FUNCTIONAL RESULTS OF SURGICAL TREATMENT OF CERVICAL SPONDYLOTIC MYELOPATHY

Objective: To analyze the functional outcome of surgical treatment of cervical spondylotic myelopathy. Methods: A retrospective study involving 34 patients with CSM, operated from January 2014 to June 2015. The neurological status was assessed using the Nurick and modified Japanese Orthopedic Association (mJOA) scales preoperatively and at 12 months. Sex, age, time of evolution, affected cervical levels, surgical approach and T2-weighted magnetic resonance hyperintense signal were also evaluated. Results: A total of 14 men and 20 women participated. The mean age was 58.12 years. The average progression time was 12.38 months. The preoperative neurological state by mJOA was mild in 2 patients, moderate in 16 and severe in 16, with a mean of 11.44 points. The preoperative Nurick was grade II in 14 patients, grade III in 8, grade IV in 10 and grade V in 2. The T2-weighted hyperintense signal was documented in 18 patients (52.9%). The functional outcome according to the mJOA recovery rate was good in 15 patients (44.1%) and poor in 19 (55.9%). The degree of Nurick recovery was good in 20 (58.8%) and poor in 14 (41.2%). Conclusions: Decompressive surgery of the spinal cord has been shown to be effective in the treatment of cervical spondylotic myelopathy in well-selected patients. Although it is suggested that there are certain factors that correlate with functional outcome, we believe that more prospective randomized studies should be conducted to clarify this hypothesis.


INTRODUCTION
Cervical spondylotic myelopathy (CSM) is the most common form of spinal cord dysfunction in patients aged over 55 years. 1 It may manifest with a wide range of signs and symptoms, such as changes in gait, decreased fine motor ability of the hands, decreased muscle strength, loss of sensitivity, and bladder dysfunction. 2ts clinical course may include periods of remission and periods of progressive neurological deterioriation. 3[10][11] The objective of this study is to evaluate the functional result of surgical treatment of patients with cervical spondylotic myelopathy.

METHODS
A descriptive, longitudinal, observational study was conducted at the Centro Médico ISSEMyM Ecatepec, during the period January 1 to June 16, 2015.A total of 34 patients with cervical spondylotic myelopathy were recruited, who were operated on at the spine surgery service.
For the evaluation of preoperative functional neurological state, the Nurick scale was used, as well as the modified scale of the Japanese Orthopaedic Association (mJOA) by Benzel et al.The postsurgical functional result was evaluated through the Nurick and mJOA scales at 12 months.
The mJOA recovery rate was also defined, using the Hirabayashi method (postsurgical mJOA-presurgical mJOA)/(18-presurgical mJOA) x 100.A satisfactory result was considered as one where the mJOA recovery rate was equal to or greater than 50%, and insufficient if it was less than 50%.Similarly, the result was defined as good if an increase in functional grade on the Nurick scale was produced, and bad if it remained the same or worsened.
Sex, age, duration of the symptoms, levels of compression and hyperintense signal in T2-weighted magnetic resonance imaging were also evaluated.

STATISTICAL ANALYSIS
For the statistical analyses, the software program SPSS, version 23.0 for Windows, was used.The categorical variables were summarized as frequencies and percentages, and the continuous variables as means and standard deviations.The Student's t test was used to compare the quantitative variables, and the Chi Squared test to compare the qualitative variables.
There was a statistically significant relationship between preoperative and postoperative Nurick grades, measured by the Chi Squared x2 (12)=69.94,p=0.000.(Table 3) This functional result following the mJOA recovery rate was good in 15 patients (44.1%) and poor in 19 (55.9%) with a mean recovery of 37.53%.
The functional result, according to the Nurick recovery grade, was good in 20 (58.8%) and poor in 14 (41.2%).There was a correlation between statistically significant functional result according to the Nurick recovery grade and the mJOA functional score, according to the Hirabayashi recovery rate (Table 4).
No statistically significant associations were found between sex (p= 0.119), approach route (p=0.432) and the functional result measured according to the Hirabayashi recovery rate.
There was a statistically significant association between the hyperintense signal in T2 in the magnetic resonance images and the mJOA functional result (p=0.000).(Table 5) There was a statistically significant association between the number of cervical levels affected and the mJOA functional result mJOA (p=0.008).(Table 6) There was a statistically significant association between the preoperative mJOA scale (p=0.000) and the mJOA functional result (Table 7) A statistically significant correlation was found between age and mJOA score at 12 postoperative months; this relationship was inverse moderate linear.rPearson -0.509 (p=0.002).(Table 8 and Figure 1) A statistically significant correlation was found between the preoperative mJOA score and the mJOA score at 12 postoperative months; this relationship was positive linear.rPearson 0.933 (p=0.000).(Table 9 and Figure 2) Finally, there was no statistically significant relationship between time of evolution and final mJOA score.rPearson 0.051 (p=0.774).(Table 10 and Figure 3)

DISCUSSION
The clinical course of cervical spondylotic myelopathy may include periods of inactivity with gradual worsening; 2,12 however, a gradual progression of neurological dysfunction may follow in more constant form. 3,4eing able to predict which patients will have a stable disease and which patients will worsen remains a challenge. 13 Cochrane review of controlled, randomized studies of the role of surgery in patients with cervical spondylotic myelopathy led to the conclusion that the immediate results of the surgery were superior to       conservative management in terms of pain, debility and loss of sensitivity, but no differences were found beyond the first year. 14Another study demonstrated that timely surgical treatment alters the prognosis in patients treated in the first year after the start of symptoms. 15This is consistent with the results of our study, in which we found that there is a statistically significant improvement in patients who received surgical treatment, and that this improvement is positively associated with age and mJOA score at the time of surgery.It was also documented that patients who did not present the hyperintense signal in T2, and those who were affected at 2 levels, had better clinical results.Other factors, such as time of evolution, surgical approach used, and sex, showed no correlation with the postsurgical result.

CONTRIBUTION OF THE AUTHORS:
This manuscript is an institutional study involving five authors.Each author made significant individual contributions to the manuscript.MJVU and AGM were the main contributors to the writing of the manuscript, while AGM, GHH and JEGC performed the surgical interventions, as well as the clinical follow-up, and recruited the patients for the study.VM collected the database and performed the statistical analyses.SH. contributed with the literature review and review of the manuscript.

Figure 3 .
Figure 3. Correlation between time of evolution and postoperative mJOA score.
a.There are multiple modes.The smallest value is shown.

Table 3 .
Correlation between preoperative and postoperative Nurick grades.

Table preoperative Nurick grade vs. postoperative Nurick grade at 12 months Count Postoperative Nurick grade at 12 months
a.In 19 Boxes (95.0%) a count lower than 5 is expected.The minimum expected count is 18.

Table 4 .
Correlation between Nurick recovery grade and Hirabayashi recovery rate.Boxes (0.0%), a count of less than 5 is expected.The minimum expected count is 6.18.b.Only calculated for a 2x2 table.

Table 5 .
Correlation between the hyperintense signal in T2 and the mJOA functional result.

Table 6 .
Correlation between the number of cervical levels affected and the mJOA functional result.

table cervical levels affected vs. mJOA functional result Count mJOA functional result Satisfactory Insufficient Total
. In 3 Boxes (50.0%) a count of less than 5 is expected.The minimum expected count is 2.21 a

Table 7 .
Correlation between preoperative mJOA score and mJOA functional result.

table preoperative mJOA vs. mJOA functional result Count mJOA functional result Satisfactory Insufficient Total
Boxes (33.3%) a count of less than 5 is expected.The minimum expected count is 88.

Table 8 .
Correlation between age and postoperative mJOA score.
*.The correlation is significant at a level of 0.05 (bilateral).

Table 9 .
Correlation between preoperative and postoperative mJOA scores.

Table 10 .
Correlation between time of evolution and postoperative mJOA score.