IV. SPINAL CORD LESIONS
A. General comments
- The complex of anatomy of the vertebral column and the great concentration
of important tracts in a structure of small cross-sectional area are unique
features related to spinal cord injury. A number of factors influence the
severity of pathological changes and functional deficits after spinal cord
trauma, including age and the flexibility of the body, the size of the
bony canal as influenced by heredity, degenerative changes of joints and
intravertebral discs and variations in blood supply. The spinal levels
most commonly involved with injury are the lower cervical spine (C4, C5,
C6, C7, T1) and the thoracolumbar juncture (T12, L1, L2), the areas of
greater mobility.
B. Pathophysiology
- 1. The spinal cord and nerve roots may be injured by:
a. Compression from bone, ligaments, extruded disc material and
tumors.
b. Disruption or overstretching of neural tissues
c. Edema following compression or concussion
d. Disturbance of circulation
- 2. Mechanisms of injury
- a. Direct injury results from force applied directly to the
back of the neck or trunk and may cause fractures of spinous processes
of laminal arches, concussion of the spinal cord, or direct compression
of neural tissue by depressed bone fragments. Lacerations can result from
knife or bullet wounds.
- b. Indirect injury is a more common mechanism resulting from
forces applied to the head and trunk or from movements that exceed the
normal range, e.g. when the head is suddenly accelerated or decelerated
in relation to the trunk.
C. Pathological changes
- The most common pathological changes are contusions, with necrosis,
swelling and hemorrhage acutely to variable extents. Chronic changes include
macrophages, gliosis and loss of architecture. In addition, edema may occur
in areas that do not show contusions and infarction may result from impairment
of circulation. Wallerian degeneration in distal axons will occur.
D. Clinical signs
- Neurological symptoms vary from complete loss of function below the
injured segments to temporary loss of cord function with complete recovery.
Specific symptoms depend on the site of injury. e.g. posterior horn or
column injury produces paresthesias, pain and other sensory disturbances;
anterior horn or corticospinal tract damage results in weakness or paralysis.
After denervation, fibrillations, fasciculations, muscle atrophy, and groups
of atrophic fibers in a muscle biopsy will be seen.
E. Types of injury
- 1. Fracture dislocation of the spine
2. Hyperextension or hyperflexion with cord compression by a displaced
vertebral body fragment.
3. Cervical spondylosis
4. Intervertebral disc abnormalities and other osseous pathology,
e.g. herniated lumbar disc
5. Neoplasms (intramedullary or extramedullary)