Tic

Tics are classified as either motor or phonic, and simple or complex. Motor tics can be of an endless variety and may include such movements as hand clapping, neck stretching, mouth movements, head, arm or leg jerks, and facial grimacing. A simple phonic tic can be almost any sound or noise, with common phonic tics being throat clearing, sniffing, or grunting. == Characteristics ==

Tics are described as semi-voluntary or unvoluntary, because they are not strictly involuntary—they may be experienced as a voluntary response to a premonitory urge (a sensory phenomenon that is an inner sensation of mounting tension). A unique aspect of tics, relative to other movement disorders, is that they are suppressible yet irresistible; they are experienced as an irresistible urge that must eventually be expressed. Relaxation may result in a tic increase (for instance, watching television or using a computer), while concentration on an absorbing activity often leads to a decrease in tics. Neurologist and writer Oliver Sacks described a physician with severe Tourette syndrome (Canadian Mort Doran, M.D., a pilot and surgeon in real life, although a pseudonym was used in the book), whose tics remitted almost completely while he was performing surgery. Immediately preceding tic onset, most individuals are aware of an urge that is similar to the need to yawn, sneeze, blink, or scratch an itch. Individuals describe the need to tic as a buildup of tension that they consciously choose to release, as if they "had to do it". Examples of this premonitory urge are the feeling of having something in one's throat or a localized discomfort in the shoulders, leading to the need to clear one's throat or shrug the shoulders. The actual tic may be felt as relieving this tension or sensation, similar to scratching an itch. Another example is blinking to relieve an uncomfortable sensation in the eye. Some people with tics may not be aware of the premonitory urge. Children may be less aware of the premonitory urge associated with tics than are adults, but their awareness tends to increase with maturity. as in the case of klazomania (compulsive shouting). ==Diagnosis==

Tic disorders occur along a spectrum, ranging from mild (transient or chronic tics) to more severe; Tourette syndrome is the more severe expression of a spectrum of tic disorders, which are thought to be due to the same genetic vulnerability. Management for the spectrum of tic disorders is similar to the management of Tourette syndrome. Tic disorders are defined based on symptoms and duration. The fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), published in May 2013, reclassified Tourette's and tic disorders as motor disorders listed in the neurodevelopmental disorder category, removed the word "stereotyped" from the definition of tic to better distinguish between stereotypies and tics, replaced transient tic disorder with provisional tic disorder, removed the criterion that tics must occur nearly every day, and removed the criterion that previously had excluded long tic-free periods (months) from counting towards the year needed to diagnose Tourette's or Persistent (Chronic) tic disorders. Differential diagnosis Dystonias, paroxysmal dyskinesias, chorea, other genetic conditions, and secondary causes of tics should be ruled out in the differential diagnosis. and stereotypic movement disorder; Sydenham's chorea; idiopathic dystonia; and genetic conditions such as Huntington's disease, neuroacanthocytosis, pantothenate kinase-associated neurodegeneration, Duchenne muscular dystrophy, Wilson's disease, and tuberous sclerosis. Other possibilities include chromosomal disorders such as Down syndrome, Klinefelter syndrome, XYY syndrome, and fragile X syndrome. Acquired causes of tics include drug-induced tics, head trauma, encephalitis, stroke, and carbon monoxide poisoning. Most of these conditions are rarer than tic disorders, and a thorough history and examination may be enough to rule them out, without medical or screening tests. Tics that begin after the age of 18 are not diagnosed as Tourette's syndrome, but may be diagnosed as an "other specified" or "unspecified" tic disorder. TSH levels can be measured to rule out hypothyroidism, which can be a cause of tics. Brain imaging studies are not usually warranted. Individuals with obsessive–compulsive disorder (OCD) may present with features typically associated with a tic disorder, such as compulsions that may resemble motor tics. "Tic-related OCD" is hypothesized to be a subgroup of OCD, distinguished from non-tic-related OCD by the content and type of obsessions and compulsions; individuals with tic-related OCD have more intrusive thoughts, and exhibit more hoarding and counting rituals than individuals with non-tic-related OCD. Tics must also be distinguished from fasciculations. Small twitches of the upper or lower eyelid, for example, are not tics, because they do not involve a whole muscle, rather are twitches of a few muscle fibre bundles, that are not suppressible. ==See also==