movement disorders Flashcards
JVIM 2021
main output structures of the basal nuclei
endopedoncular nucleus, substancia nigria
direct pathway of movement control
dopaminergic innervation of caudate/putamen from the substancia nigria increase inhibition of the subsantcia nigria/EPN by activating D1 recept on gabapergic medium spiny neuron. this release the thalamus from tonic inhibition. This increase the excitatory feedback from the thalamus to motor cortex and caudate/putamen
PROMOTE MOVEMENT
dopaminergic receptor in motor control
- D1 recept: increase glutamatergic activity, direct pathway
- D2 recept: decrease glutaminergic activity
indirect pathway of movement control
medium spiny neurons inhibit GABAergic neuron in globus palidus. This release the subthalamic nucleus from inhibition, increasing excitation of SN/EPN, and in turn inhibition of thalamus. Decrease thalamic excitation of motor cortex and caudate/putamen
INHIBITS MOVEMENT
dopamine promote or inhibit movement ?
promote: excite medium spicy neuron through D1 recep in direct pathway, inhibit through D2 in indirect
role of cerebellum in pathophysiology of hyperkinetic disorder
lateral cerebellar nucleus conected to striatum via intralaminar nucleus of thalamus
clinical signs resulting from peripheral nerve hyperexcitability
fasciculation, myokymia, neuromyotomia, cramps, tentany, tetanus
define myokymia (EMG, channel, persistance with sleep)
continuous contraction of facial/limb myofibers, often exhibiting an vermicular movement of the skin overlying the affected muscle.
EMG: burst of single motor unit potential firing at 5-150 Hz
believed to result from abnormal K channel function.
Persist during sleep
define tremors
involontary rythmic oscillatory movement of a body part with symmetric velocity in both direction of movement.
frequency 1-12 Hz
classification of tremors
- rest tremors (not in animal)
- action tremors: postural (orthostatic, idiopathic head tremors, begnin/idiopathic/rapid postural tremors) and kinetic (intention tremors)
define neuromyotomia (EMG)
generalized muscle stiffness with delayed relaxation, often resulting in collapse. Muscle rippling. May be precipited by stress/ excitement
EMG: high frequency (150-300 Hz) burst of decrementing discharge of motor unit potentials with abrubt onset/offset. Spontaneous or initiated by needle movement, volontary contraction percussion of the nerve
Persist during sleep, can be blocked by neuromuscular bloking agent
define cramp
sudden, severe, and involuntary muscle contraction or over‐shortening that is generally temporary and benign. Can cause mild‐to‐excruciating pain, and immobility of the affected muscle(s). Onset is usually sudden, and resolves on its own over a period of several seconds, minutes, or hours.
reported with hypoadrenocorticism
EMg: repetitive firing of motor unit action potential at high rate (up to 150 Hz). Number of MU activated and frequency of discharge increase gradually and subside gradually with irregular firing pattern.
Electrically silent cramp with strenous/ischemic exercice in metabolic myopathy associated with defect glycolysis/glycogenolysis
define tetany
Sustained muscle contraction, usually involving extensors muscles. No relaxation is noted. May be accompanied by sensory changes (eg, hypocalcemia‐induced tetany).
define tetanus
Severe, sustained muscle contraction resulting from impairment of glycine release within the ventral gray matter of the spinal cord resulting from exotoxin release associated with Clostridium tetani infections.
epileptic and non epileptic myoclonus
Epileptic:
1. Lafora
2. neuronal ceroid lipofuscinosis
3. feline audiogenic reflex seizure
4. juveniel myoclonic epilepsy in Rhodesian Ridgebacks
Non epileptic:
1. Canine distemper virus
2. Startle disease
3. Hemifacial spasm
define myoclonus
A sequence of repeated, variably rhythmic, brief shock‐like jerks resulting from the sudden involuntary contraction or relaxation of 1 or more muscles. Generates movement of the affected body part. Differs from a startle response in that myoclonic movements frequently occur independent of a sudden stimulatory input and occur repetitively. May be precipitated or worsened by movement, stress. May occur during sleep.
causes of generalised peripheral nerve hyperexcitability
hereditary, immune-mediated, paraneoplasic, polyneuropathies, motor neuron diseases, neurodegenerative, metabolic, begnin (stress/exercise), toxicity
define athetosis
Prolonged slow involuntary contraction of the distal part > trunk muscles resulting in nonrhythmic bending/sinuous/writhing movements. May occur at rest or may be worsened or precipitated by movement.
define ballism
An abrupt involuntary contraction of proximal limb muscles resulting in large‐amplitude flailing/flinging movements of the limb(s); typically unilateral.
define chorea
An abrupt, irregular, and unsustained low‐amplitude contraction of muscle groups, particularly distal muscles resulting in 1 or more discrete movements. Similar in distribution to athetosis but faster and larger amplitude. Not characterized by an inserted posture (as in dystonia) but rather an inserted movement.
define dystonia
A sustained, slow, involuntary contraction of agonist and antagonist muscles of a body region producing abnormal postures and/or involuntary movement of portions of the body along a longitudinal axis. May appear as a twisted posture of the limbs, trunk, or neck. Associated with varying durations of muscle contracture (arrhythmic). Only occurs in wakeful state.
define fasciculation
A brief spontaneous contraction resulting from the spontaneous activation of a small number of muscle fibers, often causing a vermicular movement under the skin.
define myoclonic tremor
Likely replaced by term rhythmic myoclonus
brief shock‐like myoclonic movements occurring with a defined unidirectional fast phase (positive or negative) and a slower recovery phase.
define myotomia
A disturbance in muscle relaxation after voluntary contraction or percussion. Is most noticeable after a period of rest, and improves with continued activity. Frequently results in noticeable hypertrophy of the affected muscles and may lead to diminished joint flexion when walking
