A Model-Based Approach to Understanding Apraxia in Corticobasal Syndrome

Abstract

Limb apraxia is a neurological disorder of higher cognitive function characterized by an inability to perform purposeful skilled movements and not attributable to an elementary sensorimotor dysfunction or comprehension difficulty. Corticobasal Syndrome (CBS) is an akinetic rigid syndrome with asymmetric onset and progression with at least one basal ganglia feature (rigidity, limb dystonia or myoclonus) and one cortical feature (limb apraxia, alien hand syndrome or cortical sensory loss). Even though limb apraxia is highly prevalent in CBS (70-80%), very few studies have examined the performance of CBS patients on praxis measures in detail. This review aims to (1) briefly summarize the clinical, neuroanatomical and pathological findings in CBS, (2) briefly outline what limb apraxia is and how it is assessed, (3) to comprehensively review the literature on limb apraxia in CBS to date and (4) to briefly summarize the literature on other forms of apraxia, such as limb-kinetic apraxia and buccofacial apraxia. Overall, the goal of the review is to bring a model-based perspective to the findings available in the literature to date on limb apraxia in CBS.

Correlation between Assessments of Arm and Leg Ideomotor Apraxia in Hemiplegic Stroke Patients

“…The pathophysiologic mechanism of IMA is considered to be damage of the praxis system, which is involved in the representation of gestures in the brain, the characteristic movements of tools, and a brain model of the body and its position in space. The accurate neural processes of the praxis system are related to the movement strategy and are finally transmitted to the primary motor cortex for movement generation [22][23][24] . The primary motor cortex plays an important role in executing the precise movements of the upper and lower limbs according to the movement strategy of the praxis system 7, 11,12,15) .…”

The clinical assessment of apraxia

“…Another likely reason for its relatively low profile is that any lesion affecting the prefrontal motor cortex also likely disrupts the integrity of the corticospinal tract, so muscle weakness often overshadows any higher level disorder of motor control. The term is therefore not widely used, but there has been renewed interest in this area with the realisation that many patients with corticobasal syndrome have limb-kinetic apraxic deficits 8. It often manifests early in the disease course and the neurologist should suspect it if a patient struggles to produce any form of rhythmical opposition of their index finger and thumb when testing for bradykinesia.…”

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

“…Corticobasal syndrome can also arise from other neuropathologies, such as Alzheimertype pathology or progressive supranuclear palsy [13][14][15], Creutzfeldt-Jakob disease [14] or the cumulative effects of cerebrovascular disease [16]. The corticobasal syndrome can present with subcortical motor features (including akinetic rigidity, dystonia and myoclonus) or cortical features (including visuospatial and deficits, non-fluency and cortical sensory loss) [17,18]. The current international consensus clinical diagnostic criteria for corticobasal syndrome include alien limb [19], as have earlier diagnostic criteria [20,21].…”

“…Apraxia may be defined as a disorder of "the execution of learned movement which cannot be accounted for either by weakness, incoordination or sensory loss, or by incomprehension of or inattention to commands" [23]. It is assessed through the pantomiming of actions (performing an action on request without example) and imitation of gestures [18]. It can result from focal lesions, classically in the corpus callosum and dominant hemisphere [23,24], as well as neurodegenerative disorders such as corticobasal syndrome [18,19].…”

“…It is assessed through the pantomiming of actions (performing an action on request without example) and imitation of gestures [18]. It can result from focal lesions, classically in the corpus callosum and dominant hemisphere [23,24], as well as neurodegenerative disorders such as corticobasal syndrome [18,19]. Limb apraxia is usually considered in three forms, often called 'ideational', 'ideomotor', and 'limb-kinetic apraxia' [18,25].…”