In the US, neuroborreliosis is typically treated with intravenous antibiotics which cross the blood–brain barrier, such as penicillins, ceftriaxone, or cefotaxime. One relatively small randomized controlled trial suggested ceftriaxone was more effective than penicillin in the treatment of neuroborreliosis. Small observational studies suggest ceftriaxone is also effective in children. The recommended duration of treatment is 14 to 28 days.

Several studies from Europe have suggested oral doxycycline is equally as effective as intravenous ceftriaxone in treating neuroborreliosis. Doxycycline has not been widely studied as a treatment in the US, but antibiotic sensitivities of prevailing European and US isolates of "Borrelia burgdorferi" tend to be identical. However, doxycycline is generally not prescribed to children due to the risk of bone and tooth damage.

Discreditied or doubtful treatments for neuroborreliosis include:

- Malariotherapy

- Hyperbaric oxygen therapy

- Colloidal silver

- Injections of hydrogen peroxide and bismacine

Neuroimaging is controversial in whether it provides specific patterns unique to neuroborreliosis, but may aid in differential diagnosis and in understanding the pathophysiology of the disease. Though controversial, some evidence shows certain neuroimaging tests can provide data that are helpful in the diagnosis of a patient. Magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT) are two of the tests that can identify abnormalities in the brain of a patient affected with this disease. Neuroimaging findings in an MRI include lesions in the periventricular white matter, as well as enlarged ventricles and cortical atrophy. The findings are considered somewhat unexceptional because the lesions have been found to be reversible following antibiotic treatment. Images produced using SPECT show numerous areas where an insufficient amount of blood is being delivered the cortex and subcortical white matter. However, SPECT images are known to be nonspecific because they show a heterogeneous pattern in the imaging. The abnormalities seen in the SPECT images are very similar to those seen in people with cerebral vacuities and Creutzfeldt–Jakob disease, which makes them questionable.

Several forms of laboratory testing for Lyme disease are available, some of which have not been adequately validated. The most widely used tests are serologies, which measure levels of specific antibodies in a patient's blood. These tests may be negative in early infection as the body may not have produced a significant quantity of antibodies, but they are considered a reliable aid in the diagnosis of later stages of Lyme disease. Serologic tests for Lyme disease are of limited use in people lacking objective signs of Lyme disease because of false positive results and cost.

The serological laboratory tests most widely available and employed are the Western blot and ELISA. A two-tiered protocol is recommended by the Centers for Disease Control and Prevention: the sensitive ELISA test is performed first, and if it is positive or equivocal, then the more specific Western blot is run. The reliability of testing in diagnosis remains controversial. Studies show the Western blot IgM has a specificity of 94–96% for people with clinical symptoms of early Lyme disease. The initial ELISA test has a sensitivity of about 70%, and in two-tiered testing, the overall sensitivity is only 64%, although this rises to 100% in the subset of people with disseminated symptoms, such as arthritis.

Erroneous test results have been widely reported in both early and late stages of the disease, and can be caused by several factors, including antibody cross-reactions from other infections, including Epstein–Barr virus and cytomegalovirus, as well as herpes simplex virus. The overall rate of false positives is low, only about 1 to 3%, in comparison to a false-negative rate of up to 36% in the early stages of infection using two-tiered testing.

Polymerase chain reaction (PCR) tests for Lyme disease have also been developed to detect the genetic material (DNA) of the Lyme disease spirochete. PCR tests are susceptible to false positive results from poor laboratory technique. Even when properly performed, PCR often shows false negative results with blood and cerebrospinal fluid specimens. Hence, PCR is not widely performed for diagnosis of Lyme disease, but it may have a role in the diagnosis of Lyme arthritis because it is a highly sensitive way of detecting "ospA" DNA in synovial fluid.

Culture or PCR are the current means for detecting the presence of the organism, as serologic studies only test for antibodies of "Borrelia". OspA antigens, shedded by live Borrelia bacteria into urine, are a promising technique being studied. The use of nanotrap particles for their detection is being looked at and the OspA has been linked to active symptoms of Lyme. High titers of either immunoglobulin G (IgG) or immunoglobulin M (IgM) antibodies to "Borrelia" antigens indicate disease, but lower titers can be misleading, because the IgM antibodies may remain after the initial infection, and IgG antibodies may remain for years.

Western blot, ELISA, and PCR can be performed by either blood test via venipuncture or cerebrospinal fluid (CSF) via lumbar puncture. Though lumbar puncture is more definitive of diagnosis, antigen capture in the CSF is much more elusive; reportedly, CSF yields positive results in only 10–30% of affected individuals cultured. The diagnosis of neurologic infection by "Borrelia" should not be excluded solely on the basis of normal routine CSF or negative CSF antibody analyses.

New techniques for clinical testing of "Borrelia" infection have been developed, such as LTT-MELISA, although the results of studies are contradictory. The first peer reviewed study assessing the diagnostic sensitivity and specificity of the test was presented in 2012 and demonstrated potential for LTT to become a supportive diagnostic tool. In 2014, research of LTT-MELISA concluded that it is "sensible" to include the LTT test in the diagnostic protocol for putative European-acquired Lyme borreliosis infections. Other diagnostic techniques, such as focus floating microscopy, are under investigation. New research indicates chemokine CXCL13 may also be a possible marker for neuroborreliosis.

Some laboratories offer Lyme disease testing using assays whose accuracy and clinical usefulness have not been adequately established. These tests include urine antigen tests, PCR tests on urine, immunofluorescent staining for cell-wall-deficient forms of "B. burgdorferi", and lymphocyte transformation tests. The CDC does not recommend these tests, and stated their use is "of great concern and is strongly discouraged".

A number of diseases can produce symptoms similar to those of Lyme neuroborreliosis. They include:

- Alzheimer's disease

- Acute disseminated encephalomyelitis

- Viral meningitis

- Multiple sclerosis

- Bell's palsy

Neuroborreliosis presenting with symptoms consistent with amyotrophic lateral sclerosis has been described.

Diagnosis is determined by clinical examination of visible symptoms. Neuroborreliosis can also be diagnosed serologically to confirm clinical examination via western blot, ELISA, and PCR.

Diagnosis is based on the self-reported experiences of the person followed by a clinical assessment. Psychiatric assessment includes a psychiatric history and some form of mental status examination. Since some medical and psychiatric conditions mimic the symptoms of DPD, clinicians must differentiate between and rule out the following to establish a precise diagnosis: temporal lobe epilepsy, panic disorder, acute stress disorder, schizophrenia, migraine, drug use, brain tumour or lesion. No laboratory test for depersonalization-derealization disorder currently exists.

The diagnosis of depersonalization disorder can be made with the use of the following interviews and scales:

The Structured Clinical Interview for DSM-IV Dissociative Disorders (SCID-D) is widely used, especially in research settings. This interview takes about 30 minutes to 1.5 hours, depending on individual's experiences.

The Dissociative Experiences Scale (DES) is a simple, quick, self-administered questionnaire that has been widely used to measure dissociative symptoms. It has been used in hundreds of dissociative studies, and can detect depersonalization and derealization experiences.

The Dissociative Disorders Interview Schedule (DDIS) is a highly structured interview which makes DSM-IV diagnoses of somatization disorder, borderline personality disorder and major depressive disorder, as well as all the dissociative disorders. It inquires about positive symptoms of schizophrenia, secondary features of dissociative identity disorder, extrasensory experiences, substance abuse and other items relevant to the dissociative disorders. The DDIS can usually be administered in 30–45 minutes.

The Cambridge Depersonalization Scale (CDS) is a method for determining the severity of depersonalization disorder. It has been proven and accepted as a valid tool for the diagnosis of depersonalization disorder in a clinical setting. It is also used in a clinical setting to differentiate minor episodes of depersonalization from actual symptoms of the disorder. Due to the success of the CDS, a group of Japanese researchers underwent the effort to translate the CDS into the J-CDS or the Japanese Cambridge Depersonalization Scale. Through clinical trials the Japanese research team successfully tested their scale and determined its accuracy. One limitation is that the scale does not allow for the differentiation between past and present episodes of depersonalization. It should also be noted that it may be difficult for the individual to describe the duration of a depersonalization episode, and thus the scale may lack accuracy. The project was conducted in the hope that it would stimulate further scientific investigations into depersonalization disorder.

Depersonalization disorder is classified differently in the DSM-IV-TR and in the ICD-10: In the DSM-IV-TR this disorder it is seen as a dissociative disorder; in the ICD-10 as an independent neurotic disorder. Whether depersonalization disorder should be characterized as a dissociative disorder can be discussed.

Depersonalization is also a direct symptom of Lyme disease as well as other tick-borne diseases. If depersonalization is suspected a blood-test is required in search of anti-bodies.

Treatment is dependent on the underlying cause, whether it is organic or psychological in origin. If depersonalization is a symptom of neurological disease, then diagnosis and treatment of the specific disease is the first approach. Depersonalization can be a cognitive symptom of such diseases as amyotrophic lateral sclerosis, Alzheimer's, multiple sclerosis (MS), neuroborreliosis (Lyme disease), or any other neurological disease affecting the brain. For those suffering from depersonalization with migraine, tricyclic antidepressants are often prescribed.

If depersonalization is a symptom of psychological causes such as developmental trauma, treatment depends on the diagnosis. In case of dissociative identity disorder or DD-NOS as a developmental disorder, in which extreme developmental trauma interferes with formation of a single cohesive identity, treatment requires proper psychotherapy, and—in the case of additional (co-morbid) disorders such as eating disorders—a team of specialists treating such an individual. It can also be a symptom of borderline personality disorder, which can be treated in the long term with proper psychotherapy and psychopharmacology.

The treatment of chronic depersonalization is considered in depersonalization disorder.

A recently completed study at Columbia University in New York City has shown positive effects from transcranial magnetic stimulation (TMS) to treat depersonalization disorder. Currently, however, the FDA has not approved TMS to treat DP.

A 2001 Russian study showed that naloxone, a drug used to reverse the intoxicating effects of opioid drugs, can successfully treat depersonalization disorder. According to the study: "In three of 14 patients, depersonalization symptoms disappeared entirely and seven patients showed a marked improvement. The therapeutic effect of naloxone provides evidence for the role of the endogenous opioid system in the pathogenesis of depersonalization."