Akinetic mutism can also occur as a result of damage to the mesencephalic region of the brain. Mesencephalic akinetic mutism is clinically categorized as somnolent or apathetic akinetic mutism. It is characterized by vertical gaze palsy and ophthalmoplegia. This state of akinetic mutism varies in intensity, but it is distinguished by drowsiness, lack of motivation, hyper-somnolence, and reduction in spontaneous verbal and motor actions.

Symptoms of akinetic mutism progress over time. The occurrence of akinetic mutism takes place approximately four months after the symptoms first appear.

- Lack of motor function (but not paralysis)

- Lack of speech

- Apathy

- Slowness

- Disinhibition

The bilateral form of FCMS ("also known as facio-labio-pharyngo-glosso-laryngo-brachial paralysis)" is consistent with the classic presentation of bilateral corticobulbar involvement. It is characterized by well-preserved automatic and reflex movements. It is caused by lesions in the cortical or subcortical region of the anterior opercular area surrounding the insula forming the gyri of the frontal, temporal, and parietal lobes.

The unilateral operculum syndrome is a very rare form of FCMS caused by the formation of unilateral lesions. In this form of FCMS, the unaffected hemisphere of the brain compensates for the unilateral lesion. Usually, this occurs when the unaffected region is the individual's dominant hemisphere.

Frontal lobe disorder is an impairment of the frontal lobe that occurs due to disease or head trauma. The frontal lobe of the brain plays a key role in higher mental functions such as motivation, planning, social behaviour, and speech production. A frontal lobe syndrome can be caused by a range of conditions including head trauma, tumours, degenerative diseases, neurosurgery and cerebrovascular disease. Frontal lobe impairment can be detected by recognition of typical clinical signs, use of simple screening tests, and specialist neurological testing.

The signs and symptoms of frontal lobe disorder can be indicated by Dysexecutive syndrome which consists of a number of symptoms which tend to occur together. Broadly speaking, these symptoms fall into three main categories; cognitive (movement and speech), emotional or behavioural. Although many of these symptoms regularly co-occur, it is common to encounter patients who have several, but not all of these symptoms. This is one reason why some researchers are beginning to argue that dysexecutive syndrome is not the best term to describe these various symptoms. The fact that many of the dysexecutive syndrome symptoms can occur alone has led some researchers to suggest that the symptoms should not be labelled as a "syndrome" as such. Some of the latest imaging research on frontal cortex areas suggests that executive functions may be more discrete than was previously thought.

Signs/symptoms can be divided as follows:

Primary stuttering behaviors are the overt, observable signs of speech disfluencies, including repeating sounds, syllables, words or phrases, silent blocks and prolongation of sounds. These differ from the normal dysfluencies found in all speakers in that stuttering dysfluencies may last longer, occur more frequently, and are produced with more effort and strain. Stuttering dysfluencies also vary in quality: common dysfluencies tend to be repeated movements, fixed postures, or superfluous behaviors. Each of these three categories is composed of subgroups of stutters and dysfluencies.

- Repeated movements

- Part-word repetition—a single segment of a word is repeated (for example: "s-s-stuttering!") or a part of a word which is still a full syllable such as "un—un—under the..." and "o—o—open".

- Incomplete syllable repetition—an incomplete syllable is repeated, such as a consonant without a vowel, for example, "c—c—c—cold".

- Whole-word repetition—a whole word, or more than one word is repeated, such as "I know—I know—I know a lot of information.".

- Fixed postures

- Prolongation—prolongation of a sound occurs such as "mmmmmmmmmom".

- Block—such as a block of speech or a tense pause where nothing is said despite efforts.

- Superfluous behaviors

- Interjections—this includes an interjection such as an unnecessary "uh" or "um" as well as revisions, such as going back and correcting one's initial statements such as "I—My girlfriend...", where the "I" has been corrected to the word "my".

- Secondary characteristics—these are visible or audible speech behaviors, such as lip smacking, throat clearing, head thrusting, etc., usually representing an effort to break through or circumvent a block or stuttering loop.

Selective mutism previously known as "elective mutism" is an anxiety disorder very common among young children, characterized by the inability to speak in certain situations. It should not to be confused with someone who is mute and cannot communicate due to physical disabilities. Selectively mute children are able to communicate in situations in which they feel comfortable. About 90% of children with this disorder have also been diagnosed with social anxiety. It is very common for symptoms to occur before the age of five and do not have a set time period. Not all children express the same symptoms. Some may stand motionless and freeze in specific social settings and have no communication.

Alalia is a disorder that refers to a delay in the development of speaking abilities in children. In severe cases, some children never learn how to speak. It is caused by illness of the child or the parents, the general disorders of the muscles, the shyness of the child or that the parents are close relatives.

Anarthria is a severe form of dysarthria. The coordination of movements of the mouth and tongue or the conscious coordination of the lungs are damaged.

Aphasia can rob all aspects of the speech and language. It is a damage of the cerebral centres of the language.

Aphonia is the inability to produce any voice. In severe cases the patient loses phonation. It is caused by the injury, paralysis, and illness of the larynx.

Conversion disorder can cause loss of speaking ability.

Feral children grow up outside of human society, and so usually struggle in learning any language.

Some people with autism never learn to speak.

Most intellectually disabled children learn to speak, but in the severe cases they can't learn speech (IQ 20-25). Children with Williams syndrome have good language skills with mean IQ 50. Children with Down syndrome often have impaired language and speech.

Those who are physically mute may have problems with the parts of the human body required for human speech (the esophagus, vocal cords, lungs, mouth, or tongue, etc.).

Trauma or injury to Broca's area, located in the left inferior frontal cortex of the brain, can cause muteness.

Stuttering, also known as stammering, is a speech disorder in which the flow of speech is disrupted by involuntary repetitions and prolongations of sounds, syllables, words or phrases as well as involuntary silent pauses or blocks in which the person who stutters is unable to produce sounds. The term "stuttering" is most commonly associated with involuntary sound repetition, but it also encompasses the abnormal hesitation or pausing before speech, referred to by people who stutter as "blocks", and the prolongation of certain sounds, usually vowels or semivowels. According to Watkins et al., stuttering is a disorder of "selection, initiation, and execution of motor sequences necessary for fluent speech production." For many people who stutter, repetition is the primary problem. The term "stuttering" covers a wide range of severity, encompassing barely perceptible impediments that are largely cosmetic to severe symptoms that effectively prevent oral communication. In the world, approximately four times as many men as women stutter, encompassing 70 million people worldwide, or about 1% of the world's population.

The impact of stuttering on a person's functioning and emotional state can be severe. This may include fears of having to enunciate specific vowels or consonants, fears of being caught stuttering in social situations, self-imposed isolation, anxiety, stress, shame, being a possible target of bullying (especially in children), having to use word substitution and rearrange words in a sentence to hide stuttering, or a feeling of "loss of control" during speech. Stuttering is sometimes popularly seen as a symptom of anxiety, but there is actually no direct correlation in that direction (though as mentioned the inverse can be true, as social anxiety may actually develop in individuals as a result of their stuttering).

Stuttering is generally not a problem with the physical production of speech sounds or putting thoughts into words. Acute nervousness and stress do not cause stuttering, but they can trigger stuttering in people who have the speech disorder, and living with a stigmatized disability can result in anxiety and high allostatic stress load (chronic nervousness and stress) that reduce the amount of acute stress necessary to trigger stuttering in any given person who stutters, exacerbating the problem in the manner of a positive feedback system; the name 'stuttered speech syndrome' has been proposed for this condition. Neither acute nor chronic stress, however, itself creates any predisposition to stuttering.

The disorder is also "variable", which means that in certain situations, such as talking on the telephone or in a large group, the stuttering might be more severe or less, depending on whether or not the stutterer is self-conscious about their stuttering. Stutterers often find that their stuttering fluctuates and that they have "good" days, "bad" days and "stutter-free" days. The times in which their stuttering fluctuates can be random. Although the exact etiology, or cause, of stuttering is unknown, both genetics and neurophysiology are thought to contribute. There are many treatments and speech therapy techniques available that may help decrease speech disfluency in some people who stutter to the point where an untrained ear cannot identify a problem; however, there is essentially no cure for the disorder at present. The severity of the person's stuttering would correspond to the amount of speech therapy needed to decrease disfluency. For severe stuttering, long-term therapy and hard work is required to decrease disfluency.

Besides lack of speech, other common behaviors and characteristics displayed by selectively mute people, according to Dr. Elisa Shipon-Blum's findings, include:

- Shyness, social anxiety, fear of social embarrassment, and/or social isolation and withdrawal

- Difficulty maintaining eye contact

- Blank expression and reluctance to smile

- Difficulty expressing feelings, even to family members

- Tendency to worry more than most people of the same age

- Sensitivity to noise and crowds

On the positive side, many people with this condition have:

- Above-average intelligence, perception, or inquisitiveness

- Creativity and a love for art or music

- Empathy and sensitivity to others' thoughts and feelings

- A strong sense of right and wrong

Aboulia has been known to clinicians since 1838. However, in the time since its inception, the definition of aboulia has been subjected to many different forms, some contradictory. Aboulia has been described as a loss of drive, expression, loss of behavior and speech output, slowing and prolonged speech latency, and reduction of spontaneous thought content and initiative. The clinical features most commonly associated with aboulia are:

- Difficulty in initiating and sustaining purposeful movements

- Lack of spontaneous movement

- Reduced spontaneous speech

- Increased response-time to queries

- Passivity

- Reduced emotional responsiveness and spontaneity

- Reduced social interactions

- Reduced interest in usual pastimes

Especially in patients with progressive dementia, it may affect feeding. Patients may continue to chew or hold food in their mouths for hours without swallowing it. The behavior may be most evident after these patients have eaten part of their meals and no longer have strong appetites.

Children and adults with selective mutism are fully capable of speech and understanding language but fail to speak in certain situations, though speech is expected of them. The behaviour may be perceived as shyness or rudeness by others. A child with selective mutism may be completely silent at school for years but speak quite freely or even excessively at home. There is a hierarchical variation among people with this disorder: some people participate fully in activities and appear social but do not speak, others will speak only to peers but not to adults, others will speak to adults when asked questions requiring short answers but never to peers, and still others speak to no one and participate in few, if any, activities presented to them. In a severe form known as "progressive mutism", the disorder progresses until the person with this condition no longer speaks to anyone in any situation, even close family members.

Selective mutism is by definition characterized by the following:

- Consistent failure to speak in specific social situations (in which there is an expectation for speaking, e.g., at school) despite speaking in other situations.

- The disturbance interferes with educational or occupational achievement or with social communication.

- The duration of the disturbance is at least 1 month (not limited to the first month of school).

- The failure to speak is not due to a lack of knowledge of, or comfort with, the spoken language required in the social situation.

- The disturbance is not better accounted for by a communication disorder (e.g., childhood-onset fluency disorder) and does not occur exclusively during the course of autism spectrum disorder, schizophrenia, or another psychotic disorder.

Selective mutism is strongly associated with other anxiety disorders, particularly social anxiety disorder. In fact, the majority of children diagnosed with selective mutism also have social anxiety disorder (100% of participants in two studies and 97% in another). Some researchers therefore speculate that selective mutism may be an avoidance strategy used by a subgroup of children with social anxiety disorder to reduce their distress in social situations.

Particularly in young children, SM can sometimes be confused with an autism spectrum disorder, especially if the child acts particularly withdrawn around his or her diagnostician, which can lead to incorrect treatment. Although autistic people may also be selectively mute, they often display other behaviors—hand flapping, repetitive behaviors, social isolation even among family members (not always answering to name, for example)—that set them apart from a child with selective mutism. Some autistic people may be selectively mute due to anxiety in social situations that they do not fully understand. If mutism is entirely due to autism spectrum disorder, it cannot be diagnosed as selective mutism as stated in the last item on the list above.

The former name "elective mutism" indicates a widespread misconception among psychologists that selective mute people choose to be silent in certain situations, while the truth is that they often wish to speak but have difficulty doing so. To reflect the involuntary nature of this disorder, the name was changed to "selective mutism" in 1994.

The incidence of selective mutism is not certain. Due to the poor understanding of this condition by the general public, many cases are likely undiagnosed. Based on the number of reported cases, the figure is commonly estimated to be 1 in 1000, 0.1%. However, a 2002 study in "The Journal of the American Academy of Child and Adolescent Psychiatry" estimated the incidence to be 0.71%.

Speech and language impairment are basic categories that might be drawn in issues of communication involve hearing, speech, language, and fluency.

A speech impairment is characterized by difficulty in articulation of words. Examples include stuttering or problems producing particular sounds. Articulation refers to the sounds, syllables, and phonology produced by the individual. Voice, however, may refer to the characteristics of the sounds produced—specifically, the pitch, quality, and intensity of the sound. Often, fluency will also be considered a category under speech, encompassing the characteristics of rhythm, rate, and emphasis of the sound produced

A language impairment is a specific impairment in understanding and sharing thoughts and ideas, i.e. a disorder that involves the processing of linguistic information. Problems that may be experienced can involve the form of language, including grammar, morphology, syntax; and the functional aspects of language, including semantics and pragmatics

An individual can have one or both types of impairment. These impairments/disorders are identified by a speech and language pathologist.

Aboulia or abulia (from , meaning "will", with the prefix -a), in neurology, refers to a lack of will or initiative and can be seen as a disorder of diminished motivation (DDM). Aboulia falls in the middle of the spectrum of diminished motivation, with apathy being less extreme and akinetic mutism being more extreme than aboulia. A patient with aboulia is unable to act or make decisions independently. It may range in severity from subtle to overwhelming. It is also known as Blocq's disease (which also refers to abasia and astasia-abasia). Aboulia was originally considered to be a disorder of the will.

The following are brief definitions of several of the more prominent speech disorders:

Even though most speech sound disorders can be successfully treated in childhood, and a few may even outgrow them on their own, errors may sometimes persist into adulthood rather than only being not age appropriate. Such persisting errors are referred to as "residual errors" and may remain for life.

In some cases phonetic and phonemic errors may coexist in the same person. In such case the primary focus is usually on the phonological component but articulation therapy may be needed as part of the process, since teaching a child how to use a sound is not practical if the child does not know how to produce it.

A minimally conscious state (MCS) is a disorder of consciousness distinct from persistent vegetative state and locked-in syndrome. Unlike persistent vegetative state, patients with MCS have partial preservation of conscious awareness. MCS is a relatively new category of disorders of consciousness. The natural history and longer term outcome of MCS have not yet been thoroughly studied. The prevalence of MCS was estimated to be 112,000 to 280,000 adult and pediatric cases.

Parkinsonian gait (or festinating gait, from Latin "festinare" [to hurry]) is the type of gait exhibited by patients suffering from Parkinson's disease (PD). This disorder is caused by a deficiency of dopamine in the basal ganglia circuit leading to motor deficits. Gait is one of the most affected motor characteristics of this disorder although symptoms of Parkinson's disease are varied.

Parkinsonian gait is characterized by small shuffling steps and a general slowness of movement (hypokinesia), or even the total loss of movement (akinesia) in the extreme cases. Patients with PD demonstrate reduced stride length and walking speed during free ambulation while double support duration and cadence rate are increased. The patient has difficulty starting, but also has difficulty stopping after starting. This is due to muscle hypertonicity.

Minimally conscious state (MCS) is defined as a condition of severely altered consciousness in which minimal but definite behavioral evidence of self or environmental awareness is demonstrated.

Patients with Parkinson's disease exhibit gait characteristics that are markedly different from normal gait. While the list of abnormal gait characteristics given below is the most discussed, it is certainly not exhaustive.

List of symptoms that has been observed in those with autistic catatonia:

- Stupor

- Mutism

- Hyperactivity

- Agitation

- Excitement

- Posing

- Negativism

- Rigidity

- Waxy flexibility

- Automatic obedience

- Combativeness (during excitement)

- Aggressivity

- Stereotypies

- Tics

- Grimacing

- Echolalia

- Echopraxia

- Perseveration

- Verbigeration

- Staring

- Withdrawal

- Immobility

- Challenging behaviour

- Tremor

- Slowness

- Amotivation

- Grasp reflex

- Mannerism

- Gaze fixation

- Choreoathetoid movements of the trunk and extremities

- Autonomic instability (during excitement)

- Cannot start actions

- Cannot stop actions (if during excitement episodes needs acute psychiatric care)

- Freezing

- Impulsivity

- Bizarre/psychotic

- Sleep problems

- Urinary or Fecal incontinence

- Odd gait

- Passivity

- Reversal of day and night

- Eyerolling

- Stiff muscles

- Catalepsy

- Physiological pillow

- Difficulty crossing lines

- Gegenhalten

- Mitgehen

- Mitmachen

- Ambitendency

- Rituals

Initial symptoms include restlessness, agitation, malaise, or a fixed stare. Then comes the more characteristically described extreme and sustained upward deviation of the eyes. In addition, the eyes may converge, deviate upward and laterally, or deviate downward. The most frequently reported associated findings are backwards and lateral flexion of the neck, widely opened mouth, tongue protrusion, and ocular pain. However it may also be associated with intensely painful jaw spasm which may result in the breaking of a tooth. A wave of exhaustion may follow an episode. The abrupt termination of the psychiatric symptoms at the conclusion of the crisis is most striking.

Other features that are noted during attacks include mutism, palilalia, eye blinking, lacrimation, pupil dilation, drooling, respiratory dyskinesia, increased blood pressure and heart rate, facial flushing, headache, vertigo, anxiety, agitation, compulsive thinking, paranoia, depression, recurrent fixed ideas, depersonalization, violence, and obscene language.

It is often not realized that in addition to the acute presentation, oculogyric crisis can develop as a recurrent syndrome, triggered by stress, and exposure to the above drugs.

MRI: medial temporal lobe signal change bilateral hippocampal lesions, with signals that were hypointense in IR sequences and hyperintense in FLAIR.