Inclusion criteria: Upper limb amyotrophy; No obvious sensory disturbance; Complete preoperative imaging examination [including cervical x-ray, computed tomography (CT), magnetic resonance imaging (MRI), and electromyogram (EMG)]; Complete regular outpatient follow-up.

Exclusion criteria: Motor neuron disease; Hirayama disease; Amyotrophic lateral sclerosis; Shoulder sleeve injury; Lost to follow-up.

From March 2021 to June 2022, 15 patients were admitted to the Department of Orthopedics of the First Affiliated Hospital of Zhengzhou University and diagnosed with CSA, including 7 males and 8 females, aged from 42 to 70 years (average 55.1 years). The duration of preoperative amyotrophy symptoms was 6 to 240 months (average 63.6 months). The patients were divided into two groups according to the site of preoperative amyotrophy: Proximal type group, 6 cases in total; Distal type group, 6 cases in total; Another 3 cases were treated conservatively. There was no statistical significance between the two groups in age, course of the disease, and follow-up time after surgery, as shown in Table 1.

When patients receive conservative treatment for at least one month which is ineffective in the end, the patients shall be treated with anterior cervical decompression and fusion or posterior cervical laminoplasty according to the compression position of the lesion, the number of the lesion segments, the curvature of the cervical spine. The principle is to relieve the compression of nerve root and spinal cord and reconstruct the physiological curvature of cervical spine.

All patients were followed up at postoperative 3, 6, and 12 months and every year after that. The follow-up aimed to evaluate the recovery of muscle strength compared with before surgery, the improvement of amyotrophy after surgery, and conduct imaging review.

The muscle strength level is divided into 6 levels: 0, 1, 2, 3, 4, and 5. The muscle strength level of 5 is normal. The muscle strength of patients before and during the follow-up was evaluated by Manual Muscle Testing (MMT), which is based on the function of the subject's muscles or muscle groups, placing the patient in different examination positions, instructing the patient to perform certain movements in a state of anti-gravity, or resistance, and achieving the maximum range of motion, which then were divided into four groups (“excellent”, “good”, “moderate”, and “bad”). It is “excellent” that the muscle strength improve by ≥2 grades than that before operation or to restore the muscle strength to the normal level after operation. The muscle strength at follow-up was better than that before operation; It is “good” that the muscle strength improve by >1 grades than that before operation; It is “moderate” that the muscle strength has no obvious improvement compared with that before operation; It is “bad” that the muscle strength decrease compared with preoperative. At the follow-up, the “excellent” or “good” group were defined as satisfactory efficacy.

The data were analyzed by SPSS (version 26.0) statistical software. The measurement data were expressed by mean ± standard deviation (X ± S), and the independent sample t-test was used to compare the two groups. The data that did not meet the normal distribution conditions were analyzed using Mann–Whitney Testing. P < 0.05 is statistically significant.

CSA is rare in clinic, and its pathogenesis is not very clear. According to domestic and foreign literature reports, CSA may have the following types: Selective ventral spinal cord nerve root (VNR) injury: Keegan et al. believe that anterior spinal root compression is one of the important mechanisms of the disease (2); Anterior horn (AH) cell injury of spinal cord: It is reported in the literature that there is symmetrical high signal in the AH area on the MRI T2 image of some patients with CSA, which is called “snake eye sign” (7); Anterior spinal artery (ASA) blood supply insufficiency: AH mainly receives the blood supply from the terminal branch of the anterior spinal artery. On the basis of cervical degeneration, cervical instability, and cervical spinal stenosis, cervical flexion and extension activities will cause compression or traction of blood vessels inside and outside the spinal cord, thus affecting the blood supply in the spinal cord (8). The blockage of ASA blood flow causes insufficient AH perfusion in multiple segments, which is considered to be one of the pathogenesis of CSA (9); Both VNR and AH are involved: Imajo believes that the herniated intervertebral disc or osteophyte at the posterior edge of the vertebral body can cause VNR and AH to be involved at the same time (10). Most of the patients in our research group conformed to the above view, and 5 patients had “snake eye sign” on imaging. In addition, the incidence rate of CSA is not significantly related to the degree of cervical degeneration (11).

Diagnostic criteria: Patients with cervical spondylosis or previous history of cervical spondylosis, unilateral and a few bilateral upper limb amyotrophy, and the muscle strength of the affected limb has been weakened to a certain extent, without lower limb sensory disturbance; With or without upper limb root pain, sensory disturbance and positive pathological signs; Compression segment MRI T2WI weighted image with or without high signal of spinal cord; Neuroelectrophysiological examination was consistent with cervical spondylosis of amyotrophic type; Motor neuron disease, Hirayama disease and peripheral neuropathy (such as cubital tunnel syndrome) were excluded (12).

Motor neuron disease is the most critical disease to differentiate from CSA, and amyotrophic lateral sclerosis (ALS) is the most common one (13). The main clinical manifestations are progressive aggravation of skeletal muscle weakness, atrophy, muscle bundle fibrillation, bulbar paralysis and pyramidal bundle sign, which are common in the elderly. Neuroelectrophysiological examination is very important in the differential diagnosis of the two. Repetitive nerve stimulation is mainly used to evaluate the electrophysiological test of neuromuscular junction function, which has more obvious changes in the detection of ALS patients (14). EMG can identify the cause of muscular atrophy and determine the part and degree of nerve damage. The involvement of sternocleidomastoid muscle (accessory nerve innervation) on EMG is the most important identification point between CSA and ALS (15). If it is difficult to distinguish motor neuron disease from CSA, surgery should not be performed, because surgery may aggravate the condition of motor neuron disease.

Hirayama disease, also known as atrophy of the distal part of the upper limb in young people, occurs in adolescence and is mainly male. Its clinical features include major unilateral muscle weakness and atrophy of the hand and forearm. The onset of the disease is concealed, the progress is slow, and it often recovers within a few years. Cervical magnetic resonance imaging and neuroelectrophysiological examination are helpful to differentiate Hirayama disease from CSA, and the age of onset is also one of the differences between the two (16). In addition, CSA should be differentiated from cubital tunnel syndrome and rotator cuff disease (3).

At present, there is no gold standard for the treatment of CSA. Conservative treatment is the early intervention for CSA by most clinicians, especially in the early stage of the disease, including traction, neck support fixation, hyperbaric oxygen, and taking vitamin B12 or vitamin E has also proved effective for some patients (17). Therefore, most clinicians suggest that conservative treatment should be taken as the initial treatment of CSA, especially those with the following related factors: age < 50 years old, duration of symptoms < 6 months, single-segment spinal canal stenosis, intervertebral foramen stenosis and patients who are effective for traction treatment (18).

Moreover, there is no consensus on the timing and mode of CSA surgery. Most scholars believe that once CSA is confirmed, surgical treatment can at least prevent the further development of the disease, even if it cannot effectively improve the symptoms of patients. Tauchi suggested that surgical treatment should be considered if the effect of conservative treatment is not good after 4 months of CSA symptoms. The decrease of the amplitude of the action potential of the compound muscle of the deltoid and biceps to 30%–50% of the contralateral side is also considered as the indication of surgical treatment (19).

There is no unified understanding of the choice of surgical methods. Both anterior cervical decompression and fusion and simple posterior laminoplasty have been reported in CSA (20). Uchida K believes that anterior cervical decompression and fusion is effective for most patients with CSA (6). Inui believes that posterior treatment is recommended when the segment is more than 2 with spinal canal stenosis (7).

In this study, there was no significant improvement in the symptoms of 3 patients with conservative treatment during the follow-up. The muscle strength of 12 patients was improved compared with that before operation, of which 2 cases were excellent, 6 cases were good, and 4 cases were moderate. The satisfactory rate of curative effect was 66.7% (8/12), there were 5 cases of proximal type and 3 cases of distal type. Our treatment group agreed that surgical treatment had a certain effect on patients with CSA. It is suggested that the surgical treatment of proximal CSA should be more active than that of distal CSA. Of the 12 patients in this study, 8 were treated with ACDF and 4 with LP. Most of the patients' condition improved compared with that before surgery. From the perspective of pathogenic factors, spinal cord or nerve compression is the main pathogenesis, and the main goal of surgery should be decompression (21).

Our study is a retrospective study with a short follow-up time and a small sample size, which requires a large sample of multi-center prospective further research. To sum up, the surgical effect of proximal CSA is significantly better than that of distal CSA. The proximal CSA with severe compression should be actively treated with surgery. The recovery effect of amyotrophy after distal CSA is poor. Whether to choose surgical treatment remains to be explored by spine orthopedic doctors all over the world.