Spinal cord function and dysfunction

Question 1

What are the majority of tracts in the spinal cord

Answer 1

Ascending

Question 2

Why do the symptoms of spinal cord lesions depend on

Answer 2

The extent of the lesion
Where in the spinal cord the lesion takes place- both level and where about in there grey or white mater itself (as tracts occupy different lesions within the cord)

Question 3

How many spinal segments are there and how many pairs of spinal nerves are there

Answer 3

31 spinal segments

31 pairs of spinal nerves
8 Cervical
12 Thoracic
5 Lumbar
5 Sacral
1 Coccygeal

30 vertebrae

Question 4

How do nerves leave the vertebral column

Answer 4

Nerves leave the vertebral column through intervertebral foramina

Question 5

Is the diameter of the spinal cord constant

Answer 5

Cervical enlargement (C4-T1) – has extra motor neurons that go to the muscles of the upper limb
Lumbosacral enlargement (L2-S3) – has extra motor neurons that go to the muscles of the lower limb 

Therefore we see increases in diameter (enlargements) in these regions of the spinal cord

Question 6

Describe the discrepancy between spinal cord levels and vertebral levels

Answer 6

Spinal cord is a lot shorter than the vertebral column
Below the termination of the cord (L1/L2), the lumbar and sacral nerve roots descend as the cauda equina.
C1-C7- spinal nerves leave above their vertebrae
C8-Co- leave below their corresponding vertebrae
BUT C8 leaves below C7- only 7 cervical vertebrae

Describe injuries on two levels:
Vertebral level- where the injury actually took place
Spinal level- which spinal nerve is the last functioning one

Question 7

What is a spinal cord segment

Answer 7

A pair of spinal nerves leaves each segment of the spinal cord.
Essentially the butterfly shape of the spinal cord

Question 8

Describe the meningeal coverings of the spinal cord

Answer 8

Dura mater- continuous with the inner sheet of dura in the cranium, forms the dural sac, ends at S2
Arachnoid mater- ballooned up against the dura
Pia mater- adheres tightly to the inner surface of the spinal cord

Question 9

Describe the spaces formed in the spinal cord as a result of the meningeal coverings

Answer 9

Epidural space- true space between the dura and the vertebral periosteum, filled with fat and venous plexus- doesn’t exist in the brain

Subaracnhoid space- filled with CSF, continuous with the subarachnoid space of the cranium

Question 10

What are the denticulate ligaments

Answer 10

The pia mater has lateral projections called dentate ligaments which extend to the dura and help to stabilize the spinal cord
Lateral denticulate ligaments help to separate the anterior and posterior roots

Question 11

Describe the difference between the anterior and posterior roots

Answer 11

Anterior- carries motor innervation, exits spinal cord through anterolateral sulcus

Posterior- carries sensory information, cell bodies are in the spinal ganglion, enters the spinal cord in the posterolateral sulcus

Question 12

What is the spinal ganglion (dorsal root ganglion)

Answer 12

The pia mater has lateral projections called dentate ligaments which extend to the dura and help to stabilize the spinal cord

Question 13

What is the filum terminale

Answer 13

The lower end of the spinal cord is anchored to the coccygeal vertebrae by a pial thread called the filum terminale
Pia mater ends at level of spinal cord- but extends downwards to attach to the coccyx as the film terminal

Question 14

What is the lumbar cistern

Answer 14

The subarachnoid space below the end of the spinal cord is called the lumbar cistern. It contains the lumbar & sacral spinal roots (cauda equina)

Question 15

How doe the spinal nerves attach to the spinal cord

Answer 15

They attach to the spinal cord via dorsal and ventral roots which contain primary afferent and efferent neurons respectively (afferent neurons carry information to the central nervous system (CNS); efferent neurons carry impulses away from the CNS). Dorsal and ventral roots join to form the spinal nerve proper near to the intervertebral foramen where spinal nerves exit the vertebral canal. Here, small enlagements can also be seen on the dorsal roots. These are the dorsal root ganglia containing the cell bodies of the primary afferent neurons.

Question 16

Describe epidural nerve block

Answer 16

Anesthetic inserted into the epidural space
The anesthetic medicine is injected into the catheter to numb the body above and below the point of injection as needed.
Used when you know how long the surgery will take- i.e routine procedures and caesarians during childbirth

Question 17

Describe spinal nerve block

Answer 17

But the anesthetic medicine is injected using a much smaller needle, directly into the cerebrospinal fluid that surrounds the spinal cord (lumbar cistern- important to be below spinal cord- as nerve roots are floppy here- they won’t be damaged when you insert the needle- but move fixed in the spinal cord and so will be damaged
Spinal anesthesia numbs the body below and sometimes above the site of the injection.

Anaesthetic will circulate in CSF- so don’t need to know duration

Question 18

Define the term dermatome

Answer 18

Area of skin innervated by one spinal nerve or one spinal segment

Question 19

Define the term myotome

Answer 19

Muscles innervated by one single spinal nerve or spinal segment

Question 20

Summarise the grey mater of the spinal cord

Answer 20

Cells in the central grey matter can be divided into a series of layers in the dorsal horn and as a series of columns in the ventral horn (Fig. 4.3). These layers and columns are known as Rexed’s laminae (numbered I–X) and are based on groupings of similarly shaped cell bodies:

Question 21

Describe the dorsal (posterior) horn of the spinal cord

Answer 21

•
The dorsal horn layers are involved in sensory pathways and are the target sites for some sensory afferent nerves, particularly for pain, temperature and crude touch.

Question 22

Describe the ventral (anterior) horn of the spinal cord

Answer 22

The ventral columns are made up of pools of motor neurons innervating skeletal muscle. Medial motor columns supply proximal muscles and lateral motor columns supply distal muscles.

So medial- axial
Lateral- limb

Question 23

How do the dorsal and ventral roots attach to the grey mater of the spinal cord

Answer 23

Via many rootlets

Question 24

Describe the anterior and posterior rami

Answer 24

Anterior rami- sensory and motor to the front of the body
Posteiror rami- sensory and motor to the back

Formed after the formation of the spinal nerve and thus contain mixed motor and sensory information- different to that of the dorsal and ventral roots which contain either sensory or motor information exclusively

Question 25

Summarise the structure of the spinal cord

Answer 25

The spinal cord consists of a core of grey matter surrounded by white matter The dorsal horns receive sensory information from the body via spinal nerves and dorsal roots.

This information is used in spinal reflexes or projected to the brain for further processing

The ventral horns contain motoneurones whose axons control the muscles of the body via the ventral roots and spinal nerves

The white matter of the spinal cord contains short pathways which interconnect adjacent segments of the spinal cord, and longer tracts which convey information to and from the brain

Question 26

Describe the intermediate horns

Answer 26

In the thoracic and upper lumbar region the intermediate horns contain sympathatic preganglionic motoneurones whose axons control visceral function via the ventral roots and spinal nerves
T1-L2 normally

Question 27

Define the term nerve

Answer 27

Nerve: mixed bundle of sensory and motor neurones originating from the cord

Question 28

Define the term nerve root

Answer 28

Nerve root: dorsal root contains DRG for sensory neurone cell bodies, and carries sensory neurones into the cord, whereas ventral root carries motor neurones out of the cord - formed from rootlets emerging from the anterior (ventral) roots of the grey matter

Question 29

Define the term rams

Answer 29

Ramus: upon exiting spine, the mixed spinal nerve branches to an anterior and posterior ramus. The anterior ramus supplies the front and sides of the body, while the posterior ramus supplies the back.

Question 30

What are superior and inferior known as in the CNS

Answer 30

Superior- rostral (towards the beak)

Inferior- caudal (towards the tail)

Question 31

What is the anterior median fissure

Answer 31

Divides the anterior surface of the spinal cord in two halves

Question 32

What is the posterior median sulcus

Answer 32

divides the posterior surface of the spinal cord in two halves

Question 33

Describe where the sensory fibres for touch and proprioception enter the grey mater

Answer 33

Sensory neurones will enter the dorsal horn and then travel in the dorsal columns without synapsing in the dorsal horn

Question 34

Describe where the sensory fibres for pain and temperature enter the grey mater

Answer 34

Fibres enter the dorsal horn, may travel up 1-2 spinal cord levels in the Lissaeuer tract, then synapse in the nucleus proprius. Fibres then cross the midline in the anterior commissure and travel in the spinothalmic tract

Question 35

Describe where motor fibres leave the spinal cord

Answer 35

a-motor neurones are located in the ventral horn.
They exit the spinal cord and travel to their target muscles.
interneuron circuits in the anterior horn filter descending motor information and are part of localised reflex circuits

Question 36

Summarise the main ascending and descending tracts

Answer 36

Fasciculus: posteromedial - two tracts at the posterior column of the spinal cord, carrying fine touch, vibration and proprioception information
F. Gracilis: lower limb - L for LEG
F. Cuneatus: upper limb
Spinocerebellar: posterolateral - proprioception from limbs to cerebellum
Lateral corticospinal: lateral - motor to ipsilateral anterior horn - fibres cross- limb muscles- 85% of corticospinal fibres
Spinothalamic: anterolateral - pain and temp for contralateral side
Anterior corticospinal: anterior - motor to ipsi- and contralateral anterior horn - to axial muscles- fibres don’t cross

Question 37

Describe the white mater of the spinal cord

Answer 37

The white matter of the spinal cord consists of ascending and descending nerve fibres and completely surrounds the grey matter. As a general rule, the ascending sensory tracts run at the periphery and descending motor tracts occupy a more central position

Question 38

Where do sensory inputs from the skin terminate

Answer 38

Sensory inputs from the skin terminate in laminae I–IV, with some fibres travelling to the segments above and below in Lissauer’s tract.

Question 39

In the ventral horn of the grey matter, where are the cell bodies for flexors and extensors found

Answer 39

Flexors more superiorly

Question 40

What is the corticospinal tract

Answer 40

The corticospinal tract (sometimes called the pyramidal tract) is pimarily concerned with the control of skeletal muscle activity, particularly skilled voluntary movements in the distal parts of the limbs.
Main voluntary movement pathway

Question 41

Where do the motor fibres from the corticospinal tract originate from

Answer 41

Two-thirds of pyramidal tract neurons originate from cell bodies in the motor cortex (Brodmann’s areas 4 and 6; see Ch. 6). In the primary motor cortex, Betz cells give rise to the largest diameter corticospinal axons. The remaining third arise from the sensory cortices in the parietal lobes. Axons pass through the posterior third of internal capsule to the base of the cerebral peduncles. From here, the fibres descend through the pons to form a triangular fibre tract on the ventral surface of the medulla (hence the term pyramidal tract). The tract mostly decussates at the junction between medulla and spinal cord, after which they continue on the side contralateral to their origin in the motor cortex.

Question 42

What are the two branches of the corticospinal tract

Answer 42

•
75–90% of fibres decussate to form the lateral corticospinal tract. This tract controls the precision movements of the limbs (innervating lateral motor neuron pools).
•
10–25% of pyramidal fibres remain uncrossed (ispilateral) forming the ventral corticospinal tract. They do, however, decussate near to their termination. This tract controls the less precise movements of the trunk (innervating medial motor neuron pools).

Question 43

Describe the motor fibres that innervate the head

Answer 43

The fibres influencing motor neurons that innervate muscles in the head (e.g. extraocular muscles, tongue muscles and facial muscles, the bulbar muscles) run in the corticobulbar tracts to the appropriate cranial nerve nuclei. The somatotopic arrangement of the descending motor fibres from the cortex includes the head in the cerebral peduncles, but not at the level of decussation in the medulla.

Question 44

How do the motor fibres succeed in carrying signals for highly skilled voluntary movements

Answer 44

The motor fibres carry signals for highly skilled voluntary movements. To achieve this:
•
The tract needs to be highly somatotopic (see Ch. 6)
•
The fibres must have few collaterals so that excitation from one fibre is communicated to the minimum number of spinal motor neurons (this allows a great deal of control over the execution of movement).

Question 45

What other fibres are found in the corticospinal tract

Answer 45

As well as motor axons, there are fibres that regulate spinal reflexes in the tract and feedback to the dorsal horn sensory circuits from the sensory cortex.

Question 46

Why may the corticospinal tract be more complex than we know

Answer 46

In some individuals, one side of the brain controls the opposite side of the body and both sides of the trunk
in others, two sides of the brain are required to go to one side of the trunk.

Question 47

How many neurones are found between the peripheral receptor and the cerebral cortex

Answer 47

3

Question 48

Describe the 3 neurones involved in the sensory pathways

Answer 48

First-order neurons (or primary afferent neurons) enter the spinal cord via the dorsal roots of spinal nerves (their cell body lies in the dorsal root ganglion). They make synaptic contact with second order neurons either in the spinal cord grey matter or the medulla.
•
The cell bodies of second-order neurons lie in the cord or medulla. Their axons decussate (cross to the contralteral side of the CNS) and ascend to the thalamus where they synapse with third-order neurons.
Secondary neurones are always on the opposite side to the primary neurones
•
Third-order neuron cell bodies lie in thalamus. Their axons project to the somatosensory cortex in the parietal lobe.

Question 49

How are the sensory tracts arranged

Answer 49

Both sensory tracts are arranged segmentally (i.e. fibres from the same level run upwards together in the tract). At the top of the dorsal columns, the segments are arranged in a coherent pattern from medial (sacral) to lateral (cervical), maintaining the body pattern from which they arise.

Question 50

What are the dorsal column pathways

Answer 50

There are two tracts located within the dorsal columns; the fasciculus gracilis (medially) and the fasciculus cuneatus (laterally). One of the functions of the dorsal columns is to rearrange the dermatomal input of the primary sensory fibres into the map of the body surface seen in the primary sensory cortex (the sensory homunculus). Here, the body surface is seen as grossly distorted and is based on the number of receptors originating from any given structure. As such, most of the cortical cells respond to sensory exploratory structures such as the hands, feet and lips, all of which have high numbers of sensory receptors.

Question 51

What are the functions of the dorsal column pathways

Answer 51

•
Segregates information into modality-specific pathways for touch, hair movement, pressure, vibration and joint rotation- essentially, Discriminative touch, vibration, proprioception
•
Contains feedback mechanisms to gate the amount of incoming information to the cortex.

Question 52

Where do the functions of the dorsal column pathways occur

Answer 52

These functions are carried out in the areas where the pathway is interrupted by synapses, which allow for reorganization, segregation and suppression of the ascending sensory signals.

Question 53

Describe the passage of the dorsal columns to the medulla

Answer 53

Large sensory axons (Aα) enter the spinal cord and ascend ipsilaterally. The first order neuronal cell bodies lie in the dorsal root ganglia. They synapse with the dorsal column nuclei (gracile and cuneate) of the medulla in the pattern shown below:
•
Sensory input from the leg and lower trunk travels to the gracile nucleus
•
Sensory input from the arm, upper trunk and neck to the cuneate nucleus
•
Sensory input from the face goes via the trigeminal nerve (cranial nerve V) to the trigeminal nucleus.

Question 54

What happens to the dorsal column pathways after they have synapsed in the medulla

Answer 54

Axons from the cells in the gracile and cuneate nuclei then travel towards the ventral medulla where they decussate and continue toward the thalamus via the medial lemniscus. At the point of the decussation, all somatic sensory systems arising from one side of the body will be processed by the opposite (i.e. contralateral) side of the brain. The next synapse is in the contralateral ventroposterolateral nucleus of the thalamus (or VPL) or the contralateral ventroposteromedial nucleus (VPM) for trigeminal inputs (which have travelled in a separate trigeminothalamic tract).

Question 55

What happens to the dorsal column pathways after they have synapsed in the VPL of the thalamus

Answer 55

The homuncular organization which began in the dorsal columns and trigeminal nuclei is amplified in the thalamus and the sensory cortex. The neurons from the VPL and VPM nuclei project to the cortex (the primary somatosensory cortex, S1) via the thalamocortical radiations- through the internal capsule

Question 56

Does the information carried in the dorsal column resemble that in the somatosensory cortex

Answer 56

Information travelling along the dorsal column does not arrive at S1 in the same form it has when it enters the spinal cord. Information changes occur at both synapses (in the medulla and thalamus). For instance, lateral inhibition occurs between adjacent sets of inputs in the dorsal column pathway, allowing the distinction between background and ‘true’ sensory information to be increased and processed accordingly.

Question 57

Describe the information carried in the spinothalamic tract

Answer 57

In addition to pain, the spinothalamic tract also carries crude touch and thermal information. Pain information is also carried in the spinoreticular and spinomesencephalic tracts.

Question 58

Distinguish between the different types of pain

Answer 58

Noxious and thermal information is carried into the dorsal horn by fast myelinated Aδ fibres (conveying sharp, stabbing pain) and slower unmyelinated C fibres (conveying dull, nagging pain as well as thermal information).

Question 59

What happens to the sensory neurones once they reach the spinal cord in the spinothalamic tract

Answer 59

Aδ fibres terminate in laminae I and V. The axons from these cells immediately cross over to the opposite side of the cord (decussate) through the ventral white commissure and ascend in the anterolateral white matter, forming the spinothalamic tract (anterolateral system). Note this immediate decussation is different from that of the dorsal column pathway, as it occurs in the spinal cord as opposed to the medulla.

Question 60

How is the spinothalamic pathway similar to the dorsal column pathway

Answer 60

The spinothalamic tract is, however, similar to the dorsal column pathway in that there are three orders of neurons; first-order neurons in dorsal root ganglia, second-order neurons in dorsal grey matter and third-order neurons in the thalamus.

Question 61

Describe the passage of the C fibres

Answer 61

C fibres influence the firing of the spinothalamic dorsal horn cells via interneurons, because they terminate in a different layer of the cord-lamina II. This provides further synaptic steps in the pain pathway, which may comprise targets for modulation of pain signal transmission by higher centres

Question 62

Describe the passage of the neurones in the spinothalamiic tract after the spinal cord

Answer 62

the spinothalamic fibres join the medial lemniscus in the medulla and project to the thalamus. The thalamic termination of the tract is in the ventroposterior nuclei and also in the intralaminar nuclei, from which there is a relay to the cortex.

Question 63

Where do noxious inputs also project to

Answer 63

Noxious input also projects to a variety of brainstem structures, some of which are implicated in generating sensations of agonizing pain (spinomesencephalic) whereas others are involved in arousal mechanisms (spinoreticular).

Question 64

Describe the reflex pathway in response to stretching (for example tapping there patellar tendon/ligament)

Answer 64

Ia fibre from muscle spindle senses stretching of the muscle
Ia fibre synapses directly with a-motor neurones in the anterior horn
A-motor neurones to the extensor muscle are activated

Ia fibre also synapses with inhibitory interneuron
Inhibitory interneuron inhibits the a-motor neurones of the antagonist muscle

This is the knee jerk

Question 65

Describe the reflex pathway in response to noxious stimuli e.g heat or chemical stimuli

Answer 65

A-delta and C fibres in the skin detect noxious stimuli.
A-delta and C fibres synapse with inhibitory interneurons
A-motor neurones to the extensor muscles are inhibited

A-delta and C fibres also synapse with a-motor neurones for the flexor muscle
A-motore neurones to the flexor muscles are excited, and flexors contract, resulting in withdrawal from the noxious stimulus

Question 66

Why do we test reflexes clinically

Answer 66

Useful to test neurological problems
Knee jerk reflexes- tell you about the integrity of sensory and motor pathways- and wha’s happening in the brain- as reflexes change when changes in the brain occur:
larger in strokes
smaller with a peripheral nerve lesion

Question 67

Why are reflexes more complicated than described

Answer 67

When moving away from noxious stimuli- need to activate muscles in core and opposite leg to prevent you from falling over

Question 68

How are reflex actions permitted

Answer 68

The tracts carry information between different levels of the spinal cord (thereby permitting reflex actions), and also to and from the supraspinal structures.

Question 69

Describe the intermediolateral column

Answer 69

•
In between the dorsal and ventral horns lies the interomediolateral column where the cell bodies of preganglionic sympathetic neurons are found.
T1-L2

Question 70

Where are the pre-ganglionic visceromotor parasympathetic neurones found

Answer 70

Lateral horn of the grey matter

S2-S4

Question 71

What are the autonomic effects on the bladder, liver and rectum

Answer 71

SNS:
Bladder- relaxes bladder
Rectum- contracts rectum
Liver- stimulates glucose release

PSNS:
Bladder- Contracts bladder
Rectum- relaxes rectum
Liver- stimulates gallbladder

Question 72

Describe the range of things that can damage the spinal cord

Answer 72

Metastatic disease
Traumatic injury
Many things

Question 73

Which factors affect the severity of the spinal lesion

Answer 73

Loss of neural tissue
Vertical level
Transverse plane

Question 74

Describe the loss of neural tissue

Answer 74

Usually small if due to trauma
Can be more extensive e.g. metastases, degenerative disease or demyelinating
MRI of degenerating spinal cord

Question 75

Describe the impact of vertical level on the extent of the spinal cord lesion

Answer 75

Higher the lesion, greater the disability
Obviously, a fracture to the neck is more serious than that of the back
Can result in paralysis
To repair:
repair fracture
or reconnect the disconnected fibres

Question 76

Describe the effect of the transverse plane on the event of the spinal cord lesion

Answer 76

Transverse plane: most lesions are NOT complete - so anterior and posterior lesions will have different effects - anterior cord more likely to be sensory, posterior cord motor/pain & temp

complete or partial section; damage to white matter is usually more important than damage to grey matter because of which ascending and/or descending tracts are affected

Question 77

Describe the statistics associated with spinal injuries

Answer 77

Spinal cord injury paralyses over 6 people every day
NHS Specialised Spinal Cord Injury Services Annual Statement - in 2017/18, 2429 new patients were referred to the eight specialist centres in England.
This adds to the 50,000 living here that are already paralysed.
Most common causes of spinal cord injury is a broken neck or back as a result of road traffic accidents, accidents during sports or recreation or falls (in older people).
Currently no cure – yet!

Question 78

Describe the consequences of lesions to the dorsal columns

Answer 78

Sensory ataxia- due to loss of proprioception

Question 79

describe spinothalmic tract spinal lesions (syringyomyelia)

Answer 79

Enlargement of the central canal (the space is called a syrinx)
This selectively affects the spinothalamic fibres that are crossing at the level of the lesion and it does not affect fibres that have already crossed
So if the enlargement of the central canal is in the region of the cervical enlargement, you could get loss of pain/temperature sensation in the arms but not the legs (because those fibres would already have crossed and would be ascending in the spinothalamic tract away from the central canal)

Question 80

What is the difference between upper and lower motor neurones

Answer 80

An UMN that runs from the cortex to the ventral horn of the spinal cord
•
A LMN that runs from the ventral horn to the skeletal muscle.

Question 81

describe the consequences of upper motor neurone lesions

Answer 81

Voluntary paresis (weakness) is caused by loss of corticospinal input (i.e. a loss of UMN input). The symptoms and signs are:
•
Weakness involving extensors of the upper limb and flexors of the lower limb
•
Spasticity or abnormal distribution in muscle tone which affects flexors more than extensors (this may be caused by disruption of extrapyramidal systems)
•
Stronger deep reflexes, e.g. knee jerk (hyperreflexia)
•
Loss of superficial reflexes (e.g. abdominal, cremasteric)
•
Positive Babinski’s sign – extensor plantar response to stroking the lateral part of the sole from heel to toe
•
Clonus – elicited by rapidly dorsiflexing the foot (≤ 3 rhythmic downward beats of the foot are normal).

Question 82

Where are the effects of UMN lesion seen

Answer 82

The effects of an UMN lesion are typically seen on the side of the body contralateral to the lesion, because of the decussation of the corticospinal tract in the pyramids of the medulla (the left motor cortex, because of the decussation of fibres, controls the right side of the body). If there is localized damage to the motor cortex or pyramidal tract, all the input to an area will be affected due to homuncular and somatotopic organization.

Question 83

Describe the consequences of LMN lesion

Answer 83

Damage to the spinal motor neurons (or the LMNs), either in the cord or along their pathway to the site of innervation of the muscle, produces a different set of symptoms and signs, referred to as a LMN lesion:
•
Weakness caused by loss of nervous innervation (flaccid paralysis)
•
Atrophy as a result of disuse (this is a late sign)
•
Fasciculations (wriggling movements of the muscle) caused by increased sensitivity at receptor level to any acetylcholine that is released from intact terminals
•
Absent reflexes caused by loss of reflex output
•
Plantars remain flexor

Question 84

What are the two stages of injury to the lateral corticospinal tract

Answer 84

SPINAL SHOCK – you get loss of reflexes below the level of the lesion leading to flaccid paralysis. The limbs become floppy and there is little muscle tone
RETURN OF REFLEXES – you get hyperreflexia and spasticity. The patient experiences spontaneous muscle contraction and there is very high muscle tone – rigid paralysis - due to excitability of the interneurone connecting the sensory and motor neurones

Question 85

Summarise Brown-Sequard syndrome

Answer 85

With unilateral lesions the relationship of the deficit to the lesion depends on where the tract decussates
7. If you have a unilateral lesion of the lateral corticospinal tract in the mid-thoracic region, where will the deficit be?
Ipsilateral – on the same side as the lesion because the fibres decussate at the pyramidal decussation in the medulla

Question 86

Describe the posterolateral fasciculus (Liesauer tract)

Answer 86

Sensory fibres carrying pain and temperature will ascend or descend several spinal cord levels before synapsing in the posterior horn.

Question 87

Describe the substantia gelatinosa

Answer 87

Lamina II of the grey matter: first modulation for pain and temperature

Question 88

Summarise the recovery from spinal cord lesions

Answer 88

Severed CNS tracts do not regenerate but there may be some functional improvement after resolution of local damage if tracts are only compressed