Cerebellum Flashcards
What are hereditary disorders that affect the cerebellum?
Friedreich ataxia
Spinocerebellar ataxias
What is the cerebellum?
Although referred to as ‘Little brain’ the cerebellum contains nearly four times the number of neurons as the cerebral cortex.
Cerebellum compares intended movement with actual movement and makes adjustments as necessary.
Damage results in impaired coordination and postural control. No change to sensation or strength.
Largest part of hindbrain.
Fills most of posterior cranial fossa.
Separated from occipital lobe by tentorium cerebelli.
Separated from posterior part of pons and medulla oblongata by 4th ventricle
What are acquired conditions that affect the cerebellum?
Multiple sclerosis, cerebellar strokes, traumatic brain injury, or toxin exposure, or they may be idiopathic.
Systemic disorders include alcoholism (alcoholic cerebellar degeneration), hypothyroidism
In children, primary brain tumors (medulloblastoma, cystic astrocytoma) may be the cause.
In humans, the most common cause of a toxic lesion to the cerebellar circuitry isalcohol related, but the cerebellum is also a main target of drug exposure (such as anticonvulsants, antineoplastics, lithium salts, calcineurin inhibitors), drug abuse and addiction.
How is the cerebellum anatomically divided?
Anatomically divided into 3 lobes:
Anterior, Posterior, & Flocculonodular
The inferior part of the posterior lobe is called the cerebellar tonsil.
Clinical significance – Increased ICP can force the tonsils into foramen magnum, compromising 4th ventricle and brainstem structures that regulate breathing and cardiovascular activity.
Descent seen in Chiari malformation as previously discussed.
Vertically the cerebellum can be divided into three functional regions. What are they?
Midline Vermis - Spinocerebellum
Paravermis - Spinocerebellum
Lateral hemisphere - Cerebrocerebellum
Each vertical projection responsible for specific movements.
Each vertical section projects to specific cerebellar nuclei or to vestibular nuclei (brainstem)
What are the nuclei of cerebellum?
Four paired masses of grey matter known as the deep cerebellar nuclei are located within white matter
Nuclei lie above 4th fourth ventricle
From medial to lateral:
Fastigial Nucleus
Globose Nucleus
Emboliform Nucleus
Dentate Nucleus
Their axons form the cerebellar outflow in the superior and inferior cerebellar peduncles
What are the afferents to cerebellum?
Primarily carried via inferior & middle cerebellar peduncles
Inputs seem to modulate cerebellar activity
Most afferent fibres send branches to deep cerebellar nuclei
What are the Efferents from Cerebellum?
Deep cerebellar nuclei Superior cerebellar peduncle Contralateral red nucleus Contralateral thalamic nuclei Motor cortex
Modulate activity in contralateral motor cortex
Double cross over – Cerebellar disease often presents with unilateral symptoms.
The vestibulospinal tract iscomprised of a lateral and medial pathway. The function of these tracts is to maintain equilibratory reflexes from the input of the vestibular apparatus. They will reach the axial muscles, i.e. intercostal and back muscles, as well as the extensors of the limbs.
The primate reticulospinal tract is usually considered tocontrol proximal and axial muscles, and to be involved mainly in gross movements such as locomotion, reaching and posture. This contrasts with thecorticospinal tract, which is thought to be involved in fine control, particularly of independent finger movements.
What is the Vestibulocerebellum?
(link with vestibular system) – regulates equilibrium – Influence postural control via vestibulospinal tracts following input to vestibular nuclei. Involved in eye movements.
What is the Spinocerebellum?
named for connections with spinal cord – coordinates gross limb movement and is the functional name for the vermis and paravermal regions. Receives motor information from cortex, spinal cord level, and movements or postural adjustments from proprioceptors. Damage would cause reaching tasks to be jerky and inaccurate for example.
What is the cerebrocerebellum?
named for connections with cortex – coordinates precise, distal voluntary movements – functional name for the lateral hemispheres. Damage to this area would cause clumsiness on gripping an object or fastening a button for examples.
What are signs of cerebellar dysfunction?
Signs of motor function of cerebellar origin include abnormal movement that does not change with or without use of vision.
Abnormalities of posture, eye movements, and voluntary movement.
Unilateral cerebellar lesions cause impairments on the same side of the body. Information in spinocerebellar tracts remain ipsilateral. Cerebellar afferents project to the contralateral cerebral cortex and red nucleus, whose descending tracts decussate.
What is cerebellar ataxia?
Ataxic movements common to all cerebellar lesions are normal strength, jerky, and inaccurate.
Lesions to the vermis or flocculonodular lobe result in truncal ataxia.
Lesions in the paravermal region result in gait and limb ataxia. Ataxic gait = pt will increase base of support.
Lesions to lateral cerebellum – hand and finger ataxia. Speech problems.
How do you assess a patient’s gait?
Observe patient’s normal gait:
Stance – a broad-based gait is noted in cerebellar disease
Stability– can be staggering, often slow and unsteady – similar to alcohol intoxication
In unilateral cerebellar disease, the patient can veer towards the side of the lesion.
Tandem (‘heel to toe’) walking – ask the patient to walk in a straight line with their heels to their toes.
Exaggerate any unsteadiness.
Sensitive at assessing the function of the cerebellar vermis.
First function to be lost in alcoholic cerebellar cortical degeneration.
In cerebral dysfunction how is speech displayed?
Slurred
