Introduction
When normal movements such as walking, grasping, but also articulation, do not proceed smoothly, this is referred to as a coordination disorder. There may be disordered movements (ataxia), overshoot in a movement (hypermetria) or a tremor that occurs upon a purposeful movement (intention tremor).
The coordination disorder, or ataxia of the bulbar muscles, leading to dysarthria is covered in the section ‘The voice, speech and language’.
Coordination disorders can arise due to:
- insufficient muscle strength (muscular diseases, peripheral nerve injuries, pyramidal tract lesions)
- inadequate propriocepsis (conditions involving the dorsal column, polyneuropathies)
- impaired control over the centre of gravity (extrapyramidal conditions)
- vestibular conditions
- cerebellar conditions.
Diadochokinesis describes rapidly alternating movements, for example pronation and supination of the forearms. This function can be negatively influenced by pyramidal, extrapyramidal and cerebellar disorders. The term dysdiadochokinesis is then used.
The examination
Procedure
- During the examination of the gait and posture, the patient will have walked back and forth across the room, and walked heel-to-toe (tandem gait), you will have assessed whether the patient is unsteady when walking (abasia).
- In addition, have the patient walk with their eyes closed, to assess whether this leads to abasia.
- Romberg’s test should also be carried out (refer to the section ‘Gait and posture’).
The heel-to-shin test
- Ask the patient to close their eyes and to place the heel of one foot on the knee of the other leg, in one smooth movement, and to subsequently slide the heel down the front of the leg to the foot [Figure 62].
- Assess whether the patient displays hypermetria or ataxia, in other words whether the heel repeatedly misses the knee (hypermetria) and keeps sliding off the shin (ataxia) instead of maintaining constant contact.
- If you detect hypermetria and ataxia, ask the patient to repeat the task with their eyes open.
- Always compare left and right.
Figure 62
The finger-to-nose test
- Ask the patient to close their eyes and stretch their arms out to the sides.
- Ask the patient to place the index finger of one hand on their nose, making an large arch with the finger as they do so [Figure 63]. Repeat the action with the index finger of the other hand.
- Assess whether there are any signs of hypermetria or intention tremor.
- If you notice hypermetria or an intention tremor, have the patient repeat the test with their eyes open.
- Ascertain whether opening the eyes causes the coordination impairment to disappear or markedly improve.
- Compare left and right.
Figure 63
The finger-to-finger test
- Ask the patient to repeatedly move their index finger a number of times from their nose to your index finger (with their eyes open).
- You should hold your index finger about 50 cm away from the patient’s nose and keep changing the position of your finger each time [Figure 64].
- Compare left and right.
Figure 64
Diadochokinesis
- Ask the patient to make rapidly alternating movements, such as pronating and supinating their forearms [Figure 65].
- If necessary, demonstrate the action yourself.
- Compare left and right.
Figure 65
Interpretation
1. Coordination disorder due to inadequate propriocepsis.
The coordination impairment clearly increases or only becomes manifest when the patient closes their eyes.
This is known as sensory ataxia. When carrying out the heel-to-shin test and the finger-to-nose test the patient hesitates before touching the knee or the nose, misses and then correctly places the heel or the index finger. It is also important to examine the patient’s sense of motion and sense of direction.
2. Coordination disorder caused by a cerebellar condition.
Depending on the severity of the cerebellar condition, the described tests will be abnormal to a greater or lesser extent. With severe cerebellar ataxia, the patient will demonstrate gross hypermetria. With less severe ataxia, only an intention tremor will be visible and an abnormal finger-to-finger test. It is also important to examine the patient’s handwriting and to assess whether this is large and irregular (megalography).
3. Coordination disorder caused by a vestibular condition.
As with sensory ataxia, with a vestibular condition the coordination disorder will increase if the patient shuts their eyes. There are, however, large differences which makes it easier to differentiate between the two. With a vestibular condition the patient will usually complain of dizziness, that the room is spinning or that the horizon is skew. A nystagmus is often present. The patient’s tendency to fall will always be to one side. With the pointing tests involving the finger and the heel, the patient will always misplace the finger or heel to the same side, with both the left and right finger and left and right heel, and always in the direction of the slow phase of the nystagmus. The vestibulocochlear nerve function should also be examined.
4. Coordination disorder caused by an extrapyramidal condition.
The pointing tests are not impaired in patients with an extrapyramidal condition. A tremor that may be present will, in fact, disappear when a purposeful movement is carried out. When walking and standing the patient may have problems relating to balance, or due to severe involuntary movements, or because of a difficulty with initiating or ending movements. One example is a patient with Parkinson’s disease, who will have difficulty stopping when walking or will involuntarily walk faster (propulsion) or, when walking backwards, will show a tendency to fall backwards (retropulsion). The muscle tone should also be examined, looking for signs of rigidity. You should also assess the patient’s handwriting and observe whether this is extremely small (micrography).