Hyoid muscle dystonia: A distinct focal dystonia syndrome.

INTRODUCTION: Adult-onset dystonias are often segmental in distribution and preferentially affect the craniocervical muscles. Here we describe an overlooked muscle group involved in craniocervical dystonia - the hyoid muscles. Dystonia of these muscles results in anterior neck tightness, speech changes, and dysphagia. METHODS: For this retrospective study we obtained a list of 55 patients who had received botulinum toxin injections into hyoid muscles between 1998 and 2013. Fifteen patients were identified to have an unusual dystonia affecting the hyoid muscles. RESULTS: Patients presented with a triad of speech resonance changes (100%), anterior neck tightness (86.6%), and dysphagia (73.3%). Ten (66.7%) patients presented with all three symptoms, while fourteen (93.3%) had at least two. Fourteen patients (93.3%) had a concomitant dystonia affecting the face or neck and eleven (73.3%) had a sensory trick. Exam universally showed contracted hyoid muscles. Some patients had professions or hobbies requiring prolonged use of vocal muscles such as teachers, singers, and musicians. Patients were often misdiagnosed and received unnecessary treatments. Patients underwent botulinum toxin injections into various hyoid muscles with benefit in 71% of patients but adverse effects in the same proportion. CONCLUSIONS: Hyoid muscle dystonia is a previously poorly characterized focal dystonia causing the triad of speech changes, anterior neck tightness, and dysphagia. Concomitant dystonia, sensory tricks, and visualization of contracted hyoid muscles were often present. Recognition of this disease may reduce unnecessary testing and treatments, and patients may benefit from botulinum toxin injections.

Development and characterisation of an experimental recurrent laryngeal nerve injury model for the study of viral gene therapy.

OBJECTIVES: To develop and characterise an experimental model of recurrent laryngeal nerve injury for the study of viral gene therapy. METHODS: Twenty rats underwent unilateral recurrent laryngeal nerve injury. After vocal fold mobility was observed, larynges were serially sectioned, and immunohistochemical techniques were employed to stain for neurofilament and motor endplates in order for a blinded investigator to determine the percentage of nerve-endplate contact, as a histological indicator of an intact neuromuscular connection. RESULTS: All animal procedures resulted in complete, ipsilateral vocal fold paralysis that recovered by three weeks. The mean nerve-endplate contact percentage was 11.6 per cent at one week, 53.9 per cent at two weeks, 88.6 per cent at three weeks, 81.7 per cent at four weeks and 86.6 per cent at five weeks. The differences between results at week one and week three were statistically significant (p < 0.01). The mean nerve-endplate contact percentage on the control side was 86.8 per cent. CONCLUSIONS: There was a dramatic, measurable decrease in nerve-endplate contact percentage following crush injury to the recurrent laryngeal nerve. Spontaneous recovery was observed by three weeks post-injury. This model will be used to investigate the potential therapeutic role of viral gene therapy for the treatment of recurrent laryngeal nerve injury.

Effects of hypoxia-reoxygenation on microvascular endothelial function in the rat hippocampal slice.

BACKGROUND: Cerebral ischemia and hypoxia may cause injury to both neuronal and vascular tissue. The direct effects of hypoxia on endothelial function in intraparenchymal cerebral arterioles are unknown. Using a modification of the rat brain slice preparation, allowing continuous imaging of these previously inaccessible vessels, microvessel dilation was evaluated before and after a brief hypoxic episode. METHODS: Rat brain slices were superfused with oxygenated artificial cerebrospinal fluid. Hippocampal arterioles were visualized using computerized videomicroscopy, and their diameters (range, 12-27 microm) were measured using image analysis. After preconstriction with prostaglandin F2alpha and controlled pH and carbon dioxide tension, graded concentrations of either acetylcholine (endothelium-dependent vasodilation) or sodium nitroprusside (endothelium-independent vasodilation) were given before and after a 10-min period of hypoxia. RESULTS: Sodium nitroprusside (100 microM) caused similar dilation before and after hypoxia (mean +/- SEM: 9.6 +/- 0.6% vs. 13.0 +/- 0.9%). Acetylcholine (100 microM) caused significantly less dilation (P < 0.05) after hypoxia (mean +/- SEM: 9.3 +/- 1.8% vs. 3.6 +/- 1.2%). The decreased acetylcholine-induced dilation after hypoxia was not reversed by pretreatment with L-arginine (1 mM), the precursor of nitric oxide (mean +/- SEM: 8.8 +/- 1.3% vs. 4.4 +/- 0.7%). CONCLUSIONS: Even brief periods of hypoxia may cause endothelial dysfunction in intraparenchymal cerebral arterioles. This does not seem to be related to a deficiency of the nitric oxide substrate, L-arginine. Endothelial dysfunction and impaired endothelium-dependent dilation of microvessels may decrease oxygen delivery and increase neuronal injury during cerebral hypoxia-reoxygenation.