4: Cervical Dystonia

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CHAPTER 4

Cervical Dystonia

Moon Suk Bang, MD, PhD

Shi-Uk Lee, MD, PhD

Synonyms

Spasmodic torticollis

Idiopathic torsion dystonia

Symptomatic torsion dystonia

ICD-9 Codes

333.6  Idiopathic torsion dystonia

333.7  Symptomatic torsion dystonia

ICD-10 Codes

G24.1  Idiopathic torsion dystonia

G24.2  Symptomatic torsion dystonia

Definition

Idiopathic cervical dystonia, the most common form of adult-onset focal dystonia, is twisting and turning of the neck caused by abnormal involuntary muscle contractures [1]. Cervical dystonia has also been known as spasmodic torticollis, which implies head jerking or neck spasms. However, these features are absent in 25% to 35% of patients with this condition [2]. Furthermore, the term spasmodic torticollis fails to emphasize the dystonic nature of the condition and the frequent association of cervical dystonia with dystonia in adjacent or remote body parts.

The incidence of cervical dystonia has been estimated at 1.07 per 100,000 person-years [3]. Women are affected 1.5 to 1.9 times more often than men are [2,4]. In 70% to 90% of cases, the disease begins between the fourth and sixth decades, with a peak incidence in the fifth decade of life [5].

The pathogenetic mechanisms are unclear, but increasing evidence suggests that cervical dystonia is influenced by genetic factors. Many patients with cervical dystonia have a family history [2]. Several gene loci, such as DYT1, DYT6, and DYT7, have recently been reported to be associated with cervical dystonia [6].

Cervical dystonia has also been reported to develop secondary to head, neck, and shoulder trauma [7]. The role of the sensory system is important in the pathogenesis of this condition (see section on symptoms) [8]. Impaired inhibition of sensory Ia afferent fibers, impairment of central sensory pathways, and increased spindle responsiveness secondary to overactive gamma spindle efferent fibers have been proposed as pathogenic mechanisms [9]. Other proposed mechanisms are vestibular impairment, dysfunction of the subcortical-cortical motor network, and dopaminergic dysfunction [9].

The natural course of dystonia has been reported [10], and in 68.1% of patients, dystonia remained focal. Progression of dystonia to sites other than the neck was noted in 31.9% of patients. The only risk factor for progression of dystonia to other body parts was longer duration of the disease. The rate of spontaneous remission was 20.8%. In most of the cases (87%), the remission occurred during the first 5 years after the onset of symptoms. The remission was sustained in 60% of the patients, and in 40% of the patients who had experienced remission, the disorder relapsed (nonsustained remission). The duration of the disease before remission was an important discriminating factor between sustained and nonsustained remission. The patients who experienced nonsustained remission had all done well within the first 2 years of the disorder; whereas in the patients who had sustained remission, the duration of dystonia before remission was more than 2 years.

Symptoms

Symptoms usually begin insidiously with complaints of a pulling or drawing in the neck or an involuntary twisting or jerking of the head. In most patients, the manifesting symptoms are sensory in nature (described variously as pain, pulling, or stiffness) or a degree of head rotation or deviation, with jerking and tremor of the head being distinctly less common complaints [2,4,11]. In 83% of patients, head deviation was constant rather than jerky (i.e., nonspasmodic) and demonstrated some degree of rotation (97%). Only a fraction of patients showed head jerks (35%) and neck spasms (37%), which are the cardinal features of “spasmodic” torticollis [2].

Several provocative and palliative factors are characteristic of idiopathic dystonia. Most notable is the use of a sensory trick or geste antagoniste. Gently touching the chin, back of the head, or top of the head relieves the symptoms. The use of sensory tricks to keep the head in the body midline position was reported by 88.9% of patients in one series [12]. The physiologic mechanism of sensory tricks remains unknown. Other effective maneuvers include leaning against a high-backed chair, placing something in the mouth, and pulling the hair. Early in the illness, these tricks are helpful in most patients, but they tend to lose effectiveness as the disease progresses. Less common palliative factors are relaxation, alcohol, and “morning benefit,” when symptoms are improved for a while after waking. Cervical dystonia is commonly exacerbated by activity (e.g., walking), fatigue, or stress [13].

Pain is a major source of disability in two thirds to three quarters of patients with cervical dystonia [2,3,14,15]. Pain severity was related to the intensity of dystonia and muscle spasms [2] but not to the duration of cervical dystonia and severity of motor dysfunction [14]. Pain was commonly described as tiring, radiating, tugging, aching, and exhausting [14].

Physical Examination

Inspection of the patient’s head posture is enough for the diagnosis of cervical dystonia. A wide variety of abnormal head and neck postures can occur (Fig. 4.1). Rotational torticollis is a rotation of the chin around the longitudinal axis toward the shoulder. Laterocollis is a rotation of the head in the coronal plane, moving the ear toward the shoulder. Anterocollis and retrocollis are rotations of the head in the sagittal plane; anterocollis brings the chin toward the chest, and retrocollis elevates the chin and brings the occiput toward the back. By convention, the direction of the rotation is defined by the chin, so right-turning torticollis means that the chin is turning to the right. There may also be sagittal or lateral deviation of the base of the neck from the midline [13]; 66% to 80% of patients present with a combination of these movements [2,4]. The most common component of complex deviations is rotational torticollis, followed by head tilt, retrocollis, and anterocollis. Isolated deviations (e.g., in a single plane) are seen in less than one third of patients. Notably, idiopathic cases of pure anterocollis are extremely uncommon. There is no statistically significant preponderance of right or left deviation [2,4,5,16]. The abnormal posture is present for more than 75% of the time in most patients, but findings may change in nature and directional preponderance over time [2].

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FIGURE 4.1 Drawing of a patient with left rotational torticollis and laterocollis showing prominent left rotation, left tilt, and shoulder elevation.

Many patients have signs of dystonia involving other body segments at the time of presentation. Extracervical dystonia is found in 10% to 20% of patients [2,4]; the jaw (oromandibular), eyelids (blepharospasm), arm or hand (writer’s cramp), and trunk (axial) are the most frequently affected parts. A postural or kinetic hand tremor is found on physical examination in up to 25% of patients.

Although the term spasmodic torticollis implies head jerking or neck spasms, this feature is absent in 25.33% of patients. The adjectives spasmodic and spastic are misleading because there is no evidence that cervical dystonia is a spastic disorder or caused by dysfunction of the pyramidal tracts. Furthermore, the movements are not always spasmodic but may be sustained.

Although abnormal head position is enough for the diagnosis, physical examination in patients with cervical dystonia must be focused on detection of “pseudodystonia” secondary to structural abnormalities [17]. Normal findings in a complete neurologic examination are mandated to exclude secondary dystonia. The presence of corticospinal, sensory, cerebellar, oculomotor, or cortical signs with cervical or extracervical dystonia suggests secondary dystonia.

Functional Limitations

Functional limitations due to cervical dystonia are found in almost all patients (99% of 220 patients) [16

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