Spinal Cord Injury

Slide 1 · Spinal Cord Injury

Pathogenesis · Morphology · Clinicopathologic localization

Dr Abu Suraih Sakhri

MBBS, MD (Pathology)

www.abusuraihsakhri.com

Slide 2 · Learning outcomes

Explain how vertebral displacement produces focal cord injury and tract disconnection.

Relate lesion level and tissue compartment to motor, sensory, and respiratory deficits.

Recognize acute hemorrhagic–necrotic injury, later cystic gliosis, and Wallerian degeneration.

Integrate neuropathology with neurological examination and imaging.

Mechanical insult

Local tissue loss

Tract disconnection

Functional deficit

Slide 3 · Spinal cord injury: Pathological definition

Traumatic insult damages neurons, axons, supporting cells, and/or cord microvasculature.

The neurological syndrome reflects both tissue destruction at impact and interruption of long pathways.

Functional deficit may extend far beyond the small anatomic region that is directly injured.

Impact

Cranial

Caudal

Slide 4 · Why a small cord lesion can be devastating

Many ascending and descending pathways are concentrated within a narrow cross-sectional area.

Long tracts carry signals between the brain and multiple spinal segments.

An interruption at one level can affect function throughout caudal regions.

Lesion

Rostral

Caudal

Slide 5 · Typical mechanical setting

Most traumatic cord injuries accompany transient or permanent displacement of the vertebral column.

Mechanical displacement can transmit deforming forces to the enclosed cord.

Bone alignment alone does not fully characterize intramedullary tissue damage.

Vertebra

Cord

Slide 6 · Spinal motion and injury severity

A high-energy force can deform the cord during the event of impact.

Compression, stretching, and shear may coexist in an individual injury.

Final neurological damage reflects the spatial distribution of tissue injury, not only an external fracture.

Initial insult

Cell / vessel damage

Clinical deficit

Slide 7 · From trauma to neurological impairment

Primary mechanical injury disrupts cellular elements and blood vessels.

Secondary vascular and inflammatory injury can extend tissue damage.

Axonal disruption and local gray-matter loss together account for functional deficits.

Mechanical impact

Hemorrhage + necrosis

Secondary expansion

Pathway loss

Slide 8 · White matter and gray matter are injured differently

White matter contains long myelinated axons that connect distant neural regions.

Gray matter houses local neuronal cell bodies, synapses, and segmental circuits.

White-matter disruption disconnects; Gray-matter necrosis removes segmental processing.

Schematic transverse cord

Slide 9 · Primary axonal disruption

Long tracts may be damaged at the level of impact.

Signals from the brain cannot reliably cross the affected axonal segment.

Even distant intact spinal segments can become functionally disconnected.

Axon / myelin (schematic)

Injured segment

Slide 10 · Ascending pathways: Sensory information

Ascending tracts transmit peripheral sensory information toward higher centers.

Cord injury can prevent sensory information arising caudal to the lesion from reaching the brain.

A sensory level can therefore localize the functional interruption.

Lesion

Degeneration

Rostral

Caudal

Slide 11 · Descending pathways: Motor commands

Descending tracts convey central motor signals to spinal motor networks.

Interruption impairs voluntary motor output below the injury.

Motor manifestations depend on tract involvement and the lesion level.

Lesion

Degeneration

Rostral

Caudal

Slide 12 · Segmental gray-matter destruction

Trauma at the lesion epicenter can directly destroy spinal neurons and interneurons.

Damage to local motor circuits may produce segmental dysfunction.

Segmental tissue loss coexists with long-tract disconnection in severe injuries.

Schematic transverse cord

Slide 13 · A conceptual two-component lesion

Local lesion: Hemorrhage, necrosis, and loss of neurons at the impact site.

Long-distance consequence: Interrupted axons impair connection with more caudal cord.

The combination is more informative than describing only the visible lesion epicenter.

Ascending sensory axon

Injury site

Descending motor axon

Distal = away from each neuron’s soma

Slide 14 · Lesion level determines distribution

Neurological manifestations depend strongly on the rostrocaudal level of injury.

Higher lesions place more descending/ascending pathways and segmental functions at risk.

Interpret the affected vertebra separately from the neurological level of injury.

Cervical

Thoracic

Lumbar / sacral

Rostral

Caudal

Slide 15 · Cervical injury: Tetraplegic pattern

Cervical cord injury can impair both upper and lower limbs.

Degree of arm/hand involvement varies with the specific segment and spared pathways.

High cervical injury may also compromise breathing.

Cervical

Thoracic

Lumbar / sacral

Rostral

Caudal

Slide 16 · Thoracic injury: Paraplegic pattern

Thoracic-region cord injury typically spares motor pathways serving the arms.

Legs and trunk functions below the lesion may be impaired.

Autonomic and sensory deficits may accompany paralysis.

Cervical

Thoracic

Lumbar / sacral

Rostral

Caudal

Slide 17 · Above C4: The respiratory hazard

The possibility of respiratory compromise when injury is above C4.

Disrupted descending drive to the phrenic motor system can impair diaphragm function.

Respiratory evaluation is therefore central to acute localization and safety.

Brainstem drive

C3–C5 phrenic neurons

Diaphragm activation

High cervical disruption

Slide 18 · Phrenic motor output: C3–C5

Phrenic motor neurons receive segmental contributions largely from C3–C5.

Very high cervical lesions can interrupt descending control of diaphragm activation.

The neurological deficit is determined by neural damage, not vertebral numbering alone.

Brainstem drive

C3–C5 phrenic neurons

Diaphragm activation

High cervical disruption

Slide 19 · Vertebral level ≠ cord segment

The bony vertebral level and the neurological spinal cord segment are not always identical.

This distinction is particularly important in the lower spine.

Report imaging anatomy and neurological examination as related but distinct findings.

Vertebra

Cord

Slide 20 · Loss of function below the injury

Descending motor output may fail to reach otherwise intact caudal motor neurons.

Ascending sensory traffic may fail to cross the injured level.

Below-level impairment need not mean uniform necrosis throughout the distal cord.

Lesion

Rostral

Caudal

Slide 21 · Complete and incomplete lesions

A neurological injury can abolish all tested sacral sensory and motor function or preserve some pathways.

Apparent severe weakness does not alone establish neurological completeness.

Standardized classification requires sacral testing rather than inspection of a cord image.

Complete: No sacral sparing

Incomplete: Sacral sparing

Slide 22 · Primary versus secondary tissue injury

Primary injury is the direct mechanical destruction at impact.

Secondary injury evolves through ischemia, edema, excitotoxicity, oxidative stress, and inflammation.

Secondary events help explain why the pathologic field may exceed the initial mechanical focus.

Mechanical impact

Hemorrhage + necrosis

Secondary expansion

Pathway loss

Slide 23 · A morphological time sequence

Acute: Hemorrhage, necrosis, and axonal swelling at the lesion site.

Evolution: Inflammatory clearance and loss of destroyed parenchyma.

Chronic: Central cystic cavitation, reactive gliosis, and distant tract degeneration.

Acute

Hemorrhage / necrosis

Evolving

Debris clearance

Chronic

Cavity + gliosis

Slide 24 · Acute hemorrhage within the cord

Vessel disruption introduces blood into injured spinal parenchyma.

Hemorrhage marks damage near the lesion epicenter and may coexist with edema.

Blood extravasation is a genuine morphologic finding—not equivalent to complete transection.

Schematic transverse cord

Slide 25 · Acute necrosis at impact

Direct mechanical and vascular injury can destroy neurons and glia.

Necrosis eliminates functional tissue rather than merely suppressing impulse conduction.

The acute lesion can involve both central gray matter and nearby white matter.

Schematic transverse cord

Slide 26 · Axonal swelling in surrounding white matter

Swollen axons in white matter around the acute injury.

Axonal swelling signals disrupted axonal integrity and transport.

Surrounding tract injury may be wider than the focus of frank hemorrhage.

Axon / myelin (schematic)

Injured segment

Slide 27 · Spatial tapering away from the epicenter

The greatest structural destruction is typically centered on the impact zone.

Histological severity decreases in cord sections farther above or below the focus.

Distant degeneration follows tract direction and should be distinguished from the local injury field.

Cranial

Caudal

Slide 28 · Secondary hypoperfusion and ischemia

Microvascular injury and tissue swelling can worsen delivery of oxygen and substrates.

Ischemic stress promotes further neuronal and glial dysfunction.

A mechanically small lesion can have a biologically amplified injury zone.

Mechanical impact

Hemorrhage + necrosis

Secondary expansion

Pathway loss

Slide 29 · Excitotoxic signaling

Injured neural tissue may release excess excitatory neurotransmitters.

Ionic dysregulation and calcium overload can intensify cellular damage.

This is a secondary-injury mechanism, not a directly visible histologic diagnosis.

Initial insult

Cell / vessel damage

Clinical deficit

Slide 30 · Oxidative injury

Secondary inflammatory and ischemic processes generate reactive oxygen species.

Oxidative stress can injure membranes, proteins, and neural cells.

It contributes to secondary injury but is not identified by routine H&E alone.

Initial insult

Cell / vessel damage

Clinical deficit

Slide 31 · Inflammation after traumatic necrosis

Resident microglia and infiltrating phagocytes respond to damaged tissue.

Inflammation removes debris but can also amplify local tissue injury.

The response evolves as acute necrosis transitions toward gliosis and cavitation.

Mechanical impact

Hemorrhage + necrosis

Secondary expansion

Pathway loss

Slide 32 · Oligodendrocyte loss and demyelination

Oligodendrocytes maintain myelin around multiple CNS axons.

Secondary cell injury can impair surviving axons by loss of myelin.

Axonal continuity and myelin integrity are related but distinct determinants of conduction.

Axon / myelin (schematic)

Injured segment

Slide 33 · Edema expands functional injury

Swelling increases tissue pressure in an anatomically constrained compartment.

Edema may compromise microvascular flow and impulse conduction.

Imaging-visible edema cannot on its own establish irreversible neuronal loss.

Impact

Cranial

Caudal

Slide 34 · Phagocytic removal of necrotic tissue

Microglia and blood-derived macrophages clear fragmented cell and myelin debris.

Macrophage-rich tissue is part of injury evolution, not an independent disease.

The removed necrotic center may later appear as a cystic cavity.

Acute

Hemorrhage / necrosis

Evolving

Debris clearance

Chronic

Cavity + gliosis

Slide 35 · Astrocytic reactivity and gliosis

Reactive astrocytes hypertrophy and proliferate around injured tissue.

Gliosis is a major histopathologic marker of CNS injury.

A gliotic rim marks a mature tissue response rather than restored neuronal circuitry.

Schematic transverse cord

Reactive astroglia

Slide 36 · GFAP as an astroglial marker

Astrocytic processes express glial fibrillary acidic protein (GFAP).

GFAP immunostaining can highlight the reactive astroglial border of chronic lesions.

Positive astroglial staining supports gliosis; It is not specific for traumatic etiology.

Schematic transverse cord

Reactive astroglia

Slide 37 · Central cavitation in chronic lesions

Areas of destroyed spinal parenchyma may become cystic over time.

The cystic center reflects tissue loss, rather than formation of normal cord tissue.

Cavitation commonly coexists with surrounding gliosis.

Schematic transverse cord

Slide 38 · Cystic cavity versus gliotic rim

Central compartment: Absence of previously viable neural tissue.

Peripheral response: Astrocytic gliosis at the lesion margin.

A mature spinal lesion therefore contains both a negative space and a reactive cellular border.

Schematic transverse cord

Slide 39 · Late changes are not uniform along the cord

The local lesion remains centered near the injury site.

Distal degeneration tracks along specific affected white-matter bundles.

Serial sections are more informative than a single cross-section.

Cranial

Caudal

Slide 40 · Wallerian degeneration: Definition

An axon segment disconnected from its neuronal cell body undergoes degeneration.

The degenerative process can extend over a long distance from the primary lesion.

Wallerian degeneration is a secondary axonal consequence, not a second traumatic impact.

Axon / myelin (schematic)

Injured segment

Slide 41 · Ascending tract degeneration above injury

Sensory pathways originate in neurons located caudally and project rostrally.

When such axons are severed, their rostral distal segments degenerate above the lesion.

Robbins specifically describes secondary ascending Wallerian degeneration above the focus.

Lesion

Degeneration

Rostral

Caudal

Slide 42 · Descending tract degeneration below injury

Many motor pathways arise rostrally and descend toward spinal levels.

Their distal disconnected segments lie caudal to the injury.

Descending Wallerian degeneration below the lesion.

Lesion

Degeneration

Rostral

Caudal

Slide 43 · Why “distal” changes anatomical direction

Distal is defined relative to the neuron’s cell body, not simply “below the lesion.”

Ascending sensory axons: Distal disconnected segment can be rostral.

Descending motor axons: Distal disconnected segment is usually caudal.

Ascending sensory axon

Injury site

Descending motor axon

Distal = away from each neuron’s soma

Slide 44 · Tract-specific pattern is a localization clue

Degeneration respects anatomic tracts rather than extending indiscriminately.

The side, tract position, and direction of degeneration may help reconstruct injured pathways.

Interpret degenerating tracts in relation to known axonal projection direction.

Lesion

Rostral

Caudal

Slide 45 · White-matter pallor and myelin breakdown

Degenerating axons are accompanied by degeneration of their myelin sheaths.

Chronic affected bundles may show reduced myelin staining and tract atrophy.

Histologic tract changes complement, rather than replace, neurological localization.

Axon / myelin (schematic)

Injured segment

Slide 46 · CNS versus peripheral nerve repair

Peripheral nerve axonal regeneration can be supported by Schwann cell pathways.

Spinal cord long tracts do not routinely recover by equivalent regeneration.

Gliosis, tissue cavitation, and disrupted long connections complicate restoration of function.

CNS: Oligodendroglia

PNS: Schwann cells

Slide 47 · Microscopic sampling strategy

Examine a section through the lesion epicenter for hemorrhage and necrosis.

Compare serial sections immediately rostral and caudal to assess injury taper.

Examine distant white-matter tracts for patterned secondary degeneration.

Cranial

Caudal

Slide 48 · Interpreting tissue stains in context

H&E: Cellular injury, hemorrhage, necrotic debris, and evolving cavity.

Myelin stains: Affected tract pallor or myelin loss when used appropriately.

GFAP: Reactive astroglial response in chronic margins.

Interpret morphology with anatomical level and time after trauma.

H&E: Tissue architecture

Myelin stain: Tracts

GFAP: Astroglia

Slide 49 · Acute and chronic morphology: Comparison

Acute injury emphasizes hemorrhage, necrosis, and axonal swelling.

Chronic injury emphasizes cavitation, gliosis, and long-tract degeneration.

The two patterns may overlap in evolving lesions.

Acute: Hemorrhage / necrosis

Chronic: Gliosis / cavity

Slide 50 · Loss of conduction versus structural loss

Neurologic dysfunction can arise from interrupted conduction in injured pathways.

Histologic necrosis demonstrates irreversible tissue destruction in the sampled area.

Do not infer the degree of viable axonal sparing from a single imaging sequence or thin section.

Ascending sensory axon

Injury site

Descending motor axon

Distal = away from each neuron’s soma

Slide 51 · Paraplegia: Clinicopathologic mapping

A thoracic cord lesion may interrupt descending pathways serving the legs.

Upper-extremity motor circuits remain rostral to the injury.

Sensory and autonomic deficits below the level provide additional localization.

Cervical

Thoracic

Lumbar / sacral

Rostral

Caudal

Slide 52 · Tetraplegia: Clinicopathologic mapping

Cervical lesions can disconnect spinal circuitry supplying all four limbs.

Segmental cervical gray-matter damage can add focal upper-limb weakness.

Functional outcome depends on level, severity, and preserved axonal pathways.

Cervical

Thoracic

Lumbar / sacral

Rostral

Caudal

Slide 53 · Respiratory compromise: Mechanism

High cervical injury may interrupt brainstem drive to phrenic motor neurons.

Diaphragmatic paralysis can threaten ventilation.

A neurological deficit above C4 deserves particular attention to breathing.

Brainstem drive

C3–C5 phrenic neurons

Diaphragm activation

High cervical disruption

Slide 54 · Sensory level and tract interruption

A reproducible sensory level can suggest the segment where ascending input fails.

Different sensory modalities sample different ascending pathways.

Clinical sensory mapping and imaging must be interpreted together.

Lesion

Degeneration

Rostral

Caudal

Slide 55 · Bladder and bowel dysfunction

Spinal cord lesions may disrupt descending regulation of autonomic and somatic circuits.

Dysfunction may persist even when the directly damaged segment is rostral to pelvic organs.

These consequences reflect pathway disconnection, not direct visceral trauma.

Lesion

Rostral

Caudal

Slide 56 · Autonomic dysfunction after cord injury

Descending autonomic connections can be disrupted by injury.

Severe cord injury can affect blood-pressure regulation, sweating, and other autonomic functions.

Autonomic findings add clinical context but are not a substitute for motor/sensory examination.

Initial insult

Cell / vessel damage

Clinical deficit

Slide 57 · Spinal shock versus structural completeness

Early loss of reflex activity may obscure the extent of preserved pathways.

Spinal shock is a physiological syndrome; Anatomical injury is a separate question.

Classify neurological completeness with standardized examination, including sacral assessment.

Physiological suppression

Structural tissue loss

Slide 58 · Clinical examination: What it establishes

Determine segmental motor function, sensory function, and sacral preservation.

Document right–left asymmetry and neurological level systematically.

Repeat examinations can characterize clinical evolution after acute injury.

Mechanical insult

Local tissue loss

Tract disconnection

Functional deficit

Slide 59 · Neuroimaging: Complementary questions

CT helps evaluate bony injury and alignment after trauma.

MRI is better suited to depicting cord edema, hemorrhage, compression, and soft tissues.

Imaging morphology complements, but does not replace, neurological examination.

CT: Vertebral anatomy

MRI: Cord / soft tissues

Slide 60 · ISNCSCI: Current classification framework

The International Standards formalize sensory and motor examination after SCI.

They define neurological level and completeness using standardized criteria.

The current cited edition is the 9th edition (2026); Use its official worksheet for scoring.

Initial insult

Cell / vessel damage

Clinical deficit

Slide 61 · Sacral sparing and neurological completeness

Preserved function in S4–S5 indicates neurological incompleteness.

Absent sacral sensory and motor function is central to the definition of complete SCI.

Structural continuity on MRI is not itself the definition of neurological completeness.

Complete: No sacral sparing

Incomplete: Sacral sparing

Slide 62 · Structural mimics and diagnostic boundaries

Traumatic vertebral injury does not automatically establish spinal cord parenchymal damage.

Spinal nerve-root injury and compressive lesions can produce overlapping deficits.

The lesion must be localized using clinical examination and anatomically appropriate imaging.

Cord / central injury

Root / extra-axial injury

Clinical–imaging correlation

Slide 63 · Case 1: Thoracic impact with leg paralysis

Scenario: Vertebral displacement near the thoracic spine followed by marked bilateral leg weakness.

What is the most likely mechanism of paralysis?

Teaching interpretation: Interruption of descending motor pathways with local spinal damage.

Do not assume the precise completeness grade from weakness alone.

Clinical clue

Likely lesion

Mechanism

Important limit

Slide 64 · Case 2: High cervical injury and ventilation

Scenario: High cervical trauma, severe limb weakness, and inadequate diaphragmatic movement.

Which pathway is most immediately consequential?

Teaching interpretation: Impaired descending drive to phrenic circuitry.

Respiratory risk can coexist with other cord and vertebral injuries.

Clinical clue

Likely lesion

Mechanism

Important limit

Slide 65 · Case 3: Long-standing cord lesion at autopsy

Scenario: Central cystic tissue loss and gliosis at an old cord impact site.

Above the injury: Degeneration of ascending white-matter pathways.

Below the injury: Degeneration of descending white-matter pathways.

The pattern supports both focal trauma and remote Wallerian degeneration.

Clinical clue

Likely lesion

Mechanism

Important limit

Slide 66 · Putting pathology and localization together

Site of impact predicts focal hemorrhagic–necrotic destruction.

Interrupted tract orientation predicts which remote fibers degenerate.

Neurological level and spared pathways predict the distribution of deficits.

Time since injury predicts whether acute changes or chronic cavitation/gliosis dominate.

Mechanical insult

Local tissue loss

Tract disconnection

Functional deficit

Slide 67 · Core pathology synthesis

Acute spinal trauma: Hemorrhage + necrosis + swollen axons.

Topographic pattern: A maximal impact lesion tapering rostrally and caudally.

Late lesion: Central tissue loss with cystic transformation and gliosis.

Long-tract consequence: Ascending degeneration above and descending degeneration below.

Acute

Hemorrhage / necrosis

Evolving

Debris clearance

Chronic

Cavity + gliosis

Slide 68 · Discussion questions

Why can a tiny cervical cord lesion cause more disability than a larger injury elsewhere in the CNS?

Why does ascending Wallerian degeneration appear above the traumatic lesion?

Which chronic changes distinguish tissue loss from functional disconnection?

Why does neurological completeness require sacral examination?

Mechanical insult

Local tissue loss

Tract disconnection

Functional deficit

Slide 69 · Selected references

Robbins, Cotran & Kumar. Pathologic Basis of Disease. 11th edition. 2026.

National Institute of Neurological Disorders and Stroke. Spinal Cord Injury. NIH.

National Institute of Child Health and Human Development. Spinal Cord Injury: Causes and Effects. NIH.

Spinal Cord Injury: Pathophysiology, Multimolecular Interactions, and Underlying Recovery Mechanisms. Int J Mol Sci. 2020;21:7533.

Rupp R et al. International Standards for Neurological Classification of SCI: 9th edition. Top Spinal Cord Inj Rehabil. 2026;32:141–168.