Embryos produced using in vitro fertilization may be genetically tested for HD using preimplantation genetic diagnosis (PGD). This technique, where one or two cells are extracted from a typically 4- to 8-cell embryo and then tested for the genetic abnormality, can then be used to ensure embryos affected with HD genes are not implanted, and therefore any offspring will not inherit the disease. Some forms of preimplantation genetic diagnosis—non-disclosure or exclusion testing—allow at-risk people to have HD-free offspring "without" revealing their own parental genotype, giving no information about whether they themselves are destined to develop HD. In exclusion testing, the embryos' DNA is compared with that of the parents and grandparents to avoid inheritance of the chromosomal region containing the HD gene from the affected grandparent. In non-disclosure testing, only disease-free embryos are replaced in the uterus while the parental genotype and hence parental risk for HD are never disclosed.

It is also possible to obtain a prenatal diagnosis for an embryo or fetus in the womb, using fetal genetic material acquired through chorionic villus sampling. An amniocentesis can be performed if the pregnancy is further along, within 14–18 weeks. This procedure looks at the amniotic fluid surrounding the baby for indicators of the HD mutation. This, too, can be paired with exclusion testing to avoid disclosure of parental genotype. Prenatal testing can be done when a parent has been diagnosed with HD, when they have had genetic testing showing the expansion of the HTT gene, or when they have a 50% chance of inheriting the disease. The parents can be counseled on their options, which include termination of pregnancy, and on the difficulties of a child with the identified gene.

In addition, in at-risk pregnancies due to an affected male partner, non-invasive prenatal diagnosis can be performed by analyzing cell-free fetal DNA in a blood sample taken from the mother (via venipuncture) between six and twelve weeks of pregnancy. It has no procedure-related risk of miscarriage (excepting via needle contamination).

Computed tomography (CT) scans of people with PD usually appear normal. MRI has become more accurate in diagnosis of the disease over time, specifically through iron-sensitive T2* and SWI sequences at a magnetic field strength of at least 3T, both of which can demonstrate absence of the characteristic 'swallow tail' imaging pattern in the dorsolateral substantia nigra. In a meta-analysis, absence of this pattern was 98% sensitive and 95% specific for the disease. Diffusion MRI has shown potential in distinguishing between PD and Parkinson plus syndromes, though its diagnostic value is still under investigation. CT and MRI are also used to rule out other diseases that can be secondary causes of parkinsonism, most commonly encephalitis and chronic ischemic insults, as well as less frequent entities such as basal ganglia tumors and hydrocephalus.

Dopamine-related activity in the basal ganglia can be directly measured with PET and SPECT scans. A finding of reduced dopamine-related activity in the basal ganglia can rule out drug-induced parkinsonism, but reduced basal ganglia dopamine-related activity is seen in both PD and the Parkinson-plus disorders so these scans are not reliable in distinguishing PD from other neurodegenerative causes of parkinsonism.

A physician will initially assess for Parkinson's disease with a careful medical history and neurological examination. People may be given levodopa, with any resulting improvement in motor impairment helping to confirm the PD diagnosis. The finding of Lewy bodies in the midbrain on autopsy is usually considered final proof that the person had PD. The clinical course of the illness over time may reveal it is not Parkinson's disease, requiring that the clinical presentation be periodically reviewed to confirm accuracy of the diagnosis.

Other causes that can secondarily produce parkinsonism are stroke and drugs. Parkinson plus syndromes such as progressive supranuclear palsy and multiple system atrophy must be ruled out. Anti-Parkinson's medications are typically less effective at controlling symptoms in Parkinson plus syndromes. Faster progression rates, early cognitive dysfunction or postural instability, minimal tremor or symmetry at onset may indicate a Parkinson plus disease rather than PD itself. Genetic forms with an autosomal dominant or recessive pattern of inheritance are sometimes referred to as familial Parkinson's disease or familial parkinsonism.

Medical organizations have created diagnostic criteria to ease and standardize the diagnostic process, especially in the early stages of the disease. The most widely known criteria come from the UK Queen Square Brain Bank for Neurological Disorders and the U.S. National Institute of Neurological Disorders and Stroke. The Queen Square Brain Bank criteria require slowness of movement (bradykinesia) plus either rigidity, resting tremor, or postural instability. Other possible causes of these symptoms need to be ruled out. Finally, three or more of the following supportive features are required during onset or evolution: unilateral onset, tremor at rest, progression in time, asymmetry of motor symptoms, response to levodopa for at least five years, clinical course of at least ten years and appearance of dyskinesias induced by the intake of excessive levodopa.

When PD diagnoses are checked by autopsy, movement disorders experts are found on average to be 79.6% accurate at initial assessment and 83.9% accurate after they have refined their diagnosis at a follow-up examination. When clinical diagnoses performed mainly by nonexperts are checked by autopsy, average accuracy is 73.8%. Overall, 80.6% of PD diagnoses are accurate, and 82.7% of diagnoses using the Brain Bank criteria are accurate.

A task force of the International Parkinson and Movement Disorder Society (MDS) has proposed diagnostic criteria for Parkinson’s disease as well as research criteria for the diagnosis of prodromal disease, but these will require validation against the more established criteria.

Accurate diagnosis of these Parkinson-plus syndromes is improved when precise diagnostic criteria are used. Since diagnosis of individual Parkinson-plus syndromes is difficult, the prognosis is often poor. Proper diagnosis of these neurodegenerative disorders is important as individual treatments vary depending on the condition. The nuclear medicine SPECT procedure using I-IBZM, is an effective tool in the establishment of the differential diagnosis between patients with PD and Parkinson-plus syndromes.

To gain a better understanding of the disease, researchers have retrospectively reviewed medical records of probands and others who were assessed through clinical examinations or questionnaires. Blood samples are collected from the families of the probands for genetic testing. These family members are assessed using their standard medical history, on their progression of Parkinson's like symptoms (Unified Parkinson's Disease Rating Scale), and on their progression of cognitive impairment such as dementia (Folstein Test).

Standard MRI scans have been performed on 1.5 Tesla scanners with 5 mm thickness and 5 mm spacing to screen for white matter lesions in identified families. If signal intensities of the MRI scans are higher in white matter regions than in grey matter regions, the patient is considered to be at risk for HDLS, although a number of other disorders can also produce white matter changes and the findings are not diagnostic without genetic testing or pathologic confirmation.

Parkinson-plus syndromes are usually more rapidly progressive and less likely to respond to antiparkinsonian medication than PD. However, the additional features of the diseases may respond to medications not used in PD.

Current therapy for Parkinson-plus syndromes is centered around a multidisciplinary treatment of symptoms.

These disorders have been linked to pesticide exposure.

Genetic testing can confirm a neuroferritinopathy diagnosis. A diagnosis can be made by analyzing the protein sequences of affected individuals and comparing them to known neuroferritinopathy sequences.

Blood tests usually come back normal in affected individuals, so they do not serve as a reliable means of diagnosis. Blood tests can show low serum ferritin levels. However, this is unreliable as method of diagnosis, as some patients show typical serum ferritin levels even at the latest stages of neuroferritinopathy. Cerebral spinal fluid tests also are typically normal.

Ferritin found in the skin, liver, kidney, and muscle tissues may help in diagnosing neuroferritinopathy. More cytochrome c oxidase-negative fibers are also often found in the muscle biopsies of affected individuals.

Protein function tests that demonstrate a reduce in chorein levels and also genetic analysis can confirm the diagnosis given to a patient. For a disease like this it is often necessary to sample the blood of the patient on multiple occasions with a specific request given to the haematologist to examine the film for acanthocytes. Another point is that the diagnosis of the disease can be confirmed by the absence of chorein in the western blot of the erythrocyte membranes.

Due to the condition's rarity, it is frequently misdiagnosed, often as cerebral palsy. This results in patients often living their entire childhood with the condition untreated.

The diagnosis of SS can be made from a typical history, a trial of dopamine medications, and genetic testing. Not all patients show mutations in the GCH1 gene (GTP cyclohydrolase I), which makes genetic testing imperfect.

Sometimes a lumbar puncture is performed to measure concentrations of biopterin and neopterin, which can help determine the exact form of dopamine-responsive movement disorder: early onset parkinsonism (reduced biopterin and normal neopterin), GTP cyclohydrolase I deficiency (both decreased) and tyrosine hydroxylase deficiency (both normal).

In approximately half of cases, a phenylalanine loading test can be used to show decreased conversion from the amino acid phenylalanine to tyrosine. This process uses BH4 as a cofactor.

During a sleep study (polysomnography), decreased twitching may be noticed during REM sleep.

An MRI scan of the brain can be used to look for conditions that can mimic SS (for example, metal deposition in the basal ganglia can indicate Wilson's disease or pantothenate kinase-associated neurodegeneration). Nuclear imaging of the brain using positron emission tomography (PET scan) shows a normal radiolabelled dopamine uptake in SS, contrary to the decreased uptake in Parkinson's disease.

Other differential diagnoses include metabolic disorders (such as GM2 gangliosidosis, phenylketonuria, hypothyroidism, Leigh disease) primarily dystonic juvenile parkinsonism, autosomal recessive early onset parkinsonism with diurnal fluctuation, early onset idiopathic parkinsonism, focal dystonias, dystonia musculorum deformans and dyspeptic dystonia with hiatal hernia.

- Diagnosis - main

- typically referral by GP to specialist Neurological Hospital e.g. National Hospital in London.

- very hard to diagnose as condition is dynamic w.r.t. time-of-day AND dynamic w.r.t. age of patient.

- correct diagnosis only made by a consultant neurologist with a complete 24-hour day-cycle observation(with video/film) at a Hospital i.e. morning(day1)->noon->afternoon->evening->late-night->sleep->morning(day2).

- patient with suspected SS required to walk in around hospital in front of Neuro'-consultant at selected daytime intervals to observe worsening walking pattern coincident with increased muscle tension in limbs.

- throughout the day, reducing leg-gait, thus shoe heels catching one another.

- diurnal affect of condition: morning(fresh/energetic), lunch(stiff limbs), afternoon(very stiff limbs), evening(limbs worsening), bedtime(limbs near frozen).

- muscle tension in thighs/arms: morning(normal), lunch(abnormal), afternoon(very abnormal), evening(bad), bedtime(frozen solid).

- Diagnosis - additional

- lack of self-esteem at school/college/University -> eating disorders in youth thus weight gains.

- lack of energy during late-daytime (teens/adult) -> compensate by over-eating.

There is no cure for spinocerebellar ataxia, which is currently considered to be a progressive and irreversible disease, although not all types cause equally severe disability.

In general, treatments are directed towards alleviating symptoms, not the disease itself. Many patients with hereditary or idiopathic forms of ataxia have other symptoms in addition to ataxia. Medications or other therapies might be appropriate for some of these symptoms, which could include tremor, stiffness, depression, spasticity, and sleep disorders, among others. Both onset of initial symptoms and duration of disease are variable. If the disease is caused by a polyglutamine trinucleotide repeat CAG expansion, a longer expansion may lead to an earlier onset and a more radical progression of clinical symptoms. Typically, a person afflicted with this disease will eventually be unable to perform daily tasks (ADLs). However, rehabilitation therapists can help patients to maximize their ability of self-care and delay deterioration to certain extent. Researchers are exploring multiple avenues for a cure including RNAi and the use of Stem Cells and several other avenues.

On January 18, 2017 BioBlast Pharma announced completion of Phase 2a clinical trials of their medication, Trehalose, in the treatment of SCA3. BioBlast has received FDA Fast Track status and Orphan Drug status for their treatment. The information provided by BioBlast in their research indicates that they hope this treatment may prove efficacious in other SCA treatments that have similar pathology related to PolyA and PolyQ diseases.

In addition, Dr. Beverly Davidson has been working on a methodology using RNAi technology to find a potential cure for over 2 decades. Her research began in the mid-1990s and progressed to work with mouse models about a decade later and most recently has moved to a study with non-human primates. The results from her most recent research "are supportive of clinical application of this gene therapy". Dr. Davidson along with Dr. Pedro Gonzalez-Alegre are currently working to move this technique into a Phase 1 clinical trial.

Finally, another gene transfer technology discovered in 2011 has also been shown by Dr. Davidson to hold great promise and offers yet another avenue to a potential future cure.

Definitive diagnosis of FTDP-17 requires a combination of characteristic clinical and pathological features and molecular genetic analysis. Genetic counseling should be offered to affected and at-risk individuals; for most subtypes, penetrance is incomplete.

There is no known prevention of spinocerebellar ataxia. Those who are believed to be at risk can have genetic sequencing of known SCA loci performed to confirm inheritance of the disorder.

In diagnosing autosomal dominant cerebellar ataxia the individuals clinical history or their past health examinations, a current physical examination to check for any physical abnormalities, and a genetic screening of the patients genes and the genealogy of the family are done. The large category of cerebellar ataxia is caused by a deterioration of neurons in the cerebellum, therefore magnetic resonance imaging (MRI) is used to detect any structural abnormality such as lesions which are the primary cause of the ataxia. Computed tomography (CT) scans can also be used to view neuronal deterioration, but the MRI provides a more accurate and detailed picture.

Physical therapists can assist patients in maintaining their level of independence through therapeutic exercise programmes. One recent research report demonstrated a gain of 2 SARA points (Scale for the Assessment and Rating of Ataxia) from physical therapy. In general, physical therapy emphasises postural balance and gait training for ataxia patients. General conditioning such as range-of-motion exercises and muscle strengthening would also be included in therapeutic exercise programmes. Research showed that spinocerebellar ataxia 2 (SCA2) patients with a mild stage of the disease gained significant improvement in static balance and neurological indices after six months of a physical therapy exercise training program. Occupational therapists may assist patients with incoordination or ataxia issues through the use of adaptive devices. Such devices may include a cane, crutches, walker, or wheelchair for those with impaired gait. Other devices are available to assist with writing, feeding, and self care if hand and arm coordination are impaired. A randomised clinical trial revealed that an intensive rehabilitation program with physical and occupational therapies for patients with degenerative cerebellar diseases can significantly improve functional gains in ataxia, gait, and activities of daily living. Some level of improvement was shown to be maintained 24 weeks post-treatment. Speech language pathologists may use both behavioral intervention strategies as well as augmentative and alternative communication devices to help patients with impaired speech.

Different types of ataxia:

- congenital ataxias (developmental disorders)

- ataxias with metabolic disorders

- ataxias with a DNA repair defect

- degenerative ataxias

- ataxia associated with other features.

Because vision loss is often an early sign, Batten disease/NCL may be first suspected during an eye exam. An eye doctor can detect a loss of cells within the eye that occurs in the three childhood forms of Batten disease/NCL. However, because such cell loss occurs in other eye diseases, the disorder cannot be diagnosed by this sign alone. Often an eye specialist or other physician who suspects Batten disease/NCL may refer the child to a neurologist, a doctor who specializes in disease of the brain and nervous system. In order to diagnose Batten disease/NCL, the neurologist needs the patient's medical history and information from various laboratory tests.

Diagnostic tests used for Batten disease/NCLs include:

- Skin or tissue sampling. The doctor can examine a small piece of tissue under an electron microscope. The powerful magnification of the microscope helps the doctor spot typical NCL deposits. These deposits are found in many different tissues, including skin, muscle, conjunctiva, rectal and others. Blood can also be used. These deposits take on characteristic shapes, depending on the variant under which they are said to occur: granular osmophilic deposits (GRODs) are generally characteristic of INCL, while curvilinear profiles, fingerprint profiles, and mixed-type inclusions are typically found in LINCL, JNCL, and ANCL, respectively.

- Electroencephalogram or EEG. An EEG uses special patches placed on the scalp to record electrical currents inside the brain. This helps doctors see telltale patterns in the brain's electrical activity that suggest a patient has seizures.

- Electrical studies of the eyes. These tests, which include visual-evoked responses (VER) and electroretinograms (ERG), can detect various eye problems common in childhood Batten disease/NCLs.

- Brain scans. Imaging can help doctors look for changes in the brain's appearance. The most commonly used imaging technique is computed tomography (CT), which uses x-rays and a computer to create a sophisticated picture of the brain's tissues and structures. A CT scan may reveal brain areas that are decaying in NCL patients. A second imaging technique that is increasingly common is magnetic resonance imaging, or MRI. MRI uses a combination of magnetic fields and radio waves, instead of radiation, to create a picture of the brain.

- Enzyme assay. A recent development in diagnosis of Batten disease/NCL is the use of enzyme assays that look for specific missing lysosomal enzymes for infantile and late infantile only. This is a quick and easy diagnostic test.

Three main approaches have been used to prevent or reduce the incidence of Tay–Sachs:

- Prenatal diagnosis. If both parents are identified as carriers, prenatal genetic testing can determine whether the fetus has inherited a defective gene copy from both parents. Chorionic villus sampling (CVS), the most common form of prenatal diagnosis, can be performed between 10 and 14 weeks of gestation. Amniocentesis is usually performed at 15–18 weeks. These procedures have risks of miscarriage of 1% or less.

- Preimplantation genetic diagnosis. By retrieving the mother's eggs for in vitro fertilization, it is possible to test the embryo for the disorder prior to implantation. Healthy embryos are then selected and transferred into the mother's womb, while unhealthy embryos are discarded. In addition to Tay–Sachs disease, preimplantation genetic diagnosis has been used to prevent cystic fibrosis and sickle cell anemia among other genetic disorders.

- Mate selection. In Orthodox Jewish circles, the organization Dor Yeshorim carries out an anonymous screening program so that carrier couples for Tay–Sachs and other genetic disorders can avoid marriage.

Clinical diagnosis is conducted on individuals with age onset between late teens and late forties who show the initial characteristics for the recessive autosomal cerebellar ataxia.

The following tests are performed:

- MRI brain screening for cerebellum atrophy.

- Molecular genetic testing for SYNE-1 sequence analysis.

- Electrophysiologic studies for polyneurotherapy

- Neurological examination

Prenatal diagnosis and preimplantation genetic diagnosis (PGD) can be performed to identify the mothers carrying the recessive genes for cerebellar ataxia.

The prognosis and rate of the diseases progression vary considerably among individual patients and genetic kindreds, ranging from life expectancies of several months to several years, and, in exceptional cases, as long as two decades.

There is currently no cure for SCA 6; however, there are supportive treatments that may be useful in managing symptoms.

In terms of a cure there is currently none available, however for the disease to manifest itself, it requires mutant gene expression. Manipulating the use of protein homoestasis regulators can be therapuetic agents, or a treatment to try and correct an altered function that makes up the pathology is one current idea put forth by Bushart, et al. There is some evidence that for SCA1 and two other polyQ disorders that the pathology can be reversed after the disease is underway. There is no effective treatments that could alter the progression of this disease, therefore care is given, like occupational and physical therapy for gait dysfunction and speech therapy.

This condition is very rare, only affecting one in two million people. It is more common in females than in males. There are several hundred cases in the United States, 25 known cases in the United Kingdom, and less than that in Australia and New Zealand.