SPINAL CORD

The spinal cord extends from the foramen magnum to L1–L2 vertebral level in adults. It transmits motor, sensory, and autonomic impulses between the brain and peripheral nervous system.

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Major Tracts in the Spinal Cord

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Ascending Tracts

• Posterior columns – vibration, position, fine touch

• Spinothalamic tracts – pain and temperature

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Descending Tracts

• Corticospinal tracts – voluntary motor control

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Segmental Organization

Each spinal segment supplies:

• A dermatome (sensory)

• A myotome (motor)

• Reflex activity

Spinal cord lesions typically produce:

• Bilateral motor weakness

• Sensory level

• Autonomic dysfunction (bladder, bowel)

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General Signs

• UMN signs below the lesion

• LMN signs at the level of lesion

• Loss of reflexes at lesion level

• Hyperreflexia below lesion

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Autonomic Involvement

• Early bladder involvement

• Constipation

• Sexual dysfunction

A complete lesion interrupts all ascending and descending tracts.

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Clinical Features

• Complete loss of motor function below lesion

• Complete sensory loss below lesion

• Loss of bladder and bowel control

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Spinal Shock

• Initial flaccid paralysis

• Areflexia

• Hypotonia

Later progresses to:

• Spasticity

• Hyperreflexia

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Common Causes

• Trauma

• Tumors

• Severe compression

Results from hemisection of the spinal cord.

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Clinical Features

Side ---->  Deficit

Ipsilateral-  UMN weakness below lesion

Ipsilateral-  Loss of vibration and position

Contralateral-  Loss of pain and temperature

Causes

• Penetrating trauma

• Tumors

• Multiple sclerosis

Results from ischemia of anterior two-thirds of spinal cord.

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Clinical Features

• Loss of motor function

• Loss of pain and temperature

• Preservation of posterior column sensations

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Causes

• Aortic pathology

• Severe hypotension

• Vertebral artery disease

Most commonly seen in cervical cord injuries.

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Clinical Features

• Greater weakness in upper limbs than lower limbs

• Variable sensory loss

• Bladder dysfunction

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Mechanism

• Involvement of central gray matter

• Upper limb fibers affected more

Selective involvement of posterior columns.

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Clinical Features

• Loss of vibration and proprioception

• Sensory ataxia

• Positive Romberg sign

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Causes

• Vitamin B12 deficiency

• Tabes dorsalis

• Multiple sclerosis

Involves the terminal end of the spinal cord.

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Clinical Features

• Early bladder and bowel dysfunction

• Saddle anesthesia

• Mild motor weakness

Results from compression of nerve roots below L1.

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Clinical Features

• Severe radicular pain

• Asymmetric lower limb weakness

• Saddle anesthesia

• Late bladder involvement

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Feature                     | Conus            | Cauda    
Onset                         | Sudden          | Gradual    
Pain                             | Mild                 | Severe    
Bladder                     | Early                | Late      
Weakness                | Symmetric    | Asymmetric
 

Localization is based on:

1. Sensory level

2. Motor involvement

3. Reflex changes

4. Autonomic features

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Cervical Cord Lesion

• Quadriparesis

• Upper limb LMN signs at level

• Lower limb UMN signs

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Thoracic Cord Lesion

• Paraparesis

• Sensory level on trunk

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Lumbar Cord Lesion

• Lower limb weakness

• Early bladder involvement

1. Determine onset (acute vs chronic)

2. Look for sensory level

3. Assess bladder involvement

4. Correlate motor and reflex findings