Spasmodic torticollis is an extremely painful chronic neurological movement disorder causing the neck to involuntarily turn to the left, right, upwards, and/or downwards. The condition is also referred to as "cervical dystonia". Both agonist and antagonist muscles contract simultaneously during dystonic movement. Causes of the disorder are predominantly idiopathic. A small number of patients develop the disorder as a result of another disorder or disease. Most patients first experience symptoms midlife. The most common treatment for spasmodic torticollis is the use of botulinum toxin type A.
Signs and symptoms Initial symptoms of spasmodic torticollis are usually mild. Some feel an invisible tremor of their head for a few months at onset. Then the head may turn, pull or tilt in jerky movements, or sustain a prolonged position involuntarily. Over time, the involuntary spasm of the neck muscles will increase in frequency and strength until it reaches a plateau. Symptoms can also worsen while the patient is walking or during periods of increased stress. Other symptoms include muscle hypertrophy, neck pain, dysarthria and tremor. Studies have shown that over 75% of patients report neck pain, and 33% to 40% experience tremor of the head.
Pathophysiology
The pathophysiology of spasmodic torticollis is still relatively unknown. Spasmodic torticollis is considered neurochemical in nature, and does not result in structural neurodegenerative changes. Although no lesions are present in the basal ganglia in primary spasmodic torticollis, fMRI and PET studies have shown abnormalities of the basal ganglia and hyper activation of the cortical areas. Studies have suggested that there is a functional imbalance in the striatal control of the globus pallidus, specifically the substantia nigra pars reticulata. The studies hypothesize the hyper activation of the cortical areas is due to reduced pallidal inhibition of the thalamus, leading to over activity of the medial and prefrontal cortical areas and under activity of the primary motor cortex during movement. It has also been suggested that the functional imbalance is due to an imbalance of neurotransmitters such as dopamine, acetylcholine, and gamma-aminobutyric acid. These neurotransmitters are secreted from the basal ganglia, traveling to muscle groups in the neck. An increase in neurotransmitters causes spasms to occur in the neck, resulting in spasmodic torticollis. Studies of local field potentials have also shown an increase of 4–10 Hz oscillatory activity in the globus pallidus internus during myoclonic episodes and an increase of 5–7 Hz activity in dystonic muscles when compared to other primary dystonias. This indicates that oscillatory activity in these frequency bands may be involved in the pathophysiology of spasmodic torticollis.
Diagnosis
The most commonly used scale to rate the severity of spasmodic torticollis is the Toronto Western Spasmodic Torticollis Rating Scale (TWSTRS). It has been shown that this rating system has widespread acceptance for use in clinical trials, and has been shown to have "good interobserver reliability." There are three scales in the TWSTRS: torticollis severity scale, disability scale, and pain scale. These scales are used to represent the severity, the pain, and the general lifestyle of spasmodic torticollis.
Classification Spasmodic torticollis is a form of focal dystonia, a neuromuscular disorder that consists of sustained muscle contractions causing repetitive and twisting movements and abnormal postures in a single body region. There are two main ways to categorize spasmodic torticollis: age of onset, and cause. The disorder is categorized as early onset if the patient is diagnosed before the age of 27, and late onset thereafter. The causes are categorized as either primary (idiopathic) or secondary (symptomatic). Spasmodic torticollis can be further categorized by the direction and rotation of head movement.
Primary Primary spasmodic torticollis is defined as having no other abnormality other than dystonic movement and occasional tremor in the neck. This type of spasmodic torticollis is usually inherited. Studies have shown that the DYT7 locus on chromosome 18p in a German family and the DYT13 locus on chromosome 1p36 in an Italian family is associated with spasmodic torticollis. The inheritance for both loci is autosomal dominant. These loci are all autosomal dominantly inherited with reduced penetrance. Although these loci have been found, it is still not clear the extent of influence the loci have on spasmodic torticollis.
Secondary When other conditions lead to spasmodic torticollis, it is said that the spasmodic torticollis is secondary. A variety of conditions can cause brain injury, from external factors to diseases. These conditions are listed below:
Central nervous system tumor Central pontine myelinolysis Cerebrovascular diseases Drug induced Infectious or post infectious encephalopathies Kernicterus Metabolic Paraneoplastic syndromes Perinatal (during birth) cerebral injury Peripheral or central trauma Toxins Secondary spasmodic torticollis is diagnosed when any of the following are present: history of exogenous insult or exposure, neurological abnormalities other than dystonia, abnormalities on brain imaging, particularly in the basal ganglia.
Head positions To further classify spasmodic torticollis, one can note the position of the head.
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