Pathophysiology
From the definition of cervical spondylosis, it can be seen that the following conditions must be present for the occurrence and development of cervical spondylosis: first, degenerative changes mainly in the cervical intervertebral discs; second, the degenerated tissues and structures must constitute compression or irritation to organs or tissues such as the cervical spinal cord or blood vessels or nerves or trachea, thus causing clinical symptoms. The intervertebral discs are bloodless tissues, and the degeneration of the nucleus pulposus and the fibrous ring occurs due to changes in the nutritional metabolism of the cartilage plate. On the one hand, the degenerated nucleus pulposus protrudes and directly compresses the spinal cord through the ruptured annulus fibrosus; on the other hand, dehydration of the nucleus pulposus reduces the height of the intervertebral space, loosens the intervertebral body, and stimulates the formation of bone redundancy at the posterior edge of the vertebral body; moreover, the loosening of the vertebral joint also causes hyperplasia of the hook vertebral joint, the small posterior joint protrusion, and the yellow ligament.
However, from the pathological point of view, cervical spondylosis is a continuous process of pathological reaction, which can be divided into three stages.
1. Intervertebral disc degeneration stage
Degeneration of the intervertebral disc begins at the age of 20. The instability of the vertebral segment caused by degeneration of the fibrous ring is the main cause of accelerated degeneration of the nucleus pulposus. Fibrous degeneration, swelling, fracture and fissure formation can be seen; the nucleus pulposus is dehydrated, the elastic modulus is altered, cracks may form internally, and the degenerated nucleus pulposus may protrude posteriorly with the cartilage plate. If the nucleus pulposus crosses the posterior longitudinal ligament, it is called nucleus pulposus prolapse. The nucleus pulposus may compress the spinal cord as well as compress or irritate the nerve roots. From the biomechanical point of view, the main features of this stage are: change in the elastic modulus of the disc, increase in the intradiscal pressure, intervertebral instability and stress redistribution.
2.Bone spur formation stage
The spur formation stage is also a continuation of the previous stage. The formation of bone spur itself indicates the change of stress distribution in the vertebral segment caused by the degeneration of the intervertebral disc in which it is located. From the biomechanical point of view, the formation of bone flab and the hypertrophy of the small joints and ligamentum flavum are compensatory reactions. The result is the re-establishment of mechanical equilibrium. This is a defense mechanism of the body. From the pathological point of view, most scholars believe that the bone flab originates from the mechanization, ossification or calcification of the ligament-disc interstitial space hematoma. Bone spurs of longer duration are as firm as ivory.
Bone spurs are seen on both sides of the barbels, the margins of the small joints, and the posterior-superior margins of the vertebral bodies. The posterior inferior border of the vertebral body and the anterior border of the vertebral body are also not uncommon. In the later stage, there may be extensive osteophytes, and the ligamentum flavum and the posterior longitudinal ligament may also be proliferated at the same time. Bone growths located at the posterior edge of the vertebral body mainly stimulate the spinal cord and dura. The lateral bony spurs such as hooks and small joints mainly stimulate the root cuff and cause radicular symptoms. It is only when the bone spur at the anterior edge of the vertebral body is very large that the esophagus may be irritated.
Since cervical 5 and 6 are at the central point of cervical physiological forward flexion, the discs are under greater stress, so the osteophytes of cervical 5 and 6 are most common, followed by cervical 4 and 5 and cervical 6 and 7.
3.Spinal cord damage segment
As mentioned earlier, degeneration alone does not necessarily produce clinical signs and symptoms, which is the difference between cervical spondylosis and cervical degeneration. It is only when changes in the above two pathological segments affect the surrounding tissues and cause corresponding changes that they become clinically significant.
Spinal compression of the spinal cord can come from both anterior and posterior sources, or both. Anterior compression is dominated by intervertebral discs and osteophytes. Anterior median compression may directly invade the anterior central or sulcus artery of the spinal cord. Anterior paracentral or anterolateral compression mainly invades the anterior horn and anterior cord of the spinal cord and presents with symptoms of conus fasciculi on one or both sides. Lateral and posterior lateral compressions come from the ligamentum flavum, small joints, etc., and present mainly with symptoms of sensory disturbances.
The pathological changes in the spinal cord depend on the intensity and duration of the pressure. Acute compression can cause impaired blood flow, tissue congestion and edema, and after prolonged pressure, vasospasm, fibrous changes, canal wall thickening and even thrombosis. Both gray matter and white matter of the spinal cord are atrophied. The gray matter of the spinal cord is more pronounced. Degeneration, softening and fibrosis, cystic degeneration and cavity formation in the spinal cord occur.
The compression of the spinal nerve roots mainly originates from the hooked vertebral joints and the bony bulge at the lateral posterior border of the vertebral body. Joint instability and lateral-posterior herniation of the disc can also cause irritation and compression of the nerve roots. Early reactive inflammation such as edema and exudation may occur at the root cuff. Continued compression can cause arachnoid adhesions. Arachnoid adhesions make the nerve roots susceptible to strain injury and degeneration or even Wallerian degeneration can occur.
Vertebral artery stenosis due to true hyperplasia and compression is rare. Due to the development of MRI and angiomediography (DSA) techniques. It is now found that the vertebral artery is often twisted or even spiraled during cervical degeneration. The vertebral artery is stimulated by the activity of the vertebral joints, causing different degrees of spasm, which reduces the intracranial blood supply and produces vertigo or even sudden collapse. Loosening and dislocation of the small posterior joints, destruction and hyperplasia of the articular cartilage, and relaxation and hypertrophy of the joint capsule can all stimulate the peripheral nerve fibers located around the joints and produce neck pain. The posterior wall of the cervical disc is also innervated by nerve endings, and relaxation and degeneration of the annulus fibrosus and posterior longitudinal ligament can cause peripheral nerve irritation resulting in neck pain and discomfort.
Classification and clinical characteristics
I. Classification of cervical spondylosis
As the understanding of cervical spondylosis continues to deepen and develop, the classification of cervical spondylosis also continues to improve. The classification of cervical spondylosis is based on two main aspects: symptomatology and pathology. The symptomatology classification is more intuitive and is mainly based on clinical features. However, the symptomatology classification is subject to certain limitations, as exemplified by the early so-called “sympathetic cervical spondylosis”. The pathological classification focuses more on the pathological nature of the lesion and classifies the various pathological stages of cervical spondylosis in a staged approach. In practice, it is sometimes not easy to distinguish this specialized division, and the symptomatology classification is still the main focus.
(I) Cervical cervical spondylosis
The main manifestations are pain in the occipital neck, limitation of neck movement, and stiffness of the cervical muscles. Cervical cervical spondylosis is also called the localized type. That is, the symptoms and signs are confined to the neck.
(II) Neurogenic cervical spondylosis
Neurogenic cervical spondylosis is a more common type of cervical spondylosis, which mainly manifests as sensory and motor deficits and reflex changes consistent with the distribution area of spinal nerve roots.
The nerve root symptoms are associated with the following factors: protrusion and prolapse of the nucleus pulposus, formation of bony redundancy at the posterior edge of the vertebral body, and limited hypertrophy of the posterior longitudinal ligament. However, osteophytes in the small posterior joints, bone spur formation in the hook joint, and loosening and displacement of the three adjacent joints may be important factors in causing symptoms and signs of compression of the spinal nerve roots. In addition, arachnoid adhesions at the root cuff are also associated with nerve root symptoms.
(iii) Spinal cord type cervical spondylosis
Spinal cord cervical spondylosis is more common and has severe symptoms, which often develop into irreversible nerve damage if treatment is delayed. Since the spinal cord is mainly damaged, and the course of the disease is mostly chronic and worsens when triggered, the clinical manifestation is hypesthesia and upper motor neuron injury below the damage plane. The symptoms below the damage plane are mostly numbness, decreased muscle strength and increased muscle tone.
Patients with spinal cord-type cervical spondylosis mostly have spinal stenosis, which develops with the addition of anterior and posterior compression factors. Protruding intervertebral discs, bone flab, posterior longitudinal ligament and yellow ligament cause secondary stenosis of the spinal canal, and if combined with vertebral segment instability, it increases the stimulation or compression of the spinal cord.
(iv) Vertebral artery type cervical spondylosis
The second segment of the vertebral artery passes through the transverse foramen of the cervical spine and travels alongside the vertebral body. When the hook vertebral joint is enlarged, it can cause extrusion and irritation to the vertebral artery, causing insufficient blood supply to the brain and producing symptoms such as dizziness and headache. When the cervical spine is degenerated and the vertebral joints are unstable, the relative displacement between the transverse foramina increases, and the vertebral artery that travels between them is stimulated more often, and the vertebral artery itself can be twisted or even spiraled to come into contact with the hyperplastic leptomeningeal joint.
(V) Mixed cervical spondylosis
It is often found clinically that some patients have a cervical type in the early stage and later develop a neurogenic type. It is also not uncommon for the neurogenic type to co-exist with the spinal cord type. The esophageal compression type alone is quite rare. Therefore, the combination of two or more symptoms at the same time is called the mixed type. This type is also referred to as the diffuse type in the professional classification. Patients with the mixed type have a long disease duration and are older, mostly over 50 years old.
Second, the clinical manifestations of cervical spondylosis
Since the pathological changes of cervical spondylosis are more diverse, each type of cervical spondylosis produces different clinical manifestations and presents different imaging features. On the contrary, due to the diffuse degeneration of vertebral segments in the late stage of the disease, cervical spinal stenosis and cervical spondylosis coexist, and the symptoms of mixed cervical spondylosis can be manifested. The clinical manifestations of each type will be described below, and a comprehensive analysis will be made with the imaging data.
(I) Cervical cervical spondylosis
1. Age: Young and middle-aged people are the majority. Cervical spinal stenosis can develop around the age of 45, individual patients have neck trauma, and almost all patients have long-term low head work.
2, symptoms: the neck feels sore, painful, swollen and other discomfort. This soreness and swelling is mainly in the back of the neck. Female patients often complain of discomfort in the scapular and shoulder areas as well. Patients often complain that they do not know what position to put their head and neck in to be comfortable. Some patients have limited neck movement, and a few patients may have transient upper limb numbness, but no muscle strength loss and walking impairment.
3. Physical signs: Patients generally have no neck distortion. The physiological curvature is reduced or disappeared, and the neck is often pressed and pinched by hand. There may be pressure pain between the spinous process and the paraspinal process.
4.X-ray film: the physiological curvature of cervical vertebrae is straightened or disappeared, and the cervical vertebrae are mildly degenerated. Lateral extension and flexion power radiographs may reveal loosening of the intervertebral space in about 1/3 of cases, showing mild trapezoidal changes, or greater flexion and extension mobility.
(II) Nerve root type cervical spondylosis
1. radicular pain: radicular pain is the most common symptom, and the pain range corresponds to the spinal nerve distribution area of the involved vertebral segment. Accompanying with radicular pain are other sensory disorders in the distribution area of this nerve, among which numbness, hypersensitivity and diminished sensation are common.
2. Radicular muscle disorder: early on, there is an increase in muscle tone, but soon it will be weakened and muscle weakness and muscle atrophy signs will appear. In the hand, the atrophy of interosseous muscle and interosseous muscle is the most obvious.
3, abnormal tendon reflexes: early tendon reflexes are active, while later reflexes gradually weaken, and in severe cases the reflexes disappear. However, pathological reflexes do not appear when there is simple radicular compression, but if there are pathological reflexes, it means that the spinal cord itself is also damaged.
4. Neck symptoms: neck pain and discomfort, and pressure pain in the neck side. There may be pain when compressing the top of the head, and there may also be pressure pain in the spinous process.
5.Special test: When there is a cervical disc herniation, there may be a positive pressure neck test. The spinal nerve pull test is positive. The method is to make the patient sit, the operator holds the patient’s neck with one hand, the other hand holds the patient’s wrist, the two hands are pulled in the opposite direction, if the patient feels pain or numbness in the hand is positive. This is due to the brachial plexus being pulled and the nerve roots being stimulated.
6, X-ray: lateral film can be seen in the cervical spine physiological convexity reduced, straightened or “reverse curve”, narrowing of the intervertebral space, degeneration of the diseased vertebral joint, the formation of bone spurs at the anterior and posterior edges. Intervertebral instability is seen in extension and flexion lateral views. The corresponding ossification of the collateral ligament is common in the plane of the diseased vertebral segment.
7, CT examination: can be found in the lesion segment disc lateral protrusion or posterior osteophytes and to determine the sagittal diameter of the spinal canal. Magnetic resonance examination can also find whether the posterior aspect of the vertebral body has compression on the dural sac. If there is a combination of spinal cord impairment, changes in spinal cord signal can be seen.
(iii) Spinal cord cervical spondylosis
1. Medical history: Patients are 40-60 years old, with a slow onset and about 20% have a history of trauma. Patients often do not think of the cervical spine at first and consult neurology first. The patient often has a history of falling pillow.
2. Symptoms: Patients start with bilateral or unilateral sinking and numbness of the lower limbs, followed by difficulty in walking, tightness of the muscles of the lower limbs, slow lifting and inability to walk fast, and in heavy cases, obvious gait staggering, and even inability to run. Poor coordination of both lower limbs and inability to cross obstacles. Both feet have a cotton-like sensation. Self-reported stiffness in the neck and numbness in the extremities when extending the neck back. Sometimes the symptoms of the upper limbs may appear before the symptoms of the lower limbs, but usually slightly later than the lower limbs. Numbness and pain in the upper extremities appear on one side or both sides successively. In the early stage, the hands feel weak when wringing towels in the morning, often fall to the ground when holding small objects, and cannot button clothes. Some patients have sphincter dysfunction and urinary retention. In addition to the symptoms of the extremities, there is often decreased sensation of the skin below the chest and tightness of the chest and abdomen, i.e., the feeling of girdling.
3. Signs: The most obvious sign is elevated muscle tone in the limbs, and in severe cases, a slight movement of the limbs can induce muscle spasm, which is often more pronounced in the lower limbs than in the upper limbs. The symptoms of the lower limbs are mostly bilateral, but the severity can vary. Muscle tone is also elevated in the upper extremities. However, sometimes the prominent symptoms in the upper extremity are muscle weakness and myasthenia with radicular hyperalgesia, while the lower extremity myasthenia is not obvious, mainly manifested by myospasm, hyperreflexia, ankle clonus and patellar clonus.
Sensory plane examination of the skin often indicates the plane of true spinal cord compression. Furthermore, the distribution of radicular nerve damage is different from the area of nerve trunk damage. Detailed examination of the sensory areas of the hand and forearm helps to localize the area, whereas perceptual deficits of the trunk are often asymmetrical from side to side and are often difficult to determine based on the trunk sensory planes.
Tendon reflexes can be hyperactive in all extremities, especially in the lower extremities. A positive Hoffmann’s sign in the upper extremity (a positive thumb flexion caused by snapping the finger from above or flicking the middle finger from below) or a positive Rossolimo’s sign (a positive toe plantarflexion caused by rapid percussion on the plantar surface of the plantar feet) is more meaningful as a unilateral positive Hoffmann’s sign, which is an important sign when the cervical spinal cord is compressed and often positive bilaterally in severe cases. In addition to hyperactive tendon reflexes in the lower extremities, ankle clonus is more frequent, and Babinski, Oppenheim, Chaddock, and Gordon signs are also positive. The abdominal wall reflex and testicular reflex may be diminished or even absent.