Lecturer

Prof. Dr. Ali K. Al-Shalchy

MBChB/ FIBMS/ MRCS/ FRCS

2014

Dorsal root: The dorsal root carries

both myelinated and unmyelinated

afferent fibers to the spinal cord.

Posterior gray column: Long and

narrow column of gray matter reaches

almost to the surface of the spinal cord.

Primarily concerned with sensory input.

Anterior gray column: Short and

broad column of gray matter. Concerned

with motor function. Both posterior and

anterior gray columns are sites where

sensory and motor cell bodies,

respectively, are found.

Ventral root: Bundle of somatic

motor fibers. Constitute the efferent

outflow of the spinal cord.

Anterior median fissure: About 3 mm

deep. Contains blood vessels (anterior

spinal artery) supplying the anterior two

thirds of the cord.

Anterior funiculus: Between the

anterior median fissure and anterolateral

sulcus (ventral root). Merges with the

lateral funiculus. Contains ascending and

descending tracts.

Lateral funiculus: Between the dorsal

and ventral roots. Merges with the anterior

funiculus. Contains ascending and

descending tracts.

Posterior lateral sulcus: Site of entry

of dorsal root.

Posterior funiculus: Between posterior

median sulcus and dorsal root. Contains

ascending tracts.

The spinal cord tracts can be divided into ascending (sensory or afferent) and

descending (motor or efferent) tracts.

The sensory tracts include dorsal column/medial lemniscus system,

anterolateral system, and spinocerebellar tracts ; while the motor tracts include

the pyramidal and extrapyramidal tracts.

In the dorsal column-medial lemniscus

tract, a primary neuron's axon enters the

spinal cord and then enters the dorsal

column. If the primary axon enters below

spinal level T6, the axon travels in the

fasciculus gracilis, the medial part of the

column. If the axon enters above level T6,

then it travels in the fasciculus cuneatus,

which is lateral to the fasciculus gracilis.

Either way, the primary axon ascends

to the lower medulla, where it leaves its

fasciculus and synapses with a secondary

neuron in one of the dorsal column nuclei:

either the nucleus gracilis or the nucleus

cuneatus.

At this point, the secondary axon leaves

its nucleus and passes anteriorly and

medially. The collection of secondary axons

that do this are known as internal arcuate

fibers. The internal arcuate fibers decussate

and continue ascending as the contralateral

medial lemniscus. Secondary axons from

the medial lemniscus finally terminate in

the ventral posterolateral nucleus (VPL) of

the thalamus, where they synapse with

tertiary neurons. From there, tertiary

neurons ascend via the posterior limb of the

internal capsule and end in the primary

sensory cortex.

This system transmits touch,

proprioception and vibration modalities of

sensations.

The anterolateral system works somewhat differently. Its primary neurons axons

enter the spinal cord and then ascend one to two levels before synapsing in the

substantia gelatinosa. The tract that ascends before synapsing is known as Lissauer's

tract. After synapsing, secondary axons decussate and ascend in the anterior lateral

portion of the spinal cord as the spinothalamic tract. This tract ascends all the way to

the VPL, where it synapses on tertiary neurons. Tertiary neuronal axons then travel to

the primary sensory cortex via the posterior limb of the internal capsule.

This system transmits pain and temperature modalities of sensations.

Proprioceptive information in the body travels up the spinal cord via three

tracts. Below L2, the proprioceptive information travels up the spinal cord in the

ventral spinocerebellar tract. Also known as the anterior spinocerebellar tract,

sensory receptors take in the information and travel into the spinal cord. The cell

bodies of these primary neurons are located in the dorsal root ganglia. In the

spinal cord, the axons synapse and the secondary neuronal axons decussates and

then travel up to the superior cerebellar peduncle where they decussate again.

From here, the information is brought to deep nuclei of the cerebellum including

the fastigial and interposed nuclei.

From the levels of L2 to T1,

proprioceptive information enters the

spinal cord and ascends ipsilaterally,

where it synapses in Clarke's nucleus.

The secondary neuronal axons continue to

ascend ipsilaterally and then pass into the

cerebellum via the inferior cerebellar

peduncle. This tract is known as the

posterior spinocerebellar tract.

From above T1, proprioceptive primary

axons enter the spinal cord and ascend

ipsilaterally until reaching the accessory

cuneate nucleus, where they synapse. The

secondary axons pass into the cerebellum

via the inferior cerebellar peduncle where

again, these axons synapse on cerebellar

deep nuclei. This tract is known as the

cuneocerebellar tract.

The corticospinal tract serves as the

motor pathway for upper motor neuronal

signals coming from the cerebral cortex

and from primitive brainstem motor

nuclei.

Cortical upper motor neurons originate

from Brodmann areas 1, 2, 3, 4, and 6 and

then descend in the posterior limb of the

internal capsule, through the crus cerebri,

down through the pons, and to the

medullary pyramids, where about 90% of

the axons cross to the contralateral side at

the decussation of the pyramids.

They then descend as the lateral

corticospinal tract. These axons

synapse with lower motor neurons in

the ventral horns of all levels of the

spinal cord.

The remaining 10% of axons

descend on the ipsilateral side as the

ventral corticospinal tract. These axons

also synapse with lower motor neurons

in the ventral horns. Most of them will

cross to the contralateral side of the

cord (via the anterior white

commissure) right before synapsing.

They are called so because they don’t reach their targets by traveling through the

"pyramids of medulla". Pyramidal tracts go through the pyramids of medulla.

Extrapyramidal tracts indirectly control the anterior horn cells (for modulation and

regulation).

Extrapyramidal system is responsible for gross, synergic movements which require

the activity of large groups of muscles

Radiculopathy

Nerve root impingement with typical pain

radiation and/or motor or sensory impairment

leading to nerve root dysfunction.

Typical Findings: weakness of the index

muscle mainly innervated by that nerve,

diminished reflexes of the same muscle and

dermatomal sensory disturbance.

The most common distribution of

radiculopathy is the lumbar spine followed

by the cervical spine. Radiculopathy is less

common in the thoracic spine.

Pain usually exacerbated with coughing,

sneezing or during defecation.

Myelopathy

Compression or stretching of the spinal cord

can cause myelopathy, which is more common

in the cervical rather than the thoracic spine.

Hyperreflexia and positive Babinski sign are

common.

Sensory deficits include impaired sensory

level, dermatomal sensory disturbance in the

arms, glove-distribution sensory loss in the

hands and posterior column dysfunction.

Motor deficits with arm weakness and

wasting of hand muscles are encountered and

paraparesis can occur . However, hemi- or

tetraparesis are less frequent. Spasticity and

sphincter distubances occur also.

Localized demyelination of the spinal

cord.

Is caused by an immune process

resulting in small vessel vasculopathy,

ischemia, and demyelination.

Symptoms: Clinical picture is identical

to cord transection occurring over hours to

a few days. Most common in the thoracic

cord. Band-like chest pain mimicking

acute myocardial infarction may occur

before the onset of flaccid paralysis,

sensory level, and urinary retention.

Progressive rise in the sensory level may

occur.

Treatment: High-dose intravenous

steroids

Definition: The procedure of taking CSF from the spine in the lower back

through a hollow needle, usually done for diagnostic purposes (e.g.

meningitis).

The patient should lie flat on his

side with the back at the edge of the

bed.

Flexion of hips and knees is

done.

Introduction of 20- to 22-gauge

needle in between 2 spinous

processes (either ,commonly L3-L4,

or L4-L5) exactly in the midline.

By pushing the needle pointing

slightly towards the patient’s head,

piercing the dura is performed at 5-6

cm.

Collect the CSF and send it to

analysis.