4 - Spinal Cord

Pia mater

innermost

Arachnoid mater

outside pia mater

• Subarachnoid space – contains cerebrospinal fluid

Dura mater

outermost layer, study layer of connective tissue that has lots of sensory nerve endings

Cauda Equina

Area distal to L1 where the lumbar and sacral nerves roots run inferiorly within the spinal canal

• Considered PNS

• Turns from SC to cauda equina at L1

What type of injuries occurs when the spina is injured at L1/L2 or lower?

LMN injuries: flaccid paralysis, atrophy, hyporeflexia

Saddle anesthesia

Sensory impairment in perineal and inner thigh area

• Red flag for cauda equina syndrome

• Requires immediate referral

Grey matter

Composed of neuron cell bodies and dendrites

• Includes: dorsal, lateral, and ventral horns

Dorsal horn

Contains sensory (afferent) nerve fibers

Lateral horn

Contains cell bodies of autonomic neurons

• Only found in T1 – L2 and S2 – S4

Ventral horn

Contains cell bodies of motor neurons that innervate skeletal muscles

• Considered lower motor neurons

White matter

Contains both ascending and descending tracts

Ascending tracts

carry action potentials to the brain

Descending tracts

carry signals from the brain to the body

Dorsal Columns (medial lemniscus)

• Location: posterior white matter

• Function: Convey information regarding 2-point discrimination, vibration, conscious proprioception to primary sensory cortex

  • Information regarding the LE travels in the gracile fasciculus

  • Information regarding the UE travels in the cuneate fasciculus

  • Crosses in the medulla oblongata

What happens if the dorsal columns are injured?

• If unilateral lesion below the decussation → ipsilateral loss

• If superior to decussation → contralateral loss

Anterior spinothalamic tract

• Location: anterior white matter

• Function: Convey information regarding pressure, texture and light touch to somatosensory cortex

  • Ascends 1-2 levels before decussating

What occurs if the anterior spinothalamic tract is injured?

Contralateral loss of pressure and touch sensation

Lateral spinothalamic tract

• Location: Lateral white matter

• Function: Convey information regarding pain and temperature to somatosensory cortex

What occurs if the lateral spinothalamic tract is injured?

Contralateral loss of pain and temperature sensation

Spinocerebellar tract

• Location: Lateral white matter, anterior and posterior Input from muscle spindle and golgi tendon organ

• Function: Convey information regarding unconscious proprioception to cerebellum

What occurs if the spinocerebellar tract is injured?

Partial loss of unconscious proprioception, lack of coordinated movement

How is the spinocerebellar tract often injured?

Demyelinating diseases such as MS

Spino-olivary tract

ascends to the cerebellum and relays information from cutaneous and proprioceptive organs (tendons and muscles)

Spinoreticular tract

• Afferent pathway to the reticular formation that influences levels of consciousness

• Assists in immediate reaction to painful stimuli

Spinotectal tract

afferent pathway providing information for spinovisual reflexes and assists with movement of eyes towards a stimulus

Lateral corticospinal tract

• Location: Lateral white matter Originates in cerebral cortex

  • Becomes the lateral corticospinal tract when fibers decussate in the medulla at the pyramids

• Function: Convey information to cause voluntary movement

What occurs if the lateral corticospinal tract is injured?

Unilateral lesion of the spinal cord below decussation → Ipsilateral spastic paralysis

Anterior corticospinal tract

• Location: Anterior white matter O

  • Originates in cerebral cortex. Most sources indicate fibers do not decussate*

• Function: Convey information to cause voluntary movement of the neck and shoulder girdle muscles

What occurs if the anterior corticospinal tract is injured?

spastic paresis (effect less significant than damage to lateral corticospinal tract)

Reticulospinal tract

• Location: Anterior white matter

  • Originates in brainstem. Most fibers do not decussate

• Function: Facilitation and inhibition of voluntary and reflex activity for automatic posture and gait-related movements. Provide a pathway by which the hypothalamus can control sympathetic thoracolumbar outflow and parasympathetic sacral outflow

What occurs if the reticulospinal tract is injured?

Impair autonomic function; impair posture and walking due to loss of control of limb flexors; hypertonicity and muscle spasms. Hyperactive tendon reflexes and + Babinski.

Babinski reflex

• Performed by running a blunt object along the lateral border of the foot.

• Positive Babinski test: Great toe extends and possible splaying of other toes. Normal in infants. Sign of UMN lesion in adults

• Negative Babinski Test: Toes will flex. Normal for adults

Vestibulospinal

• Location: Anterior white matter

• Originates in brainstem vestibular nuclei. These are bilateral tracts (some decussate, others do not).

• Function: Control proximal limb muscles (extensors) used for posture and gait.

What occurs if the vestibulospinal tract is injured?

Loss of control of postural muscles, impaired balance (ataxia)

Rubrospinal spinal tract

responsible for motor input of gross postural tone, facilitating activity of flexor muscles and inhibiting the activity of extensor muscles

Tectospinal tract

Responsible for contralateral postural tone associated with auditory/visual stimuli

Anterior spinal artery

supplies the anterior 2/3 of the spinal cord

Posterior spinal arteries 

– supply the posterior 1/3

Segmental arteries

supply the related spinal cord segment

Spinal shock

Period following the spinal cord injury in which there is no sensation or movement below the injured spinal cord segment. Reflexes and bowel/bladder control are typically lost. As the swelling decreases, some function may return

Quadriplegia (tetraplegia)

motor impairment to all 4 limbs

Paraplegia 

motor impairment to the lower extremities only

Hemiplegia

motor impairment to one side of the body

Monoplegia

motor impairment to one limb

Complete spinal cord injury

Complete paralysis and a complete loss of sensation below the level of injury

Incomplete spinal cord injury

Any motor or sensation remains intact below the level of the lesion

• Includes sacral sparing (ability to contract anal sphincter)

Physical lesion “above” the level 

Sensation, movement, and tone are normal

Physical lesion “at” the level 

• Sensation: Lost (sensory neurons going to dorsal horn destroyed)

• Movement: Paralyzed (Lower motor neurons destroyed)

• Tone: Hypotonic flaccid paralysis (Damage of LMN)

Physical lesion “below” the level

• Sensation: Lost (ascending tracts to carry info destroyed)

• Movement: Paralyzed (descending pathways can’t transmit signals past lesion)

• Tone: Hypertonic (Damage of UMN)

C1-C4

• Structures: Neck Muscles

• Functional effect: Neck stability and mobility

• Effect of injury: Loss of neck stability

C3-C5

• Structures: Diaphragm

• Functional effect: Breathing

• Effect of injury: Ventilator dependent

C5-T1

• Structures: Upper Extremity

• Functional effect: Upper extremity movement

• Effect of injury: Tetraplegia

T1-L5

• Structures: Trunk muscles Intercostals Abdominal wall muscles

• Functional effect: Trunk stability and movement Accessory respiratory muscles 

• Effect of injury: Loss of trunk stability Decreased respiratory function

L2-S4

• Structures: Lower extremity

• Functional effect: Lower extremity movement

• Effect of injury: Paraplegia

S2-S4

• Structures: Pelvic diaphragm Genitals

• Functional effect: Sphincter control (bladder and bowel) Sexual function

• Effect of injury: Neurogenic bladder/bowel Loss of sexual function

Asia Impairment Scale (AIS): A rating

Complete. No sensory or motor function is preserved in the sacral segments S 4-5.

Asia Impairment Scale (AIS): B rating

Sensory Incomplete. Sensory, but not motor function is preserved below the neurological level and includes the sacral segments S 4-5 AND no motor function is preserved more than three levels below the motor level on either side of the body.

Asia Impairment Scale (AIS): C rating

Motor Incomplete. Motor function is preserved at the most caudal sacral segments for voluntary contraction OR meets the criteria for sensory incomplete status and has some sparing of motor function more than three levels below the ipsilateral motor level on either side.

Asia Impairment Scale (AIS): D rating

Motor Incomplete. Motor incomplete status as described above with at least half of key muscle functions below the single NLI having a muscle grade of at least 3/5

Asia Impairment Scale (AIS): E rating

Normal

Brown-Sequard Syndrome

Symptoms:

• Ipsilateral flaccid paralysis of muscle at the physical injury level

• Ipsilateral spastic paralysis of muscles below the lesion site

• Ipsilateral sensory loss at the lesion level

• Ipsilateral loss of proprioception, vibration and 2-point discrimination below the lesion level

• Contralateral loss of pain and temperature Usually caused by a stab sensation below the level of the lesion

Central cord syndrome 

• Typically caused by damage to the center of the spinal cord by traumatic bending of the cervical spine

• Symptoms:

  • Flaccid paralysis of the UE muscles and UE sensory loss

Anterior Cord Syndrome 

Damage to the anterior part of the spinal cord; posterior white matter spared. Caused by traumatic bending of the cord or conditions that narrow that spinal canal

• Symptoms:

  • Conscious proprioception, vibration and 2- point discriminative touch remains intact

  • Loss of motor function below lesion

  • Loss of pain and temperature below lesion

Cauda Equina Syndrome

• Damage occurs below L1 Considered to be a peripheral nerve injury

• Symptoms:

  • Flaccidity

  • Areflexia

  • Impairment of bowel and bladder function