Spinal Cord

Question 1

What are the investing membranes of the spinal cord?

Answer 1

Dura Mater
Tough, fibrous tubular sheath
Extends from foramen magnum to level of S2 vertebra & is continuous with cranial dura

Epidural/Extradural Space
Separates dura from vertebral column.
Contains loose areolar tissue & internal venous plexus.

Subdural Space
Narrow space between dura & underlying arachnoid mater.

Arachnoid Mater
Thin transparent sheath
Separated from underlying pia by subarachnoid space

Subarachnoid Space
Contains cerebrospinal fluid (CSF)

Pia Mater
Closely surrounds spinal cord
Sends septa into its substance

Question 2

What is arachnoiditis?

Answer 2

Arachnoiditis is a disorder caused by the inflammation of the arachnoid.

Question 3

What is the Filum Terminale?

Answer 3

Stabilises cord and dura lengthways

Filum Terminale Internum
Filament formed by pia mater  tip of dural sac
Surrounded by cauda equina, bathed in CSF

Filum Terminale Externum
Extradural continuation
Attaches at tip of dural sac & extends to coccyx and ends as the coccygeal ligament

Filum is formed by pia mater ​

Terminale stabilises the cord distally ​

Spinal cord terminates around T12-L1- L2​

Pointy bit = conus medullaris

Question 4

What is the dentate ligament?

Answer 4

Formed by pia mater​

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Runs along both lateral margins of spinal cord between dorsal and ventral rootlets​

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Medial edge is continuous with pia at side of spinal cord​

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Lateral edge pierces arachnoid at intervals to attach to inside of dura​

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Helps stabilise cord from side to side

Question 5

What is the anatomy of the spinal cord?

Answer 5

Occupies upper 2/3’s of adult spinal canal ​

42-45cm long in adults ​

Divided into  30 segments (8 cervical, 12 thoracic, 5 lumbar, 5 sacral and a few small coccygeal)​

Continuous with medulla superiorly​
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Widens laterally as cervical & lumbosacral enlargements ​

Lumbosacral enlargement tapers off to form conus medullaris, which ends at L1/ L2 level of vertebral column in adults​

Filum terminale consists of pia & glial fibres & often contains a vein

Question 6

What is the grey matter in the internal divisions of the spinal cord?

Answer 6

H-shaped mass of grey matter surrounded by white matter​

Made up of two symmetric portions joined across midline by a transverse connection of grey matter​

Contains central canal or its remnants

CC = central canal – contains​
small amount of CSF (very small amount)​
Motor at the front – bottom of H ​
Sensory at the back = top of H ​
Autonomic - Side of H

Question 7

What is the ventral/anterior horn in the internal divisions of the spinal cord?

Answer 7

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Anterior to central canal ​

Contains cell bodies alpha & gamma motor neurons​

Origin of the lower motor neurons (LMN), the efferent neuron of the peripheral nervous system (PNS) that connects the central nervous system (CNS) with the muscle to be innervated.​

Also, location of anterior horn cell diseases.​

Blood supply – anterior spinal artery.

Polio is an anterior horn disease – not as common now as vaccine ​

Anterior horn = origin of lower motor neuron – target is the muscle that it reaches

Question 8

What is the lateral horn in the internal divisions of the spinal cord?

Answer 8

between dorsal & ventral horns​

Prominent lateral triangular projection in thoracic & upper lumbar regions​

Contains preganglionic cells for autonomic nervous system​

Distal expansion of the H shape sideways is seen only in thoracic

Question 9

What is the dorsal horn in the internal divisions of the spinal cord?

Answer 9

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Posterior to central canal​

Contains many layers (laminas) of nerve cells: lamina I, II, III, IV, V, and VI​

Lamina II contains substantia gelatinosa of Rolando (important part of pain gate theory)​

Other lamina contain neurons that respond to noxious stimuli, position & touch sense, & mechanical signals from skin & joints.

Many lamina are in the circle ​- on powerpoint

Sensory

Question 10

Where is the white matter located in the internal divisions of spinal cord?

Answer 10

Dorsal/posterior White Column (PC)​
Between posterior median sulcus & posterolateral sulcus​

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Lateral White Column​
Between posterolateral sulcus & anterolateral sulcus​

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Ventral White Column​
Lies between anterolateral sulcus and anteromedian fissure

Proprioception/ light touch / vibration / conscious joint position/ determining two points when applied to skin = PCon slide

Question 11

What are the regional characteristics of the spinal cord?

Answer 11

Cervical Levels​
Oval​
Larger than other spinal levels​
Large amount of white matter​

Thoracic Levels​
Round​
Small posterior & anterior horns​
Progressive decrease in white matter from upper to lower levels​
Dorsal nucleus (of Clark)​
Intermediate (unconcious proprioception, spinocerebellar a continuation) ​
Lateral horn - Autonomics

Lumbar Levels​
Round​
Quite large posterior & anterior horns​
Less white matter than higher levels​

Sacral Levels​
Round​
Smaller than lumbar levels​
Consists mainly of gray matter​
Thin shell of white matter​
Intermediate/lateral horn (S2/S3/S4)

Question 12

What are the Pathways in White Matter: Descending Fibre Systems​?

Answer 12

Lateral corticospinal tract​ - Lateral is key one for movements of the limbs = reflex testing
Anterior corticospinal tract​

Bottom 4 are tracts that are working in the background – don’t have clinical significance or testability of the other 2 ​
Vestibulospinal​
Reticulospinal​
Rubrospinal​
Tectospinal

Question 13

What is the lateral corticospinal tract?

Answer 13

Largest descending motor pathway

Function - Fine motor function, modulation of sensory functions​
Course - Motor & premotor cortex > internal capsule > crus cerebri >basis pontis > medullary pyramid > 75-90% decussate in decussation of pyramids > contralateral lateral white column of spinal cord > ventral gray horn > contralateral anterior horn cells

Upper motor neuron ​
If something is going wrong in upper motor neuron something is going wrong within the lateral corticospinal tract ​
Decussation point is in the medullary pyramid​
Upper motor neuron symptoms include weakness/paralysis/hyperactive reflexes/

Question 14

What is the decussation point of the lateral corticospinal tract?

Answer 14

medullary pyramid​

Question 15

What is the Anterior Corticospinal Tract?

Answer 15

Small descending motor pathway​

Function​
Gross and postural motor function (proximal & axial musculature)​

Course​

Motor & premotor cortex > crus cerebri > basis pontis >medullary pyramid > 10-25% do NOT decussate > ipsilateral anterior white column of spinal cord > many decussate via anterior white commissure > ventral gray horn > interneurons > contralateral anterior horn cells

Anterior white commissure where they cross/ decussate

Question 16

What is the decussation point of the Anterior Corticospinal Tract?

Answer 16

ipsilateral anterior white column of spinal cord  many decussate via anterior white commissure

Question 17

What is the vestibular tract and its function?

Answer 17

Vestibular nuclei receive afferents from vestibular apparatus (semicircular canals, utricle & saccule)​

Function​
Postural reflexes, quick movements in reaction to sudden changes in body position (e.g. falling), essential control of antigravity muscles

Question 18

What is the course Lateral Vestibulospinal Tract​?

Answer 18

Lateral vestibular nucleus > medulla (anterior to rubrospinal tract) > ipsilateral anterior white column of spinal cord > ipsilateral gamma & alpha motor neurons > postural control (especially related to movements of head) by inhibiting axial flexor muscles, & stimulating axial extensor muscles

Question 19

What is the course Medial Vestibulospinal Tract​?

Answer 19

Medial vestibular nucleus > mainly to ipsilateral cervical cord > ipsilateral gamma & alpha motor neurons

Question 20

What is the course of the medial longitudinal faciculus?

Answer 20

Contains medial vestibulospinal, tectospinal & reticulospinal fibers  co-ordination of head & eye movements​

Question 21

What is the function and course of the Rubrospinal Tract?

Answer 21

Facilitate flexor & inhibit extensor muscles​

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Course​
Contralateral deep cerebellar nuclei (via superior cerebellar peduncle) & motor cortex bilaterally > red nucleus > contralateral lateral white column > ventral gray horn > alpha & gamma motor neurons

Decorticate vs. Decerebrate​

A UMN lesion above the level of the red nucleus will result in decorticate posture (thumb tucked under flexed fingers in fisted position, pronation of forearm, flexion at elbow with the lower extremity in extension with foot inversion) while a lesion below the level of the red nucleus but above the level of the vestibulospinal and reticulospinal nuclei will result in decerebrate posture (upper extremity in pronation and extension and the lower extremity in extension). The reason for this is that the red nucleus output reinforces antigravity flexion of the upper extremity. When its output is eliminated then the unregulated reticulospinal and vestibulospinal tracts reinforce extension tone of both upper and lower extremities. If there is a lesion in the medulla then all the brainstem motor nuclei as well as the direct corticospinal tract would be out and the patient would be flaccid acutely. If the patient were to survive, tone would return because of interneuronal activity at the spinal cord level.

Question 22

What is the function and course of the tectospinal tract?

Answer 22

Mediates contralateral movements of head in response to auditory, visual and somatic stimuli (protective reflex)​
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Course​
Superior colliculus in tectum of midbrain > decussate soon after origin > descend through brainstem close to medial longitudinal fasciculus > contralateral anterior white column of spinal cord > ventral gray horn of upper cervical segments > alpha & gamma motor neurons

Question 23

What is the function and course of Reticulospinal Tract​?

Answer 23

Modulation of sensory transmission (especially pain), modulation of spinal reflexes, affect muscle tone & posture​

Course​
Scattered throughout midbrain, pons & medulla are cells known as reticular formation

Question 24

What are the Descending Autonomics Function?

Answer 24

Modulation of autonomic functions (e.g. blood pressure, pulse, respiratory rates & sweating)​

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Cerebral cortex, hypothalamus, amygdaloid complex & reticular formation  decussate in brainstem > contralateral lateral white column > autonomic motor cells in lateral gray horns in thoracic and upper lumbar (sympathetic outflow) & midsacral (parasympathetic) levels of spinal cord

Question 25

What is the function and course of Dorsal Column - Medial Lemniscus System?

Answer 25

Function​
Fine touch, vibration, proprioception, 2 point discrimination​

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Course​
Skin, Joints, Tendons  first order sensory neurones  dorsal root ganglia  dorsal gray horn of spinal cord  ipsilateral fasciculus gracilis & fasciculus cuneatus in dorsal white column of spinal cord  2nd order cell bodies in gracile & cuneate nuclei in lower medulla  internal arcuate fibres (axons towards midline)  decussate  medial lemniscus (axons after midline)  brainstem  ventral posterolateral (VPL) thalamic nuclei  somatosensory cortex

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Gracilis – closer to the ground ​
Cuneateus pathways – upper body

Question 26

What is the Anterolateral System ​- Function (Spinothalamic) function and course?

Answer 26

Pain, temperature, crude touch​

Course​

Skin  1st order sensory neurones > dorsal root ganglia  upward (1 or 2 segments) at periphery of dorsal gray horn (Lissauer’s tract) > 2nd order neurones in ipsilateral dorsal horn > decussate > contralateral anterior white column containing anterior spinothalamic tract (crude touch) & lateral white column containing lateral spinothalamic tract (pain & temperature) > branches to reticular formation (spinoreticular), periaqueductal gray (spinotectal), superior colliculus (spinotectal) & hypothalamus (spinohypothalamic) > ventral posterolateral (VPL) nucleus of thalamus  somatosensory cortex

Question 27

What are the functions and course of Dorsal Spinocerebellar Tracts?

Answer 27

Function​

Information from muscle spindles, tendon organs & joint receptors of trunk & lower limbs concerning tension & movement of muscles & joints, coordination of limb movements & maintenance of posture​

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Course​
Skin, muscle spindles, golgi tendon organs, touch & pressure receptors > dorsal root ganglion > 2nd order neurons of dorsal nucleus (of Clark) in lamina VII of dorsal horn, extending from C8-L2 > posterolateral part of ipsilateral lateral column > medulla > inferior cerebellar peduncle > cerebellar cortex​

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Fibers from sacral & lower lumbar levels ascend in dorsal columns  lower part of dorsal nucleus (of Clark)

Question 28

What is the function and course of the Cuneocerebellar Tract​?

Answer 28

Function​
Information of muscle joint sense to cerebellum for upper extremity​

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Course​
Dorsal nucleus (of Clarke) is replaced above C8 by accessory cuneate nucleus ​

Dorsal root fibres originating at cervical levels  2nd order neurons in accessory cuneate nucleus  ipsilateral lateral column of spinal cord  inferior cerebellar peduncle

Question 29

What are the functions and course of the Ventral Spinocerebellar Tracts​?

Answer 29

Function​
Muscle joint information from muscle spindles, tendon organs & joint receptors of trunk, upper & lower limbs​

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Course​
Skin, muscle spindles, golgi tendon organs, touch & pressure receptors  dorsal roots  second order neurones in dorsal nucleus (of Clark)  most decussate in spinal cord  contralateral (minority in ipsilateral) lateral column  medulla  pons  superior cerebellar peduncle  cerebellar cortex  decussate again within cerebellum

Question 30

What are the clinical correlations?

Answer 30

Neurons of dorsal column system decussate in medulla​
Neurons of spinothalamic tract decussate in spinal cord​

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Brainstem/Higher Lesions:​
Contralateral deficits of pain perception, light touch sensation & proprioception​

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Spinal Cord Lesions:​
Contralateral deficit of pain perception​

Ipsilateral deficit of light touch sensation & proprioception

Same side as lesion = UMN weakness / loss of position and vibration

Opposite lesion = loss of pain and temp

Question 31

What is a Spinal Cord Hemi section?

Answer 31

Ipsilateral loss of proprioception, touch, and vibration sense below the lesion due to damage to the ascending dorsal columns ​

Ipsilateral upper motor neuron spastic paralysis below the lesion due to damage to the descending lateral corticospinal tracts ​

Contralateral loss of pain and temperature sensation 2 to 3 levels below the level of the lesion due to damage to the ascending lateral spinothalamic tract which cross 2 to 3 levels above the level of their respective dorsal root ​

Ipsilateral loss of motor and sensory function just at the level of the injured segments due to direct damage to ventral and dorsal grey matter

Question 32

What are the clinical correlations of central cord syndrome?

Answer 32

The lesion interrupts fibers crossing to enter the spino-thalamic tracts, and fibers mediating the tendon stretch reflex. As it enlarges, it affects the intermediolateral columns (autonomic function), and the lateral corticospinal tracts.

Question 33

What are the clinical correlations of Upper Motor Neuron Lesions?

Answer 33

Damage to cerebral hemispheres, internal capsule or lateral white column of spinal cord can produce signs of UMNL’s including spasticity & hyperreflexia​

Commonly seen as a result of strokes​
Other causes include infections or tumours​

Corticospinal, rubrospinal & reticulospinal tracts lie close together/overlap within lateral white column​

Interruption of corticospinal tract is usually accompanied by interruption of the other two tracts

Question 34

What is the sensory testing neurological exam?

Answer 34

Sensory Testing (Within dermatomes)

Pin prick – Pain – Spinothalamic Tract
Light touch – wisp cotton wool - DCML
Temperature – Spinothalamic Tract
Joint position sense – DCML
Vibration (128hz)– DCML (Bony prominence)
Two point discrimination – DCML