In October 2007 an astute medical interpreter noticed similar neurological symptoms being reported by Spanish-speaking patients seeking treatment from different physicians at the Austin Medical Center, in Austin, Minnesota. Not only did these patients share similar neurological symptoms, they also worked at the same pork processing plant. Dr. Daniel LaChance, a physician at both the Austin Medical Center and the Mayo Clinic in nearby Rochester, Minnesota, was notified. He launched a request to area physicians to refer other patients with similar symptoms to him. The Minnesota Department of Health (MDH) was notified and began an investigation into the "outbreak." The MDH identified workers from two other pork processing plants in Indiana and Nebraska who also had parallel neurological complaints. Several agencies including the Occupational Safety and Health Administration (OSHA) and the Center for Disease Control and Prevention (CDC) were brought in to assist. Simultaneously investigations were conducted to rule out contagious disease, to locate the source or carrier, and to identify what exactly was causing these workers to develop these symptoms.

Removal from exposure was the first line of treatment. Due to progressive sensory loss and weakness, immunotherapy was often required. These treatments included intravenous methylprednisolone, oral prednisone, azathioprine, and/or immunoglobulin. All 24 patients improved, including 7 who received no treatment and 17 who required immunotherapy.

In terms of the differential diagnosis for polyneuropathy one must look at the following:

As in multiple sclerosis, another demyelinating condition, it is not possible to predict with certainty how CIDP will affect patients over time. The pattern of relapses and remissions varies greatly with each patient. A period of relapse can be very disturbing, but many patients make significant recoveries.

If diagnosed early, initiation of early treatment to prevent loss of nerve axons is recommended. However, many individuals are left with residual numbness, weakness, tremors, fatigue and other symptoms which can lead to long-term morbidity and diminished quality of life.

It is important to build a good relationship with doctors, both primary care and specialist. Because of the rarity of the illness, many doctors will not have encountered it before. Each case of CIDP is different, and relapses, if they occur, may bring new symptoms and problems. Because of the variability in severity and progression of the disease, doctors will not be able to give a definite prognosis. A period of experimentation with different treatment regimens is likely to be necessary in order to discover the most appropriate treatment regimen for a given patient.

The diagnosis of polyneuropathies begins with a history and physical examination to ascertain the pattern of the disease process (such as-arms, legs, distal, proximal) if they fluctuate, and what deficits and pain are involved. If pain is a factor, determining where and how long the pain has been present is important, one also needs to know what disorders are present within the family and what diseases the person may have. Although diseases often are suggested by the physical examination and history alone, tests that may be employed include: electrodiagnostic testing, serum protein electrophoresis, nerve conduction studies, urinalysis, serum creatine kinase (CK) and antibody testing (nerve biopsy is sometimes done).

Other tests may be used, especially tests for specific disorders associated with polyneuropathies, quality measures have been developed to diagnose patients with distal symmetrical polyneuropathy (DSP).

Over 40 laboratory tests were initially conducted to rule out various pathogens and environmental toxins. These tests were used to try to identify potential viruses carried by humans, pigs, or both, including rotoviruses, adenoviruses, hepatitis A, and hepatitis E. They also tried to identify bacteria such as salmonella and escherichia coli (e. coli), and parasites such as Giardia and cryptosporidium that could be causing the symptoms. All were ruled out.

Neurodegenerative diseases were considered specifically because of the similarity of symptoms and animal involvement thus included investigation of prion associated diseases such as bovine spongiform encephalopathy (BSE), chronic wasting disease (CWD), and variant Creutzfeldt–Jakob disease (vCJD). These all have highly transmissible pathogenic agents that induce brain damage. Since no pathogenic agent had been found, these diseases were ruled out as being related.

Next two very similar neuropathies were ruled out. Guillain–Barré syndrome (GBS) induces an acute autoimmune response which affects the Schwann cells in the peripheral nervous system. GBS is usually triggered by an infection that causes weakness and tingling that may lead to muscle loss. This condition may be life-threatening if muscle atrophy ascends to affect the pulmonary or cardiac systems. So far, no infectious agents have been found that relate to the current disease, progressive infammatory neuropathy. They looked at chronic inflammatory demyelinating polyneuropathy (CIDP) which is characterized by progressive weakness and sensory impairment in the arms and legs. Damage occurs to the myelin sheath in the peripheral nervous system. As doctors at the Mayo Clinic were beginning to note, the problem they were seeing in progressive inflammatory neuropathy was occurring in the spinal nerve roots.

Initial screening for CIP/CIM may be performed using an objective scoring system for muscle strength. The Medical Research Council (MRC) score is one such tool, and sometimes used to help identify CIP/CIM patients in research studies. The MRC score involves assessing strength in 3 muscle groups in the right and left sides of both the upper and lower extremities. Each muscle tested is given a score of 0-5, giving a total possible score of 60. An MRC score less than 48 is suggestive of CIP/CIM. However, the tool requires that patients be awake and cooperative, which is often not the case. Also, the screening tool is non-specific, because it does not identify the cause a person's muscle weakness.

Once weakness is detected, the evaluation of muscle strength should be repeated several times. If the weakness persists, then a muscle biopsy, a nerve conduction study (electrophysiological studies), or both should be performed.

There are several types of immune-mediated neuropathies recognised. These include

- Chronic inflammatory demyelinating polyneuropathy (CIPD) with subtypes:

- Classical CIDP

- CIDP with diabetes

- CIDP/monoclonal gammopathy of undetermined significance

- Sensory CIDP

- Multifocal motor neuropathy

- Multifocal acquired demyelinating sensory and motor neuropathy (Lewis-Sumner syndrome)

- Multifocal acquired sensory and motor neuropathy

- Distal acquired demyelinating sensory neuropathy

- Guillain-Barre syndrome with subtypes:

- Acute inflammatory demyelinating polyradiculoneuropathy

- Acute motor axonal neuropathy

- Acute motor and sensory axonal neuropathy

- Acute pandysautonomia

- Miller Fisher syndrome

- IgM monoclonal gammopathies with subtypes:

- Waldenstrom's macroglobulinemia

- Mixed cryoglobulinemia, gait ataxia, late-onset polyneuropathy syndrome

- Myelin-associated glycoprotein-associated gammopathy, polyneuropathy, organomegaly, endocrinopathy, M-protein and skin changes syndrome (POEMS)

For this reason a diagnosis of chronic inflammatory demyelinating polyneuropathy needs further investigations.

The diagnosis is usually provisionally made through a clinical neurological examination. Patients usually present with a history of weakness, numbness, tingling, pain and difficulty in walking. They may additionally present with fainting spells while standing up or burning pain in extremities. Some patients may have sudden onset of back pain or neck pain radiating down the extremities, usually diagnosed as radicular pain. These symptoms are usually progressive and may be intermittent.

Autonomic system dysfunction can occur; in such a case, the patient would complain of orthostatic dizziness, problems breathing, eye, bowel, bladder and cardiac problems. The patient may also present with a single cranial nerve or peripheral nerve dysfunction.

On examination the patients may have weakness, and loss of deep tendon reflexes (rarely increased or normal). There may be atrophy (shrinkage) of muscles, fasciculations (twitching) and loss of sensation. Patients may have multi-focal motor neuropathy, as they have no sensory loss.

Most experts consider the necessary duration of symptoms to be greater than 8 weeks for the diagnosis of CIDP to be made.

Typical diagnostic tests include:

- Electrodiagnostics – electromyography (EMG) and nerve conduction study (NCS). In usual CIDP, the nerve conduction studies show demyelination. These findings include:

1. a reduction in nerve conduction velocities;

2. the presence of conduction block or abnormal temporal dispersion in at least one motor nerve;

3. prolonged distal latencies in at least two nerves;

4. absent F waves or prolonged minimum F wave latencies in at least two motor nerves. (In some case EMG/NCV can be normal).

- Serum test to exclude other autoimmune diseases.

- Lumbar puncture and serum test for anti-ganglioside antibodies. These antibodies are present in the branch of CIDP diseases comprised by anti-GM1, anti-GD1a, and anti-GQ1b.

- Sural nerve biopsy; biopsy is considered for those patients in whom the diagnosis is not completely clear, when other causes of neuropathy (e.g., hereditary, vasculitic) cannot be excluded, or when profound axonal involvement is observed on EMG.

- Ultrasound of the periferal nerves may show swelling of the affected nerves

- MRI can also be used in the diagnosic workup

In some cases electrophysiological studies fail to show any evidence of demyelination. Though conventional electrophysiological diagnostic criteria are not met, the patient may still respond to immunomodulatory treatments. In such cases, presence of clinical characteristics suggestive of CIDP are critical, justifying full investigations, including sural nerve biopsy.

The serum creatine phosphokinase (CPK) can be mildly elevated. While the CPK is often a good marker for damage to muscle tissue, it is not a helpful marker in CIP/CIM, because CIP/CIM is a gradual process and does not usually involve significant muscle cell death (necrosis). Also, even if necrosis is present, it may be brief and is therefore easily missed. If a lumbar puncture (spinal tap) is performed, the protein level in the cerebral spinal fluid would be normal.

Below are various methods/techniques used to diagnose demyelinating diseases.

- Exclusion of other conditions that have overlapping symptoms

- Magnetic resonance imaging (MRI) is a medical imaging technique used in radiology to visualize internal structures of the body in detail. MRI makes use of the property of nuclear magnetic resonance (NMR) to image nuclei of atoms inside the body. This method is reliable because MRIs assess changes in proton density. "Spots" can occur as a result of changes in brain water content.

- Evoked potential is an electrical potential recorded from the nervous system following the presentation of a stimulus as detected by electroencephalography (EEG), electromyography (EMG), or other electrophysiological recording method.

- Cerebrospinal fluid analysis (CSF) can be extremely beneficial in the diagnosis of central nervous system infections. A CSF culture examination may yield the microorganism that caused the infection.

- Quantitative proton magnetic resonance spectroscopy (MRS) is a non-invasive analytical technique that has been used to study metabolic changes in brain tumors, strokes, seizure disorders, Alzheimer's disease, depression and other diseases affecting the brain. It has also been used to study the metabolism of other organs such as muscles.

- Diagnostic criteria refers to a specific combination of signs, symptoms, and test results that the clinician uses in an attempt to determine the correct diagnosis.

- Fluid-attenuated inversion recovery (FLAIR) uses a pulse sequence to suppress cerebrospinal fluid and show lesions more clearly, and is used for example in multiple sclerosis evaluation.

Peripheral neuropathy may first be considered when an individual reports symptoms of numbness, tingling, and pain in feet. After ruling out a lesion in the central nervous system as a cause, diagnosis may be made on the basis of symptoms, laboratory and additional testing, clinical history, and a detailed examination.

During physical examination, specifically a neurological examination, those with generalized peripheral neuropathies most commonly have distal sensory or motor and sensory loss, although those with a pathology (problem) of the nerves may be perfectly normal; may show proximal weakness, as in some inflammatory neuropathies, such as Guillain–Barré syndrome; or may show focal sensory disturbance or weakness, such as in mononeuropathies. Classically, ankle jerk reflex is absent in peripheral neuropathy.

A physical examination will involve testing the deep ankle reflex as well as examining the feet for any ulceration. For large fiber neuropathy, an exam will usually show an abnormally decreased sensation to vibration, which is tested with a 128-Hz tuning fork, and decreased sensation of light touch when touched by a nylon monofilament.

Diagnostic tests include electromyography (EMG) and nerve conduction studies (NCSs), which assess large myelinated nerve fibers. Testing for small-fiber peripheral neuropathies often relates to the autonomic nervous system function of small thinly- and unmyelinated fibers. These tests include a sweat test and a tilt table test. Diagnosis of small fiber involvement in peripheral neuropathy may also involve a skin biopsy in which a 3 mm-thick section of skin is removed from the calf by a punch biopsy, and is used to measure the skin intraepidermal nerve fiber density (IENFD), the density of nerves in the outer layer of the skin. Reduced density of the small nerves in the epidermis supports a diagnosis of small-fiber peripheral neuropathy.

Laboratory tests include blood tests for vitamin B-12 levels, a complete blood count, measurement of thyroid stimulating hormone levels, a comprehensive metabolic panel screening for diabetes and pre-diabetes, and a serum immunofixation test, which tests for antibodies in the blood.

MRI is the most sensitive imaging technique that can be used for diagnosing NBD. As for the parenchymal NBD, medical doctors mainly monitor the upper brainstem lesion. In fact, it is possible that lesions extends to thalamus and basal ganglia. Another advantage of using MRI is the ability to perform Diffusion-weighted imaging, or diffusion MRI. This technique is the most sensitive tool to image an acute infarct. In the case of NBD, Diffusion MRI can determine whether the lesion were due to cerebral infarction. In other words, it can distinguish NBD from non-NBD neural disease. When only spinal cord is affected by NBD, brain looks perfectly normal when scanned by MRI. Therefore, it is necessary to scan the spinal cord as well when diagnosing possible NBD involvement. As for the non-parenchymal NBD, venous sinus thrombosis can be detected.

Demyelinating diseases can be divided in those affecting the central nervous system and those presents in the peripheral nervous system, presenting different demyelination conditions. They can also be divided by other criteria in inflammatory and non-inflammatory, according to the presence or lack of inflammation, and finally, a division can also be made depending on the underlying reason for demyelination in myelinoclastic (myelin is attacked by an external substance) and leukodystrophic (myelin degenerates without attacks)

For diagnosis of NPSLE, it must be determined whether neuropsychiatric symptoms are indeed caused by SLE, whether they constitute a separate comorbid condition, or whether they are an adverse effect of disease treatment. In addition, onset of neuropsychiatric symptoms may happen prior to the diagnosis of lupus. Due to the lack of uniform diagnostic standards, statistics about NPSLE vary widely.

Tests which aid in diagnosis include MRI, electrophysiological studies, psychiatric evaluation, and autoantibody tests.

At least one study suggests that gluten neuropathy can be effectively treated with a gluten-free diet. In the study, 35 patients with gluten neuropathy adhered to a gluten-free diet, where adherence was monitored serologically. After one year, the treatment group had improved significantly compared to the control group. The indicators of improvements were improvements of sural sensory action potential and subjective improvement of neuropathic symptoms. Subgroup analysis suggested that severe neuropathy might imply reduced capacity for recovery of the peripheral nerves or longer recovery.

The prognosis for Tropical spastic paraparesis indicates some improvement in a percentage of cases due to immunosuppressive treatment. A higher percentage will eventually lose the ability to walk within a ten-year interval.

Glutathione was studied in two large double-blind placebo-controlled trials and seemed to reduce neurotoxicity without interfering with the therapeutic effect, but shortcomings in the trial designs make confident interpretation of the results impossible. As of September 2013, patients are being recruited for a more definitive study.

In a study of patients receiving oxaliplatin treatment, only 4 percent of those also receiving intravenous calcium and magnesium (ca/mg) before and after each oxaliplatin dose had to discontinue treatment due to neurotoxicity, compared to 33 percent who were receiving intravenous placebo; onset of neuropathy was also significantly delayed in the ca/mg patients, and only 22 percent of the ca/mg patients had long-term CIPN of grade 2 or worse compared with 41 percent of those on placebo. Overall, trials of ca/mg infusion suggest there are no serious harmful side effects and it may be an effective preventative therapy — the number of patients so far studied is small, however, and confident conclusions cannot be drawn.

The treatment of peripheral neuropathy varies based on the cause of the condition, and treating the underlying condition can aid in the management of neuropathy. When peripheral neuropathy results from diabetes mellitus or prediabetes, blood sugar management is key to treatment. In prediabetes in particular, strict blood sugar control can significantly alter the course of neuropathy. In peripheral neuropathy that stems from immune-mediated diseases, the underlying condition is treated with intravenous immunoglobulin or steroids. When peripheral neuropathy results from vitamin deficiencies or other disorders, those are treated as well.

AON is a rare disease and the natural history of the disease process is not well defined. Unlike typical optic neuritis, there is no association with multiple sclerosis, but the visual prognosis for AON is worse than typical optic neuritis. Thus AON patients have different treatment, and often receive chronic immunosuppression. No formal recommendation can be made regarding the best therapeutic approach. However, the available evidence to date supports treatment with corticosteroids and other immunosuppressive agents.

Early diagnosis and prompt treatment with systemic corticosteroids may restore some visual function but the patient may remain steroid dependent; vision often worsens when corticosteroids are tapered. As such, long-term steroid-sparing immunosuppressive agents may be required to limit the side-effects of steroids and minimize the risk of worsening vision.

The severity of symptoms vary widely even for the same type of CMT. There have been cases of monozygotic twins with varying levels of disease severity, showing that identical genotypes are associated with different levels of severity (see penetrance). Some patients are able to live a normal life and are almost or entirely asymptomatic. A 2007 review stated that "Life expectancy is not known to be altered in the majority of cases".

"...Despite its rarity, the patient's ethnic background and the typical radiographic findings should prompt the clinicians to include NBD in the differential diagnosis of optic neuritis and demyelinating disease in the young..."[5]. This quote indicates that even common symptoms such as headache should be recognized as the sign for possible NBD considering the patient's ethnic background.

Among the methods of diagnosing tropical spastic paraparesis are MRI (magnetic resonance imaging) and lumbar puncture (which may show lymphocytosis).

In 1993, Peter James Dyck divided HSAN I further into five subtypes HSAN IA-E based on the presence of additional features. These features were thought to result from the genetic diversity of HSAN I (i.e. the expression of different genes, different alleles of a single gene, or modifying genes) or environmental factors. Molecular genetic studies later confirmed the genetic diversity of the disease.

CMT can be diagnosed through symptoms, through measurement of the speed of nerve impulses (nerve conduction studies), through biopsy of the nerve, and through DNA testing. DNA testing can give a definitive diagnosis, but not all the genetic markers for CMT are known. CMT is first noticed when someone develops lower leg weakness, such as foot drop; or foot deformities, including hammertoes and high arches. But signs alone do not lead to diagnosis. Patients must be referred to a physician specialising in neurology or rehabilitation medicine. To see signs of muscle weakness, the neurologist asks patients to walk on their heels or to move part of their leg against an opposing force. To identify sensory loss, the neurologist tests for deep tendon reflexes, such as the knee jerk, which are reduced or absent in CMT. The doctor also asks about family history, because CMT is hereditary. The lack of family history does not rule out CMT, but helps rule out other causes of neuropathy, such as diabetes or exposure to certain chemicals or drugs.

In 2010, CMT was one of the first diseases where the genetic cause of a particular patient's disease was precisely determined by sequencing the whole genome of an affected individual. This was done by the scientists employed by the Charcot Marie Tooth Association (CMTA) Two mutations were identified in a gene, SH3TC2, known to cause CMT. Researchers then compared the affected patient's genome to the genomes of the patient's mother, father, and seven siblings with and without the disease. The mother and father each had one normal and one mutant copy of this gene, and had mild or no symptoms. The offspring that inherited two mutant genes presented fully with the disease.

Patients with hereditary motor and sensory neuropathies are diagnosed through a physical evaluation that looks for muscle atrophy, weakness, and sensory responses. In addition to this, EMG (electromyography) and motor nerve conduction tests can help clinicians decide what type of motor and sensory neuropathy it is and how severe the disease is. Final confirmation can come through genetic testing.