Cerebellum & Movement disorders Flashcards
What are the inputs and outputs to the cerebellum?
Afferent inputs: vestibular, proprioceptive, skin receptor, sensorimotor cortex
Efferent outputs: Motor systems: vestibular nuclei, thalamus, red nucleus
Describe the general pathway through the cerebellum
Afferents are mossy and climbing fibers that enter the cerebellar cortex and then synapse with Purkinje cells. Purkinje cells synapse on deep nuclei before projecting to their targets
Which is the largest cerebellar peduncle?
The middle cerebellar peduncle
Which cerebellar peduncles carry afferent information and which carry efferent?
Superior: efferent
Middle and inferior: afferent
Describe the afferent pathways to the cerebellum
Fibers from the cerebral cortex synapse in the pontine nuclei and enter the contralateral cerebellar cortex through the middle cerebellar peduncle
Fibers from the contralateral inferior olive, and ipsilateral vestibulocochlear nuclei, and spinocerebellar tracts enter through the inferior cerebellar peduncle
Describe the somatotopic organization of the cerebellum
The vermis (central portion) controls trunk stability and gait. The hemispheres are responsible for ipsilateral limbs and motor coordination.
What is unique about the anterior spinocerebellar tract?
It is the only afferent tract in the superior cerebellar peduncle
Describe the connections to/from the flocculonodular lobe
Vestibular afferents and efferents to the fastigial nucleus
The fastigial nucleus projects to the vestibular nuclei, which project bilaterally through the MLF to the abducens nucleus, PPRF and oculomotor nucleus
Describe the connections to/from the vermis
The vermis projects to the fastigial nucleus and the vestibular nucleus which has projections forming the descending MLF and lateral vestibulospinal tract. The globose-emboliform nucleus also projects to the contralateral red nucleus which then projects downward as the ipsilateral rubrospinal tract (crosses 2 times).
Describe the connections to/from the cerebellar hemispheres
Input from the olive (ICP) and pons (MCP) reach the dentate nucleus, which projects to the contralateral red nucleus and ventrolateral thalamus. The red nucleus projects down the the inferior olive. The VL projects to the cerebellar cortex, which then communicates with the pontine gray as well as the corticospinal tract
What are the 3 microscopic layers of the cerebellum?
Molecular: axons and dendrites
Purkinje: the only axons that leave the cerebellum
Granular: Axons from the parallel fibers
Which cells of the cerebellum are excitatory and which are inhibitory?
Moss fibers, parallel fibers (granule cells), and climbing fibers are excitatory. Purkinje cells are inhibitory.
What effect do purkinje cells have on movement?
When purkinje cells are active, they inhibit movement
What is praxis?
A memory or concept put into action on command
Ex: patient with gait apraxia is immobile when asked to walk, despite having all the essentials necessary for walking
What essentials are necessary for normal walking?
Strength, coordination, postural control, sensation
What differentiates a posterior column lesion from a cerebellar lesion?
Posterior column lesions present as positive Romberg signs. Cerebellar disease causes instability regardless of eyes open/closed.
Broad based ataxic gait is associated with lesions where?
Posterior columns, sensory nerves, or cerebellum
What is a hemiplegic gait?
Affected lower limb is stiffly extended and swung/circumducted to walk. Affected ipsilateral upper limb is flexed at the elbow and wrist with decreased armswing
Common in stroke patients
What is a tabetic gait?
Foot slapping due to impaired sensation
Seen in tabes dorsalis neurosyphilis
What is a steppage gait?
Foot drop due to peroneal nerve of L5 root lesions
Hip flexed higher to elevate the dropping foot to avoid tripping
What is a waddling gait?
Weak pelvic/hip muscles cannot support the body on one leg while the opposite foot is lifted. Compensate by swaying of leaning left when right foot is raised.
Caused by myopathy
What is a scissors gait?
Spasms/tightness of the adductor muscles of the thighs force the knees together when walking. Legs cross over each other
Due to CST lesions
What is festination?
In parkinsonian gait, leaning further and further forward to walk, the patient runs to catch up with their center of gravity
What is dysmetria?
Overshooting/undershooting a target
What is decomposition of movement?
A normally smooth movement becomes jerky
What is a check response?
Sudden release of contracted biceps leads to striking the face
Describe hemispheral cerebellar syndrome
Ipsilateral limbs affected (kinetic tremor, dysmetria, dysdiadochokinesia, rebound) due to infarction, hemorrhage, tumor, or MS lesion
Describe vermal syndrome
Trunk affected (unsteady standing/walking, tremor, postural impairment, gait ataxia) from hemorrhage, tumor, MS or degenerative disorders
What is the most common type of spinocerebellar degeneration?
Friedreich’s ataxia
3 types of tremor
Resting tremor (seen in parkinsonism) Postural tremor (familial essential tremor) Kinetic tremor (cerebellar disease)
What is choreoathetosis?
Slow writing continual limb movements with brief irregular flowing dancelike movements of the limbs, trunk and face.
Caused by a lesion in the caudate nucleus or dopaminergic medications
What is hemiballismus
Rapid, violent flinging movements of proximal upper and lower limbs on one side caused by a lesion of the contralateral STN
2 types of dystonia
Focal: torticollis
Generalized
What is Tourette’s syndrome?
Tics of motor and vocal muscles
Inherited, with variable penetrance, M>F
Associated with ADD and behavioral problems
Lesion unknown
What is myoclonus?
Rapid shocklike bilateral movement caused by diffuse encephalopathies (CJD) or medical diseases (renal or hepatic failure, anoxia)
What is asterixis?
Flapping tremor due to diffuse encephalopathies or medical diseases (renal/hepatic failure)
Drugs for Essential tremor?
Beta blockers
Barbiturates
Drugs for choreoathetosis, hemiballismus, tics?
Dopamine antagonists
Drugs for dystonia?
Anticholinergics
Benzodiazepines
BoTox
