Alien limb in the corticobasal syndrome: phenomenological characteristics and relationship to apraxia

David J. Lewis-Smith,James B. Rowe,Noham Wolpe,Boyd C. P. Ghosh

doi:10.1007/s00415-019-09672-8

Abstract

Alien limb refers to movements that seem purposeful but are independent of patients’ reported intentions. Alien limb often co-occurs with apraxia in the corticobasal syndrome, and anatomical and phenomenological comparisons have led to the suggestion that alien limb and apraxia may be causally related as failures of goal-directed movements. Here, we characterised the nature of alien limb symptoms in patients with the corticobasal syndrome (n = 30) and their relationship to limb apraxia. Twenty-five patients with progressive supranuclear palsy Richardson syndrome served as a disease control group. Structured examinations of praxis, motor function, cognition and alien limb were undertaken in patients attending a regional specialist clinic. Twenty-eight patients with corticobasal syndrome (93%) demonstrated significant apraxia and this was often asymmetrical, with the left hand preferentially affected in 23/30 (77%) patients. Moreover, 25/30 (83%) patients reported one or more symptoms consistent with alien limb. The range of these phenomena was broad, including changes in the sense of ownership and control as well as unwanted movements. Regression analyses showed no significant association between the severity of limb apraxia and either the occurrence of an alien limb or the number of alien limb phenomena reported. Bayesian estimation showed a low probability for a positive association between alien limb and apraxia, suggesting that alien limb phenomena are not likely to be related to severity apraxia. Our results shed light on the phenomenology of these disabling and as yet untreatable clinical features, with relevance to theoretical models of voluntary action.

Highlights

Alien limb phenomena are a heterogeneous group of behaviours in which one or more of a patient’s limbs, usually an arm, behaves in a manner that appears purposeful or semipurposeful but is independent of the patient’s reported intentions [1,2,3,4,5]
In terms of age and gender, our progressive supranuclear palsy syndrome (PSP) and corticobasal syndrome patients were similar to those reported in a larger population-representative epidemiological study [40]
Limb praxis scores were incomplete for one patient with corticobasal syndrome and another with PSP

Summary

Introduction

Alien limb phenomena are a heterogeneous group of behaviours in which one or more of a patient’s limbs, usually an arm, behaves in a manner that appears purposeful or semipurposeful but is independent of the patient’s reported intentions [1,2,3,4,5]. The first group includes complex, unwilled motor acts, including intermanual conflict, mirror movements, interference, and the pushing aside of the directed limb by the autonomous limb. These movements have been described as often bimanual, and liable to occur within two scenarios: (a) the offending hand is involuntarily recruited to tasks which the patient intends to perform unimanually with the other hand and (b) the offending limb undertakes the incorrect act when desired to act in concert with the. The second group of phenomena include simple, unwilled, quasi-reflex actions These include autonomous reaching, grasping and utilisation behaviour, automatic limb withdrawal or levitation

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Results

Discussion

Conclusion