(I) Tourette syndrome (TS): Tourette syndrome is a neurological disorder characterized by repetitive, stereotyped, involuntary movements and vocalizations called tics that are present for at least a year. It typically begins between the ages of 3-9 years and is more common in males.

Tics are classified as either simple or complex.

Simple motor tics are sudden, brief, repetitive movements that involve a limited number of muscle groups. Common simple motor tics include eye blinking and other eye movements, facial grimacing, shoulder shrugging, and head or shoulder jerking.

Simple vocalizations might include repetitive throat-clearing, sniffing, or grunting sounds.

Complex tics are distinct, coordinated patterns of movements involving several muscle groups. Complex motor tics might include facial grimacing combined with a head twist and a shoulder shrug. Other complex motor tics may appear purposeful, including sniffing or touching objects, hopping, jumping, bending, or twisting.

Coprolalia (uttering socially inappropriate words such as swearing) or echolalia (repeating the words or phrases of others) are seen.

Abnormalities in certain brain regions, including the basal ganglia, frontal lobes, cortex, and hypertrophy of the thalamus, have been demonstrated. Low serotonin in the brainstem, low levels of glutamate in the globus pallidus, and low levels of cAMP in the cortex are seen. An increase in the density of the presynaptic dopamine transporter and the postsynaptic D2 dopamine receptor, suggesting increased dopamine activity, has been postulated.

ADHD, depression, anxiety, and OCD may be associated with TS.

(II) Adult onset tic disorders: Onset of tic disorders in adulthood, typically after the age of 21 years, is called adult onset tic disorder. Most cases are secondary to neurodegenerative disorders like Huntington’s disease, brain trauma, cocaine abuse, viral encephalitis, medication side effects, etc.

(III) Essential tremor: It is characterized by involuntary, rhythmic movements of the hands or arms, or less commonly involving the neck, jaw, or tongue. It can be fast or slow. It becomes worse with movement, stress, fatigue, caffeine, and hypoglycemia. It may be inherited in an autosomal dominant fashion.

People with essential tremor are at increased risk of developing Alzheimer’s disease and Parkinson’s syndrome. Essential tremors may briefly subside after the ingestion of alcohol.