Apraxia of speech is an acquired disorder that causes difficulty in speaking, as a result of a defect in the transmission of commands from the brain to the muscles of the mouth. Developmental verbal dyskinesia is also known as childhood apraxia of speech. It is the inability of a child to perform the verbal movements necessary for speaking during the learning period. Although the causes of apraxia of speech and developmental verbal dyskinesia differ, they have similar characteristics and treatment. Especially when it comes to sequencing and producing sounds. The Lefelt model describes the process of speaking through three stages: conception, formulation, and articulation. According to the Lefelt model, apraxia of speech affects the articulation stage. The affected person does not actually have difficulty with language, but rather the difficulty lies in producing language in an understandable sound form. Interestingly, this difficulty is limited to vocal speech only, but body language is not affected, which confirms that the defect is in the part of the brain responsible for sending signals to the muscles of the mouth to perform a specific movement. The most obvious symptoms of this disease are the presence of errors in articulation and phonation. Some of the accompanying symptoms include effort in speaking, self-correction of errors, difficulty initiating speech, abnormal tension, and instability in pronunciation. Wirtz described five symptoms that appear in an individual with apraxia of speech. Stuttering is the process of finding the right mouth position to produce the desired sound. When the patient tries to pronounce a word, it takes longer or he pronounces it repeatedly or in a low voice. In some cases, the patient can pronounce the word easily and spontaneously, but when asked to pronounce a specific word, he makes an effort and struggles to pronounce the word. The patient is aware of his pronunciation errors and tries to correct them for himself. This is because he is able to understand speech more than he expresses it. When pronouncing the same word repeatedly with different examples, the person with apraxia of speech has some difficulty in using and maintaining the same pronunciation similar to the previous pronunciation. The person with apraxia of speech may make some mistakes on some days or may seem as if he is losing the ability to pronounce certain sounds at some times. Articulation also becomes more difficult when a word or phrase requires some organization in the way it is articulated, such that the tongue and lip movements must be in a specific order to move between sounds. For example, the word "baby" requires less organization of the mouth than the word "dog"; if "dog" is said, it requires both tongue and lip movements to articulate. Speech production becomes more difficult for people with apraxia of speech, resulting in more speech errors. Errors in completing speech gestures are likely to increase as the length of the utterance increases. Since multi-syllable words are difficult, people with apraxia of speech use simple words with a limited range of vowels and consonants. Speech-language pathologists diagnose apraxia of speech through specific tests that measure the oral mechanics of speech. The oral mechanics test includes tasks such as pursing lips, blowing, licking the lips, and lifting the tongue, and also includes an examination of the mouth. A complete examination also includes observing the patient while he or she is eating and speaking. Speech-language pathologists do not agree on a specific set of characteristics that constitute a diagnosis of apraxia of speech, so any of the characteristics from the above section can be used for diagnosis. Patients may be required to perform other daily tasks such as reading, writing, and speaking with others. In cases involving brain damage, brain MRIs can also help identify damaged areas of the brain. Differential diagnosis must be used to rule out other similar or alternative disorders. Although other disorders such as expressive apraxia, conductive apraxia, and dysarthria involve symptoms similar to apraxia of speech, the disorders must be distinguished in order to treat patients properly—while apraxia of speech involves motor organization or the processing stage of speech, aphasia disorders may involve other linguistic processes. According to Ziegler et al., this difficulty in diagnosis stems from the unknown causes and function of the disorder, making it difficult to establish specific criteria for defining apraxia of speech. However, he specifically states that orofacial apraxia, dysarthria, and aphasia are three distinct disorders that cause individuals to have symptoms that are often similar to those of a person with apraxia of speech, and that speech-language pathologists must properly rule out close associations before giving apraxia of speech as a diagnosis. In this way, apraxia of speech is a diagnosis of exclusion, generally defined when all other similar speech production disorders have been ruled out. Apraxia of speech and expressive aphasia are often confused as the same disorder because they often occur together in patients. Although both disorders come with symptoms such as difficulty producing sounds due to damage to the language parts of the brain, they are not the same. The main difference between these disorders is the ability to understand spoken language. Patients with apraxia are able to fully understand speech, whereas patients with aphasia are not always fully able to understand the speech of others. Conduction aphasia is another speech disorder that is similar, but not the same as apraxia of speech. Although patients with conduction aphasia have full understanding of speech, like those with apraxia of speech, there are differences between the two disorders. Patients with conduction aphasia are usually able to speak fluently, but they do not have the ability to repeat what they hear. Dysarthria, in turn, is another motor speech disorder characterized by difficulty articulating sounds. Difficulty in adequate articulation does not occur in the preparation of motor movements, as occurs with apraxia of speech. Rather, dysarthria is due to inability or weakness of the muscles of the mouth, face, and respiratory system. "Apraxia of speech may be caused by dysfunction of the parts of the brain that control muscle movement and speech," but the specific area of the brain in which apraxia of speech occurs is controversial. Many patients with damage to the left subcortical structures, the insula, and Broca's area have been diagnosed with apraxia of speech. It is usually caused by vascular lesions, but apraxia of speech can also arise as a result of tumors and injuries. Stroke-associated apraxia of speech is the most common form of acquired apraxia of speech, accounting for about 60% of all cases of acquired apraxia of speech reported. It is one of several possible disorders that can result from stroke, but only about 11% of stroke cases involve this disorder. Damage to the brain's nerve connections, especially the synapses, during a stroke can lead to acquired apraxia of speech. Most stroke-related apraxia of speech is mild, but in severe cases, motor function of the tongue may be lost and must be re-learned. Because most patients with this type of apraxia of speech are at least 50 years old, few recover completely to their previous level of speech production. Other brain disorders and injuries that can lead to apraxia of speech include dementia, progressive neurological disorders, and traumatic brain injury. In cases of brief apraxia of speech, the patient may recover and regain the ability to speak as before. Cases of acquired apraxia of speech require treatment, and the type of treatment varies depending on the patient's condition. Treatment usually involves seeing a speech pathologist. In severe cases of apraxia of speech, the patient may need several therapy sessions each week, and the number of sessions may decrease as the patient's condition improves. One of the basic types of treatment is repetition; the goal of this treatment is to obtain a large amount of meaningful speech or desired use of speech. There are several methods for treating apraxia of speech. The linguistic approach is a treatment method that uses sound and sequencing rules, and focuses on mouth position when forming sounds. The movement programming approach involves training the patient in the mouth movements and transitions necessary to produce sounds. Research on the treatment of apraxia has identified four main categories: articulation movement, rhythmic rate control, reorganization, and alternative and incremental communication. One study described the use of electroplatography to treat patients with severe acquired apraxia of speech. Electroplatography is a computer-based tool for assessing and treating speech problems. This program allows the patient to see the position of the mouth when speaking so that he or she can achieve the correct position. Speech problems often reappear within two years of treatment, and this study demonstrated that electroplatography therapy allows the patient to see previous mouth position problems when speaking and thus helps him or her improve them. Studies are ongoing to explore different approaches to treating apraxia of speech. Some suggestions made by ASHA include combining objective evidence for treatment, rationale, knowledge and experience of the therapist, and the needs and goals of the patient. The term apraxia was first defined by Hugo Karl Lippmann in 1908 as “the inability to perform a complex task due to weakness of the muscles”. In 1969 Frederick Darley coined the term apraxia of speech and replaced Lippmann’s definition with “the inability to perform the structure of the tongue, lips, and larynx”. Paul Burka also defined dysarthria in 1862 and renamed it aphasia, a disorder involving difficulty in articulation despite intact language skills and muscle function.