basal ganglia pathology

dystonia

sustained contractions of agonist and antagonist

• involuntary movement

• abnormal, distorted positions of the limbs, face, or trunk that are more sustained or slower than athetosis

• can be generalized, unilateral, or focal (torticollis, blepharospasm, spasmodic dysphonia, writer’s cramp)

• treated with botilunum toxin

athetosis

writhing, “worm-like”

• involuntary movement

• twisting movements of face, trunk, limbs

• sometimes merge with faster choreic movements → choreoathetosis

chorea

• rapid, irregular, fluid or jerky involuntary movement

• movements are often incorporated into voluntary movements in an attemp to conceal their occurrence

• when it’s severe, it resembles “break-dance”

ballismus

large amplitude sudden, violent flailing

• involuntary movement

• movements of proximal limb muscles with a larger amplitude, more rotatory o flinging quality than chorea

myoclonus

cyclical, spasmodic alternation in muscle contraction and relaxation (quick muscle jerks)

• involuntary movement

• sudden rapid muscle jerk

• can be focal, uni or bilateral

• multiple causes

resting tremor

• rhythmic or semi-rhythmic oscillation movement

• often seen with basal ganglia lesions (not always)

• obvious when limbs are at rest, decreases/stops when patient moves their limbs

notable feature of PD

pill-rolling tremor

hypkinetic movement disorder

parkinson’s

hyperkinetic movement disorders

• huntington’s disease

• hemiballismus

unilateral movement disorders caused by focal basal ganglia lesions causes the movement of disorder to be…

CL to the lesion

bradykinesia (slowed movement) is caused by…

• increased inhibitory basal ganglia outflow to the thalamus

  • basal ganglia sends too much inhibitory signals to thalamus = less movement

• loss of dopamine from substantia nigra pars compacta

  • dopamine helps direct and reduces indirect pathways

• direct pathway becomes weaker

  • usually direct pathway reduces thalamus inhibition = movement

  • less dopamine causes striatum to inhibit GPi less = GPi sends more inhibitory signals to thalamus = less movement

• indirect pathway becomes stronger

  • Fewer inhibitory signals go from GPe to the subthalamic nucleus.

  • STN becomes more active → excites GPi → GPi inhibits the thalamus even more.

  • This further reduces movement

rigidity

• increased resistance to passive movement

• present in disorder that cause bradykinesia or dystonia

clasp-knife rigidity

• corticospinal disorders

  • resistive tone increases as muscles of limbs are stretched, then may decrease

lead pipe rigidity

• basal ganglia disorders

  • continuous resistence to stretch

cogwheel rigidity

• basal ganglia disorders

  • ratchet-like interruptions

  • often thought of rigidity with a superimposed tremor

dystonia causes

• primary idiopathic dystonia (hereditary)

• any disorder affecting basal ganglia

• long-term use of dopamine-blocking medications

• Wilson’s disease

  • genetic disease where body can’t get rid of copper causing it to build in liver and basal ganglia

  • Kayser-Fleischer copper rings

tardive dyskinesia

• A medication-induced movement disorder.

• Causes involuntary mouth and tongue movements

athetosis causes

• perinatal hypoxia involving basal ganglia

• wilson’s disease

• huntington’s disease

• PD = patients being treated with levodopa can experience disabling hyperkinetic dyskinesias

chorea causes

• huntington’s disease

• benign familial chorea (inherited)

• sydenham’s or rheumatic chorea (rare)

• Lupus

• patients being treated with levodopa can experience this

hemiballismus

unilateral wild flingling movements of the extremities CL to a lesion in the basal ganglia

ballismus or hemiballismus typically involves…

a lacunar lesion (small stroke) in subthalamic nucleus or the striatum

• damage to subthalamic nucleus…

  • decreases excitation to GPi

  • GPi gives less inhibition to thalamus (becomes disinhibited)

  • thalamus then is overactive = hyperactive movement

motor tics involve

face or neck

vocal tics can be…

brief grunts, coughing sounds, howling or barkings sounds, vocalizations of obscene words

• tourette’s

tremor

• both agonist + antagonist muscles are activated, resulting in bidirectional movements

• can be slow or fast

classic SxS of PD

• bradykinesia, rigidity, rest tremor/pill-rolling tremor, postural instability/unsteady gait

ideopathic parkinson’s disease is characterized by…

• resting tremor

• bradykinesia

• postural = gait disturbance (freezing gait, festinating gait, retropulsion on backward pull test)

• rigidity = masked face, hypophonia

huntington’s disease

autosomal dominant neurodegenerative condition

• characterized by

  • progressive, usually choreiform movement disorder

  • dementia

  • psychiatric disturbances

• progressive atrophy of striatum (caudate nucleus + putamen)

• results in abnormalities of all 4 channels (motor, oculomotor, prefrontal, limbic)

what is severely affected in huntington’s disease?

the indirect pathway

• less/no enkephalins are released by striatum resulting in disinhibition of the thalamus

• if thalamus is not inhibited, it will continue to send excitatory signals to the cortex producing excessive movement