CELLEBELAR, CELLEBELAR, the symptoms of disordersthe symptoms of disorders

FUNCTIONSFUNCTIONS

• The cerebellum is involved in the The cerebellum is involved in the • coordination of movement, coordination of movement,

• balance for walking and standingbalance for walking and standing • and muscle tone. and muscle tone.

• A simple way to look at its purpose is that it A simple way to look at its purpose is that it compares what you thought you were going to do compares what you thought you were going to do (according to motor cortex) with what is actually (according to motor cortex) with what is actually happening down in the limbs (according to happening down in the limbs (according to proprioceptive feedback), and corrects the proprioceptive feedback), and corrects the movement if there is a problem. The cerebellum is movement if there is a problem. The cerebellum is also partly responsible for motor learning, such as also partly responsible for motor learning, such as riding a bicycle.riding a bicycle.

• Unlike the cerebrum, which works entirely on Unlike the cerebrum, which works entirely on a contralateral basis, the a contralateral basis, the cerebellum works cerebellum works ipsilaterallyipsilaterally..The cerebellum ("little brain") has The cerebellum ("little brain") has convolutions similar to those of cerebral convolutions similar to those of cerebral cortex, only the folds are much smaller. cortex, only the folds are much smaller.

• Like the cerebrum, the cerebellum has Like the cerebrum, the cerebellum has • anan outer cortex, outer cortex, • an inner white matter, an inner white matter, • and deep nucleiand deep nuclei below the white matter. below the white matter.• There are worm (vermis), two hemispheres

and three branches (peduncles).

NUCLEINUCLEI• The 3 deep nuclei are • fastigial, • interposed, • dentate. • The fastigial nucleus is primarily

concerned with balance, and sends information mainly to vestibular and reticular nuclei. The dentate and interposed nuclei are concerned more with voluntary movement, and send axons mainly to thalamus and the red nucleus.

• The 3 highways are the peduncles.

• There are 3 pairs:

• the inferior,

• middle,

• and superior peduncles.

• The 3 inputs are: Mossy fibers from the spinocerebellar pathways, climbing fibers from the inferior olive, and more mossy fibers from the pons, which are carrying information from cerebral cortex. The mossy fibers from the spinal cord have come up ipsilaterally, so they do not need to cross. The fibers coming down from cerebral cortex, however, DO need to cross (remember the cerebrum is concerned with the opposite side of the body, unlike the cerebellum).

• To identify cerebellar problems, the neurological examination includes assessment of gait (a broad-based gait being indicative of ataxia), finger-pointing tests and assessment of posture.

Romberg's testRomberg's test..• Ask the subject to stand

erect with feet together and eyes closed. Stand close by as a precaution in order to stop the person from falling over and hurting themselves. A positive sign is noted when a swaying, sometimes irregular swaying and even toppling over occurs. The essential feature is that the patient is unsteadier than with open eyes.

The essential features of the test are as The essential features of the test are as follows:follows:

• the subject stands with feet together, eyes open and hands by the sides.

• the subject closes the eyes while the examiner observes for a full minute.

Because the examiner is trying to elicit whether the patient falls when the eyes are closed, it is advisable to stand ready to catch the falling patient. Romberg's test is positive if the patient sways or falls while the patient's eyes are closed. Patients with a positive result are said to demonstrate Romberg's sign.

- A positive Romberg test suggests that ataxia is sensory in nature, i.e. depending on loss of proprioception.

- A negative Romberg test suggests that ataxia is cerebellar in nature, i.e. depending on localised cerebellar dysfunction instead.

• Finger-pointing test – the patient touches its nose

• Heel-knee test – the patient touches a knee by the heel of other leg.

Cerebellar tremorCerebellar tremor

• Cerebellar tremor (also known as "intention tremor") is a slow, broad tremor of the extremities that occurs at the end of a purposeful movement, such as trying to press a button or touching a finger to the tip of one’s nose.

NystagmusNystagmus

• Nystagmus is a type of eye movement characterized by alternating slow phase movements in one direction and Saccade-like quick phases in the other direction. Nystagmus may be:

DYSDIADOCHOKINESISDYSDIADOCHOKINESIS

• is the medical term for an inability to perform rapid, alternating movements.It is commonly demonstrated by asking the patient to tap the palm of one hand with the fingers of the other, then rapidly turn over the fingers and tap the palm with the back of them, repeatedly. This movement is known as a pronation/supination test of the upper extremity.

DysmetriaDysmetria

• Dysmetria (Greek: "difficult to measure") refers to a lack of coordination of movement typified by the undershoot and/or overshoot of intended position with the hand, arm, leg, or eye. It is sometimes described as an inability to judge distance or scale.

• Muscular tone is low.

DysmetriaDysmetria

• Asynergy Asynergy is defective or lack of co-is defective or lack of co-ordination between muscles, limbs or ordination between muscles, limbs or joints, resulting in a loss in movement joints, resulting in a loss in movement or speed. or speed.

• Asynergy is most likely to occur during Asynergy is most likely to occur during complex movements, where several complex movements, where several individual muscle contractions are individual muscle contractions are needed to act in unison. needed to act in unison.

• A speechA speech loses a smoothness, loses a smoothness, becomes scanned, explosion, slow.becomes scanned, explosion, slow.

Babinsky’ testBabinsky’ test – a – a patient lies, hands patient lies, hands are crossed on a are crossed on a

breast. Ask him to breast. Ask him to sit down, feet rise sit down, feet rise in place of trunkin place of trunk

• Stewart-Holms test - absence of reverse shove