Neurological Examination : Reflexes Flashcards
What is a reflex ?
A predictable, involuntary motor or vegetative response to a standardised stimulus.
What is the standardised reflex pathway ?
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
What are the 3 types of reflexes ?
Proprioceptive reflex = muscle stretch reflex
Cutaneous reflex = superficial reflex
Primitive reflex
What are the characteristics of proprioceptive reflex ?
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
What are the characteristics of cutaneous reflex ?
Standardised tactile stimulus.
Response by muscle contraction.
Poly-synaptic reflexes.
What are the characteristics of primitive reflexes ?
Present in neonates resulting of an immature nervous system and extinguished when it becomes mature.
Can reappear due to lesion often caused degenerative disease.
What are the different proprioceptive reflexes and their nerves ?
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
What are the types of cutaneous reflex to test ?
On indication :
- abdominal skin reflex
- plantar reflex
What are the types of primitives reflexes to test ?
On indication.
- snout reflex
- palmomental reflex
- corneomandibular reflex
What is the specific reflex test ?
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
What is the general technique of reflex testing ?
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
How do you distract the patient ?
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
Biceps tendon reflex ?
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
Triceps tendon reflex ?
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
Brachioradialis relfex ?
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
Finger flexion / Hoffman’s reflex ?
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
Patellar reflex ?
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
Ankle jerk reflex ?
Seated : plantarflexion
- foot in slight dorsiflexion
- strike Achille tendon
Tibial nerve then sciatic nerve - S1
How to describe reflexes with the neurologist scale ?
-4 = absent
+4 = non extinguishing
How to describe réflexes with the muscle stretch reflex scale ?
0 = absent
1 = low
2 = normal (brief)
3 = high
4 = high with clonus
5 = very high with non extinguishing clonus
What is a clonus ?
An involuntary and rhythmic muscle contraction caused by a permanent lesion in descending motor neurons.
Indicative of central motor neurone lesion
How do you test abdominal skin reflex ?
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
How do you test the plantar reflex ?
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
How do you test the snout reflex ?
Gently tap the skin between patient nose and mouth with finger
- absence of response if normal
- reflex => brief purse lips reflexively
How do you test the palmomental reflex ?
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
What is the purpose of testing proprioceptive reflex ?
Test hypothesis
Asymmetry provide important info
- due to a unilateral central motor neuron abnormalities
What does having low reflex means ?
Signal impairment in the peripheral nervous system
What does not having reflexes mean ?
Lesion of peripheral nerve
Lesion of central part of reflex arc
Acute stage of spinal cord injury
Deep coma
What does having high reflex means ?
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.
What happen to the reflexes after a spinal cord injury ?
Soon after there’s hypotonia and areflexia. After a few days/hours it becomes hypertonic and hyperreflexia.
What is the clinical significance of cutaneous reflex ?
Asymmetry is always pathological.
Babinski’s sign means a pyramidal tract lesion.
Absent abdominal skin reflex.
What are the causes of an absent abdominal skin reflex ?
Pyramidal tract lesion
Severe obesity
Weak abdominal muscle
What causes primitive reflexes to appear ?
Cerebral pyramidal tract lesion.
Diffuse cerebral disorder such as : hydrocephalus, dementia syndrome, severe traumatic brain injury, metabolic problem.
