Abnormal interaction between vestibular and voluntary head control in patients with spasmodic torticollis

Rethinking Movement Disorders

At present, clinical practice and research in movement disorders (MDs) focus on the "normalization" of altered movements. In this review, rather than concentrating on problems and burdens people with MDs undoubtedly have, we highlight their hidden potentials. Starting with current definitions of Parkinson's disease (PD), dystonia, chorea, and tics, we outline that solely conceiving these phenomena as signs of dysfunction falls short of their complex nature comprising both problems and potentials. Such potentials can be traced and understood in light of well-established cognitive neuroscience frameworks, particularly ideomotor principles, and their influential modern derivatives. Using these frameworks, the wealth of data on altered perception-action integration in the different MDs can be explained and systematized using the mechanism-oriented concept of perception-action binding. According to this concept, MDs can be understood as phenomena requiring and fostering flexible modifications of perception-action associations. Consequently, although conceived as being caught in a (trough) state of deficits, given their high flexibility, people with MDs also have high potential to switch to (adaptive) peak activity that can be conceptualized as hidden potentials. Currently, clinical practice and research in MDs are concerned with deficits and thus the "deep and wide troughs," whereas "scattered narrow peaks" reflecting hidden potentials are neglected. To better delineate and utilize the latter to alleviate the burden of affected people, and destigmatize their conditions, we suggest some measures, including computational modeling combined with neurophysiological methods and tailored treatment. © 2024 International Parkinson and Movement Disorder Society.

Comparison of Oropharyngeal Dysphagia Before and After Botulinum Toxin Injection in Cervical Dystonia

Cervical dystonia (CD) is the most common form of focal dystonia with Botulinum neurotoxin (BoNT) being a frequent method of treatment. Dysphagia is a common side effect of BoNT treatment for CD. Instrumental evaluation of swallowing in CD using standardized scoring for the videofluoroscopic swallowing study (VFSS) and validated and reliable patient-reported outcomes measures is lacking in the literature. (1) to determine if BoNT injections change instrumental findings of swallowing function using the Modified Barium Swallow Impairment Profile (MBSImP) in individuals with CD; (2) to determine if BoNT injections change self-perception of the psychosocial handicapping effects of dysphagia in individuals with CD, using the Dysphagia Handicap Index (DHI); (3) to determine the effect of BoNT dosage on instrumental swallowing evaluation and self-reported swallowing outcomes measures. 18 subjects with CD completed a VFSS and the DHI before and after BoNT injection. There was a significant increase in pharyngeal residue for pudding consistency after BoNT injection, p = 0.015. There were significant positive associations between BoNT dosage and self-perception of the physical attributes of the handicapping effect of dysphagia, the grand total score and patient self-reported severity of dysphagia on the DHI; p = 0.022; p = 0.037; p = 0.035 respectively. There were several significant associations between changes in MBSImP scores and BoNT dose. Pharyngeal efficiency of swallowing may be affected by BoNT for thicker consistencies. Individuals with CD perceive greater physical handicapping effects of dysphagia with increased amounts of BoNT units and have greater self-perceptions of dysphagia severity with increased amounts of BoNT units.

Isolated Cervical Dystonia: Diagnosis and Classification

This document presents a consensus on the diagnosis and classification of isolated cervical dystonia (iCD) with a review of proposed terminology. The International Parkinson and Movement Disorder Society Dystonia Study Group convened a panel of experts to review the main clinical and diagnostic issues related to iCD and to arrive at a consensus on diagnostic criteria and classification. These criteria are intended for use in clinical research, but also may be used to guide clinical practice. The benchmark is expert clinical observation and evaluation. The criteria aim to systematize the use of terminology as well as the diagnostic process, to make it reproducible across centers and applicable by expert and non-expert clinicians. Although motor abnormalities remain central, increasing recognition has been given to nonmotor manifestations, which are incorporated into the current criteria. Three iCD presentations are described in some detail: idiopathic (focal or segmental) iCD, genetic iCD, and acquired iCD. The relationship between iCD and isolated head tremor is also reviewed. Recognition of idiopathic iCD has two levels of certainty, definite or probable, supported by specific diagnostic criteria. Although a probable diagnosis is appropriate for clinical practice, a higher diagnostic level may be required for specific research studies. The consensus retains elements proven valuable in previous criteria and omits aspects that are no longer justified, thereby encapsulating diagnosis according to current knowledge. As understanding of iCD expands, these criteria will need continuous revision to accommodate new advances. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.

Impaired trunk control and its relationship with balance, functional mobility, and disease severity in patients with cervical dystonia

BACKGROUND

Impaired trunk control is common in neurological disorders; however, trunk control has not been examined in patients with cervical dystonia (CD). Therefore, the primary aim was to compare trunk control between patients with CD and healthy people. The secondary aim was to investigate the relationship between trunk control and balance, functional mobility, and disease severity in patients with CD.

METHODS

]This cross-sectional study included 32 patients with CD and 32 healthy people. Trunk control was compared using the trunk impairment scale (TIS) that consists of three subscales: static sitting balance, dynamic sitting balance, and trunk coordination between two groups. Balance was assessed using Berg Balance Scale, four square step test, and one-leg stance test. The Timed Up and Go Test was measured to determine functional mobility. Toronto Western Spasmodic Torticollis Rating Scale was used to evaluate disease severity.]></AbstractText> <AbstractText Label="RESULTS"><![CDATA[ Patients with CD demonstrated worse performance on the TIS-total with TIS-dynamic sitting subscale and TIS-trunk coordination subscale (p < 0.001, p < 0.001, and p < 0.001), except for TIS-static sitting subscale (p = 0.078) compared to healthy people. TIS-total scores had moderate to strong correlations with balance, functional mobility, and disease severity (range r between 0.786 and 0.536, p < 0.05 for all). There was no correlation between TIS-total scores and disease severity (p = 0.102).

DISCUSSION

Patients with CD had impaired trunk control, especially in dynamic sitting balance and trunk coordination. Impaired trunk control was also associated with balance and functional mobility but not disease severity. These findings suggest that trunk control deficits should receive attention in the assessment and treatment of patients with CD.

Sensorimotor Control in Dystonia

This is an overview of the sensorimotor impairments in dystonia, a syndrome characterized by sustained or intermittent aberrant movement patterns leading to abnormal movements and/or postures with or without a tremulous component. Dystonia can affect the entire body or specific body regions and results from a plethora of etiologies, including subtle changes in gray and white matter in several brain regions. Research over the last 25 years addressing topics of sensorimotor control has shown functional sensorimotor impairments related to sensorimotor integration, timing, oculomotor and head control, as well as upper and lower limb control. In the context of efforts to update the classification of dystonia, sensorimotor research is highly relevant for a better understanding of the underlying pathology, and potential mechanisms contributing to global and regional dysfunction within the central nervous system. This overview of relevant research regarding sensorimotor control in humans with idiopathic dystonia attempts to frame the dysfunction with respect to what is known regarding motor control in patients and healthy individuals. We also highlight promising avenues for the future study of neuromotor control that may help to further elucidate dystonia etiology, pathology, and functional characteristics.

Impairments of balance, stepping reactions and gait in people with cervical dystonia

BACKGROUND

Impaired balance is common in neurological disorders. Cervical dystonia is a neurological movement disorder affecting the neck. The effect of this aberrant head posture on physical function is unknown.

OBJECTIVES

To compare balance, mobility, gait and stepping reactions between ten people with cervical dystonia and ten control adults.

METHODS

Spatiotemporal gait parameters and walking speed were assessed using a computerised walkway. Step length and time, time in double support and gait variability were calculated, then normalised to gait speed. Centre of pressure path length was assessed with eyes open and eyes closed to calculate a Romberg Quotient. Simple and choice reaction times were measured using customised apparatus while mobility was assessed by the timed up and go. Cervical spine range of motion was measured using a head mounted goniometer. Self-reported scales included Falls Self Efficacy Scale and Dystonia Discomfort Scale.

RESULTS

There was a difference between groups for most outcome measures. The timed up-and-go and walking speed was slower (both P<0.005) and the Romberg Quotient lower (P=0.046) in cervical dystonia. People with cervical dystonia had lower falls self-efficacy (P=0.0002). Reduced cervical range of motion was correlated with balance, stepping reaction time and mobility (all P<0.05). Timed up and go was positively associated with stepping reaction time (P<0.01). Dystonia discomfort did not impact function.

CONCLUSIONS

People with cervical dystonia displayed deficits in balance, gait and stepping reactions, and expressed higher fear of falling. Studies to further elucidate functional limitations and their impact on activity and participation in daily life are required.

Dynamic head-neck stabilization in cervical dystonia

BACKGROUND

Effective sensorimotor integration is essential to modulate (adapt) neck stabilization strategies in response to varying tasks and disturbances. This study evaluates the hypothesis that relative to healthy controls cervical dystonia patients have an impaired ability to modulate afferent feedback for neck stabilization with changes in the frequency content of mechanical perturbations.

METHODS

We applied anterior-posterior displacement perturbations (110s) on the torso of seated subjects, while recording head-neck kinematics and muscular activity. We compared low bandwidth (0.2-1.2Hz) and high bandwidth (0.2-8Hz) perturbations where our previous research showed a profound modulation of stabilization strategies in healthy subjects. Cervical dystonia patients and age matched controls performed two tasks: (1) maintain head forward posture and (2) allow dystonia to dictate head posture.

FINDINGS

Patients and controls demonstrated similar kinematic and muscular responses. Patient modulation was similar to that of healthy controls (P>0.05); neck stiffness and afferent feedback decreased with high bandwidth perturbations. During the head forward task patients had an increased neck stiffness relative to controls (P<0.05), due to increased afferent feedback.

INTERPRETATION

The unaffected modulation of head-neck stabilization (both kinematic and muscular) in patients with cervical dystonia does not support the hypothesis of impaired afferent feedback modulation for neck stabilization.

Interactions between voluntary head control and neck proprioceptive reflexes in cervical dystonia

BACKGROUND

To investigate deficiencies in mechanisms of sensorimotor processing and reflexive-voluntary interactions leading to the impaired head position control in primary cervical dystonia.

METHODS

Thirteen patients and 23 healthy controls were subjected to transient, low amplitude, low velocity head-on-trunk, trunk-under-head and whole-body rotations in the horizontal plane. With the instruction not to resist the imposed displacements, resistance to horizontal neck deflections was evaluated.

RESULTS

Patients exhibited a torque offset (bias) in the direction of torticollis before stimulus application. While controls reduced and occasionally eliminated completely the initial resistance to head-to-trunk rotations, torque in patients increased throughout displacements. Change of resistance relative to baseline in patients was, however, symmetrical, i.e. independent of torticollis direction. Spontaneous torque fluctuations were significantly larger in patients. Strong correlations existed among these abnormal findings.

CONCLUSIONS

Patients' ability to manipulate normal postural reactions to head-trunk rotations is impaired. The deficit is bilateral and correlates with the degree of abnormal posture. The present study extends previous work on reflexive-voluntary interactions and provides evidence that malfunctioning proprioceptive feedback may contribute to the pathophysiology of cervical dystonia.

The role of the trigeminal sensory nuclear complex in the pathophysiology of craniocervical dystonia

Isolated focal dystonia is a neurological disorder that manifests as repetitive involuntary spasms and/or aberrant postures of the affected body part. Craniocervical dystonia involves muscles of the eye, jaw, larynx, or neck. The pathophysiology is unclear, and effective therapies are limited. One mechanism for increased muscle activity in craniocervical dystonia is loss of inhibition involving the trigeminal sensory nuclear complex (TSNC). The TSNC is tightly integrated into functionally connected regions subserving sensorimotor control of the neck and face. It mediates both excitatory and inhibitory reflexes of the jaw, face, and neck. These reflexes are often aberrant in craniocervical dystonia, leading to our hypothesis that the TSNC may play a central role in these particular focal dystonias. In this review, we present a hypothetical extended brain network model that includes the TSNC in describing the pathophysiology of craniocervical dystonia. Our model suggests the TSNC may become hyperexcitable due to loss of tonic inhibition by functionally connected motor nuclei such as the motor cortex, basal ganglia, and cerebellum. Disordered sensory input from trigeminal nerve afferents, such as aberrant feedback from dystonic muscles, may continue to potentiate brainstem circuits subserving craniocervical muscle control. We suggest that potentiation of the TSNC may also contribute to disordered sensorimotor control of face and neck muscles via ascending and cortical descending projections. Better understanding of the role of the TSNC within the extended neural network contributing to the pathophysiology of craniocervical dystonia may facilitate the development of new therapies such as noninvasive brain stimulation.

Keeping your head on target

The mechanisms by which the human brain controls eye movements are reasonably well understood, but those for the head less so. Here, we show that the mechanisms for keeping the head aimed at a stationary target follow strategies similar to those for holding the eyes steady on stationary targets. Specifically, we applied the neural integrator hypothesis that originally was developed for holding the eyes still in eccentric gaze positions to describe how the head is held still when turned toward an eccentric target. We found that normal humans make head movements consistent with the neural integrator hypothesis, except that additional sensory feedback is needed, from proprioceptors in the neck, to keep the head on target. We also show that the complicated patterns of head movements in patients with cervical dystonia can be predicted by deficits in a neural integrator for head motor control. These results support ideas originally developed from animal studies that suggest fundamental similarities between oculomotor and cephalomotor control, as well as a conceptual framework for cervical dystonia that departs considerably from current clinical views.

Trunk bradykinesia and foveation delays during whole-body turns in spasmodic torticollis

We have investigated how the abnormal head posture and motility in spasmodic torticollis interferes with ecological movements such as combined eye-to-foot whole-body reorientations to visual targets. Eight mildly affected patients and 10 controls voluntarily rotated eyes and body in response to illuminated targets of eccentricities up to ±180°. The experimental protocol allowed separate evaluation of the effects of target location, visibility and predictability on movement parameters. Patients’ latencies of eye, head, trunk and foot motion were prolonged but showed a normal modification pattern when target location was predictable. Peak head-on-trunk displacement and velocity were reduced both ipsi- and contralaterally with respect to the direction of torticollis. Surprisingly, peak trunk velocity was also reduced, even more than in previously studied patients with Parkinson’s disease. As a consequence, patients made short, hypometric gaze saccades and only exceptionally foveated initially nonvisible targets with a single large gaze shift (4 % of predictable trials as opposed to 30 % in controls). Foveation of distant targets was massively delayed by more than half a second on average. Spontaneous dystonic head movements did not interfere with the execution of voluntary gaze shifts. The results show that neck dystonia does not arise from gaze (head-eye) motor centres but the eye-to-foot turning synergy is seriously compromised. For the first time we identify significant ‘secondary’ complications of torticollis such as trunk bradykinesia and foveation delays, likely to cause additional disability in patients. Eye movements per se are intact and compensate for the reduced head/trunk performance in an adaptive manner.

Balance

This chapter addresses the important and undertreated problem of balance disorders. The chapter has a simplified summary of the physiology of balance problems in order to set the scene. The issue of assessment is next addressed with discussion of important tests including the Berg Balance Scale and the Get Up and Go Test, and others. Posturography is discussed as well as assessment of the gravitional vertical. The assessment of vestibular function is of key importance and discussed in some detail. The focus of the chapter is on balance rehabilitation. Re-training of postural alignment and of sensory strategies are key but adaptation of the environment and re-training of cognitive strategies are also helpful in individual cases. Vestibular exercises can also be used. The chapter then critically analyses the efficacy of these treatments in specific balance disorders such as in stroke, Parkinson disease, polyneuropathies, multiple sclerosis, and vestibular disorders. Overall, there is a growing body of evidence that balance rehabilitation improves symptoms, function, and quality of life for those troubled by these disabling problems.

Interaction between vestibulo-spinal and corticospinal systems: a combined caloric and transcranial magnetic stimulation study

We investigated the interaction between vestibular and corticospinal stimuli in 8 healthy volunteers. Vestibular stimulation was induced with unilateral ear caloric irrigation (30°C) with subjects supine. Single transcranial magnetic stimulation (TMS) pulses were delivered (double-cone coil, intensities 60-75% maximal output) every 10-20 s during vestibular activation and during baseline. Bilateral surface electromyography (EMG) from splenius capitis, sternocleidomastoid (SCM), obliquus externus abdominis, vastus lateralis, biceps femoris (BF), tibialis anterior and peroneus longus was obtained. During whole-body maximal rotatory voluntary isometric contraction (MRVC), only SCM and BF displayed EMG activation/inhibition patterns indicating axial rotatory action. TMS-induced motor evoked potentials (MEPs) after caloric irrigation revealed that only SCM showed consistent vestibular-mediated excitation/inhibition responses, i.e. an increase in MEP area contralateral to the irrigation and a decrease in MEP area ipsilaterally (+12.7 and -6.3% of the MRVC, respectively). A putative head turn induced by this SCM activity pattern would be in the same direction of the slow-phase eye movement. EMG in the 100 ms preceding TMS showed muscle tone values of approximately 10% of MRVC. After caloric irrigation, these values increased by ca. 2% for all muscles bilaterally and hence cannot explain the direction-specific SCM MEP changes. Thus, SCM MEPs show caloric-induced amplitude modulation indicating that SCM is under both horizontal semicircular canal and corticospinal control. This vestibular modulation of corticospinal SCM control likely occurs at cortical levels. The direction of the MEP modulation indicates a directional coupling between vestibularly induced head and eye movements.

Clinical and neurophysiological improvement of SGCE myoclonus-dystonia with GPi deep brain stimulation

Myoclonus-dystonia (M-D) is characterized by early onset myoclonus and dystonia. It is thought to be subcortical in origin. Response to oral medications may be incomplete, such that deep brain stimulation (DBS) surgery to the globus pallidum interna (GPi) or ventral intermediate thalamic nucleus (VIM) may be considered. The optimal site is not known. The physiology and surgical response for a 63-year-old woman who underwent GPi DBS for M-D with onset at age 2 and related to a mutation in the epsilon-sarcoglycan gene (SGCE) is described. She showed excellent clinical and neurophysiological improvement of both myoclonus and dystonia, suggesting that modulation by DBS is effective even after long disease duration and only partial response to oral medications.

Subthalamotomy in cervical dystonia: A case study of lesion location and clinical outcome

Here we report a 63-year-old woman with primary cervical dystonia (CD) whose symptoms subsided for more than 30 years following a unilateral stereotactic subthalamotomy contralateral to the overactive left sternocleidomastoid muscle but then gradually recurred over a period of several months. The aim of the present study was to correlate the topography of the stereotactic lesion with the long lasting therapeutic effect. High-resolution magnetic resonance imaging and subsequent stereotactic analysis were performed to determine the anatomical localization of the lesion. The primary coagulation focus comprised the posterior subthalamic white matter in the prelemniscal radiation and field H of Forel. Neighboring structures were implicated to various extents. It is suggested that the posterior subthalamic area, with its abundance of interconnecting fibers and related nuclei, represents an effective target for the neurosurgical treatment of CD that may be explored further with deep brain stimulation.

Postural control and sensory integration in cervical dystonia

OBJECTIVE

Postural control and sensory integration were assessed in 12 patients with Cervical Dystonia (CD) and 11 healthy control subjects (CS), who were asked to maintain their posture as vertical as possible with their eyes open and closed while standing on a platform tilting laterally at angular accelerations below the vestibular activation threshold.

METHODS

Data were collected with a three-dimensional acquisition system. The orientation and stabilization components were studied using specific indexes. We also tested the subjective visual vertical.

RESULTS

CD does not affect whole body postural control. CD patients were able to control the orientation of their head. CS stabilized their head in space, especially when their eyes were open. This head stabilization strategy was lost in the CD patients, and the presence of visual inputs made no difference. CD patients seemed to neglect the visual information when controlling their head. The RFT confirmed this visual independence.

CONCLUSION

CD patients seem to ignore the sensory information skewed by the disease: their reference segment shifts from head to trunk and they tend to preferentially use proprioceptive information.

SIGNIFICANCE

As the proprioceptive chain remains functional in CD patients, it seems likely that the vestibular system might rather be involved in the pathophysiology of CD.

Animal models of focal dystonia

Animal models indicate that the abnormal movements of focal dystonia result from disordered sensorimotor integration. Sensorimotor integration involves a comparison of sensory information resulting from a movement with the sensory information expected from the movement. Unanticipated sensory signals identified by sensorimotor processing serve as signals to modify the ongoing movement or the planning for subsequent movements. Normally, this process is an effective mechanism to modify neural commands for ongoing movement or for movement planning. Animal models of the focal dystonias spasmodic torticollis, writer's cramp, and benign essential blepharospasm reveal different dysfunctions of sensorimotor integration through which dystonia can arise. Animal models of spasmodic torticollis demonstrate that modifications in a variety of regions are capable of creating abnormal head postures. These data indicate that disruption of neural signals in one structure may mutate the activity pattern of other elements of the neural circuits for movement. The animal model of writer's cramp demonstrates the importance of abnormal sensory processing in generating dystonic movements. Animal models of blepharospasm illustrate how disrupting motor adaptation can produce dystonia. Together, these models show mechanisms by which disruptions in sensorimotor integration can create dystonic movements.

Laterality and imbalance of muscle stiffness relate to personality

The authors' purpose in this study was to test the hypothesis that laterality and imbalance of muscle stiffness relate to personality. The authors selected 23 healthy volunteers and divided them into two groups based on the predominance of muscle stiffness on the left or right side. Imbalance of muscle stiffness was calculated as the absolute value of the difference of muscle stiffness between the right and left sides. The authors evaluated personality with the Japanese version of the Eysenck Personality Questionnaire. Subjects with left predominant muscle stiffness of the rectal abdominis had significantly higher neuroticism score than those with right predominant muscle stiffness. Subjects with more imbalance of muscle stiffness in the latissimus dorsi and in the trapezius had significantly higher neuroticism and psychoticism scores than those with less imbalance. The findings suggest that laterality and imbalance of muscle stiffness relate to personality.

Natural history and syndromic associations of orthostatic tremor: a review of 41 patients

Orthostatic tremor (OT) is a rare condition characterized by unsteadiness when standing still that is relieved when sitting or walking and is thought to arise from a central generator in the cerebellum or brainstem. OT is considered to be a distinct, discrete condition, and little is known about its demographic characteristics, natural history, associated features, and treatment response. We have reviewed these aspects in 41 OT patients fulfilling current diagnostic criteria, seen at our institution between 1986 and 2001. We classified 31 (75%) as having idiopathic "primary OT" either with (n = 24) or without an associated postural arm tremor. We found that 10 of 41 (25%) cases had additional neurological features, and we defined this group as having "OT plus" syndrome. Of these 10, 6 had parkinsonism; 4 of these had typical Parkinson's disease (PD), 1 had vascular and 1 had drug-induced parkinsonism. Among the remaining 4 patients, 2 had restless legs syndrome (RLS), 1 had tardive dyskinesia, and 1 orofacial dyskinesias of uncertain etiology. One patient with PD and the patient with vascular parkinsonism also had RLS. Age at onset was significantly earlier in the "primary OT" (mean +/- SD, 50.4 +/- 15.1) than in the "OT plus" (61.8 +/- 6.4; z = 2.7; P =.006) group. In 7 of the 10 "OT plus" patients, OT leg symptoms preceded the onset of additional neurological features. OT appeared to be underdiagnosed, and on average, it took 5.7 years from the initial complaints until a diagnosis was made. In general, treatment response to a variety of drugs such as clonazepam, primidone, and levodopa was poor. In most cases, OT symptoms remain relatively unchanged over the years, but in 6 of 41 cases (15%), the condition gradually worsened over the years, and in some of these cases, symptoms spread proximally to involve the trunk and arms. OT may not be a discrete disorder as commonly believed and associated features like parkinsonism present in nearly 25% of cases. Dopaminergic dysfunction may have a role in the pathophysiology of this disorder.

Secondary cervical dystonia associated with structural lesions of the central nervous system

We tested the hypothesis that structural lesions of the central nervous system (CNS) associated with cervical dystonia more commonly involve the cerebellum and its primary afferent pathways than basal ganglia structures. Cervical dystonia is the most common focal dystonia, the majority of cases are idiopathic, and only a small percentage of patients have a family history of dystonia or other movement disorders. Pathophysiological mechanisms operative in solely or predominantly appendicular dystonias such as writer's cramp and Oppenheim's dystonia, respectively, may not be directly applicable to axial dystonias. The localization of structural lesions of the CNS associated with secondary cervical dystonia may provide some insight into the neural structures potentially involved in primary cervical dystonia. The National Library of Medicine Gateway (from 1960) and a clinical database maintained by the senior author (from 1999) were searched for cases of secondary cervical dystonia associated with structural lesions of the CNS. Search terms included one or more of the following: dystonia, torticollis, cervical, secondary, and symptomatic. Lesion localization and type, patient age, patient gender, head position, occurrence of sensory tricks, and associated neurological findings were tabulated for each case. Structural lesions associated with cervical dystonia were most commonly localized to the brainstem and cerebellum. The remaining cases were equally divided between the cervical spinal cord and basal ganglia. Although inconsistent, head rotation tended to be contralateral to lesion localization. Additional neurological abnormalities were present in the majority of patients with secondary cervical dystonia. The relative paucity of basal ganglia pathology and concentration of lesions in the brainstem, cerebellum, and cervical spinal cord in patients with secondary cervical dystonia suggests that dysfunction of cerebellar afferent pathways may be important to the pathophysiology of primary cervical dystonia.

Woman with facial spasm induced exclusively by sound

A woman is described in whom facial spasm occurs solely and predictably in the presence of certain noises. The symptoms resolve promptly as soon as the auditory stimulus stops.

Spontaneously changing muscular activation pattern in patients with cervical dystonia

The objective of this study was to determine stability of the neck muscle activation pattern in a given dystonic head position in patients with cervical dystonia (CD). We assessed 26 patients with CD and botulinum toxin (BT) treatment failure before surgical denervation. None of them had received BT injections for at least 4 months. To relate dystonic head position to underlying neck muscle activity, we used synchronised video and poly-electromyographic (EMG) recording over a period of 10 minutes. The muscle activation pattern during constant ("stable") maximal dystonic excursions was analysed. EMG data of nine patients was excluded from the analysis, as these patients had a constantly changing head position or marked head tremor. In the remaining 17 patients, who had a fairly stable dystonic position, muscular activation patterns during the recording spontaneously changed in nine (Group A) while in eight it remained stable (Group B). There was no significant difference in demographic variables between the two groups other than a male predominance in Group A. However, the retrospectively determined initial response to BT treatment (before BT treatment failure had occurred) was significantly worse in Group A as compared with Group B. Neck muscle activation patterns can spontaneously change in CD patients despite constant dystonic head position, implying an inherent variability of the underlying central motor program in some patients. This should be considered when BT treatment response is unsatisfactory, and should also be taken into account when interpreting results of EMG recordings of neck muscles in these patients.

Prospective study of swallowing function in patients with cervical dystonia undergoing selective peripheral denervation

OBJECTIVE

To characterise swallowing function in patients with cervical dystonia with botulinum toxin treatment failure, before and after selective peripheral denervation surgery.

METHODS

Twelve patients with cervical dystonia had a thorough examination including standardised assessment for cervical dystonia, scoring of subjective dysphagia, and videofluoroscopic swallow. Videofluoroscopy was scored by consensus opinion between a speech and language therapist and an independent blinded radiologist using a validated scoring system.

RESULTS

Seven patients with cervical dystonia experienced no subjective dysphagia either before or after surgery, although in all these patients there was objective videofluoroscopic evidence of underlying mild to moderate oropharyngeal dysphagia preoperatively and postoperatively. The most common finding was delayed initiation of swallow. Three other patients, also without subjective dysphagia before surgery, developed postoperative dysphagia. In these patients, videofluoroscopy showed a delayed swallow reflex before surgery, which was worse postoperatively in two. The remaining two patients had mild subjective dysphagia before surgery that improved postoperatively in one and deteriorated in the other. In the first, videofluoroscopy was normal preoperatively and postoperatively, and in the second, oral bolus preparation was moderately abnormal preoperatively and swallow initiation was delayed postoperatively. Mean subjective dysphagia scores did not change significantly. Apart from a significant improvement of tongue base retraction, videofluoroscopic scores were not significantly different after surgery. Postoperatively there was significant improvement of overall cervical dystonia severity and abnormal head rotation in the group as a whole. There was no correlation between age, duration of symptoms of cervical dystonia, preoperative or postoperative cervical dystonia severity, subjective dysphagia scores, or videofluoroscopic scores. However, in the five patients with persisting anterior sagittal head shift as part of the torticollis, tongue base retraction was less likely to improve after surgery compared with those without head shift.

CONCLUSION

Surgical denervation of dystonic neck muscles, leading to improved neck posture, can also improve tongue base retraction, which is a key component of normal bolus propagation. However, delayed swallow initiation, a common feature in patients with cervical dystonia, can be further compromised by surgery, leading to subjective dysphagia. In general, selective peripheral denervation seems to be a safe procedure with no major compromise of swallowing function.