Coordination

Coordination – Anatomy

Introduction

The principle area of the brain that is examined by the coordination exam is the cerebellum. The cerebellum is important for motor learning and timing of motor activity. It fine-tunes the force of agonist and antagonist muscle activity simultaneously and sequentially across multiple joints to produce smooth flowing, goal directed movements. Cerebellar dysfunction results in decomposition of movements and under and over shooting of goal directed movements (dysmetria). Decomposition of movement and dysmetria are the main elements of ataxia.

Subdivisions

The cerebellum has 3 functional subdivisions, which function as feedback and feed forward systems.

Vestibulocerebellum

The first is the vestibulocerebellum. This consists of the connections between the vestibular system and the flocculonodular lobe. Dysfunction of this system results in nystagmus, truncal instability (titubation), and truncal ataxia.

Spinocerebellum

The 2nd subdivision is the spinocerebellum. This system consists of the connections between the cutaneous and proprioceptive information coming from the spinal cord to the vermis and paravermis regions with corrective feedback predominantly to the muscles of truncal stability and gait. Dysfunction of this system results in gait and truncal ataxia.

Midline Ataxia

Clinically, the ataxic syndromes caused by vestibulocerebellar and spinocerebellar disease are lumped together and are called midline or equilibratory (gait) ataxias. The hallmarks of these midline ataxic syndromes are truncal instability manifested by titubation (tremor of the trunk in an anterior-posterior plane at 3-4 Hz) and gait ataxia (wide based, irregular steps with lateral veering).

Cerebrocerebellum

The 3rd subdivision of the cerebellum is the cerebrocerebellum. This system consists of connections from the cerebral cortex (predominantly motor) to the cerebellar hemispheres then back to the cerebral cortex. This system is important in motor planning. Dysfunction of the cerebellar hemispheres results in ataxia of speech (scanning dysarthria) and ataxia of the extremities (appendicular ataxia). It is important to remember that ataxia caused by disease of the cerebellar hemispheres will be ipsilateral to the dysfunctional hemisphere. The findings of appendicular ataxia are hypotonia, decomposition of movement, dysmetria, and difficulty with rapid alternating movements (dysdiadochokinesia).

Exam Tests

The following tests of the neuro exam can be divided according to which system of the cerebellum is being examined:

Vestibulocerebellum and spinocerebellum (midline):

• Station
• Walking
• Tandem gait

Cerebrocerebellum (appendicular):

• Rapid alternating movements
• Finger-to-nose
• Toe-to-finger
• Heel-to-shin
• Rebound and check reflex
• Speech

Potential Traps

Although incoordination is primarily a symptom of cerebellar disease, it can also be seen from other causes such as:

1. Sensory dysfunction-loss of large myelinated sensory axons serving proprioception. This causes a sensory ataxia. Key distinguishing feature for this type of problem- a positive Romberg and loss of position sense on the sensory exam.
2. Vestibular dysfunction. Key distinguishing feature- vertigo.
3. Corticospinal tract disease can cause incoordination of the distal extremities. Key distinguishing feature- UMN signs.

Clinical Pearls

Appendicular ataxia is maximum at the greatest extent and end point of the motor act so make sure you have the patient get to the full extent of the motor act when testing for ataxia.

Remember that the Romberg test is a test for position sense and not of cerebellar function.

Coordination – Normal Exam

Speech Rapid Alternating Movements

Having the patient say lah-pah-kah can test rapid alternating movements of the tongue, lips, and palate.

Tremor

Patient’s arms are held outstretched and fingers extended. Watch for postural or essential tremor.

Rebound

Tap outstretched arms. Patient’s arms should recoil to original position.

Check Reflex

Examiner pulls on actively flexed arm then suddenly releases. The patient should be able to check or stop the arm’s movement when released.

Hand Rapid Alternating Movements

Finger tapping, wrist rotation and front-to-back hand patting. Watch for the rapidity and rhythmical performance of the movements noting any right-left disparity.

Finger-to-nose

The patient moves her pointer finger from her nose to the examiner’s finger as the examiner moves his finger to new positions and tests accuracy at the furtherest outreach of the arm.

Foot Rapid Alternating Movements

Patient taps her foot on the examiner’s hand or on the floor.

Toe-to-finger

The patient touches her toe to the examiner’s finger repetitively as the examiner moves his finger to new positions.

Heel-to-shin

The patient places her heel on the opposite knee then runs the heel down the shin to the ankle and back to the knee in a smooth coordinated fashion.

Station

Have the patient stand still. Note the position of the feet and how steady the patient is with eyes open. In the demonstrated exam, the patient is asked to hop and pat at the same time. This is a good way to test upper and lower extremity coordination and balance simultaneously.

Natural gait

The patient should be observed walking as she normally would.

Tandem gait

The patient is asked to walk heel-to-toe. Note steadiness. Tandem gait requires the patient to narrow the station and maintain balance over a 4-5 inch width. Patients with midline ataxias have difficulty with tandem gait.

Coordination – Abnormal

Speech Rapid Alternating Movements

Impaired speech articulation of cerebellar origin is characterized by being slow, indistinct, and scanning (scanning refers to decomposition of words into monosyllabic parts and loss of normal phrasing and intonation).

Tremor

A cerebellar intention tremor (1st scene in this movie) arises mainly from limb girdle muscles and is maximal at the most demanding phase of the active movement. This must be distinguished from a postural tremor (fine distal 8-13 Hz)(2nd scene) or resting tremor (coarse distal 5-6 Hz pill-rolling type of tremor)(3rd scene).

Rebound

Increased range of movement with lack of normal recoil to original position is seen in cerebellar disease.

Check Reflex

The patient is unable to stop flexion of the arm on sudden release so the arm may strike the chest and doesn’t recoil to the initial position. This is most likely due to failure of timely triceps contraction.

Hand Rapid Alternating Movements

Movements are slow and irregular with imprecise timing. Inability to perform repetitive movements in a rapid rhythmic fashion is called dysdiadochokinesia.

Finger-to-nose

Under (hypometria) and over (hypermetria) shooting of a target (dysmetria) and the decomposition of movement (the breakdown of the movement into its parts with impaired timing and integration of muscle activity) are seen with appendicular ataxia.

Foot Rapid Alternating Movements

Movements are slow and irregular with imprecise timing of agonist and antagonist muscle action.

Toe-to-finger

Same as finger-to-nose except for the lower extremities. For both the upper and lower extremities, it is important to always compare right versus left.

Heel-to-shin

The patient with ataxia of the lower extremity will have difficulty placing the heel on the knee with a side-to-side irregular over- and undershooting as the heel is advanced down the shin. Dysmetria on heel-to-shin can be seen in midline ataxia syndromes as well as cerebellar hemisphere disease so there is overlap between the two types of ataxias for this finding.

Station

Patient’s feet will be placed wider apart then usual in order to maintain balance (broad or wide-based station). Midline ataxias cause instability of station with eyes opened or closed.

Natural gait

Wide-based, unsteady, irregular steps with lateral veering; ataxia is most prominent when sudden changes are needed such as turning, standing up or stopping.

Tandem gait

Patients with ataxia have difficulty narrowing the station in order to walk heel to toe. Tandem gait is helpful in identifying subtle or mild gait ataxia.