Prospective study of selective peripheral denervation for botulinum-toxin resistant patients with cervical dystonia

Idiopathic foot dystonia treated with intramuscular phenol injection

We describe a patient who developed involuntary, painless, dystonic contraction of the left foot on walking. The patient had been treated with botulinum toxin A without benefit. Examination showed that walking brought on a spasmodic twisting of the left foot, with extension and eversion of the ankle. The patient underwent an intramuscular phenol injection, which abolished the foot dystonia. This case suggests that intramuscular phenol treatment may be an alternative for patients where botulinum toxin was unable to relieve the dystonias.

Surgical therapy for dystonia

Surgical treatments for dystonia have been available since the early 20th century, but have improved in their efficacy to adversity ratio through a combination of technologic advances and better understanding of the role of the basal ganglia in dystonia. The word "dystonia" describes a phenotype of involuntary movement that may manifest from a variety of conditions. Dystonia may affect only certain regions of the body or may be generalized. It appears to be critical to determine whether the etiology underlying the dystonia is "primary" (ie, occurring from a genetic or idiopathic origin) or "secondary" (ie, occurring as a result of structural, metabolic, or neurodegenerative disorders). Secondary dystonias are far more common than primary dystonias. Primary dystonias respond well to pallidotomy or deep brain stimulation of the internal segment of the globus pallidum, whereas secondary dystonias appear to respond partially at best. Limited historic and current data suggest that the thalamus may be a promising target for the treatment of secondary dystonias, but more careful, prospective, randomized studies are needed. Combinations of bilateral targets are possible with the current technology of DBS, but not widely used due to surgical morbidity and expense. This article reviews the surgical treatment of dystonia from past to present, with a focus on separating the outcomes for primary versus secondary and generalized versus cervical dystonia.

Selective peripheral denervation for the treatment of intractable spasmodic torticollis: experience with 168 patients at the Mayo Clinic

OBJECT

Selective peripheral denervation is currently the primary surgical treatment for intractable cervical dystonia. The authors assessed preoperative factors to determine which, if any, correlated with outcomes in patients with torticollis who had undergone this procedure.

METHODS

The records of 168 consecutive patients who had undergone selective peripheral denervation for cervical dystonia between 1988 and 1996 at the Mayo Clinic were reviewed. There were 89 women (53%) and 79 men (47%) with a mean age of 53.4 years. Selection of muscles for denervation was based on the patient's clinical presentation and electromyography mapping results. The most common torticollis vectors were rotational in 141 patients (84%) and laterocollis in 59 (35%). Seventy patients (42%) presented with combined vectors. The technique used to remedy both conditions involved denervation of the ipsilateral posterior cervical paraspinal and splenius capitis muscles. Denervation of the sternocleidomastoid muscle was performed on the contralateral side for rotational torticollis and on the ipsilateral side for laterocollis. A rigorous physical therapy program followed surgery. At the 3-month postoperative evaluation, 125 patients (77%) of the 162 who were available for follow up had moderate to excellent improvement in their head position, and pain was moderately to markedly improved in 131 patients (81%). The long-term follow up lasted a mean of 3.4 years and was undertaken in 130 patients. The original level of moderate to excellent improvement in head position and pain was retained in at least 71 patients (70%). Outcome was not predicted by preoperative head position, severity of abnormal posture of head, symptom duration, presence of tremor or phasic dystonic movements, or failure to respond to botulinum toxin treatment. Five patients recovered from postoperative complications including one myocardial infarction, one pulmonary embolism, and three respiratory failures. Three patients suffered from persistent C-2 distribution dysesthesias and three from slight shoulder weakness; one had a wound infection, and one died of respiratory arrest.

CONCLUSIONS

Selective peripheral denervation is an effective method of achieving lasting improvement of dystonia in most patients with intractable torticollis.

Dystonia: clinical features, genetics, and treatment

PURPOSE OF REVIEW

The present review covers recent advances in dystonia research related to dystonia genetics and treatment. These have led to the discovery of novel dystonia genes and loci, to changing classification schemes, and to the introduction of improved and new treatment options.

RECENT FINDINGS

Currently 13 different forms of dystonia can be distinguished on a genetic basis (dystonia types 1-13). Recently, a novel gene locus (DYT13) was detected in a family with segmental dystonia, and the gene causing myoclonus-dystonia was identified (SGCE). Furthermore, a novel mutation in the DYT1 gene is associated with a myoclonus-dystonia phenotype. Regarding dystonia treatment, patients refractory to botulinum toxin type A can now be treated with botulinum toxin type B. Selective peripheral denervation remains an effective form of treatment for patients with secondary, but probably not with primary botulinum toxin treatment failure. Finally, a renaissance of functional surgical ablative procedures has taken place, with high frequency deep brain stimulation being introduced in dystonia treatment. Bilateral pallidotomy or pallidal stimulation may provide major benefit especially in patients with generalized, disabling dystonia with the most dramatic improvements in dystonia type 1 patients. Neurostimulation may also be effective in primary segmental axial dystonia, myoclonus-dystonia, and tardive dystonia.

SUMMARY

The recent mapping of additional dystonia gene loci, the identification of novel dystonia genes, and the characterization of proteins encoded by these genes have enhanced our understanding of various forms and aspects of the dystonias and have opened up new avenues for research. Treatment options include both medical and surgical therapies, with deep brain simulation being the most recent development.

Pallidal deep brain stimulation in patients with cervical dystonia and severe cervical dyskinesias with cervical myelopathy

OBJECTIVES

Surgical treatment of complex cervical dystonia and of cervical dyskinesias associated with cervical myelopathy is challenging. In this prospective study, the long term effect of chronic pallidal stimulation in cervical dystonia and on combining the technique with spinal surgery in patients with severe cervical dyskinesias and secondary cervical myelopathy is described.

METHODS

Eight patients with a history of chronic dystonia who did not achieve adequate benefit from medical treatment or botulinum toxin injection participated in the study. Five patients had complex cervical dystonia with tonic postures and phasic movements. Three patients had rapidly progressive cervical myelopathy secondary to severe cervical dyskinesias and dystonia in the context of a generalised movement disorder. Quadripolar electrodes were implanted in the posteroventral lateral globus pallidus internus with stereotactic CT and microelectrode guidance. In the three patients with secondary cervical myelopathy, spinal surgery was performed within a few weeks and included multilevel laminectomies and a four level cervical corporectomy with spinal stabilisation.

RESULTS

Improvement of the movement disorder was noted early after pallidal surgery, but the full benefit could be appreciated only with a delay of several months during chronic stimulation. Three months after surgery, patients with cervical dystonia had improved by 38% in the severity score, by 54% in the disability score, and by 38% in the pain score of a modified version of the Toronto western spasmodic torticollis rating scale. At a mean follow up of 20 months, the severity score had improved by 63%, the disability score by 69%, and the pain score by 50% compared with preoperatively. There was also sustained amelioration of cervical dyskinesias in the three patients who underwent spinal surgery. Lead fractures occurred in two patients. The mean amplitude needed for chronic deep brain stimulation was 3.8 V at a mean pulse width of 210 micros, which is higher than that used for pallidal stimulation in Parkinson's disease.

CONCLUSIONS

Chronic pallidal stimulation is effective for complex cervical dystonia and it is a useful adjunct in patients with cervical dyskinesias and secondary cervical myelopathy who undergo spinal surgery.

Botulinum toxin for the treatment of cervical dystonia

Cervical dystonia (CD) manifests clinically through involuntary spasms of neck muscles, producing abnormal head and neck movements and postures, which is often associated with pain. CD is the most common form of focal dystonia presenting to movement disorders clinics. Chemodenervation with botulinum toxin (BTX) has become the first-line treatment for CD, producing satisfactory relief of symptoms in > 80% of cases. Unresolved issues that may impact on the overall results include the method of selection for injection sites (clinical vs. electromyography), dosing, dilution and the role and relative efficacy of the different BTX serotypes. A guiding therapeutic principle of BTX injections is to achieve optimal results with the lowest possible dosage and frequency of administration. This strategy is critical in order to keep the risk of immunoresistance at a minimum. Development of antibodies that block the effects of BTX, usually associated with frequent injections of high doses, is the main reason for secondary unresponsiveness to this treatment. Although the mechanism of denervation at the neuromuscular junction by BTX is relatively well understood, the role of changes in muscle spindles and myopathic pain mechanisms, as well as secondary changes at the level of the basal ganglia, thalamus and cortex and their role in response to BTX, all need further exploration.

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.