Session 6: Motor Disorders Flashcards
What are the components of the Motor Pathway?
- Corticospinal tract
- Corticobulbar tract
- Extrapyramidal tracts
Where is the cerebellum located?
- Located in the posterior cranial fossa at the back of the brain
- Separated from the occipital and parietal lobes by the tentorium cerebelli
- Separated from the pons by the 4th ventricle
- It has an important role in motor control and coordination
What are the component of the Cerebellum?
- Vermis in the midline which regulates the trunk musculature
- Lateral hemispheres which regulate the distal structures (limbs)
How does pathology in the cerebellum affect the body?
-Tracts are ipsilateral in the cerebellum so pathology affect the ipsilateral side
How does the cerebellum communicate with brainstem and cortex?
- Superior cerebellar peduncle attaches cerebellum to midbrain
- Middle cerebellar peduncle attaches cerebellum to pons
- Inferior cerebellar peduncle attaches cerebellum to medulla
- Cerebellum communicates with the cortex via the thalamus
What is the effect of a midline lesion of the cerebellum?
- Midline lesions can cause truncal ataxia and abnormal gait
- Extension of midline lesions can also cause 4th cranial nerve lesions, ipsilateral arm tremors compression of 4th ventricle and lead to hydrocephalus
What are the symptoms of cerebellar pathology?
Dysdiadochokinesis – Inability to perform rapid alternating movements
Ataxia – abnormal movement
Nystagmus – rapid eye movements
Intention tremor – tremor when attempting to do something
Slurred speech
Hypotonia – floppy movements
What is the Basal Ganglia?
- Area of the brain know to be involved in motor function
- Communicates with the cortex and cerebellum to aid with the initiation of movement
What are the important Structures of the Basal Ganglia?
- Caudate
- Lentiform nucleus
- Substantia nigra (pars compacta and pars reticularis)
- Subthalamic Nucleus
What are the components of the Lentiform Nucleus?
- Putamen
- Globus pallidus externa
- Globus pallidus interna
What is the output of the basal ganglia?
Thalamus
What are most of the nuerons in the striatum?
-GABAergic
What is the striatum?
Putamen + Caudate Nucelus
What is the substantia nigra made of?
Made up of pigmented neurones:
- Pars compacta dorsally
- Pars Reticularis which is a ventral strip
Which neurons are found in the substantia nigra pars compacta?
-Dopaminergic neurons
How is the circuitry of the basal ganglia arranged?
Direct and Indirect pathways to the thalamus
What is the overall effect of the direct pathway?
- Overall has a stimulatory effect on the cortex without dopamine
- Dopamine merely encourages stimulation of the cortex
What is the overall effect of the indirect pathway?
- Overall has an inhibitory effect on the cortex without dopamine
- Addition of dopamine however stimulates the cortex
What is the overall net effect of direct and indirect pathways on the motor cortex?
-Overall net effect of DOPAMINE in the direct and indirect pathways is motor cortex stimulation via the thalamus
What are the symptoms of basal ganglia disorders?
Affects the contralateral side:
- Abnormal motor control
- Altered posture
- Affects muscle tone
- Dyskinesia
What cause Parkinson’s Disease?
Degeneration of substantia nigra pars compacta leading to deficiency of dopamine
What is Parkinson’s Disease?
- Chronic, progressive movement disorder characterised by triad of symptoms
- Inhibition of motor function due to indirect pathway functioning without dopamine so Bradykinesia
- Lack of encouragement of direct pathway
What are the symptoms of Parkinson’s Disease?
- Bradykinesia
- Tremor at rest
- Hypertonia (rigidity)
What are other associated features of Parkinson’s Disease?
- Hypophonia
- Reduced facial expression
- Micrographia (smaller handwriting)
- Dementia
- Depression
What is Huntington’s Disease?
- Autosomal dominant progressive neurodegenerative disorder
- Onset of disease around 30-50 years
What are symptoms of Huntington’s Disease?
- Chorea (more pronounced at the start)
- Dystonia
- Incoordination
- Cognitive decline
- Behavioural difficulties
What is Huntington’s Disease associated with?
Associated with cell loss within the basal ganglia (striatum) and cortex.
What is Hemiballismus?
- Rare movement disorder associated with dysfunction contralateral sub-thalamic nuclei
- Results in unilateral abnormal movement
- Damage often secondary to sub cortical stroke
Cerebral peduncles contain all motor fibres. True/False
True
