TCeMEPs

Question 1

Purpose of TCeMEPs

Answer 1

used to monitor the corticospinal descending pathway
– Voluntary movement of the limbs
– Voluntary movement of the trunk
– Posture and balance
▪ Sensory systems help to guide our movement

Question 2

MEP Pathway - Upper Motor Neuron

Answer 2

CEREBRAL CORTEX TO ANTERIOR HORN

Signal travels from the cortex through the internal capsule, and in the medulla, most of the lateral tract crosses over.

The anterior tract continues down the ipsilateral side and crosses over in the spinal cord at the level it synapses.

Question 3

MEP Pathway - Lower Motor Neuron

Answer 3

ANTERIOR HORN TO MUSCLE

Synapse occurs in the anterior horn of the spinal cord. The signal travels through the nerve to the neuromuscular junction where it connects up with the musculature.

Question 4

Upper MEP homonculus

Answer 4

represented laterally in cortex

Question 5

Upper MEP Blood Supply

Answer 5

Supplied by the Middle Cerebral Artery (MCA).
IC supplied by lenticulostriate
branches originating from MCA and the anterior choroidal arteries,
Brainstem branches of the vertebral and basilar arteries, spinal cord ASA, PSA and radicular arteries
Watershed zones = T1, T5, T8 - 9

Question 6

Lower MEP Homunculus

Answer 6

represented medially in cortex

Question 7

Lower MEP Blood Supply

Answer 7

Supplied by the Anterior Cerebral Artery (ACA) and Anterior Communicating Artery ( Acomm )

Question 8

Corticobulbar Motor Tract

Answer 8

Originating from Cortex
projects to the medulla and ends at cranial nerve nuclei controlling movements of the face and tongue

Question 9

Lateral Corticospinal Motor Tract

Answer 9

▪ Originating from Cortex
project to the spinal cord and control movements of the trunk and limbs, axons terminate in the gray matter of the spinal cord

Voluntary motor control of the body and limbs

Synapses in the anterior horn on the lower motor neuron

▪ Lateral – distal part of limbs (90% of connections)

Question 10

Anterior Corticospinal Motor Tract

Answer 10

▪ Originating from Cortex
project to the spinal cord and control movements of the trunk and limbs, axons terminate in the gray matter of the spinal cord

Voluntary motor control of the body and limbs

Crosses in the anterior horn,then synapses on the lower
motor neuron

▪ Anterior – upper legs and trunk (10% of connections, controls trunk)

Question 11

Corticorubrospinal Motor Tract

Answer 11

Originates in the red nucleus which receives information from the motor cortex and cerebellum, axons terminate on spinal cord and control arms and legs but not fingers

Question 12

Vestibulospinal Motor Tract originates in the…

Answer 12

vestibular nucleus

Question 13

Reticulospinal Motor Tract

Answer 13

originates in the reticular formation, terminates in the gray matter of the spinal cord, movement of the trunk and proximal limbs (head turning, autonomic functions)

Question 14

Tectospinal Motor Tract originates in…

Answer 14

the superior colliculus

Question 15

General Somatic Efferent (GSE) – located…

Answer 15

in the ventral horns of the
gray matter of the spinal cord,

– In addition to the spine it includes the tongue and the eye muscles (CN III, IV, VI, XII)

Question 16

General Somatic Efferent (GSE) - exit

Answer 16

via the ventral root carrying motor information to skeletal muscle via the neuromuscular junction

Question 17

alpha motor neurons target

Answer 17

extrafusal (generate tension) muscle fibers

Question 18

gamma motor neurons target

Answer 18

intrafusal (detect amount of tension) muscle fibers

Question 19

RE: General Somatic Efferent Pathways (Pyramidal Tracts)

Corticospinal Tract – carries

Answer 19

motor information from the brain down to the skeletal muscles to cause movement

Question 20

RE: General Somatic Efferent Pathways (Pyramidal Tracts)

Corticobulbar Tract – carries

Answer 20

motor information from the brain to the cranial nerve innervated muscles to cause movement

Question 21

Corticospinal tract upper motor neurons connect…

Answer 21

the brain to the neurons in the spinal cord
where they synapse in the anterior horn

Question 22

Corticospinal tract lower motor neurons connect…

Answer 22

the neurons where they synapse in the anterior
horn of the spinal cord with the neuromuscular junction

Question 23

Motor Cortex

Answer 23

30% of motor neurons originate in the primary motor cortex
* Precentral Gyrus
* Brodmann Area 4
* Homunculus
* Body map locations of neurons that correspond to muscle control

Question 24

Premotor/Supplementary Motor Areas

Answer 24

30% of motor neurons
Anterior to the precentral gyrus
* More complex and fine movement control
* Voluntary actions dependent on sensory feedback
* Visual, auditory, general somatic
* Movement planning

Question 25

Somatosensory Cortex

Answer 25

(40% of motor neurons) * Parietal lobe, cingulate gyrus

Question 26

Additional Motor Areas

Answer 26

▪ Frontal Eye Field – Anterior to premotor cortex – Voluntary movement of the eyes ▪ Broca’s Area – Left frontal lobe – Speech production – Corresponding region in the right

Question 27

Pyramidal Cells - layer V

Answer 27

– Pyramidal cells primary control for body movements ▪ Basal dendrites ▪ Apical dendrites that reaches toward the dorsal cortical border ▪ Receive synaptic connections from other connections in cortex ▪ Send their signals to other pyramidal cells, other cortical neurons, spinal cord, thalamus, brainstem

Question 28

Betz cells in Layer V

Answer 28

project far distances

Question 29

Internal Capsule

Answer 29

Cortical neurons project as the corona radiata through the posterior limb of the internal capsule down to the midbrain

Question 30

The Internal Capsule includes

Answer 30

Corticopontine tract Coticobulbar tract Corticospinal tract

Question 31

Midbrain & Pons (MEPs)

Answer 31

▪ Fibers of the pyramidal tracts travel through the cerebral peduncles ▪ Damage results in unrefined motor skills, imbalance and lack of proprioception

Question 32

Medulla (MEPs)

Answer 32

▪ The pyramidal tracts form two “ pyramids ” ▪ About 80 - 90% of the lateral tract crosses over here at the pyramidal decussation ▪ The anterior tract continues down the ipsilateral side

Question 33

Temporal Summation

Answer 33

potentials occur close to each other in time producing a cumulative effect

Question 34

Spatial Summation

Answer 34

potentials occur close to each other on the membrane from several synaptic inputs originating from separate locations can also exert a cumulative effect

Question 35

Stimulation Sites for MEPs (Cerebral Cortex)

Answer 35

▪ Most commonly used are C3 and C4 ▪ Alternative stimulation sites may include: – C1 – C2 – M3 – M4 – Cz

Question 36

Stimulation Sites for MEPs (Spinal Cord)

Answer 36

Epidural Electrodes

Question 37

Linked Quadripolar (LQP) Setup for TCeMEPs

Answer 37

* Measure nasion to inion to find CZ just like you normally would to find CZ * Measure 10% to the left and right for C1 and C2 * Measure 20% to the left and right * 1 cm anterior are M3 and M4 * 2 cm posterior are SSEP head leads C1 and M3 (left side) go into the black plugs (there are three, it doesn’t matter which two you use) C2 and M4 (right side) go into the red plugs These can hook up to any input on your TCS - 4 box, but recommend using 1 as this is what is programmed for our protocols.

Question 38

Stimulation Parameters for TCeMEPs - Intensity

Answer 38

– 0 - 1000 V – Intensity is increased until myogenic responses are generated in target muscles or the intensity reaches 600 V

Question 39

Stimulation Parameters for TCeMEPs - Duration

Answer 39

– 50 or 75 μs

Question 40

Stimulation Parameters for TCeMEPs - Train Count

Answer 40

– 1 - 9 pulses, preferable 5 - 7 for spine and 3 - 5 for craniotomies – Double train (most successful in patients who have pre - existing deficits or who experience changes intraoperatively – Osburn 2006)

Question 41

Stimulation Parameters for TCeMEPs - Rate

Answer 41

– If measured in frequency: 200 - 500 Hz – If measured as interstimulus interval (ISI): 1.1 - 4.5 ms is best

Question 42

So for motor potentials, we can utilize constant current or constant voltage, but more typically we use

Answer 42

constant voltage.

Question 43

The fastest you ever want to stimulate is

Answer 43

2 milliseconds, unless you are doing cranial nerve motor evoke potentials.

Question 44

he slowest that you'd want to stimulate is at

Answer 44

5 milliseconds interstimulus interval.

Question 45

Recording Sites for TCeMEPs -

Answer 45

can generally be any muscle of the body or face.

Question 46

RE: Muscle Innervation - Trapezius

Answer 46

Major Nerve: None Spinal Nerves: C2-4, Spinal Accessory

Question 47

RE: Muscle Innervation - Sternocleidomastoid

Answer 47

Major Nerve: None Spinal Nerves: C2-4

Question 48

RE: Muscle Innervation - Deltoid

Answer 48

Major Nerve: Axillary Spinal Nerves: C5-C6

Question 49

RE: Muscle Innervation - Biceps Brachii

Answer 49

Major Nerve: Musculocutaneous Spinal Nerves: C5-C6