Dystonia

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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


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