I. Etiology
1.Trauma
The cervical spine is located between the head and the thoracic spine, and is the part of the human spine with the largest range of motion, so there are more chances of injury, and neck trauma in adolescence is an important factor leading to the onset of the disease after middle age.
2.Chronic strain of the neck
Long-term low head work or poor posture, causing strain on the muscles, ligaments and joints of the neck, inflammatory degeneration of the bone and joint of the affected vertebrae, retroflexion of the physiological curvature of the cervical vertebrae, instability and misalignment of the cervical vertebrae, and protrusion of the corresponding posterior vertebrae into the spinal canal, can lead to the onset of spinal cord compression.
3.Cervical degenerative changes
Old age and weakness, liver and kidney deficiency, tendons and bones slack, can cause calcification of cervical ligaments. Degenerative changes of the cervical intervertebral disc, vertebral body and small intervertebral joints are the main reason for the occurrence of cervical spondylosis. If the cervical intervertebral disc protrudes to the rear of the vertebral body, it compresses the spinal cord and causes spinal cord-type cervical spondylosis.
4.Spinal stenosis
Due to the degeneration of the cervical disc, the fibrous ring bulges into the spinal canal and the osteophytes at the posterior edge of the vertebral body protrude into the spinal canal, resulting in spinal canal stenosis. At the same time, when the vertebral space is narrowed, the yellow ligament is relaxed, the cervical spine bone joint is misaligned and destabilized, and compensatory ligament thickening and osteophytes can occur, which aggravates the occurrence of cervical spinal stenosis.
5.Obstructed intramedullary blood circulation
In pathological changes of spinal cord type cervical spondylosis, if the spinal stenosis caused is changed to a certain degree, the spinal cord can be damaged by compression, compressing the gray matter and lateral cords of the central part of the medulla where stress tolerance is weak, so that the intramedullary blood circulation is obstructed and vasodilation or even rupture occurs at the compressed parts. The local lesion tissue is stagnant due to blood stagnation and reduced blood and oxygen supply to the tissue, which can lead to atrophy and necrosis of nerve cells, degeneration of empty cells and hemorrhage.
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Second, the clinical manifestations of cervical spondylosis
Spinal cord-type cervical spondylosis due to cervical spinal stenosis can cause secondary pathological changes in the cervical spine if it is hyperextended and flexed before a clear diagnosis is made. Clinical manifestations, in general, are early bilateral or unilateral lower limbs numbness, pain, stiffness and shivering, weakness and trembling, difficulty in walking, followed by bilateral upper limbs numbness, weakened grip strength, and easy loss of objects. When the above symptoms are aggravated, there may be constipation, difficulty in urination with urinary retention or incontinence symptoms, or bedridden, and may also be complicated by sympathetic symptoms such as dizziness, blurred vision, difficulty in swallowing, and abnormal facial sweating.
1.Conus fasciculus sign
The main feature of spinal cord cervical spondylosis is that its mechanism is due to the direct compression of the cone bundle (corticospinal bundle) by the compressor or the reduction of local blood supply. Clinically, it starts with the weakness of the lower limbs, tightness of the legs (such as leg binding) and the feeling of heavy lifting, etc. Gradually, symptoms such as drifting, limping, easy kneeling (or falling), inability to lift the toes off the ground, clumsy gait and the feeling of chest binding appear. On examination, typical symptoms of the pyramidal fasciculus such as hyperreflexia, ankle clonus, patellar clonus and muscle atrophy can be found, and most of the abdominal wall reflexes and testicular reflexes are diminished or disappeared. The arrangement of the pyramidal bundle in the medulla is in the order of the nerve fibers of the upper cervical extremity, thoracic, lower lumbar extremity and sacral region, which can be divided into three types: central type (upper extremity type), peripheral type (lower extremity type) and anterior central vascular type (extremity type) depending on the location of the involvement.
2.Limb numbness
It is mainly due to the simultaneous involvement of the thalamic tract of the spinal cord, which is similar to the former in the order of fiber arrangement from the inside out for the nerve fibers of the upper cervical extremity, thoracic, lower lumbar extremity and sacral region. Therefore, the location and typing of symptoms are consistent with the former. The distribution of nociceptive and thermo-sensory fibers and tactile fibers in the thalamic tract of the spinal cord is different, so the degree of compression varies, i.e., nociceptive and thermo-sensory impairment is obvious, while tactile sensation may be completely normal.
3.Reflex disorders
(1) Abnormal physiological reflexes Depending on the segment of the spinal cord affected by the lesion, the physiological reflexes may change accordingly, including the biceps reflex, triceps reflex and radial aponeurosis reflex in the upper limbs, and the knee reflex and Achilles tendon reflex in the lower limbs, which are mostly hyperactive or active.
(2) Hoffmann’s sign and palmar chin reflex have the highest positive rate; later in the course of the disease, ankle clonus, patellar clonus and Babinski’s sign can appear.
4. Autonomic symptoms
Clinically, it is not uncommon that all systems are involved, among which the gastrointestinal tract, cardiovascular and urinary systems are the most common and many patients only recall that they may be caused by cervical spondylosis when their symptoms improve after decompression surgery, which is often difficult to detect without detailed inquiry before surgery.
5. Defecation and urinary dysfunction
At first, urinary urgency, poor bladder emptying, urinary frequency and constipation are common, and gradually lead to urinary retention or urinary and fecal incontinence.