The muscle spasticity can cause gait patterns to be awkward and jerky. The constant spastic state of the muscle can lead to bone and tendon deformation, further complicating the patient's mobility. Many patients with spastic hemiplegia are subjected to canes, walkers and even wheelchairs. Due to the decrease in weight bearing, patients are at a higher risk of developing osteoporosis. An unhealthy weight can further complicate mobility. Patients with spastic hemiplegia are a high risk for experiencing seizures. Oromotor dysfunction puts patients at risk for aspiration pneumonia. Visual field deficits can cause impaired two-point discrimination. Many patients experience the loss of sensation in the arms and legs on the affected side of the body. Nutrition is essential for the proper growth and development for a child with spastic hemiplegia.

The prognosis for those with spastic muscles depends on multiple factors, including the severity of the spasticity and the associated movement disorder, access to specialised and intensive management, and ability of the affected individual to maintain the management plan (particularly an exercise program). Most people with a significant UMN lesion will have ongoing impairment, but most of these will be able to make progress. The most important factor to indicate ability to progress is seeing improvement, but improvement in many spastic movement disorders may not be seen until the affected individual receives help from a specialised team or health professional.

Doublecortin positive cells, Similar to stem cells, are extremely adaptable and, when extracted from a brain, cultured and then re-injected in a lesioned area of the same brain, they can help repair and rebuild it. The treatment using them would take some time to be available for general public use, as it has to clear regulations and trials.

Although HSP is a progressive condition, the prognosis for individuals with HSP varies greatly. It primarily affects the legs although there can be some upperbody involvement in some individuals. Some cases are seriously disabling while others are less disabling and are compatible with a productive and full life. The majority of individuals with HSP have a normal life expectancy.

In some cases, spastic cerebral palsy is caused by genetic factors.

The genetic factors for spastic cerebral palsy include:

Although it has its origins in a brain injury, spastic CP can largely be thought of as a collection of orthopaedic and neuromuscular issues because of how it manifests symptomatically over the course of the person's lifespan. It is therefore not the same as "brain damage" and it need not be thought of as such. Spastic quadriplegia in particular, especially if it is combined with verbal speech challenges and strabismus, may be misinterpreted by the general population as alluding to cognitive dimensions to the disability atop the physical ones, but this is false; the intelligence of a person with any type of spastic CP is unaffected by the condition "of the spasticity itself".

In spastic cerebral palsy in children with low birth weights, 25% of children had hemiplegia, 37.5% had quadriplegia, and 37.5% had diplegia.

The incidence of cerebral palsy has increased in the past 40 years. It has been estimated that in the United States cerebral palsy occurs in 4 out every 1000 births. Of these births about 20–30% of them have spastic hemiplegia. Spasticity overall, is the more common type of cerebral palsy, whereas as non-spastic cerebral palsy is less common. Studies show that spastic type cerebral palsy is on the rise, and the occurrence of diplegia type is decreasing. The prevalence of cerebral palsy is higher in areas of low socioeconomic status. This could potentially be because cerebral palsy incidence increases as birth weight decreases.

Upper limb paralysis refers to the loss of function of the elbow and hand. When upper limb function is absent as a result of a spinal cord injury it is a major barrier to regain autonomy. People with tetraplegia should be examined and informed concerning the options for reconstructive surgery of the tetraplegic arms and hands.

In the industrialized world, the incidence of overall cerebral palsy, which includes but is not limited to spastic diplegia, is about 2 per 1000 live births. Thus far, there is no known study recording the incidence of CP in the overall nonindustrialized world. Therefore, it is safe to assume that not all spastic CP individuals are known to science and medicine, especially in areas of the world where healthcare systems are less advanced. Many such individuals may simply live out their lives in their local communities without any medical or orthopedic oversight at all, or with extremely minimal such treatment, so that they are never able to be incorporated into any empirical data that orthopedic surgeons or neurosurgeons might seek to collect. It is shocking to note that—as with people with physical disability overall—some may even find themselves in situations of institutionalization, and thus barely see the outside world at all.

From what "is" known, the incidence of spastic diplegia is higher in males than in females; the Surveillance of Cerebral Palsy in Europe (SCPE), for example, reports a M:F ratio of 1.33:1. Variances in reported rates of incidence across different geographical areas in industrialized countries are thought to be caused primarily by discrepancies in the criteria used for inclusion and exclusion.

When such discrepancies are taken into account in comparing two or more registers of patients with cerebral palsy and also the extent to which children with mild cerebral palsy are included, the incidence rates still converge toward the average rate of 2:1000.

In the United States, approximately 10,000 infants and babies are born with CP each year, and 1200–1500 are diagnosed at preschool age when symptoms become more obvious. It is interesting to note that those with extremely mild spastic CP may not even be aware of their condition until much later in life: Internet chat forums have recorded men and women as old as 30 who were diagnosed only recently with their spastic CP.

Overall, advances in care of pregnant mothers and their babies has not resulted in a noticeable decrease in CP; in fact, because medical advances in areas related to the care of premature babies has resulted in a greater survival rate in recent years, it is actually "more" likely for infants with cerebral palsy to be born into the world now than it would have been in the past. Only the introduction of quality medical care to locations with less-than-adequate medical care has shown any decreases in the incidences of CP; the rest either have shown no change or have actually shown an increase. The incidence of CP increases with premature or very low-weight babies regardless of the quality of care.

Spastic quadriplegia is generally caused by brain damage or disruptions in normal brain development preceding birth. According to the National Institutes of Health, there are four types of brain damage that can cause spastic quadriplegia. These include, damage to the white matter (periventricular leukomalacia), abnormal brain development (cerebral dysgenesis), bleeding in the brain (intracranial hemorrhage), and brain damage due to lack of oxygen (hypoxic-ischemic encephalopathy or intrapartum asphyxia).

The white matter of the brain is especially vulnerable between the 26th and 34th weeks of maturation, and damage to the white matter can interfere with the brain’s ability to transmit signals to the rest of the body. Spastic quadriplegia can be caused by a condition known as periventricular leukomalacia which results in the formation of lesions and holes in the white matter of the brain.

Prior to the 26th week of maturation, the fetal brain is particularly susceptible to various toxins whose effects can ultimately hinder normal development. Exposure of the brain to infectious agents is especially dangerous because they can trigger immune responses that activate cytokines and lead to inflammation of the brain. Some infections that have been linked to the development of spastic quadriplegia include meningitis, herpes, rubella, and encephalitis. A difference in blood types between the mother and the fetus can also initiate a problematic immune response and cause brain damage. Severe jaundice, can also lead to brain damage and spastic quadriplegia due to a buildup of bilirubin in the blood.

Bleeding in the brain caused by fetal strokes, blood clots, weak and malformed blood vessels, or high maternal blood pressure may also lead to brain damage causing spastic quadriplegia. Maternal infection, most specifically pelvic inflammatory disease, has been shown to increase the risk of fetal stroke.

Hypoxia, lack of oxygen to the brain, can also cause damage in the cerebral motor cortex and other brain regions. This lack of oxygen can be the result of placenta malfunction, womb rupture, umbilical cord damage, low maternal blood pressure or asphyxia during labor and delivery.

Children who experienced many complications during birth, such as, prematurity, insufficient oxygen, low birthweight, aspiration, head injury, or bleeding in the brain have a greater risk of developing spastic quadriplegia. Children whose mothers were ill during the pregnancy or did not receive adequate nutrition are also more likely to develop the disease.

The severity of impairment and related prognosis is dependent on the location and severity of brain lesions. Up to 50% of patients will achieve some degree of ambulation. Speech problems, such as dysarthria, are common to these patients.

Worldwide, the prevalence of all hereditary spastic paraplegias combined is estimated to be 2 to 6 in 100,000 people. A Norwegian study of more than 2.5 million people published in March 2009 has found an HSP prevalence rate of 7.4/100,000 of population – a higher rate, but in the same range as previous studies. No differences in rate relating to gender were found, and average age at onset was 24 years. In the United States, Hereditary Spastic Paraplegia is listed as a "rare disease" by the Office of Rare Diseases (ORD) of the National Institutes of Health which means that the disorder affects less than 200,000 people in the US population.

Delayed diagnosis of cervical spine injury has grave consequences for the victim. About one in 20 cervical fractures are missed and about two-thirds of these patients have further spinal-cord damage as a result. About 30% of cases of delayed diagnosis of cervical spine injury develop permanent neurological deficits. In high-level cervical injuries, total paralysis from the neck can result. High-level tetraplegics (C4 and higher) will likely need constant care and assistance in activities of daily living, such as getting dressed, eating and bowel and bladder care. Low-level tetraplegics (C5 to C7) can often live independently.

Even with "complete" injuries, in some rare cases, through intensive rehabilitation, slight movement can be regained through "rewiring" neural connections, as in the case of the late actor Christopher Reeve.

In the case of cerebral palsy, which is caused by damage to the motor cortex either before, during (10%), or after birth, some people with tetraplegia are gradually able to learn to stand or walk through physical therapy.

Quadriplegics can improve muscle strength by performing resistance training at least three times per week. Combining resistance training with proper nutrition intake can greatly reduce co-morbidities such as obesity and type 2 diabetes.

Spastic diplegia's particular type of brain damage inhibits the proper development of upper motor neuron function, impacting the motor cortex, the basal ganglia and the corticospinal tract. Nerve receptors in the spine leading to affected muscles become unable to properly absorb gamma amino butyric acid (GABA), the amino acid that regulates muscle tone in humans. Without GABA absorption to those particular nerve rootlets (usually centred, in this case, around the sectors L1-S1 and L2-S2), affected nerves (here, the ones controlling the legs) perpetually fire the message for their corresponding muscles to permanently, rigidly contract, and the muscles become permanently hypertonic (spastic).

The abnormally high muscle tone that results creates lifelong difficulty with all voluntary and passive movement in the legs, and in general creates stress over time—depending on the severity of the condition in the individual, the constant spasticity ultimately produces pain, muscle/joint breakdown including tendinitis and arthritis, premature physical exhaustion (i.e., becoming physically exhausted even when you internally know that you have more energy than you are able to use), contractures, spasms, and progressively worse deformities/mis-alignments of bone structure around areas of the tightened musculature as the person's years progress. Severe arthritis, tendinitis, and similar breakdown can start as early as the spastic diplegic person's mid-20s (as a comparison, typical people with normal muscle tone are not at risk of arthritis, tendinitis, and similar breakdown until well into their 50s or 60s, if even then).

No type of CP is officially a progressive condition, and indeed spastic diplegia does not clinically "get worse" given the nerves, damaged permanently at birth, neither recover nor degrade. This aspect is clinically significant because other neuromuscular conditions with similar surface characteristics in their presentations, like most forms of multiple sclerosis, indeed do degrade the body over time and do involve actual progressive worsening of the condition, including the spasticity often seen in MS. However, spastic diplegia is indeed a chronic condition; the symptoms themselves cause compounded effects on the body that are typically just as stressful on the human body as a progressive condition is. Despite this reality and the fact that muscle tightness is the symptom of spastic diplegia and not the cause, symptoms rather than cause are typically seen as the primary area of focus for treatment, especially surgical treatment, except when a selective dorsal rhizotomy is brought into consideration, or when an oral baclofen regimen is attempted.

Unlike any other condition that may present with similar effects, spastic diplegia is entirely congenital in origin—that is, it is almost always acquired shortly before or during a baby's birth process. Things like exposure to toxins, traumatic brain injury, encephalitis, meningitis, drowning, or suffocation do not tend to lead to spastic diplegia in particular or even cerebral palsy generally. Overall, the most common cause of spastic diplegia is Periventricular leukomalacia, more commonly known as neonatal asphyxia or infant hypoxia—a sudden in-womb shortage of oxygen-delivery through the umbilical cord. This sudden lack of oxygen is also almost always combined with premature birth, a phenomenon that, even by itself, would inherently risk the infant developing some type of CP. On the other hand, the presence of certain maternal infections during pregnancy such as congenital rubella syndrome can also lead to spastic diplegia, since such infections can have similar end results to infant hypoxia.

Patients can often live with PLS for many years and very often outlive their neurological disease and succumb to some unrelated condition. There is currently no effective cure, and the progression of symptoms varies. Some people may retain the ability to walk without assistance, but others eventually require wheelchairs, canes, or other assistive devices.

In any manifestation of spastic CP, clonus of the affected limb(s) may intermittently result, as well as muscle spasms, each of which results from the pain and/or stress of the tightness experienced, indicating especially hard-working and/or exhausted musculature. The spasticity itself can and usually does also lead to very early onset of muscle-stress symptoms like arthritis and tendinitis, especially in ambulatory individuals in their mid-20s and early-30s. As compared to other types of CP, however, and especially as compared to hypotonic CP or more general paralytic mobility disabilities, spastic CP is typically more easily manageable by the person affected, and medical treatment can be pursued on a multitude of orthopaedic and neurological fronts throughout life.

Physical therapy and occupational therapy regimens of assisted stretching, strengthening, functional tasks, and/or targeted physical activity and exercise are usually the chief ways to keep spastic CP well-managed, although if the spasticity is too much for the person to handle, other remedies may be considered, such as various antispasmodic medications, botox, baclofen, or even a neurosurgery known as a selective dorsal rhizotomy (which eliminates the spasticity by eliminating the nerves causing it).

Most common causes of lower motor neuron injuries are trauma to peripheral nerves that serve the axons – a virus that selectively attacks ventral horn cells.

Disuse atrophy of the muscle occurs i.e., shrinkage of muscle fibre finally replaced by fibrous tissue (fibrous muscle)

Other causes include Guillain–Barré syndrome, "C. botulism", polio, and cauda equina syndrome; another common cause of lower motor neuron degeneration is amyotrophic lateral sclerosis.

CP in general is a non-progressive, neurological condition that results from brain injury and malformation occurring before cerebral development is complete. ADCP is associated with injury and malformations to the extrapyramidal tracts in the basal ganglia or the cerebellum. Lesions to this region principally arise via hypoxic ischemic brain injury (HIBI) or bilirubin encephalopathy.

Spastic quadriplegia, also known as spastic tetraplegia, is a subset of spastic cerebral palsy that affects all four limbs (both arms and legs).

Compared to quadriplegia, spastic tetraplegia is defined by spasticity of the limbs as opposed to strict paralysis. It is distinguishable from other forms of cerebral palsy in that those afflicted with the condition display stiff, jerky movements stemming from hypertonia of the muscles.

Spastic quadriplegia, while affecting all four limbs more or less equally, can still present parts of the body as stiffer than others, such as one arm being tighter than another arm, and so forth. Spastic triplegia, meanwhile, involves three limbs (such as one arm and two legs, or one leg and two arms, etc.); spastic diplegia affects two limbs (commonly just the legs), spastic hemiplegia affects one or another entire side of the body (left or right); and spastic monoplegia involves a single limb.

Researchers do not fully understand what causes PLS, although it is thought it could be due to a combination of environmental and genetic factors. Studies are being done to evaluate the possible causes, although linking causality can be difficult due to the relatively low number of people who are diagnosed with PLS.

Juvenile PLS may be caused by the ALS2 gene, although this condition is very rare.

Recovery of hyperreflexia can occur between several hours to several months after a spinal cord injury; however, the phase of recovery is likely to occur in stages rather than on a continuum. The late stage can be defined as between two weeks and several months. Individuals with a severe spinal cord injury (SCI) mainly present with a later stage of recovery because during the early stages they present with spinal shock. Reflex and motor recovery can sometimes return simultaneously.

Individuals with paraplegia can range in their level of disability, requiring treatments to vary from case to case. From a rehabilitation standpoint, the most important factor is to gain as much functionality and independence back as possible. Physiotherapists spend many hours within a rehabilitation setting working on strength, range of motion/stretching and transfer skills. Wheelchair mobility is also an important skill to learn. Most paraplegics will be dependent on a wheelchair as a mode of transportation. Thus it is extremely important to teach them the basic skills to gain their independence. Activities of daily living (ADLs) can be quite challenging at first for those with a spinal cord injury (SCI). With the aid of physiotherapists and occupational therapists, individuals with an SCI can learn new skills and adapt previous ones to maximize independence, often living independently within the community.

Recent research indicates that the biomolecule taurine may be effective for hypertonia, perhaps through its benzodiazepine-like modulation of the inhibitory neurotransmitter GABA or the neuromuscular effects of increasing intracellular calcium levels.

A lower motor neuron lesion is a lesion which affects nerve fibers traveling from the ventral horn or anterior grey column of the spinal cord to the relevant muscle(s) – the lower motor neuron.

One major characteristic used to identify a lower motor neuron lesion is flaccid paralysis – paralysis accompanied by loss of muscle tone. This is in contrast to an upper motor neuron lesion, which often presents with spastic paralysis – paralysis accompanied by severe hypertonia.

Pseudobulbar palsy is the result of damage of motor fibers traveling from the cerebral cortex to the lower brain stem. This damage might arise in the course of a variety of neurological conditions that involve demyelination and bilateral corticobulbar lesions. Examples include:

- Vascular causes: bilateral hemisphere infarction, CADASIL syndrome

- Progressive supranuclear palsy

- Amyotrophic lateral sclerosis

- Parkinson's disease and related multiple system atrophy

- Various motor neuron diseases, especially those involving demyelination

- Multiple sclerosis and other inflammatory disorders

- High brain stem tumors

- Metabolic causes: osmotic demyelination syndrome

- Neurological involvement in Behçet's disease

- Brain trauma

Baclofen, diazepam and dantrolene remain the three most commonly used pharmacologic agents in the treatment of spastic hypertonia. Baclofen is generally the drug of choice for spinal cord types of spasticity, while sodium dantrolene is the only agent which acts directly on muscle tissue. Tizanidine is also available. Phenytoin with chlorpromazine may be potentially useful if sedation does not limit their use. Ketazolam, not yet available in the United States, may be a significant addition to the pharmacologic armamentarium. Intrathecal administration of antispastic medications allows for high concentrations of drug near the site of action, which limits side effects.