Dystonia
Classification by Etiology (2)
Primary Dystonia (idiopathic) Secondary Dystonia
Primary dystonia
Primary dystonia almost always begins by affecting a single part of the body (focal) which then gradually generalizes
Dystonia
A neurological syndrome characterized by involuntary, prolonged twisting and turning movements that are frequently stereotyped and repetitive, and produce characteristic abnormal postures 13 motor features
Motor Circuit Abnormalities - Primary Dystonia
Abnormal CNS function in nearly every region of CNS relevant for motor control and sensorimotor integration Including SC, brainstem, cerebellum, basal ganglia, and cerebral cortex Motor system/circuit disorder, not abnormality of a particular strucutre
Mechanisms of Brain Dysfunction
Abnormal plasticity Focal dystonias associated with significant bilateral increase in grey matter in cortical area representing body part with dystonia Deficient inhibition demonstrated in cortex, brainstem, and SC
Overflow Dystonia
Actions in other parts of the body can induce dystonic movements of the primarily affected body part
Segmental Dystonia
Affects one or more contiguous body parts
Focal Dystonia
Affects single body part
Generalized
Affects the entire body
Motor Circuit Abnormalities - Secondary Dystonia
Associated with lesions of putamen or globus pallidus Can also result from lesions of the caudate, thalamus, brainstem, (and cerebellum, frontal/parietal cortex) Motor system/circuit disorder, not abnormality of a particular strucutre
Coexist
Can coexist with dystonic tremor or dystonic myoclonus
Secondary Dystonia
Caused by a known motor system insult - such as trauma, neurodegenerative disease, cerebral palsy, or exposure to dopamine receptor antagonists Usually begins with dystonia at rest (unlike primary dystonia)
Neurochemical Abnormalities
Deficient GABA levels Decreased dopaminergic neurotransmission in putamen in some types of dystonia ACh/dopamine balance alterations
Early Onset (childhood) Dystonia
Dominantly inherited Often begins in arm or leg Can spread widely Resulting in severe motor disability
Paradoxical Dystonia
Dystonia at rest improves by talking or by voluntary active movement.
Affect voluntary muscles
Dystonic movements can affect practically all voluntary muscles prolonged contraction of agonist and antagonist muscles causes affected body part to twist
Action Dystonia
Dystonic movements frequently exacerbated (worsen) by voluntary action
Classification by Distribution (5)
Focal Segmental Multifocal Hemidystonia Generalized
Treatment
Focus on etiology because (1) Management can be difficult, and (2) Patients do not consistently respond to one type of therapy 4 Types: Oral medication Chemodenervation (botox injection) Surgical Therapy Other Therapies
Hemidystonia
Involves only half of the body
Multifocal Dystonia
Involves two or more non-contiguous body parts
Sensory Tricks
Movements can be suppressed by tactile or proprioceptive "sensory tricks"
Neurophysiologic mechanisms
Muscles are controlled by anterior horn cells (amn) There is a reduced pre-synpatic inhibition of muscle afferent input to the IN-interneurons Deficient cortical inhibition therefore resulting in increased excitation in the primary motor cortex has also been documented
Primary Dystonia (idiopathic)
Occurs as an isolated symptom in the absence of recognizable brain damage or exogenous cause Categorized according to age of onset
Task-Specific Dystonia
Only occurs during specific actions (ex: Writing)
Pain is uncommon
Pain is not very common, except in cervical dystonia
Fixed Abnormal Posture
Severe dystonia can lead to a fixed abnormal posture at rest
Stereotyped Patterns
Stereotypic patterns of movement arise from repeated involvement of the same group of muscles
Late Onset (adult) Dystonia
Usually idiopathic Begins in face or neck Less likely to spread
Worsen/Suppressed
Worsens with fatigue and stress Suppressed with sleep, hypnosis, or relaxation
Age of onset
Younger the age of onset, the more likely dystonia to spread