**1. Introduction**

The word *dystonia* comes from the modern Latin *dys-* and the Greek *tonos* [1,2]. It is defined as a state of disordered tonicity, especially of muscle tissue. The word tone itself has musical connotations. It derives from the thirteeth-century old French *ton*, of the voice. The Latin word *tonus* meant a stretching, quality of sound, tone, or accent and in turn is derived from the Greek *tonos*, similarly translated as stretching, tension and raising of the voice and pitch. In modern usage, the word dystonic is applied to abnormal tension resulting in abnormal postures present in many disorders [2]. The definition of dystonia was recently revisited. In 2013, an interna‐ tional consensus committee proposed the following revised definition: *Dystonia is a movement disorder characterized by sustained or intermittent muscle contractions causing abnormal, often repetitive, movements, postures, or both. Dystonic movements are typically patterned, twisting, and may be tremulous. Dystonia is often initiated or worsened by voluntary action and associated with overflow muscle activation* [3].

The condition affects most voluntary muscles and is known as cervical dystonia (CD) when the neck muscles are affected. The term spasmodic torticollis was previously used for this syndrome, but it does not stress the dystonic nature of the disease [4]. Oromandibular dystonia (OMD) spasms of the masticatory, facial and lingual muscles result in repetitive and sometimes sustained jaw opening, closure, deviation or any combination of these, as well as abnormal tongue movements [5].

Various studies have shown that before treatment is started, some focal craniocervical dystonias such as spasmodic dysphonia and CD can be accompanied by a range of swallowing difficulties [6-15]. The incidence of dysphagia varies between 22 and 100 % of CD patients and is usually over 50 %. It increases significantly after botulinum toxin (BoNT) injection [8,11,12]. Dysphagia is suspected in 36 % of patients with CD on the basis of clinical assessment, and

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the incidence increases to 72 % on electrophysiological evaluation of oropharyngeal swallow‐ ing and after selective rhizotomy [8,9]. Similarly, dysphagia in patients with spasmodic dysphonia has been reported before and after treatment of this condition [13-15]. Because of the anatomical distribution of the affected muscles, OMD and co-existing oral-buccal-lingual (OBL) dyskinesias are associated with abnormal perioral, oral and lingual movements that can interfere with tasks such as chewing, swallowing and speaking, leading to social embarrass‐ ment and even eating disorders and weight loss. Eating dysfunction has been reported in 15.6 % of OMD cases [16]. Pharyngeal OMD often affects the pharyngeal constrictor muscles and can occur with spasmodic dysphonia. Choking and difficulty in swallowing are common complaints. After treatment of spasmodic dysphonia, there may be an unexpected improve‐ ment in pharyngeal dystonia. Treatment for pharyngeal constriction muscle dysfunction is nearly always associated with dysphagia [17].

Although new radiologic changes were observed in 50 % of CD patients following BoNT-A treatment, clinically only 33 % of the patients reported new dysphagia symptoms. The severity of the new dysphagia symptoms correlated strongly with the severity of new radiologic pharyngeal abnormalities [8].

In this chapter the role of dysphagia as a clinical symptom of cranio-cervical dystonia is discussed and the occurrence of dysphagia as a common adverse effect of treatment for dystonias is described.
