BIOE221 SN10 NeurologicalPNS · Dermatomes o A dermatome is a circumscribed skin area that is supplied mainly from one spinal cord segment through a ... (Magee 2008, p.155) (Magee

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BIOE221

Session 10

Neurological Assessment –

PNS Motor, Sensory

Examination and Reflexes

Bioscience Department


Session Objectives

o Review the major structures and functions of the nervous

system in order to be able to assess its motor, sensory

and integrative functions

o Identify the common symptoms relating to neurological

disorders

o Demonstrate examination of the neurological system by

assessing certain sensory and motor systems

o Recognise abnormal findings with these techniques

o Demonstrate examination of deep tendon reflexes

o Recognise abnormal findings with these reflexes


Spinal Cord

Sensory & Motor Tracts

(Tortora & Derrickson 2009, p.481)


Spinal Nerves

o The 31 pairs of spinal nerves arise from the length of the spinal cord and supply the rest of the body

• 8 cervical, 12 thoracic, 5 lumbar, 5 sacral and 1 coccygeal

o They are “mixed nerves”

• contain both sensory and motor fibres

o Sensory afferent fibres enter the cord through the posterior or dorsal roots

• See ‘dermatomes’

o Motor efferent fibres exit through the anterior or ventral roots

• The nerves exit the spinal cord in an orderly manner, each nerve innervating a particular segment of the body known as a myotome


Dermatomes

o A dermatome is a circumscribed skin area that is

supplied mainly from one spinal cord segment through a

particular spinal nerve

o Dermatomes overlap

o Useful landmarks

• thumb, middle and little finger – dermatomes of C6,

C7, C8

• nipple – at level of T4

• umbilicus – at level of T10

• groin – at level of L1


Dermatomes

(Tortora & Derrickson 2000)


Common Myotomes

(Magee 2008, p.155)

(Magee 2008, p.549)


Neurological Examination

o Last week

• Mental state

• Cranial nerves

• Motor system

o This week

• Sensory system

• Reflexes


Neurological Sensory System

o Always compare sensation bilaterally

• If you observe a definite decrease – map it out to

determine the dermatome or myotome affected.

o Tests could include

• Sharp / dull – pain and crude touch

• Light touch – Fine touch discrimination

• Stereognosis

– Ability to recognise objects by feel with eyes

closed



Light Touch(Jarvis 2016, p.652)

Sharp/Dull Test(Jarvis 2016, p.652)



Stereognosis(Jarvis 2016, p.654)

Stereognosis should always be tested with an object that is easily

identifiable. Astereognosis is the inability to identify the object and is

associated with sensory cortex lesions e.g. Stroke.


Common Patterns of Sensory Loss

o Peripheral neuropathy

• Loss of sensation involves all sensory modalities. Loss is most severe distally (feet and hands); response improves as stimulus is moved proximally

• Causes: Metabolic disease, nutritional deficiency

o Individual nerves or roots

• Decrease or loss of all sensory modalities. Area of sensory loss corresponds to distribution of the involved nerve

• Cause: Trauma, vascular occlusion

o Spinal cord hemisection

• Loss of pain and temperature on contralateral side, starting one to two segments below the level of the lesion.

• Loss of vibration and position discrimination on the ipsilateral side, below the level of the lesion.

• Causes: Meningioma, neurofibroma, cervical spondylosis, MS.


Common Patterns of Sensory Loss

o Thalamus

• Loss of all sensory modalities on the face, arm and leg on the

side contralateral to the lesion

• Cause: Vascular occlusion

o Cortex

• Since pain, vibration and crude touch are mediated by the

thalamus, there is little loss of this sensory function with a cortex

lesion.

• Loss of discrimination occurs on the contralateral side with loss

of recognition of shape, weight and finger finding.

• Cause: Cerebral cortex, parietal lobe lesion.


Patterns of Sensory Loss

Peripheral neuropathy

Individual nerves or roots

Spinal Cord Hemisection

spinal cord transection

(Jarvis 2016, p.686-687)


Patterns of Sensory loss

Thalamus

Cortex

(Jarvis 2016, p.686-687)


Reflexes

o Reflexes• Involuntary basic defence mechanisms of nervous

system

• Permit quick reaction to potentially harmful situations

• Help body maintain balance & appropriate muscle tone

o Four types• Deep tendon (stretch) reflex

• Superficial

• Visceral (organic)

• Pathological (abnormal)


Deep Tendon (Stretch) Reflex

o Measurement of DTR reveals

• intactness of reflex arc at specific spinal levels

• normal override on the reflex of higher cortical levels

o The deep tendon reflex (DTR) consists of:

• Tapping the tendon stretches the muscle spindles which activates the sensory afferent nerve

• The sensory afferent fibres carry the message from the receptor, through the dorsal (posterior) root, into the spinal cord

• They synapse in the cord with the motor neuron in the anterior horn

• Motor efferent fibres leave via the ventral (anterior) root and travel to the muscle, effecting a reflex response via the neuromuscular junction


Tendon Arc

(Jarvis 2016, p.637)


Rating Deep Tendon Reflexes

o The rating of reflexes is a subjective scale and must be considered in the context of the entire neurological examination of the client. Always compare bilaterally.

Rating Definition

4+ Very brisk, hyperactive with clonus,

indicative of disease (Hyper-reflexia)

3+ Brisker than average, may indicate

disease, probably normal

2+ Average, normal, NAD

1+ Diminished, low normal, or occurs only

with reinforcement (Hypo-reflexia)

0 No Response (areflexia)

(adapted from: Jarvis 2016, p.655)


Biceps Reflex (C5-C6)

(Jarvis 2016, p.656)

• The biceps reflex is

performed indirectly by

striking your own thumb

which is placed over the

biceps tendon.

• Normal = Forearm flexion

• If it is difficult to illicit the

reflex use the upper limb

reinforcement technique.

• Patient looks away

and clenches teeth.


Triceps Reflex (C7-C8)

(Jarvis 2016, p.657)

• Be careful when positioning

the arm in people who have

shoulder/rotator cuff

injuries.

• Normal = forearm extension


Patellar Reflex (L2-L4) Patellar reflex with

reinforcement

(Jarvis 2012)

• For reinforcement technique have the

client grasp their own forearms and

gently pull

• Normal = lower leg extension


Achilles Reflex (L5-S2)

(Jarvis 2016, p.659)

• Passive dorsiflexion of the

foot, whilst the leg is relaxed

is required.

• Normal = plantar flexion


Plantar Reflex (L4-S2)

(Jarvis 2016, p.660)

Negative Babinski Positive Babinski


Plantar Reflex (L4-S2)

o Normal response

• plantar flexion of all toes

• inversion & flexion of forefoot

o Abnormal

• dorsiflexion of big toe and fanning of all toes

– positive Babinski sign (UMN disease)

– Extend your neurological examination of the UMN’s


Resources

Jarvis, C, 2016, Physical Examination & Health

Assessment, 7th edn, Saunders, Sydney

Tortora GJ & Derrickson B, 2014, Principles of Anatomy

& Physiology, 14th edn, John Wiley & Sons, USA

Magee, D, 2008, Orthopaedic Physical Assessment,

Saunders Elsevier, Missouri.


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Documents

BIOE221 SN10 NeurologicalPNS · Dermatomes o A dermatome is a circumscribed skin area that is supplied mainly from one spinal cord segment through a ... (Magee 2008, p.155) (Magee