Ataxia
Ataxia is a disorder of coordination and rhythm. With ataxia, the rate, range, and force of movement are altered. Classically, physicians are taught that ataxia is equivalent to a cerebellar disorder. Indeed, this may be so. However since the advent of more advanced imaging, it has become clear that many people with ataxia actually have disorders in other parts of the systems that underlie movement.
Intention tremor that with voluntary movement of a limb towards a target, sees side-to-side oscillation, which increases as the limb closes in on the target.
Unsteady gait, often with a wide base.
Dysdiadochokinesis, where when alternately supinating and pronating the hand, there are slow, jerky, arrhythmic movements.
Overshoot dysmetria, where the patient often launches a limb to the target, overshoots, and then recorrects. This is the basis of intention tremor.
Scanning speech, in which ataxia is sometimes associated with a hesitant, arrhythmic speech that varies in rate and force.
IS THE LESION IN THE FRONTAL LOBE?
Mechanism: involvement of corticocerebellar connections (i.e., frontopontocerebellar pathway).
Tumor. Meningioma, glioma, or metastatic tumor may involve the frontal lobes. Patients may have signs suggesting cerebellar disease (i.e., staggering gait, difficulty performing rapid alternating movements, and even nystagmus). Patients with “frontal ataxia” tend to fall backward. Other features of frontal lobe dysfunction include perseveration, grasp and primitive suck reflexes, incontinence, slowness in thinking and initiating conversation, and headache.
Anterior cerebral artery syndrome. A thrombotic occlusion of this artery affects the frontal lobes (see Chapter 16). A large aneurysm of the anterior communicating artery also may affect the frontal lobes.
Hydrocephalus. Enlargement of the frontal horns of the lateral ventricles affects leg fibers, and may produce ataxia. In addition, there are often memory loss and incontinence. Hydrocephalus may occur with tumors that obstruct the ventricular system, or with disorders of cerebrospinal fluid (CSF) absorption (see Chapter 31).
IS THE LESION SUBCORTICAL?
Multiple strokes (état lacunaire). In addition to ataxia, there is emotional lability, brisk reflexes including increased jaw jerk, dysarthria, and dementia (see Chapter 19).
Ataxic hemiparesis (ataxia crural paresis). This is a lacunar syndrome, with the lesion in the internal capsule or contralateral basis pontis. There is ataxia on the same side as the hemiparesis, with weakness primarily in the leg.Related posts:
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