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Is apraxia caused by brain damage?


Apraxia is a motor disorder that affects the ability to perform learned skilled movements, despite having the desire and physical capacity to perform them. It is caused by damage to specific areas of the brain that are involved in planning, sequencing and executing movements. Apraxia can affect various body parts and manifest in different ways depending on the location and extent of brain damage. Understanding what brain areas are impacted in apraxia and how they cause deficits in skilled motor acts can provide insight into this complex disorder.

What is apraxia?

Apraxia refers to an inability to perform learned skilled movements on command, even though the request or desire to perform the action is understood and the physical ability to perform the movement is intact. It is a motor disorder caused by damage to specific areas of the brain responsible for correctly executing learned motor plans and sequences.

Common signs of apraxia include:

– Difficulty performing familiar tasks like brushing teeth, waving goodbye, using utensils or tools despite understanding what needs to be done and having the physical ability to complete it.

– Clumsy, fragmented movements when attempting learned skilled acts.

– Better at demonstrating how to perform an action than actually executing it.

– Difficulty imitating hand or body gestures, movements or postures.

– Inappropriate or incorrect positioning of body parts or sequencing of muscle movements when attempting tasks.

– Groping or trial-and-error movements when trying to interact with objects.

There are several types of apraxia based on the location of the brain damage and resulting motor deficits:

– Ideomotor apraxia affects the ability to pantomime tool use and imitate gestures or movements.

– Ideational apraxia impairs performing a sequence of actions and movements in logical order to complete tasks.

– Orofacial or buccofacial apraxia affects the ability to carry out facial, lingual and mouth movements on command.

– Limb apraxia impairs movements of the arms and legs.

– Constructional apraxia affects the ability to draw or construct simple figures.

While the specific features vary, all forms of apraxia have in common an impairment in executing learned skilled motor acts that cannot be attributed to basic motor deficits, sensory loss or incomprehension of the task.

Neuroanatomy of apraxia

Apraxia is caused by damage or dysfunction in particular regions of the brain involved in skilled motor planning and execution:

Parietal lobe

The parietal lobe integrates sensory information needed for movement and contains several important praxis regions:

– Inferior parietal lobule – involved in spatiomotor processing, tool use knowledge and skilled hand movements. Damage causes ideomotor apraxia.

– Angular gyrus – processes learned, meaningful gestures and pantomimes. Lesions lead to ideomotor apraxia.

– Supramarginal gyrus – coordinates orofacial musculature for speech. Damage causes buccofacial apraxia.

Frontal lobe

Frontal lobe areas that contribute to praxis include:

– Premotor and supplementary motor cortices – program skilled, learned motor sequences. Damage results in ideomotor apraxia.

– Broca’s area – controls speech articulation. Lesions cause buccofacial apraxia.

– Prefrontal cortex – involved in motor planning. Damage impairs multi-step task performance.

Corpus callosum

The corpus callosum connects the left and right cerebral hemispheres and allows communication between motor planning and execution areas in each lobe. Damage impairs complex, coordinated movements between hands.

Basal ganglia

The basal ganglia and connecting pathways modulate cortical motor output. Dysfunction leads to inefficient, clumsy movements.

Causes of apraxia

Apraxia most commonly results from focal damage to praxis areas from:

Stroke

– Ischemic strokes causing infarcts in parietal, frontal and subcortical areas.

– Hemorrhagic strokes damaging motor cortices and white matter connectivity.

Neurodegenerative disorders

– Corticobasal degeneration – progressive loss of cortical and subcortical neuronal populations.

– Parkinson’s disease – breakdown of basal ganglia motor circuits.

– Alzheimer’s disease – parietal and frontal lobe atrophy.

Traumatic brain injury

Focal damage or diffuse axonal injury disrupting motor networks.

Brain tumors

Mass effect on frontal, parietal and corpus callosum regions.

Infections

Encephalitis, meningitis or abscesses affecting cortical and subcortical grey matter.

Toxic-metabolic disorders

Disruption of cerebral metabolism and cortical functioning from hepatic encephalopathy, uremic encephalopathy, drug intoxication.

Developmental disorders

Congenital or early life lesions to motor regions.

Diagnosing apraxia

A diagnosis of apraxia requires:

– Excluding elementary motor, sensory or language deficits that could mimic apraxia.

– Assessing performance on skilled motor tasks requiring semantic knowledge, motor planning and praxis.

– Testing imitation of gestures and use of tools/objects.

– Evaluation of automatic (reflexive) vs volitional movement.

– Sequencing tasks to evaluate multi-step skills.

– Neuroimaging studies to detect lesions in praxis regions.

Depending on the type of apraxia and suspected causative lesion, specific subtests can help localize the damage and deficits:

Test Assesses
Pantomime to visual cue Ideomotor apraxia
Pantomime to verbal command Ideomotor apraxia
Imitating hand/finger gestures Ideomotor apraxia
Transitive (tool use) gestures Ideomotor apraxia
Intransitive (symbolic) gestures Ideomotor apraxia
Bucofacial praxis Orofacial apraxia
Multistep object use Ideational apraxia
Picture/model construction Constructional apraxia

Apraxia treatment

Treatment focuses on retraining motor planning and execution strategies:

Compensatory strategies

– Use cues, prompts and hand-over-hand guidance.

– Simplify tasks into single step actions.

– Provide verbal, visual and tactile feedback.

– Practice everyday tasks frequently to make them more automatic.

Gesture and movement training

– Imitation and repetition of specific actions or sequences.

– Mirror feedback during practice.

– Shape hand and body appropriately for tasks.

– Use objects and props as needed.

Errorless learning

– Guide correct movements and provide feedback.

– Avoid allowing incorrect attempts.

– Taper prompts as skills improve.

Cognitive approaches

– Explicitly formulate motor plans before executing actions.

– Think through task steps verbally before performing them.

– Use mental visualization of movements.

– Practice motor imagery and pantomime of skills.

Limb activation therapy

– Stimulate the affected limb prior to praxis training.

– Use tactile stimulation, proprioceptive cues, passive movement.

– Increase use of affected limb in daily activities.

The specific approach depends on the type and severity of apraxia, as well as the individual’s abilities and capacity to improve. Consistent, repeated practice is key to successfully retraining praxis skills.

Prognosis for apraxia

The prognosis depends on the underlying cause and severity of the apraxia:

– Stroke-induced apraxia may improve spontaneously in the first few months. More severe cases will require active rehabilitation.

– Degenerative disorders cause progressive decline in praxis skills over time. Treatment can help slow worsening.

– Developmental apraxia has a better prognosis in children as their brains remain plastic. Early intervention is key.

– Mild-moderate acquired apraxia can improve significantly with targeted, intensive therapy.

– Severe apraxia is more resistant to treatment, with limited gains. Compensatory methods become more important.

– Additional cognitive or language deficits make retraining praxis skills more difficult.

While deficits may persist to some degree, treatment can often improve motor planning and execution, leading to enhanced functioning and quality of life. Supportive aids and adaptive strategies help maximize independence.

Conclusion

Apraxia is a complex disorder of skilled motor planning and execution caused by specific damage to praxis regions of the brain. Key areas include the parietal lobe, frontal lobe, corpus callosum and basal ganglia. Impaired ability to perform learned skilled gestures and movements can result from stroke, neurodegenerative disease, trauma, tumors and other neurological insults. Diagnosis involves testing praxis skills and identifying the underlying lesion. Treatment focuses on retraining motor sequencing and execution strategies, while addressing associated disabilities. With appropriate therapy, many patients can regain functional abilities, although mild to moderate deficits often remain. Targeted rehabilitation can improve outcomes and quality of life for those living with apraxia.