Impaired postural control in patients with cervico-brachial pain

The effect of neck-specific exercise and prescribed physical activity on headache and dizziness in individuals with cervical radiculopathy: Further analyses of a randomized study with a 1-year follow-up

OBJECTIVE

To evaluate the effect of neck-specific exercise (NSE) compared to prescribed physical activity (PPA) on headache and dizziness in individuals with cervical radiculopathy (CR). Also, to investigate associations between headache or dizziness and pain, neck muscle endurance (NME), neck mobility, physical activity, and fear avoidance beliefs.

METHODS

Individuals randomized to either NSE or PPA were selected to a headache subgroup (n = 59) and/or a dizziness subgroup (n = 73). Data were evaluated, according to headache and/or dizziness outcomes at baseline and at 3, 6, and 12-month follow-ups.

RESULTS

No significant between-group differences were found between NSE and PPA in either subgroup. In the headache subgroup, significant within-group improvements were seen at all follow-ups for NSE (p < .001) and from baseline to 3 (p = .037) and 12 (p = .003) months for PPA. For dizziness, significant within-group improvements were seen from baseline to 3 months for NSE (p = .021) and from baseline to 3 (p = .001) and 6 (p = .044) months for PPA. Multiple regression models showed significant associations at baseline between headache intensity and neck pain (adjusted R-square = 0.35, p < .001), and for dizziness with neck pain and dorsal NME (adjusted R-square = 0.34, p < .001).

CONCLUSION

NSE and PPA show similar improvements in headache intensity and dizziness in individuals with CR. Headache intensity is associated with neck pain, and dizziness with neck pain and dorsal NME, highlighting the importance of these factors when evaluating headache and dizziness.

Patient-Reported Outcome Measures following Coblation Nucleoplasty for Cervical Discogenic Dizziness

BACKGROUND

There is little research in the literature comparing the efficacy of coblation nucleoplasty with conservative treatment in the treatment of cervical discogenic dizziness and reporting the achieved rate of minimal clinically important differences (MCID) and patient acceptable symptom state (PASS) after surgery. This retrospective study aims to explore the patient-reported outcome measures (PROM) following coblation nucleoplasty for cervical discogenic dizziness and to compare the therapeutic effect of coblation nucleoplasty with prolonged conservative treatment.

METHODS

Sixty-one patients with cervical discogenic dizziness and a positive intradiscal diagnostic test eligible for single-level cervical coblation nucleoplasty were included in the study. Among these 61 patients, 40 patients underwent cervical coblation nucleoplasty, while the remaining 21 patients refused surgery and received continued conservative treatment. The primary PROMs were the intensity and frequency of dizziness and secondary PROMs were related to the neck disability index (NDI) and visual analog scale (VAS) for neck pain (VAS-neck) during a 12-month follow-up period. Moreover, the achieved rate of MCID and PASS in both groups was assessed 12 months after surgery.

RESULTS

Dizziness intensity, dizziness frequency, VAS-neck score, and NDI score were significantly improved from the baseline at all follow-up time points in both treatment groups, except for showing no significant improvement in dizziness frequency in the conservative treatment group at 6 and 12 months after surgery. However, at each follow-up time point, the above indexes were lower in the surgery group than in the conservative treatment group. In addition, the achieved rates for PASS and MCID in all indexes in the surgery group were significantly higher than those in the conservative treatment group at 12 months after surgery.

CONCLUSIONS

Cervical coblation nucleoplasty significantly improved the intensity and frequency of dizziness, neck pain, and NDI in patients with cervical discogenic dizziness, and the results were superior to those from prolonged conservative treatment. Meanwhile, cervical coblation nucleoplasty is a good choice for patients with chronic neck pain and refractory cervical discogenic dizziness who have not demonstrated the indications for open surgery and have not responded well to conservative treatment.

Cervicogenic dizziness alleviation after coblation discoplasty: a retrospective study

OBJECTIVE

Little is known about the therapeutic relationship between coblation discoplasty and cervicogenic dizziness (CGD). CGD can be caused by abnormal proprioceptive inputs from compressed nerve roots, intradiscal mechanoreceptors and nociceptors to the vestibulospinal nucleus in the degenerative cervical disc. The aim was to analyze the efficacy of coblation discoplasty in CGD through intradiscal nerve ablation and disc decompression in a 12-month follow-up retrospective study.

METHODS

From 2015 to 2019, 42 CGD patients who received coblation discolplasty were recruited as the surgery group, and 22 CGD patients who rejected surgery were recruited as the conservative group. Using intent-to-treat (ITT) analysis, we retrospectively analyzed the CGD visual analogue scale (VAS), neck pain VAS, CGD frequency score, and the CGD alleviation rating throughout a 12-month follow-up period.

RESULTS

Compared with conservative intervention, coblation discoplasty revealed a better recovery trend with effect sizes of 1.76, 2.15, 0.92, 0.78 and 0.81 in CGD VAS, and effect sizes of 1.32, 1.54, 0.93, 0.86 and 0.76in neck pain VAS at post-operative 1 week, and 1, 3, 6, 12 months, respectively. The lower CGD frequency score indicated fewer attacks of dizziness until postoperative 3 months (p < 0.01). At post-operative 12 months, the coblation procedure showed increased satisfactory outcomes of CGD alleviation rating (p < .001, -1.00 of effect size).

CONCLUSIONS

Coblation discoplasty significantly improves the severity and frequency of CGD, which is important inbridging unresponsive conservative intervention and open surgery.Key messagesThere is a correlation between the degenerative cervical disc and cervicogenic dizziness (CGD).CGD can be caused by abnormal proprioceptive inputs from a compressed nerve root and intradiscal mechanoreceptors and nociceptors to the vestibulospinal nucleus in the degenerative cervical disc.Cervical coblation discoplasty can alleviate CGD through ablating intradiscal nerve endings and decompressing the nerve root.

Comparison and Association of Neck Extensor Muscles’ Endurance and Postural Function in Subjects with and without Chronic Neck Pain – A Cross-Sectional Study

Purpose Neck extensor endurance (NEE) and position sense are vital for maintaining cervical spine function and defects in these processes may be associated with impaired postural control in chronic neck pain (CNP) subjects. The study’s objectives are 1) to compare the cervical extensor endurance capability and postural control of CNP subjects with those of asymptomatic controls; 2) to investigate the association between NEE and postural control.

Materials and Methods Sixty-four participants (38 asymptomatic, 38 with CNP) participated in this cross-sectional study. NEE was assessed using a clinical extensor endurance test. Under open and closed eyes conditions, postural control measures were tested with the Good Balance system. The postural control parameters were AP-velocity (mm/s), ML-velocity (mm/s) and Velocity moment (mm2). NEE capacity and postural control parameters were compared and correlated between asymptomatic and CNP subjects.

Results and Discussion CNP subjects showed lower NEE capacity (p<0.001) and significantly larger AP-velocity (p<0.001), ML-velocity (p<0.001) and Velocity moment (p<0.001) than asymptomatic participants. NEE negatively correlated with AP-velocity (r=−0.51, p=0.001), ML-velocity (r=0.46, p=0.003) and velocity moment (r=0.38, p=0.020) in asymptomatic subjects in eyes open condition and no correlations in subjects with CNP. CNP subjects showed increased postural sway velocities and lowered extensor endurance capacity compared to asymptomatic participants. No correlations existed between NEE and postural control parameters in CNP subjects.

Cervical intervertebral disc degeneration and dizziness

Clinical studies have found that patients withcervical degenerative disease are usually accompanied by dizziness. Anterior cervical surgery can eliminate not only chronic neck pain, cervical radiculopathy or myelopathy, but also dizziness. Immunohistochemical studies show that a large number of mechanoreceptors, especially Ruffini corpuscles, are present in degenerated cervical discs. The available evidence suggests a key role of Ruffini corpuscles in the pathogenesis of dizziness caused by cervical degenerative disease (i.e. cervical discogenic dizziness). Disc degeneration is characterized by an elevation of inflammatory cytokines, which stimulates the mechanoreceptors in degenerated discs and results in peripheral sensitization. Abnormal cervical proprioceptive inputs from the mechanoreceptors are transmitted to the central nervous system, resulting in sensory mismatches with vestibular and visual information and leads to dizziness. In addition, neck pain caused by cervical disc degeneration can play a key role in cervical discogenic dizziness by increasing the sensitivity of muscle spindles. Like cervical discogenic pain, the diagnosis of cervical discogenic dizziness can be challenging and can be made only after other potential causes of dizziness have been ruled out. Conservative treatment is effective for the majority of patients. Existing basic and clinical studies have shown that cervical intervertebral disc degeneration can lead to dizziness.

Does the C3/4 disc play a role in cervical spondylosis with dizziness? A retrospective study

PURPOSE

To investigate the effect of C3/4 disc degeneration on cervical spondylosis with dizziness (CSD) and to assess the curative effect of anterior cervical decompression and fusion (ACDF) in patients with CSD.

METHOD

Four hundred nineteen patients who underwent ACDF for treatment of myelopathy or radiculopathy were divided into dizziness and non-dizziness group. The visual analog scale (VAS) score and Japanese Orthopaedic Association (JOA) score were used to determine the intensity of dizziness and neurological symptoms, respectively. Cervical disc degeneration was evaluated using Miyazaki's classification system. Some parameters were measured using cervical radiographs. The surgical effects on CSD were compared between surgery with and without C3/4 level. Multivariate logistic regression analysis was used to determine the risk factors for CSD.

RESULTS

The pre-operative incidence of CSD was 33.9%. Women were more likely to develop dizziness than men (p < 0.05), CSD was significantly associated with C3/4 disc degeneration (69.7%, p < 0.001), and smokers were more subject to dizziness (p < 0.05). Regression analysis showed that female (OR = 1.611, p = 0.031), smoking (OR = 1.719, p = 0.032), Miyazaki grade of C3/4 ≥ IV (OR = 2.648, p < 0.001), and instability on C3/4 (OR = 1.672, p = 0.024) were risk factors for CSD. Treatment of CSD by ACDF involving C3/4 was more effective than not involving C3/4 (efficacy rate, 73.2% vs 51.7%, p < 0.05).

CONCLUSION

The CSD is a common clinical manifestation in elderly patients, especially patients with cervical spondylosis at the C3/4 level. Female, smoking, instability on C3/4, and C3/4 Miyazaki grade ≥ IV could be considered significant risk factors for CSD. CSD is more likely to be alleviated by ACDF involving C3/4.

Instant reduction in postural sway during quiet standing by intraoral dental appliance in patients with Whiplash associated Disorders and non-trauma neck pain

OBJECTIVES

This study tested the hypothesis that modulation of jaw sensorimotor control by intraoral dental appliance can reduce postural sway during quiet standing and hence improve standing balance, in patients with whiplash associated disorders (WAD) and non-trauma neck pain.

DESIGN

Postural sway during quiet standing with feet together was examined in 54 WAD patients (40 females) and 10 non-trauma patients (8 females) using wireless 3D movement recording technique. Recordings were performed alternating without and with intraoral dental appliance, and with closed eyes and open eyes, respectively. In this protocol the participants served as their own controls. A reference group of 30 healthy subjects (17 females) was also recorded. Each recording lasted 120 s, followed by 3-5 min of rest. Speed, acceleration and perimeter of postural sway area were documented.

RESULTS

In the patients, but not in the healthy group, the intraoral dental appliance instantly and significantly reduced standing postural sway in recordings with closed and open eyes.

CONCLUSIONS

The prompt reduction in standing postural sway from intervention by intraoral dental appliance i.e. improved standing balance, suggests a potent effect on the postural control system by modulation of the jaw sensorimotor system, probably involving reflex transmission. The result opens for new insight into mechanisms behind postural control and the pathophysiology of balance disorders, and adds to the knowledge on plasticity of the nervous system. It may help developing new procedures for assessment and management of impaired balance in WAD and non-trauma neck pain patients.

Cervical Intervertebral Disc Degeneration Contributes to Dizziness: A Clinical and Immunohistochemical Study

OBJECTIVES

Dizziness often happens in patients with chronic neck pain with only cervical disc degeneration but without cervical radiculopathy or myelopathy. We prospectively selected a series of patients who showed cervical disc degeneration with concomitant chronic neck pain and intractable dizziness who did not respond to conservative treatment to test a new diagnostic method for this dizziness, to analyze the results of anterior cervical discectomy and fusion (ACDF) surgery based on the test, and to explore its pathogenesis.

METHODS

Seventy-seven patients who had a transient neck pain and dizziness relief after injection of bupivacaine into a suspected disc were included in the study. In total, 52 underwent ACDF as surgery group, and 25 refused surgery and accepted conservative treatments as conservative group from June, 2015 to October, 2016 with subsequent follow-up to 1 year. The outcomes were visual analogue scale for neck pain, Neck Disability Index, and intensity and frequency of dizziness. During ACDF, the 72 specimens of degenerative cervical discs were collected to determine the innervation in degenerative cervical discs immunohistochemically.

RESULTS

After surgery, the patients experienced a significant reduction in neck pain and dizziness. Symptomatic relief in surgery group was obviously better than conservative group at each time point of follow-up (P = 0.001). Ruffini corpuscles and substance P-positive free nerve fibers were obviously increased in the number and deeply ingrown into the inner degenerative cervical discs.

CONCLUSIONS

Current clinical and immunohistochemical studies strongly suggest that chronic neck pain and intractable dizziness in this series of patients stem from the degenerative cervical discs.

The effectiveness of anterior cervical decompression and fusion for the relief of dizziness in patients with cervical spondylosis: a multicentre prospective cohort study

AIMS

Cervical spondylosis is often accompanied by dizziness. It has recently been shown that the ingrowth of Ruffini corpuscles into diseased cervical discs may be related to cervicogenic dizziness. In order to evaluate whether cervicogenic dizziness stems from the diseased cervical disc, we performed a prospective cohort study to assess the effectiveness of anterior cervical discectomy and fusion on the relief of dizziness.

PATIENTS AND METHODS

Of 145 patients with cervical spondylosis and dizziness, 116 underwent anterior cervical decompression and fusion and 29 underwent conservative treatment. All were followed up for one year. The primary outcomes were measures of the intensity and frequency of dizziness. Secondary outcomes were changes in the modified Japanese Orthopaedic Association (mJOA) score and a visual analogue scale score for neck pain.

RESULTS

There were significantly lower scores for the intensity and frequency of dizziness in the surgical group compared with the conservative group at different time points during the one-year follow-up period (p = 0.001). There was a significant improvement in mJOA scores in the surgical group.

CONCLUSION

This study indicates that anterior cervical surgery can relieve dizziness in patients with cervical spondylosis and that dizziness is an accompanying manifestation of cervical spondylosis. Cite this article: Bone Joint J 2018;100-B:81-7.

Cervical Vertigo: Historical Reviews and Advances

Vertigo is one of the most common presentations in adult patients. Among the various causes of vertigo, so-called cervical vertigo is still a controversial entity. Cervical vertigo was first thought to be due to abnormal input from cervical sympathetic nerves based on the work of Barré and Liéou in 1928. Later studies found that cerebral blood flow is not influenced by sympathetic stimulation. Ryan and Cope in 1955 proposed that abnormal sensory information from the damaged joint receptors of upper cervical regions may be related to pathologies of vertigo of cervical origin. Further studies found that cervical vertigo seems to originate from diseased cervical intervertebral discs. Recent research found that the ingrowth of a large number of Ruffini corpuscles into diseased cervical discs may be related to vertigo of cervical origin. Abnormal neck proprioceptive input integrated from the signals of Ruffini corpuscles in diseased cervical discs and muscle spindles in tense neck muscles secondary to neck pain is transmitted to the central nervous system and leads to a sensory mismatch with vestibular and other sensory information, resulting in a subjective feeling of vertigo and unsteadiness. Further studies are needed to illustrate the complex pathophysiologic mechanisms of cervical vertigo and to better understand and manage this perplexing entity.

Disturbed cervical proprioception affects perception of spatial orientation while in motion

The proprioceptive, visual and vestibular sensory systems interact to maintain dynamic stability during movement. The relative importance and interplay between these sensory systems is still not fully understood. Increased knowledge about spatial perception and postural orientation would provide better understanding of balance disorders, and their rehabilitation. Displacement of the body in space was recorded in 16 healthy subjects performing a sequence of stepping-in-place tests without any visual or auditory cues. Spatial displacement and orientation in space were determined by calculating two parameters, “Moved distance (sagittal + lateral displacement)” and “Rotation”. During the stepping-in-place tests vibration were applied in a randomized order on four different cervical muscles, and the effects were compared between muscles and to a non-vibration baseline condition. During the tests a forward displacement (“Moved distance”) was found to be the normal behavior, with various degrees of longitudinal rotation (“Rotation”). The moved distance was significantly larger when the vibration was applied on the dorsal muscles (916 mm) relative to on ventral muscles (715 mm) (p = 0.003) and the rate of displacement was significantly larger for dorsal muscles (36.5 mm/s) relative to ventral (28.7 mm/s) vs (p = 0.002). When vibration was applied on the left-sided muscles, 16° rotation to the right was induced (p = 0.005), whereas no significant rotation direction was induced with right-sided vibration (3°). The rate of rotation was significantly larger for vibration applied on ventral muscles (0.44°/s) relative to on dorsal (0.33°/s) (p = 0.019). The results highlight the influence of cervical proprioception on the internal spatial orientation, and subsequent for postural control.

Mechanoreceptors in Diseased Cervical Intervertebral Disc and Vertigo

STUDY DESIGN

We collected the samples of cervical intervertebral discs from patients with vertigo to examine the distribution and types of mechanoreceptors in diseased cervical disc.

OBJECTIVE

The aim of this study was to determine whether mechanoreceptors are distributed more abundantly in cervical discs from patients with cervical spondylosis, and whether they are related to vertigo.

SUMMARY OF BACKGROUND DATA

Previous limited studies have found that normal cervical intervertebral discs are supplied with mechanoreceptors that have been considered responsible for proprioceptive functions. Several clinical studies have indicated that the patients with cervical spondylosis manifested significantly impaired postural control and subjective balance disturbance.

METHODS

We collected 77 samples of cervical discs from 62 cervical spondylosis patients without vertigo, 61 samples from 54 patients with vertigo, and 40 control samples from 8 cadaveric donors to investigate distribution of mechanoreceptors containing neurofilament (NF200) and S-100 protein immunoreactive nerve endings.

RESULTS

The immunohistochemical investigation revealed that the most frequently encountered mechanoreceptors were the Ruffini corpuscles in all groups of cervical disc samples. They were obviously increased in the number and deeply ingrown into inner annulus fibrosus and even into nucleus pulposus in the diseased cervical discs from patients with vertigo in comparison with the discs from patients without vertigo and control discs. Only three Golgi endings were seen in the three samples from patients with vertigo. No Pacinian corpuscles were found in any samples of cervical discs.

CONCLUSION

The diseased cervical discs from patients with vertigo had more abundant distribution of Ruffini corpuscles than other discs. A positive association between the increased number and ingrowth of Ruffini corpuscles in the diseased cervical disc and the incidence of vertigo in the patients with cervical spondylosis was found, which may indicate a key role of Ruffini corpuscles in the pathogenesis of vertigo of cervical origin.

LEVEL OF EVIDENCE

1.

People With Chronic Neck Pain Walk With a Stiffer Spine

Study Design Controlled laboratory study, case-control design. Objective To evaluate spine kinematics and gait characteristics in people with nonspecific chronic neck pain. Background People with chronic neck pain present with a number of sensorimotor and biomechanical alterations, yet little is known about the influence of neck pain on gait and motions of the spine during gait. Methods People with chronic nonspecific neck pain and age- and sex-matched asymptomatic controls walked on a treadmill at 3 different speeds (self-selected, 3 km/h, and 5 km/h), either with their head in a neutral position or rotated 30°. Tridimensional motion capture was employed to quantify body kinematics. Neck and trunk rotations were derived from the difference between the transverse plane component of the head and thorax and thorax and pelvis angles to provide an indication of neck and trunk rotation during gait. Results Overall, the patient group showed shorter stride length compared to the control group (P<.001). Moreover, the patients with neck pain showed smaller trunk rotations (P<.001), regardless of the condition or speed. The difference in the amount of trunk rotation between groups became larger for the conditions of walking with the head rotated. Conclusion People with chronic neck pain walk with reduced trunk rotation, especially when challenged by walking with their head positioned in rotation. Reduced rotation of the trunk during gait may have long-term consequences on spinal health. J Orthop Sports Phys Ther 2017;47(4):268-277. Epub 3 Feb 2017. doi:10.2519/jospt.2017.6768.

The conundrum of cervicogenic dizziness

Cervicogenic or cervical dizziness is debated as an entity. However, there exists both a physiologic basis and a multitude of clinical data to make such a disease concept at least possible and worth considering. In addition, the interaction of proprioceptive and vestibular mechanisms may amplify dizziness of other origin. Cervical pain and dizziness are both common symptoms and may coincide, and neck pain or obvious dysfunction does not necessarily cause dizziness or balance disturbances. So far, there is also the lack of a proper diagnostic test for cervicogenic dizziness. On the other hand, there is growing evidence that cervical proprioceptive input is important for balance and postural control not only in animals but also in humans, and that intervention in disorders affecting the human cervical segment may relieve dizziness in some patients. It is advocated that the diagnosis should be used with care and that there is a need for better diagnostic tests. In the absence of such a test, one has to rely on preliminary criteria and a diagnosis ex juvantibus. A possible approach would require patients to present with neck pain before or in close temporal relation with dizziness; that other causes should be made at least unlikely; and that treatment of a cervical dysfunction reduces also dizziness or balance disturbance.

The influence of headaches in patients with chronic dizziness

CONCLUSION

The frequency of headaches in patients complaining of chronic dizziness is closely related to the severity of the dizziness impairments and mood states, such as anxiety. It is, therefore, important to treat co-morbid headache in patients with chronic dizziness. The severity of the dizziness impairments and other mood states, including anxiety, did not differ between patients with migraine or non-migraine headaches.

OBJECTIVES

Patients with chronic dizziness often complain of headaches or general fatigue. This study investigated the influence of the frequency of headaches on dizziness impairments, anxiety, quality-of-life, and other mood states in patients with chronic dizziness.

METHOD

The subjects consisted of 100 consecutive patients with intractable dizziness. Several types of questionnaires were used in the investigations.

RESULTS

Of the 85 patients, 51 had either type of headache (tension headache, 38; migraine, 13). The total score on the Dizziness Handicap Inventory correlated linearly with general fatigue (R = 0.39, p < 0.001) and headache (R = 0.25, p < 0.05). The patients with any type of headache had a significantly more positive family history of headache (p < 0.05).

Experimentally induced deep cervical muscle pain distorts head on trunk orientation

PURPOSE

We wanted to explore the specific proprioceptive effect of cervical pain on sensorimotor control. Sensorimotor control comprises proprioceptive feedback, central integration and subsequent muscular response. Pain might be one cause of previously reported disturbances in joint kinematics, head on trunk orientation and postural control. However, the causal relationship between the impact of cervical pain on proprioception and thus on sensorimotor control has to be established.

METHODS

Eleven healthy subjects were examined in their ability to reproduce two different head on trunk targets, neutral head position (NHP) and 30° target position, with a 3D motion analyser before, directly after and 15 min after experimentally induced neck pain. Pain was induced by hypertonic saline infusion at C2/3 level in the splenius capitis muscle on one side (referred to as "injected side").

RESULTS

All subjects experienced temporary pain and the head repositioning error increased significantly during head repositioning to the 30° target to the injected side (p = 0.011). A post hoc analysis showed that pain interfered with proprioception to the injected side during acute pain (p < 0.001), but also when the pain had waned (p = 0.002). Accuracy decreased immediately after pain induction for the 30° target position to the side where pain was induced (3.3 → 5.3°, p = 0.033), but not to the contralateral side (4.9 → 4.1°, p = 0.657). There was no significant impact of pain on accuracy for NHP. A sensory mismatch appeared in some subjects, who experienced dizziness.

CONCLUSIONS

Acute cervical pain distorts sensorimotor control with side-specific changes, but also has more complex effects that appear when pain has waned.

Treating balance disorders by ultra-low-level laser stimulation of acupoints

BACKGROUND

Balance disorders, a widespread problem in the senior population, are very often related to painful musculoskeletal disabilities and/or to degenerative neurologic pathologies. In a previous work, we investigated the beneficial effects of acupuncture such as laser photobiostimulation, regardless of the etiological origin of the balance dysfunction.

AIMS

Attention was focused on two individuals showing balance deficits with different etiologies. One healthy control individual was receiving treatment, one healthy control individual did not receive any treatment. Balance performances were measured before and after ultra-low-level laser (ULLL) stimulation as a basis for the design of further investigations.

METHODS

Romberg's parameters were measured on a force platform. Of the four tested individuals, one showed dizziness symptoms, one was affected by a mild form of Parkinson's disease, and two showed no dysfunction and were used as controls.

RESULTS

It was found that a ULLL stimulation of peripheral Traditional Chinese Medicine (TCM) acupuncture points can be effective, regardless of the pathology.

DISCUSSION

A specific clinical analysis of the stability of the beneficial result as a function of homogeneous groups of dysfunctional individuals is needed.

Impaired postural control in patients affected by tension-type headache

Sixteen subjects, affected by chronic tension-type headache (TTH) accordingly to the International Headache Society Classification (1988) criteria, in presence of tenderness in pericranial muscles,with a mean age of 37+/-11.8 years, and ten healthy volunteer subjects, age and sex matched, were submitted to postural analysis by Static Posturography (S.Ve.P. Amplaid). Aim of the study was to evaluate whether patients with TTH have disturbed postural control, as compared to normal subjects. Postural analysis considered all posturographic variables but focused on spectral frequency analysis of body sway. In both open (OE) and closed eyes (CE) condition, spectral frequency analysis showed a significantly increased body sway at low (OE= p < or = 0.01; CE= p < or = 0.01) and middle (OE= p < or = 0.01; CE= p < or = 0.01) frequencies on the antero-posterior (y) plane and at low frequencies (OE= p < or = 0.05; CE= p < or = 0.05) on the lateral (x) plane. Statistical analysis was performed using the Student's t test for unpaired data, p value 0.05 defined significant. The proprioceptive input seems to be predominant at middle and high frequencies in maintaining posture, our results seem then to suggest a proprioceptive disturbance in TTH patients. The disturbance is likely related to chronic pericranial muscle contraction and tenderness. Posturography and spectral analysis may help not only in the diagnosis of a postural disturbance but even more in the follow-up of TTH patients, during and after a medical and/or a rehabilitative treatment.

Manual therapy with and without vestibular rehabilitation for cervicogenic dizziness: a systematic review

BACKGROUND

Manual therapy is an intervention commonly advocated in the management of dizziness of a suspected cervical origin. Vestibular rehabilitation exercises have been shown to be effective in the treatment of unilateral peripheral vestibular disorders, and have also been suggested in the literature as an adjunct in the treatment of cervicogenic dizziness. The purpose of this systematic review is to evaluate the evidence for manual therapy, in conjunction with or without vestibular rehabilitation, in the management of cervicogenic dizziness.

METHODS

A comprehensive search was conducted in the databases Scopus, Mantis, CINHAL and the Cochrane Library for terms related to manual therapy, vestibular rehabilitation and cervicogenic dizziness. Included studies were assessed using the Maastricht-Amsterdam criteria.

RESULTS

A total of fifteen articles reporting findings from thirteen unique investigations, including five randomised controlled trials and eight prospective, non-controlled cohort studies were included in this review. The methodological quality of the included studies was generally poor to moderate. All but one study reported improvement in dizziness following either unimodal or multimodal manual therapy interventions. Some studies reported improvements in postural stability, joint positioning, range of motion, muscle tenderness, neck pain and vertebrobasilar artery blood flow velocity.

DISCUSSION

Although it has been argued that manual therapy combined with vestibular rehabilitation may be superior in the treatment of cervicogenic dizziness, there are currently no observational and experimental studies demonstrating such effects. A rationale for combining manual therapy and vestibular rehabilitation in the management of cervicogenic dizziness is presented.

CONCLUSION

There is moderate evidence to support the use of manual therapy, in particular spinal mobilisation and manipulation, for cervicogenic dizziness. The evidence for combining manual therapy and vestibular rehabilitation in the management of cervicogenic dizziness is lacking. Further research to elucidate potential synergistic effects of manual therapy and vestibular rehabilitation is strongly recommended.

Altered postural sway in patients suffering from non-specific neck pain and whiplash associated disorder - A systematic review of the literature

Study design

Systematic literature review.

Objectives

To assess differences in center of pressure (COP) measures in patients suffering from non-specific neck pain (NSNP) or whiplash-associated disorder (WAD) compared to healthy controls and any relationship between changes in postural sway and the presence of pain, its intensity, previous pain duration and the perceived level of disability.

Summary of Background data

Over the past 20 years, the center of pressure (COP) has been commonly used as an index of postural stability in standing. While several studies investigated COP excursions in neck pain and WAD patients and compared these to healthy individuals, no comprehensive analysis of the reported differences in postural sway pattern exists.

Search methods

Six online databases were systematically searched followed by a manual search of the retrieved papers.

Selection Criteria

Papers comparing COP measures derived from bipedal static task conditions on a force plate of people with NSNP and WAD to those of healthy controls.

Data collection and analysis

Two reviewers independently screened titles and abstracts for relevance. Screening for final inclusion, data extraction and quality assessment were carried out with a third reviewer to reconcile differences.

Results

Ten papers met the inclusion criteria. Heterogeneity in study designs prevented pooling of the data and no direct comparison of data across the studies was possible. Instead, a qualitative data analysis was conducted. There was broad consensus that patients with either type of neck pain have increased COP excursions compared to healthy individuals, a difference that was more pronounced in people with WAD. An increased sway in antero-posterior direction was observed in both groups.

Conclusions

Patients with neck pain (due to either NSNP or WAD) exhibit greater postural instability than healthy controls, signified by greater COP excursions irrespective of the COP parameter chosen. Further, the decreased postural stability in people with neck pain appears to be associated with the presence of pain and correlates with the extent of proprioceptive impairment, but appears unrelated to pain duration.

The effect of neck torsion on postural stability in subjects with persistent whiplash

Dysfunction of cervical receptors in neck disorders has been shown to lead to disturbances in postural stability. The neck torsion manoeuvre used in the smooth pursuit neck torsion (SPNT) test is thought to be a specific measure of neck afferent dysfunction on eye movement in those with neck pain. This study aimed to determine whether neck torsion could change balance responses in those with persistent whiplash-associated disorders (WADs). Twenty subjects with persistent WAD and 20 healthy controls aged between 18 and 50 years stood on a computerised force plate with eyes closed in comfortable stance under 5 conditions: neutral head, head turned to left and right and neck torsion to left and right. Root mean square (rms) amplitude of sway was measured in the anterior-posterior (AP) and medial-lateral (ML) directions. The whiplash group had significantly greater rms amplitude in the AP direction following neck torsion compared to the control group (p < 0.03). The results show that the neck torsion manoeuvre may lead to greater postural deficits in individuals with persistent WAD and provides further evidence of neck torsion to identify abnormal cervical afferent input, as an underlying cause of balance disturbances in WAD. Further research is warranted.

Influence of cervical spine stabilization via Stiff Neck on the postural system in healthy patients: compensation or decompensation of the postural system?

Functional and structural disorders of the cervical spine are often regarded as the cause of non-specific vertigo. Pathogenetically, disorders of proprioceptive connections between neck muscles and vestibular cores as well as the proprioceptors in the cervical facette joints are presumed. According to a study by Hülse and Hölzl (HNO 48:295-301, 1), after manual therapeutic intervention in patients with functional disorders of the cervical spine 50% of the probands stated a significant reduction of their vertigo. This was backed up in posturography, which documented an improvement in vestibulospinal reactions. To date, the effects of artificial as well as surgical stabilization of the cervical spine on the balance system have not been explored yet. In a first pilot study, we examined the influence of artificial stabilization of the cervical spine via cervical collar Stiff Neck, manufactured by Ambu/Perfit ACE] on the balance system of 20 healthy probands. For this purpose, a posturography (Balance Master Systems, NeuroCom, Clackamas, OR, USA) was applied to 20 healthy probands (10 males, 10 females) with a mean age of 35 years who had no prior spine pathology. Posturography was analyzed under static and dynamic test situations with and without Stiff Neck cervical collar. The results were compared statistically to the Wilcoxon test. In the static test situation of the modified clinical test of sensory interaction on balance, a significantly improved standing stability occurred. In none of the dynamic tests did fixation of the cervical spine by Stiff Neck cuff lead to a measurable impairment of the movement coordination. All probands felt subjectively more stable when wearing the Stiff Neck. In healthy probands, a fixation of the cervical spine leads to a stabilization of the postural balance situation. This fixation seems to be helpful in compensating the malfunction of other components of balance information. In a next step, this same model of analysis is applied to patients with cervical instability. Standing stability and movement coordination before and after cervical fusion are being explored.

Head repositioning accuracy and posturography related to cervical facet nerve blockade and spinal manipulative therapy in healthy volunteers: a time series study

OBJECTIVE

The aim of the study was to investigate if changes in head repositioning accuracy (HRA), and standing balance could be evoked by unilateral facet nerve blockade (FNB) or spinal manipulative therapy (SMT).

METHODS

This time series research study (n = 6) was chosen because of the viability of the experiment, sample characteristics, and small sample size. Cervical proprioceptive functions were assessed by exploring HRA and static posture by computerized posturography. All participants were subjected to 2 interventions, unilateral FNB using local anesthetic and SMT.

RESULTS

No significant trends were seen in the subjects over the period of the study. All measurements were taken approximately 3 weeks apart. Visually, it was detected that most of subjects appeared to be greatly affected by the FNB, thus, increasing their deviation from the center point of measurement in extension and flexion movements. When comparing the changes with respect to the baseline after SMT, all subjects showed some differences, though there was a great deal of variation between the subjects. These trends were also seen when comparing the changes from baseline measurements to those after FNB.

CONCLUSIONS

Data from this time series research design suggest there was no uniform response to unilateral FNB or to SMT. However, differences indicate that there may be important effects of unilateral FNBs for some of the HRA aspects measured. Balance testing using computerized posturography did not show clear differences between baseline assessments and interventions. A future larger clinical study to detect changes in HRA evoked by unilateral FNB or SMT appears feasible.

Cervicocephalic kinesthetic sensibility and postural balance in patients with nontraumatic chronic neck pain--a pilot study

Background

Although cervical pain is widespread, most victims are only mildly and occasionally affected. A minority, however, suffer chronic pain and/or functional impairments. Although there is abundant literature regarding nontraumatic neck pain, little focuses on diagnostic criteria. During the last decade, research on neck pain has been designed to evaluate underlying pathophysiological mechanisms, without noteworthy success. Independent researchers have investigated postural balance and cervicocephalic kinesthetic sensibility among patients with chronic neck pain, and have (in most cases) concluded the source of the problem is a reduced ability in the neck's proprioceptive system. Here, we investigated cervicocephalic kinesthetic sensibility and postural balance among patients with nontraumatic chronic neck pain.

Methods

Ours was a two-group, observational pilot study of patients with complaints of continuous neck pain during the 3 months prior to recruitment. Thirteen patients with chronic neck pain of nontraumatic origin were recruited from an institutional outpatient clinic. Sixteen healthy persons were recruited as a control group. Cervicocephalic kinesthetic sensibility was assessed by exploring head repositioning accuracy and postural balance was measured with computerized static posturography.

Results

Parameters of cervicocephalic kinesthetic sensibility were not reduced. However, in one of six test movements (flexion), global repositioning errors were significantly larger in the experimental group than in the control group (p < .05). Measurements did not demonstrate any general impaired postural balance, and varied substantially among participants in both groups.

Conclusion

In patients with nontraumatic chronic neck pain, we found statistically significant global repositioning errors in only one of six test movements. In this cohort, we found no evidence of impaired postural balance.

Head repositioning accuracy and computerized static posturography are imperfect measures of functional proprioceptive impairments. Validity of (and procedures for using) these instruments demand further investigation.

Trial registration

Current Controlled Trials ISRCTN96873990

Long-term symptoms in dizzy patients examined in a university clinic

Background

The long-term course of dizziness was investigated combining medical chart and survey data. The survey was undertaken median (interquartile range (IQR)) 4.6 (4.3) years after the initial medical examination.

Methods

Chart data comprised sex, age, diagnosis, symptom duration, postural sway and neck pain. Survey data comprised symptom severity assessed by the Vertigo Symptom Scale – Short Form (VSS-SF), and data regarding current state of dizziness, medication, neck pain and other chronic conditions.

Results

The sample consisted of 503 patients, the mean (standard deviation (SD)) age was 50.0 (11.6) years, women being slightly overrepresented (60%). Severe problems with dizziness (VSS-SF mean (SD) 13.9, (10.8)) were indicated in the total group and in 5 of 6 diagnostic sub-groups. Vertigo/balance- and autonomic/anxiety-related symptoms were present in all groups. Current dizziness was confirmed by 73% who had significantly more severe problems than the non-dizzy (VSS-SF mean (SD): 17.2 (10.1) versus 5.0 (7.3)). Symptoms were related to vertigo/balance more than to autonomic/anxiety (test of interaction p < 0.001).

Based on simple logistic regression analysis, sex, symptom duration, neck pain, sway and diagnoses predicted dizziness. Symptom duration and neck pain remained predictors in the adjusted analysis. Age, symptom duration, neck pain, sway and diagnoses predicted vertigo/balance-related dizziness in both regression analyses. Sex, neck pain and sway predicted development of autonomic/anxiety-related dizziness according to simple regression analysis, while only neck pain remained a significant predictor in the adjusted analysis. With respect to diagnosis, simple regression analysis showed significant reduced likelihood for development of dizziness in all vestibular sub-groups when compared to the non-otogenic dizziness group. With respect to vertigo/balance- and autonomic/anxiety-related symptoms, the implication of diagnostic belonging varied. No effect of diagnoses was seen in adjusted analyses.

Conclusion

The majority of patients had persistent and severe problems with dizziness. The wait-and-see attitude before referral to specialist institutions may be questioned. Early, active movements seem necessary, and attention should be paid to the presence of neck pain. Diagnoses had limited prognostic value. Questionnaire-based evaluations could assist in classification and identification of type of dizziness and thereby provide a better basis for specific rehabilitation.

Sensorimotor function and dizziness in neck pain: implications for assessment and management

SYNOPSIS

The term sensorimotor describes all the afferent, efferent, and central integration and processing components involved in maintaining stability in the postural control system through intrinsic motor-control properties. The scope of this paper is to highlight the sensorimotor deficits that can arise from altered cervical afferent input. From a clinical orthopaedic perspective, the peripheral mechanoreceptors are the most important in functional joint stability; but in the cervical region they are also important for postural stability, as well as head and eye movement control. Consequently, conventional musculoskeletal intervention approaches may be sufficient only for patients with neck pain and minimal sensorimotor proprioceptive disturbances. Clinical experience and research indicates that significant sensorimotor cervical proprioceptive disturbances might be an important factor in the maintenance, recurrence, or progression of various symptoms in some patients with neck pain. In these cases, more specific and novel treatment methods are needed which progressively address neck position and movement sense, as well as cervicogenic oculomotor disturbances, postural stability, and cervicogenic dizziness. In this commentary we review the most relevant theoretical and practical knowledge on this matter and implications for clinical assessment and management, and we propose future directions for research.

LEVEL OF EVIDENCE

Level 5.

Subclinical deviation of the subjective visual vertical in patients affected by a primary headache

CONCLUSION

Our results suggest that patients with migraine or tension-type headache have subclinical deviations of the subjective visual vertical, which may be associated with their subjective imbalance.

OBJECTIVES

Patients affected by migraine or tension-type headache often complain of unsteadiness. However, they rarely show a clinical significance in the objective examinations of their equilibrium. We investigated the equilibrium functions in patients affected by migraine or tension-type headache.

SUBJECTS AND METHODS

We investigated the neurotological findings of 17 patients with migraine, 20 patients with tension-type headaches, and 16 patients without headache. All patients in this study experienced vertigo or dizziness before they underwent the examination; however, they never had vertigo attacks for more than 1 month before the examination. All patients in this study were tested during headache-free intervals.

RESULTS

There was no significant difference in the hearing levels of pure tone audiometry, the canal palsy percentage of bithermal caloric test, and the body sway in posturography among the three groups (p>0.05, Mann-Whitney U test). The average values in absolute deviations of subjective visual vertical (SVV) in patients with tension-type headache (1.3+/-1.1 degrees ) and patients with migraine (1.5+/-1.2 degrees ) were significantly larger in comparison with those of patients without headache (0.6+/-0.4) (p<0.05, Mann-Whitney U test). Intra-individual varaiances of the SVV in patients with primary headache were significantly larger than those in patients without headache (p<0.05, Mann-Whitney U test).

Rehabilitation program for traumatic chronic cervical pain associated with unsteadiness: a single case study

BACKGROUND

Neck problems are often recurring or chronic. After pain, unsteadiness and balance problems are among the most frequent symptoms reported by chronic neck pain (CNP) patients. Altered sensorimotor control of the cervical spine and sensorimotor integration problems affecting postural control have been observed in CNP patients. Very few data are available regarding the post-intervention effects of rehabilitation programs on postural control in CNP.

CASE PRESENTATION

This is a case study of a traumatic CNP patient (a 45-year old female) with postural unsteadiness who participated in an 8-week rehabilitation program combining therapeutic exercises with spinal manipulative therapy. Pre-intervention data revealed that the postural control system was challenged when postural control sensory inputs were altered, particularly during the head-extended-backward condition. Post-intervention centre of pressure measurements indicated a drastic reduction in postural sway during trials with changes in neck orientation.

CONCLUSION

This case report indicates that an 8-week rehabilitation program combining therapeutic exercises with spinal manipulative therapy may have had an effect on improvement of postural control in a trauma CNP patient with unsteadiness. These results warrant further studies to investigate the relationships between pain amelioration, sensorimotor control of the cervical spine, muscle fitness and postural steadiness.

Standing balance: A comparison between idiopathic and whiplash-induced neck pain

Disturbances of balance have been found both in patients with whiplash-associated disorders and idiopathic neck pain. This study directly compared balance between these groups to determine if neck pain precipitated by trauma resulted in greater or different balance impairments. The study was a comparative, observational design. Thirty subjects with whiplash, 30 with idiopathic neck pain and 30 healthy controls, took part in the study. Subjects performed balance tests in comfortable, narrow and tandem stances. Balance disturbances (sway energy and/or root mean squared (RMS) amplitude) were evident in several tests between subjects with neck pain and controls. Direct comparison between the neck pain groups revealed that the whiplash group had significantly greater sway energy and RMS amplitude than the idiopathic group in comfortable stance tests on a soft surface (F > 4.4, p < 0.04). Further, the whiplash group had greater RMS, but significantly less sway energy than the idiopathic group in most narrow stance tests in the anterior posterior direction F > 5.8, p < 0.02). Both neck pain groups were also significantly less able to complete the eyes closed, tandem test compared to control subjects. In conclusion, the study has found that balance deficits exist in both subjects with whiplash-associated disorders and idiopathic neck pain compared to controls; however, differences in balance strategies may exist between the neck pain groups. Overall, subjects who have experienced trauma appear to have greater balance disturbances.

Pathophysiology of tension-type headache

Tension-type headache is one of the most common primary headache disorders. Advances in basic pain and clinical research have improved our understanding of pathophysiologic mechanisms of tension-type headache. Increased excitability of the central nervous system generated by repetitive and sustained pericranial myofascial input may be responsible for the transformation of episodic tension-type headache into the chronic form. Studies of nitric oxide (NO) mechanisms suggest that NO may play a key role in the pathophysiology of tension-type headache and that the antinociceptive effect of nitric oxide synthase inhibitors may become a novel principle in the future treatment of chronic headache. Future studies should focus on investigation of the source of peripheral nociception, the role of descending pain modulation, and the development of an animal model of tension-type headache to support the pathophysiologic importance of central sensitization in tension-type headache.

Neck muscle fatigue and postural control in patients with whiplash injury

OBJECTIVES

To examine if patients with whiplash injury show identifiable increases in neck muscle fatigability and associated increase in postural body sway after contractions of dorsal neck muscles, and if physiotherapy treatment reduces these effects.

METHODS

Sway was measured during stance in 13 patients before and after 5 min of isometric dorsal neck muscle contractions and after recovery, pre- and post-physiotherapy, using a force platform. Amplitude and median frequency of neck muscle EMG were calculated during the contracting period. After each stance trial, patients gave a subjective score of sway.

RESULTS

Pre-treatment, seven patients showed EMG signs of fatigue (increases in amplitude, decreases in median frequency) and increases in sway (eyes closed) after contractions. The other patients showed neither fatigue nor increased sway. Post-treatment, no signs of fatigue or imbalance were recorded in all patients, for the same levels of muscle contraction.

CONCLUSIONS

As in normal human subjects, increases in sway are associated with signs of neck muscle fatigue in some whiplash injury patients. Physiotherapy decreases the susceptibility to fatigue of neck muscles and is an effective choice of treatment of subjective instability and sway.

SIGNIFICANCE

This study demonstrates a pathophysiological link between neck muscle fatigue and impaired postural control, and also that physiotherapy can relieve symptoms and signs of impaired neck muscle function by reducing muscle fatigability.

Responses of muscle spindles in feline dorsal neck muscles to electrical stimulation of the cervical sympathetic nerve

Previous studies performed in jaw muscles of rabbits and rats have demonstrated that sympathetic outflow may affect the activity of muscle spindle afferents (MSAs). The resulting impairment of MSA information has been suggested to be involved in the genesis and spread of chronic muscle pain. The present study was designed to investigate sympathetic influences on muscle spindles in feline trapezius and splenius muscles (TrSp), as these muscles are commonly affected by chronic pain in humans. Experiments were carried out in cats anesthetized with alpha-chloralose. The effect of electrical stimulation (10 Hz for 90 s or 3 Hz for 5 min) of the peripheral stump of the cervical sympathetic nerve (CSN) was investigated on the discharge of TrSp MSAs (units classified as Ia-like and II-like) and on their responses to sinusoidal stretching of these muscles. In some of the experiments, the local microcirculation of the muscles was monitored by laser Doppler flowmetry. In total, 46 MSAs were recorded. Stimulation of the CSN at 10 Hz powerfully depressed the mean discharge rate of the majority of the tested MSAs (73%) and also affected the sensitivity of MSAs to sinusoidal changes of muscle length, which were evaluated in terms of amplitude and phase of the sinusoidal fitting of unitary activity. The amplitude was significantly reduced in Ia-like units and variably affected in II-like units, while in general the phase was affected little and not changed significantly in either group. The discharge of a smaller percentage of tested units was also modulated by 3-Hz CSN stimulation. Blockade of the neuromuscular junctions by pancuronium did not induce any changes in MSA responses to CSN stimulation, showing that these responses were not secondary to changes in extrafusal or fusimotor activity. Further data showed that the sympathetically induced modulation of MSA discharge was not secondary to the concomitant reduction of muscle blood flow induced by the stimulation. Hence, changes in sympathetic outflow can modulate the afferent signals from muscle spindles through an action exerted directly on the spindles, independent of changes in blood flow. It is suggested that such an action may be one of the mechanisms mediating the onset of chronic muscle pain in these muscles in humans.

Neck muscle fatigue and spatial orientation during stepping in place in humans

Neck proprioceptive input, as elicited by muscle vibration, can produce destabilizing effects on stance and locomotion. Neck muscle fatigue produces destabilizing effects on stance, too. Our aim was to assess whether neck muscle fatigue can also perturb the orientation in space during a walking task. Direction and amplitude of the path covered during stepping in place were measured in 10 blindfolded subjects, who performed five 30-s stepping trials before and after a 5-min period of isometric dorsal neck muscle contraction against a load. Neck muscle electromyogram amplitude and median frequency during the head extensor effort were used to compute a fatigue index. Head and body kinematics were recorded by an optoelectronic system, and stepping cadence was measured by sensorized insoles. Before the contraction period, subjects normally stepped on the spot or drifted forward. After contraction, some subjects reproduced the same behavior, whereas others reduced their forward progression or even stepped backward. The former subjects showed minimal signs of fatigue and the latter ones marked signs of fatigue, as quantified by the dorsal neck electromyogram index. Head position and cadence were unaffected in either group of subjects. We argue that the abnormal fatigue-induced afferent input originating in the receptors transducing the neck muscle metabolic state can modulate the egocentric spatial reference frame. Notably, the effects of neck muscle fatigue on orientation are opposite to those produced by neck proprioception. The neck represents a complex source of inputs capable of modifying our orientation in space during a locomotor task.

Cervicogenic dizziness: a review of diagnosis and treatment

The diagnosis of cervicogenic dizziness is characterized by dizziness and dysequilibrium that is associated with neck pain in patients with cervical pathology. The diagnosis and treatment of an individual presenting with cervical spine dysfunction and associated dizziness complaints can be a challenging experience to orthopaedic and vestibular rehabilitation specialists. The purpose of this article is to review the incidence and prevalence, historical background, and proposed pathophysiology underlying cervicogenic dizziness. In addition, we have outlined the diagnostic criteria, evaluation, and treatment of dizziness attributed to disorders of the cervical spine. The diagnosis of cervicogenic dizziness is dependent upon correlating symptoms of imbalance and dizziness with neck pain and excluding other vestibular disorders based on history, examination, and vestibular function tests. When diagnosed correctly, cervicogenic dizziness can be successfully treated using a combination of manual therapy and vestibular rehabilitation. We present 2 cases, of patients diagnosed with cervicogenic dizziness, as an illustration of the clinical decision-making process in regard to this diagnosis.

Experimental muscle pain produces central modulation of proprioceptive signals arising from jaw muscle spindles

The aim of the present study was to investigate the effects of intramuscular injection with hypertonic saline, a well-established experimental model for muscle pain, on central processing of proprioceptive input from jaw muscle spindle afferents. Fifty-seven cells were recorded from the medial edge of the subnucleus interpolaris (Vi) and the adjacent parvicellular reticular formation from 11 adult cats. These cells were characterized as central units receiving jaw muscle spindle input based on their responses to electrical stimulation of the masseter nerve, muscle palpation and jaw stretch. Forty-five cells, which were successfully tested with 5% hypertonic saline, were categorized as either dynamic-static (DS) (n=25) or static (S) (n=20) neurons based on their responses to different speeds and amplitudes of jaw movement. Seventy-six percent of the cells tested with an ipsilateral injection of hypertonic saline showed a significant modulation of mean firing rates (MFRs) during opening and/or holding phases. The most remarkable saline-induced change was a significant reduction of MFR during the hold phase in S units (100%, 18/18 modulated). Sixty-nine percent of the DS units (11/16 modulated) also showed significant changes in MFRs limited to the hold phase. However, in the DS neurons, the MFRs increased in seven units and decreased in four units. Finally, five DS neurons showed significant changes of MFRs during both opening and holding phases. Injections of isotonic saline into the ipsilateral masseter muscle had little effect, but hypertonic saline injections made into the contralateral masseter muscle produced similar results to ipsilateral injections with hypertonic saline. These results unequivocally demonstrate that intramuscular injection with an algesic substance, sufficient to produce muscle pain, produces significant changes in the proprioceptive properties of the jaw movement-related neurons. Potential mechanisms involved in saline-induced changes in the proprioceptive signals and functional implications of the changes are discussed.