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BG Fxn/Dysfxn
Clinical Notes for Basal Ganglia
Question | Answer |
---|---|
Where is activity of the BG initiated? | Cortical Levels |
Nigral input to striatum provides what, & why? | Continuous damping effect, so that cortical commands will be focused |
Striatum integres & feeds info where? This influences activity of what? | Globus Pallidus & SN-Pars Reticulata; Influences thalamus & other targets (superior colliculus, RF) |
Thalamus projects where? | Appropriate cerebral cortex loci |
BG responsible for? | Automatic execution of a learned motor plan |
Damage to BG results in? | Slower, less automatic & less accurate cortical mechanisms for motor behavior |
During preparation & execution of mvmt, separate neurons within motor loop discharge selectively in relation to what? | Target location in space; Direction of limb mvmt; Mm pattern |
In oculomotor loop, neurons discharge in relation to? | Visual fixation; Saccadic eye mvmt; Passive visual stimuli |
Getting Hypothesis | In normals, dopamine (inhibitory) & cortical sensorimotor (excitatory) inputs to striatum are in balance |
What do cerebellum & BG have in common? | BG= context encoders, info useful in planning & gating of action sent to cerebral cortex; Cerebellum = pattern generator/executor; Both work seamlessly with cerebrum to provide "perfect" automatic mvmt |
Cerebral cortex does what? | Acts as a repository to receive diverse info via ascending tracts, compute it & share it with BG & cerebellum |
More cerebral cortex function | Acts in executive fxn to implement action emanating from its collective computation processes for output via the SC |
Are lesions of the BG & cerebellum UMN? | NO |
Pre-frontal Loop deals with? | Spatial memory; Different from memory mediated by hippocampus & diencephalon; Appropriate switches in behavior |
Limbic System | Emotional & Motivational processes |
Diseases of BG characterized by? | Abnormal involuntary mvmts at rest; Disappear in sleep (non-intention tremor) |
BG dysfunction can be either ___ or ___? | Hypo- or Hyperkinetic |
Most common mvmt disorder of the BG? | Dystonia |
Most common behavioral disturbance of BG? | Abulia |
What is abulia? | Apathy, loss of initiative, & of spontaneous thought & emotional response |
Hyperkinetic Disorders | Chorea (Huntington's, Sydenham's); Athetosis; Ballism; Dystonia; Akathasia; Tourette's |
Chorea | Sudden, Frequent, involuntary, purposeless & quick jerks of trunk, extremities & head associated with facial grimaces |
Huntington's Disease | Hereditary; Choreiform mvmts beginning @ extremities/face that progress to more mm; Mental deficiency (progressive deterioration); Combination of hyperhypokinetic (pt becomes immobile & unable to speak/swallow) |
Sydenham's Disease | Childhood; Rapid, irregular, involuntary mvmts of limbs, face, trunk; Associated with rheumatic fever (pretty rare now); Transient results with full recovery |
Athetosis | slow, writhing, sinuous, continuous, wormlike mvmts of distal parts of extremities which show bizarre posturing; can have choreoathetosis |
Ballism (Hemiballism) | Vascular lesion, sub-thalamic nucleus (indirect motor loop); Mvmts of limbs, sudden, quick, continuous, unusually violent & flinging (contralateral to lesion usually); Proximal extremity mm usu involved (exaggerated chorea) |
Dystonia | twisting, slow, contorting, involuntary mvmt that is somewhat sustained & often repetitive; fixed abnormal posture develops in affected part; Focal, segmental, generalized; sometimes discrete lesion can be found |
Akathasia | Inability to be still, constant motion of limbs; Common SE of many neuroleptic drugs |
Tourette's | Motor tics (sudden, brief involuntary mvmt preceded by urge to perform, followed by sense of relief; eye blinking/shoulder shrugging); vocal tics; ADD/compulsive behaviors; condition of late childhood, can be outgrown; counseling is important! |
Hypokinetic Disorders | Parkinson's |
What are the 3 classic s/sx of Parkinson's? | Tremor, Rigidity, Bradykinesia |
Parkinsonian Tremor | non-intentional |
Parkinsonian Rigidity- Plastic | if pt doesn't also have tremor, mvmt to passive resistance is continuous throughout PROM |
Parkinsonian Rigidity- Cogwheel | if pt also has tremor, mm resistance can be overcome by a series of jerks (like a ratchet) |
Parkinsonian Bradykinesia | Diminution/loss of assoc mvmts, difficult to initiate mvmt, slow mvmt; Masked face; Slurred & monotonous speech |
Postural disturbances in Parkinsonism | Festinating gait; Kyphotic posture |
Is there loss of power of sensation with Parkinson's? | No, should test normal but be aware that patient may be de-conditioned due to sedentary lifestyle |
What is the most consistent pathology in Parkinson's? | Loss of dopamine; Leads to poverty of mvmt & difficulty in switching to new behaviors |
What may be used to treat Parkinson's? | Drugs, sometimes surgery |
Can Parkinson's be cured? | No, only treated. It is ceaselessly progressive, eventually bilateral (even when medicated) |
Is Parkinson's strictly hypokinetic? | No, inclues both types of motor disturbances (hyper [tremor, too much motion] or hypo [bradykinesia]) |