Международный неврологический журнал Том 19, №2, 2023

A cerebrospinal fluid (CSF) analysis is an important diagnostic method to screen for the presence many neurologic diseases. The lumbar puncture with subsequent cerebrospinal fluid analysis is used in bacterial meningitis and meningoencephalitis, multiple sclerosis (MS), autoimmune encephalitis, paraneoplastic neurological syndromes, acute disseminated encephalomyelitis, neuromyelitis optica, mono- and polyneuritis of the cranial nerves, systemic inflammatory/autoimmune processes with the involvement of the nervous system, benign intracranial hypertension, subarachnoid haemorrhage, Creutzfeldt-Jakob disease, Alzheimer’s disease [1].

In inflammatory diseases of the central nervous system (CNS), the process occurs intrathecally; it is the cerebrospinal fluid where an isolated synthesis of immunoglobulins followed by a change in their clonality takes place. The disco-very of oligoclonal bands of immunoglobulin G (IgG) in the CSF was an important step forward in the understanding of MS and other inflammatory diseases of the central nervous system [1, 2]. The separation of IgG molecules produced by different clones of B cells has been impossible until the agarose gel electrophoresis was introduced in 1950 [3, 4]. The key observation which led to the discovery of oligoclonal bands is dated 1959 when Karcher, van Sande, and Lowenthal [4] reported the separation of gamma globulins into fractions using the agarose gel electrophoresis in a patient with subacute sclerosing panencephalitis. In 1960, the same group of researchers found oligoclonal bands in patients with trypanosomiasis, neurosyphilis, and MS [3, 4].

The isoelectric focusing technique with subsequent immunoblotting was developed by Geoff Keir in 1990 [3]. Due to the fact that IgG molecules are visualized as thin bands, the method of isoelectric focusing was named the oligoclonal band assay. The test is qualitative since the band count in the oligoclonal type of immunoglobulin synthesis is not done as it has no clinical significance. The essence of the isoelectric focusing consists in the comparison of clonality of immunoglobulins in the cerebrospinal fluid and in the blood serum because in systemic autoimmune and infectious processes, immunoglobulin penetrates the blood-brain barrier (BBB) to get to both the cerebrospinal fluid and the blood serum. The presence of oligoclonal IgG in the cerebrospinal fluid is not an absolute specific criterion of MS as it can also be found in infectious or autoimmune diseases [2, 4]. For the analysis and interpretation of results of an oligoclonal band test, the classification of synthesis types according to Andersen [5] is used which singles out 5 patterns of the immunoglobulin synthesis:

— type 1 — normal pattern: diffuse polyclonal distribution of IgG in the cerebrospinal fluid and the blood (no intrathecal IgG synthesis);

— type 2 — oligoclonal bands unique to the cerebrospinal fluid (the presence of intrathecal IgG synthesis characteristic of a subacute/chronic immunoinflammatory process in the CNS together with the immune response of the intrathecal distribution);

— type 3 — mixed pattern: the presence of oligoclonal bands unique to the cerebrospinal fluid plus the presence of oligoclonal bands in the cerebrospinal fluid and in the blood (the presence of intrathecal IgG synthesis characteristic of an acute/subacute immunoinflammatory process in the CNS together with a systemic immune response);

— type 4 — mirror pattern: oligoclonal bands in the cerebrospinal fluid and in the blood are identical (no intrathecal IgG synthesis characteristic of a systemic immunoinflammatory process with or without the involvement of the CNS and with a systemic production of oligoclonal bands);

— type 5 — paraprotein pattern: oligoclonal bands in the blood and in the cerebrospinal fluid are identical like in type 4 but are characterized by a regular periodic sequence and a decrease in intensity — monoclonal type (no intrathecal IgG synthesis, the presence of monoclonal gammopathy).

For MS, the synthesis types 2 and 3 are pathognomonic, while type 4 is characteristic of a systemic inflammatory response with the involvement of the BBB in neuroborreliosis, neurosyphilis, Guillain-Barré syndrome, neurologic manifestations of infection with the human immunodeficiency virus (HIV), meningoencephalitides, and tuberculosis. The monoclonal type 5 synthesis is indicative of paraneoplastic processes, while the type 1 synthesis is found in persons with no inflammatory changes in the cerebrospinal fluid. Determining intrathecal IgG synthesis indicators as oligoclonal bands is considered to be the main laboratory criterion of MS as a chronic inflammatory disease [5, 7]. However, an inflammatory immune response in MS occurs only outside the BBB that allows finding IgG in the CSF. As an inflammatory process progresses, the “polyclonal” immune response transforms into the “oligoclonal” one that is caused by an increase in the number of immune cell clones reacting with a certain autoantigen. Therefore, the detection of oligoclonal immunoglobulin is indicative of a chronic autoimmune inflammatory process. Although the presence of oligoclonal IgG bands in the CSF is a frequent phenomenon in patients with MS, it has not been totally clarified yet whether there is a link between them and a white matter lesion, intrathecal or meningeal inflammatory changes, and a clinical course [7–9]. Any transitory or progressing pathological process involving the CNS may have symptoms similar to MS [7]. Thus, a differential diagnosis of MS has to be carried out on a broader set of pathologies, with neurosyphilis being one of them [7, 10].

Damage to the nervous system may be observed at any stage of a syphilitic process development [10, 11]. Neurosyphilis is diagnosed on the basis of clinical manifestations and changes in the CSF as there is no single highly sensitive and specific test to identify this disease [11, 12].

Often, Treponema pallidum, the causative agent of syphilis, also causes neurovascular and/or parenchymal involvement of the nervous system, posing no difficulty in terms of diagnosing. In both cases, pleocytosis with an increase in the gamma globulin level and the presence of oligoclonal bands is observed during a CSF analysis [11, 13]. The presence or absence of plasma antibodies to lipoproteins of treponemas detected using the immunofluorescence reaction has a high sensitivity to syphilis [10, 11]. However, neurosyphilis is known as a “great imitator” and may be manifested in nonspecific complaints, be associated with positive treponemal and negative nontreponemal tests as well as cause nonspecific changes in the CSF [14]. In such cases, the diagnostic search broadens, and neurosyphilis is not an obvious diagnosis. More often, the damage to the nervous system by syphilis develops in young people, males, homosexuals, and people infected with the HIV [11, 14]. Early forms of neurosyphilis develop within a few months during the first several years after initial infection and are characterized by an involvement of the meninges and the blood vessels, while its late forms develop within a few years, decades after the infection, and are characterized by an involvement of the parenchyma of the brain and the spinal cord.

For the detection of syphilis, two types of tests are used: treponemal (the fluorescent treponemal antibody absorption, the Treponema pallidum particle agglutination assay in the CSF, the enzyme-linked immunosorbent assay (ELISA)) and nontreponemal (the rapid plasma reagin (RPR) test or the cardiolipin antibody test), the serological test for syphilis developed by the Venereal Disease Research Laboratory (VDRL), the toluidine red unheated serum test. Nontreponemal tests in patients with the tertiary (late) syphilis may be non-reactive (negative), while treponemal tests remain reactive at all stages of the disease. The gold standard for diagnosing neurosyphilis is the CSF test for syphilis developed by the VDRL (CSF-VDRL); however, its sensitivity varies from 30 to 70 % [11]. A positive CSF-VDRL test confirms the diagnosis of neurosyphilis but a negative result does not exclude this diagnosis either [15].

To identify neurosyphilis, neuroimaging techniques, in particular, the magnetic resonance imaging (MRI) of the brain, are applied as well [16]. Cerebral gummata resembling meningiomas and increased signal intensity in the T2 mode or in the diffusion-weighted mode in one or both medial temporal regions resembling herpetic encephalitis [16, 17] are pathognomonic MRI patterns of neurosyphilis.

Patient B., a Caucasian male aged 40 years, has sought medical attention at the Department of Neurology 1 of the Mechnikov Dnipropetrovsk Regional Clinical Hospital in September 2018 complaining of pronounced weakness in the lower limbs, disturbance of movements in them, gait disorder, feeling of numbness in the limbs. As known from the medical records and the anamnestic data, the patient considers himself to be ill since the end of August — beginning of September 2018 when, not having any health problems, he started to experience the symptoms of weakness in the lower limbs. He consulted a doctor in his place of residence (Kyiv) and was sent to an examination — MRI of the brain and the cervical spinal cord with contrast enhancement. As a result of the conducted study, the foci of a hyperintense MR signal in the T2 and FLAIR modes and of an isointense one — in the T1 mode have been found in the right cerebral hemisphere (Fig. 1) and at the level of C4-C5 segments of the cervical spinal cord.

After relocation, the patient sought medical attention at the Mechnikov Dnipropetrovsk Regional Clinical Hospital and was hospitalized to the Department of Neurology 1. Upon admission to the hospital, his neurological status was as follows: the consciousness is clear, the speech is preserved, the cranial nerves are intact; the muscle strength: in the upper limbs: D — 5 points, S — 5 points, in the lower limbs: D — 2.5–3 points, S — 2.5–3 points; the tendon and periosteal reflexes of the upper limbs: S = D, overactive; of the lower limbs — D = S, high; the foot clonuses are caused on 2 sides; the Babinski, Oppenheim, Schaeffer, and Chaddock reflexes are present on 2 sides; the muscle tone in the upper limbs: D = S, unchanged, in the lower limbs: D = S, slightly increased due to spasticity; the symptoms of an extrapyramidal system lesion are not observed; the sphere of coordination: the finger-to-nose test is satisfactory, the heel-to-shin test cannot be performed due to the severity of paresis in the lower limbs; the patients is unable to maintain the standing position in the Romberg’s test; a decrease in the superficial and deep sensitivity below the C3 innervation level on 2 sides; the meningeal symptoms are absent; the pelvic viscera functions are not disturbed; the patient’s walking is assisted, he cannot walk on his own due to the severity of paresis in the lower limbs.

Based on the clinical and radiological picture, a conclusion that the patient had the onset of a demyelinating disease was made according to the McDonald criteria 2017. The treatment was carried out: pulse therapy with the administration of methylprednisolone 1000 mg by intravenous infusions for 5 days. As a result of the treatment, a pronounced positive dynamics expressed in an increase in the muscle strength of the lower limbs to 4 points was observed.

A re-deterioration in the patient’s condition has been observed in February 2019 when, being otherwise healthy, he again complained of pronounced weakness in the lower limbs, disturbance of movements in them, coordination and balance disorder worsening at night, a pronounced gait disorder. The patient was rehospitalized to the Department of Neurology 1 of the Mechnikov Dnipropetrovsk Regional Clinical Hospital. Upon admission, his neurological status was as follows: the consciousness is clear, the speech is preserved, the cranial nerves — horizontal nystagmus; the muscle strength in the upper limbs: D — 5 points, S — 5 points, in the lower limbs: D — 3 points, S — 3 points; the tendon and periosteal reflexes of the upper limbs: 

S = D, overactive; of the lower limbs: D = S, high; the foot clonuses are caused on 2 sides; the Babinski sign is pre-sent on 2 sides; the muscle tone in the upper limbs: D = S, unchanged, in the lower limbs: D = S, slightly increased due to spasticity; the symptoms of an extrapyramidal system lesion are not observed; the sphere of coordination: the finger-to-nose test is performed with dysmetria, the heel-to-shin test is performed with dysmetria, dysmetria is aggravated in the absence of visual control; extremely unstable when standing during the Romberg’s test; a decrease in the superficial and deep sensitivity below the C3 innervation level on 2 sides, the deep sensitivity is more reduced; the meningeal symptoms are absent; the pelvic viscera functions are not disturbed; the patient moves using a walking stick, notices considerable difficulties when walking in the dark and with the eyes shut. An exacerbation of multiple sclerosis was assumed and, to verify it, the patient underwent an MRI examination with contrast enhancement and the hyperintense foci in the T2 and FLAIR modes localized in both brain hemispheres have been found (Fig. 2). Also, a focus has been detected accumulating a contrast agent at the level of C2-C3 spinal cord segments in the T1 mode (Fig. 3).

In view of such a radiological picture, a decision was made to carry out an in-depth examination and further diagnostic search: an analysis of the CSF and blood plasma to detect oligoclonal antibodies (01.03.2019). Analysis of oligoclonal bands has revealed type 4 synthesis which is indicative of the presence of high-affinity (“mirror”) oligoclonal antibodies in the cerebrospinal fluid and blood plasma. As this picture of oligoclonal bands is not typical of demyelinating diseases and is more characteristic of systemic inflammatory processes that are autoimmune or infectious in nature, the decision to continue the diagnostic search has been made. For this purpose, the following diagnostic tests have been carried out:

— a blood test for HIV infection (06.03.2019): the result is negative;

— a blood test for antinuclear antibodies (06.03.2019): the result is negative;

— a blood test for the presence of antibodies to Borrelia burgdorferi antigens using the blotting method (06.03.2019): antibodies to the р41 protein are found.

It should be noted that during the first hospitalization (in September 2018) and the current hospitalization, the patient underwent a series of serological tests, including Wassermann reaction and the microprecipitation reaction with the cardiolipin antigen (RPR) whose results were negative. However, considering the clinical picture that shows lower limb paraparesis, coordination disorders with the prevalence of sensory ataxia phenomena, neuroimaging data, the pre-sence of type 4 IgG synthesis in the serum and blood (cha-

racteristic of systemic infections as well), the decision to carry out further examination to detect the presence of syphilis has been made:

— a blood test to detect IgG and IgM to Treponema pallidum using the ELISA (11.03.2019): the result is positive;

— in relation to the latter, a blood test to detect antibo-dies to Treponema pallidum using the immunoblotting me-thod was performed (26.03.2019): the proteins р41, р45, р17, р15 have been found (Fig. 4).

Based on the results of the above-mentioned examinations, the patient has been diagnosed with neurosyphilis. He was sent for further treatment to a dermatovenerologic dispensary in the place of his residence, Kyiv.

The clinical case described above clearly demonstrates a number of clinically significant and topical issues faced by contemporary neurologists. Firstly, it is a problem of differential diagnosis in distinguishing MS and other neurological as well as systemic infectious and non-infectious diseases. The extreme diversity of clinical manifestations of MS, various types of its course and nonspecific changes an MRI examination can reveal often dictate the necessity of a differential diagnosis which sometimes appears to be very difficult. At the same time, a high prevalence of MS in the modern neurological practice compared to other diseases with similar manifestations and changes visua-lized by MRI creates among neurologists a certain prejudice having excessive diagnostic testing of multiple sclerosis as a consequence. In the context of the clinical case reviewed here, a considerable decrease in the incidence and prevalence of syphilitic lesions of the nervous system over the last 50 years has also played an important role which led to a decrease in the watchfulness with respect to this disease among neurologists. Secondly, the mentioned clinical case shows the importance of determining the type of antibody synthesis when carrying out a cerebrospinal fluid analysis with the aim to detect oligoclonal bands because, as stated in the works included in the overview and illustrated by our patient’s example, just confirming the fact of the presence of oligoclonal bands in the CSF is not sufficient for diagnosing MS; moreover, a wrong diagnosis can be made. It means that the interpretation of results of a test aimed at detecting oligoclonal antibodies must always be done taking into consideration the type of antibody synthesis but definitely not in isolation from the clinical picture of a disease, its course, and the results of other diagnostic tests. And finally, the third question which is indirectly touched upon in this case study is the problem of screening tests for syphilis in Ukraine: the tests which are nowadays used for screening (Wassermann reaction, RPR) may at certain stages of syphilis (in particular, in the tertiary stage) yield false-negative results as it was in the case with our patient and led to diagnosing his disease wrongly during the first hospitalization. The verification of a syphilitic process became possible only after the modern highly sensitive and highly specific tests (ELISA, the immunoblotting) have been implemented to analyze the cerebrospinal fluid and to determine the type of antibody production.

Despite a high prevalence of demyelinating diseases of the nervous system (in particular, MS), the probability of that a patient may have a different neurological or systemic disease (of infectious or non-infectious origin) which would explain the clinical picture and neuroimaging changes should be borne in mind. Neurosyphilis is one of these di-seases. The method of a CSF analysis to detect the presence of oligoclonal bands should include the identification of the type of oligoclonal antibody synthesis because it is one of the markers which, in combination with the data obtained through other research methods, may facilitate the process of differential diagnosis of neurosyphilis and MS.

 

Received 20.03.2023

Revised 01.04.2023

Accepted 06.04.2023