Special IssueNeuroimaging Characteristics of Patients with Focal Hand Dystonia
Section snippets
Characteristics of FHd, Clinical Management, and the Role of Neuroimaging
Although the critical problem is decreased motor control, FHd may also be associated with decreased range of motion or hyperflexibility, decreased strength or excessive strength and muscle hypertrophy, and/or impaired sensory processing. It is primarily the impairment of motor control that leads to an inability to perform the associated task and, in some cases, other activities of daily living, such as brushing one's teeth, shaving, cutting nails, or buttoning a shirt. Current conservative
Sensorimotor Learning Hypothesis: Evidence for Neuroplasticity in Focal Dystonia
Even though FHd is considered multifactorial, one prevailing hypothesis for the development of FHd is based on aberrant sensorimotor learning. This hypothesis suggests that highly repetitive, rapid, attenuated movements associated with the onset of FHd result in maladaptive changes in the representation of the digits within the somatosensory and motor cortices of the brain.8, 9 Degradation of normal somatotopy occurs as a result of an inability of the brain to distinguish between
Somatosensory Processing
Although no definitive clinical test exists to diagnose FHd, impairments in tactile processing (likely as a result of reorganization in S1) are evident in this population when these individuals are tested for simple sensory function. Specifically, patients with FHd exhibit deficits in fine spatial and temporal somatosensory processing. Spatial discrimination thresholds are increased in dystonia patients, for both affected and unaffected hands.15, 16
Even in clinical measures of spatial
Motor Processing
Although some aspects of sensorimotor integration (such as sensory gating) may remain uncompromised in patients with focal dystonia, it is well established that aberrant patterns of activity exist in the motor system of these patients, and this activity also contributes to the condition. Motor processing is complex and involves the preparation, initiation, and execution of movement followed by sensory feedback. During movement preparation, regions of the frontal lobe including premotor cortex
Effects of Training
Knowledge about the underlying neural pathophysiology of FHd obtained through animal models and neuroimaging techniques have allowed clinicians to develop successful behavioral treatment regimens. Some of these therapeutic interventions, such as constraint-induced movement therapy41 and learning-based sensorimotor retraining13, 42 have been successfully applied with the ultimate goal of improving the sensory representations of the affected limbs in the brain. Completion of these physical
The Role of Neuroimaging in the Diagnosis of FHd
Although the behavioral manifestations of FHd are evident to the clinician, limited testing is available to confirm such a diagnosis. A diagnosis of FHd is typically generated through behavioral testing by the clinician; however, neuroimaging tools can and do play a powerful role in verification of the disorder.3 Although some genetic mutations, specifically those of the DYT1 and DYT7 genes, are associated with the development of a focal dystonia,51, 52, 53 many carriers of these genes do not
Future Directions for Neuroimaging and FHd
Although many advances in the treatment of FHd have been made through insights provided by neuroimaging, a considerable amount of work remains to be done in linking these motor impairments to underlying anatomical and physiological mechanisms. It is challenging to evaluate the extent to which changes in brain anatomy and function are the result of primary versus secondary effects of the disorder, and this becomes critical to understand in the development of behavioral treatment regimens
Conclusion
Therapists, neuroscientists, neuroradiologists, neurosurgeons, and neurologists have an exciting opportunity to work together to discover more about the risk factors, etiology, and effective intervention paradigms to facilitate recovery of normal motor control in patients with FHd. Although today, the application of functional neuroimaging is most commonly used for research purposes, neuroimaging may begin to play a more important role in objectively documenting and guiding appropriate
Quiz: Article # 122
Record your answers on the Return Answer Form found on the tear-out coupon at the back of this issue. There is only one best answer for each question.
- #1.
The article suggests that
- a.
emotional disturbances are the root cause of focal hand dystonia
- b.
sub clinical closed head trauma is the most common root cause of focal hand dystonia
- c.
the brain is at the center of the disturbances that play into the clinical manifestation of focal hand dystonia
- d.
the peripheral nervous system is the primary locus of the
- a.
References (66)
- et al.
Writer's cramp
Trends Neurosci
(1990) - et al.
Task-specific plasticity of somatosensory cortex in patients with writer's cramp
Neuroimage
(2003) - et al.
Movement preparation and motor intention
Neuroimage
(2001) - et al.
Regional cerebral blood flow correlates of the severity of writer's cramp symptoms
Neuroimage
(2004) Direct demonstration of the effect of lorazepam on the excitability of the human motor cortex
Clin Neurophysiol
(2000)- et al.
Impaired modulation of corticospinal excitability following subthreshold rTMS in focal hand dystonia
Hum Mov Sci
(2004) - et al.
Treatment effectiveness of patients with a history of repetitive strain injury and focal hand dystonia: a planned, prospective follow-up study
J Hand Ther
(2000) - et al.
Neuromagnetic fields reveal cortical plasticity when learning an auditory discrimination task
Brain Res
(1997) - et al.
Effect of sensory discrimination training on structure and function in patients with focal hand dystonia: a case series
Arch Phys Med Rehabil
(2003) Brain cortical activation during guitar-induced hand dystonia studied by functional MRI
Neuroimage
(2000)
Writer's cramp—a focal dystonia
Brain
Focal hand dystonia
Pract Neurol
Botulinum toxin therapy of writer's cramp
Eur J Neurol
Effective behavioral treatment of focal hand dystonia in musicians alters somatosensory cortical organization
PNAS
Limb immobilization for the treatment of focal occupational dystonia
Neurology
Motor training as treatment in focal hand dystonia
Mov Disord
Sensory representation abnormalities that parallel focal hand dystonia in a primate model
Somatosens Mot Res
A primate genesis model of focal hand dystonia and repetitive strain injury: 1. Learning-induced dedifferentiation of the representation of the hand in the primary somatosensory cortex in adult monkeys
Neurology
Magnification, receptive-field area, and “hypercolumn” size in areas 3b and 1 of somatosensory cortex in owl monkeys
J Neurophysiol
Abnormal cortical sensory activation in dystonia: an fMRI study
Mov Disord
Human brain mapping in dystonia reveals both endophenotypic traits and adaptive reorganization
Ann Neurol
Somatosensory representation of the digits in clinical performance in patients with focal hand dystonia
Am J Phys Med Rehabil
Computational model of the role of sensory disorganization in focal task-specific dystonia
J Neurophysiol
Abnormalities of spatial and temporal sensory discrimination in writer's cramp
Mov Disord
Abnormalities of spatial discrimination in focal and generalized dystonia
Brain
The basal ganglia are hyperactive during the discrimination of tactile stimuli in writer's cramp
Brain
Sensory dysfunction associated with repetitive strain injuries of tendonitis and focal hand dystonia: a comparative study
J Ortho Sports Phys Ther
Sensory discrimination capabilities in patients with focal hand dystonia
Ann Neurol
Dynamic organization of the somatosensory cortex induced by motor activity
Brain
Activation of cortical and cerebellar motor areas during executed and imagined hand movements: an fMRI study
J Cogn Neurosci
Cerebral activation patterns in patients with writer's cramp: a functional magnetic resonance imaging study
J Neurol
Basal ganglia activity remains elevated after movement in focal hand dystonia
Ann Neurol
Increased basal-ganglia activation performing a non-dystonia-related task in focal dystonia
Eur J Neurol
Cited by (22)
Treatment of Dystonia: Medications, Neurotoxins, Neuromodulation, and Rehabilitation
2020, NeurotherapeuticsAssessment of hand functions in patients with idiopathic cervical dystonia
2020, Human Movement ScienceCitation Excerpt :Recently, it has become clear that the role of basal ganglia extends beyond motor control into cognitive and sensory functions and sensorimotor integration (Tinazzi, Fiorio, Fiaschi, Rothwell, & Bhatia, 2009. Data from neuroimaging and electrophysiological experiments in dystonic patients also point to functional impairments in premotor and primary sensorimotor cortical areas as well as aberrant sensorimotor integration, which is believed to be a significant element in the occurrence of focal dystonia (Hinkley, Webster, Byl, & Nagarajan, 2009; Tinazzi, Fiorio, et al., 2009; Tinazzi, Squintani, & Berardelli, 2009). It has been shown that patients with idiopathic dystonia show sensorimotor dysfunction associated with sensorimotor circuits, involving both the cortico-striatal and thalamo-cortical pathways. (
Repetitive Stress Pathology
2016, Pathology and Intervention in Musculoskeletal RehabilitationSensorimotor network in cervical dystonia and the effect of botulinum toxin treatment: A functional MRI study
2011, Journal of the Neurological SciencesCitation Excerpt :Recently, it has become clear that the role of the basal ganglia extends beyond motor control into cognitive and sensory functions as well as in sensorimotor integration [3]. Converging data from both functional imaging and electrophysiological experiments in dystonic patients also suggest functional abnormalities in premotor and primary sensorimotor cortical areas together with aberrant sensorimotor integration, which is considered to be a crucial factor for the development of focal dystonia [3–5]. However, the published studies differ in terms of observed hypo- and hyperactivation in these cortical areas.
Complex dystonias: an update on diagnosis and care
2021, Journal of Neural Transmission