Diagnosis of MSA can be challenging because there is no test that can definitively make or confirm the diagnosis in a living patient. Clinical diagnostic criteria were defined in 1998 and updated in 2007. Certain signs and symptoms of MSA also occur with other disorders, such as Parkinson's disease, making the diagnosis more difficult.

Both MRI and CT scanning frequently show a decrease in the size of the cerebellum and pons in those with cerebellar features. The putamen is hypodense on T2-weighted MRI and may show an increased deposition of iron in Parkinsonian form. In cerebellar form, a "hot cross" sign has been emphasized; it reflects atrophy of the pontocereballar fibers that manifest in T2 signal intensity in atrophic pons.

A definitive diagnosis can only be made pathologically on finding abundant glial cytoplasmic inclusions in the central nervous system.

There is no known cure for MSA and management is primarily supportive.

Ongoing care from a neurologist specializing in "movement disorders" is recommended as the complex symptoms of MSA are often not familiar to less-specialized health care professionals.

One particularly serious problem, the drop in blood pressure upon standing up (with risk of fainting and thus injury from falling) often responds to fludrocortisone, a synthetic mineralocorticoid. Another common drug treatment is midodrine (an alpha-agonist). Non-drug treatments include "head-up tilt" (elevating the head of the whole bed by about 10 degrees), salt tablets or increasing salt in the diet, generous intake of fluids, and pressure (elastic) stockings. Avoidance of triggers of low blood pressure (such as hot weather, alcohol, and dehydration) are crucial.

Hospice/homecare services can be very useful as disability progresses.

Levodopa (L-Dopa), a drug used in the treatment of Parkinson's disease, improves parkinsonian symptoms in a small percentage of MSA patients. A recent trial reported that only 1.5% of MSA patients experienced a less than 50% improvement when taking levodopa, and even this was a transient effect lasting less than one year. Poor response to L-Dopa has been suggested as a possible element in the differential diagnosis of MSA from Parkinson's disease.

A November, 2008 study conducted in Europe failed to find an effect for the drug riluzole in treating MSA or PSP.

Physiotherapy intervention aims to improve balance and gait of OPCA patients, by stimulating neuroplastic changes in the atrophied neural structure. A challenge-oriented treatment program has previously been shown to be beneficial for individuals with ataxia from OPCA. The treatment program was composed of repetitive training with task challenges (e.g. obstacle course) and/or novel motor skills acquisition over a 12-week period under the supervision of a physiotherapist. Task challenges were progressed only when the patient showed mastery of a task.

Overground harness systems may be used to allow OPCA patients to challenge their balance without chance of falling. Furthermore, home exercise programs and/or aquatic exercises are used to allow more repetitions to facilitate balance learning. Treatment programs should be frequently monitored and adjusted based on a patient's progress. Outcome measures such as the Berg Balance Scale, Dynamic Gait Index and activities-specific balance confidence scales are useful to assess patient’s progress over time.

Arts syndrome should be included in the differential diagnosis of infantile hypotonia and weakness aggravated by recurrent infection with a family history of X-linked inheritance. Sequence analysis of PRPS1, the only gene associated with Arts syndrome, has detected mutations in both kindreds reported to date. Arts syndrome patients were also found to have reduced levels of hypoxanthine levels in urine and uric acid levels in the serum. In vitro, PRS-1 activity was reduced in erythrocytes and fibroblasts.

Olivopontocerebellar atrophy is hereditary, but has an unknown genetic basis. There are two forms:

A few non-hereditary diseases formerly categorized as olivopontocerebellar atrophy have been reclassified as forms of multiple system atrophy as well as to four hereditary types, that have been currently reclassified as four different forms of spinocerebellar ataxia:

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.

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.

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.

The types of imaging techniques that are most prominently utilized when studying and/or diagnosing CBD are:

- magnetic resonance imaging (MRI)

- single-photon emission computed tomography (SPECT)

- fluorodopa positron emission tomography (FDOPA PET)

Developments or improvements in imaging techniques provide the future possibility for definitive clinical diagnosis prior to death. However, despite their benefits, information learned from MRI and SPECT during the beginning of CBD progression tend to show no irregularities that would indicate the presence of such a neurodegenerative disease. FDOPA PET is used to study the efficacy of the dopamine pathway.

Despite the undoubted presence of cortical atrophy (as determined through MRI and SPECT) in individuals experiencing the symptoms of CBD, this is not an exclusive indicator for the disease. Thus, the utilization of this factor in the diagnosis of CBD should be used only in combination with other clinically present dysfunctions.

One of the most significant problems associated with CBD is the inability to perform a definitive diagnosis while an individual exhibiting the symptoms associated with CBD is still alive. A clinical diagnosis of CBD is performed based upon the specified diagnostic criteria, which focus mainly on the symptoms correlated with the disease. However, this often results in complications as these symptoms often overlap with numerous other neurodegenerative diseases. Frequently, a differential diagnosis for CBD is performed, in which other diseases are eliminated based on specific symptoms that do not overlap. However, some of the symptoms of CBD used in this process are rare to the disease, and thus the differential diagnosis cannot always be used.

Postmortem diagnosis provides the only true indication of the presence of CBD. Most of these diagnoses utilize the Gallyas-Braak staining method, which is effective in identifying the presence of astroglial inclusions and coincidental tauopathy.

Currently, purine replacement via S-adenosylmethionine (SAM) supplementation in people with Arts syndrome appears to improve their condition. This suggests that SAM supplementation can alleviate symptoms of PRPS1 deficient patients by replacing purine nucleotides and open new avenues of therapeutic intervention. Other non-clinical treatment options include educational programs tailored to their individual needs. Sensorineural hearing loss has been treated with cochlear implantation with good results. Ataxia and visual impairment from optic atrophy are treated in a routine manner. Routine immunizations against common childhood infections and annual influenza immunization can also help prevent any secondary infections from occurring.

Regular neuropsychological, audiologic, and ophthalmologic examinations are also recommended.

Carrier testing for at-risk relatives and prenatal testing for pregnancies at increased risk are possible if the disease-causing mutation in the family is known.

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.

The detection of tumours specific to VHL disease is important in the disease's diagnosis. In individuals with a family history of VHL disease, one hemangioblastoma, pheochromocytoma or renal cell carcinoma may be sufficient to make a diagnosis. As all the tumours associated with VHL disease can be found sporadically, at least two tumours must be identified to diagnose VHL disease in a person without a family history.

Genetic diagnosis is also useful in VHL disease diagnosis. In hereditary VHL, disease techniques such as southern blotting and gene sequencing can be used to analyse DNA and identify mutations. These tests can be used to screen family members of those afflicted with VHL disease; "de novo" cases that produce genetic mosaicism are more difficult to detect because mutations are not found in the white blood cells that are used for genetic analysis.

Niemann–Pick type C is diagnosed by assaying cultured fibroblasts for cholesterol esterfication and staining for unesterified cholesterol with filipin. The fibroblasts are grown from a small skin biopsy taken from a patient with suspected NPC. The diagnosis can be confirmed by identifying mutations in the NPC1 or NPC2 genes in 80–90% of cases. This specialized testing is available at Thomas Jefferson University Lysosomal Disease Testing Lab and the Mayo Clinic.

The lifespan of patients with NPC is usually related to the age of onset. Children with antenatal or infantile onset usually succumb in the first few months or years of life, whereas adolescent and adult onset forms of Niemann–Pick type C have a more insidious onset and slower progression, and affected individuals may survive to the seventh decade. Adult cases of NPC are being recognized with increasing frequency. It is suspected that many patients affected by NPC are undiagnosed, owing to lack of awareness of the disease and the absence of readily available screening or diagnostic tests. For the same reasons the diagnosis is often delayed by many years.

There is no way to reverse VHL mutations, but early recognition and treatment of specific manifestations of VHL can substantially decrease complications and improve quality of life. For this reason, individuals with VHL disease are usually screened routinely for retinal angiomas, CNS hemangioblastomas, clear-cell renal carcinomas and pheochromocytomas. CNS hemangioblastomas are usually surgically removed if they are symptomatic. Photocoagulation and cryotherapy are usually used for the treatment of symptomatic retinal angiomas, although anti-angiogenic treatments may also be an option. Renal tumours may be removed by a partial nephrectomy or other techniques such as radiofrequency ablation.

Hereditary gelsolin amyloidosis is a cutaneous condition inherited in an autosomal dominant fashion.

The condition was first described in 1969, by the Finnish ophthalmologist Jouko Meretoja, and is also known as Familial amyloid neuropathy type IV, Meretoja syndrome, Hereditary amyloidosis, Finnish type.

The disorder primarily associated with eye, skin and cranial nerve symptoms. It is a form of amyloidosis, where the amyloid complexes are formed from fragments of the protein gelsolin in the plasma, due to a mutation in the GSN gene (c.654G>A or c.654G>T).

Type A Niemann–Pick disease (about 85% of cases) has an extremely poor prognosis, with most cases being fatal by the age of 18 months. Type B (adult onset) and type C (mutation affecting a different molecule) Niemann–Pick diseases have a better prognosis.

There are four types of Niemann–Pick disease in two categories. Patients with ASM deficiency are classified into type A and B. Type A patients exhibit hepatosplenomegaly in infancy and profound central nervous system involvement and unable to survive beyond two years of age. Type B patients also show hepatosplenomegaly and pathologic alterations of their lungs but usually without the involvement of their central nervous system. Some can develop significant life-threatening complications including liver failure, hemorrhage, oxygen dependency, pulmonary infections, and splenic rupture. Some develop coronary artery or valvular heart disease. In a longitudinal natural history study, nearly 20% of the patients died. For those classified into type C, they may have mild hepatosplenomegaly, but their central nervous system is profoundly affected.

- Niemann–Pick disease, SMPD1-associated, which includes types A and B

- Niemann–Pick disease, type C: subacute/juvenile, includes types C1 (95% of type C) and C2. Type C is the most common form of the disease Type C2 is a rare form of the disease.

The International Olympic Committee recommends the eucapnic voluntary hyperventilation (EVH) challenge as the test to document exercise-induced asthma in Olympic athletes. In the EVH challenge, the patient voluntarily, without exercising, rapidly breathes dry air enriched with 5% for six minutes. The presence of the enriched compensates for the losses in the expired air, not matched by metabolic production, that occurs during hyperventilation, and so maintains levels at normal.

The Kadish classification is used for clinical classification of sinonasal tumors including esthesioneuroblastoma. Subsequent research articles have been published to determine prognosis based on tumor grade.

Dulguerov Classification

Diagnosis may include careful identification of the cause with the aid of a good patient history, swabs and cultures, and pathological examination of a biopsy.

Esthesioneuroblastoma is a slow developing but malignant tumor with high reoccurrence rates because of its anatomical position. The tumor composition, location and metastatic characteristics as well as the treatment plan determine prognosis. Common clinical classification systems for esthesioneuroblastoma include the Kadish classification and the Dulguerov classfictation. Histopathological characteristics on top of Kadish classification can further determine cancer prognosis. In severe, Kadish class C tumors, Haym's grades of pathology are important for prognosis. Patients with low grade Kadish class C tumors have a 10-year survival rate of 86 percent compared to patients with high grade class C tumors who have a survival rate of 28 percent. Surgically treated patients with high grade tumors are more likely to experience leptomeningeal metastases or involvement of the cerebral spinal fluid unlike patients with low grade tumors who usually only see local recurrence. Survival rates for treated esthesioneuroblastoma are best for surgery with radiotherapy (65%), then for radiotherapy and chemotherapy (51%), just surgery (48%), surgery, radiotherapy and chemotherapy (47) and finally just radiotherapy (37%). From the literature, radiotherapy and surgery seem to boast the best outcome for patients. However, it is important to understand that to some degree, prognosis is related to tumor severity. More progressed, higher grade tumors would result in chemotherapy or radiotherapy as the only treatment. It is no surprise that the prognosis would be worse in these cases.

Objective testing should begin with spirometry at rest. In true exercise-induced bronchoconstriction, the results should be within normal limits. Should resting values be abnormal, then asthma, or some other chronic lung condition, is present. There is, of course, no reason why asthma and exercise-induced bronchoconstriction should not co-exist but the distinction is important because without successful treatment of underlying asthma, treatment of an exercise component will likely be unsuccessful. If baseline testing is normal, some form of exercise or pharmacologic stress will be required, either on the sideline or practice venue, or in the laboratory.

There has been no specific drug therapy developed for hepatitis, with the exception of hepatitis C. Patients are advised to rest in the early stages of the illness, and to eat small, high-calorie, high-protein meals in order to battle anorexia. Larger meals are more easily tolerated in the morning, for patients often experience nausea later in the day. Although high-protein meals are recommended, protein intake should be reduced if signs of precoma — lethargy, confusion, and mental changes — develop.

In acute viral hepatitis, hospitalization is usually required only for patients with severe symptoms (severe nausea, vomiting, change in mental status, and PT greater than 3 seconds above normal) or complications. If the patient experiences continuous vomiting and is unable to maintain oral intake, parenteral nutrition may be required.

In order to relieve nausea and also prevent vomiting, antiemetics (diphenhydramine or prochlorperazine) may be given 30 minutes before meals. However, phenothiazines have a cholestatic effect and should be avoided. The resin cholestyramine may be given only for severe pruritus.