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Chapter Objectives

Upon completion of this chapter, the learner should be able to:

  1. Discuss the physiology of coordinated movement.

  2. Discuss the etiology, pathogenesis, and clinical presentation of ataxia/incoordination.

  3. Explain the differential diagnosis between ataxia/incoordination due to a somatosensory impairment and to a cerebellar impairment.

  4. Discuss the evaluation principles applicable to a patient who presents with ataxia/incoordination.

  5. Discuss the principles of intervention to design an appropriate rehabilitation program for patients with cerebellar and somatosensory ataxia/incoordination.

  6. Discuss precautions, monitoring, and a home program for patients with cerebellar and somatosensory ataxia/incoordination


This chapter explains the basic anatomy and physiology of lesions known to result in ataxia/incoordination, their potential etiology, the differentiation between cerebellar and sensory ataxia/incoordination, and the rehabilitation principles for these conditions.

Coordination, or coordinated functional movement, is described in the coordination examination section of Chapter 6. Coordination requires precise cooperation between opposing muscle groups, related interjoint muscle groups, and interlimb muscle groups for functional activities, along with normal postural control during a volitional movement. Normal postural control depends on an anatomically intact neuromusculoskeletal system (Fig. 21-1) and intact complex interactions and cooperation between the many systems in the human body that control its biomechanical alignment and orientation within the context of environmental demands.


Schematic representation of the circuitry involved in motor function. (Reproduced with permission from Michael-Titus A, Revest P, Shortland P. The Nervous System: Basic Science and Clinical Conditions. Philadelphia, PA: Churchill Livingstone; 2007.])

Ataxia/incoordination occurs as a result of either the lack/absence of sensory (in particular, proprioceptive) input from the periphery to the cerebellum, or higher sensory centers (sensory ataxia), or a lesion/disruption in the interaction among four different systems: the lower motor neurons (LMNs) in the brainstem and spinal cord, the upper motor neuron (UMN) cell bodies in the cortex and brainstem, the cerebellum, and the basal ganglia.

Normal Motor Function

Normal coordinated, selective, voluntary and involuntary, intentional and automatic, conscious and subconscious movements are essential in a large variety of specific movement patterns (including movements of the mouth and eyes) during skilled activities of daily living (ADLs), recreational activities, and sporting activities. As mentioned previously, movement is controlled and coordinated through the interaction between four subsystems of the nervous system: the LMNs in the brainstem and spinal cord, the UMN cell bodies in the cortex and the brainstem, the cerebellum, and the basal ganglia (which have an inhibitory influence on the motor cortex). Both the cerebellum and the basal ganglia regulate the activity of the LMN via the UMN and the thalamus.

A simplistic but holistic understanding of the organization of the brain makes it easier to understand the sources from which ataxia or incoordination can originate and how the rehabilitation ...

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