Letter to the Editor Regarding the Central Sensitisation Inventory and Central Sensitisation

We have recently read the paper by Seweryn et al. [1] regarding the assessment of central sensitization, anxiety and depression in patients with chronic masticatory muscle pain. The authors concluded that their findings ‘may suggest that central sensitisation is more closely linked to depression and anxiety than to masticatory muscle pain’ [1]. Given this, we wish to address a critical methodological point regarding the assessment of central sensitization (CS). More specifically, the practice of using the Central Sensitization Inventory (CSI) as a surrogate of CS in humans which risks conflating a neurophysiological phenomenon with a self-reported clinical profile [2, 3]. Precision in distinguishing between the physiological underpinnings of CS and the symptoms captured by the CSI is crucial for accurate scientific interpretation and effective progress towards precision pain management.

Since its original proposition in the late 80's, CS remains fundamentally a neurophysiological phenomenon, defined by the International Association for the Study of Pain (IASP) as ‘increased responsiveness of nociceptive neurons in the central nervous system to their normal or subthreshold afferent input’. Because directly assessing CS in humans remains a challenge [4], terms such as central sensitivity syndromes, human-assumed central sensitisation and even the concept of nociplastic pain have been used in order to establish a clinical profile assumed to be the manifestation of CS. This highlights a crucial distinction: CS is best conceptualised as a physiological state, not a perceptual one and relying on subjective questionnaires to assess CS risks that the term broadens beyond its neurophysiological meaning to include psychological and symptomatic profiles, potentially misguiding research. Therefore, although we acknowledge the expansion in the definitions, interpretations and applications of CS, specially to patients with chronic pain, we also believe that such widening of scope can cause more confusion than clarification.

The authors highlighted the absence of quantitative sensory testing as a potential study limitation. In this regard, a systematic review by Adams et al. and a recent original research study by Salbego et al. in patients with chronic masticatory muscle pain reported that the CSI is strongly associated with psychological constructs, such as depression, anxiety and pain catastrophizing, but showed weak or no association with psychophysical measures of nociceptive sensitivity [3, 5]. However, another systematic review by Neblett et al. [2] reported that the CSI is significantly correlated with pain thresholds. Importantly, the traditional manner by which psychophysical assessment of the somatosensory function has been done does not seem to be sufficient to identify CS [4].

The imprecise use of CS based on CSI scores risks misinterpreting pain mechanisms in pain conditions. For instance, if high CSI scores primarily reflect psychological distress and symptom burden, rather than specific neurophysiological changes within the central nervous system (CNS), then treatment strategies might be misdirected. For example, interventions targeting CNS modulation may be prioritised over more appropriate psychological or behavioural therapies. Likewise, there may be cases where peripheral inputs are the main drivers of pain, in which case it may be therapeutically more appropriate to address them.

It is thus crucial to distinguish between CS as a neurophysiological process, from the unspecific clinical presentation assumed to be related to the presence of CS. The authors rightfully state that ‘Despite a growing body of literature on this topic, the mechanisms of CS are insufficiently understood’ [1]. We fully agree with that and believe that the way forward involves increasing the awareness of the many uses and misuses of the term CS and encourage researchers to work with more specific definitions and more precise assumptions.

Given this, we respectfully urge the Journal of Oral Rehabilitation and its contributors to maintain a clear distinction between the physiological concept of CS and a clinical construct measured by questionnaires like the CSI. Scientific precision in definitions and measurement is vital for accurate research, valid conclusions and the development of truly effective, mechanism-based interventions for painful TMDs and chronic pain.

The authors declare no conflicts of interest.

The authors have nothing to report.

The peer review history for this article is available at https://www.webofscience.com/api/gateway/wos/peer-review/10.1111/joor.70053.