THE CEREBELLUM has long been known to be essential for smooth and precise motor function and balance. The combination of postural instability and a staggering gait is a sign of cerebellar dysfunction. Falls are frequently associated with postural disorders and ataxia.
For many years, it was thought that postural and balance disorders in cerebellar dysfunction weren't treatable. However, several recent studies suggest that rehabilitation can relieve postural disorders associated with cerebellar ataxia and can help to reduce or prevent falls and injuries.1
It's also widely accepted that the cerebellum has significant involvement in cognitive and neuropsychiatric processes. Recent evidence supports the view that executive functions such as cognition, behavior, personality, decision making, judgment, and moderating social behavior depend on cerebellar integrity.2
This article discusses our current understanding of cerebellar function and the implications for nursing practice, including how to assess for cerebellar dysfunction.
Cerebellar anatomy and physiology
The cerebellum, which is Latin for “little brain,” is located below the tentorium cerebelli in the posterior cranial fossa. (See Mapping cerebellar anatomy.) Besides influencing motor function and maintaining posture and balance, this structure receives, processes, and modulates somatosensory, visual, auditory, vestibular, and proprioceptive input from all regions of the brain. The cerebellum functions as a rapid, corrective feedback loop, smoothing, coordinating, and sequencing movements.3,4
Because of its connections to the visual cortex and vestibular and ocular motor nuclei, the cerebellum is also essential for smooth eye movements. Circuits within the cerebellum help control various sensorimotor behaviors, such as sitting, standing, walking, reaching, and grasping.4
The many possible causes for cerebellar dysfunction include age-related degeneration, ischemia, infarction, vascular dissection, hemorrhage, infection, exposure to toxins, and traumatic injury. Unlike an injury to the cerebral cortex, which results in signs and symptoms that are contralateral to the injury, unilateral damage to the cerebellum results in ipsilateral or same-side dysfunction.5
Depending on the extent of cerebellar dysfunction, a patient may have one or a combination of signs and symptoms. Examples can include headache, dizziness, vertigo, nausea, vomiting, diplopia, blurred vision, alteration in speech (dysarthria), and focal motor weakness. Clinical signs can also include lack of movement coordination, imbalance, abnormal extraocular movements such as nystagmus, and gait abnormality.5
Cerebellar infarction represents 3% of all ischemic strokes in the United States, or about 27,400 new cerebellar infarctions each year.5 Hearing loss is common with anterior inferior cerebellar infarction, and intractable hiccups may be seen in posterior inferior cerebellar infarction.6
What recent research reveals
Anatomical, clinical, and neuroimaging evidence has shown that the cerebellum has significant involvement in a range of human functions: cognition, attention, learning, working memory, social behavior, emotions, eating habits, impulse control, feelings such as regret, beliefs, and neuropsychiatric disorders.7,8 Studies using advanced magnetic resonance imaging (MRI) techniques such as functional MRI have shown that cerebellar activation increases when a person processes more complex cognitive and behavioral tasks. New data support the role of the cerebellum as a modulator of mental, psychological, and social functions.8-12
Evidence from anatomical, clinical, and imaging studies shows that right-sided cerebellar lesions lead to verbal deficits, whereas left-sided cerebellar lesions cause visuo-spatial deficits. Lesions in an area of the cerebellum known as the vermis have been associated with behavioral alterations and impaired executive functions such as speech, language, judgment, planning, and information processing.8-12
The cerebellum is now understood to be specifically involved in certain neuropsychiatric disorders, including anxiety, attention deficit hyperactivity disorder, bipolar disorder, major depressive disorder, autism spectrum disorder (ASD), and schizophrenia. For example, accumulating evidence indicates that multiple cerebral-cerebellar circuits are anatomically and functionally abnormal in patients with ASD.2,9,11
Cerebellar dysfunction has long been known to have direct involvement in the motor manifestations of multiple sclerosis (MS) including gait ataxia, poor coordination of the hands, and intention tremor. Cerebellar dysfunction is also involved in the cognitive decline that can be seen in patients with MS.12
Although the cerebellum is known to have a significant role in cognition and neuropsychiatric processes, we're only beginning to understand the extent of its involvement in these dysfunctions.13
Assessing cerebellar function
The following tests and special techniques can help the clinician assess for signs and symptoms of cerebellar dysfunction.
- Romberg test. To test position sense, ask the patient to stand with feet together and eyes open, then close both eyes for 30 to 60 seconds. Observe the patient's ability to stand upright with only minimal swaying. A patient with cerebellar ataxia will have trouble standing with feet together, regardless of whether the eyes are open or closed.13
- Rapid alternating movements. A patient with cerebellar dysfunction will have trouble performing one movement followed closely by the same movement in the opposite direction. Use the following exercises assess for this type of dysfunction.13
Ask the patient to strike one hand on the thigh, turn it over, then strike the back of the hand on the same place. Have the patient repeat these movements as quickly as possible, then repeat with the other hand. Note the speed, rhythm, and smoothness of the motions. (See Assessing rapid alternating movements.)
Have the patient tap the thumb's distal joint with the tip of the index finger as quickly as possible. Again observe the speed, rhythm, and smoothness of the motions.
Have the patient tap your hand with the ball of each foot in turn, and note the speed, rhythm, and smoothness of the motions.13
- Point-to-point movements. Incoordination during these exercises that worsens with the eyes closed suggests cerebellar dysfunction.
Ask the patient to touch your index finger with his or her index finger and then his or her nose alternatively several times (finger-to-nose test). Move your finger so the patient must change directions and fully extend the arm to touch it. Note the accuracy of the movement and watch for tremors. Cerebellar dysfunction may cause the finger to overshoot the target initially, and an intention tremor may appear toward the end of the movement.13 (See Assessing for tremors.) Intention tremors are absent at rest and may worsen as the patient reaches toward an object.14 (See Glossary of terms.)
Hold your finger in one place so that the patient can touch it by stretching out one arm and finger. Then ask the patient to raise the arm overhead and lower it to touch your finger several times. Then ask the patient to perform the same maneuver several times with closed eyes. Repeat the exercise with the opposite arm.
Ask the patient to place one heel on the opposite knee, then run it down the shin to the big toe (heel-to-shin test). Repeat with the eyes closed. Repeat on the opposite side. In cerebellar dysfunction, the heel may overshoot the knee and then oscillate from side to side down the shin. The patient may lift the heel too high because of a loss of position sense.13
In patients with cerebellar dysfunction, these point-to-point movements are clumsy, unsteady, and variable in speed. The patient may display consistent deviation to one side.
- Tremors. Patients with cerebellar dysfunction may demonstrate an abnormal head tilt at rest, or you may see a rhythmic nodding tremor of the head from side to side. Abnormal involuntary movements such as myoclonic jerks and choreiform movements can occur with extensive cerebellar disease.5
- Ask the patient to pick up an object; tremors will appear or intensify when the hand nears the object.
- Gait. Ask the patient to walk across the room or down the hall, turn, and come back as you observe posture and balance. Normally the arms swing easily and the patient makes turns smoothly without losing balance.
- Ask the patient to walk heel-to-toe in a straight line (tandem walking). An uncoordinated reeling gait (ataxia) may become more apparent during tandem walking. (See Assessing the patient's gait.) Also ask the patient to walk on the toes, then on the heels to assess balance.13
- Nystagmus. This fine rhythmic oscillation of the eyes can impair the ability to focus on stationary or moving targets and increases fall risk. Assess for this by examining extraocular movements and visual acuity.14
- Speech disturbances. Scanning dysarthria may manifest as slurred, slow, deliberate, and/or explosive speech. You may hear lengthy pauses between words or even syllables. Assess for these signs by engaging patients in conversation or note when they repeat a phrase.14,15
Because of the possibility for cognitive, behavioral, memory, and emotional dysfunction, these functions should be evaluated as well.5 For more information, see bonus content at www.nursing2017.com.
Implications for practice
Cerebellar dysfunction can lead to many cognitive, behavioral, muscular, visual, and equilibrium impairments; any of these can cause significant complications and affect recovery from injury or illness. For example, swallowing difficulties could lead to impaired nutrition, dehydration, ineffective breathing, or aspiration, which can cause pneumonia and result in the need for mechanical ventilation. The nurse or speech therapist should perform a bedside swallow assessment before the patient takes any oral fluids, food, or medication.16
Perform a validated falls risk assessment to determine degree of risk and initiate appropriate preventive interventions. Ataxia and poor balance when standing and even with sitting increase the risk of falls and injury. A reeling gait will show as head tilted toward the side of the cerebellar lesion with a high risk for falling to that side.8,10
Fatigue and weakness are common with cerebellar dysfunction and also increase the risk of falls. Patients with impaired vision may be unable to avoid obstacles and negotiate stairs, leading to falls.8,10
In patients with cerebellar dysfunction, voluntary movements such as reaching and grasping are often imprecise. This can result in deficits in self-care, including inability to complete activities of daily living such as dressing, toileting, hygiene, and feeding. Remember that patients may also be unable to hold a pen and write legibly, or type accurately on a keyboard. Neuropsychiatric, personality, and mood disorders associated with cerebellar dysfunction may require interventions such as counseling and/or pharmacologic agents.1-3,17
Cerebellar dysfunction can interfere significantly with a patient's ability to perform many activities of daily living. Use your assessment findings to plan nursing care that promotes patient safety and optimizes recovery.
Mapping cerebellar anatomy
(A) Dorsal view of the cerebellum indicating the positions of the anterior, posterior, and flocculonodular lobes and the midline region called the vermis.
(B) Dorsal view of the brainstem after removal of the cerebellum. The connections of the cerebellum to the brainstem are indicated by the presence of the inferior, middle, and superior cerebellar peduncles.
Assessing rapid alternating movements13
Ask the patient to strike one hand on the thigh, turn it over, then strike the back of the hand on the same place. Have the patient repeat these movements as quickly as possible, then repeat with the other hand.
Glossary of terms
Chorea is a hyperkinetic involuntary movement disorder characterized by rapid and unpredictable contractions. It primarily affects distal limbs, but the face and trunk may also be affected. Movements are nonpatterned and their speed, timing, and direction vary.18
Myoclonus is characterized by brief, shocklike, involuntary movements caused by muscular contractions (positive myoclonus) or inhibitions (negative myoclonus or asterixis). Patients may describe myoclonus as jerks, shakes, or spasms.19
Nystagmus, which impairs vision and depth perception, is characterized by involuntary, repetitive, uncontrolled eye movements from side to side, up and down, or in a circular pattern. The speed of eye movements varies and both eyes are usually affected. This disorder prevents a steady view of objects by both eyes.20
Scanning dysarthria disrupts normal speech patterns, with abnormally long pauses between words or even individual syllables. It's characterized by slow, slurred, and monotonous speech and is associated with oral motor ataxia.14,18
Tremors are rhythmic oscillatory movements caused by disorders in cerebellar pathways, as in multiple sclerosis. Intention or kinetic tremors are absent at rest and may worsen as the patient's hand gets closer to a target.14
Assessing for tremors13
Intention tremors are absent at rest and may worsen as the patient reaches toward an object.
Assessing the patient's gait13
Ataxia may become more apparent when the patient walks heel-to-toe in a straight line (tandem walking).
Head to www.nursing2017.com for a video guide to assessing cognitive function.
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20. American Academy of Ophthalmology. What is nystagmus? https://http://www.aao.org