Introduction

There is an extensive literature on gait apraxia or ‘higher-level gait disorders’ as they have recently been called (Nutt et al. 1993). The term encompasses walking difficulties that are out of proportion to those that would be expected on the basis of the bedside neurological examination and that are best explained by disorders of integration of cerebral activity. There have been few attempts to formulate unifying theories regarding these gait disorders and this is borne out by the large number of synonyms used to describe what are essentially the same or very similar gait disorders (see Table 6.1). In this chapter, we shall attempt to unravel the conceptual muddle that surrounds these gait disorders. Firstly, we shall review the historical accounts of such disorders in the literature. Secondly, we shall describe a recent, though unsatisfactory classification. Thirdly, we shall propose our own classification based on neuroanatomical and neurophysiological correlations drawn largely from the existing literature on gait initiation, especially in relation to Parkinson's disease (PD). Finally, we will suggest how a clearer understanding of the disease processes may aid in developing rational approaches to therapeutic interventions. Throughout this chapter we shall focus particularly on the higherlevel gait disorders associated with cerebral multi-infarct states (CMIS) and refer to these as vascular higher-level gait disorders (vascular HLGDs). It must however be remembered that, along with CMIS, many other disease processes can lead to these gait disorders: many of the original descriptions were of frontal lobe tumours.