Threshold of Clinical Severity of Cervical Dystonia for Positive (18)F-FDG PET/CT

Muscle Function, Muscle Disease, and Positron Emission Tomography-Computed Tomography: A Narrative Review

18F-fluorodeoxyglucose (18F-FDG) is a radiopharmaceutical that exhibits glucose-like kinetics and is used in positron emission tomography (PET). 18F-FDG is used for cancer diagnosis in clinical practice. However, 18F-FDG uptake is also observed in normal organs, such as the brain, liver, and heart, with high glucose consumption. Moreover, 18F-FDG uptake is also observed in muscles, where its accumulation and radioactivity reflect muscle activity. Dystonia is characterized by excessive muscle movement. Recently, 18F-FDG and technetium-99m-methoxyisobutyl isocyanide ([99mTc]MIBI) have been used for the diagnosis and botulinum toxin therapy evaluation of dystonia. This review aimed to summarize the utility of 18F-FDG-PET for the evaluation of muscle activity and diagnosis of muscle diseases such as dystonia, polymyositis, dermatomyositis, and polymyalgia rheumatica.

Therapeutic Efficacy and Prediction of 18F-FDG PET/CT-Assisted Botulinum Toxin Therapy in Patients With Idiopathic Cervical Dystonia

PURPOSE

This study aimed to investigate the therapeutic efficacy of 18F-FDG PET/CT-assisted botulinum toxin (BTX) injection therapy and predictive PET findings in relation to a good response in patients with idiopathic cervical dystonia (ICD).

MATERIALS AND METHODS

A total of 78 patients was enrolled from November 2007 to July 2018. The Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) score was determined at baseline and 4 weeks after BTX injection guided by electromyography and PET/CT. The number of hypermetabolic muscles, the highest SUVmax among hypermetabolic muscles, and the total SUVmax of hypermetabolic muscles were evaluated as pretreatment PET parameters. A good response was defined as a reduction rate ≥30% and a point decrease ≥15 of the TWSTRS total score.

RESULTS

Half of the subjects showed a good response. Good responders had significantly higher baseline TWSTRS scores than poor responders (total score, P < 0.001; severity, P < 0.001; disability, P < 0.001; pain, P = 0.026). Good responders also had significantly higher numbers of hypermetabolic muscles and BTX-injected hypermetabolic muscles (P < 0.001, both). In multivariable analysis, the baseline TWSTRS disability subscale score and the number of BTX-injected hypermetabolic muscles were significant predictors for good response (P = 0.001 and P = 0.028). The aforementioned 3 PET parameters were positively correlated with the baseline TWSTRS scores. In addition, PET/CT well detected dystonic deep cervical muscles.

CONCLUSIONS

FDG PET/CT-assisted BTX injection therapy showed good therapeutic efficacy in ICD patients. The numbers of hypermetabolic cervical muscles and BTX-injected hypermetabolic muscles may be helpful in predicting a good response.

Efficacy of single-photon emission computed tomography aided botulinum toxin injection in cervical dystonia: A double-blind, randomized study

BACKGROUND

Although single-photon emission computed tomography (SPECT/CT) could help to predetermine dystonic muscles in patients with cervical dystonia (CD), its efficacy in aiding botulinum toxin injection is undetermined. This randomized, double-blinded study aimed to assess the efficacy of SPECT/CT aided botulinum toxin injection in CD.

METHODS

Patients were randomized into study group (candidate muscles selected by SPECT/CT and clinical evaluation) or control group (clinical evaluation). Follow-ups were done at two weeks (T1), one (T2), three (T3) and six months (T4). The primary outcomes included symptom improvement assessed using Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS) and Tsui score at T2.

RESULTS

A total of 122 patients were enrolled and 108 patients accomplished the study. For primary outcomes, the study group had significantly better symptom improvement at T2 (TWSTRS: β, -4.86 [95%CI -9.40 to -0.32; P = 0.036]; Tsui: β, -1.65 [95%CI -2.77 to -0.54; P = 0.004]). For secondary outcomes, the study group also showed better outcomes at T1 (TWSTRS: β, -6.33 [95%CI -10.17 to -2.49; P = 0.001]; Tsui: β, -1.42 [95%CI -2.48 to -0.37; P = 0.008]) and T3 (TWSTRS: β, -6.05 [95%CI -11.09 to -1.01; P = 0.019]; Tsui: β, -1.24 [95%CI -2.40 to -0.08; P = 0.037]). The interval of re-injection was significantly longer in the study group than the control group (159.1 ± 28.6 versus 141.8 ± 51.0 days, P = 0.032).

CONCLUSIONS

SPECT/CT could improve the efficacy of botulinum toxin in CD. It could become a useful tool to aid botulinum toxin injection.

A methodological approach for botulinum neurotoxin injections to the longus colli muscle in dystonic anterocollis: A case series of 4 patients and a literature review

We review the current approaches and their feasibility to treat dystonic anterocollis by injecting longus colli muscle (LCo) with botulinum neurotoxin (BoNT) as well as present our personal experiences in this field compared with the findings from previously published studies. First, we searched the PubMed database for the publications reporting patients who received LCo injections for anterocollis; we also thoroughly examined the references included in each of the found publications. Second, we present and analyze our own experiences in injecting LCo under EMG guidance in patients with dystonic anterocollis due to heredodegenerative disorders. We found 11 publications describing administration of LCo injections for the treatment of dystonic anterocollis in a total of 28 patients with primary dystonia aged between 21 and 80 years. The mean age of our patients was 44.8 years with the mean anterocollis duration being 15 months. OnabotulinumtoxinA in a dose of up to 35 U per LCo muscle was not associated with the development of transient dysphagia. The mean percentage of patient satisfaction was 36.3%, and the mean duration of the beneficial effect was 2.5 months. All patients agreed to receive a repeat injection. We provide a set of empirically based suggestions on the current use of BoNT injections to LCo for managing anterocollis in outpatient clinics, including pretreatment work-up, injection technique, and dose range.

[99mTc]MIBI SPECT/CT for Identifying Dystonic Muscles in Patients with Primary Cervical Dystonia

PURPOSE

This study aimed to evaluate the usefulness of [^99mTc]sestamibi ([^99mTc]MIBI) single photon emission computed tomography (SPECT)/X-ray computed tomography (CT) imaging for the identification of dystonic muscles in primary cervical dystonia (PCD) patients who underwent botulinum neurotoxin type A (BoNT-A) therapy.

PROCEDURES

Thirty-six patients with PCD and 10 healthy subjects (control group) who underwent [^99mTc]MIBI SPECT/CT were enrolled. The image characteristics of dystonic muscles and normal muscles were evaluated. Muscle/background ratio (MBR) of six representative muscles was calculated for dystonic muscles in PCD group and normal muscles in control group. In PCD patients, target muscles injected with BoNT-A were selected by clinical evaluations and the results of needle electromyography (EMG) were considered as the gold standard. The sensitivity, specificity, and diagnostic efficacy of SPECT/CT were obtained from the receiver operator characteristic (ROC) curve.

RESULTS

Twenty-four PCD patients were included in our study eventually, because three PCD patients whose follow-up were lost and 9 PCD patients whose maximum reduction of Tsui scale scores was < 80 % were ruled out. Normal muscles of healthy subjects showed mild symmetrical radioactivity distribution, while in PCD patients, [^99mTc]MIBI uptake in dystonic muscles abnormally increased. The mean MBRs of dystonic muscles were significantly higher than those of normal muscles. The sensitivity, specificity, and area under the curve (AUC) of SPECT/CT were 93.2 %, 88.5 %, and 0.908, respectively.

CONCLUSIONS

Our study indicated that [^99mTc]MIBI SPECT/CT may be a useful method for identifying dystonic muscles and a guide to BoNT-A therapy in PCD patients.