The Role of Ultrasound for the Personalized Botulinum Toxin Treatment of Cervical Dystonia

Neurosurgical and pharmacological management of dystonia

Dystonia characterizes a group of neurological movement disorders characterized by abnormal muscle movements, often with repetitive or sustained contraction resulting in abnormal posturing. Different types of dystonia present based on the affected body regions and play a prominent role in determining the potential efficacy of a given intervention. For most patients afflicted with these disorders, an exact cause is rarely identified, so treatment mainly focuses on symptomatic alleviation. Pharmacological agents, such as oral anticholinergic administration and botulinum toxin injection, play a major role in the initial treatment of patients. In more severe and/or refractory cases, focal areas for neurosurgical intervention are identified and targeted to improve quality of life. Deep brain stimulation (DBS) targets these anatomical locations to minimize dystonia symptoms. Surgical ablation procedures and peripheral denervation surgeries also offer potential treatment to patients who do not respond to DBS. These management options grant providers and patients the ability to weigh the benefits and risks for each individual patient profile. This review article explores these pharmacological and neurosurgical management modalities for dystonia, providing a comprehensive assessment of each of their benefits and shortcomings.

Botulinum toxin injection for abductor spasmodic dysphonia under cervical ultrasonography guidance

Ultrasound (US) imaging effectively provides real-time anatomical information for clinical examinations. In otolaryngology, US imaging can visualize laryngeal muscles as well as cervical muscles. Here we present the case where US imaging was used while injecting botulinum toxin (BT) for the treatment of abductor spasmodic dysphonia, which provided definite results. We could visualize not only the injection pathway but also the infiltration of the BT solution into the posterior cricoarytenoid muscles. Therefore, our laryngeal US imaging is useful for both improving the success rate and avoiding injection complications of BT.

Botulinum Toxin Injections to the Obliquus Capitis Inferioris Muscle for Dynamic Cervical Dystonia Improves Subjective Patient Outcomes

The obliquus capitis inferioris (OCI) muscle is a significant driver of cervical dystonia with torticaput movements and a no-no head tremor. Limited data are available on the efficacy of OCI injections on patient outcomes. Our study aims to determine whether the botulinum toxin injection into OCI improves subjective patient quality of life in those with dystonic head tremors. A retrospective chart review was performed for 25 patients receiving injections into the OCI for a dystonic head tremor at the London Movement Disorders Clinic between January 2020 and January 2022. Toronto Western Spasmodic Torticollis Scale-2 (TWSTRS-2) subscale scores for disability and pain, TWSTRS-PSYCH scores, and the global impression of severity were extracted. The average TWSTRS-2 disability subscale change was -2.8 points (p < 0.003). The average TWSTRS-2 pain subscale change was -4.6 points (p < 0.003). The average TWSTRS-PSYCH score prior to injection was 5.6. After injection, the average score was 3.7 (p < 0.004). The patient self-reported average global impression of severity before injection was 7.0; after this, it was 4.2 (p < 0.0003). The OCI injection showed significant improvement in retrospective patient self-reported outcomes; it should be considered early in the treatment plan for cervical dystonia with a no-no head tremor.

Hypertrophy of the Spinalis Cervicis Muscle in Cervical Dystonia

Background

Botulinum neurotoxin A (BoNT) is the first line treatment for cervical dystonia (CD) and treatment outcome significantly depends on the correct identification of the muscles involved.

Phenomenology shown

In a case with insufficient response to BoNT treatment further work up with magnetic resonance imaging (MRI) of the neck revealed a hypertrophic spinalis cervicis muscle, that is not commonly involved in CD.

Educational value

This highlights the use of MRI for muscle selection in treatment refractory CD cases.

Eligibility criteria in clinical trials for cervical dystonia

INTRODUCTION

Cervical dystonia (CD) is the most common form of adult-onset focal dystonia. Because of a heterogeneous clinical presentation, the diagnosis rests on clinical opinion. During the last decades, several clinical trials have tested safety and efficacy of medical and surgical treatments for CD. We analyzed all the published CD trials and reviewed the strategies adopted for patient enrollment.

METHODS

The review included clinical trials in patients with CD published in PubMed. Studies were excluded if reviews, meta-analyses, post-hoc analyses on pooled data, or if not reporting a treatment for CD.

RESULTS

A total of 174 articles were identified; 134 studies met inclusion criteria. Diagnosis of CD varied among studies and in most cases was based on clinical judgement, using different descriptors such as "cervical dystonia" (37 studies), "idiopathic or isolated CD" (35), "primary CD" (13), and "torticollis" (40). Clinical judgement was supported by a phenomenological description of dystonia in four studies, and by a specific diagnostic strategy in other four. Finally, one study adopted general diagnostic criteria for dystonia. Inclusion and exclusion criteria proved heterogeneous across trials and were defined only in 108 studies, mainly considering age or the phenomenological pattern of muscle involvement.

CONCLUSION

The review showed lack of consolidated diagnostic criteria and non-uniformity of eligibility criteria for CD across clinical trials. There is need to move beyond clinical judgement as diagnostic criterion for selecting participants. New trials assessing specific CD patient subgroups or comparing medical and surgical procedures will need grounds that are more consistent.

Botulinum Toxin Therapy for Oromandibular Dystonia and Other Movement Disorders in the Stomatognathic System

Various movement disorders, such as oromandibular dystonia, oral dyskinesia, bruxism, functional (psychogenic) movement disorder, and tremors, exist in the stomatognathic system. Most patients experiencing involuntary movements due to these disorders visit dentists or oral surgeons, who may be the first healthcare providers. However, differential diagnoses require neurological and dental knowledge. This study aimed to review scientific advances in botulinum toxin therapy for these conditions. The results indicated that botulinum toxin injection is effective and safe, with few side effects in most cases when properly administered by an experienced clinician. The diagnosis and treatment of movement disorders in the stomatognathic system require both neurological and dental or oral surgical knowledge and skills, and well-designed multicenter trials with a multidisciplinary team approach must be necessary to ensure accurate diagnosis and proper treatment.

Pivotal role of obliquus capitis inferior in torticaput revealed by single-photon emission computed tomography

Torticaput is the most common primary form of cervical dystonia (CD). Obliquus capitis inferior (OCI) plays a major role in ipsilateral rotation of the head. The present study aimed to use single-photon emission computed tomography (SPECT/CT) to determine the involvement of OCI in torticaput and in torticaput associated with no-no tremor. We retrospectively analyzed the SPECT/CT images of 60 patients with torticaput as the main abnormal posture and ranked the affected muscles. The affected muscles in patients with no-no tremor were also ranked. The correlation between the radioactivity of OCI and the thickness of OCI measured by ultrasonography was analyzed. The agreement between SPECT/CT and electromyography in detecting OCI was also analyzed. After sternocleidomastoid muscle (81.7%), OCI was the second most affected muscle (70.0%) in torticaput, followed by splenius capitis (63.3%). In 23 patients with no-no tremor, OCI (78.3%) and sternocleidomastoid muscle (78.3%) were the most frequently affected muscles, followed by splenius capitis (69.6%). Furthermore, bilateral muscle involvement was commonly seen in patients with no-no tremor, especially for OCI (12/23) and sternocleidomastoid muscle (11/23). A positive correlation was found between the radioactivity and thickness of OCI (r = 0.330, P < 0.001). The total agreement rate between SPECT/CT and electromyography in the diagnosis of OCI excitement was 94.0%, with kappa value = 0.866 (P < 0.001). OCI plays a critical role in torticaput and no-no tremor. SPECT/CT could be a practical tool to help clinicians detect abnormally excited OCI.

Editorial on the Special Issue "Botulinum Toxin for the Treatment of Neurological Disorders: Where We Are and Where We Need to Go"

Over the past 30 years, botulinum toxin (BoNT) has seen an ever-expanding use in disorders afflicting the nervous system [...].

Pain in cervical dystonia: mechanisms, assessment and treatment

INTRODUCTION

In patients with cervical dystonia (CD), pain is a major contributor to disability and social isolation and is often the main reason patients seek treatment. Surveys evaluating patient perceptions of their CD symptoms consistently highlight pain as a troublesome and disabling feature of their condition with significant impact on daily life and work.

AREAS COVERED

In this article, the authors review the epidemiology, assessment, possible mechanisms and treatment of pain in CD, including a meta-analysis of randomized controlled trial data with abobotulinumtoxinA.

EXPERT OPINION

Mechanisms of pain in CD may be muscle-based and non-muscle based. Accumulating evidence suggests that non-muscle-based mechanisms (such as abnormal transmission and processing of nociceptive stimuli, dysfunction of descending pain inhibitory pathways as well as structural and network changes in the basal ganglia, cortex and other areas) may also contribute to pain in CD alongside prolonged muscle contraction. Chemodenervation with botulinum toxin is considered the first-line treatment for CD. Treatment with botulinum toxin is usually effective, but optimization of the injection parameters should include consideration of pain as a core symptom in addition to the motor problems.