Congenital mirror movement disorder (CMM disorder) is a rare genetic neurological disorder which is characterized by mirrored movement, sometimes referred to as associated or synkinetic movement, most often in the upper extremity of the body. These movements are voluntary intentional movements on one, ipsilateral, side of the body that are mirrored simultaneously by involuntary movements on the contralateral side.

The reproduction of involuntary movement usually happens along the head-tail axis, having a left-right symmetry. For example, if someone were to voluntarily make a fist with their left hand, their right hand would do the same. In most cases, the accompanying contralateral involuntary movements are much weaker than the ipsilateral voluntary ones, although the extent and magnitude of the mirrored movement vary across patients. This disorder has not yet been found to be associated with any other neurologic disease or cognitive disability, and currently, no cures nor means to improve signs or symptoms have been found.

The congenital mirror movements begin in infancy and persist throughout the patient’s life, often with very little improvement, or deterioration. Consequently, patients who do suffer from this movement disorder have serious difficulty carrying out tasks that require manual dexterity or precision, such as playing a two handed musical instrument or typing on a keyboard, for their whole lives. Patients also often experience discomfort or pain in the upper limbs due to prolonged use of the same muscles. Therefore, quality of life can be severely hampered.

CMM disorder’s prevalence in the world is thought to be less than 1 in 1 million people. Because of its rarity, researchers suggest that some mildly affected individuals may never be diagnosed. It is important not to confuse congenital mirror movement disorders, a rare genetically based neurologic disease, with acquired mirror movement disorders that present themselves during one’s lifetime due to other reasons (stroke for example).

Currently, clinical diagnosis of CMM disorder has been based on clinical findings or molecular genetic testing.

"Clinical Findings (Signs and Symptoms)"""":"

- onset of mirror movements in infancy or early childhood

- persistence of mirror movements into and throughout adulthood with the absence of other neurologic disorders

- little improvement nor deterioration of mirror movements over the course of one’s life

- intensity of mirrored movements increasing with the complexity of the voluntary movement

- involuntary mirror movements that are generally of lesser amplitude compared with voluntary movements

- predominant mirror movement in upper limbs, with increasing severity in more distal appendages (fingers)

- inability to perform tasks requiring skilled bimanual coordination

- occasional pain in the upper limbs during prolonged manual activities

- occasional observed subclinical mirroring movement, but detectable with accelerometer gloves

"Molecular genetic testing"":"

- identification of a heterozygous mutant "DCC, DNAL4, or RAD51" gene (single gene test or multi-gene panel)

Most cases of autosomal recessive cerebellar ataxia are early onset, usually around the age of 20. People with this type of ataxia share many characteristic symptoms including:

- frequent falls due to poor balance

- imprecise hand coordination

- postural or kinetic tremor of extremities or trunk

- dysarthria

- dysphasia

- vertigo

- diplopia

- lower extremity tendon reflexes

- dysmetria

- minor abnormalities in ocular saccades

- attention defects

- impaired verbal working memory and visuospatial skills

- Normal life expectancy

Autosomal recessive ataxias are generally associated with a loss of proprioception and vibration sense. Arreflexia is more common in autosomal recessive ataxia than autosomal dominant ataxias. Also, they tend to have more involvement outside of the nervous system. Mutations in subunit of the mitochondrial DNA polymerase (POLG) have been found to be a potential cause of autosomal recessive cerebellar ataxia.

Autosomal recessive cerebellar ataxia type 1 (ARCA1) is a condition characterized by progressive problems with movement. Signs and symptoms of the disorder first appear in early to mid-adulthood. People with this condition initially experience impaired speech (dysarthria), problems with coordination and balance (ataxia), or both. They may also have difficulty with movements that involve judging distance or scale (dysmetria). Other features of ARCA1 include abnormal eye movements (nystagmus) and problems following the movements of objects with their eyes. The movement problems are slowly progressive, often resulting in the need for a cane, walker, or wheelchair.

Movement disorders are clinical syndromes with either an excess of movement or a paucity of voluntary and involuntary movements, unrelated to weakness or spasticity. Movement disorders are synonymous with basal ganglia or extrapyramidal diseases. Movement disorders are conventionally divided into two major categories- "hyperkinetic" and "hypokinetic".

Hyperkinetic movement disorders refer to dyskinesia, or excessive, often repetitive, involuntary movements that intrude upon the normal flow of motor activity.

Hypokinetic movement disorders refer to akinesia (lack of movement), hypokinesia (reduced amplitude of movements), bradykinesia (slow movement) and rigidity. In primary movement disorders, the abnormal movement is the primary manifestation of the disorder. In secondary movement disorders, the abnormal movement is a manifestation of another systemic or neurological disorder.

Hypotonic patients may display a variety of objective manifestations that indicate decreased muscle tone. Motor skills delay is often observed, along with hypermobile or hyperflexible joints, drooling and speech difficulties, poor reflexes, decreased strength, decreased activity tolerance, rounded shoulder posture, with leaning onto supports, and poor attention. The extent and occurrence of specific objective manifestations depends upon the age of the patient, the severity of the hypotonia, the specific muscles affected, and sometimes the underlying cause. For instance, some people with hypotonia may experience constipation, while others have no bowel problems.

The term "floppy infant syndrome" is used to describe abnormal limpness when an infant is born. Infants who suffer from hypotonia are often described as feeling and appearing as though they are "rag dolls". They are unable to maintain flexed ligaments, and are able to extend them beyond normal lengths. Often, the movement of the head is uncontrollable, not in the sense of spasmatic movement, but chronic ataxia. Hypotonic infants often have difficulty feeding, as their mouth muscles cannot maintain a proper suck-swallow pattern, or a good breastfeeding latch.

The prolonged muscle contractions, which occur most commonly in the leg muscles in recessive mutations, and more commonly in the hands, face, and eyelids in dominant mutations, are often enhanced by inactivity, and in some forms are relieved by repetitive movement known as "the warm-up effect". This effect often diminishes quickly with rest. Some individuals with myotonia congenita are prone to falling as a result of hasty movements or an inability to stabilize themselves after a loss of balance. During a fall, a person with myotonia congenita may experience partial or complete rigid paralysis that will quickly resolve once the event is over. However, a fall into cold water may render the person unable to move for the duration of submergence. As with myotonic goats, children are more prone to falling than adults, due to their impulsivity.

The two major types of myotonia congenita are distinguished by the severity of their symptoms and their patterns of inheritance. Becker disease usually appears later in childhood than Thomsen disease, and causes more severe myotonia, muscle stiffness and transient weakness. Although myotonia in itself is not normally associated with pain, cramps or myalgia may develop. People with Becker disease often experience temporary attacks of muscle weakness, particularly in the arms and hands, brought on by movement after periods of rest. They may also develop mild, permanent muscle weakness over time. This muscle weakness is not observed in people with Thomsen disease. However, in recent times, as more of the individual mutations that cause myotonia congenita are identified, these limited disease classifications are becoming less widely used.

Early symptoms in a child may include:

- Difficulty swallowing

- Gagging

- Stiff movements that improve when they are repeated

- Frequent falling

- Difficulties opening eyelids after strenuous contraction or crying (von Graefe's sign)

Possible complications may include:

- Aspiration pneumonia (caused by swallowing difficulties)

- Frequent choking or gagging in infants (also caused by swallowing difficulties)

- Abdominal muscle weakness

- Chronic joint problems

- Injury due to falls

Facial Synkinesis is a common sequela to Idiopathic Facial Nerve Paralysis, also called Bell’s Palsy or Facial Palsy. Bell’s Palsy, which is thought to occur due to a viral reactivation which can lead (through unknown mechanisms) to diffuse axon demyelination and degeneration of the seventh cranial nerve, results in a hemifacial paralysis due to non-functionality of the nerve. As the nerve attempts to recover, nerve miswiring results (see Mechanism of Action below). In patients with severe facial nerve paralysis, facial synkinesis will inevitably develop.

Additionally, a common treatment option for facial palsy is to use electrical stimulation. Unfortunately, this has been shown to be disruptive to normal re-innervation and can promote the development of synkinesis.

The most common symptoms of facial synkinesis include:

- Eye closure with volitional contraction of mouth muscles

- Midfacial movements with volitional eye closure

- Neck tightness (Platysmal contraction) with volitional smiling

- Hyperlacrimation(also called Crocodile Tears)

- A case where eating provokes excessive lacrimation. This has been attributed to neural interaction between the salivary glands and the lacrimal glands.

Many patients report that temperature may affect the severity of symptoms, especially cold as being an aggravating factor. However, there is some scientific debate on this subject, and some even report that cold may alleviate symptoms.

Almost all cases of synkinesis develop as a sequel to nerve trauma (the exception is when it is congenitally acquired as in Duane-Retraction Syndrome and Marcus Gunn phenomenon). Trauma to the nerve can be induced in cases such as surgical procedures, nerve inflammation, neuroma

, and physical injury.

Developmental coordination disorder (DCD), also known as developmental dyspraxia or simply dyspraxia, is a chronic neurological disorder beginning in childhood. It is also known to affect planning of movements and co-ordination as a result of brain messages not being accurately transmitted to the body. Impairments in skilled motor movements per a child's chronological age which must interfere with activities of daily living. A diagnosis of DCD is then reached only in the absence of other neurological impairments like cerebral palsy, muscular dystrophy, multiple sclerosis or Parkinson's disease. According to CanChild in Canada, this disorder affects 5 to 6 percent of school-aged children; however this disorder does progress towards adulthood, therefore making it a lifelong condition.

Developmental coordination disorder is classified (by doctors) in the fifth revision of the "Diagnostic and Statistical Manual of Mental Disorders" (DSM-5) as a motor disorder, in the category of neurodevelopmental disorders.

Symptoms vary according to the kind of dystonia involved. In most cases, dystonia tends to lead to abnormal posturing, in particular on movement. Many sufferers have continuous pain, cramping, and relentless muscle spasms due to involuntary muscle movements. Other motor symptoms are possible including lip smacking.

Early symptoms may include loss of precision muscle coordination (sometimes first manifested in declining penmanship, frequent small injuries to the hands, and dropped items), cramping pain with sustained use, and trembling. Significant muscle pain and cramping may result from very minor exertions like holding a book and turning pages. It may become difficult to find a comfortable position for arms and legs with even the minor exertions associated with holding arms crossed causing significant pain similar to restless leg syndrome. Affected persons may notice trembling in the diaphragm while breathing, or the need to place hands in pockets, under legs while sitting or under pillows while sleeping to keep them still and to reduce pain. Trembling in the jaw may be felt and heard while lying down, and the constant movement to avoid pain may result in the grinding and wearing down of teeth, or symptoms similar to temporomandibular joint disorder. The voice may crack frequently or become harsh, triggering frequent throat clearing. Swallowing can become difficult and accompanied by painful cramping.

Electrical sensors (EMG) inserted into affected muscle groups, while painful, can provide a definitive diagnosis by showing pulsating nerve signals being transmitted to the muscles even when they are at rest. The brain appears to signal portions of fibers within the affected muscle groups at a firing speed of about 10 Hz causing them to pulsate, tremble and contort. When called upon to perform an intentional activity, the muscles fatigue very quickly and some portions of the muscle groups do not respond (causing weakness) while other portions over-respond or become rigid (causing micro-tears under load). The symptoms worsen significantly with use, especially in the case of focal dystonia, and a "mirror effect" is often observed in other body parts: Use of the right hand may cause pain and cramping in that hand as well as in the other hand and legs that were not being used. Stress, anxiety, lack of sleep, sustained use and cold temperatures can worsen symptoms.

Direct symptoms may be accompanied by secondary effects of the continuous muscle and brain activity, including disturbed sleep patterns, exhaustion, mood swings, mental stress, difficulty concentrating, blurred vision, digestive problems, and short temper. People with dystonia may also become depressed and find great difficulty adapting their activities and livelihood to a progressing disability. Side-effects from treatment and medications can also present challenges in normal activities.

In some cases, symptoms may progress and then plateau for years, or stop progressing entirely. The progression may be delayed by treatment or adaptive lifestyle changes, while forced continued use may make symptoms progress more rapidly. In others, the symptoms may progress to total disability, making some of the more risky forms of treatment worth considering. In some cases with patients who already have dystonia, a subsequent tramatic injury or the effects of general anethesia during an unrelated surgery can cause the symptoms to progress rapidly.

An accurate diagnosis may be difficult because of the way the disorder manifests itself. Sufferers may be diagnosed as having similar and perhaps related disorders including Parkinson's disease, essential tremor, carpal tunnel syndrome, TMD, Tourette's syndrome, conversion disorder or other neuromuscular movement disorders. It has been found that the prevalence of dystonia is high in individuals with Huntington's disease, where the most common clinical presentations are internal shoulder rotation, sustained fist clenching, knee flexion, and foot inversion. Risk factors for increased dystonia in patients with Huntington's disease include long disease duration and use of antidopaminergic medication.

Segmental dystonias affect two adjoining parts of the body:

- Hemidystonia affects an arm and foot on one side of the body.

- Multifocal dystonia affects many different parts of the body.

- Generalized dystonia affects most of the body, frequently involving the legs and back.

This is characterized by hand and arm abnormalities. The following are specific characteristics:

- Malformed or absent (aplasia) thumb

- A thumb that looks more like a finger

- Partial or complete absence of a radius

- Shortening and radial deviation of the forearms

- Triphalangeal thumb

- Duplication of the thumb (preaxial polydactyly)

Also known as Duane syndrome, Duane anomaly is a congenital strabismus syndrome that is characterized by certain eye movements. This results from improper nerve development for eye movement.

The following are characteristics of Duane anomaly:

- Inability to fully abduct (away from the midline) the eye either unilaterally or bilaterally

- Narrowing of the palpebral fissure

- Retraction of the globe on adduction (toward the midline)

- Absence of the abducens nucleus and nerve (cranial nerve VI)

- Abnormal eye movement due to the lateral rectus muscle being innervated by a branch of the oculomotor nerve (cranial nerve III)

Stereotypic movement disorder (SMD) is a motor disorder with onset in childhood involving repetitive, nonfunctional motor behavior (e.g., hand waving or head banging), that markedly interferes with normal activities or results in bodily injury. The behavior must not be due to the direct effects of a substance or another medical condition. The cause of this disorder is not known.

Other conditions which feature repetitive behaviors in the differential diagnosis include autism spectrum disorders, obsessive–compulsive disorder, tic disorders (e.g., Tourette syndrome), and other conditions including dyskinesias.

Stereotypic movement disorder is often misdiagnosed as tics or Tourette syndrome (TS). Unlike the tics of TS, which tend to appear around age six or seven, repetitive movements typically start before age three, are more bilateral than tics, and consist of intense patterns of movement for longer runs than tics. Tics are less likely to be stimulated by excitement. Children with stereotypic movement disorder do not always report being bothered by the movements as a child with tics might.

In some children without “classic” holoprosencephaly, microforms of holoprosencephaly may be noted on MRI, including missing olfactory tracts and bulbs and absent or hypoplastic corpus callosum.

Children with 18p- have an increased incidence of ear infections, often requiring the placement of PE tubes.

Although the cause of writer's cramp is not well known, it was historically believed to be the result of excessive fine motor activity, possibly complicated by a tense or otherwise inappropriate writing technique. More recently, Karin Rosenkranz et al. have suggested that this is not necessarily the case. Musician's cramp (a similar focal dystonia which affects some 1% of instrumentalists) has historically been grouped together with writer's cramp because of this and their common task-specificity. Rosenkranz et al. have more recently identified significant differences between the two populations, however. No matter exactly how it arises, researchers generally agree that these types of focal dystonia are the result of a basal ganglia and/or sensorimotor cortex malfunction in the brain.

Early symptoms may include loss of precision muscle coordination (sometimes first manifested in declining penmanship, frequent small injuries to the hands, dropped items and a noticeable increase in dropped or chipped dishes), cramping pain with sustained use and trembling. Significant muscle pain and cramping may result from very minor exertions like holding a book and turning pages. It may become difficult to find a comfortable position for arms and legs with even the minor exertions associated with holding arms crossed causing significant pain similar to restless leg syndrome. Affected persons may notice trembling in the diaphragm while breathing, or the need to place hands in pockets, under legs while sitting or under pillows while sleeping to keep them still and to reduce pain. Trembling in the jaw may be felt and heard while lying down, and the constant movement to avoid pain may result in the grinding and wearing down of teeth, or symptoms similar to TMD. The voice may crack frequently or become harsh, triggering frequent throat clearing. Swallowing can become difficult and accompanied by painful cramping. Patients may also present with varying degree of disability and symptoms, such as experiencing more difficulty writing down-stroke as compared to writing upstroke.

Electrical sensors (EMG) inserted into affected muscle groups, while painful, can provide a definitive diagnosis by showing pulsating nerve signals being transmitted to the muscles even when they are at rest. The brain appears to signal portions of fibers within the affected muscle groups at a firing speed of about 10 Hz causing them to pulsate, tremble and contort. When called upon to perform an intentional activity, the muscles fatigue very quickly and some portions of the muscle groups do not respond (causing weakness) while other portions over-respond or become rigid (causing micro-tears under load). The symptoms worsen significantly with use, especially in the case of focal dystonia, and a "mirror effect" is often observed in other body parts: use of the right hand may cause pain and cramping in that hand as well as in the other hand and legs that were not being used. Stress, anxiety, lack of sleep, sustained use and cold temperatures can worsen symptoms.

Direct symptoms may be accompanied by secondary effects of the continuous muscle and brain activity, including disturbed sleep patterns, exhaustion, mood swings, mental stress, difficulty concentrating, blurred vision, digestive problems and short temper. People with dystonia may also become depressed and find great difficulty adapting their activities and livelihood to a progressing disability. Side effects from treatment and medications can also present challenges in normal activities.

In some cases, symptoms may progress and then plateau for years, or stop progressing entirely. The progression may be delayed by treatment or adaptive lifestyle changes, while forced continued use may make symptoms progress more rapidly. In others, the symptoms may progress to total disability, making some of the more risky forms of treatment worth considering in the future.

Step I : Decide the dominant type of movement disorder

Step II : Make differential diagnosis of the particular disorder

Step II: Confirm the diagnosis by lab tests

- Metabolic screening

- Microbiology

- Immunology

- CSF examination

- Genetics

- Imaging

- Neurophysiological tests

- Pharmacological tests

Writer's cramp, also called mogigraphia and scrivener's palsy, is a disorder caused by cramps or spasms of certain muscles of the hand and/or forearm, and presents itself while performing fine motor tasks, such as writing or playing an instrument. Writer's cramp is a task-specific focal dystonia of the hand. 'Focal' refers to the symptoms being limited to one location (the hand in this case), and 'task-specific' means that symptoms first occur only when the individual engages in a particular activity. Writer's cramp first affects an individual by interfering with their ability to write, especially for prolonged periods of time.

Congenital distal spinal muscular atrophy (congenital dSMA) is a hereditary genetic condition characterized by muscle wasting (atrophy), particularly of distal muscles in legs and hands, and by early-onset contractures (permanent shortening of a muscle or joint) of the hip, knee, and ankle. Affected individuals often have shorter lower limbs relative to the trunk and upper limbs. The condition is a result of a loss of anterior horn cells localized to lumbar and cervical regions of the spinal cord early in infancy, which in turn is caused by a mutation of the "TRPV4" gene. The disorder is inherited in an autosomal dominant manner. Arm muscle and function, as well as cardiac and respiratory functions are typically well preserved.