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.

HSP is a group of genetic disorders. It follows general inheritance rules and can be inherited in an autosomal dominant, autosomal recessive or X-linked recessive manner. The mode of inheritance involved has a direct impact on the chances of inheriting the disorder. Over 70 genotypes had been described, and over 50 genetic loci have been linked to this condition. Ten genes have been identified with autosomal dominant inheritance. One of these SPG4 accounts for ~50% of all genetically solved cases cases, or approximately 25% of all HSP cases. Twelve genes are known to be inherited in an autosomal recessive fashion. Collectively this latter group account for ~1/3 cases.

Most altered genes have known function, but for some the function haven’t been identified yet. All of them are listed in the gene list below, including their mode of inheritance. Some examples are spastin (SPG4) and paraplegin (SPG7) are both AAA ATPases.

The inheritance pattern is autosomal recessive. The disorder is caused by a mutation in the SGCG on chromosome 13. The mutation of the SACS gene causes the production of an unstable, poorly functioning SACSIN protein. It is unclear as to how this mutation affects the central nervous system (CNS) and skeletal muscles presenting in the signs and symptoms of ARSACS.

In most cases, between the age of 2 and 4 oculomotor signals are present. Between the age of 2 and 8, telangiectasias appears. Usually by the age of 10 the child needs a wheel chair. Individuals with autosomal recessive cerebellum ataxia usually survive till their 20s; in some cases individuals have survived till their 40s or 50s.

Most patients begin to use a wheelchair for movement around age 30-40. Death usually occurs in their 60s, but some have been reported to live longer.

40 cases were diagnosed in northern Italy between 1940 and 1990. The gene frequency for this autosomal recessive condition was estimated at 1 in 218. In 1989, 16 cases on EOCA were diagnosed in children with a mean onset age of 7.1 In 1990, 20 patients affected by EOCA were studied. It was found that the ataxia of this study's participants affected the pyramidal tracts and peripheral nerves.

In terms of frequency, is estimated at 2 per 100,000, it has identified in different regions of the world. Some clusters of certain types of autosomal dominant cerebellar ataxia reach a prevalence of 5 per 100,000.

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.

NPCA is a syndrome and can have diverse causes. It has a genetic basis and inheritance is considered to be autosomal recessive. However, autosomal dominant variety has also been reported. There may be familial balanced translocation t(8;20)(p22;q13) involved.

Harding ataxia, also known as Early onset cerebellar ataxia with retained reflexes (EOCARR), is an autosomal recessive cerebellar ataxia originally described by Harding in 1981. This form of cerebellar ataxia is similar to Friedreich ataxia including that it results in poor reflexes and balance, but differs in several ways, including the absence of diabetes mellitus, optic atrophy, cardiomyopathy, skeletal abnormalities, and the fact that tendon reflexes in the arms and knees remain intact. This form of ataxia is characterized by onset in the first 20 years, and is less severe than Friedreich ataxia. Additional cases were diagnosed in 1989, 1990, 1991, and 1998.

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.

The treatment of 2-Hydroxyglutaric aciduria is based on seizure control, the prognosis depends on how severe the condition is.

Costeff syndrome, or 3-methylglutaconic aciduria type III, is a genetic disorder caused by mutations in the "OPA3" gene. It is typically associated with the onset of visual deterioration (optic atrophy) in early childhood followed by the development of movement problems and motor disability in later childhood, occasionally along with mild cases of cognitive deficiency. The disorder is named after Hanan Costeff, the doctor who first described the syndrome in 1989.

Non-progressive congenital ataxia (NPCA) is a non-progressive form of cerebellar ataxia which can occur with or without cerebellar hypoplasia.

The prognosis is very poor. Two studies reported typical age of deaths in infancy or early childhood, with the first reporting a median age of death of 2.6 for boys and less than 1 month for girls.

Infantile neuroaxonal dystrophy is a rare pervasive developmental disorder that primarily affects the nervous system. Individuals with infantile neuroaxonal dystrophy typically do not have any symptoms at birth, but between the ages of about 6 and 18 months they begin to experience delays in acquiring new motor and intellectual skills, such as crawling or beginning to speak. Eventually they lose previously acquired skills.

Behr syndrome is characterized by the association of early-onset optic atrophy with spinocerebellar degeneration resulting in ataxia, pyramidal signs, peripheral neuropathy and developmental delay.

Although it is an autosomal recessive disorder, heterozygotes may still manifest much attenuated symptoms. Autosomal dominant inheritance also being reported in a family. Recently a variant of OPA1 mutation with phenotypic presentation like Behr syndrome is also described. Some reported cases have been found to carry mutations in the OPA1, OPA3 or C12ORF65 genes which are known causes of pure optic atrophy or optic atrophy complicated by movement disorder.

2-hydroxyglutaric aciduria is a rare neurometabolic disorder characterized by the significantly elevated levels of hydroxyglutaric acid in ones urine. It is either autosomal recessive or autosomal dominant.

Dejerine–Sottas disease, also known as Dejerine–Sottas syndrome, Dejerine–Sottas neuropathy, progressive hypertrophic interstitial polyneuropathy of childhood and onion bulb neuropathy (and, "hereditary motor and sensory polyneuropathy type III" and "Charcot–Marie–Tooth disease type 3"), is a hereditary neurological disorder characterised by damage to the peripheral nerves and resulting progressive muscle wasting. The condition is caused by mutations in a various genes and currently has no known cure.

The disorder is named for Joseph Jules Dejerine and Jules Sottas, French neurologists who first described it.

The prevalence of SCA6 varies by culture. In Germany, SCA6 accounts for 10-25% of all autosomal dominant cases of SCA (SCA itself having a prevalence of 1 in 100,000). This prevalence in lower in Japan, however, where SCA6 accounts for only ~6% of spinocerebellar ataxias. In Australia, SCA6 accounts for 30% of spinocerebellar ataxia cases while 11% in the Dutch.

This condition is inherited in an autosomal recessive pattern, which means two copies of the gene ("PLA2G6") in each cell are altered. Most often, the parents of an individual with an autosomal recessive disorder each carry one copy of the altered gene but do not show signs and symptoms of the disorder.

The long-term prognosis of Costeff syndrome is unknown, though it appears to have no effect on life expectancy at least up to the fourth decade of life. However, as mentioned previously, movement problems can often be severe enough to confine individuals to a wheelchair at an early age, and both visual acuity and spasticity tend to worsen over time.

The prognosis of this developmental disorder is highly based on the underlying disorder. Cerebellar hypoplasia may be progressive or static in nature. Some cerebellar hypoplasia resulting from congenital brain abnormalities/malformations are not progressive. Progressive cerebellar hypoplasia is known for having poor prognosis, but in cases where this disorder is static, prognosis is better.

Dejerine–Sottas neuropathy is caused by a genetic defect either in the proteins found in axons or the proteins found in myelin. Specifically, it has been associated with mutations in "MPZ", "PMP22", "PRX", and "EGR2" genes. The disorder is inherited in an autosomal dominant or autosomal recessive manner.

Onset : Early childhood

Progression: Chronic progressive

Clinical: Cerebellar ataxia plus syndrome / Optic Atrophy Plus Syndrome

Ocular: Optic atrophy, nystagmus, scotoma, and bilateral retrobulbar neuritis.

Other: Mental retardation, myoclonic epilepsy, spasticity, and posterior column sensory loss. Tremor in some cases.

Musculoskeletal

Contractures, lower limbs, Achilles tendon contractures, Hamstring contractures, Adductor longus contractures

Systemic

Hypogonadotrophic hypogonadism.