Neurological Examination : Reflexes

Question 1

What is a reflex ?

Answer 1

A predictable, involuntary motor or vegetative response to a standardised stimulus.

Question 2

What is the standardised reflex pathway ?

Answer 2

Receptor organ => muscle spindle, tactile receptor
- afférent pathway : afférent peripheral nerve to dorsal root
Input in a particular spinal cord segment then synaptic transfer.
- efferent pathway : ventral root to efferent part of peripheral nerve
Effect organ : muscle

Question 3

What are the 3 types of reflexes ?

Answer 3

Proprioceptive reflex = muscle stretch reflex
Cutaneous reflex = superficial reflex
Primitive reflex

Question 4

What are the characteristics of proprioceptive reflex ?

Answer 4

Receptor organs = muscle spindle
Activated by stretch due to a tap of reflex hammer, they have the same pathway.
Synaptic contact with the anterior horn cell
- influenced by muscle spindles signals and the corticospinal tract (inhibitory effect)
Always monosynaptic

Question 5

What are the characteristics of cutaneous reflex ?

Answer 5

Standardised tactile stimulus.
Response by muscle contraction.
Poly-synaptic reflexes.

Question 6

What are the characteristics of primitive reflexes ?

Answer 6

Present in neonates resulting of an immature nervous system and extinguished when it becomes mature.

Can reappear due to lesion often caused degenerative disease.

Question 7

What are the different proprioceptive reflexes and their nerves ?

Answer 7

Biceps tendon reflex :
- Musculocutaneous nerve - C5, C6
Triceps tendon reflex :
- Radial nerve - C7, C8
Brachio-radialis reflex :
- Radial nerve - C5, C6
Finger flexion reflex (Hoffmann’s reflex; on indication) :
- Median nerve - C7, C8, T1
Patellar reflex :
- Femoral nerve - L2, L3, L4
Ankle jerk reflex :
- Tibial nerve then sciatic nerve - S1

Question 8

What are the types of cutaneous reflex to test ?

Answer 8

On indication :
- abdominal skin reflex
- plantar reflex

Question 9

What are the types of primitives reflexes to test ?

Answer 9

On indication.
- snout reflex
- palmomental reflex
- corneomandibular reflex

Question 10

What is the specific reflex test ?

Answer 10

The ankle clonus test.
- support patient partially flexed knee
- bring foot into dorsi/plantar-flexion a few times
- foot in dorsiflexion
Watch out for rhythmic movement

Question 11

What is the general technique of reflex testing ?

Answer 11

Hold reflex hammer to strike with relaxed wrist
- with dominant hand, brief and strong hit
Repeat test several times with short intervals
Muscle must be relaxed
- distract the patient
Assess : movement/contraction, compare left/right

Question 12

How do you distract the patient ?

Answer 12

For arms reflex : make a fist with other arm

Jendrassik manoeuvre (patellar and ankle)
- interlock patient finger and ask them to try to pull them appart

Question 13

Biceps tendon reflex ?

Answer 13

Seated : flexions of forearm
- relaxed forearm on their lap
Press finger on biceps tendon in the cubital fold
Strike finger with hammer

Musculocutaneous nerve - C5-6

Question 14

Triceps tendon reflex ?

Answer 14

Seated : extension of the forearm
- slightly more than 90° flexion of the forearm
OR
- abducted shoulder, forearm hanging down

• hold patient wrist
• strike above the olecranon at the epicondyles

Radial nerve - C7-8

Question 15

Brachioradialis relfex ?

Answer 15

Seated : extension of the wrist
- relaxed forearm on their lap
- strike radial side of the forearm (with or without the finger)

Radial nerve - C5-6

Question 16

Finger flexion / Hoffman’s reflex ?

Answer 16

Flexion of thumb and index
- hook finger around patient middle finger
- let hand hang down
- flick flexed distal phalanx of middle finger

Median nerve - C7-8, T1

Question 17

Patellar reflex ?

Answer 17

Seated : extension of lower leg
- dangle lower leg over the edge of the table
- strike quadriceps tendon between patella and tibial tuberosity

Femoral nerve - L2-3-4

Question 18

Ankle jerk reflex ?

Answer 18

Seated : plantarflexion
- foot in slight dorsiflexion
- strike Achille tendon

Tibial nerve then sciatic nerve - S1

Question 19

How to describe reflexes with the neurologist scale ?

Answer 19

-4 = absent

+4 = non extinguishing

Question 20

How to describe réflexes with the muscle stretch reflex scale ?

Answer 20

0 = absent
1 = low
2 = normal (brief)
3 = high
4 = high with clonus
5 = very high with non extinguishing clonus

Question 21

What is a clonus ?

Answer 21

An involuntary and rhythmic muscle contraction caused by a permanent lesion in descending motor neurons.
Indicative of central motor neurone lesion

Question 22

How do you test abdominal skin reflex ?

Answer 22

Supine relaxed patient :
- stroke abdominal skin, lateral to medial with a cotton bud

Watch out for :
- movement of the navel due to reflexive tensing
- deviation form the navel toward the stimulus

Question 23

How do you test the plantar reflex ?

Answer 23

Supine patient :
- grasp ankle/foot
- stroke lateral surface of the loop of the foot with cotton bud over the ball of the foot in medial direction

Watch for :
- extension of big toe => Babinski’s reflex is pathological
- plantarflexion or no reaction normally

Question 24

How do you test the snout reflex ?

Answer 24

Gently tap the skin between patient nose and mouth with finger
- absence of response if normal
- reflex => brief purse lips reflexively

Question 25

How do you test the palmomental reflex ?

Answer 25

Stroke patient thenar eminence (under the thumb) with cotton bud firmly and briefly

Watch out for :
- homolateral contraction of the mentalis muscle in the chin
- if elicited more than 5 times => pathological

Question 26

What is the purpose of testing proprioceptive reflex ?

Answer 26

Test hypothesis
Asymmetry provide important info
- due to a unilateral central motor neuron abnormalities

Question 27

What does having low reflex means ?

Answer 27

Signal impairment in the peripheral nervous system

Question 28

What does not having reflexes mean ?

Answer 28

Lesion of peripheral nerve
Lesion of central part of reflex arc
Acute stage of spinal cord injury
Deep coma

Question 29

What does having high reflex means ?

Answer 29

Disorder of the central nervous system :
- corticospinal tract is supposed to have an inhibitory influence. If central influence decrease, the motor neurone will be more sensible to stimulation.

Question 30

What happen to the reflexes after a spinal cord injury ?

Answer 30

Soon after there’s hypotonia and areflexia. After a few days/hours it becomes hypertonic and hyperreflexia.

Question 31

What is the clinical significance of cutaneous reflex ?

Answer 31

Asymmetry is always pathological.
Babinski’s sign means a pyramidal tract lesion.
Absent abdominal skin reflex.

Question 32

What are the causes of an absent abdominal skin reflex ?

Answer 32

Pyramidal tract lesion
Severe obesity
Weak abdominal muscle

Question 33

What causes primitive reflexes to appear ?

Answer 33

Cerebral pyramidal tract lesion.
Diffuse cerebral disorder such as : hydrocephalus, dementia syndrome, severe traumatic brain injury, metabolic problem.