PSYCH 415--Notes for Movement Disorders

1. positive motor sign - something added; something not normally present
2. negative motor sign - something taken away that should be present
3. spasticity - muscle hypertonicity (stiffness due to excessive muscle contraction; spastic paralysis if severe)
4. ataxia - loss of coordination and equilibrium (a "drunken" appearance)
5. akinesia - inability to initiate movement
6. rigidity - resistance to passive movement (due to excess muscle tension)
7. chorea (choreiform movements) - involuntary "dance-like" movements
8. athetosis - involutary, slow, writhing movements usually of the hands and arms or feet and legs, often restricted to one side of the body, and sometimes accompanied by chorea (choreoathetosis)
9. myoclonus - sudden, involuntary muscle contractions leading to jerks
10. tremor - rhythmic shaking
11. dystonia - involuntary muscle contractions leading to twisting movements and adoption of strange postures
12. tics - sudden, repetitive, nonrhythmic movements, behaviors, or vocalizations
13. gesticulations - peculiar and inappropriate gesturing
14. mannerism - a peculiar or unusual mode of movement that becomes characteristic of a person's behavior
15. compulsions - irresistible urges to repeat certain acts
16. akathisia - unpleasant sensations of inner restlessness that result in the inability to sit still or remain motionless

1. monosynaptic stretch reflex - adjustment to changed load; control of posture
2. gamma motor system - maintenance of muscle tone, etc.
3. polysynaptic reflexes - such as flexor crossed extensor reflexes

1. anatomy of the motor system - see big scary diagram no. 1
   1. pyramidal motor system - thru the "pyramids" of the medulla
      1. primary motor cortex - precentral gyrus of frontal lobe
      2. pyramidal tract (aka the corticospinal tract) - upper motor neurons
      3. spinal motor neurons - lower motor neurons
         1. alpha motor neurons - to the muscle fibers (movement)
         2. gamma motor neurons - to the muscle spindles (muscle tone)
      4. corticobulbar (corticopontine) tracts - onto cranial nerve nuclei, and relay to the cerebellum
   2. extrapyramidal system - everything else
      1. basal ganglia - modulation (but not direct control) of movement (and probably also certain cognitive functions - how closely is "thinking" related to movement?)
         1. neostriatum - caudate nucleus putamen
         2. paleostriatum - globus pallidus (internal and external segments)
      2. ventral thalamus - relays to cortex from basal ganglia, cerebellum, etc.
      3. subthalamic nucleus
      4. substantia nigra (pars compacta) - origin of DA fibers of the nigrostriatal tract (dopaminergic input to neostriatum)
      5. cerebellum - balance, coordination, motor conditioning, correction of ongoing movements that deviate from their intended course
      6. pons - partly, a relay into the cerebellum via the middle cerebellar peduncle
      7. red nucleus - relays from cerebellum to thalamus but also is the origin of a descending motor pathway (rubrospinal tract)
      8. inferior olive - relays from spinal cord to cerebellum
      9. descending pathways
         1. rubrospinal tract - movement of forearms and hands
         2. tectospinal tract - coordination of eye movements with body movement
         3. vestibulospinal tract - posture
         4. reticulospinal tract - walking and rhythmic movements
         5. olivospinal tract - general modulation of muscle flexion (?)
2. organization of movement control in the cortex - see big scary diagram no.2
   1. the motor cortex - motor homunculus ("somatotopic" organization)
      1. a disproportionate amount of the motor cortex is devoted to the face (esp. the muscles of speech), the hands, and the feet - "distal" muscles involved in fine motor control are represented
      2. primary input is from the frontal association cortex (motor association cortex) just anterior to the primary motor cortex
         1. secondary motor (premotor) cortex - planning
         2. dorsolateral prefrontal association cortex - decisions to initiate voluntary movements
         3. frontal eye fields - controls eye movement ("plans")
         4. supplementary motor area - planning
         5. somatosensory cortex - snesory feedback from touch
      3. comment on mirror neurons
      4. FACx, in turn, receives input from the posterior sensory association cortexes of the parietal, occipital, and temporal (POT) lobes
         1. parietal association cortex (PACx)
            • keeps track of the positions of the parts of the body based on somatosensory, visual, and auditory information
            • also keeps track of the positions of objects in space
            • directs attention
            • damage causes apraxia and contralateral neglect (later)
         2. occipital association cortex (OACx) - vision
         3. temporal association cortex (TACx) - vision and audition
         4. primary somatosensory cortex (PSCx) - body (somato-) sensation
      5. the importance of feedback - movements are regulated and fine tuned by sensory feedback from all senses but most quickly by the body senses
         1. tendon and joint senses - via the cerebellum
         2. touch sensation - directly (stereognosis, the process of identifying objects by touch)
3. descending motor pathways
   1. the corticospinal pathways
      1. dorsolateral (or lateral) corticospinal tract - the "big one"
         1. the pyramidal tract - direct
         2. decussates (crosses over) in the lower medulla - damage to the right side of the brain in the pyramidal system causes movement disability on the left side of the body
         3. originates substantially in the primary motor cortex and controls contralateral distal limb muscles and esp. fine motor control
         4. Betz cells - very large cells in the motor cortex that send fibers down to the lower spinal cord where they control the muscles of the legs and enable rapid, voluntary control of the leg muscles
         5. some synapse on spinal interneurons, but many synapse directly on the alpha motor neurons (only in primates)
      2. dorsolateral corticorubrospinal tract - indirect (relayed)
         1. descends from the motor cortex and synapses in the red nucleus
         2. efferents from the red nuc. cross over and synapse in cranial nerve nuc. that give rise to cranial nerves controlling the facial muscles
         3. other efferents from the red nuc. continue continue into the spinal cord where they rejoin the pyramidal tract and control contralateral arms, legs, and hands
      3. ventromedial (or ventral or anterior) corticospinal tract
         1. uncrossed, direct
         2. controls ipsilateral trunk and proximal limb muscles
   2. the ventromedial pathways
      1. anatomically the ventral corticospinal tract goes here
      2. ventromedial cortico-brainstem-spinal tract
         1. bilateral control, relayed
         2. vestibulospinal tract - balance, posture (also receives input from the cerebellum)
         3. tectospinal tract - coordination of trunk with eye movements
         4. reticulospinal tracts - walking and other rhythmic, repetitive movements; muscle tone and tension

1. first some terms
   1. Babinski sign - a reflex often tested in infants to determine if the pyramidal system in the brain is "on line"
   2. testing the Babinski reflex
   3. spastic paralysis - excessive muscle tension and overactive tendon reflexes, sometimes to the point of disablement
   4. flaccid paralysis - paralysis due to absense of muscle tone and tendon reflexes
   5. muscle fasciculations - little twitches or tics in one or a few muscle fibers
2. see big scary diagram no. 3
3. an example of lower motor neuron disease - poliomyelitis
   1. aka "polio" - probably the most feared disease on the planet in the early 20th century
   2. virtually wiped out by the polio vaccine - Jonas Salk on the cover of Time, March 29, 1954
   3. there was always a kid with polio on crutches, or with a withered leg, or worse
   4. images
      • child with crutches and leg brace
      • child with withered legs
      • an iron lung ward for polio victims, Boston, 1950s
   5. polio is due to a virus that attacks the alpha motor neurons (spinal polioencephalitis)
      1. denervation of the muscles and subsequent muscle atrophy
      2. flaccid paralysis, often temporary but with permanent effects in about half of all cases
   6. the virus may also attack various areas of the brain (bulbar polioencephalitis), in which case the disease is much more severe and often fatal

1. definition - apraxia is the inability to execute a learned skilled movement or sequence of movements (due either to an omission of behaviors or intrusion of behaviors); this def. is not universally accepted
   1. limb apraxia - failure of skilled limb movements following a verbal command
      1. left limb apraxia - impairment of left arm only
      2. left limb apraxia with right limb paralysis
      3. bilateral limb apraxia
      4. see big scary diagram no. 4
2. constructional apraxia - patients have trouble drawing 3D pictures or assembling objects from parts; due to damage (most often) in right PACx
   1. attempt to copy a cube by apraxic patient
   2. attempt to copy models
3. often accompanied by contralateral (or unilateral) neglect - failure to attend to one side of the (visual) world, often most clearly indicated when the patient attempts to copy a drawing
   1. attempt to copy a clock face
   2. attempt to copy a house
   3. attempt to copy a house with yard

1. basic wiring of the basal ganglia - see wiring diagram
   1. the entire neocortex is topographically mapped onto the neostriatum
   2. the neostriatum also receives the dopaminergic nigrostriatal tract - two-way communication (typical of a lot of connections in the brain)
   3. the output of the neostriatum goes to the globus pallidus
   4. the globus pallidus projects directly and indirectly into the ventral tier nuclei of the thalamus (as does the cerebellum)
   5. the ventral thalamic nuclei project to the primary motor (and premotor) cortex
   6. there is also a projection to the brainstem nuclei that give rise to the extrapyramidal motor pathways
2. Parkinson's disease
   1. due to death and degeneration of the nigrostriatal tract and loss of DA in the neostriatum - progressive
      • PET scan from a PD patient
      • progression of PD revealed by PET scans
   2. signs
      1. slowness of movement and difficulty starting and stopping voluntary movements ("poverty of movement") - short, shuffling gait with occasional halting or "freezing up"
      2. rigidity - excess muscle tension, difficulty moving joints passively ("cogwheel rigidity" - very characteristic of parkinsonism)
      3. tremor, esp. resting tremor, which is NOT unique to parkinsonism - may originate in a reverberatory circuit between the ventral thalamus and the motor cortex
   3. causes
      1. idiopathic - "nobody knows"
      2. environmental toxins - herbicides, pesticides, free radicals
      3. postencephalitic ("Awakenings" - Oliver Sacks)
      4. drug-induced parkinsonism ("Case of the Frozen Addicts")
      5. genes?
   4. treatments
      1. drugs
         1. Levodopa - l-dopa (converted to DA in the body)
         2. Levodopa/carbidopa (Sinemet) - carbidopa prevents metabolism of l-dopa in the gut, thus sparing it for the brain
         3. various DA agonists - such as amantidine-HCl (Symmetril)
         4. anticholinergics - ACh antagonists, e.g., benztropine
         5. deprenyl (Eldepryl) - MAOI thought to be able to delay the need for l-dopa during the early stages of PD
      2. surgery
         1. deep-brain stimulation - electrical pulses applied through a stereotaxically implanted electrode to the thalamus or globus pallidus to stop dyskinesias (involuntary movements)
         2. pallidotomy - stereotaxic lesion placed in the globus pallidus for relief from rigidity
            • surgery
            • rationale for pallidotomy in PD
         3. thalamotomy - same procedure but done in the thalamus for relief from rigidity or tremor
         4. brain tissue transplants - described in the "Brain Transplant" video
         5. use of neural stem cells
3. Huntington's disease (chorea - "dance" in Greek) - due to degeneration of the neostriatum, esp. the GABAergic and acetylcholinergic neurons), with eventual degeneration in the cortex as well, resulting in a progressive course ending in death within about 10-12 years
   1. choreiform movements - quick, uncontrollable, jerky movements of the voluntary muscles involving several muscle groups or whole limbs, usually developing in the upper body first
   2. inability to sustain muscle contraction (fluctuating grip strength)
   3. dementia - emotional, personality, and memory disorders
   4. genetic in origin, resulting from an abnormal gene on chromosome 4
      1. inheritance pattern - case of Woody Guthrie
      2. inherited as an autosomal dominant
      3. onset of symptoms between 30 and 50 years of age
      4. there is now a test for the gene, but there is still no treatment
      5. DA antagonists alleviate symptoms while DA agonists make them worse
      6. may be excitotoxic, with overactive cortical glutamate cells killing off the GABA and ACh cells in the neostriatum
   5. its victims were often persecuted as witches in 17th cent. England, so many afflicted families fled to the American colonies in 1630 - the first convincing case described in this country was a woman hanged for witchcraft in 1653)
4. hemiballismus - violent, unilateral flailing movements of the limbs that exhaust and incapacitate their victims (and lead to death from exhaustion unless arrested); due to stroke, tumor, or infection in the subthalamic nucleus
   • treatment with deep brain stimulation
5. athetosis - a slow, coarse writhing movement of the head and limbs, including facial grimacing; may be a side effect of l-dopa and other drugs used to treat PD
6. dystonia - a broad collection of various conditions (including athetosis) that involve involuntary muscle contractions of the voluntary muscles, which force the patient's body into unnatural movements and postures, sometimes painful (may occur in any part of the body)

1. don't worry about the anatomical details in the book - worry about these anatomical details instead!
   1. involvement with the vestibular system and vestibulospinal tracts - balance
   2. involvement with the rubrospinal system - coordination of movements involving many joints or limbs (???)
   3. involvement with the corticospinal system - thought to be involved in the timing of rapid, skilled movements (ballistic movements; too fast to be guided by sensory feedback)
   4. big scary wiring diagram (just for the painfully curious)
2. damage to the cerebellum - cerebellar ataxia
   1. some forms are genetic - genetic atropy of the cerebellum
   2. signs (patients tend to have a "drunken" demeanor)
      1. staggering gait, loss of equilibrium - due to loss of muscle synergy
      2. decomposition of movement - movements requiring the motions of several joints are not properly coordinated and appear robot-like
      3. inability to stop movements at the desired point
      4. inability to stop one movement and following it immediately by the opposite one (tested by pronation and supination of the hand) - this is called dysdiadochokinesia, a term you don't have to remember (but one of my favorites!)
      5. scanning speech - stops and pauses in the wrong places; due to loss of synergy in the speech muscles
3. other effects of damage to the cerebellum
   1. intention tremor
   2. asthenia - muscle weakness, fatigability
4. role of the cerebellem in motor learning revealed by degeneration of the inferior olive
   • ability to adjust dart throwing after IO damage

1. multiple sclerosis - demyelenating disease, possibly autoimmune, that attacks the motor pathways, and sometimes sensory and other pathways as well
2. lateral (spinal) sclerosis - degeneration of the lateral tracts of the spinal cord causing spastic paraplegia (upper motor neuron disease)
3. amyotrophic lateral sclerosis (ALS, Charcot's disease, Lou Gehrig's disease) - disease of the lateral motor tracks of the spinal cord causing progressive muscle atrophy, hyperreflexia, fasciculations, and spastic irritability of the muscles (upper motor neuron accompanies by some features of lower motor neuron disease); possibly viral or genetic
4. cerebral palsy - loss of accurate motor control (palsy = paralysis or paresis) often due to perinatal brain damage associated with anoxia (but may also be viral or traumatic)
5. muscular dystrophy - a group of inherited disorders affecting mostly men and resulting in progressive muscle degeneration
6. myasthenia gravis - an autoimmune disorder attacking the motor endplate (ACh receptors on the muscles) resulting in "grave muscle weakness" (ptosis (droopy eyelids) in myasthenia gravis)

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