Neuroscience Clerkship

 

 

Aphasia and Dysarthria

The terms Aphasia and Dysarthria are often confused, and used as if they were interchangeable. However, this is not the case; they have very different meanings:

 

Aphasia is a disturbance of language

Dysarthria is a disturbance in articulation
 

Aphasia results from a focal insult to the brain, usually to one of the areas around the Sylvian fissure of the dominant hemisphere. Aphasia may result in impaired of expression, comprehension, repetition, naming, reading and/or writing. There are several important types of aphasia to recognize. Among them are Broca’s, Wernicke’s, Conduction and Global aphasias.
Dysarthria, on the other hand, is simply a collective name for a group of speech disorders resulting from disturbances of muscular control of speech production. In dysarthric patients, the actual language (grammar, word choice, understanding) is normal. Dysarthria may result from many etiologies, both locally and in the central and peripheral nervous systems. For instance, dysarthria can be seen in:


Local disorders

(e.g., disorders of the tongue, palate and larynx)

Myopathies

(e.g., oculopharyngeal muscular dystrophy, FSH muscular dystrophy)

NMJ Disorders

(e.g., myasthenia gravis)

Disorders of Cranial Nerves 5, 7, 9, 10, or 12

(e.g., skull based tumors)

Diffuse Peripheral Neuropathies

(e.g., Guillain-Barré Syndrome)

Brainstem disorders

(e.g., stroke, tumor)

Cerebellar disorders

(e.g., scanning speech in paraneoplastic degeneration, multiple sclerosis, etc.)

Basal ganglionic disorders

(e.g., hypophonic speech in Parkinson’s)

Subcortical disorders

(e.g., slurred speech in lacunar strokes)

Cortical disorders

(e.g., slurred speech in a MCA stroke)

Mixed Upper and Lower Motor Neuron Disorders

(e.g., mixed flaccid and spastic speech in ALS)

 

Although dysarthria often implicates a neurologic disorder, dysarthria is often not localizing in isolation. Aphasia, on the other hand, always implicates a central nervous system disorder, usually cortical, affecting the dominant hemisphere in the peri-sylvian area. Patients can have both dysarthria and aphasia (e.g., stroke in the left frontal lobe).