Neural Compression Neural Compression PhysiologyPhysiology

Presented By:Presented By:

Joseph S. Ferezy, D.C.Joseph S. Ferezy, D.C.

© 1999© 1999

Each of Us Has, No Doubt, Each of Us Has, No Doubt, Experienced Some Variety Experienced Some Variety of Neural Compression. of Neural Compression. Whether It Be an Arm or Whether It Be an Arm or Leg "Failing Asleep" or a Leg "Failing Asleep" or a Specific Peripheral Specific Peripheral Entrapment Neuropathy.Entrapment Neuropathy.

Mechanisms of Neural Mechanisms of Neural CompressionCompression

• Remain a MysteryRemain a Mystery• Attempt to Review Some of the Attempt to Review Some of the

Current Concepts.Current Concepts.• Remaining Clinically Relevant. Remaining Clinically Relevant.

NeuroanatomyNeuroanatomy

• Main Cell Types of the Nervous Main Cell Types of the Nervous System.System.– There Are Two Major Classes of Cells There Are Two Major Classes of Cells

in the Nervous System.in the Nervous System.• Neurons.Neurons.• Neuroglia.Neuroglia.

NeuronsNeurons

• Functional Cells of the Nervous System.Functional Cells of the Nervous System.• Carry Action Potentials.Carry Action Potentials.• Produce Neurotransmitters.Produce Neurotransmitters.• Participate Directly in Synaptic Activity.Participate Directly in Synaptic Activity.• Convey Signal Some Distance.Convey Signal Some Distance.• Receive Information and Then "Decides" Receive Information and Then "Decides"

Based Upon the Sum of the Excitatory Based Upon the Sum of the Excitatory and Inhibitory Stimuli, to Transmit the and Inhibitory Stimuli, to Transmit the Signal.Signal.

Neuroglia (CNS & PNS)Neuroglia (CNS & PNS)

• Supportive of Neuronal Activity Supportive of Neuronal Activity Providing Mainly Structural and Providing Mainly Structural and Nutritive Support.Nutritive Support.

The The NeuronNeuron

• Receptor Receptor Portion.Portion.

• Integrative Integrative Portion.Portion.

• Trigger Trigger Portion.Portion.

• Conductive Conductive Portion.Portion.

• Effecter Effecter Portion.Portion.

The AxonThe Axon• Larger = Faster.Larger = Faster.• Fiber Size Ranges From 0.2 Fiber Size Ranges From 0.2

Micrometers to 20 Micrometers.Micrometers to 20 Micrometers.• Speeds From .5-100 M/sec.Speeds From .5-100 M/sec.

Four Basic Nerve Cell Four Basic Nerve Cell TypesTypes

• Multipolar - Most Common - Many Multipolar - Most Common - Many Dendrites and a Single Axon.Dendrites and a Single Axon.

• Pseudounipolar Cell (DRG).Pseudounipolar Cell (DRG).• Bipolar - Retina and Olfactory.Bipolar - Retina and Olfactory.• Unipolar Cells - Retinal Rods and Unipolar Cells - Retinal Rods and

Cones.Cones.

Neural Tissue Neural Tissue Morphology Morphology

• Begin With Inner Most Structures and Begin With Inner Most Structures and Work OutWork Out– Axonal Cylinder Is Surrounded by a Myelin Axonal Cylinder Is Surrounded by a Myelin

SheathSheath– In Turn Surrounded by an Endoneurium.In Turn Surrounded by an Endoneurium.– Covered by Perineural Epithelium and a Layer Covered by Perineural Epithelium and a Layer

of Perineural Connective Tissue.of Perineural Connective Tissue.– At This Level Referred to As Nerve FasciculusAt This Level Referred to As Nerve Fasciculus

• Functional UnitFunctional Unit• When Aberrantly Discharging Responsible for When Aberrantly Discharging Responsible for

Clinical Fasciculations.Clinical Fasciculations.

Fasciculus Surrounded by Fasciculus Surrounded by EpineuriumEpineurium

• Gives Rise to Peripheral Nerve.Gives Rise to Peripheral Nerve.

Blood SupplyBlood Supply

• Larger Blood Vessels Originating From Larger Blood Vessels Originating From Nearby Arteries and Veins Course Over Nearby Arteries and Veins Course Over the Surface of the Nerve Trunk.the Surface of the Nerve Trunk.

• Enter the Epineurium.Enter the Epineurium.• Through Numerous Anastomosis, Vessels Through Numerous Anastomosis, Vessels

Communicate With Perineurium of Each Communicate With Perineurium of Each Fasciculus.Fasciculus.

• Penetrating Vessels of the Endoneurium Penetrating Vessels of the Endoneurium Are Primarily Arranged in Longitudinal Are Primarily Arranged in Longitudinal Capillary Beds. Capillary Beds.

Compression Compression Physiology Physiology

• No Blanket Statement Can Be Made No Blanket Statement Can Be Made Regarding Compression.Regarding Compression.

• The Composition of Different Types of The Composition of Different Types of Nerve Tissue Has an Effect on the Nerve Tissue Has an Effect on the Clinical Outcome of Compression.Clinical Outcome of Compression.– Nerve Roots Are Many More Times Nerve Roots Are Many More Times

Susceptible to the Effects of Compression Susceptible to the Effects of Compression Than Are Peripheral Nerves.Than Are Peripheral Nerves.

– Larger Neurons Are More Sensitive to Larger Neurons Are More Sensitive to Compression Then Smaller Ones. Compression Then Smaller Ones.

Parameters of the Parameters of the Compressive ForceCompressive Force

• Acute or ChronicAcute or Chronic• Continuous or IntermittentContinuous or Intermittent• One or Many EpisodesOne or Many Episodes• Mild to Severe in DegreeMild to Severe in Degree• Parameters Are Not Independent of One Parameters Are Not Independent of One

Another.Another.• Final Clinical Effect of Compression Arises Final Clinical Effect of Compression Arises

From a Combination and Interaction From a Combination and Interaction Between Many Different Factors. Between Many Different Factors.

Compression Effects Compression Effects

• Clinically, Compression Can Clinically, Compression Can Directly or Indirectly (Via Vascular Directly or Indirectly (Via Vascular Supply) Lead to Pain And/or Supply) Lead to Pain And/or Dysfunction.Dysfunction.

• Specific Effects on the Nerve Itself Specific Effects on the Nerve Itself May Be Divided Into Categories. May Be Divided Into Categories.

Categories of Compression Categories of Compression EffectsEffects

• Morphological Effects Morphological Effects • Neurophysiological EffectsNeurophysiological Effects• Chemical Effects Chemical Effects • Behavioral Effects Behavioral Effects

Morphological EffectsMorphological Effects

• Purely Morphological Alterations May Purely Morphological Alterations May Not Be Not Be Necessary or SufficientNecessary or Sufficient to to Produce Clinical Effects.Produce Clinical Effects.

• Nerves Are Readily Pliable.Nerves Are Readily Pliable.• Tissue Integrity and Chemical Effects Tissue Integrity and Chemical Effects

(Both Excitatory and Inhibitory) Are an (Both Excitatory and Inhibitory) Are an Exciting, but Largely Unknown Area of Exciting, but Largely Unknown Area of Investigation. Investigation.

Axoplasmic DammingAxoplasmic Damming

Acute Mild Acute Mild CompressionCompression

• Decreased Axon Cylinder Decreased Axon Cylinder Dimensions As Well As Endoneural Dimensions As Well As Endoneural Space.Space.

• Causing Modest Decreases in Causing Modest Decreases in Conduction Velocities or Total Conduction Velocities or Total Blockade. Blockade.

Acute Severe Acute Severe CompressionCompression

• Irreversible Loss of Nerve Function. Irreversible Loss of Nerve Function.

Chronic Mild Chronic Mild CompressionCompression

• Decreased Conduction Velocity.Decreased Conduction Velocity.• Segmental Demyelination.Segmental Demyelination.• Abnormal Permeability Barriers to Abnormal Permeability Barriers to

Extracellular Influences.Extracellular Influences.• Axoplasmic Damming. Axoplasmic Damming.

Chronic Severe Chronic Severe CompressionCompression

• Distal Demyelination.Distal Demyelination.• Abnormal Permeability Barriers to Abnormal Permeability Barriers to

Extracellular Influences.Extracellular Influences.• Axoplasmic Damming.Axoplasmic Damming.

– Complete Blockade. Complete Blockade.

CompressionCompression

Degrees of Injury Degrees of Injury

• According to Sunderland (1978) There Are According to Sunderland (1978) There Are Five Degrees of Neuronal Tissue Damage.Five Degrees of Neuronal Tissue Damage.

• Graded in Increasing Severity From First to Graded in Increasing Severity From First to Fifth Degree.Fifth Degree.

• Increasing Intensities of Both Traction and Increasing Intensities of Both Traction and Compression of Capable of Producing Compression of Capable of Producing Increasing Degrees of Damage.Increasing Degrees of Damage.

• Categories Are Not Mutually Exclusive.Categories Are Not Mutually Exclusive.

• Mixed Injuries Commonly Occur. Mixed Injuries Commonly Occur.

Degrees of Injury – Degrees of Injury – SunderlandSunderland

• First Degree First Degree – Complete Blocking of Conduction Through a Complete Blocking of Conduction Through a

Nerve Segment, With Axonal Continuity Nerve Segment, With Axonal Continuity Preserved.Preserved.

– Impulses Travel Above and Below the Impulses Travel Above and Below the Damaged Segment, but Not Through It.Damaged Segment, but Not Through It.

– No Wallerian Degeneration Occurs, and the No Wallerian Degeneration Occurs, and the Patient Should Be Expected to Completely Patient Should Be Expected to Completely Recover Within Days or Weeks. Recover Within Days or Weeks.

– Equivalent to Seddon’s - NeurapraxiaEquivalent to Seddon’s - Neurapraxia

Degrees of Injury – Degrees of Injury – SunderlandSunderland

• Second DegreeSecond Degree– Axonal Damage and Subsequent Wallerian Axonal Damage and Subsequent Wallerian

Degeneration Does Occur, However the Degeneration Does Occur, However the Endoneurium Remains Intact.Endoneurium Remains Intact.

– Neurons Are Confined to Their Original Neurons Are Confined to Their Original Pathway.Pathway.

– Regeneration Is Therefore Complete, but Regeneration Is Therefore Complete, but Slower. Slower.

– Equivalent to Seddon’s – Axonotmetsis.Equivalent to Seddon’s – Axonotmetsis.

Degrees of Injury – Degrees of Injury – SunderlandSunderland

• Third DegreeThird Degree– Intrafunicular Damage Including Axon Intrafunicular Damage Including Axon

and Endoneural Sheath Derangement.and Endoneural Sheath Derangement.– Nerve Fibers Grow Into Incorrect Nerve Fibers Grow Into Incorrect

Pathways and Regeneration Is Both Pathways and Regeneration Is Both Incomplete and Imperfect. Incomplete and Imperfect.

– Seddon’s Neurotmesis Combines Seddon’s Neurotmesis Combines 33rdrd – 5 – 5thth Degree Degree

Degrees of Injury – Degrees of Injury – SunderlandSunderland

• Forth DegreeForth Degree– Disruption of Funicular Structure and Disruption of Funicular Structure and

Organization.Organization.– Scar Tissue Causes Obstacles to Any Scar Tissue Causes Obstacles to Any

Significant Regeneration Potential. Significant Regeneration Potential.

• Fifth DegreeFifth Degree– Ragged or Clean Tissue Severance.Ragged or Clean Tissue Severance.– Some Axons Regenerate Across a Gap, but Some Axons Regenerate Across a Gap, but

No Clinical Level of Function Can Be No Clinical Level of Function Can Be Expected. Expected.

Seddon's Classification of Seddon's Classification of Nerve Injuries.Nerve Injuries.

• NeurapraxiaNeurapraxia– A Transient Local Conduction Block.A Transient Local Conduction Block.– Mostly Motor Type With Complete Recovery Mostly Motor Type With Complete Recovery

Within Days or Weeks. Within Days or Weeks.

• AxonotmesisAxonotmesis– Indicates Axonal Interruption, With Intact Indicates Axonal Interruption, With Intact

Schwann Cell Membrane.Schwann Cell Membrane.– Wallerian Degeneration Occurs Distal to the Wallerian Degeneration Occurs Distal to the

Stump, but Complete Regeneration May Not Stump, but Complete Regeneration May Not Occur and May Take Months If It Does. Occur and May Take Months If It Does.

– NeurotmesisNeurotmesis• Complete Transection. Complete Transection.