Signs of Cerebellar dysfunction & How to examine them (with mnemonic)

The cerebellum is a major part of the brain located in the posterior cranial fossa, behind the pons and medulla oblongata. It is the largest part of the hindbrain and sits astride the main sensory and motor systems in the brainstem.

Image of cerebellum (purple colored) - From Wikipedia 

The signs of Cerebellar dysfunction can be memorized with the mnemonic "DANISH".

D - Dysdiadochokinesia, Dysmetria 

A - Ataxia

N - Nystagmus 

I - Intention tremor 

S - Slurred speech 

H - Hypotonia 

Let's discuss more about the signs in detail and ways to examine it on a patient.

Signs of Cerebellar Dysfunction and how to examine them

Dysdiadochokinesia 

Dysdiadochokinesia is the inability to perform rapidly alternating opposite movements in a regular and coordinated manner. 

This difficulty arises when the motor control system fails to accurately predict the position of different body parts during rapid movements. As a result, the subsequent movement might start too early or too late, disrupting the smooth progression of motion.

How to examine dysdiadochokinesia on a patient 

To test dysdiadochokinesia in a patient ask him to rapidly pronate and supinate his forearms. 

In individuals with cerebellar lesions, these movements on the affected side tend to be slow, jerky, and incomplete. 

Here is a video showing dysdiadochokinesia 

Dysmetria 

Dysmetria is a condition characterized by the inability to control the range of movement in voluntary muscular actions. 

This results in movements that are either overshooting the intended target (hypermetria or past-pointing) or undershooting it (hypometria).

A classic example of dysmetria is past pointing, where, in the absence of proper cerebellar function, an individual will move their hand or another body part considerably beyond the intended point. The cerebellum normally initiates a motor signal to stop a movement once it has begun; without this signal, the movement goes too far. Therefore, past pointing is considered a manifestation of dysmetria.

How to examine Dysmetria on a patient 

The finger-nose test is a common clinical assessment for dysmetria. 

1. Explain the procedure to the patient. Ask for their permission to proceed.
2. Ask the patient to be in a comfortable sitting or standing position.
3. Instruct the patient to touch their nose with the tip of their index finger.
4. Then, ask them to extend their arm and touch your outstretched forefinger. Hold your finger at nearly full extension of the patient’s shoulder and elbow, or just within the patient’s arm's reach, making them stretch.
5. Instruct the patient to repeat the movement between their nose and your finger as quickly as possible.
6. Observe the smoothness and accuracy of their movements.
7. Perform the test first with the patient's eyes open and then repeated with their eyes closed.
8. To make the test more sensitive, you can change the position of your target finger. Move your finger just as the patient’s finger is about to leave their nose to avoid a false-positive result.
9. When the patient's finger approaches the target, look for any intention tremor, which is a tremor that increases as the target is approached, and there is no tremor at rest.
10. Observe for dysmetria or past-pointing, a tendency to fall short of or overshoot your finger or their nose.

When a patient with cerebellar dysfunction attempts to touch their nose or your finger with their index finger, the movements are not properly coordinated, and the finger may either pass the nose/finger (past-pointing) or hit the nose/finger inaccurately. 

Here is a video of finger to nose test

 

Ataxia 

Ataxia refers to a lack of coordination of muscle movements, which can result in unsteadiness and difficulty walking. It can arise from lesions in the cerebellum, vestibular apparatus, or peripheral nerves.

Cerebellar ataxia results from lesions in the cerebellum. It can manifest with a broad-based, unsteady gait, often described as 'drunken'. Patients may have difficulty with tandem gait (heel-toe walking).

How to examine Ataxia 

To examine for ataxia, a systematic approach focusing on gait, balance, and coordination is essential. It's also important to look for associated neurological signs.

1. Observation During History Taking and Initial Interaction: Pay attention to the patient's movements as they walk into the room and sit down. Note any unsteadiness, difficulty with turns, or the use of walking aids.
2. Gait Assessment: Ask the patient to walk normally. Observe their stride length, arm swing, steadiness, and any limping or other difficulties.

Here is a video demonstrating ataxic gait

Nystagmus 

Cerebellar nystagmus refers to involuntary, jerky movement of the eyes that arise due to abnormalities in the cerebellum or its connections. It is frequently horizontal but can also have vertical and torsional components. 

How to examine Cerebellar Nystagmus in a patient 

1. Observation in Primary Gaze: Ask the patient to sit and look straight ahead at a stationary target (e.g., your nose) and observe for any spontaneous nystagmus. Note the direction and characteristics if present.
2. Assessment of Gaze-Evoked Nystagmus: 

• Hold your finger or a pen about an arm's length away, level with the patient's eyes. 
• Ask the patient to follow your finger with their eyes only, keeping their head still. 
• Move your finger slowly and smoothly to the right, then to the left, and then up and down, tracing an 'H' pattern. 
• Move to about 30 degrees from the central gaze position. Avoid extremes of gaze, as physiological nystagmus can occur. 
• Observe the patient's eyes for any oscillations (nystagmus) during these movements. 
• Note the direction of the nystagmus (horizontal, vertical, rotatory, or multidirectional).

Here is a video showing different types of nystagmus 

Intention Tremor 

Intention tremor in cerebellar disease is a type of tremor that appears during voluntary movement and worsens as the movement approaches its target. It is absent when the muscles are at rest.

Characteristics: Intention tremor is also known as action tremor or target-seeking tremor. It is often described as having a fairly low tremor frequency and sometimes a quite large amplitude. The amplitude becomes more marked as the patient’s finger or limb approaches the intended target, such as their nose or the examiner's finger.

Cerebellar Origin: Intention tremor is a direct consequence of cerebellar damage. The cerebellum plays a crucial role in coordinating smooth and learned movements initiated by the motor cortex. Lesions in the cerebellum disrupt this coordination, leading to imprecise movements. The intention tremor specifically arises due to the loss of cerebellar connections in the brainstem.

How to examine Intention Tremor in a Patient 

Intention tremor is typically assessed during the finger-nose test, where the patient is asked to touch their nose and then the examiner's finger repeatedly. The tremor becomes more apparent as the finger approaches the target.

It's important to differentiate intention tremor from other types of tremor, such as resting tremor seen in Parkinson's disease, which is present at rest and often decreases with movement, and essential tremor, which is typically a postural or action tremor present during maintained postures and movement, but not at rest.

Here is video showing intention tremor 

Slurring of Speech 

Slurring of speech is a characteristic feature of cerebellar lesions, and it is a type of dysarthria resulting from the cerebellum's role in coordinating the muscles involved in speech articulation.

How to examine Slurring of Speech in a patient 

Slurred speech in cerebellar lesions can be assessed by listening to the patient's spontaneous speech and asking them to repeat phrases that involve different muscle groups for articulation. The examiner may note the rhythm and clarity of speech. Asking the patient to say words like "Hippopotamus" or "West Register Street" can help highlight the jerky and irregular nature of cerebellar speech.

Hypotonia 

Hypotonia, or decreased muscle tone, is a feature that can be observed in cerebellar lesions.

Hypotonia in cerebellar lesions is often described as floppy limbs. It can also manifest as an arm drift when the patient extends their arms, with the arms drifting upwards due to the weakness of agonist muscles.

Neurological Basis: The cerebellum exerts a facilitatory influence on spinal motor neurons. When there is a cerebellar lesion, this facilitatory influence is lost, leading to a reduction in muscle tone.

How to examine Hypotonia in a Patient 

Hypotonia can be assessed during the neurological examination by passively moving the patient's limbs and feeling the resistance to movement. In cerebellar hypotonia, there is a decreased resistance. The rebound phenomenon can also be an indicator; when a displaced outstretched arm is released, it may fly up past the original position due to the hypotonia.

It's important to note that hypotonia can also be seen in other conditions, such as lower motor neuron lesions, the early phases of cerebral or spinal shock, and certain metabolic disorders. Therefore, it should be considered in conjunction with other neurological findings to diagnose a cerebellar lesion.

It's important to consult a health professional if any of the above mentioned signs are seen in any patient for further evaluation and proper diagnosis of the disease.

You can take this short quiz on cerebellar dysfunction if you have time 😃.

That's all for today guys. Hope it was helpful 😊.