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88 Cards in this Set
- Front
- Back
The cerebellum serves to:
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1-integrate sensory and other inputs from many regions of the spinal cord and brain.
2-smooth movements/ coordination; functions in motor planning. 3-involvement of lower motor neurons (not directly) through motor system of cortex & brainstem. |
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What condition is typically related to lesions of the cerebellum?
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Ataxia - irregular, uncoordinated movements
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What function does the inferior vermis or flocculonodular lobes serve?
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Regulates balance and eye movement in conjunction with the vestibulatory circuitry. Also works with other parts of vermist to regulate medial motor systems (e.g., proximal trunk & limb muscles).
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What do the intermediate hemispheres do?
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These regions serve the lateral motor systems, such as distal appendicular muscles.
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Which region of the cerebellum functions in motor planning?
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The lateral cerebellar regions.
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Is ataxia ipsilateral or contralateral to the side of the cerebellar lesion?
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Ipsilateral
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Unsteady gait, such as truncal ataxia and eye movement abnormalities result from what type of lesions?
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Midline lesions of the cerebellar vermis or flocculonodular lobes
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Midline lesions can cause what type of symptoms (other than the unsteady gait)?
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Intense vertigo, nausea, and vomiting
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Ataxia of the limbs, for example, appendicular ataxia, result from lesions where?
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Lesions lateral to the cerebellar vermis.
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Identify four additional functions of the cerebellar pathways:
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1 - speech articulation
2 - respiratory movements 3 - motor learning 4 - higher order cognitive functions |
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How is the cerebellum attached to the dorsal region of the pons and medulla?
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It is attached by the superior, middle, and inferior cerebellar peduncles.
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The roof of what ventricle is formed by the cerebellum?
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Fourth ventricle
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Herniation of the cerebellar tonsils can be caused by and lead to what conditions?
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Caused by mass lesion of the cerebrum or cerebellum, brain swelling, intracranial pressure. Herniation can lead to tonsils being pushed into foramen magnum, compress the medulla, & possible death secondary to medulla respiratory centers being affected.
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Which cerebellar peduncle carries mainly output from the cerebellum?
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Superior cerebellar peduncle.
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Which peduncle (s) carry mainly input to the cerebellum?
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Middle and Inferior cerebellar peduncles.
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What are the main functions of the lateral hemispheres?
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Motor planning for extremities.
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Which region is the largest part of the cerebellum?
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The lateral hemispheres.
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Which motor pathways influence the lateral hemispheres?
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Lateral corticospinal tract
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What is the function of the intermediate hemispheres of the cerebellum?
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Distal limb coordination, particularly the appendicular muscles in the legs & arms.
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Which region of the cerebellum controls proximal limb and truck coordination?
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Vermis.
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The flocculonodular lobe controls what functions?
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Balance and vestibulo-ocular reflexes.
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What motor pathways are influenced in the intermediate hemispheres?
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lateral corticospinal trach & rubrospinal tract.
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What motor pathways are involved in the vermis?
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Anterior corticospinal tract, reticulospinal tract, vestibulospinal tract, & tectospinal tract.
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The motor pathway of the medial longitudinal fasciliculus is involved in which region?
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Flocculonodular lobe.
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If there is a lesion in the lateral cerebellum, what function may be affected?
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Distal limb coordination.
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Truck control, posture, balance, & gait can be affected by a lesion in what region?
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Medial cerebellum.
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Deficits in coordination are ipsilateral the the lesion because the pathways are "double crossed." Where are the crossings?
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1 - As the cerebellar output pathways exit in the decussation of the superior cerebellar peduncles.
2 - Occurs as the cortico -spinal and rubrospinal tract go down to the spinal cord. |
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Do lesions of the medial motor system cause unilateral, contralateral, or bilateral deficits?
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Bilateral, as the medial motor system influences the proximal trunk muscles bilaterally.
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Inputs to the cerebellum arise from various sources. Identify 4 regions:
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All regions of the CNS, sensory modalities, brainstem nuclei, & spinal cord.
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What is the major source of fibers in the cerebellum?
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Corticopontine fibers from the 4 lobes of cerebrum - travel in the internal capsule and cerebral peduncles.
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How is much of the cerebellum innervated?
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Pontocerebellar fibers cross the midline to enter the contralateral middle cerebellar peduncle. It branches to mossy fibers to innervate the cerebellum.
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Spinocerebellar fibers are another greast source into the cerebellum. What information is conveyed via this route?
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Information about limb movements via the dorsal spinocerebellar tract and cuneocerebellar tract.
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Why would you get ipsilateral limb ataxia if there was a lesion within the spinocerebellar tract?
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The input is either ipsilateral or double-crossed.
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What are the 2 types of synaptic input into the cerebellum?
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Mossy fibers (excitatory synapses) and Climbing fibers (also powerful excitatory synapses).
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Which cells carry all of the outputs of the cerebellum?
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Carried out by the axons of purkinje cells, which form inhibitory synapses onto deep cerebellar nuclei and vestibular nuclei - then outputs from the cerebellum to other regions (excitatory).
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Cerebellar inhibitory interneurons include:
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Basket cells and stellate cells (located in the molecular layer).
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Axons projecting upward are excitatory. These include:
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mossy fibers, climbing fibers, granule cell parallel fibers.
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All axons projecting downward are inhibitory. These include:
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Purkinje cells, stellate cells, basekt cells, and Golgi cells.
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What branches of arteries supply the cerebellum?
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Posterior inferior cerebellar artery, anterior inferior cerebellar artery, & superior cerebellar artery.
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Do the arteries above supply blood to the cerebellum exclusively?
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No, they also supply blood to portions of the lateral medulla & pons.
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Infarcts are most common in which arteries?
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Posterior inferior cerebellar artery and Superior cerebellar artery.
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What are the common symptoms seen in cerebellar infarcts?
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headache (occipital, frontal, upper cervial), nausea/vomiting, horizontal nystagmus, vertigo, unsteady gait, & limb ataxia.
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If the cerebellum is spared (in an infarct), can the patient have ataxia?
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Yes, because many signs/symptoms of cerebellar artery infarcts result from lateral medulla/pons infarcts - it is because of its involvement with the cerebellar peduncles.
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What kind of infarct may have occured if the brainstem was spared but involved primarily the cerebellum?
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Superior cerebellar artery infarct.
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Which infarcts would involve both lateral brainstem and cerebellum?
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Posterior inferior and Anterior inferior cerebellar arteries.
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Compression of the fourth ventricle can be caused by what type of infarct?
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Large cerebellar infarcts involving areas supplied by the posterior inferior and superior cerebellar arteries. This can lead to hydrocephalus
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Why would compression of the posterior fossa be life threatening?
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Respiratory centers & other equally vital brainstem structures can be affected.
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What primary medical conditions can lead to cerebellar hemorrhage?
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Chronic hypertension, ateriovenous malformation, hemmorhage 2ndary to inschemic infarct, & metastases.
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What can be caused by a large cerebellar hemorrhage?
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hydrocephalus, 6th nerve palsy, impaired consciousness, brainstem compression, death.
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What is ataxia?
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Problems with both contractions of agonist and antagonist muscles. It's the lack of normal coordination btwn movement at different joints.
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What are characteristics of ataxia?
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irregular movements, with a wavering course that can present with "overshoots," overcorrecting and then overshooting again around the intended target.
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What are the characteristics of ataxic movements?
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Problems with timing (dysrhythmia) and problems with trajectories through space (dysmetria).
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What type of ataxia is caused by lesions of the cerebellar vermis?
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Truncal ataxia - wide-based, unsteady, drunk-like gait. One can have some difficulty sitting upright in severe cases.
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What portions of the cerebellum are affected in appendicular ataxia?
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Lesions of the intermediate and lateral portions.
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Which motor system leads to a bilateral (truncal ataxia)?
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Lesions affecting the medial motor system - while bilateral, patient may lean towards side of lesion.
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With intact cerebellum, lesions in the cerebellary peduncles or pons can lead to what?
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Severe ataxia.
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Gait abnormalities, similar to truncal ataxia, can result from lesions/hydrocephalus in which brain region, other than cerebellar hemispheres?
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Lesions within the prefrontal cortex or hydrocephalus, which may damage frontopontine pathways.
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Another false localization of ataxia can occur where in the CNS?
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Spinal cord.
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What syndrome is caused by lacunar infarcts in the cerebellum?
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Ataxia-hemiparesis.
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What is the clinical presentation of ataxia-hemiparesis?
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Includes a combination of ataxia and unilateral motor signs. Both ataxia & hemiparesis are contralateral to side of lesion.
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What areas are typically lesioned in the syndrome of ataxia & hemiparesis?
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Internal capsule or pons that involve both corticospinal & corticopontine fibers, and corona radiata. Also, frontal, parietal lobes, sensorimotor ctx, midbrain lesions (fibers involving superior cerebellar peduncles or red nucleus).
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What pathway is disturbed in sensory ataxia?
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Posterior column-medial lemniscal pathway
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What symptoms occur in sensory ataxia?
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It causes impaired or loss of joint position sense and is characterized by ataxic like overshooting movements of the limbs and wide-based, unsteady gait.
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What worsens symptoms of sensory ataxia? What improves symptoms?
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When eyes are closed or in the dark, symptoms worsen; visual feedback helps.
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What types of lesions will cause sensory ataxia in the ipsilateral side of the lesion?
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Typically involves lesions of the peripheral nerves or posterior columns.
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In contralateral ataxia, where are the lesions typically located?
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May occur secondary to lesions in the thalamus, thalamic radiations or somatosensory cortex.
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What are common symptoms/signs of lesions in the cerebellum that produce incipient tonsilar herniation?
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Depressed consciousness, brainstem findings, hydrocephalus, head tilt.
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What are some abnormalities that can confond the cerebellar exam?
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Upper motor neuron signs (corticospinal and cerebellar lesions), lower motor neuron signs (testing would not be possible), sensory loss, basal ganglia dysfunction,tremor, & dyskinesia.
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What is dysmetria?
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Abnormal under- or overshooting during movements toward a target.
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What is dysrhythmia?
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Abnormal rhythm and timing of movements.
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Name and describe one test for ataxia:
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Finger-to-nose test - alternately touches nose and examiner's finger.
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Name and describe a second test for ataxia:
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Heel shin - rubs heel up and down length of shin in a straigt line (lying down).
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What is dysdiadochokinesia?
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Abnormalities of rapid alternating movements.
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What type of ataxia is seen in a wide-based gait, like a drunk person or toddler, with cerebellar involvement?
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Truncal ataxia.
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Name and describe one type of test for truncal ataxia:
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Tandem gait testing - heel-toe walk (narrow stance). The patient will fall or deviate towards the side of the lesion.
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Name and describe another test for truncal ataxia:
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Romberg's Test - Feet together (1/2 minute), eyes closed then. + test: can stand w/ eyes open, but falls with eyes closed. Proprioception lesion, not test of cerebellar fxn.
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Where would the lesion be if the patient had a hard time standing with eyes open AND closed?
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Midline cerebellar lesions (also a peculiar tremor of the trunk or head-titubation-can occur).
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Define ocular dysmetria:
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saccades overshoot or undershoot their target.
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Define nystagmus, of the gaze paretic type:
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The patient looking at a target in the periphery shows slow phases toward the primary position and fast phases occur back towards the target.
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What is it called when a person's speech has an ataxic quality, in cerebellar disorders, with irregular fluctuations in rate & volume?
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Scanning or explosive speech.
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What are the most prevalent causes of acute ataxia in adults?
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Ingestion of toxins and ischemic or hemorrhagic stroke.
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Identify the common causes of chronic ataxia in adults:
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brain metastases, chronic exposure to toxins(e.g., alcohol), multiple sclerosis, degenerative disorders of the cerebellum or cerebellar pathways.
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In the pediatric population, what are the most common causes of acute ataxia?
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Accidental ingestion of drugs/toxins, varicella- associated cerebellitis, migraine.
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Also in children, what are common causes for chronic or progressive ataxia?
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Cerebellar astrocytoma, medulloblastoma, Friedreich's ataxia, ataxia-telangiactasia
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In understanding the neuroanatomy of the cerebellum, where is it located in the cranium?
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Posterior fossa
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The cerebellum consists of what brain structures?
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Midline vermis, intermediate part of the cerebellar hemisphere, lateral part of the cerebellar hemisphere.
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The cerebellum is attached to the brainstem via which structures?
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Superior cerebellar, middle cerebellar, and inferior cerebellar peduncles.
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What are the 3 functional zones of the cerebellar cortex and deep nuclei?
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1 - Vermis (via fastigial n.) & flocculonodular lobes (via vestibular n.)
2 - Intermediate part of cerebellar hemispher (via interposed n.) 3 - Lateral part of the cerebellum (via dentate n.) |