Ataxia Flashcards
Define ataxia
Group of disorders that affect coordination, balance and speech.
4 things impacted:
1) balance and walking
2) speaking and swallowing
3) tasks that require high degree of control
4) vision
What are the 3 different causes of ataxia
1) acquired: trauma, stroke, brain tumour.
2) Hereditary: faulty genes.
3) Idiopathic: no clear reason.
What part of the brain is usually impacted in ataxia
Cerebellum (needed for coordination, balance and tone).
Or parts of nervous system that feed into cerebellum damaged.
Outline the structure of the cerebellum
Posterior and anterior lobes that are separated by a primary fissure.
*splits into vermis and lateral
If look from back: middle is vermis surrounded by intermediate hemispheres.
Ventral view: flocculus and nodulus
Outline vestibulocerebellum
Flocculus and nodulus
Vestibular labyrinth
Flocculonodular
Vestibulospinal
Muscles and balance: so you know where your head is. ‘Inner ear’
vid on bb
Outline spinocerebellum
Neck/trunk
Vermis (middle)
Fastigial nucleus
(then splits in 2)
1)Thalamus-M1(ascending)
2)Reticulospinal tract-axial muscles-tonus (descending)
Spinocerebellum
Interposed nuclei (other nuclei other than fastigial)
splits
1) thalamus-M1
2) red nucleus-tonus (muscle tone)
PROPRIOCEPTION, MUSCLE TONE, COORDINATION
Outline cerebrocerebellum
Lateral hemispheres that surround vermis
Cerebrocerebellum (input from cortex)
Dentate nucleus
splits
1) thalamus-M1(ascending)
2) red nucleus - to spinal (descending)
PLANNING AND INITIATION
Describe 3 layers of the cerebellum from deepest to most superficial
1) Granular layer: contains granule cells that receive input from mossy fibres.
2) Purkinje cell (body) layer: fan-like dendrites of cells extend up to molecular layer where they receive input from second major type of afferent fiber in cerebellum - climbing fibres.
3) Molecular layer: processing layer, contains cell bodies and dendrites of two types of inhibitory interneurons (stellate and basket cells).
What are the 2 afferent fiber systems and how do they encode information.
1) mossy: originate from cell bodies in spinal cord and brainstem. Carry sensory info from periphery as well as info from cerebral cortex.
2) Climbing fibers: originate in inferior olivary nucleus and convey sensory information to the cerebellum from both the periphery and cerebral cortex.
Both carry sensory info from periphery and cerebral cortex
How does learning occur in cerebellum
Implemented through complementary synaptic changes in the cerebellar cortex and deep nuclei.
2 stimuli presented at same time so association:
1) bought in mossy
2) bought in inferior olive
Both go to deep nucleus
Thought to occur in deep cerebellar neurons and at synapses from purkinje cells.
Evidence that the cerebellum plays role in adaptation of limb movements that rely on hand-eye coordination
Prisms that deflect light path sideways: patients with damaged cerebellar cortex or inferior olive are severly impaired or unable to adapt at all in this test.
Treatment of ataxia
In most cases, there’s no cure for ataxia and supportive treatment to control thesymptoms is necessary.
Thismay include:
speech and language therapy to help with speech and swallowing problems
physiotherapyto help with movement problems
occupational therapyto helpcoping with the day-to-day problems
medication to control muscle, bladder, heartand eye problems
In a few cases, it’s possible to improve ataxia or stop it getting worse by treating the underlying cause.
Outlook of ataxia
Depends on the type of ataxia. Some types may remain relatively stable or even improve with time, but most will get progressively worse over many years.
Life expectancy is generally shorter than normal for people with hereditary ataxia, although some people can live well into their 50s, 60s or beyond.
For acquired ataxia, the outlook depends on the underlying cause. Some cases may improveor stay the same, whileother casesmayget gradually worse over time and reduce life expectancy.
Outline Friedreich’s ataxia
Prevalence: 1 in 50,000
Cause: hereditary
Symptoms: start in childhood. balance and coordination, weakness in legs, speech, swallowing, vision loss, hearing loss.
Impaired mitochondrial function: impacts organs such as heart and pancreas as well as nervous system
* FXN gene encodes Frataxin expressed in above tissues: puts together cofactors (iron sulfur clusters). Needed for electron transfer, this causes mito dys (less ATP produced and Fe and O2 combine to make free radicals and cause cell death)
Mutation: GAA trinucleotide repeat over x100 normal = gene silencing (diagnosis is genetic test)
Autosomal recessive (carrier parents)
Common cause of death: abnormal thickening of ventricles - hypertrophic cardiomyopathy.
Outline Ataxia-telangiectasia
Prevalence: 1 in 40,000-100,000
Cause: Hereditary
Symptoms: begin in early childhood, difficulty walking, speech, red blood vessels in corner of their eyes, weakened immune system.
Mutation of ATM (protein kinase tha activates tumour suppressor genes etc) that usually fixes DNA damage (double stranded breaks) and develops T-lymphocytes.
* decrease in ATM function = damaged cells proliferate and die, causes cerebellar atrophy.
* T cells are non functional and decreased immunoglobin levels that leads to decreased immune function.
* cancer is more common.
Diagnosis: genetic, low immunoglobins and high alpha-fetoprotein
