Motor unit number index (MUNIX) in the quantitative assessment of severity and surgical outcome in cervical spondylotic amyotrophy

Analysis of surgical treatment of cervical spondylotic amyotrophy

Background

Cervical spondylotic amyotrophy (CSA) is a special type of cervical spondylosis based on cervical degeneration, which is mainly manifested by weakness and atrophy of upper limb muscles without obvious sensory impairment. Various diagnostic and treatment strategies used; however, discrepancies exist. We tried to discuss diagnosing and treating CSA.

Methods

15 patients with CSA were diagnosed in the Orthopedics Department of the First Affiliated Hospital of Zhengzhou University, aged 42-70 years old. The duration of preoperative symptoms of amyotrophy was 6 to 240 months. 12 patients received surgical treatment, and 3 patients received conservative treatment. The patients were divided into two groups according to the site of preoperative amyotrophy. The manual muscle test was used to evaluate the patients' muscle strength pre-and postoperatively.

Results

During postoperative follow-up, the muscle strength of 12 patients improved to different degrees compared to before surgery. The improvement effect was excellent in 2 cases, good in 6, and moderate in 4. There was no decrease in postoperative muscle strength compared with that before surgery. The satisfaction rate of the effect was 66.7%. The two groups had no statistically significant difference in preoperative muscle strength. The postoperative muscle strength of the proximal group was significantly better than that of the distal group.

Conclusion

The surgical effect of CSA of the proximal type is significantly better than that of the distal type. The recovery effect of amyotrophy after surgery for distal type CSA is poor; thus, surgical treatment should be carefully considered.

Quantitative assessment of motor impairment and surgical outcome in Hirayama disease with proximal involvement using motor unit number index

OBJECTIVE

To assess the feasibility of motor unit number index (MUNIX) in quantitatively evaluating Hirayama disease (HD) with proximal involvement and to identify the effectiveness of anterior cervical fusion (ACF) in treating atypical HD with proximal involvement.

METHODS

This study included 28 atypical HD patients with proximal involvement (proximal-distal vs. distal-proximal groups: 5 vs. 23) and 41 healthy controls. All patients underwent pre- and postoperative 1-year MUNIX tests on abductor pollicis brevis (APB), abductor digiti minimi (ADM), biceps brachii (BB) and deltoid (Del). The disabilities of arm, shoulder and hand (DASH) and Medical Research Council (MRC) scales were also performed in these patients before and one year after operation.

RESULTS

Preoperatively, the patients in the distal-proximal group showed reduced compound muscle action potential (CMAP), decreased MUNIX and increased motor unit size index (MUSIX) in bilateral distal muscles and symptomatic-side proximal muscles (P < 0.05), and similar abnormalities were also observed in ADM, BB and Del on the symptomatic side in the proximal-distal groups (P < 0.05). Postoperative follow-up analysis identified increased MUNIX in the symptomatic-side proximal muscles with improved motor function in the proximal-distal groups (P < 0.05), and distal-proximal group patients showed an increase in both CMAP and MUSIX in the symptomatic-side proximal muscles (P < 0.05).

CONCLUSIONS

MUNIX may serve as an available supplementary test to quantitatively evaluate the motor dysfunction and treatment outcome in HD with proximal involvement. ACF procedures can effectively treat these atypical HD patients, especially for those whose symptoms started in proximal muscles.

Motor unit number index detects the effectiveness of surgical treatment in improving distal motor neuron loss in patients with incomplete cervical spinal cord injury

BACKGROUND

Recovery of motor dysfunction is important for patients with incomplete cervical spinal cord injury (SCI). To enhance the recovery of muscle strength, both research and treatments mainly focus on injury of upper motor neurons at the direct injury site. However, accumulating evidences have suggested that SCI has a downstream effect on the peripheral nervous system, which may contribute to the poor improvement of the muscle strength after operation. The aim of this study is to investigate the impact of early vs. delayed surgical intervention on the lower motor neurons (LMNs) distal to the injury site in patients with incomplete cervical SCI.

METHODS

Motor unit number index (MUNIX) was performed on the tibialis anterior (TA), extensor digitorum brevis (EDB) and abductor hallucis (AH) in 47 patients with incomplete cervical SCI (early vs. delayed surgical-treatment: 17 vs. 30) and 34 healthy subjects approximately 12 months after operation. All patients were further assessed by American spinal injury association (ASIA) motor scales and Medical Research Council (MRC) scales.

RESULTS

There are no difference of both ASIA motor scores and MRC scales between the patients who accepted early and delayed surgical treatment (P > 0.05). In contrast, the patients undergoing early surgical treatment showed lower MUSIX values in both bilateral EDB and bilateral TA, along with greater MUNIX values in both right-side EDB and right-side TA, compared to the patients who accepted delayed surgical treatment (P < 0.05).

CONCLUSIONS

Cervical SCI has a negative effect on the LMNs distal to the injury site. Early surgical intervention in Cervical SCI patients may improve the dysfunction of LMNs distal to the injury site, reducing secondary motor neuron loss, and eventually improving clinical prognosis.