In mild cases, ET can manifest as the inability to stop the tongue or hands from shaking, the ability to sing only in vibrato, and difficulty doing small precise tasks such as threading a needle. Even simple tasks like cutting in a straight line or using a ruler can range from difficult to impossible, depending on the severity of the condition. In disabling cases, ET can interfere with a person's activities of daily living, including feeding, dressing, and taking care of personal hygiene. Essential tremor generally presents as a rhythmic tremor (4–12 Hz) that occurs only when the affected muscle is exerting effort. Any sort of physical or mental stress will tend to make the tremor worse.

The tremor may also occur in the head (neck), jaw and voice as well as other body regions, with the general pattern being that the tremor begins in the arms and then spreads to these other regions in some people. Women are more likely to develop the head tremor than are men. Other types of tremor may also occur, including postural tremor of the outstretched arms, intention tremor of the arms and rest tremor in the arms. Some people may have unsteadiness and problems with gait and balance.

ET-related tremors do not occur during sleep, but people with ET sometimes complain of an especially coarse tremor upon awakening that becomes noticeably less coarse within the first few minutes of wakefulness. Tremor and disease activity/intensity can worsen in response to fatigue, strong emotions, low blood sugar, cold and heat, caffeine, lithium salts, some antidepressants, and other factors. It is typical for the tremor to worsen in "performance" situations, such as when writing a check for payment at a store or giving a presentation.

Parkinson's disease and Parkinsonism can also occur simultaneously with ET. In those cases the degree of tremor, rigidity, and functional disability does not differ from those people with idiopathic Parkinson's disease. Hand tremor predominates (as it does in Parkinson’s disease), and occurs in nearly all cases, followed by head tremor, voice tremor, neck, face, leg, tongue and trunk tremor. Most other tremors occur in association with hand tremor. Walking difficulties in essential tremor are common. About half of patients have associated dystonia, including cervical dystonia, writer's cramp, spasmodic dysphonia, and cranial dystonia, and 20% of the patients had associated parkinsonism. Olfactory dysfunction (loss of sense of smell) is common in Parkinson’s disease, and has also been reported to occur in patients with essential tremor. A number of patients with essential tremor also exhibit many of the same neuropsychiatric disturbances seen in idiopathic Parkinson's disease.

Essential tremor with tremor onset after the age of 65 is associated with Mild cognitive impairement and dementia.

This type of tremor is often referred to as "kinetic tremor".

Essential tremor has been known as "benign essential tremor", but the adjective "benign" has been removed in recognition of the sometimes disabling nature of the disorder.

Restless leg syndrome is a disorder in which patients feel uncomfortable or unpleasant sensations in the legs. These sensations usually occur in the evening, while the patient is sitting or lying down and relaxing. Patients feel like they have to move their legs to relieve the sensations, and walking generally makes the symptoms disappear. In many patients, this can lead to insomnia and excessive daytime sleepiness. This is a very common problem and can occur at any age.

Similarly, the syndrome akathisia ranges from mildly compulsive movement usually in the legs to intense frenzied motion. These movements are partly voluntary, and the individual typically has the ability to suppress them for short amounts of time. Like restless leg syndrome, relief results from movement.

Tremor is most commonly classified by clinical features and cause or origin. Some of the better known forms of tremor, with their symptoms, include the following:

- Cerebellar tremor (also known as intention tremor) is a slow, broad tremor of the extremities that occurs at the end of a purposeful movement, such as trying to press a button or touching a finger to the tip of one’s nose. Cerebellar tremor is caused by lesions in or damage to the cerebellum resulting from stroke, tumor, or disease such as multiple sclerosis or some inherited degenerative disorder. It can also result from chronic alcoholism or overuse of some medicines. In classic cerebellar tremor, a lesion on one side of the brain produces a tremor in that same side of the body that worsens with directed movement. Cerebellar damage can also produce a “wing-beating” type of tremor called rubral or Holmes’ tremor — a combination of rest, action, and postural tremors. The tremor is often most prominent when the affected person is active or is maintaining a particular posture. Cerebellar tremor may be accompanied by other manifestations of ataxia, including dysarthria (speech problems), nystagmus (rapid, involuntary rolling of the eyes), gait problems and postural tremor of the trunk and neck. "Titubation" is tremor of the head and is of cerebellar origin.

- Dystonic tremor occurs in individuals of all ages who are affected by dystonia, a movement disorder in which sustained involuntary muscle contractions cause twisting and repetitive motions and/or painful and abnormal postures or positions. Dystonic tremor may affect any muscle in the body and is seen most often when the patient is in a certain position or moves a certain way. The pattern of dystonic tremor may differ from essential tremor. Dystonic tremors occur irregularly and often can be relieved by complete rest. Touching the affected body part or muscle may reduce tremor severity (a geste antagoniste). The tremor may be the initial sign of dystonia localized to a particular part of the body.

- Essential tremor (sometimes called benign essential tremor) is the most common of the more than 20 types of tremor. Although the tremor may be mild and nonprogressive in some people, in others, the tremor is slowly progressive, starting on one side of the body but affecting both sides within 3 years. The hands are most often affected but the head, voice, tongue, legs, and trunk may also be involved. Head tremor may be seen as a vertical or horizontal motion. Essential tremor may be accompanied by mild gait disturbance. Tremor frequency may decrease as the person ages, but the severity may increase, affecting the person’s ability to perform certain tasks or activities of daily living. Heightened emotion, stress, fever, physical exhaustion, or low blood sugar may trigger tremors or increase their severity. Onset is most common after age 40, although symptoms can appear at any age. It may occur in more than one family member. Children of a parent who has essential tremor have a 50 percent chance of inheriting the condition. Essential tremor is not associated with any known pathology.

- Orthostatic tremor is characterized by fast (>12 Hz) rhythmic muscle contractions that occur in the legs and trunk immediately after standing. Cramps are felt in the thighs and legs and the patient may shake uncontrollably when asked to stand in one spot. No other clinical signs or symptoms are present and the shaking ceases when the patient sits or is lifted off the ground. The high frequency of the tremor often makes the tremor look like rippling of leg muscles while standing. Orthostatic tremor may also occur in patients who have essential tremor, and there might be an overlap between these categories of tremor.

- Parkinsonian tremor is caused by damage to structures within the brain that control movement. This resting tremor, which can occur as an isolated symptom or be seen in other disorders, is often a precursor to Parkinson's disease (more than 25 percent of patients with Parkinson’s disease have an associated action tremor). The tremor, which is classically seen as a "pill-rolling" action of the hands that may also affect the chin, lips, legs, and trunk, can be markedly increased by stress or emotion. Onset is generally after age 60. Movement starts in one limb or on one side of the body and usually progresses to include the other side.

- Physiological tremor occurs in every normal individual and has no clinical significance. It is rarely visible and may be heightened by strong emotion (such as anxiety or fear), physical exhaustion, hypoglycemia, hyperthyroidism, heavy metal poisoning, stimulants, alcohol withdrawal or fever. It can be seen in all voluntary muscle groups and can be detected by extending the arms and placing a piece of paper on top of the hands. Enhanced physiological tremor is a strengthening of physiological tremor to more visible levels. It is generally not caused by a neurological disease but by reaction to certain drugs, alcohol withdrawal, or medical conditions including an overactive thyroid and hypoglycemia. It is usually reversible once the cause is corrected. This tremor classically has a frequency of about 10 Hz

- tremor (also called hysterical tremor) can occur at rest or during postural or kinetic movement. The characteristics of this kind of tremor may vary but generally include sudden onset and remission, increased incidence with stress, change in tremor direction and/or body part affected, and greatly decreased or disappearing tremor activity when the patient is distracted. Many patients with psychogenic tremor have a conversion disorder (see Posttraumatic stress disorder) or another psychiatric disease.

- Rubral tremor is characterized by coarse slow tremor which is present at rest, at posture and with intention. This tremor is associated with conditions which affect the red nucleus in the midbrain, classically unusual strokes.

Tremor can result from other conditions as well

- Alcoholism, excessive alcohol consumption, or alcohol withdrawal can kill certain nerve cells, resulting in a tremor known as asterixis. Conversely, small amounts of alcohol may help to decrease familial and essential tremor, but the mechanism behind it is unknown. Alcohol potentiates GABAergic transmission and might act at the level of the inferior olive.

- Tremor in peripheral neuropathy may occur when the nerves that supply the body’s muscles are traumatized by injury, disease, abnormality in the central nervous system, or as the result of systemic illnesses. Peripheral neuropathy can affect the whole body or certain areas, such as the hands, and may be progressive. Resulting sensory loss may be seen as a tremor or ataxia (inability to coordinate voluntary muscle movement) of the affected limbs and problems with gait and balance. Clinical characteristics may be similar to those seen in patients with essential tremor.

- Tobacco withdrawal symptoms include tremor.

- Most of the symptoms can also occur randomly when panicked.

Wilson's disease (WD) is a rare inherited disorder in which patients have a problem metabolizing copper. In patients with WD, copper accumulates in the liver and other parts of the body, particularly the brain, eyes and kidneys. Upon accumulation in the brain, patients may experience speech problems, incoordination, swallowing problems, and prominent hyperkinetic symptoms including tremor, dystonia, and gait difficulties. Psychiatric disturbances such as irritability, impulsiveness, aggressiveness, and mood disturbances are also common.

Holmes tremor is typically characterized by a low frequency tremor (below 4.5 Hz) that has a repeated series of rest and intention tremors. These tremors move slowly and are generally specific to an upper area of the body. They can consist of postural tremors in nearby muscles as well. These tremors involve uncontrollable shaking despite efforts to be still. Holmes tremor is considered a rest-intention posture tremor. These irregular movements occur while muscles are at rest, but worsen during voluntary muscle contractions. Symptoms usually appear delayed one to twenty-four months after the lesion is created.

Intention tremor, also known as cerebellar tremor, is a dyskinetic disorder characterized by a broad, coarse, and low frequency (below 5 Hz) tremor. The amplitude of an intention tremor increases as an extremity approaches the endpoint of deliberate and visually guided movement (hence the name intention tremor). An intention tremor is usually perpendicular to the direction of movement. When experiencing an intention tremor, one often overshoots or undershoots their target, a condition known as dysmetria. Intention tremor is the result of dysfunction of the cerebellum, particularly on the same side as the tremor in the lateral zone, which controls visually guided movements. Depending on the location of cerebellar damage, these tremors can be either unilateral or bilateral.

A variety of causes have been discovered to date, including damage or degradation of the cerebellum due to neurodegenerative diseases, trauma, tumor, stroke, or toxicity. There is currently no established pharmacological treatment; however, some success has been seen using treatments designed for essential tremors.

Intention tremors are common among individuals with multiple sclerosis (MS). One common symptom of multiple sclerosis is ataxia, a lack of coordinated muscle movement caused by cerebellar lesions characteristic of multiple sclerosis. The disease often destroys physical and cognitive function of individuals.

Intention tremors can be a first sign of multiple sclerosis, since loss or deterioration of motor function and sensitivity are often one of the first symptoms of cerebellar lesions.

Intention tremors have a variety of other recorded causes as well. These include a variety of neurological disorders, such as stroke, alcoholism, alcohol withdrawal, peripheral neuropathy, Wilson's disease, Creutzfeldt–Jakob disease, Guillain–Barré syndrome and fragile X syndrome, as well as brain tumors, low blood sugar, hyperthyroidism, hypoparathyroidism, insulinoma, normal aging, and traumatic brain injury. Holmes tremor, a rubral or midbrain tremor, is another form of tremor that includes intention tremors, among other symptoms. This disease affects the proximal muscles of the head, shoulders, and neck. Tremors of this disease occur at frequencies of 2–4 Hz or more.

Intention tremor is also known to be associated with infections, West Nile virus, rubella, H. influenza, rabies, and varicella. A variety of poisons have been shown to cause intention tremor, including mercury, methyl bromide, and phosphine. In addition, vitamin deficiencies have been linked to intention tremor, especially deficiency in vitamin E. Pharmacological agents such as anti-arrhythmic drugs, anti-epileptic agents, benzodiazepine, cyclosporine, lithium, neuroleptics, and stimulants have been known to cause intention tremor. Some ordinary activities including ingesting too much caffeine, cigarettes, and alcohol, along with stress, anxiety, fear, anger and fatigue

have also been shown to cause intention tremor by negatively affecting the cerebellum, brainstem, or thalamus, as discussed in mechanisms.

Tremor can be a symptom associated with disorders in those parts of the brain that control muscles throughout the body or in particular areas, such as the hands. Neurological disorders or conditions that can produce tremor include multiple sclerosis, stroke, traumatic brain injury, chronic kidney disease and a number of neurodegenerative diseases that damage or destroy parts of the brainstem or the cerebellum, Parkinson's disease being the one most often associated with tremor. Other causes include the use of drugs (such as amphetamines, cocaine, caffeine, corticosteroids, SSRIs) or alcohol, mercury poisoning, or the withdrawal of drugs such as alcohol or benzodiazepine. Tremors can also be seen in infants with phenylketonuria (PKU), overactive thyroid or liver failure. Tremors can be an indication of hypoglycemia, along with palpitations, sweating and anxiety.

Tremor can also be caused from lack of sleep, lack of vitamins, or increased stress. Deficiencies of magnesium and thiamine have also been known to cause tremor or shaking, which resolves when the deficiency is corrected. See magnesium in biology. Some forms of tremor are inherited and run in families, while others have no known cause. Tremors can also be caused by some spider bites, e.g. the redback spider of Australia.

Characteristics may include a rhythmic shaking in the hands, arms, head, legs, or trunk; shaky voice; and problems holding things such as a fork or pen. Some tremors may be triggered by or become exacerbated during times of stress or strong emotion, when the individual is physically exhausted, or during certain postures or movements.

Tremor may occur at any age but is most common in middle-age and older persons. It may be occasional, temporary, or occur intermittently. Tremor affects men and women equally.

Though it is often most associated with Parkinson's disease, hypokinesia can be present in a wide variety of other conditions.

Holmes tremor, first identified by Gordon Holmes in 1904, can be described as a wing-beating movement localized in the upper body that is caused by cerebellar damage. Holmes tremor is a combination of rest, action, and postural tremors. Tremor frequency ranges from 2 to 5 Hertz and is aggravated with posture and movement. It may arise from various underlying structural disorders including stroke, tumors, trauma, and other cerebellar lesions. Because Holmes tremor is rare, much of the research is based on individual cases.

The formation of tremors is due to two main factors: the over-excited rhythmic movement of neuronal loops and permanent structural changes from neurodegeneration. Two major neuronal networks, the corticostriatothalamocortical hap and the inferior olivary nucleus (ION) specifically target the development of the tremors. When diagnosing a patient with Holmes tremor, one must look at the neurological signs and symptoms, as well as the possibility that the tremor is caused by medications or other stimulants. In most cases, the patient’s history and a targeted neurological examination is enough to give a diagnosis.

Treatment for Holmes tremor is dependent on the characteristics of the tremor. Because the disease is involved with the dopaminergic system, most treatments involve levodopa. Drugs used to treat other types of tremors are applicable to the treatment of Holmes tremor; however, these drugs have a low success rate.

Initial symptoms of spasmodic torticollis are usually mild. Some feel an invisible tremor of their head for a few months at onset. Then the head may turn, pull or tilt in jerky movements, or sustain a prolonged position involuntarily. Over time, the involuntary spasm of the neck muscles will increase in frequency and strength until it reaches a plateau. Symptoms can also worsen while the patient is walking or during periods of increased stress. Other symptoms include muscle hypertrophy, neck pain, dysarthria and tremor. Studies have shown that over 75% of patients report neck pain, and 33% to 40% experience tremor of the head.

Differentiating some kinds of atypical Parkinson: Northwest Parkinson Foundation

Before Parkinson's disease is diagnosed, the differential diagnoses include:

- AIDS can sometimes lead to the symptoms of secondary parkinsonism, due to commonly causing dopaminergic dysfunction. Indeed, parkinsonism can be a presenting feature of HIV infection.

- Corticobasal degeneration

- Creutzfeldt–Jakob disease

- Dementia pugilistica or "boxer's dementia" is a condition that occurs in athletes due to chronic brain trauma.

- Diffuse Lewy body disease

- Drug-induced parkinsonism ("pseudoparkinsonism") due to drugs such as antipsychotics, metoclopramide, sertraline, fluoxetine or the toxin MPTP

- Encephalitis lethargica

- Essential tremor, an illness which has some diagnostic overlap with Parkinson's disease

- Orthostatic tremor

- MDMA addiction and frequent use has been linked to Parkonsonism. Several cases have been reported where individuals are diagnosed with the syndrome after taking MDMA.

- Multiple system atrophy

- Pantothenate kinase-associated neurodegeneration, also known as neurodegeneration with brain iron accumulation or Hallervorden-Spatz syndrome

- Parkinson plus syndrome

- Progressive supranuclear palsy

- Toxicity due to substances such as carbon monoxide, carbon disulfide, manganese, paraquat, mercury, hexane, rotenone, Annonaceae, and toluene (inhalant abuse: "huffing")

- Vascular parkinsonism, associated with underlying cerebrovascular disease

- Wilson's disease is a genetic disorder in which an abnormal accumulation of copper occurs. The excess copper can lead to the formation of a copper-dopamine complex, which leads to the oxidation of dopamine to aminochrome. The most common manifestations include bradykinesia, cogwheel rigidity and a lack of balance.

- Paraneoplastic syndrome: neurological symptoms caused by antibodies associated with cancers

- Genetic

- Rapid onset dystonia parkinsonism

- Parkin mutation

- X-linked dystonia parkinsonism

- Autosomal recessive juvenile parkinsonism

Stress causes alterations of cerebral circulation, increasing blood flow in the supramarginal gyrus and angular gyrus of the parietal lobe, the frontal lobe, and the superior temporal gyrus of the left hemisphere. Also, an increase in cardiac activity and change in the tonus of the heart vessels occurs, which is an elementary indication of stress development. In patients with normal stress, an adaptive fight-or-flight response is usually triggered by sympathetic nervous system activation. Hypokinesia patients experience these typical stress symptoms on a regular basis because of damage to the basal ganglia system. Therefore, when a hypokinesia victim is under stress, he or she does not display a typical fight-or-flight response, placing the patient under greater danger from potentially harmful stimuli. Low-impact exercise, elimination of drug and alcohol use, and regular meditation can help to restore normal stress responses in hypokinesia patients.

Parkinsonism is a clinical syndrome characterized by tremor, bradykinesia, rigidity, and postural instability. Parkinsonism is found in Parkinson's disease (after which it is named), however a wide range of other causes may lead to this set of symptoms, including some toxins, a few metabolic diseases, and a handful of neurological conditions other than Parkinson's disease.

About 7% of people with parkinsonism have developed their symptoms following treatment with particular medications. Side effect of medications, mainly neuroleptic antipsychotics especially the phenothiazines (such as perphenazine and chlorpromazine), thioxanthenes (such as flupenthixol and zuclopenthixol) and butyrophenones (such as haloperidol), piperazines (such as ziprasidone), and rarely, antidepressants. The incidence of drug-induced parkinsonism increases with age. Drug-induced parkinsonism tends to remain at its presenting level, not progress like Parkinson's disease.

Spasmodic torticollis is a form of focal dystonia, a neuromuscular disorder that consists of sustained muscle contractions causing repetitive and twisting movements and abnormal postures in a single body region. There are two main ways to categorize spasmodic torticollis: age of onset, and cause. The disorder is categorized as early onset if the patient is diagnosed before the age of 27, and late onset thereafter. The causes are categorized as either primary (idiopathic) or secondary (symptomatic). Spasmodic torticollis can be further categorized by the direction and rotation of head movement.

Oromandibular Symptoms

- difficulty opening the mouth (trismus)

- clenching or grinding of the teeth (bruxism)

- spasms of jaw opening

- sideways deviation or protrusion of the jaw

- lip tightening and pursing

- drawing back (retraction) of the corners of the mouth

- deviation or protrusion of the tongue.

- jaw pain

- difficulties eating and drinking

- difficulties speaking (dysarthria)

Blepharospasm symptoms

- the first symptom to appear is an increased rate of blinking

- uncontrollable squinting/closing of eyes

- light sensitivity (photophobia)

- squinting/eyes closing during speech

- uncontrollable eyes closing shut (rare instances completely causing blindness)

In addition, in some patients, the dystonic spasms may sometimes be provoked by certain activities, such as talking, chewing, or biting. Particular activities or sensory tricks may sometimes temporarily alleviate OMD symptoms, including chewing gum, talking, placing a toothpick in the mouth, lightly touching the lips or chin, or applying pressure beneath the chin.

The Greek word "blepharon" means "eyelid". Spasm means "uncontrolled muscle contraction". The term blepharospasm ['blef-a-ro-spaz-m] can be applied to any abnormal blinking or eyelid tic or twitch resulting from any cause, ranging from dry eyes to Tourette's syndrome to tardive dyskinesia. The blepharospasm referred to here is officially called benign essential blepharospasm (BEB) to distinguish it from the less serious secondary blinking disorders. "Benign" indicates the condition is not life-threatening, and "essential" is a medical term meaning "of unknown cause". It is both a cranial and a focal dystonia. Cranial refers to the head and focal indicates confinement to one part. The word dystonia describes abnormal involuntary sustained muscle contractions and spasms. Patients with blepharospasm have normal eyes. The visual disturbance is due solely to the forced closure of the eyelids.

Oromandibular dystonia (OMD) is a form of focal dystonia that affects varying areas of the head and neck including the lower face, jaw, tongue and larynx. The spasms may cause the mouth to pull open, shut tight, or move repetitively. Speech and swallowing may be distorted. It is often associated with dystonia of the cervical muscles (Spasmodic Torticollis), eyelids (Blepharospasm), or larynx (Spasmodic Dysphonia).

In patients with OMD, involuntary contractions may involve the muscles used for chewing (masticatory muscles). These may include the thick muscle in the cheek that closes the jaw (masseter muscle) and the broad muscle that draws back the lower jaw and closes the mouth (temporalis muscle). Some patients may also experience involuntary contractions of the wide muscle at the side of the neck (platysmal muscle). This muscle draws down the corner of the mouth and lower lip or other muscle groups.

Onset of symptoms usually occur in early adulthood and is characterized by intention tremor, progressive ataxia, convulsions, and myoclonic epileptic jerks.

Tremors usually affect one extremity, primarily the upper limb, and eventually involve the entire voluntary motor system. Overall, the lower extremity is usually disturbed less often than the upper extremity.

Additional features of the syndrome include: an unsteady gait, seizures, muscular hypotonia, reduced muscular coordination, asthenia, adiadochokinesia and errors with estimating range, direction, and force of voluntary movements. Mental deterioration can occur, however it is rare.

The main symptom of benign fasciculation syndrome is focal or widespread involuntary muscle activity (twitching), which can occur at random or specific times (or places). Presenting symptoms of benign fasciculation syndrome may include:

- Fasciculations (primary symptom)

- Blepharospasms (eye spasms)

- Generalized fatigue

- Muscle pain

- Anxiety (which can also be a cause)

- Exercise intolerance

- Globus sensation

- Paraesthesias

- Muscle cramping or spasms

Other symptoms include:

- Hyperreflexia

- Muscle stiffness

- Tremors

- Itching

- Myoclonic jerks

BFS symptoms are typically present when the muscle is at rest and are not accompanied by severe muscle weakness. In some BFS cases, fasciculations can jump from one part of the body to another. For example, it could start in a leg muscle, then in a few seconds jump to the forehead, then the abdomen, etc. Because fasciculations can occur on the head, this strongly suggests the brain as the generator due to its exclusive non-dependence on the spinal cord. (Together, the brain and spinal cord comprise the central nervous system.)

Anxiety is often caused as a result of BFS, and a lot of sufferers have hypochondria as BFS mimics symptoms of much more serious diseases such as amyotrophic lateral sclerosis (ALS).

Symptoms typically present in the 3rd or 4th decade of life, but have been seen as early as the age of 14. It presents with torsion dystonia, particularly when presenting at a younger age, which then progresses to parkinsonism with or without ongoing dystonia. Often the two symptoms coexist.The parkinsonian features of x-linked dystonia parkinsonism include festinating gait, bradykinesia, blepharospasm, and postural instability. It often lacks a resting tremor, helping to differentiate it from Parkinson's disease.

RHS type 1 is caused by the impairment of a regulatory mechanism between cerebellar and brainstem nuclei and has been associated with a wide range of diseases, including Lafora disease, dentatorubropallidoluysian atrophy, and celiac disease.

Parkinson-plus syndromes, also known as disorders of multiple system degeneration, is a group of neurodegenerative diseases featuring the classical features of Parkinson's disease (tremor, rigidity, akinesia/bradykinesia, and postural instability) with additional features that distinguish them from simple idiopathic Parkinson's disease (PD). Some consider Alzheimer's disease to be in this group. Parkinson-plus syndromes are either inherited genetically or occur sporadically.

The atypical parkinsonian or Parkinson-plus syndromes are often difficult to differentiate from PD and each other. They include multiple system atrophy (MSA), progressive supranuclear palsy (PSP), and corticobasal degeneration (CBD). Dementia with Lewy bodies (DLB), may or may not be part of the PD spectrum, but it is increasingly recognized as the second-most common type of neurodegenerative dementia after Alzheimer's disease. These disorders are currently lumped into two groups, the synucleinopathies and the tauopathies. They may coexist with other pathologies.

Additional Parkinson-plus syndromes include Pick's disease and olivopontocerebellar atrophy. The latter is characterized by ataxia and dysarthria, and may occur either as an inherited disorder or as a variant of multiple system atrophy. MSA is also characterized by autonomic failure, formerly known as Shy–Drager syndrome.

Clinical features that distinguish Parkinson-plus syndromes from idiopathic PD include symmetrical onset, a lack of or irregular resting tremor, and a reduced response to dopaminergic drugs (including levodopa). Additional features include bradykinesia, early-onset postural instability, increased rigidity in axial muscles, dysautonomia, alien limb syndrome, supranuclear gaze palsy, apraxia, involvement of the cerebellum including the pyramidal cells, and in some instances significant cognitive impairment.

Abnormalities in diadochokinesia can be seen in the upper extremity, lower extremity and in speech. The deficits become visible in the rate of alternation, the completeness of the sequence, and in the variation in amplitude involving both motor coordination and sequencing. Average rate can be used as a measure of performance when testing for dysdiadochokinesia.

Dysdiadochokinesia is demonstrated clinically by asking the patient to tap the palm of one hand with the fingers of the other, then rapidly turn over the fingers and tap the palm with the back of them, repeatedly. This movement is known as a pronation/supination test of the upper extremity. A simpler method using this same concept is to ask the patient to demonstrate the movement of trying a doorknob or screwing in a light bulb. When testing for this condition in legs, ask the patient to tap your hand as quickly as possible with the ball of each foot in turn. Movements tend to be slow or awkward. The feet normally perform less well than the hands. When testing for dysdiadochokinesia with speech the patient is asked to repeat syllables such as /pə/, /tə/, and /kə/; variation, excess loudness, and irregular articular breakdown are signs of dysdiadochokinesia.

Blepharospasm is any abnormal contraction or twitch of the eyelid. In most cases, symptoms last for a few days then disappear without treatment, but sometimes the twitching is chronic and persistent, causing lifelong challenges. In those rare cases, the symptoms are often severe enough to result in functional blindness. The person's eyelids feel like they are clamping shut and will not open without great effort. People have normal eyes, but for periods of time are effectively blind due to their inability to open their eyelids. In contrast, the reflex blepharospasm is due to any pain in and around the eye.

It is of two types: essential and reflex blepharospasm. The benign essential blepharospasm is a focal dystonia—a neurological movement disorder involving involuntary and sustained contractions of the muscles around the eyes. The term "essential" indicates that the cause is unknown, but fatigue, stress, or an irritant are possible contributing factors.

Although there is no cure botulinum toxin injections may help temporarily. A surgical procedure known as myectomy may also be useful. It is a fairly rare disease, affecting only one in every 20,000 people in the United States. The word is from Greek: βλέφαρον / blepharon, eyelid, and σπασμός / spasmos, "spasm," an uncontrolled muscle contraction.