They are due to an urge or sensation that eases after performing the movement or the sound.

1. What Are the Types of Tics?

1.1. Primary Tics

• Transient tic disorder

Transient tic disorders are motor or vocal tics that last for less than a year.

• Chronic tic disorder

Chronic tic disorders are motor or vocal tics that last for more than a year.

• Adult-onset tic disorder

Adult-onset tic disorder is a recurrent childhood tic disorder; however, this subtype can be classified as a secondary tic disorder if it is due to acquired conditions such as encephalitis or head trauma [2].

• Tourette syndrome

Tourette syndrome is a neurological disease that affects certain parts of the brain (frontal subcortical circuits) responsible for voluntary movements [3].

It is characterized by both vocal and motor chronic tics that are sudden and repetitive such as blinking, clearing throat, grunting, or facial movements [4].

The genetic causes of Tourette’s Syndrome are unknown; however, some cases are associated with mutations in genes such as SLITRK1, CNTNAP2, and HDC.

SLITRK1 is a protein found in the membrane of neurons where it is involved in the regulation of synapses.

CNTNAP2 is a protein found in the membrane of the neurons where it plays a role in axons, while HDC is an enzyme involved in the function of the neurotransmitter histidine.

1.2. Secondary Tics

Secondary tics can be associated with the following disorders and conditions:

• Global Brain Developmental Disorder

This disorder is due to neurodevelopmental anomalies that lead to delays in the development of social and communication skills, such as autism, mental retardation (intellectual disability), and Pervasive developmental disorders (PDD).

• Infections

Examples of infections that affect the nervous system such as:

Viral Encephalitis

It is an inflammation of the brain caused by a viral infection.

Creutzfeldt–Jakob Disease

Creutzfeldt-Jacob disease is a progressive neurodegenerative disease affecting the brain and causing cognitive disorders such as memory loss, changes in behavior, and ataxia (uncoordinated movements)

The disease is due to the accumulation of a glycoprotein known as a prion, which functions in the brain are not well known [5].

Post-Streptococcal Disorders

Post-streptococcal disorders are autoimmune disorders that happen following infections with a type of bacteria known as Staphylococcus pyogenes.

• Genetic and Neurodegenerative Diseases

Wilson Disease

Wilson disease is a rare genetic disease characterized by the accumulation of copper in different parts of the body including the brain [6].

Huntington Disease

Huntington’s Disease is a neurodegenerative disease that affects the brain causing dementia, depression, difficulty focusing, involuntary movement, stumbling, and clumsiness  [7].

Neuroacanthocytosis

Neuroacanthocytosis is a group of genetic disorders characterized by anomalies of red blood cells (acanthocytosis) and movement disorders [8].

Hallervorden-Spatz Syndrome

Hallervorden-Spatz syndrome is a rare neurodegenerative disease characterized by the accumulation of iron in a part of the brain known as basal ganglia causing its damage [9].

• Drugs

Drugs such as caffeine [10], carbamazepine [11], cocaine [12], and lamotrigine [13].

• Toxins

Carbon monoxide poisoning [14].

• Brain injury

Head trauma [15], stroke (very low supply of oxygen to the brain), and ischemic encephalopathy (low supply of oxygen to the brain) [16].

• Immune Disorders of the Central Nervous System (CNS)

Antiphospholipid Antibody Syndrome

This syndrome is characterized by the production of antibodies against phospholipids in the body which increases the risk of blood clots and thrombosis [17].

Sydenham’s Chorea

Sydenham’s Chorea is a neurological disorder that affects children after an infection with a group A beta-hemolytic streptococcus (GABHS) [18].

• Psychiatric Disorders

Schizophrenia

Schizophrenia is a complex and severe mental health disorder that is classified as a type of psychosis. It is characterized by significant alterations in thoughts, perception, mood, and behaviors [19].

Psychogenic tics

Psychogenic tics are characterized by the sudden onset of brief motor tics that are due to an urge or sensation that can be suppressed. Psychogenic tics can be due to the body’s response to stress [20].

2. What Are the First Signs of Tics?

The initial evaluation of tics is difficult as other disorders may have similar signs such as attention deficit hyperactivity disorder (ADHD), obsessive-compulsive disorder (OCD), dyskinesis, stereotypies, or tourettism [21].

3. Do Tic Disorders Go Away?

An improvement in individuals affected by tics is generally observed by adolescence or early adulthood; therefore, waiting for a period of time can lessen the severity of the tics.

4. How Are Tics Treated?

Most individuals with tics do not seek treatment and education of the affected individual, family, and school environment (e.g., school personnel) about the causes of tics is the initial intervention [21].

This educational approach can prevent such as embarrassment, bullying, anger, self-harm, and social isolation.

However, if the tics become severe, non-pharmacological and pharmacological tic-suppressive medications are provided [21] [22].

• Non-pharmacological treatment

Behavioral Therapy

The aim of this therapy is to help the affected individuals to manage their tics and reduce their severity.

Habit Reversal

This intervention involves awareness training and competing response training.

The awareness training request from the affected individual to name the tic loud, while in the competing response training, the affected individual learns to do a new behavior every time the tic manifests [22].

• Pharmacological treatment

Although most prescribed medications for tics are not approved by the US FDA (Food and Drug Administration), Tics-suppressing medications such as alpha-2-agonists, dopamine blocking agents, are used for severe cases of tics to help individuals with tics with their daily life  [21].

Conclusion

Tic disorders can be primarily associated with Tourette’s syndrome but can also be related to physical and mental disorders, brain injury, drugs, or intoxications. Fortunately, an improvement in individuals affected by tics is generally observed by adolescence or early adulthood. Meanwhile, some of the affected individuals may suffer from embarrassment, bullying, and isolation, due to a lack of education on the causes of tics.

Therefore, is essential that the affected individual learn how to manage the tics in everyday life to reduce associated discomfort, stress, and anxiety.

The education of the family and people in close contact with the affected individual can also significantly reduce embarrassment and bullying through better understanding the difficulties facing an individual with a tic disorder.

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I. How is Pyrophosphate Produced in the joints?

Chondrocytes are specialized cells that control the synthesis of cartilage, from collagen and proteoglycan, and its degradation by enzymes such as collagenase, cathepsins, and proteinases. They also produce inorganic pyrophosphate (PPi) that is used for the formation of calcium pyrophosphate crystals [1].

II. Causes of Chondrocalcinosis

1- Magnesium Deficiency

When there is an excess of calcium pyrophosphate production by the chondrocytes, enzymes including alkaline phosphatase (ALP) and inorganic pyrophosphatases, transform calcium pyrophosphate back into inorganic pyrophosphate.

However, the enzymatic activity of alkaline phosphatase (ALP) requires the presence of magnesium (Mg). Therefore, deficiency in Mg supply results in excessive production and accumulation of calcium pyrophosphate crystals that cannot be transformed into inorganic pyrophosphate (PPi) by alkaline phosphatase (ALP).

2- Post-Injury Arthritis

Although the mechanism is not known, a study that included 3350 arthroscopy samples found an association between chondrocalcinosis and post-traumatic degenerative changes in the meniscus of the knee [2].

3- Hypercalcemia

Hypercalcemia is the presence of calcium at a high level in the blood. It is mainly caused by alterations of the parathyroid function, cancer, vitamin D disorders, and high bone turnover (bone resorption and replacement).

Crystals that are generated in the joint during chondrocalcinosis are made from calcium and inorganic pyrophosphate (PPi) through a process known as nucleation. During hyperglycemia, there is an excess of calcium that increases the formation of calcium pyrophosphate.

4- Acromegaly

Acromegaly is a disorder that is associated with an increased release of growth hormone (GH) by the pituitary gland due to the presence of a tumor.  

Growth hormone (GH) is known to stimulate the activity of the insulin growth factor -1 (IGF-1) that limits the capacity of chondrocytes to produce inorganic pyrophosphate necessary for the formation of calcium pyrophosphate crystals.

Therefore, the increase of growth hormone (GH) by the pituitary gland tumor also increases the stimulation of IGF-1, and thus, should limit the activity of chondrocytes. However, due to the overstimulation of IGF-1, chondrocytes become insensitive and develop resistance to its inhibiting activity leading to excessive production of inorganic pyrophosphate (PPi) and calcium pyrophosphate crystals that accumulate in the joints.

Hypothyroidism

Hypothyroidism is a disorder characterized by a reduced production of the thyroid hormones thyroxine (T4), and triiodothyronine (T3), by the thyroid which is mainly due to iodine deficiency. Iodine is an essential component in the synthesis of T3 and T4. The most common disease associated with hypothyroidism is simple goiter.

Thyroid hormones are known to inhibit the proliferation of mature chondrocytes into hypertrophic chondrocytes that produce mineralized cartilage; however, during hypothyroidism, this inhibition is lifted as these hormones are not sufficiently produced resulting in excessive production of calcium pyrophosphate crystals in the joints.

Gitelman Syndrome

Gitelman Syndrome is a genetic disorder of the kidney characterized by low blood levels of magnesium, potassium, and chloride. The low availability of magnesium (Mg) results in magnesium deficiency leading to excessive production and accumulation of calcium pyrophosphate crystals that cannot be transformed into inorganic pyrophosphate (PPi) by alkaline phosphatase (ALP).

Wilson Disease

Gitelman Syndrome is a genetic disorder characterized by excessive accumulation of copper in the body resulting in neurological and liver anomalies.

Although the mechanism by which copper increases the production of calcium pyrophosphate crystals by chondrocytes is not well known, it was proposed that copper increases the expression of a growth factor known as transforming growth factor-beta 1 (TGFb1) that is involved in stimulating the production of inorganic pyrophosphate (PPi) by chondrocytes.

Another potential mechanism is the association between copper accumulation that excessively stimulates the expression of insulin growth factor -1 (IGF-1) leading to chondrocytes insensitivity to the inhibiting effect of insulin growth factor -1 (IGF-1).

Hemochromatosis

Hemochromatosis is a genetic disorder characterized by excessive intestinal absorption of iron and its accumulation in tissues and organs of the body.

Although the mechanism by which hemochromatosis promotes chondrocalcinosis is not known, it is possible that the accumulation of iron in the joints may promote the function of chondrocytes in producing calcium pyrophosphate crystals through anomalies in iron homeostasis [3].

Pseudogout

Pseudogout or calcium pyrophosphate dihydrate (CPPD) crystal deposition disease is characterized by the deposition of calcium pyrophosphate crystals in the joints.

Although the cause is unknown, it is suggested that the cause may be related to the excessive breakdown of ATP (Adenosine triphosphate) into pyrophosphate which is secreted by the cells of the joints.

How is Chondrocalcinosis Diagnosed?

Chondrocalcinosis manifests with stiffness and inflammation of the joints. It is diagnosed through needle collection of synovial liquid to look for the presence of calcium pyrophosphate crystals. Imaging techniques include X-rays, CT (computerized tomography) scan, MRI (Magnetic resonance imaging), and ultrasound.

The diagnosis is also based on the coexistence of stiffness and inflammation of the joints together with diseases and metabolic disorders such as magnesium deficiency, hypothyroidism, acromegaly, Gitelman Syndrome, Wilson disease, and hypercalcemia.

How is Chondrocalcinosis Treated?

The treatment of chronic chondrocalcinosis appears to be irreversible due to the degeneration of the cartilage tissue. However, the treatment of temporary chondrocalcinosis requires treatment of its related causes. Symptoms such as pain and inflammation are treated using nonsteroidal anti-inflammatory drugs (NSAIDs) or corticosteroids.

Conclusion

Chondrocalcinosis appears to affect mainly and equally women and men over the age of 50; however, it can also affect individuals at a younger age, if associated with post-traumatic injury. Magnesium deficiency appears to be the main cause, and therefore, diet supplementation should help from chondrocalcinosis if there is no degeneration of the joint cartilage.

Although the cellular mechanisms of chondrocalcinosis are not well known, they appear to be associated with alterations in the function of chondrocytes and enzymes that ensure the homeostasis between inorganic pyrophosphate (PPi) production and calcium pyrophosphate crystals generation.

Finally, the stiffness and inflammation associated with chondrocalcinosis can be significantly debilitating for the affected individuals resulting in poor quality of life, and therefore, its early detection can considerably reduce its progression to irreversible degeneration of the cartilage.

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