FLD produces rapidly progressive weakness of tongue, face and pharyngeal muscles in a clinical pattern similar to myasthenia. Neuromuscular transmission may be abnormal in these muscles because of rapid denervation and immature reinnervation. Paralysis occurs secondary to degeneration of the motor neurons of the brain stem. It causes progressive bulbar paralysis due to involvement of motor neurons of the cranial nerve nuclei. The most frequent symptoms at onset of progressive bulbar paralysis of childhood has been a unilateral facial paralysis. It is followed in frequency by dysarthria due to facial weakness or by dysphagia. Palatal weakness and palpebral ptosis also have been reported in few patients. Both sexes can be affected.

BVVL is marked by a number of cranial nerve palsies, including those of the motor components involving the 7th and 9th-12th cranial nerves, spinal motor nerves, and upper motor neurons. Major features of BVVL include facial and neck weakness, fasciculation of the tongue, and neurological disorders from the cranial nerves. The neurological manifestations develop insidiously: they usually begin with sensorineural deafness, progress inexorably to paralysis, and often culminate in respiratory failure. Most mortality in patients has been from either respiratory infections or respiratory muscle paralysis. Pathological descriptions of BVVL include injury and depletion of 3rd-7th cranial nerves, loss of the spinal anterior horn cells, degeneration of Purkinje cells, as well as degeneration of the spinocerebellar and pyramidal tracts. The first symptoms in nearly all cases of BVVL is progressive vision loss and deafness, and the first initial symptoms are seen anywhere from one to three years.

Most cases of deafness are followed by a latent period that can extend anywhere from weeks to years, and this time is usually marked by cranial nerve degeneration. Neurological symptoms of BVVL include optic atrophy, cerebellar ataxia, retinitis pigmentosa, epilepsy and autonomic dysfunction. Non-neurological symptoms can include diabetes, auditory hallucinations, respiratory difficulties, color blindness, and hypertension.

Onset of PLS usually occurs spontaneously after age 50 and progresses gradually over a number of years, or even decades. The disorder usually begins in the legs, but it may start in the tongue or the hands. Symptoms may include difficulty with balance, weakness and stiffness in the legs, and clumsiness. Other common symptoms are spasticity (involuntary muscle contraction due to the stretching of muscle, which depends on the velocity of the stretch) in the hands, feet, or legs, foot dragging, and speech and swallowing problems due to involvement of the facial muscles. Breathing may also become compromised in the later stages of the disease, causing those patients who develop ventilatory failure to require noninvasive ventilatory support. Hyperreflexia is another key feature of PLS as seen in patients presenting with the Babinski's sign. Some people present with emotional lability and bladder urgency, and occasionally people with PLS experience mild cognitive changes detectable on neuropsychological testing, particularly on measures of executive function.

PLS is not considered hereditary when onset is in adulthood; however, juvenile primary lateral sclerosis (JPLS) has been linked to a mutation in the ALS2 gene which encodes the cell-signalling protein alsin.

The issue of whether PLS exists as a different entity from ALS is not clear, as some patients initially diagnosed as having PLS ultimately develop lower motor neuron signs.

There are no specific tests for the diagnosis of PLS. Therefore, the diagnosis occurs as the result of eliminating other possible causes of the symptoms and by an extended observation period.

Fazio–Londe disease (FLD), also called progressive bulbar palsy of childhood, is a very rare inherited motor neuron disease of children and young adults and is characterized by progressive paralysis of muscles innervated by cranial nerves.

Primary lateral sclerosis (PLS) usually presents with gradual-onset, progressive, lower-extremity stiffness and pain due to muscle spasticity. Onset is often asymmetrical. Although the muscles do not appear to atrophy as in ALS (at least initially), the disabling aspect of PLS is muscle spasticity and cramping, and intense pain when those muscles are stretched, resulting in joint immobility. A normal walking stride may become a tiny step shuffle with related instability and falling.

The first sign of hemifacial spasm is typically muscle movement in the patient's eyelid and around the eye. It can vary in intensity. The intermittent twitching of the eyelid, which can result in forced closure of the eye which gradually spreads to the muscles of the lower part of the face (Typical form- See Image). In atypical form the spasms start in the cheekbone area and spreads to the eyelid. Ultimately, all the muscles on that side are affected, nearly all the time. This sometimes causes the mouth to be pulled to the side. Experts have linked hemifacial spasm to facial nerve injury, Bell's palsy and tumors. Although the most frequent cause is a blood vessel pressing on the facial nerve at the spot where it leaves the patient's brain stem, sometimes there is no known cause. When the affected individual is younger than 40, doctors suspect an underlying cause such as multiple sclerosis.

Hemifacial spasm (HFS) is a rare neuromuscular disease characterized by irregular, involuntary muscle contractions (spasms) on one side (hemi-) of the face (-facial). The facial muscles are controlled by the facial nerve (seventh cranial nerve), which originates at the brainstem and exits the skull below the ear where it separates into five main branches.

This disease takes two forms: typical and atypical. In typical form, the twitching usually starts in the lower eyelid in orbicularis oculi muscle. As time progresses, it spreads to the whole lid, then to the orbicularis oris muscle around the lips, and buccinator muscle in the cheekbone area. The reverse process of twitching occurs in atypical hemifacial spasm; twitching starts in orbicularis oris muscle around the lips, and buccinator muscle in the cheekbone area in the lower face, then progresses up to the orbicularis oculi muscle in the eyelid as time progresses. The most common form is the typical form, and atypical form is only seen in about 2–3% of patients with hemifacial spasm. The incidence of hemifacial spasm is approximately 0.8 per 100,000 persons.

This disorder occurs in both men and women, although it affects middle-aged or elderly women more frequently. Hemifacial spasm is much more common in some Asian populations. It may be caused by a facial nerve injury, a tumor, or it may have no apparent cause. Individuals with spasm on both sides of the face are very rare.

Brown-Vialetto-Van-Laere syndrome (BVVL), sometimes known as Brown's Syndrome, is a rare degenerative disorder often initially characterized by progressive sensorineural deafness.

The syndrome most often affects children, adolescents, and young adults. As knowledge of BVVL grows some adult patients have now been diagnosed. There is no known cure, however with prompt treatment the prognosis may be positive with some patients stabilizing and even minor improvements noted in certain cases.

Telangiectasias are widened blood vessels that can develop anywhere on the skin, mucous membranes, whites of the eyes, and even in the brain. Telangiectasias are associated with multiple systemic signs, the most serious of which are unusual sensitivity to ionizing radiation, excessive chromosomal breakage, and a deficiency in the immune system. Ataxia telangiectasia results from defects in the ataxia telangiectasia mutated gene, which can cause abnormal cell death in various places of the body, including brain areas related to coordinated movement of the eyes. Patients with ataxia telangiectasia have prolonged vertical and horizontal saccade latencies and hypometric saccades, and, although not all, some patients show head thrusts.

Even though OMA is not always associated with developmental issues, children with this condition often have hypotonia, decreased muscle tone, and show developmental delays. Some common delays are seen in speech, reading and motor development

Usually, the first respiratory symptoms are dyspnea and paradoxical respirations which then escalate within the first few months of life to diaphragmatic paralysis. The symptoms of diaphragmatic paralysis come on very rapidly and without warning, and the patient is often rushed to a hospital where they are placed on a ventilator for respiratory support. Due to the severe nature of diaphragmatic paralysis the patient eventually needs continuous ventilation support to survive. Continuous ventilation, however, may in itself cause damage to the anatomy of the lungs.

In addition to diaphragmatic paralysis other issues may arise: as the name suggests, the distal limbs are most affected with symptoms of weakness, restricting mobility due to (near-)paralysis of the distal limbs as well as the head and neck. Also, dysfunction of the peripheral nerves and the autonomic nervous system may occur. Due to these dysfunctions the patients have been shown to suffer from excessive sweating and irregular heartbeat. The deep tendon reflex is also lost in patients with DSMA1.

Uterine growth retardation and poor foetal movement have been observed in severe DSMA1 cases.

DSMA1 was identified and classified as a sub-group of spinal muscular atrophies (SMA) in 1974. Currently, various classifications include DSMA1 among general spinal muscular atrophies or distal hereditary motor neuropathies, though the latter has been argued to be more correct.

Facial nerve paralysis is characterised by unilateral facial weakness, with other symptoms including loss of taste, , and decreased salivation and tear secretion. Other signs may be linked to the cause of the paralysis, such as s in the ear, which may occur if the facial palsy is due to shingles. Symptoms may develop over several hours. Acute facial pain radiating from the ear may precede the onset of other symptoms.

Dysmetria () refers to a lack of coordination of movement typified by the undershoot or overshoot of intended position with the hand, arm, leg, or eye. It is a type of ataxia. It is sometimes described as an inability to judge distance or scale.

Hypermetria and hypometria refer, respectively, to overshooting and undershooting the intended position.

The bilateral form of FCMS ("also known as facio-labio-pharyngo-glosso-laryngo-brachial paralysis)" is consistent with the classic presentation of bilateral corticobulbar involvement. It is characterized by well-preserved automatic and reflex movements. It is caused by lesions in the cortical or subcortical region of the anterior opercular area surrounding the insula forming the gyri of the frontal, temporal, and parietal lobes.

An individual affected with FCMS develops disabilities associated with voluntary movements using the facial, lingual, pharyngeal, and masticatory muscles. However, the reflexive and autonomic functions of these muscles groups are usually intact. Common symptoms include drooling, an inability to elevate and depress the mandible, difficulty chewing, inability of protruding tongue, swallowing, and loss of speech.

Classification of the disorder is distinguished by the location of the lesions formed, which causes certain symptoms to be present or amplified. FCMS caused by the formation of bilateral lesions causes paralysis of the facial, lingual, pharyngeal, and masticatory muscles. This form of FCMS involves voluntary-autonomic dissociation and an inability to form speech. The formation of bilateral lesions confined to the posterior operculum has a distinct symptom of word deafness, an inability to understand language.

FCMS caused by the formation of lesions unilaterally causes muteness of speech and upper motor neuron cranial nerve paresis, muscular weakness. The formation of unilateral lesions confined to the posterior operculum has distinct symptoms that includes sensory loss in the hand and face contralateral to the location of the lesion.

Facial nerve paralysis is a common problem that involves the paralysis of any structures innervated by the facial nerve. The pathway of the facial nerve is long and relatively convoluted, and so there are a number of causes that may result in facial nerve paralysis. The most common is Bell's palsy, a disease of unknown cause that may only be diagnosed by exclusion.

Symptoms begin in infancy and include:

- hypotonia

- areflexia

- amyotrophy

- variable degrees of dysgenesis of the corpus callosum

- mild to severe intellectual and developmental delay

- psychiatric problems including paranoid delusions, depression, hallucinations and autistic-like behavior

Focal dystonia is a neurological condition, a type of "dystonia", that affects a muscle or group of muscles in a specific part of the body, causing involuntary muscular contractions and abnormal postures. For example, in focal hand dystonia, the fingers either curl into the palm or extend outward without control. In musicians, the condition is called "musician's focal dystonia", or simply, "musician's dystonia". In sports, it is commonly referred to as the "yips".

Initial facial changes usually involve the area of the face covered by the temporal or buccinator muscles. The disease progressively spreads from the initial location, resulting in atrophy of the skin and its adnexa, as well as underlying subcutaneous structures such as connective tissue, (fat, fascia, cartilage, bones) and/or muscles of one side of the face. The mouth and nose are typically deviated towards the affected side of the face.

The process may eventually extend to involve tissues between the nose and the upper corner of the lip, the upper jaw, the angle of the mouth, the area around the eye and brow, the ear, and/or the neck. The syndrome often begins with a circumscribed patch of scleroderma in the frontal region of the scalp which is associated with a loss of hair and the appearance of a depressed linear scar extending down through the midface on the affected side. This scar is referred to as a "coup de sabre" lesion because it resembles the scar of a wound made by a sabre, and is indistinguishable from the scar observed in frontal linear scleroderma.

In 20% of cases, the hair and skin overlying affected areas may become hyperpigmented or hypopigmented with patches of unpigmented skin. In up to 20% of cases the disease may involve the ipsilateral (on the same side) or contralateral (on the opposite side) neck, trunk, arm, or leg. The cartilage of the nose, ear and larynx can be involved. The disease has been reported to affect both sides of the face in 5-10% of the cases.

Symptoms and physical findings usually become apparent during the first or early during the second decade of life. The average age of onset is nine years of age, and the majority of individuals experience symptoms before 20 years of age. The disease may progress for several years before eventually going into remission (abruptly ceasing).

Neurological abnormalities are common. Roughly 45% of people with Parry–Romberg syndrome are also afflicted with trigeminal neuralgia (severe pain in the tissues supplied by the ipsilateral trigeminal nerve, including the forehead, eye, cheek, nose, mouth and jaw) and/or migraine (severe headaches that may be accompanied by visual abnormalities, nausea and vomiting).

10% of affected individuals develop a seizure disorder as part of the disease. The seizures are typically Jacksonian in nature (characterized by rapid spasms of a muscle group that subsequently spread to adjacent muscles) and occur on the side contralateral to the affected side of the face. Half of these cases are associated with abnormalities in both the gray and white matter of the brain—usually ipsilateral but sometimes contralateral—that are detectable on magnetic resonance imaging (MRI) scan.

The actual cause of dysmetria is thought to be caused by lesions in the cerebellum or by lesions in the proprioceptive nerves that lead to the cerebellum that coordinate visual, spatial and other sensory information with motor control. Damage to the proprioceptive nerves does not allow the cerebellum to accurately judge where the hand, arm, leg, or eye should move. These lesions are often caused by strokes, multiple sclerosis (MS), amyotrophic lateral sclerosis (ALS), or tumors.

According to the research article cited above, motor control is a learning process that utilizes APPGs. Disruption of APPGs is possibly the cause of ataxia and dysmetria and upon identification of the motor primitives, clinicians may be able to isolate the specific areas responsible for the cerebellar problems.

There are two types of cerebellar disorders that produce dysmetria, specifically midline cerebellar syndromes and hemispheric cerebellar syndromes. Midline cerebellar syndromes can cause ocular dysmetria, which is a condition in which the pupils of the eye overshoot. Ocular dysmetria makes it difficult to focus vision onto one object. Hemispheric cerebellar syndromes cause dysmetria in the typical motor sense that many think of when hearing the term dysmetria.

A common motor syndrome that causes dysmetria is cerebellar motor syndrome, which also marked by impairments in gait (also known as ataxia), disordered eye movements, tremor, difficulty swallowing and poor articulation. As stated above, cerebellar cognitive affective syndrome (CCAS) also causes dysmetria.

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.

Andermann syndrome also known as agenesis of corpus callosum with neuronopathy (ACCPN), Charlevoix disease among others is a very rare neurodegenerative genetic disorder that damages the nerves used to control muscles and related to sensation, and is often associated with agenesis of the corpus collosum.

It was first described by Eva Andermann et al. in 1972.