There are various subtypes of lumbar disc herniation, which can be morphologically classified as: bulging, herniated, and prolapsed. Lumbar disc herniation is a diagnosis in Western medicine, but there is no such name in Chinese medicine. Instead, the disease is grouped under the category of “lumbago” and “lumbar leg pain”. This disease is one of the more common lumbar disorders in clinical practice, and is a common and frequent disease in orthopedics. It is mainly due to the degenerative changes of various parts of the lumbar intervertebral disc (nucleus pulposus, fibrous ring and cartilage plate), especially the nucleus pulposus, and then, under the action of external factors, the fibrous ring of the intervertebral disc ruptures and the nucleus pulposus tissue protrudes (or prolapses) from the rupture in the posterior or vertebral canal, causing the adjacent tissues, such as spinal nerve roots and spinal cord, to suffer from stimulation or compression, resulting in a series of clinical symptoms such as lumbar pain, numbness and pain in one or both lower limbs. Numbness, pain and a series of clinical symptoms. The clinical symptoms of lumbar disc herniation can vary greatly depending on the location and size of the nucleus pulposus protrusion and the size of the sagittal diameter of the spinal canal, pathological characteristics, body status and individual sensitivity. Therefore, the recognition and determination of the symptoms of this disease must be fully understood and inferred from the perspective of its pathophysiology and pathological anatomy. The common symptoms of this disease are described as follows. (1) Low back pain: More than 95% of patients with lumbar disc protrusion (prolapse) have this symptom, including those with vertebral body type. (1) Mechanism: It is mainly due to mechanical irritation and compression of adjacent tissues (mainly nerve roots and sinus-vertebral nerves) caused by the degenerated nucleus pulposus entering the vertebral body or posterior longitudinal ligament, or chemical and/or mechanical radiculitis caused by the stimulation of adjacent spinal nerve roots or sinus-vertebral nerves due to the release of glycoprotein and β-protein in the nucleus pulposus and histamine (substance H). ② Manifestation: clinically, persistent dull pain in the low back is common, reduced in the lying position and increased when standing, which is generally tolerable and allows moderate lumbar activity and slow walking, mainly due to mechanical compression. The duration is as little as 2 weeks and as long as several months or even years. The other type of pain is severe lumbar spasm-like pain, which not only has a sudden onset, but also is unbearable and cannot be tolerated without bed rest. This is mainly due to ischemic radiculitis, that is, the sudden protrusion of the nucleus pulposus compressing the nerve root, resulting in a series of changes such as ischemia, bruising, hypoxia and edema due to simultaneous compression of the root blood vessels, and can last for several days to weeks (while this sign can also occur in spinal stenosis, but the duration is very short, only a few minutes). The effect of early relief can be achieved by lying on a plank bed, closed therapy and various dehydrating agents. (2) Radiating pain in the lower extremities: more than 80% of cases have this symptom, and up to 95% of them have the posterior type. (1) Mechanism: The same mechanism as the former, mainly due to mechanical and/or chemical stimulation of the spinal nerve roots. In addition, reflex sciatica (or “pseudosciatica”) may also occur through the sinus nerve of the affected node. ② Manifestation: In mild cases, it is a radiating tingling or numbness from the lumbar region to the back of the thigh and calf, reaching the bottom of the foot; it is generally tolerable. In severe cases, it is a severe electric shock-like pain from the waist to the foot, and is mostly accompanied by numbness. Although the pain is mild, the patient can still walk, but the gait is unstable and limp; the waist is tilted forward or the waist is held by hand to relieve the tension on the sciatic nerve. In severe cases, the patient rests in bed and prefers to take the hip flexion, knee flexion and lateral position. All factors that increase abdominal pressure aggravate radiating pain. Since flexion of the neck can aggravate the stimulation of the spinal nerve by pulling on the dural sac (i.e., flexion test), the patient’s head and neck are mostly in the supine and extended position. The radiological pain is mostly one-sided in the limbs, and only a very small number of central or paracentral herniated nucleus pulposus patients show symptoms in both lower limbs. (3) Numbness of the limbs: Most of them are accompanied by the former, and only about 5% of them simply show numbness without pain. This is mainly due to the stimulation of proprioceptive and tactile fibers in the spinal nerve roots. The extent and location depends on the number of nerve root sequences involved. (4) Cold sensation in the limbs: In a few cases (about 5% to 10%), the limbs are cold and chilly, mainly due to the stimulation of sympathetic nerve fibers in the spinal canal. Clinically, it is common to find cases in which the patient complains of warmth in the limbs on the day after surgery, with this being the same mechanism. (5) Intermittent claudication: The mechanism and clinical manifestations are similar to those of lumbar spinal stenosis, mainly because of the pathological and physiological basis of secondary lumbar spinal stenosis that can occur in the case of a herniated nucleus pulposus; for those with congenital developmental sagittal narrowing of the spinal canal, the prolapsed nucleus pulposus aggravates the degree of stenosis of the spinal canal, so that this symptom is easily induced. (6) Muscle paralysis: paralysis caused by lumbar disc protrusion (prolapse) is very rare, but mostly due to root damage resulting in different degrees of paralysis of the innervated muscles. In mild cases, muscle strength is reduced, and in severe cases, the muscle loses function. Clinically, foot drop caused by the involvement of the anterior tibialis, long and short peroneal muscles, long and long toe extensors and M long extensors innervated by the lumbar 5 spinal nerve is the most common, followed by the quadriceps (innervated by the lumbar 3-4 spinal nerve) and gastrocnemius (innervated by the sacral 1 spinal nerve). (7) Cauda equina symptoms: mainly seen in posterior central type and paracentral type of myelomeningocele (prolapse) syndrome, so it is rare clinically. Its main manifestations are numbness and tingling in the perineum, defecation and urination disorders, impotence (in men), and symptoms of sciatic nerve involvement in both lower extremities. In severe cases, symptoms such as loss of control of urination and defecation and incomplete paralysis of both lower limbs may occur. (8) Lower abdominal pain or anterolateral thigh pain: In high lumbar disc herniation, when the lumbar 2, 3, and 4 nerve roots are involved, there is pain in the inguinal region of the lower abdomen or anteromedial thighs in the area of nerve root innervation. In addition, some patients with low lumbar disc herniation may also have pain in the inguinal region or anterior medial thigh. One third of those with lumbar 3-4 disc herniation have pain in the inguinal region or anterior medial thigh. The rate of occurrence is almost equal in those with disc herniation in the lumbar 4-5 and lumbar 5-sacral 1 intervertebral spaces. This pain is mostly referred pain. (9) Low skin temperature of the affected limb: similar to the cold sensation of the limb, it also reflexively causes sympathetic vasoconstriction due to pain in the affected limb. Or it may provoke the sympathetic nerve fibers in the paravertebral area, causing sciatica and a decrease in skin temperature in the lower legs and toes, especially in the toes. This hypothermia is more pronounced in those with sacral 1 nerve root compression than in those with lumbar 5 nerve root compression. On the contrary, after medullary nucleus removal, feverish sensation occurs in the limbs. (10) Other: depending on the location of the compressed spinal nerve roots, the degree of compression, the extent of involvement of adjacent tissues and other factors, some rare symptoms may appear, such as excessive sweating of the limbs, swelling, sacrococcygeal pain and radiating pain in the knee, etc. (1) General signs: mainly refers to the lumbar and spinal signs, which are common to the disease, including: ① Gait: in the acute stage or when the nerve root is obviously compressed, the patient may have a limp, a hand on the waist or the affected foot is afraid of weight bearing and jumping gait. In mild cases, the gait may be the same as that of a normal person. ②Lumbar spine curvature changes: general cases show the disappearance of the physiological curve of the lumbar spine, flat back or reduced forward convexity. In a few cases, there is even a posterior convexity deformity (mostly in combination with lumbar spinal stenosis). (iii) Scoliosis: This sign is generally present. Depending on the relationship between the site of the herniated nucleus pulposus and the nerve root, the spine may be curved to the healthy side or to the affected side. If the herniated nucleus pulposus is located on the medial side of the spinal nerve root, the lumbar spine bends to the affected side because the spine bends to the affected side to reduce the tension of the spinal nerve root; conversely, if the herniated nucleus pulposus is located on the lateral side of the spinal nerve root, the lumbar spine bends to the healthy side. In fact, this is a general rule, but many factors, including the length of the spinal nerve, the degree of traumatic inflammatory response in the spinal canal, the distance of the protrusion from the spinal nerve root, and various other causes can change the direction of scoliosis. ④ Pressure pain and percussion: The location of pressure pain and percussion pain basically corresponds to the vertebral segment of the lesion and is positive in about 80% to 90% of cases. The percussion pain is obvious at the spinous process and is caused by percussion vibration of the lesion. The pressure point is mainly located at the paravertebral area equivalent to the sacrospinous muscle. Some cases are accompanied by radiating pain in the lower extremities, which is mainly due to the stimulation of the dorsal branch of the spinal nerve root. In addition, percussion on the heels of the feet can also cause conductive pain. In combination with lumbar spinal stenosis, there is also significant pressure pain in the interspinous area. ⑤ Range of lumbar motion: The degree of limitation of lumbar motion varies greatly depending on factors such as whether it is in the acute stage and the duration of the disease. In mild cases, it can be close to normal, but in the acute phase, lumbar movement can be completely restricted, and even refusal to test lumbar mobility. In general, lumbar flexion, rotation and lateral movement are mainly limited; in cases of combined lumbar spinal stenosis, posterior extension is also affected. (6) Muscle strength and atrophy of the lower limbs: depending on the location of the damaged nerve root, the muscles innervated by the nerve root may show muscle weakness and signs of muscle atrophy. In clinical practice, the circumference of the thigh and calf should be measured and the muscle strength of each group of muscles should be tested routinely, and then compared with the healthy side and recorded, and then compared after treatment. (7) Sensory disturbance: The mechanism is the same as the previous one, depending on the location of the affected spinal nerve roots and the abnormal sensation of the innervated area. The positivity rate is more than 80%, and the posterior type is 95%. In the early stages, the symptoms are mostly skin irritation, followed by numbness, tingling and hyperalgesia. The complete loss of sensation is not rare, because the affected nerve roots are unilateral, so the scope of sensory impairment is small; but if the cauda equina is involved (central type and paracentral type), the scope of sensory impairment is more extensive. (8) Reflex changes: This is also one of the typical signs that are prone to occur in this disease. When the lumbar 4 spinal nerve is involved, knee-jerk reflex disorder may occur, which is active in the early stages and then rapidly becomes hyporeflexic, with the latter being more common in clinical practice. Damage to the lumbar 5 spinal nerve has no effect on the reflexes. The Achilles tendon reflex is impaired when the first sacral nerve is involved. Reflex changes are more significant for the localization of the involved nerve. (2) Special signs: Signs obtained through various special examinations. The main ones with greater clinical significance are: ① Flexion neck test (Lindner’s sign): also known as Lindner’s sign. The patient is asked to stand, lie on his back or sit, and the examiner places his hand on top of his head and bends it forward. The test is positive if there is radiating pain in the affected lower extremity, and negative if the opposite is true. The positive rate for the spinal canal type is over 95%. The mechanism is mainly due to the upward displacement of the dura mater with the flexion of the neck, resulting in the pulling of the spinal nerve roots in contact with the protrusion. This test is simple, convenient, and reliable, and is especially suitable for outpatient and emergency care. Straight leg raise test: The patient is placed on his back and the affected knee is raised upward in a straight position. This test has been well accepted since it was first proposed by Forst in 1881. The more inferior the nerve root, the greater the positive detection rate (and the smaller the lift angle). In addition, the larger the protrusion, the more extensive the edema and adhesions at the root cuff, the smaller the lifting angle. In normal conditions, the lower extremity can be lifted above 90, and in older individuals, the angle decreases slightly. Therefore, the smaller the lift angle is, the greater its clinical significance, but it must be compared with the healthy side; in bilateral cases, 60 is generally the dividing line between normal and abnormal. ③Healthy limb elevation test (also known as Fajcrsztajn sign, Bechterew sign, Radzikowski sign): when the healthy limb is elevated straight leg, the nerve root sleeve on the healthy side can pull the dural sac to the distal side, thus causing the nerve root on the affected side to move downward as well. When the herniated disc on the affected side is in the axilla of the nerve root, the nerve root is restricted in its distal movement, causing pain. If the herniated disc is in the shoulder, the test is negative. When the patient is lying on his back during the examination, the presence of sciatica on the affected side is considered positive when the straight leg on the healthy side is elevated. Laseque’s sign: Some people combine this sign with the previous one, while others advocate a separate description. It is positive when the hip and knee are placed in 90° of flexion, and then the knee is straightened to 180°, during which the patient develops posterior radiating pain in the lower limb. The mechanism is mainly due to the stimulation and stretching of the sensitive sciatic nerve during knee extension. ⑤ Straight leg raise test: Also known as Bragard’s sign, this is when the straight leg raise test is performed at a positive angle (based on the patient’s complaints of radiating pain in the limb), and then the affected limb is flexed dorsally to increase the strain on the sciatic nerve. Positive patients complain of increased sciatic nerve radiating pain. The purpose of this test is to exclude the effect of myogenic factors on the straight leg raise test. (6) Supine jerk test: The patient is placed in a supine position and does a jerk of the abdomen and buttocks, so that the buttocks and back leave the bed. At this point, if the patient complains of radiating pain in the sciatic nerve of the affected limb, the test is positive. (7) Femoral nerve pull test: The patient is placed in a prone position with the knee joint of the affected limb fully extended. The examiner elevates the straightened lower limb so that the hip joint is in the hyperextended position, and when the hyperextension reaches a certain level and pain occurs in the femoral nerve distribution area in front of the thigh, it is positive. This test is mainly used to examine patients with herniated discs in lumbar 2 to 3 and lumbar 3 to 4. However, in recent years, it has also been used to detect cases of lumbar 4-5 disc herniation, and its positive rate can be as high as 85% or more. ⑧ Other tests: such as the N nerve or common peroneal nerve compression test, lower limb rotation (internal or external rotation) test, etc., are mainly used for sciatica disorders caused by other causes. The diagnosis of typical cases is usually not difficult, especially with the widespread use of CT and magnetic resonance techniques. However, in atypical cases, or in vertebral or central cases, misdiagnosis is easy and should be prevented.