cerebellar ataxia Flashcards
ataxia
Ataxia can mean:
Loss of control of body movements Poorly coordinated movement Unsteadiness
potential causes:
vestibular
cerebellar
sensory
difference, observation subjective hx objective exam background knowledge
vest
cerebellar
sensory
Vestibular
“Spinning”
Slow gait, reduced head movement
Vestibular tests positive Normal limb coordination Normal sensation Positive Romberg
Cerebellum “Unsteady / drunk” Cerebellar signs
Poor limb coordination - heel shin test.
Intention tremor
Wide base, variable
foot placement in gait
Sensory
“Tripping, nervous” Visual dependence Deliberate foot placement in gait Anticipatory balance strategies Positive Romberg Normal limb coordination Reduced sensation
sensory ataxia
Loss of sensory input (proprioception) due to upper or lower motor neuron lesion
Reduced awareness of joint position, spatial relationship
between limb segments, characteristics of support surface
Will be associated with other neurological deficits related to the causative injury
Examples:
UMNL: MS (lesions in parietal lobe), SCI (incomplete: posterior
cord)
LMNL: Peripheral neuropathy (sensory > motor), Charcot- Marie-Tooth
physio mgmt of sensory ataxia
Assessment: Detailed neurological evaluation, including gait (temporal-spatial and video), balance and falls risk
Treatment
Balance rehabilitation targeting proprioceptive inputs (eyes closed, vary support surface, challenge reactive strategies)
Compensation: ankle foot orthosis, gait aids
Sensory input: foot mobilisations, “spiky ball”, surfaces
bare foot exercises
vary the surfaces
cerebellum anatomy
“Little brain” Posterior fossa Highly ridged surface 10% brain volume 50% total neurons half of the neurons of the brain dense structure
3 lobes in the cerebellum
midline - vermis - dense
close to pons and 4th ventricle
all the ridges allow for loads of neurons to fit in
spinocerebellum - spinal execution
neocerebellum - motor planning and motor learning
learn new motor skills
role of cerebellum in movement
Controls error in movement
Interprets and optimises sensory feedback
Imparts new motor skills for motor learning
3 distinct functional regions
Vestibulocerebellum: Eye movements, modifies vestibular influences on posture and balance inputs - vestibular organs legs trunk and eye trunes balance tunes VOR
Spinocerebellum: Regulation of muscle tone, posture, locomotion
inputs somato-sensory and muscle afferents from SC
ouput to SC
tunes and adjusts ongoing movements and muscle tone
Cerebrocerebellum: Preparation for movement, initiation, precise control and timing
inputs primary motor cortex
outputs
primary motor and premotor cortex
function = initiation of skilled movement
causes of cerebellar ataxia
Damage or dysfunction affecting the cerebellum
AND / OR
its input or output pathways
lesions of the cerebellum
Developmental abnormality TBI Stroke / ABI Tumour MS Hereditary disease (Friedreich’s) Degenerative (spino-cerebellar-degeneration) Drug and alcohol intoxications
cerebellar lesion
Ipsilateral lesion → mostly ipsilateral signs
“Double decussation”
Output fibres cross to contralateral VL nucleus of thalamus
Thalamus relays to cortex Corticospinal tract crosses again at medulla
Some bilateral signs
cerebellar signs
Limb movement Dyssynergia Dysmetria Tremor Dysdiadochokinesia Hypotonia Balance and gait dysfunction Oculomotor: gaze stability Nystagmus Impaired smooth pursuit Dysarthria
dyssynergia / dysmetria
Dyssynergia: deficits in multi-joint movements, decomposition of movement
Dysmetria: variability of spatial path, lack of accuracy in hitting
the target
Hypermetria: overshooting Hypometria: undershooting
Tests:
Finger to nose Heel to shin
Abnormal agonist-antagonist relationship
re-bound phenomenon
Flex elbow against examiner
Examiner releases resistance
Unable to stop resultant rebound
Delay is in antagonistic “breaking” response
dysdiadochokinesia
Irregular pattern of rapid alternating movement Pronation / supination Tapping tasks upper and lower limbs With persistence error amplitude of displacement
tremor
Action tremor
During movement: kinetic tremor
Maintaining a posture: postural tremor
Truncal or head: titubation (characteristic 3Hz) (Tremor at rest not seen in pure cerebellar dysfunction)
Intention tremor: increase in tremor amplitude when approaching a target (*may be confused with dysmetria)
Most marked at end of movement (terminal tremor)
hypotonia
Diminished resistance to passive movement
Usually only seen early after lesion / injury
Mechanism unclear
altered tonic background activity of spinal interneurones loss of muscle spindle response
Deep tendon reflexes may produce pendular movement
strength
Ability to produce maximum force unchanged
Ability to sustain it over time is impaired Drift when asked to hold a limb steady Variability in maintaining constant force Impaired agonist / antagonist coordination
Reduced rate of force generation (power)
dysarthria
Scanning speech Hesitation Accentuation of some syllables Incorrect timing of pauses Speech is slurred in 50% Anterior lobe lesions (vulnerable to alcoholic cerebellar degeneration)
nystagmus
Abnormal balance of eye control
Slow drift in one direction/fast corrective movement
Maximal with eye movement in the direction of the fast phase
By convention named by direction of fast phase
Direction of fast phase corresponds to side of cerebellar dysfunction
End point nystagmus vs Gaze evoked nystagmus
eye movements
Smooth pursuit: Tracking movement of the eyes (following a moving object)
Saccades: Fast movements of the eyes
Test by getting patient to look from one object to another
Abnormalities
Hypo/Hyper metric saccades Post-saccadic drift
Jerky smooth pursuit
effects on motor tasks
Errors of
rate amplitude accuracy force
Poor control over postural adjustments
adaptive motor behaviours
Dependency on visual information
Hold themselves stiffly with wide base of support
Shorten range
Keep arms close to body; decrease need for multijoint co- ordination
Use arms to stand up
effect on posture and balance
Increased postural sway
Head and truncal tremor between 2 and 5 Hz Lesions of anterior lobe, vermis and fastigial n. Sway greatest in AP direction
Impaired postural reactions to perturbation Hypermetria
Impaired anticipatory postural adjustments Imbalance during self-generated movements
Tendency to fall to side of lesion
effect on gait
Temporal-spatial parameters: Prolonged double support phase Shorter stride length Wide base (increased step width) or variable base Kinematics: Greater variability Poor inter-limb coordination leads to foot placement errors
cerebellar assessment
Specific Cerebellar Tests
Finger-nose Finger-finger
Rapid alternating movements Finger tapping test
Heel to shin Rebound test Pendular sign
General Tests Functional Reach Rhomberg’s test Sharpened Rhomberg SLS EO/ECTandem walking CTSIB Gait analysis Nine hole peg test
rehab for ataxia?
Cerebellum is crucial to motor learning
Cerebellum is involved in predictive control
Implications of a cerebellar lesion:
Motor learning is slower
Trial and error practice will not work
Patients need guidance on task-specific training
Complex movements need to be broken into component parts
Patient needs to use cognitive strategies
Functional gains can be achieved
treatment strategies
Use external constraints
Encourage practice of smooth movements including stopping
and starting
Include activities that require sustained force
involve the production of rapid initial burst of agonist activity
Augmented feedback: visual / auditory
Avoid use of “trial and error” for motor learning
compensatory approaches
Encourage decomposition of movement into simpler single joint movements
Visual and verbal cues to aid walking speed and stride length
Assistive technology to aid computer use
Aids to help posture, balance and mobility:
4 point gait with 2 crutches gives wide base of support but can be tricky to coordinate
Rollator provides postural stability and is easy to manoeuvre, but less adaptable than crutches
treatment strategies: tremor
Lycra garments (“second skin”) may provide visco-elastic resistance to tremor
Single case studies only
Limited by difficulty in donning and doffing
Weights:
Weighted caps or belts for head or truncal titubation Limb weights to increase inertia of limb
Addition of load requires adaptive scaling of agonist– antagonist activity, impaired in cerebellar disease
Cooling may temporarily reduce tremor
restoration gait and balance
Balance re-training Manipulate vision, proprioceptive and vestibular information Safe place Progress Gait training Parallel bars BWSTT (body weight supported treadmill training
Vary
support surface environmental constraints timing
Falls risk assessment
effectiveness of restoration strategies
Prolonged interventions (3-12 months): reduced force variability, improved inter-limb coordination (Schalow 2006,Kara Harris-Love 2004)
Biofeedback and relaxation therapy effective in reducing tremor
(Guercio 2001)
Improved balance with video-game biofeedback of Centre of
Pressure (Betker 2006)
Improved motor performance and goal attainment with coordinative training (Ilg et al 2009)
gaze stabiltiy exercises
Active eye and head movements between two stationery targets
Visual fixation on a target; slow head movements
Progress to more dynamic tasks, including standing balance challenges or walking with head turns / active eye movements
More on this in Week 7 of Neurology II – Vestibular Rehabilitation
