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

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.