Topics and Speakers Randolph S. Marshall, MD, MS
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Synopsis
Stroke causes substantial injury to the brain often resulting in profound dysfunction of the higher cortical functions. In this lecture, Dr Randolph S. Marshall focuses on two of the common impairments that follow stroke: dyspraxia and hemineglect. Throughout the lecture, he illustrates his discussion of these two conditions with videos of cases.
Dyspraxia is an impairment in the execution of a motor act in the absence of primary weakness, sensory loss, or incoordination. When evaluated, patients with dyspraxia do not demonstrate any hemiparesis, sensory loss, or motor incoordination. Yet they are unable to execute motor acts, whether simple or complex. Dr Marshall distinguishes between several types of dyspraxia and apraxia. Ideomotor apraxia (or dyspraxia) is the inability to integrate basic sensory motor elements to achieve a simple motor goal, such as using scissors. Ideational apraxia is the inability to combine simple motor elements to achieve a complex or sequential motor act. For example, patients may have difficulty with complex acts, like dressing, which require executing tasks in a particular order. Constructional apraxia involves the inability to produce a mental image of an object in order to reproduce it on paper.
Often dyspraxia is associated with aphasia, which complicates evaluation and diagnosis. If a physician asks a patient to pantomime scissors, they may fail either because they do not comprehend the request (sensory aphasia) or lack the ability to execute the task (dyspraxia). This problem can be mitigated by having patients simply imitate a gesture that does not require the comprehension of language.
Disconnection syndrome occurs with a lesion to the corpus callosum. Patients with this syndrome have trouble attempting to pantomime a simple act but may be able to use the object itself. For example, a patient may not be able to show how he would put on his glasses. When the glasses are placed in his hand, however, he puts them on with ease. This intriguing syndrome results because the lesion in the corpus callosum prevents instructions from crossing from one brain hemisphere to another. Because the intrahemispheric connections are still intact, simply executing the movement is still possible.
Hemineglect is an inattention to one side of space. It is usually seen in the acute phases of stroke but can also result from tumor or head trauma. It predominantly involves dysfunction of the right hemisphere with consequent inability to attend leftward. Anosognosia is the unawareness of a deficit and is very common in patients with hemineglect. A submanifestation of this unawareness is asomatognosia, a striking syndrome in which patients do not recognize the left side of their body as their own. When presented with their own hand, patients will deny that it belongs to them. Dr Marshall describes functional imaging of hemineglect as well as the standard tests used to quantify and characterize the hemineglect.
