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WHAT IS ATAXIA?1

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Ataxia is defined as a syndrome characterized by lack of coordination of movements and posture secondary to a variety of reasons:

  1. Sensory ataxia: Proprioceptive loss causes the brain to be unaware of the position of limbs and trunk. Thus, there is incoordination of movements because of incomplete feedback. For example, the major mechanism by which we are able to maintain our balance while walking on uneven ground comes from the proprioceptive feedback from muscles and tendons around the ankle. Loss of ankle proprioception results in problems with balance.

  2. Optic ataxia: Caused by damage to the parietal lobes, it is characterized by a dysfunction of reaching movements under visual guidance (see chapter on Dementias).

  3. Cerebellar ataxia: The cerebellum is involved in coordination of movement of different muscle groups. Problems with the cerebellum cause the various manifestations of cerebellar ataxia.

  4. Vestibular ataxia: Loss of balance and coordination in the setting of vestibular system dysfunction or its connections. Patients with chronic bilateral loss of vestibular function report a sense of unsteadiness, dizziness, vertigo, post-movement gaze variability, and oscillopsia.

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CASE 30-1

You are the neuro-hospitalist on call and get a page from the Urgent Care Clinic to consult on a patient with problems with gait and balance. This is the second time he presented to Urgent Care with similar complaints over the past weeks. During the last visit, the physician had suspected cervical spine stenosis and obtained an MRI of the brain and cervical spine. He had also referred the patient to ENT for assessment of vestibular function who had thought that a vestibular disorder did not explain the symptoms fully. The clinic attending says she thinks the patient has ataxia.

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WHAT IS THE ROLE OF HISTORY AND EXAMINATION IN THE DIAGNOSIS OF CEREBELLAR ATAXIA?

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From the history, we may elicit the common symptoms of cerebellar ataxia. The key features in disorders presenting with cerebellar ataxia are the presence of poor balance with falls, imprecise hand coordination, postural or kinetic tremors of the extremities or trunk, dysarthria, dysphagia, vertigo, and diplopia.

  1. Lack of balance. Patients complain of not being able to walk in a straight line and bumping into walls. The patient often walks in a zigzag and reports that it feels like ambulating on a boat. The companions may note the patient walks like a drunk person.

  2. Incoordination. The patient may complain of clumsiness and problems with skilled tasks. They may drop objects or have problem with reaching for items.

  3. Tremor. Two kinds of tremors are seen in patients with cerebellar ataxia. They complain of hand shaking when reaching for things or trying to do something. Some complain of head shaking especially while sitting. Cerebellar tremors are worse at the end of the movement with variable amplitude and low frequency around 3–5 Hz.

  4. Dysarthria: Dysarthria is a problem with articulation of speech. There are several kinds of dysarthrias:

    1. Bulbar dysarthria...

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