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.

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.

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.

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.

A neurological examination would show evidence of muscle rigidity; weakness; and abnormal postures, movements, and tremors. If other family members are also affected, this may help determine the diagnosis. Genetic tests can confirm an abnormal gene causing the disease. However, this test is not yet widely available. Other movement disorders and diseases must be ruled out. Individuals exhibiting any of the above listed symptoms are often tested using MRI (Magnetic Resonance Imaging) for a number of neuro-related disorders. As PKAN is a disease prominently evident in the brain, MRIs are very useful in making a sound diagnosis. An MRI usually shows iron deposits in the basal ganglia. Development of diagnostic criteria continues in the hope of further separating PKAN from other forms of neurodegenerative diseases featuring NBIA.

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.

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.

Diagnosis of Jansky–Bielschowsky disease is increasingly based on assay of enzyme activity and molecular genetic testing. Thirteen pathogenic candidate genes—PPT1, TPP1, CLN3, CLN5, CLN6, MFSD8, CLN8, CTSD, DNAJC5, CTSF, ATP13A2 GRN, KCTD7—are associated with the development of the disease. Patients with Jansky–Bielschowsky disease typically have up to 50% reduced lysosomal enzymes, and thus an enzyme activity assay is a quick and easy diagnostic test.

Vision impairment is an early symptom of Jansky–Bielschowsky disease, and so an eye exam is another common diagnostic tool. During the eye exam, loss of cells within the eye would indicate the presence of the disease however more tests are needed for a complete diagnosis.

Other common diagnostic tests include:

- Blood or urine test: Elevated levels of the chemical dolichol found in the urine is typical of individuals with the disease, as well as the presence of vacuolated lymphocytes in the blood.

- Skin or tissue sampling: Microscopy of skin could be used to observe lipopigment aggregation.

- CT scan or MRI: Visualization of the brain would be able to detect areas of cerebral atrophy.

The diagnosis of SR deficiency is based on the analysis of the pterins and biogenic amines found in the cerebrospinal fluid (CSF) of the brain. The pterin compound functions as a cofactor in enzyme catalysis and biogenic amines which include adrenaline, dopamine, and serotonin have functions that vary from the control of homeostasis to the management of cognitive tasks. This analysis reveals decreased concentrations of homovanillic acid (HVA), 5-hydroxyindolacetic acid (HIAA), and elevated levels of 7,8-dihydrobiopterin, a compound produced in the synthesis of neurotransmitters. Sepiapterin is not detected by the regularly used methods applied in the investigation of biogenic monoamines metabolites in the cerebrospinal fluid. It must be determined by specialized methods that work by indicating a marked and abnormal increase of sepiapterin in cerebrospinal fluid. Confirmation of the diagnosis occurs by demonstrating high levels of CSF sepiapterin and a marked decrease of SR activity of the fibroblasts along with SPR gene molecular analysis.

Microscopic features of PKAN include:

- Iron granules

- Spheroid bodies

- Lewy bodies within neurons

Since paroxysmal exercise-induced dystonia is such a rare disorder it makes it difficult to study the disease and find consistencies. Many of the current studies seem to have contradicting conclusion but this is due to the fact that studies are usually limited to a very small number of test subjects. With such small numbers it is hard to determine what is a trend and what is random when in comes to characterizing the disease. Further study is needed to find better diagnostic techniques and treatments for PED. Patients with PED are living a limited lifestyle since simple tasks like walking and exercise are often impossible.

Brain MRI shows vermis atrophy or hypoplasic. Cerebral and cerebellar atrophy with white matter changes in some cases.

Though it is only definitively diagnosed by a genetic test, autosomal dominant porencephaly type I can be suspected if the disease is known to run in the family or if someone shows symptoms. CT scanning or MRI may be useful in indicating a diagnosis. COL4A1 may be mutated in other diseases that need to be distinguished, including brain small vessel disease with hemorrhage and HANAC syndrome. CADASIL syndrome is caused by a mutation in a different gene, but may cause similar symptoms. Sporadic porencephaly is another disorder that can appear similar.

Some cases of myotonia congenita do not require treatment, or it is determined that the risks of the medication outweigh the benefits. If necessary, however, symptoms of the disorder may be relieved with quinine, phenytoin, carbamazepine, mexiletine and other anticonvulsant drugs. Physical therapy and other rehabilitative measures may also be used to help muscle function. Genetic counseling is available.

Human findings provide insufficient data for developing treatments due to differences in the patients physiological and metabolic disorders thus, a suitable alternative animal model is essential in obtaining a better understanding of the SR deficiency. In this particular case, researchers used silkworms to identify and characterize mutations relating to SPR activity from an initial purified state created in the larvae of the silkworm. The researchers used genetic and biochemical approaches to demonstrate oral administration of BH and dopamine which increased the survival rates of the silkworm larvae. The results indicate that BH deficiency in silkworms leads to death in response to the lack of dopamine. This shows that silkworms can be useful insect models in additional SR deficiency research and study.

Sporadic cases may be brought on by minor head injuries and concussions. This was observed in one patient who started experiencing painless dystonia after mild exercise following a concussion. More research still needs to be done to determine how injuries can induce PED, as little is known in this area. Two cases of PED have been associated with insulinomas, after removal of which the symptoms of PED were resolved.

In those with SS, symptoms typically dramatically improve with low-dose administration of levodopa (L-dopa). L-DOPA exists as a biochemically significant metabolite of the amino acid phenylalanine, as well as a biological precursor of the catecholamine dopamine, a neurotransmitter. (Neurotransmitters are naturally produced molecules that may be sequestered following the propagation of an action potential down a nerve towards the axon terminal, which in turn may cross the synaptic junction between neurons, enabling neurons to communicate in a variety of ways.) Low-dose L-dopa usually results in near-complete or total reversal of all associated symptoms for these patients. In addition, the effectiveness of such therapy is typically long term, without the complications that often occur for those with Parkinson's disease who undergo L-dopa treatment. Thus, most experts indicate that this disorder is most appropriately known as dopa-responsive dystonia (SS).

No data are available on mortality associated with SS, but patients surviving beyond the fifth decade with treatment have been reported. However, in severe, early autosomal recessive forms of the disease, patients have been known to pass away during childhood. Girls seem to be somewhat more commonly affected. The disease less commonly begins during puberty or after age 20, and very rarely, cases in older adults have been reported.

Due to commonly being misdiagnosed, it is common for the disease to remain untreated. When left untreated, patients often need achilles tendon surgery by the age of 21. They will also struggle with walking, an ability that will degrade throughout the day. Power napping can provide temporary relief in untreated patients. It also impairs development into adulthood, reduces balance, and reduces calf muscle development. Socially, it can result in depression, lack of social skills, and inability to find employment.

Children of affected individuals are obligate carriers for aceruloplasminemia. If the CP mutations has been identified in a related individual, prenatal testing is recommended. Siblings of those affected by the disease are at a 25% of aceruloplasminemia. In asymptomatic siblings, serum concentrations of hemoglobin and hemoglobin A1c should be monitored.

To prevent the progression of symptoms of the disease, annual glucose tolerance tests beginning in early teen years to evaluate the onset of diabetes mellitus. Those at risk should avoid taking iron supplements.

Electroencephalography (EEG) in one patient showed epileptiformic activities in the frontal and frontotemporal areas as well as increased spike waves while the patient was sleeping. Another patient's EEG showed occipital rhythms in background activity that was abnormal, focal discharges over the temporal lobe, and multifocial epileptiform activity. Several patients showed a loss of normal background activity.

Magnetic Resonance Imaging (MRI) in one family showed mild atrophy of the cranial vermis as well as a small pons. Different types of atrophy including cerebellar in four individuals and basal ganglia has been evident through MRIs.

Currently, no treatment slows the neurodegeneration in any of the neuroacanthocytosis disorders. Medication may be administered to decrease the involuntary movements produced by these syndromes. Antipsychotics are used to block dopamine, anticonvulsants treat seizures and botulinum toxin injections may control dystonia. Patients usually receive speech, occupational and physical therapies to help with the complications associated with movement. Sometimes, physicians will prescribe antidepressants for the psychological problems that accompany neuroacanthocytosis. Some success has been reported with Deep brain stimulation.

Mouthguards and other physical protective devices may be useful in preventing damage to the lips and tongue due to the orofacial chorea and dystonia typical of chorea acanthocytosis.

There is no cure for XDP and medical treatment offers only temporary relief. Some authors have reported benzodiazepines and anticholinergic agents in the early stages of the disease. Botulinum toxin injections have been used to relieve focal dystonia. Deep brain stimulation has shown promise in the few cases treated surgically.

Plasma and cerebrospinal fluid levels of pipecolic acid are frequently elevated in patients with PDE, though it is a non-specific biomarker. α-aminodipic semialdehyde is elevated in urine and plasma and is a more specific biomarker for PDE. Improvements in these biomarkers have been reported with the implementation of a lysine-restricted diet. Initial studies evaluating the safety and efficacy of lysine restriction evaluated developmental and cognitive outcomes by age-appropriate tests and parental observations.

In northern Scandinavia, the prevalence of myotonia congenita has been estimated at 1:10,000.

Myotonia congenita is estimated to affect 1 in 1,000,000 people worldwide.

Diagnosis of this disorder depends on blood tests demonstrating the absence of serum ceruloplasmin, combined with low serum copper concentration, low serum iron concentration, high serum ferritin concentration, or increased hepatic iron concentration. MRI scans can also confirm a diagnosis; abnormal low intensities can indicate iron accumulation in the brain.