Motor Disorders

Every time we move our body or a part of it, we're performing a movement. As we grow, the movements we make become targeted (like using a fork), and some movements disappear (like rocking or putting a finger in the mouth). However, we've learned that during growth, things aren't always linear, and even with movement, we may observe behaviors that are slow to be mastered or to vanish. Let's delve into this in detail.

In the diagnostic manual (DSM), the primary movement disorders are:

• Developmental Coordination Disorder
• Stereotypic Movement Disorder
• Tic Disorders

All these disorders emerge during development and don't have a different physiological cause that can explain them.

The Developmental Coordination Disorder is characterized by difficulty in acquiring or performing movements, making them awkward or executed too slowly or imprecisely. Individuals may fall, bump into things, or learn to use utensils, scissors, handwriting, bicycle riding, etc., in an excessively challenging manner.

The Stereotypic Movement Disorder is characterized by repetitive movement that, though intentionally performed, seems to have no specific purpose. Individuals may shake their hands, rock back and forth, head-bang, bite themselves, etc. These behaviors can also be self-injurious.

To discuss Tic Disorders, we need to define what a tic is. A tic is a movement or vocalization with these characteristics:

• Sudden
• Rapid
• Recurrent
• Non-rhythmic

They are divided into:

• Tourette's Disorder
• Persistent (Chronic) Motor or Vocal Tic Disorder
• Provisional Tic Disorder

Tourette's Disorder is characterized by the coexistence of multiple motor tics and at least one vocal tic. The tics persisted for more than a year. Persistent (Chronic) Motor or Vocal Tic Disorder is characterized by the presence of motor and vocal tics, but never occurring simultaneously. Again, these tics persisted for more than a year. Provisional Tic Disorder is characterized by motor and vocal tics present for less than a year.

Tics are divided into:

• Simple: Lasting a few milliseconds. For instance, shrugging shoulders, blinking, sniffing.
• Complex: Lasting a few seconds.

Some types of complex vocal tics are:

• Echolalia: Repeating the last word or phrase heard.
• Palilalia: Repeating one's own sounds.
• Coprolalia: Uttering socially unacceptable words, from obscenities to insults.

Some types of complex motor tics are:

• Echopraxia: Imitating someone else's movements.
• Copropraxia: Making obscene gestures.

Sources:

• American Psychiatric Association (2013) - Diagnostic and Statistical Manual of Mental Disorders (5th ed.).
• Bernhill, J. W. (2014) - DSM-5 Clinical Cases.

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