With prevalence estimates ranging from 0.17 to 4.1% in the general population , cervicogenic headache (CGH) is defined as a secondary headache (HA) resulting from a disorder involving any bony of soft-tissue structure of the neck  and represents between 15 and 20% of all chronic HAs . Although the exact underlying mechanisms are not fully understood, evidence shows that CGH could arise from the C1-C2 zygapophyseal joints . As a result, one of the main clinical features of CGH is the loss of mobility during active cervical range of motion (ROM) and hypomobility of the upper cervical spine . This clinical feature is used as a diagnostic criterion by the Cervicogenic Headache International Study Group (CHISG) .
Movement deficits specific to the upper cervical spine can be assessed using the cervical flexion-rotation test (CFRT) , a test that can isolate the rotation movement of the upper cervical spine. Magnetic resonance imaging made it possible to document that a 45o rotation on both side is considered as “normal” range of motion during the CFRT .
As the CFRT demonstrated good validity in the assessment of upper cervical spine mobility deficits , it can be used to support the diagnosis of C1-C2 related CGH. However, as the CFRT informs about movement impairment (versus pain provocation), could it be useful for other purposes, such as treatment guidance, particularly for physical rehabilitation approaches? Yet, before answering this question, we would like to point out two issues associated to the CFRT, one related to the procedures (cut-off) and the second one related to its diagnostic accuracy. Some potential solutions are also proposed and discussed.
Issue n°1: the precision of the cut-off for positive response
The CFRT test is considered positive only when movement restrictions are present. However, there are inconsistencies in the cut-off (ROM) to rule on this movement restriction. Yet, significant confounding factors may increase the risk of bias or misinterpretation of CFRT.
1) Influence of pain: performing the CFRT during a painful HA episode might alter the movement response, as pain can clearly inhibit or limit ROM.
2) Age: it was established that CFRT range of motion decreases with age, as 27.9% of the variance of the CFRT could be explained by age alone .
3) Assessment tool: Although eyeball estimation of cervical rotation movement makes the CFRT very “clinician-friendly”, it has measurement errors that might greatly affect the interpretation of the test .
4) Misdiagnosis: Positive CFRT could be found in migraine population. Moreover, chronicization of symptoms increases the rate of positive CFRT in this population. This can lead to misdiagnosis .
Markedly, these confounding factors could affect the cut-off’s accuracy and is likely to overestimate the diagnosis properties of CFRT.
Potential solutions to reduce the influence of these confounding factors include:
1) Promote the use of appropriate measurement devices to enhance measurement precision
We believe that using a valid instrument to measure neck rotation during the CFRT may (i) increase the inherent validity and reliability of the test, (ii) help clinicians to detect more subtle loss of movement and (iii) bring clinically relevant information, to assist the diagnosis and to monitor significant improvements in range of motion following an intervention. Different devices measuring neck range of motion have been validated in previous studies and could be used to measure cervical range of motion while performing the CFRT. These instruments include the CROM device, smartphones applications and, more recently, the EasyAngle (Meloq AB, Stockholm, Sweden) digital goniometer, which have been used to measure ROM during the CFRT . Clearly, the use of a validated tool is essential to minimize measurement error.
2) Consider integrating the symptomatic response to the decision process
As pain is the main symptom of CGH, where the HA can be caused by an impairment of C1/C2 zygapophysial joints, it would be reasonable to assume that the CFRT should reproduce the patient’s typical symptoms (headache). Yet, we found that the reproduction of the patient’s typical pain was used in only one study . The addition of this criteria to the decision process may increase the accuracy of CFRT.