Neurological Exam and Localization

1. Neurological Exam and Localization BMS 81500 Rebecca A Packer, MS, DVM Diplomate ACVIM (Neurology)

2. Objectives • Perform a complete neurological exam • Understand the afferent and efferent pathways involved in the neuroexam • Perform neuroanatomic localization based on neuro exam findings

3. Neurological Examination(Goal/Objective) • Determine presence/absence of neurologic disease • Determine neuroanatomic localization • Intracranial • Forebrain, brainstem, cerebellum • Spinal cord • C1-C5, C6-T2, T3-L3, L4-S3 • Neuromuscular disease • Peripheral nerve, muscle, NMJ • Multifocal disease • Deficits cannot be explained by single lesion

4. Neurological Examination(Tools of the Trade) • Pleximeter • Hemostats • Trans-illuminator / LED light • Penlight often not bright enough • Cotton swab

5. Neurological Examination(Components) • Observation • Mentation, behavior, involuntary movements • Gait, posture • Postural reactions • Reflexes • Cranial nerve evaluation • Palpation • Sensory evaluation

6. Mental Status Classification • Normal • Depressed • Obtunded • Stuporous • Comatose • Other • Disoriented, delirious, loss of house-training, aggression, head-pressing, circling, fly-biting, tail-chasing, etc. Appropriate...or inappropriate?

7. Posture • Head position • With respect to gravity/ground (horizon) • With respect to axis of body • With respect to direction of movement • Tilt, turn, ventroflexion, dorsiflexion • Subtle abnormalities • Look from above or behind the pet • Look at ear position • Look at eye position • Head tilt vs. head turn

8. Posture • Trunk and limb position • Position of body with respect to gravity • Leaning, falling, rolling • Wide-based (or narrow-based) stance • Decreased/increased tone • Deviation of spine

9. Gait • Gait evaluation • Walk • Trot • Evaluate from rear, front, and side views • Normal or abnormal? • Is it neurological?

10. Gait • Lameness • Paresis (weakness) or plegia (paralysis) • Ataxia (incoordinated, irregular gait) • Dysmetria • Circling • Pacing • Exercise intolerance

11. Postural Reactions • Evaluate proprioception • Position of body/limbs in space • We evaluate the patient’s response • These are NOT local reflexes • They are responses • Lesions can be peripheral nerve, spinal cord, brainstem, or contralateral forebrain • Record as normal, delayed, or absent

12. Postural Reactions • Conscious proprioceptive placing (CP) • Hopping • Tactile placing • Visual placing • Hemistanding/hemiwalking • Extensor postural thrust • Wheelbarrowing • Remember…these are responses to proprioceptive stimuli, NOT reflexes

13. Postural Reactions • Conscious proprioceptive placing (CP) • Method • “Knuckle” paw and evaluate replacement • Speed and consistency of replacement/correction • Be gentle to avoid giving strong stimulus • MUST support body weight in normal stance • Eliminate need for load bearing in “lame” animals • Leaning may cause false deficits • Look for dorsal scuffing of nails • Normal response is rapid, consistent correction

14. Postural Reactions • Hopping • Method • Maintain natural body position • Force weight-shift to limb being tested • Push sideways to change center of gravity • Normal response is rapid correction (“hopping”) • If abnormal, consider: • Neurological disease • Systemically ill/weak patient

15. Postural Reactions • Visual placing • Method • Hold animal at table edge from all orientations • Normal response is to extend limbs to place paws • Tactile placing • Method • Similar to above except eyes covered • Touch edge of paws to table edge as stimulus • Normal response is rapid, correct placement of paws

16. Postural Reactions • Hemistanding/hemiwalking • Method • Shift weight to thoracic and pelvic limbs of one side • Maintain natural body position • Push animal laterally • Normal response is alternating step between thoracic and pelvic limb

17. Postural Reactions • Extensor postural thrust • For small patients only • Method • Hold patient upright around axillary/thoracic area • Hold them suspended above ground • Shift pelvis under them while lowering toward ground • Normal response is to extend limbs to reach for floor, and step backwards with alternating paws

18. Postural Reactions • Wheelbarrowing • Method • Perform with head upward • Prevents visual compensation • Forces use of proprioceptive cues • Shift weight to thoracic limbs • “Walk” patient forward • Normal response is alternating placement of paws without scuffing or dragging • May identify subtle thoracic limb deficits • May identify forebrain disease

19. Spinal Reflexes • Myotatic reflexes • Thoracic limb • Biceps • Triceps • Extensor carpi radialis • Pelvic limb • Patellar • Cranial tibial • Gastrocnemius • Flexor withdrawal reflexes • Cutaneous trunci reflex • Perineal reflex Grading scale 0 = absent, areflexia 1 = decreased, hyporeflexia 2 = normal 3 = hyper-reflexia 4 = hyper-reflexia with clonus or crossed-extension

20. Spinal Reflexes • Myotatic reflexes • Monosynaptic pathway • Stimulus activates stretch receptors (muscle spindle) • Impulse travels up afferent (sensory) nerve • Synapses in grey matter of spinal cord • Impulse travels down efferent (motor) nerve to muscles Muscle

21. Spinal Reflexes • Biceps reflex • C6-C8 – musculocutaneous n. • Strike distal tendon of biceps • Tendon must be tight • Contraction of biceps brachii and brachialis muscles

22. Spinal Reflexes • Triceps reflex • C7-T1 – radial n. • Stimulate distal tendon of triceps • Tendon must be tight • Contraction of triceps muscle • Extension of elbow

23. Spinal Reflexes • Extensor carpi radialis reflex • C7-T1 – radial n. • Strike extensor carpi muscle belly • Extension of carpus

24. Spinal Reflexes • Patellar reflex • L4-L6 – femoral n. • Stimulate patellar tendon • Extension of distal limb

25. Spinal Reflexes • Cranial tibial reflex • L6-L7 – peroneal branch of sciatic n. • Stimulate cranial tibial muscle belly • Flexion of hock

26. Spinal Reflexes • Gastrocnemius reflex • L7-S1 – tibial branch of sciatic n. • Stimulate common calcanean tendon • Contraction of semimembranosus, semitendinosus muscles

27. Spinal Reflexes • Flexor withdrawal reflexes • Polysynaptic pathways • L6-S1 pelvic limb – sciatic n. • C6-T1 (C5-T2) thoracic limb – all nerves • Still remains within intumescence • Evaluate • Strength of withdrawal • Flexion at all joints of limb • Remember… • Withdrawal of limb does NOT require sensory perception

28. Spinal Reflexes • Flexor withdrawal reflexes • Hyper-reflexia is based on crossed-extension • Reflexive contralateral limb extension during flexor withdrawal • Normally present, but moderated • Disinhibited with UMN lesion

29. Cutaneous Trunci Reflex • Afferent (sensory) • Sensory dermatome at level of pinch • Efferent (motor) • C8-T1 • Lateral thoracic nn. to cutaneoustrunci mm. • Requires superficial sensation to be intact • a.k.a., “Panniculus reflex”

30. Spinal Reflexes • Perineal reflex • Pudendal n. (external sphincter) • Afferent – pinch perineal area; rectal exam • Efferent – constriction of anal sphincter

31. Spinal Reflexes • Be aware, not all reflexes give reliable results • Thoracic limb • Flexor withdrawal is reliable • Pelvic limb • Flexor withdrawal is reliable • Patellar reflex is usually reliable • Caviat – some geriatric patients, some stifle disease • All other reflexes are unreliable • May not be elicited in some normal animals • May be mechanically elicited regardless of nerve function

32. Sensory Evaluation • Superficial pain perception • Pinching skin between toes (webbing) • Autonomous zones of limb • Deep pain perception • Pinching across bone of digit / toe • Check all toes and tail if LMN disease • Digits innervated separately • Quick pinch; helpful if element of surprise

33. Sensory Evaluation • Pain perception vs. withdrawal reflex • Positive response to pain perception is conscious awareness • Cry, turn, bite • Withdrawal is a local reflex and NOT a positive response • e.g., animals with transected irreparable spinal cord injury may still have normal withdrawal, but NOT have pain perception

34. Cranial Nerve Evaluation

35. Cranial Nerve Evaluation • Know cranial nerves and their functions • Know components of pathway involved • Approach CN exam as a mini problem list • List components of every abnormal CN test • Compare to find common component

36. Cranial Nerve Evaluation • Olfaction • Afferent – CN I • Test ability to smell • Twitching motion of nose is response to receiving olfactory information • Indicates positive test • Difficult to assess unilateral deficits • Do not use noxious smells (e.g., alcohol) • These stimulate CN V and give false test result • Use “good” smells instead (e.g., food)

37. Cranial Nerve Evaluation • Menace Response • Response, not reflex • Afferent – CN II, forebrain • Efferent – CN VII, cerebellum • Test each eye; cover opposite eye • Threatening gesture toward eye using hand • Try to minimize effects from air current • Do not touch whiskers; must be visual stimulation not tactile

38. Cranial Nerve Evaluation • Pupillary Light Reflex (PLR) • Afferent – CN II • Efferent – CN III • Direct and consensual constriction • If poor constriction, consider • True lesion of CN II or III • Iris atrophy (effector muscle) • Pharmacologic interference • Stress related sympathetic discharge (dilation)

39. Cranial Nerve Evaluation • Pupil size, symmetry • Afferent – CN II • Efferent – CN III, sympathetics • Anisocoria • Which eye is abnormal??? • Dark adapt • Light adapt • Pharmacologic testing

40. Cranial Nerve Evaluation • Horner’s syndrome • Miosis, ptosis, enophthalmos, elevated 3rd eyelid

41. Cranial Nerve Evaluation • Horner’s syndrome • Sympathetic lesion • Consider whole pathway • Midbrain origin, brainstem, spinal cord, brachial plexus (T1-T3 nerve roots), mediastinum, soft tissues of neck (vago-sympathetic trunk), petrous temporal bone, along CN V ophthalmic br. to retrobulbar area • the smooth muscle of the periorbita • the eyelids (including the 3rd eyelid) • the iris muscles (particularly the dilator of the pupil)

42. Cranial Nerve Evaluation • Facial sensation/Palpebral reflex • Afferent – CN V • Efferent – CN VII • Ophthalmic, maxillary, and mandibular br. • Touch medial canthus, lateral canthus, inner pinna, and maxillary whiskers • Normal response is to blink • If no response, pinch skin in those areas and note vocalization or conscious response to painful stimuli to evaluate CN V branches

43. Cranial Nerve Evaluation • Nasal Stimulation • Response, not reflex • Stimulate inner, medial nares • Afferent – CN V ophthalmic br., forebrain • Response is conscious reaction to stimuli • Response should be symmetric • Abnormalities may be in CN V, or forebrain

44. Cranial Nerve Evaluation • CN V motor branch – muscles of mastication • Palpate masticatory and temporal muscles • Look for atrophy/symmetry of temporal m. • Evaluate jaw tone, ability to close jaw • Lesions cause “dropped jaw”

45. Cranial Nerve Evaluation • Resting strabismus • Efferent – CN III, IV, VI lesion • LR2 6, SO 4, all the rest 3 • Evaluated in neutral head position • CN III lesion – ventrolateral strabismus • CN IV lesion – rotation of globe • CN VI lesion – medial strabismus

46. Cranial Nerve Evaluation • Nystagmus • Afferent – CN VIII • Efferent – CN III, IV, VI • Physiologic (normal) nystagmus • “Doll’s eye”, oculocephalic reflex, optokinetic reflex • Normal • Occurs during horizontal or vertical head movement • Fast phase (“jerk” phase) in direction of head movement • Abnormal • Lack of physiologic nystagmus with CN III, IV, VI lesions

47. Cranial Nerve Evaluation • Spontaneous (abnormal) nystagmus • Nystagmus present while head is stationary • Occurs with CN VIII lesions • Classification of nystagmus • Horizontal • Rotary • Vertical • Direction is named for fast phase

48. Cranial Nerve Evaluation • Gag reflex • CN IX, X • Normal variability in tolerance • Important evaluation is sensation of pharynx • Evaluate pharyngeal/soft palate contraction • While there… • Evaluate jaw tone (CN V motor) • Evaluate tongue symmetry/atrophy (CN XII) • Evaluate tongue movement (CN XII)

49. Cranial Nerve Evaluation • Tongue symmetry, movement • CN XII • Atrophy • Deviation toward lesion

50. Neurolocalization