic trunk in the neck can causes sweating of the face and neck (C3-4).  Lesions in the thoracic inlet can result in seating down to the shoulder (T1). Anisocoria: which side is normal? With no primary ocular lesion  Darkened room for several minutes then expose to a dim light  If both pupils dilate to equal size, then sympathetic innervation is normal  The pupil that was initially more dilated is abnormal due to a CN III lesion  If pupils do not dilate equally then sympathetic innervation is abnormal  The eye with a smaller pupil (miosis) is abnormal, caused by Horner’s syndrome Dimlightdilationtesting on function Reflexes  Many spinal reflexes can only be performed in recumbent animals (ie: Patellar reflex)  Which means we often cannot tell if upper or lower motor neuron  Hyper reflexive tends to be upper motor neuron  Hypo reflexive tends to by lower motor neuron  Panniculus or Cutaneous trunci reflex – “fly twitch”  This will be absent if there is a lesion anywhere cranial to test  Cervicofacial reflex  Local spinal cord or facial nerve deficit  Lordosis/Kyphosis response  Braced indicates musculoskeletal pain  Loss of balance and trouble extending after drop  Perianal reflex and anal tone  Pump the tail to evaluate muscular strength  When the perianal area is touched/pinched the anus contracts ie: taking a temperature  A deficit here indicates cauda equine or sacral disease Neck stretching  This is a subjective evaluation of flexibility, stiffness, and/or pain of the neck.  Abnormalities of gait  Spinal ataxia  Looks more normal the faster they travel  Hypermetria: excessive lifting of a limb, upper motor neuron  Breed standards can affect interpretation if symmetrical friesians Quarterhorses Normal  Hypometria: weakness and dragging, lower motor neuron  Intention tremor: most easily noted when feeding a horse  Tends to be cerebellar disease Spinal ataxia  Grade 0  Normal  Grade 1  Extremely mildly affected, performance limiting, a professional has to perform multiple tests to determine evidence of dysfunction  Grade 2  Mildly affected, easily appreciable to a professional, performance limiting  Grade 3  Obvious to a layperson, abnormalities notable at rest  Grade 4  Severely ataxic and could fall during the examination  Dangerous to be around, advise personnel and clients appropriately  Grade 5  Recumbent and unable to stand  Dangerous to be around, advise personnel and clients appropriately  Can only be managed appropriately at a referral facility Walking in a straight line  Observe for cadence/consistency  Observe for foot placement/consistency  Observe for path of limb flight/consistency Walking in circles  Wide circles, tight circles, and serpentines then stopping suddenly to observe for a return to a normal stance  Looking for: pivoting, circumduction, low or high foot flight, toe dragging Trotting in a straight line  Observe for cadence/consistency  Observe for foot placement/consistency  Observe for path of limb flight/consistency Cantering in a circle  Normal is a cadenced 3 beat gait  Neurologic horses may “bunny hop” behind or “cross canter”  Note* that the faster horses go, the more normal they may appear  The racetrack is a perfect example Tail pull  Stand horse square  Pull tail which initiates an extensor reflex  A poor response suggests a lower motor lesion at L3-5.  This is a subjective measure of strength  While horse is walking  Only pull when closest hind foot is on the ground  Pull 3 times separated by a few strides  Assess strength, learning, and recovery  Don’t get kicked. Walking with head elevated  This removes visual compensation  Normal horses will just keep walking  Abnormal horses will start cat walking or try to look Placements: We don’t really do it anymore  Tests conscious proprioception, theoretically.  Placing  Hopping  We don’t do hemi walking or wheel barrowing in horses  You are welcome to try this, but I don’t suggest it. Obstacles- hills or curbs  Measures their functional proprioception  Some horses are clumsy, this is not considered as useful anymore. How we think we look… Actual footage…. Autonomous zone on  This is important for horses with a single paretic limb.  Radial nerve doesn’t have a consistent zone. Ei Questions?  [email protected]