Spinal Cord Runs through the vertebral canal

Extends from foramen magnum to second lumbar vertebra

Regions Cervical Thoracic Lumbar Sacral Coccygeal

Gives rise to 31 pairs of spinal nerves All are mixed nerves

Spinal cord Enlargements Cervical enlargement:

supplies upper limbs Lumbo -sacral enlargement:

supplies lower limbs Conus medullaris- tapered

inferior end Ends between L1 and L2

Spinal Segments & Roots Spinal segment Spinal segment

C8, T12, L5, S5, Cx1C8, T12, L5, S5, Cx1

Anterior (Ventral) RootAnterior (Ventral) RootPosterior (Dorsal) RootPosterior (Dorsal) Root Dorsal Root (Spinal) GanglionDorsal Root (Spinal) Ganglion

Root - RootletsRoot - Rootlets

Spinal SegmentsImportance of the

spinal segments

Coverings of Spinal cord Dura mater: outermost layer;

continuous with epineurium of the spinal nerves

Arachnoid mater: thin and web like

Pia mater: bound tightly to surface Ligamentum Denticulatum Cordotomy Forms the filum terminale

anchors spinal cord to coccyx

Spaces Epidural: external to the dura

Anesthestics injected here Epidural Anesthesia

Subdural space: serous fluid Subarachnoid: between pia

and arachnoid Filled with CSF

Coverings of Spinal cord cont…

Lumbar Puncture – lumbar (terminal) cisternLumbar Puncture – lumbar (terminal) cistern

Lumbar Puncture

Spinal Cord White Matter

Anterior Funiculus (Anterior White Column)

Posterior Funiculus (Posterior White Column)

Lateral Funiculus (Lateral White Column)

Gray Matter

Anterior Horn ------------motor

Posterior Horn -------------- sensory

Lateral Horn ----------------- autonomic (sympathetic)

Gray Commissure -------- anterior and posterior

Cord Organization Principles of Cord Organization

1) Longitudinal Arrangement

Fibers (White Matter) ------------ White Column

Cell Groups (Gray Matter) ------- Gray Column 2) Transverse Arrangement

Afferent & Efferent Fibers

Crossing (Commissural and Decussating) Fibers

3) Somatotopical Arrangement

Somatosensory Pathway(Dorsal Colum)

Somatosensory PathwayPosterior column pathway carries sensation of highly localized touch, pressure, vibration.Posterior column pathway includes:Fasciculus cuneatus

tractFasciculus gracilus tract

- Carries fine touch, pressure, vibration, sterognosis and conscious Proprioceptive sensations.

Dorsal Colum tracts

dorsal cloumnpathway

Dorsal Colum Lesion dorsal column pathway

Leftspinal cord injury

Loss of sense of:•touch•proprioception•vibrationin left leg

Dorsal Colum Lesions

Sensory ataxiaPatient staggers;

cannot perceive position or movement of legs

Visual clues help movement

Rhombergism

Assessment of Dorsal Colum

Case ….An 85-year-old man is being evaluated for gait difficulties. On examination it is found that joint proprioception is absent in his toes. People withimpaired position sense will usually fall if they stand with their feet together and do which of the following?

Flex the neck Extend their arms in front of them Flex the knees Turn the head Close their eyes

Clinical Case A 45 year old woman complained of pain in her right breast

and progressive weakness of her right lower limb for a period of two months, she contacted her Family physician, Her Family physician referred her to a neurologist.

The neurologic evaluation revealed weakness in the right lower limb. This was associated with spasticity (increased tone), hyperreflexia (increased deep tendon reflexes) at the knee and ankle, which also demonstrated clonus.

On the right side there was loss of two-point discrimination, touch ,vibratory sense and proprioception at levels below the hip. The left side showed a loss of pain and temperature sensation below dermatome T-7.

MRI of a patient indicated to have an extramedullary tumor expanding from the dorsal roots at spinal cord levels T-5,6.

Based on the symptoms and clinical findings what is your diagnosis ?

Clinical Case Of Spinal Cord cont..

Anterolateral system

The Anterolateral Pathway

Provides sensations of “crude” touch, pressure, pain, and temperature

Ascend within the anterior or lateral spinothalamic tracts:

What is Pain?“An unpleasant sensory & emotional experience

associated with actual or potential tissue damage, or described in terms of such damage” –

Subjective sensationPain Perceptions – based on expectations, past

experience, anxiety, suggestionsAffective – one’s emotional factors that can affect pain

experienceBehavioral – how one expresses or controls painCognitive – one’s beliefs (attitudes) about pain

Physiological response produced by activation of specific types of nerve fibers

Experienced because of nociceptors being sensitive to extreme mechanical, thermal, & chemical energy.

Composed of a variety of discomforts One of the body’s defense mechanism (warns the brain

that tissues may be in jeopardy)

Where Does Pain Come From?

Cutaneous Pain – sharp, bright, burning; can have a fast or slow onset

Deep Somatic Pain – stems from tendons, muscles, joints, periosteum, & b. vessels

Visceral Pain – originates from internal organs; diffused @ 1st & later may be localized (i.e. appendicitis)

Psychogenic Pain – individual feels pain but cause is emotional rather than physical

Anterolateral System (Pain &Temp)

spinothalamic pathwayLeftspinal cord injury

Loss of sense of:•Touch•Pain•Warmth/coldin right leg

Spinothalamic TractsSpinothalamic TractsLocated lateral and ventral to

the ventral horn Carry impulses concerned

with pain and thermal sensations (lateral tract) and also non- discriminative touch and pressure (medial tract)

Fibers of the two tracts are intermingled to some extent

In brain stem, constitute the spinal lemniscus

Fibers are highly somato-topically arranged, with those for the lower limb lying most superficially and those for the upper limb lying deeply

Lateral Spinothalamic TractLateral Spinothalamic TractCarries impulses concerned

with pain and thermal sensations.

Axons of 1st order neurons terminate in the dorsal horn

Axons of 2nd order neuron (mostly in the nucleus proprius), decussate within one segment of their origin, by passing through the ventral white commissure & terminate on 3rd order neurons in ventral posterior nucleus of the thalamus

Thalamic neurons project to the somatosensory cortex

Anterior Spinothalamic TractAnterior Spinothalamic TractCarries impulses concerned

with non- discriminative touch and pressure

Axons of 1st order neurons enter cord terminate in the dorsal horn

Axons of 2nd order neuron (mostly in the nucleus proprius) may ascend several segments before crossing to opposite side by passing through the ventral white commissure & terminate on 3rd order neurons in ventral posterior nucleus of the thalamus

Thalamic neurons project to the somatosensory cortex

The system represents an additional route by which dull, aching pain is transmitted to a conscious level

Some 2nd order neurons terminate in the reticular formation of the brain stem, mainly within the medulla

Reticulothalamic fibers ascend to intralaminar nuclei of thalamus, which in turn activate the cerebral cortex

Spino-reticulo-thalamic SystemSpino-reticulo-thalamic System

Pain Control TheoriesGate Control TheoryEndogenous Opiates TheoryPhantom Pain Refferd Pain

Gate Control TheoryMelzack & Wall, 1965Substantia Gelatinosa (SG) in dorsal horn of

spinal cord acts as a ‘gate’ SG cells of Lamina II act as a inhibitory

neurons and inhibit “T” cells of lamina IV

Larger diameter afferent fibers of touch excite both SG and T cells, Therefore afferent signals of pain sensation from T cells is blocked by stimulation of inhibitory SG cells.

Small diameter afferent fibers excite T cells and Inhibit SG cells Therefore Gate is kept

Descending Pain Inhibition

Descending Pain Modulation (Descending Pain Control Mechanism)Periaqueductal Gray Area (PGA) – release enkephalinsNucleus Raphe Magnus (NRM) – release serotonin

The release of these neurotransmitters inhibit ascending neurons

Stimulation of the PGA in the midbrain & NRM in the pons & medulla causes analgesia.

Endogenous opioid peptides - endorphins & enkephalins

Referred Pain?Dermatomal ruleConvergenceFacilitation

Spinocerebellar TractsSpinocerebellar TractsThe spinocerebellar system

consists of a sequence of only two neurons

Two tracts: Posterior & Anterior

Located near the dorsolateral and ventrolateral surfaces of the cord

Contain axons of the second order neurons

Carry information derived from muscle spindles, Golgi tendon organs and tectile receptors to the cerebellum for the control of posture and coordination of movements

Posterior Spinocerebellar TractsPosterior Spinocerebellar TractsPresent only above level

L3The cell bodies of 2nd

order neuron lie in Clark’s column

Axons of 2nd order neuron terminate ipsilaterally (uncrossed) in the cerebellar cortex by entering through the inferior cerebellar peduncle

Ventral Spinocerebellar TractsVentral Spinocerebellar TractsThe cell bodies of 2nd order neuron

lie in base of the dorsal horn of the lumbosacral segments

Axons of 2nd order neuron cross to opposite side, ascend as far as the midbrain, and then make a sharp turn caudally and enter the superior cerebellar peduncle

The fibers cross the midline for a second time within the cerebellum before terminating in the cerebellar cortex

Both spinocerebellar tracts convey sensory information to the same side of the cerebellum

Spinotectal TractSpinotectal TractAscends in the anterolateral

part in close association with spinothalamic system

Primary afferents reach dorsal horn through dorsal roots and terminate on 2nd order neurons

The cell bodies of 2nd order neuron lie in base of the dorsal horn

Axons of 2nd order neuron cross to opposite side, and project to the periaquiductal gray matter and superior colliculus in the midbrain

Indirect spinocerebellar pathway (spino-olivo-cerebellar)

Impulses from the spinal cord are relayed to the cerebellum via inferior olivary nucleus

Conveys sensory information to the cerebellumFibers arise at all level of the spinal cord

Spino - olivary TractSpino - olivary Tract

Spinoreticular TractSpinoreticular TractOriginates in laminae IV-

VIIIContains uncrossed

fibers that end in medullary reticular formation & crossed & uncrossed fibers that terminate in pontine reticular formation

Form part of the ascending reticular activating system

Spino-Olivary TractsProject to accessory olivary nuclei and

cerebellum.Contribute to movement coordination

associated primarily with balance.

Spinotectal TractsProject to superior colliculi of midbrain.Involved in reflexive turning of the head and

eyes toward a point of cutaneous stimulation.

Spinoreticular TractsInvolved in arousing consciousness in the

reticular activating system through cutaneous stimulation.

Grey Matter Of Spinal cord White Matter Anterior Funiculus (Anterior White Column) Posterior Funiculus (Posterior White Column) Lateral Funiculus (Lateral White Column)

Gray Matter Anterior Horn ------------ motor Posterior Horn -------------- sensory Lateral Horn ----------------- autonomic

(sympathetic) Gray Commissure -------- anterior and

posterior

Principles of Cord Organization

1) Longitudinal Arrangement Fibers (White Matter) ------------- White Column

Cell Groups (Gray Matter) ------- Gray Column 2) Transverse Arrangement

Afferent & Efferent Fibers

Crossing (Commissural and Decussating) Fibers

3) Somatotopical Arrangement

Principles of Cord Organization

Lamina of Rexed Lamina I ---------- posteromarginal nucleus Lamina II ---------- substantia gelatinosa of Rolando Lamina III, IV ----- nucleus proprius Lamina V, VI Lamina VII --------- intermediate gray intermediolateral cell column (ILM) Clarke’s column (Nucleus dorsalis) intermediomedial cell column (IMM) Lamina VIII Lamina IX ---------- anterior horn (motor) cell Lamina X ----------- gray commissure

Lamina of Rexed

Alpha Motor NeuronsMotor UnitMotor End Plate

PhasicTonic