Craniovertebral Angle and Fibromyalgia Severity

Fibromyalgia (FM) is a chronic pain syndrome characterized by widespread musculoskeletal pain, muscle stiffness, joint rigidity, insomnia, fatigue, mood disorders, cognitive dysfunction, anxiety, depression, and general hypersensitivity.

Fibromyalgia is considered a central sensitivity syndrome. Central sensitization refers to a neuronal signal amplification mechanism within the central nervous system that leads to enhanced pain perception. Consequently, patients with FM exhibit an increased receptive field of pain, allodynia, and hyperalgesia.

Headache and temporomandibular disorders (TMD) are among the most common comorbidities in FM, displaying overlapping clinical and pathophysiological features.

Nociplastic pain is defined by the International Association for the Study of Pain as pain arising from altered nociception despite no clear evidence of actual or threatened tissue damage causing the activation of peripheral nociceptors or evidence for disease or lesion of the somatosensory system causing the pain. The mechanism of nociplastic pain is proposed to involve increased central nervous system sensitization and impaired sensory processing, accompanied by altered pain modulation. Definitive criteria for nociplastic pain have not yet been established. Eight specific disorders associated with central sensitization have been proposed: restless leg syndrome, chronic fatigue syndrome, FM, TMD, migraine or tension-type headache (TTH), irritable bowel syndrome, multiple chemical sensitivities, and whiplash injury.

Central sensitization is classically defined as a consequence of ongoing nociceptive inputs in chronic pain conditions. Its development is reported to be influenced by genetic factors, pain processing disorders in the brain, neuroendocrine and autonomic abnormalities, abnormal cytokines, and immune dysfunction.

As evident, conditions frequently accompanying FM, such as migraine, tension-type headache, chronic fatigue, irritable bowel syndrome, and TMD, share overlapping pathophysiology related to central sensitization.

A bidirectional relationship has been reported between primary headaches and craniocervical postural disorder, defined as Forward Head Posture (FHP). Postural disorders generate nociceptive peripheral stimuli that may lead to sensitization in the trigeminocervical complex.

The trigeminocervical complex (TCC), located in the brainstem, is a common convergence pathway where both trigeminal (dural) and cervical (primarily via the greater occipital nerve) afferent inputs are projected to higher centers in the thalamus and cortex. The TCC serves as the first sensory relay for meningeal and cephalic cutaneous information and forms the pathways for referred pain in primary headaches.

Brainstem interneurons have been shown to play a key role in pain modulation in migraine, TTH, and cluster headaches. Primary headache has been determined to result from trigeminocervical complex dysfunction. Neurophysiological studies on trigeminal reflexes support the concept of primary brainstem dysfunction and central hyperexcitability of trigeminal sensory pathways in chronic pain syndromes such as FM and TTH.

Similarly, animal studies in FM have identified a hyperalgesic state in the trigeminal region.

Sensitization in the trigeminocervical complex can lead to central sensitization by increasing thalamic and cortical stimulation. Peripheral and central sensitization are characterized by widespread hyperalgesia and allodynia. Consequently, patients with chronic primary headache exhibit a larger pain distribution area not only in the craniocervical region but throughout the entire spine.

The relationship between TCC sensitization and pain disorders has been well-documented in human and animal studies. Significant abnormalities in TCC responses have been observed in patients with trigeminal neuralgia, migraine, cluster headache, chronic tension-type headache, and fibromyalgia, attributed to hyperexcitability of trigeminal pathways.

Similarly, TMD, another comorbidity accompanying FM, frequently co-occurs with primary headaches, and the trigeminal system is reported to be the common pathophysiological mechanism.

Forward Head Posture (FHP) refers to the anterior displacement of the head relative to the trunk through upper cervical extension and lower cervical flexion. A craniovertebral angle (CVA) of 49° or less is defined as FHP.

FHP, characterized by forward head projection and rounded shoulders, is a common consequence of modern lifestyles involving prolonged use of laptops, mobile devices, or driving. It leads to persistent headache and is associated with migraine, TTH, and cervicogenic headaches.

The relationship between TMD and FHP is well-established. Forward head posture leads to TMD.

In the pathophysiology of primary headaches and TMD, which frequently accompany FM, the trigeminocervical complex emerges as a factor increasing central sensitization. FHP is reported to be a postural factor contributing to this. Central sensitization also plays a primary role in FM pathophysiology.

Postural studies in FM have reported increased thoracic kyphosis, lower CVA, and impaired cervical joint position sense.

To our knowledge, there are no studies examining the relationship between craniovertebral angle and disease severity in FM. We hypothesize that FHP may play a significant role in central sensitization in FM patients through the trigeminocervical complex, similar to its role in headaches and TMD. Therefore, we aim to investigate the frequency of FHP in FM patients and its relationship with FM disease severity.

Inclusion criteria

• Aged 18-55 years
• Diagnosed with Fibromyalgia (FM) according to The American College of Rheumatology (ACR) 2010 Diagnostic Criteria for Fibromyalgia

Exclusion criteria

• History of past or current pathology in the cervical spine, thoracic spine, or upper extremities
• History of paraspinal or thoracic surgery involving the head, spine, or shoulders within the last six months
• Structural spinal malformation
• History of surgical or neurological disorders
• Cervical trauma or pain treatment within the last 6 months
• Temporomandibular surgery
• Psychiatric disorders (e.g., dementia, amnesia, or delirium)
• Systemic inflammatory rheumatic diseases