Broca Aphasia

Etiology

The most common cause of Broca aphasia is a stroke involving the dominant inferior frontal lobe or Broca area. A stroke in the Broca area is usually due to a thrombus or emboli in the middle cerebral artery or internal carotid artery. Other causes of Broca aphasia include traumatic brain injury, tumors, and brain infections. Aphasia is a symptom of degenerative dementing illnesses such as Alzheimer disease. With dementing illness, patients develop gradual progressive language deficits as opposed to a sudden onset of loss of language function that is seen in an ischemic stroke.[4]

Epidemiology

Data on the incidence of Broca aphasia are limited. In the United States, approximately 170,000 new cases of aphasia related to stroke occur annually.[5]

Pathophysiology

Broca area is a region in the inferior frontal lobe of the brain's dominant hemisphere, made up of Brodmann areas 44 and 45. Language function lateralized to the left hemisphere in 96% to 99% of right-handed people and 60% of left-handed people. Various pathways connect the Broca area to the frontal lobe, basal ganglia, cerebellum, and contralateral hemisphere. As a result of a lesion in the Broca area, there is a breakdown between one's thoughts and one's language abilities. Thus, patients often feel that they know what they wish to say but cannot produce the words. They cannot translate their mental images and representations into words. This affects the normal fluency of speech. The loss of language function may be because the Broca area serves a role in ordering sounds into words and words into sentences, thus creating relationships between linguistic elements.

History and Physical

Broca aphasia is non-fluent aphasia. The output of spontaneous speech is markedly diminished. There is a loss of normal grammatical structure (agrammatic speech). Specifically, small linking words, conjunctions (and, or, but), and the use of prepositions are lost. For example, a sentence like "I took the dog for a walk." may become "I walk the dog." Patients can exhibit interjectional speech with a long latency, and the words expressed are produced as if under pressure. The ability to repeat phrases is also impaired. Despite these impairments, the produced words are often intelligible and contextually correct. In pure Broca aphasia, comprehension is intact. Patients with Broca aphasia are often very upset about their difficulty communicating. This may be due to the deficit or damage to adjacent frontal lobe structures, which control the inhibition of negative emotions. Broca aphasia can accompany other neurological deficits such as right facial weakness, hemiparesis or hemiplegia, and apraxia.

Evaluation

Bedside examination of a patient with suspected aphasia includes fluency assessments, the ability to name objects, repeat short phrases, follow simple and complex commands, and read and write. Formal neuropsychological testing may help determine the type and severity of the language deficit. Neuroimaging may be required to localize and diagnose the cause of aphasia. Patients should also be screened for depression, as this is also common in Broca aphasia.[6]

Treatment / Management

Broca aphasia often has a devastating effect on the ability of individuals to carry out their normal activities. It affects the patient's communication ability, often leading to loss of productivity, vocation, and social isolation.[7][8][9] Currently, there is no standard treatment for Broca aphasia. Treatments should be tailored to each patient's needs. Speech and language therapy is the mainstay of care for patients with aphasia. It is essential to provide aphasic patients with a means to communicate their wants and needs so these may be addressed. Often, this is done by providing a board with various objects so the patient can point to the object they want. The involvement of a speech therapist, neuropsychologist, and neurologist in developing a care plan for the patient with Broca aphasia is very helpful in obtaining a good outcome. One innovative treatment option for patients with Broca aphasia is melodic intonation. Melodic intonation relies on the fact that musical ability is often spared in Broca aphasia. Thus, the speech therapist encourages patients with poor speech production to express their words with musical tones. This approach has shown promise in clinical trials.

Medical treatment of aphasia is currently under investigation in clinical trials. Drug therapies have included catecholaminergic agents (bromocriptine, levodopa, amantadine, dexamphetamine), piracetam and related compounds, acetylcholine esterase inhibitors, and neurotrophic factors. Previous studies have been small, and further studies are needed to determine the efficacy of these pharmacological agents. Also, transcranial magnetic stimulation and transcranial direct stimulation trials for aphasia are currently underway. When the cause of Broca aphasia is a stroke, recovery of language function peaks within 2 to 6 months, after which time further progress is limited. However, patients should be encouraged to work on speech production because cases of improvement have been seen long after a stroke. There are commercial software products available that claim to improve language function, but for the most part, these have not been rigorously tested in randomized clinical trials. It is important to address issues of post-stroke depression and post-stroke cognitive impairment, as well as disorders of executive function, awareness, neglect, and hemiparesis during the rehabilitation process to optimize the outcome for an individual patient. Family and social support are extremely important to keep patients with language deficits engaged in social and leisure activities, which can greatly influence the aphasic patient’s quality of life.

Differential Diagnosis

Differential diagnosis for Broca aphasia includes:

• Anterior circulation stroke
• Cardioembolic stroke
• Central pontine myelinolysis
• Cerebral venous thrombosis
• Dementia in motor neuron disease
• Dissection syndrome
• Frontal lobe syndrome
• Glioblastoma multiforme
• Head injury