Cerebellar Neurological Signs

Issues of Concern

Lesions of the cerebellum produce neurological signs that are easy to recognize and have been shown to have excellent inter-rater reliability.[1] These signs evolve secondary to lesions in the vestibulocerebellar, vestibulospinal, and cerebellar ocular motor tracts. However, many signs, such as gait ataxia and nystagmus, may present in non-cerebellar lesions. A detailed neurological exam and a good history assist in accurate localization.

Clinical Significance

Early and accurate identification of these signs helps facilitate appropriate diagnostic testing and management, especially in time-sensitive emergencies such as acute cerebellar infarction. Utilizing a combination of signs at the bedside, such as HINTS testing, is useful in broadly differentiating neurological signs of peripheral nervous system etiology from central etiologies (such as cerebellar lesions).[2]

Nursing, Allied Health, and Interprofessional Team Interventions

Common cerebellar neurological signs are as follows:

Extraocular Movements

• Nystagmus: The pattern of nystagmus differs in etiologies of central origin, such as a cerebellar lesion, compared to peripheral origin, such as vestibulopathy. In etiologies of peripheral origin, the nystagmus is unidirectional irrespective of the gaze direction and worsens when the patient directs their gaze towards the healthy ear (Alexander law).[3][4]

• Impaired smooth pursuits: Patients cannot track objects with smooth eye movements in cerebellar lesions. Instead, catch-up saccades are the presentation.[5]

• HINTS exam: The HINTS exam combines 3 maneuvers (Head Impulse test, Nystagmus, and the test of Skew) to help differentiate vertigo of central etiology from peripheral etiology. A detailed description of the HINTS exam appears in PubMed in the article published by Kattah JC et al.[6]  
  • Head Impulse test: In vestibular disorders that cause vertigo, the head impulse test is often positive. The performance of this test is as follows:
    • The examiner sits across the patient and holds the patient's head between both palms. The examiner asks the patient to fix the gaze on the examiner's nose. The head is rotated slightly laterally, about 10-20 degrees to 1 side. Subsequently, the examiner brings the head back to the primary position in a swift motion while continually observing the patient's eyes. Individuals with an intact vestibular system (and thus an intact vestibulo-ocular reflex) can maintain their gaze on the examiner's nose. A corrective horizontal saccade is seen in a patient with unilateral vestibular damage when the head rotates to the primary position from the side with the vestibular lesion. The test is then repeated for the contralateral side. 
    • It is essential to rule out cervical spine or paraspinal musculature lesions before performing this test. If the examiner doubts the integrity of the neck or the spine, it is best to avoid this test altogether. 
  • Nystagmus: In comparison to the nystagmus of peripheral etiology as described above, the nystagmus of central etiology has the following features:
    • Bi-directional (gaze-evoked): The direction of nystagmus changes with the direction of gaze
    • Central nystagmus may also be vertical, which is uncommon in nystagmus of peripheral etiology. 
  • Test of Skew: In lesions involving the brainstem, vertical malalignment of the eyes may present (skew deviation). The alternate cover test can demonstrate this. In this test, the examiner asks the patient to look straight ahead and then alternately covers each eye. A corrective vertical or oblique saccadic movement is appreciated if a skew deviation exists.

• If any of the 3 tests point to a central etiology, the likelihood of a central etiology, such as a posterior circulation stroke, should merit strong consideration.[7][6] It is important to note that every test should be taken in the right clinical context and should not be used as the sole criteria to confirm or refute a diagnosis without considering the history, the rest of the neurological exam, and other investigations. 

Scanning speech: Cerebellar disorders can cause ataxic speech, also known as scanning speech, where the patient usually breaks words into respective syllables.[8]

Dysmetria[9]

• Finger-to-nose test: This can be tested in the upper limb by having the patient reach out and touch the examiner's index finger with their index finger and then touch their nose with the same finger. In a patient with a lesion in the cerebellar hemisphere, the ipsilateral arm manifests an intention tremor while nearing the target. This tremor occurs due to overshooting or undershooting of the patient's index finger due to improper coordination of movements. 

• Heel-to-shin test: The examiner asks the patient to move their heel across the shin in a proximal to distal motion for the lower extremities. In a hemispheric cerebellar lesion, the patient cannot trace the shin in a straight line and moves the heel from side to side.

Adiadochokinesia (dysdiadochokinesia)[5]

• Patients with cerebellar lesions are unable to execute rapid alternating movements properly. The examiner asks the patient to place the palm on the knee and then perform rapid alternate pronation and supination of the forearm. Affected individuals have difficulty executing such alternating movements, which appear jerky and irregular. 

Rebound Phenomenon[5]

• With elbows resting on the legs on the table, the examiner asks the patient to flex the elbows against the examiner's resistance. The examiner then abruptly stops providing resistance. Unaffected patients can contract the antagonist muscle (triceps), so there is no to minimal elbow flexion. In individuals with cerebellar lesions, there is exaggerated flexion of the ipsilateral elbow due to the failure of timely contraction of the antagonist muscle. This phenomenon often presents exaggeratedly in spastic limbs. Other upper extremity joints can also undergo testing in this fashion with similar results.

Intention Tremor[10]

• Intention tremor is a kinetic tremor (most prominent when performing a task); the previously mentioned finger-to-nose test can elicit this sign. The tremor worsens as the patient approaches the examiner's finger. 

Ambulation

• Stance and posture: Patients tend to have a broad-based stance in cerebellar lesions. The examiner may notice side-to-side or back-and-forth swaying of the body while the patient is standing; this is known as titubation.

• Gait: The gait in cerebellar lesions is reminiscent of acute alcohol intoxication.[5] The patient tends to stagger or sway from side to side and walks with a broad base, known as an ataxic gait.[11] Differential diagnoses for cerebellar ataxia include a myriad of conditions like hydrocephalus, Arnold-Chiari malformation, adult-onset leukodystrophy, alcoholic cerebellar degeneration, hypomagnesemia, and various infectious etiologies, including cerebellar abscess, malaria, Lyme disease, HIV encephalitis, and prion disease. 

• Tandem walk: Individuals with cerebellar lesions are unable to walk in tandem.[12] The test is performed as follows: The examiner asks the patient to walk in a straight line with the heel of the leading foot touching the toes of the lagging foot as if walking on a tightrope. This sign may also be seen in sensory ataxia or vestibulopathy. Thus, it is essential to check for other signs, such as Romberg's sign, to differentiate sensory ataxia or vestibulopathy from cerebellar ataxia. 
• Absence of Romberg's sign: The examiner asks the patient to stand with eyes open, feet close together, and arms by the side. The patient is then asked to close their eyes. Romberg's sign is positive if there is disproportionate swaying or patient falling with eyes closed compared to eyes open. This sign is present in lesions of the sensory afferent pathway or the vestibular system. Even with eyes open, excessive swaying can be seen in cerebellar lesions.[13]

Hypotonia

• Damage to half of the cerebellum can lead to ipsilateral hypotonia.

Cerebellar Mutism [14]

• If an injury occurs to the central cerebellum, such as from a tumor or surgery, a patient may have mutism for days to indefinitely after the injury.

A mnemonic to remember some of the cerebellar signs is DANISH.

• Dysdiadokinesia / dysmetria
• Ataxia
• Nystagmus
• Intention tremor
• Speech - slurred or scanning
• Hypotonia