Overview – Neurodevelopment Disorders – Motor (NMD)
Neurodevelopmental motor disorders are a group of conditions that are characterized by developmental deficits in learning, control, and use of motor skills. They are manifested by clumsiness and slowness or inaccuracy of performance of motor skills that cause interference with activities of daily living.
The pathophysiology of motor neurodevelopment disorders involves complex neuronal processes involving sensorimotor integration. It also includes somatosensory, proprioceptive, visual, and vestibular functions, along with the related motor control pathways. The individual has difficulty acquiring, learning, and performing coordinated motor skills. No surprise, this can interfere with activities of daily living including social, academic, and other activities. In young infants, symptoms may include hypotonia (floppy baby) or hypertonia (rigid baby) disorders.
This type of movement disorder is diagnosed when an individual has repetitive, seemingly driven, and apparently purposeless and nonrhythmic motor-movement behaviors, such as hand flapping, body rocking, head banging, self-biting, or self-hitting. If the behaviors result in self-injury, this should be specified as part of the diagnostic description. It also may include sudden, rapid, recurrent vocalizations.
Stereotypic movement disorder has been more clearly differentiated from body-focused repetitive behavior disorders that are presented in the obsessive-compulsive disorder chapter of the DSM 5.
Neurodevelopment Disorders, Motor, presents information on four types of motor disorders, one type each day for four days. These are:
Development Coordination Disorder
Developmental Coordination Disorder, also known as dyspraxia, is a fairly common neurodevelopmental motor disorder that typically is evident by age five. It is characterized by difficulty in smoothly carrying out coordinated movements, which is a complex process involving many different nerves and parts of the brain. It is a condition that affects physical coordination, causing a child to perform less well than expected in daily activities for his or her age, and appear to move clumsily. Interference with carrying out these coordinated movements appears to be implicated. A wide range of exhibited dysfunctions can be classified into three main groups: Gross Motor, Fine Motor, and Psychosocial dysfunctions based on symptoms.
The exact cause of what triggers the interference or inefficient organization of sensory information within the central nervous system has not yet been pinpointed. The gross and fine motor symptoms and disturbance of speech and language are often comorbid with attention deficit hyperactivity syndrome, autism spectrum disorder, impairment of mathematical ability and reading or writing (dyscalculia, dysgraphia, dyslexia), and abnormal muscle tone.
Stereotypic Movement Disorder (SMD)
Stereotypic Movement Disorder is a neurodevelopmental motor disorder that is characterized by a variety of repetitive and uncontrolled movements for a period of no less than four weeks. SMD manifests itself in children and adults but is most common in male children with a neurological disorder involving the brain or nerves, delays in appropriate motor development, or an intellectual disorder. Symptoms interfere with normal daily activities as well as social, academic, or other activities. If the behaviors cause self-injury, this should be specified as part of the diagnostic description.
The repetitive motions may increase with anxiety, frustration, boredom, or stress may exacerbate learning difficulties, and may be seen as antisocial behaviors. Stereotypic movement disorder has been more clearly differentiated from body-focused repetitive behaviors that are included in the DSM 5 obsessive-compulsive disorder chapter. To be diagnosed with a Stereotypic Movement Disorder, the symptoms must not be due to the direct effects of a substance, or another medical condition, or Autism Spectrum Disorder.
Tourette’s Disorder is a neurodevelopment motor disorder that involves the nervous system—one of three tic disorders identified in the DSM-5 manual. It is characterized by involuntary muscle motor-movement tics involving repetitive movements and vocal tics involving unwanted sounds. Tics are defined as fast, repetitive, muscle movements that result in sudden and difficult-to-control body jolts and sounds. Tics may happen randomly and may be associated with stress, tiredness, excitement or happiness, and anxiety including anxiety disorders. The symptoms tend to become worse if they are talked about or focused on. Tics may be preceded by premonitory urges. These can be described as strong, uncomfortable, and what appears to be an uncontrollable urge to move. Once the tic occurs, there appears to be a release of tension.
Tics tend to increase in numbers or intensity when the individual is exhausted, is experiencing anxiety, or when excited. The reverse is also true. When the individual is calm and is focused on a specific activity. Individuals may be free of tics for periods of time that range from weeks to months. Some learn to suppress their tics for a period of time. The discomfort and tension of suppressing them can be released only by allowing the tic to occur. For some after a period of suppression, the tics will occur more rapidly for a period of time as if trying to catch up to some predetermined number of tics.
- Some tics are simple motor tics that may last only milliseconds. These may include facial expressions and grimaces, eye blinking, repetitive touching of other persons or things, shoulder shrugging, head-turning, and movement of arms or legs. straightening the arms or legs. Simple vocal tics include humming, grunting, throat clearing, and sniffing.
- Some tics are complex and last for longer periods of time: seconds instead of milliseconds. They may occur as a combination of simple tics, such as eye blinking and head-turning and eye blinking. Complex vocal tics may include repeating specific words or phrases, often inappropriate or offensive within the given environment.
Persistent Motor or Vocal Tic Disorder
Persistent Motor or Vocal Tic Disorder is a neurodevelopment motor disorder and one of three tic disorders identified in the DSM-5 manual. Individuals with persistent motor or vocal tic disorder have had the tic symptoms for a minimum of one year.
For a person to be diagnosed with persistent motor or vocal tic disorder, the tics must have started before age 18. Tics are at least twice as common in boys as in girls, and symptoms usually begin before a child reaches puberty, with an average onset between the ages of 4 and 6. Symptoms tend to be at their most severe between the ages of 10 and 12 and improve as the child moves into adolescence.
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