the knee. This is demonstrated in Figure 21-57. A smooth movement should be seen, with the heel staying on the shin. In patients with cerebellar disease, the heel wobbles from side to side.
The ability to perform rapid alternating movements is called diadochokinesia. These motions may be tested in the upper extremity or the lower extremity. The patient can be asked to pronate and supinate one hand on the other hand rapidly. Another technique involves having the patient touch the thumb to each finger as quickly as possible. The patient may also be asked to slap the thigh, raise the hand, turn it over, and slap the thigh again rapidly. This pattern is repeated over and over as quickly as possible. These techniques are illustrated in Figure 21-58. An abnormality in performing rapid alternating movements is called adiadochokinesia.
The Romberg test is performed by having the patient stand in front of the examiner with feet together so that the heels and toes are touching. The examiner instructs the patient to extend the arms with palms facing upward and to close the eyes. If the patient can maintain this posture without moving, the test result is negative. The result is positive if the patient begins to sway and has to move the feet for balance. Another common finding is for one of the arms to drift downward, with flexion of the fingers. This is called pronator drift and is seen in patients with mild hemiparesis. The Romberg test is used to examine the posterior columns rather than actual cerebellar function. The examiner should be at the patient's side during this test because an occasional patient may suddenly sway and fall if assistance is not provided.
Foremost in the examination of cerebellar function is the observation of gait. The patient is asked to walk straight ahead while the examiner observes the gait. The patient is then instructed to return on tiptoes;to walk away again on the heels;and to return to the examiner by walking in tandem gait: one foot placed in front of the other, the heel of one foot touching the toes of the other on each step. The examiner may need to demonstrate this gait for the patient. The patient should have normal posture, and there should be normal associated movements of the arms. The examiner should pay special attention to the way in which the patient turns around. These maneuvers often accentuate cerebellar ataxia, as well as indicate weakness in the lower extremities (see Figure 20-23).
Many neurologic disorders produce striking and characteristic gaits. A patient with hemiple-gia tends to drag or circumduct a weak and spastic leg. The arm is frequently flexed at the elbow across the abdomen as the patient walks. A patient with Parkinson's disease shuffles, with short, hurried steps. The head is bowed, with the back bent over. A patient with cerebellar ataxia walks with a wide-based gait. The feet are very far apart as the patient staggers from side to side. A patient with footdrop has a characteristic slapping gait resulting from weakness of the dorsiflexors of the ankle. A patient with sensory ataxia has a high-stepping gait in which the feet are slapped down firmly, as if the person is unsure of their location. Figure 21-59 illustrates these gaits.
Figure 21-58 Techniques for testing rapid alternating movements.
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