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1._Neurologic_Exam_-_Answers

The Ruminant Neurologic Exam

  • Presented by: Cynthia Xue, DVM, DACVIM (LAIM), Assistant Professor, Clinical Sciences

  • Contact: cxue@rossvet.edu.kn

Outline and Outcomes

  • Outline:

    • Neuroanatomy/physiology

    • The neurologic exam

    • Neurolocalization

  • Outcomes:

    • Recognize abnormal clinical signs associated with neurologic dysfunction

    • Emphasize neurolocalization skills

Neuroanatomy/Physiology

Central Nervous System (CNS)

  • Important structures:

    • Cerebrum

    • Cerebellum

    • Brainstem

    • Spinal cord

    • Reticular Activating System (RAS)

    • Spinal segments: C1-C5, C6-T2, T3-L3, L4-L6

    • Thalamus/Hypothalamus

Peripheral Nervous System (PNS)

  • Comprises everything outside the CNS:

    • Cranial Nerves (CN I-XII)

    • Lower Motor Neurons

    • Spinal Nerves

    • Nociceptors

    • Neuromuscular Junctions

Somatic Nervous System

  • Voluntary actions: Somatic sensory and motor fibers

Autonomic Nervous System

  • Involuntary actions:

    • Visceral sensory fibers

    • Visceral motor fibers

    • Sympathetic and Parasympathetic divisions:

      • Fight or Flight

      • Rest & Digest

Terminology

  • Nerves as "highways" for information transfer:

    • Afferent pathways: Sensory fibers relay info INTO the CNS

    • Efferent pathways: Motor fibers relay info FROM the CNS

  • Types of fibers:

    • Afferent: Somatic and visceral sensory fibers

    • Efferent: Somatic and visceral motor fibers

Clinical Correlate

  • Absent palpebral reflex (OS):

    • Affected CNs: Trigeminal (CN V) for afferent, Facial (CN VII) for efferent

    • Symptoms: Muzzle deviation, ear drop, ptosis OS

CN Fiber Types Overview

  • Vagus Nerve: Mixed fiber types pertaining to visceral functions.

  • Oculomotor Nerve: Primarily motor for pupillary dilation and globe position.

  • Spinocerebellar tracts: Afferent neurons relaying proprioception.

Clinical Correlate Analysis

  • Vagus Nerve Fiber Composition: SA, SE, VA, VE - all types involved.

  • False Statement: Parasympathetic and sympathetic nerves contain visceral afferent fibers, not only efferent.

Afferent and Efferent Neurons

  • Afferent Neurons: Carry sensory information from receptors in skin and organs to the CNS; cell bodies outside the spinal cord.

  • Efferent Neurons: Carry motor information from the brain to the PNS; cell bodies located in the ventral horn of the spinal cord.

Upper and Lower Motor Neuron (UMN & LMN) Concepts

  • UMNs: Cell bodies within the CNS; project to another CNS area.

  • LMNs: Cell body in brainstem/spinal cord; projects to organ/gland/muscle in PNS.

Clinical Correlation: Neurolocalization

  • Understanding neuroanatomy aids in diagnosing lesions affecting both UMN and LMN, showing signs of weakness related to both types.

The Neurologic Exam Overview

  • Described as an observational exercise (Fecteau et al. 2017).

Lesion Characterization

  • Aim of neurologic exam: One lesion should explain all clinical signs.

  • Utilize algorithms to differentiate lesions based on symptoms such as gait deficits, cranial nerve signs, and leg abnormalities.

General Assessment

  • Evaluation of mental status essential for differentiating intracranial vs extracranial lesions.

    • Key questions:

      • Awareness of presence?

      • Social interaction with herd mates?

Cranial Nerve Assessment

  • Assess functional aspects of cranial nerves:

    • Loss of sensory (afferent) vs motor (efferent) capabilities can indicate nerve damage.

Important Cranial Nerves

CN

Function

Assessment

I (Olfactory)

Smell

Not routinely performed

II (Optic)

Vision

Menace & PLR tests

III (Oculomotor)

Eye movement & pupil constriction

PLR and eye position

IV (Trochlear)

Eye movement

Eye position tests

V (Trigeminal)

Sensation & motor to masticatory muscles

Palpebral reflex

VI (Abducent)

Eye movement

Globe retraction

VII (Facial)

Facial expression

Facial symmetry and reflexes

VIII (Vestibulocochlear)

Balance & hearing

Response to noise

IX (Glossopharyngeal)

Sensory & motor to pharynx

Ability to swallow

X (Vagus)

Pharynx/larynx functions

Swallowing observation

XI (Spinal accessory)

Motor to cervical muscles

Muscle atrophy observation

XII (Hypoglossal)

Tongue movement

Tongue strength and symmetry

Muscle Mass and Tone Assessment

  • Myopathy may be indicated by asymmetry or atrophy, linking cranial nerve or LMN damage.

  • Common issues in cattle due to dystocia.

Spinal Reflexes

  • Withdrawal (Flexor) Reflex: Assess sensory and motor pathways in limbs by leg flexion in response to stimulus.

  • Patellar Reflex: Tests femoral nerve by assessing stifle extension upon tendon tapping.

Gait and Proprioception Assessment

  • Different assessment methods required for ruminants vs. smaller animals, especially in dynamic environments.

Nociception Overview

  • Pain response observations can be integrated into earlier exam portions for compliance.

  • Definitions of pain sensation levels: normal, decreased, absent.

Clinical Correlate: Nervous System Injury Analysis

  • Suspected nerve injuries to assess pain response in hind limbs, perineal reflexes, linking neuroanatomy to clinical signs.

Neuro-localization: Clinical Signs Identification

  • Recognizing clinical signs related to specific brain regions:

    • Cerebrum: behavioral changes, seizures, blindness.

    • Cerebellum: posture and ataxia without weakness.

    • Brainstem: cranial nerve abnormalities.

Summary of Cerebral and Cerebellar Dysfunctional Signs

Cerebral Dysfunction

  • Postures: Opisthotonus, head pressing.

  • Behavioral Manifestations: Abnormal vocalizations.

Cerebellar Dysfunction

  • Gait/Balance: Wide stance, truncal sway, ataxia.

  • Reflexes: Absent menace response, intention tremors.

Neurolocalization Summary

  • Recognize common clinical signs to specify lesions and relate them to neurological pathologies across different systems.