Week 1 Cerebellar Dysfunction and Ataxia Flashcards
What are the functions of the Cerebellum?
- It controls the ONSET, LEVEL, and RATE of Force production by muscles for movement and Postural Equilibrium
- Acts as COMPENSATOR and performs predictive compensatory modification of reflexes in preparation for movement
- Acts as COMPARATOR between sensory input and motor output
List the features of Cerebellar Dysfunction:
Acronym HADTO
- Hypotonia
- Ataxia - uncoordinated movement
- Dysarthria - slurred speech
- Tremor
- Ocular Motor Dysfunction
(A patient may have one or more of the symptom or a combination)
Damage to the Vestibulocerebellum leads to…
- Balance:
a. Postural instability during stance in gait (postural sway and trunkal ataxia) - trunk cannot be stabilised
b. decreased postural reflex
c. nausea - Coordination and eye movements
a. Vestibulo-ocular reflex - fixation of the eye when rotating the head
b. Cerebellar nystagmus - instability of the eye to fixate they tend to drift away and rapidly return
Lesion in the Spinocerebellum leads to….
- linked to HYPOTONIA
-decrease excitation of the alpha and gamma motor neurons- is more noticeable in the UL’s and proximal mms
- usually accompanies acute lesions
Spinocerebellum loss of Programmed Deceleration leads to:
- Hypermetria - overshoot a movement (eg. when you are reaching an object you move past the point)
- Rebound Phenomenon - forces applied to the limb eg. when that force is suddenly removed normally the person will switch off the opposing force, a person with this has difficulty with that and they will keep pushing
- Lack of Motor Plasticity or Learning
- Involvement of legs resulting in gait ataxia
- Intention Tremour: As arm approaches target it goes into oscillations
What is Resting tremour?
- a tremour which is maximal at rest and tends to decrease with activity
What is Postural Tremor?
- maximal when limb is in a fixed position or when you are holding yourself against gravity
What is Intention Tremor?
- Maximal when doing the movement particularly when moving towards a specific object or target
Damage to the Neocerebellum leads to….
- MOVEMENT DECOMPOSITION - difficulty performing the a movement in one smooth pattern, pt performs the movement in a sequence of steps
- Asthenia - generalised weakness (a sense of heaviness or extra effort)
- Dysmetria - arc of movement is wavey or jerky
- Dysdiadochokinesia - rapidly alternating movements are uncoordinated (eg. pronation and supination of hand or foot tapping)
- Delayed initiation of movement
- Dysarthria: scanning, slurred, staccato, hesitant, garbled
Neocerebellum damage leads to… (continuation)
- dyssynergy - defective timing of sequential contraction of agonist/antagonist mms
- there is a loss of anticipatory movements in response to perturbations
- Inability to adjust to environmental or specific task demands
- Problems with visual pursuit movements (occular dysmetria)
What is a cardinal feature of cerebellar dysfunction (occurs when any area of the cerebellum is affected)?
ATAXIA
What is Ataxia?
- Appears in the trunk, extremities, head, mouth and tongue (speech)
- Incorrect programming of RATE, RANGE, DURATION, and Force of muscle contraction
- Inability to regulate posture will also decrease efficiency and smoothness of gait
- Disruption in rhythm so that swing and stance phase are irregular in duration
Lesion of the Spinocerebellum leads to…. (in relation to ataxia)
- movements are random in all directions
Lesion of the Cerebrocerebellum (Neocerebellum) leads to…. (in relation to ataxia)
- staggering/falling are towards the side of the lesion
What is Sensory Ataxia?
- Damage to sensory pathways
- Loss of proprioception and vibration sense
- Worse when eyes are closed
- Broad base steppage gait, slapping foot contact
- Dysarthria and nystagmus are rare
What is Vestibular Ataxia?
- Damage to CN VIII (Vestibulocochlear nerve) or its connections
- Vertigo, nausea, loss of balance, nystagmus
What is Cerebellar Ataxia
- damaged cerebellum or its cerebral brainstem and SC connections
- Intact sensory receptors and afferent pathways
- Integration of proprioception is faulty
- worse with speed
- Gait: wide-based with irregular and unsteady steps
What is Frontal Ataxia?
- AKA Gait ataxia
- typically observed with tumours or abscesses or stroke in the frontal lobe
- may be caused by Frontal Dementia
- Gait: Scissor Gait - increase adduction
What causes Symmetrical Ataxia?
- Intoxications: alcohol, sedatives, anticonvulsants
- Infections
- Lyme disease
- Hypothyroidism
- Genetic disorders
- High altitude cerebral oedema
- Hydrocephalus
What causes Asymmetrical Ataxia?
- Stroke/TBI
- Infections
- Demyelination
- Tumours
- Trauma
- AIDS
- Cervical spondylosis
What is Fredereich’s Ataxia?
- Most common hereditory progressive ataxia
- Belongs to a group of Hereditory ataxias
- Described by Nickolaus Fredreich
- Affects 1/50,000
- AUTOSOMAL RECESSIVE
- 1/100 people are carriers
Aetiology and DIagnosis of Fredereich’s Ataxia
- mutation in the Frataxin Gene (regulates iron) leads to oxidative stress and mitochondrial damage
- Diagnosed through EMG, CSF, nerve conduction velocity, MRI, DNA testing
- Usually diagnosed in youth (<25 years)
- The Earlier the onset the more severe course
What is Spinocerebellar Ataxia?
- represents a varied group of disorders
- AUTOSOMAL DOMINANT INHERITANCE (only one of the parents need to be a carrier, anybody who has the gene will present symptoms)
- incidence of 1-5/100,000
Symptoms of Fredereich’s Ataxia
- Ataxia is generally the first symptom
- Progressive weakness and fatigue
- Increasing difficulty with mobility and balance
- Dysarthria and Dysphagia
- Decreased sensation: vibration>proprioception>light>touch>pain>temp
- Progression to ataxia and weakness of UL’s (commences in the LL)
- Spasticity
- Hyporeflexia, positive babinski
- Pes cavus (shortening of the foot with high arches), Spinal Scoliosis
- Diabetes
- Cardiac anomalies: hypertrophic cardiomyopathy
NO cognitive effects
Aetiology and Diagnosis of Spinocerebellar Ataxia
- Diagnosis:
a. MRI to detect atrophy of cerebellum
b. genetic testing: DNA testing provides definitive diagnosis in 50% cases
Aetiology:
a. Degeneration of the cerebellum and SC
b. Progressive Atrophy and spasticity
Symptoms of Cerebellar Ataxia
- Age of onset varies with type >18
- Ataxia, dementia, slow eye mvts, visual loss
- Anticipation - an increase in the severity of symptoms in subsequent generation (children having worse symptoms)
