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Chapter 6Neurologic Assessment

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Learning Objectives

After reading this chapter you will be able to: Define key terms related to neurologic

assessment Describe functional anatomy of the

nervous system Explain the cortical function of different

lobes of the brain Describe common techniques used to

assess the mental status

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Learning Objectives (cont’d)

Describe functions of the brainstem, the cerebellum, and 12 pairs of cranial nerves

Identify the parameters necessary to obtain a Glasgow Coma Scale and be able to interpret the results

Describe common techniques to assess the cranial nerves, the sensory system, the motor system, coordination, and gait

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Describe the importance of assessing sedation and delirium in the ICU

Describe techniques used to assess deep, superficial, and brainstem reflexes

Explain the relationship between vital signs and neurologic status

Identify the importance of ICP monitoring and the value of assessing cerebral perfusion pressure

Learning Objectives (cont’d)

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Overview

Injuries of the nervous system May affect respiratory system May affect patient cooperation with respiratory

procedures History may indicate nature of dysfunction Exam localizes and quantifies severity of

dysfunction Initial interaction with patient is first step in

neurologic assessment

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Overview (cont’d)

Neurologic assessment evaluates: Mental status Cranial nerve function Motor system Coordination Sensory system Reflexes

Meaningful neurologic assessment requires adequate stimulation

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Functional Neuroanatomy

Neurologic system Central nervous system

• Brain: cerebrum, brainstem, cerebellum• Spinal cord

Peripheral nervous system• Cranial nerves• Spinal nerves

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Functional Neuroanatomy (cont’d)

Functional division Sensory system (afferent) Motor system (efferent)

Cerebrum Functions: movement, LOC, ability to speak

and write, emotions, memory

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Brainstem Consists of midbrain, pons, medulla oblongata Most cranial nerves originate in brainstem Regulation of heart rate, blood pressure, and

breathing

Functional Neuroanatomy (cont’d)

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Cerebellum Posterior part of the brain Responsible for equilibrium, muscle tone, and

coordination Cerebellar lesions cause:

• Loss of coordination (ataxia)• Tremors• Disturbances in gait and balance

Functional Neuroanatomy (cont’d)

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Spinal cord From base of the brain down to L1 (45 cm) Connects brain to the body for motor and

sensory function 31 spinal nerves

• C1-C8, T1-T12, L1-L5, S1-S5, one coccygeal• Posterior (dorsal) roots = sensory• Anterior (ventral) roots = motor

Functional Neuroanatomy (cont’d)

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Spinal cord Herniated vertebral disk is the most common

spinal nerve root pathology Involvement of multiple nerve roots

• Guillain-Barré Phrenic nerves arise from spinal roots C3 to

C5• Damage can result in diaphragmatic paralysis

Functional Neuroanatomy (cont’d)

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Mental Status and LOC

LOC and mentation: most important parts of the neurologic exam

Changes due to CNS dysfunction Initial goal of exam is to determine

patient’s awareness Starts with patient encounter

Compromise of LOC may be due to: Generalized dysfunction (e.g., overdose) Abnormality in specific area

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Glasgow Coma Scale (GCS)

Most widely used instrument to quantify neurologic impairment

Test Motor response Verbal response

• Poorly suited for patients with impaired verbal response (e.g., aphasia, hearing loss, tracheal intubation)

Eye opening

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Glasgow Coma Scale (cont’d)

Scale goes from 3 (deep coma) to 15 (fully awake)

GCS of 12-15 = non-ICU observation GCS of 9-12 = significant insult GCS <9 = severe coma = requires

endotracheal intubation

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Mini-Mental State Examination

MMSE or Folstein test 30-point questionnaire to assess cognition Samples various functions

• Arithmetic, memory, orientation Score interpretation

• >27/30 = normal• 20-26 = mild dementia• 10-19 = moderate dementia• <10 = severe dementia

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Sedation and Delirium in the ICU

Delirium occurs in 60% to 80% of mechanically ventilated patients

Associated with: Longer hospital stay Higher mortality Poor long-term cognitive function

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Sedation and Delirium in the ICU (cont’d)

Richmond Agitation Sedation Scale (RASS) Titrate sedation

Confusion Assessment Method for the ICU (CAM-ICU) Evaluates delirium

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Cranial Nerve Exam

12 cranial nerves = sensory and motor function Midbrain (CN III, IV) Pons (CN VIII) Medulla (CN IX to XII)

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Cranial Nerve Exam (cont’d)

Ipsilateral findings except on CN V Acoustic problem (CN VII, VIII) Pupillary response (CN II, III) Corneal reflex (CN V, VII) Gag reflex (CN IX, X)

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Sensory Exam

Somatosensory pathways Spinothalamic (ST) = pain, temperature Dorsal column-medial lemniscus (DCML) =

vibration, position sense (proprioception) Evaluates ability to perceive sensations

with eyes closed Assessment of light touch, pinprick, and

temperature

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Motor Exam

Patient’s ability to move on command Motor strength and range of motion Scale from 0 (no movement) to +5 (full

range of motion and full strength) If unconscious = response to pain

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Motor Exam (cont’d)

Upper motor neuron (UMN) Babinski’s sign, hyperreflexia, clasp-knife Decorticate and decerebrate posture

Lower motor neuron (LMN) Loss of strength, tone and reflexes, muscle

waste and fasciculations

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Deep Tendon Reflexes

Evaluate spinal nerves Triceps, biceps, brachioradialis, patellar,

Achilles tendon Westphal’s sign = absence of patellar reflex

Scale from 0 (no reflex), +2 (normal), +5 (hyperreflexia)

Myasthenia gravis and botulism have abnormal deep tendon reflexes

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Superficial Reflexes

Plantar reflex Tested when suspected L4-L5 or S1-S2

injury Babinski’s sign

Dorsiflexion of the great toe with fanning of remaining toes

Normal in children 12 to 18 months of age

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Brainstem Reflexes

Gag reflex (CN IX, X) Its absence may increase risk for aspiration

Cough reflex (CN X)

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Brainstem Reflexes (cont’d)

Pupillary reflex (CN II, III) PERRLA

• Pupils equal round reactive to light and accommodation

Anisocoria Myosis = pontine hemorrhage, narcotics Mydriasis = brain injury, anticholinergics Mid-position fixed pupils = severe cerebral

damage Corneal reflex (CN V, VII)

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Coordination, Balance, and Gait

Assessment of cerebellar function Patient should be able to follow commands

during exam Dysmetria = under- and overshooting of goal-

directed movements Romberg test = balance

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Vital Signs and Neurologic System

Brainstem = breathing Lesions from cerebrum to cervical cord

cause changes of breathing patterns Cheyne-Stokes respiration

Intracranial cause, hypoxemia, cardiac failure

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Vital Signs and Neurologic System (cont’d)

Ataxic breathing: marker of brainstem dysfunction

Increased ICP = Cushing’s triad Hypertension, widening pulse pressure,

bradycardia, bradypnea

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Intracranial Pressure Monitoring

Indications Monitor patients at risk for life-threatening

intracranial hypertension Monitor evidence of infection Assess effects of therapy for reducing ICP

Although hyperventilation decreases ICP, cerebral perfusion pressure (CPP) is the most critical element to monitor