Motor Examination Flashcards
What do you look for on general inspection during the motor exam
Posture/position
Deformities
Muscle Wasting
Spontaneous Fasciculations
Bilateral Ptosis
Facial Asymmetry
Dyskinesia (Chorea, Hemiballismus, Athetosis, Myoclonic Jerks, Tardive Dyskinesia)
Neuro-cutaneous lesions
Scars
What are spontaneous fasciculations
Visible irregular twitching of resting muscles caused by single motor units firing spontaneously
What are some causes of spontaneous fasciculations
Lower Motor Neuron Lesion
Explain how a lower motor neuron lesion causes spontaneous fasciculations
Fasciculations are as a result of denervation hypersensitivity (which occurs in severe lmn lesions)
Denervation Hypersensitivity:
When α-motor neurons are damaged, they can fire spontaneous action potentials, causing contractions in the fibres of the motor unit.
Fasciculations are only considered pathological when existing in the presence of which other observable features?
Wasting and weakness
What is a lower motor neuron?
A lower motor neuron/ alpha motor neuron is a multipolar neuron that connects UMN directly or via interneurons to the skeletal muscle that they innervate
Where does the cell body of an LMN lie
In the anterior/ventral horn of the spinal cord (CNS)
What are the components of a motor unit
LMN(anterior horn cell, axon, myelin)
Neuromuscular junction, and Muscle fibers.
True or false
One motor neuron will innervate several muscle fibers, but a single muscle fiber is only innervated by one motor neuron
True
What are the two main types of LMN
alpha motor neuron
and
gamma motor neuron
Within the spinal cord, where specifically do the cell bodies of Alpha motor neurons originate?
Lamina VIII and IX of the ventral/anterior horn
In terms of the muscles groups that alpha neurons innervate, how are the cell bodies arranged int the ventral horn of the spinal cord?
Neurons that innervate distal muscle groups are located laterally to those that innervate axial groups
Neurons that innervate extensors are located anterior to those that innervate flexors
What is the main function of the alpha motor neurons
To perform contraction
What portion of the reflex arc do alpha motor neurons form ?
The efferent arm
PS. Alpha neurons receive input from UMN and sensory nerves that form the reflex arc
True or False
There can be coordinated muscle contraction if the alpha motor neurons are not functioning
False
What is the function of gamma motor neurons
Controls muscle tone and unconscious proprioception
maintains muscle sensitivity to stretch
True false
A LMN syndrome involves damage to both alpha and gamma neurons
False, only alpha neurons are damaged in LMN syndrome
True or False,
γ-motor neurons are solely under control from the UMNs.
true
True or False
the firing of γ-motor neurons is directly proportional to the tone of a muscle.
True
How can tone be increased?
If you increased the firing of the gamma motor neurons
This hypersensitivity in turn causes greater activation and recruitment of α-motor neurons via the reflex arc, creating a stiff muscle on passive movement.
Define a lower motor syndrome
A LMN syndrome is the term used by clinicians to describe the collection of signs and symptoms present when a patient damages α-motor neurons
Where can the damage occur in the LMN lesion
Anywhere along the Brainstem nuclei/origin in the ventral horn of the spinal cord to where it synapses on the muscle fibre
What are 5 LMN lesion signs
-Hyporeflexia/Areflexia
-Hypotonicity
-Fasciculations
-Muscle Weakness/Paralysis
-Muscle atrophy
How does LMN lesion cause hy oreflexia/areflexia
The alpha motor neurons form the efferent arm of the reflex arc, therefore if they are damaged there will be no reflex contraction of the muscle group stimulated by the reflex
How does LMN lesion cause hypotonia/atonia
Tone is a product of the contraction of extrafusal fibres in response to stretch. Therefore damage to the alpha motor neurons will result in decreased tone
What is Spinal Muscular Atrophy ?
This is an autosomal recessive disorder in which there is loss of nuclei in the ventral/anterior horn of the spinal cord. There also may be loss of motor neurons in the pons and medulla
Define dystonia
Dystonia is defined as sustained muscle contractions, leading to
twisting, repetitive movements and sometimes tremor
Define chorea
Chorea describes brief, jerky, random, low amplitude, purposeless movements
that may affect various body parts, commonly the arms.
Define athetosis
Athetosis is a slower, writhing movement, more similar to
dystonia than chorea.
Define ballism
Ballism refers to violent flinging movements sometimes affecting
only one side of the body (hemiballismus)
large-amplitude, arrhythmic, and more proximal (especially at the shoulder and hip)
Give two causes of dystonia
Neonatal birth injury (hypoxia, brain hemorrhage)
Drugs: antipsychotics, antiemetics
Hepatorenal Syndrome
Give two causes of chorea
ST VITUS DANCE
S- Sydenham’s chorea
T- trauma (bilateral subdural haematoma)
V- vascular (infarct)
I- increased RBC
T- Thyrotoxicosis
U- Ureamia
S- SLE
D- Drugs (Levodopa, carbamazepine, phenytoin)
A- APLA Syndrome
N- Neurodegenerative disease (Huntington’s)
C- Chorea Gravidarum
E- Exposure to toxins (CO, Mg)
Causes of athetosis
Basal Ganglia disease
Cerebral palsy
Huntington Syndrome
List two causes of ballismus
neurodegenerative, vascular, toxic metabolic, infectious or immunological process affecting the basal ganglia
What is a tremor
This is an involuntary oscillating movement about a joint or a group of joint resulting from alternating contracting and relaxation of the muscle groups
What is a physiological tremor?
This is a fine (low amplitude), fast (high frequency) postural tremor
What are some non neurological causes of physiological tremors?
Beta Agonists
Hyperthyroidism
Alcohol intoxication
Caffeine intake
Define the tremor seen in Parkinson’s disease
Parkinson’s disease causes a slow (3–7 Hz), coarse, ‘pill-rolling’
tremor, worse at rest but reduced with voluntary movement.
Describe an intention tremor
Intention tremor is absent at rest but maximal on movement
and on approaching the target
What is the most common cause of intention tremor
Cerebellar damage
In the Lower limb motor examination, what comes after general inspection?
Assessment of bulk in:
Quadriceps femoris (Rectus femoris, vastus medialis, vastus lateralis, vastus intermedius)
Hamstrings (biceps femoris, semimembranosus, semitendinosus)
Calf muscles (gastrocnemius, soleus)
Which nerve innervates the quadricep femoris muscles (vastus medialis, lateralis, intermedius, rectus femoris)
Femoral Nerve (L2,L3,L4)
Which nerve innervates the Hamstrings (Biceps Femoris, Semitendinosus, Semimembranosus)
Tibial part of the sciatic nerve (L5, S1, S2, S3)
Which nerve innervates the soleus and gastrocnemius?
Tibial Nerve (L4, L5, S1, S2, S3)
After assessing bulk in the lower motor examination, which step is next?
Assessing tone
How is tone assessed in a lower motor exam?
Hip flexion/extension adduction/abduction
Knee flexion/extension
Ankle plantarflexion/dorsiflexion
Hypotonicity indicates what lesion?
LMN lesion
What is an UMN
An upper motor neurone (UMN) is is a neurone whose cell body originates in the cerebral cortex or brainstem and terminates within the brainstem or spinal cord.
Corticobulbar tracts arise and synapse where?
They arise from the pre-central gyrus and synapse at the motor nuclei of cranial nerves
Corticspinal tracts arise and synapse where?
They arise from the pre-central gyrus and synapse at the nuclei in the ventral horn of the spinal cord
What is the neurotransmitter typically involved in the transmission from upper to lower motor neurones?
Glutamate
What lesion causes hypertonia?(resistance to passive movement)
UMN lesion
How does UMN lesion cause hypertonia
UMN modulate tonicity by descending inhibition. UMN regulate inhibitory interneurons and their action on gamma and alpha (LMN). Therefore, in the absence of UMN there is no inhibition to LMN effect and results in hypertonia
Does UMN lesion cause hyper or hypotonicity
Descending inhibition from the UMNs also regulates the extent to which the stretch reflex is elicited (by gamma and alpha LMNs). Therefore, loss of the UMN activity causes brisk reflexes.
Define hypertonia
This is resistance to passive movement, not dependent on velocity
Define spasticity
this is a sudden increase in resistance to sudden passive movement and is velocity dependent
ie (rapid passive movement of a limb, there will be a point where the muscle becomes suddenly resistant to further stretch
After tone is assessed in the Lower Motor examination, what is the next step?
Assessing power
What is the power muscle scale 0-5
0: No contractions
1: Flicker or trace of contraction
2: Active movement with gravity eliminated
3: Active movement against gravity but not resistance
4: Active movement against gravity but weaker than normal
5: Normal power
What is tone?
This is the resistance that the examiner feels when moving a joint passively
Define Rigidity
This is a sustained resistance throughout the range of
movement and is most easily detected when the limb is moved
slowly.
What is clonus?
This is a rhythmic series of contractions evoked by sudden stretch of the tendon and muscle
Clonus is caused by UMN or LMN lesion
UMN
How do UMN lesions cause clonus
Because of the decreased modulation of spinal reflexes in UMN syndrome, patients will often exhibit flexor and extensor spasms
What is myotonia
The inability or difficulty of muscle groups relaxing
Hip flexion is controlled by which muscle, nerve and nerve root
Iliopsoas
Femoral Nerve
L1,2,3
Hip extension is controlled by which muscle, nerve nerve root
Gluteal Maximus
Internal Gluteal Nerve
L5, S1, S2
Extension at the knee is controlled by which muscle, nerve, nerve root?
Quadriceps Femoris
Femoral Nerve
L2, 3, 4
Flexion at the knee is controlled by which muscle, nerve, nerve root?
Hamstrings
Sciatic nerve
L5, S1, S2
Define Huntington’s Disease
This is an autosomal dominant neurogenetive disorder that is incurable and progressive. It often presents at middle age with prodromal symptoms of : irritabilty, depression. incoordination.
CAused by atrophy and neuronal loss of striatum and cortex
