In this study, we surveyed surgical cases of cervical myelopathy using the SQC, a newly developed self-administered questionnaire for the screening of cervical myelopathy, to investigate its sensitivity and to examine and characterize false-negative cases.
Patients with cervical myelopathy exhibit various symptoms, such as numbness, pain, hypesthesia, weakness of the extremities, pain and stiffness of the neck, manual clumsiness, walking disturbance, and urinary disturbance8,9). The prevalence is not very low and is estimated to increase with the aging of a society10,11).
Many sources of information must be examined to reach an accurate diagnosis, such as the case history, physical examination (including neurological examination), and imaging tests.
Generally, numbness of the upper extremities is one of the chief symptoms of cervical myelopathy. Patients with cervical myelopathy who show this numbness frequently consult a general outpatient clinic or primary care practitioner. However, accurate diagnosis is not always easy because numbness of the upper extremities may also result from entrapment neuropathies such as carpal or cubital tunnel syndromes.
On the other hand, misdiagnosis and delayed treatment of cervical myelopathy can result in irreversible consequences, such as paralysis, urinary disturbance, and walking disturbance1). Accurate diagnosis and early treatment by a specialist are therefore central to a good outcome.
We recently developed a brief, self-administered screening questionnaire for cervical myelopathy, the SQC2). This tool offers a high sensitivity of 93.5% and a specificity of 67.3%. We emphasized sensitivity, as this questionnaire is designed to screen for cervical myelopathy. Patients could quickly complete the questionnaire while waiting for primary care. Also, it is possible that they could answer the SQC as part of self-regulation at home.
The present study investigated the utility of the SQC by calculating the sensitivity and also compared several items between positive and negative groups to clarify the characteristics of patients showing a false negative result on the SQC. We found that JOA scores were significantly higher in the negative group.
Interestingly, most patients in the negative group (11/13, 84.6%) showed a JOA score ≥12 (Figure 2). This result corresponds with the fact that a JOA score ≥12 indicates a mild case of cervical myelopathy12). Similarly, results for grip strength and the 10-s test were superior in the negative group. These results mean that patients with mild cervical myelopathy can present false-negative results in this questionnaire. Since the purpose of screening with SQC is to narrow down the list of cervical myelopathy patients in primary care, it is thought that a certain number of false negatives will inevitably occur. In order to reduce the number of false positives, repeated evaluation by SQC for cases of suspected mild cervical myelopathy could be considered as a useful option.
Several limitations must be considered in this study. First, this self-administered questionnaire was developed based on a case-control study of patients treated surgically and patients with peripheral nerve entrapment such as carpal tunnel syndrome. Healthy volunteers were not included in the development of SQC. However, the median score of healthy volunteers in SQC is available from the past report showing the median JOACMEQ score of healthy volunteers13) because SQC consists of items of JOACMEQ, which suggests that the result of SQC in healthy volunteers should be negative. Secondly, all participants in this study were patients who were treated surgically. We consider that this questionnaire might be beneficial in primary care situations to screen for cervical myelopathy requiring surgical intervention. Further studies that include patients who were treated conservatively would be needed in the future. Finally, this SQC does not contain the item which asks about hand clumsiness and muscle weakness of hands. Therefore, complementary tests such as the grip and release test would be needed additionally for more sensitive screening. As a result, clinicians should use this questionnaire with caution.
In conclusion, the SQC showed a high sensitivity of 89.9%. Clinicians need to be aware that the SQC may show false-negative results for patients with mild cervical myelopathy.
Fig. 2. Distribution of Japanese Orthopaedic Association (JOA) scores
SQC: Self-administered questionnaire to screen patients for cervical myelopathy