Neurosyphilis in disguise

Clinical and Imaging Features of Syphilis from Head to Toe

Syphilis, a bacterial infection caused by Treponema pallidum, is resurging globally. It is classified as acquired or congenital syphilis. Acquired syphilis progresses through primary, secondary, and tertiary stages. Pathologically, acquired syphilis is characterized by vasculopathy, perivascular infiltrates in syphilitic lesions, and reactive lymphadenopathy. Primary and secondary syphilis frequently manifest with cutaneous and mucosal lesions accompanied by extensive lymphadenopathy at the initial sites of sexual contact, such as the genitalia, oropharynx, and anorectum. These manifestations may mimic malignancies. Tertiary syphilis encompasses cardiovascular syphilis, late neurosyphilis, and gummas, each manifesting distinct imaging characteristics. Most acquired cases are suspected on the basis of dermatologic signs and patient history and are confirmed serologically. Imaging findings alone may not be diagnostic and can overlap with those of other infectious, inflammatory, or neoplastic conditions, necessitating clinical correlation and laboratory testing. However, in patients with atypical clinical presentations, imaging has an important role in providing valuable diagnostic clues and guiding appropriate clinical treatment. The incidence of congenital syphilis is also increasing in parallel with the overall increase in syphilis infections. A comprehensive understanding of the diverse imaging manifestations in multiple organ systems is vital for radiologists to accurately diagnose and guide appropriate management in the era of resurgent syphilis. The authors provide an overview of acquired and congenital syphilis, detailing the epidemiologic and pathophysiologic characteristics, diagnostic approaches, clinical courses, and imaging features. ©RSNA, 2025 Supplemental material is available for this article.

Unmasking the hidden culprit: neurosyphilis mimicking parkinsonism in a middle-aged male

BACKGROUND

General paresis, a tertiary manifestation of neurosyphilis affecting the brain, is characterized by mental and behavioral disorders, such as attention disorder, cognitive impairment, and personality changes. But parkinsonism is rarely reported in patients with neurosyphilis, let alone general paresis. This study reports a case suffering from both general paresis and parkinsonism.

CASE PRESENTATION

A 50-year-old man was initially misdiagnosed with "alcohol-related psychiatric and behavioral disorders" due to the onset of psychiatric symptoms following alcohol abstinence. The excessive administration of psychotropic medications, attributed to their limited efficacy, was identified as the primary cause of his subsequent extrapyramidal symptoms, including tremor and bradykinesia. However, treatment with levodopa yielded only marginal effectiveness. Following a comprehensive diagnostic evaluation, which encompassed brain magnetic resonance imaging, syphilis screening, and cerebrospinal fluid analysis, neurosyphilis was ultimately identified as the underlying etiology. Subsequent treatment with aqueous penicillin resulted in a marked improvement in his symptoms.

CONCLUSION

This case illustrates a rare manifestation of neurosyphilis, specifically parkinsonism. The diagnostic process was complicated by several confounding factors. As neurosyphilis is known as the "great imitator," capable of mimicking various neuropsychiatric disorders, routine syphilis screening is imperative for patients presenting with mental disorders and parkinsonian symptoms to facilitate early diagnosis and enhance prognosis.

Neutrophil-related indicators as potential peripheral blood biomarkers for the diagnosis of neurosyphilis: a cross-sectional study

BACKGROUND

Neurosyphilis (NS) is the most serious complication elicited by the invasion of Treponema pallidum (T. pallidum) into the central nervous system. Identifying the neuro-invasion of T. pallidum as early as possible is important. Looking for indicators with good performance and convenient to operate is in great demand for the diagnosis of NS.

METHODS

A cross-sectional study was conducted on 428 human immunodeficiency virus (HIV)-negative syphilis patients who underwent therapy in Shanghai Skin Disease Hospital from April 2022 to June 2023. The syphilis patients were further grouped into non-neurosyphilis (NNS), asymptomatic neurosyphilis (ANS) and symptomatic syphilis (SNS). Laboratory examination results of these patients were analyzed.

RESULTS

Significantly elevated neutrophil CD64 (nCD64) index and neutrophil to lymphocyte ratio (NLR) were observed in ANS and SNS patients compared with those of NNS patients. nCD64 index and NLR were strongly correlated with serum and cerebrospinal fluid (CSF) TRUST titer, CSF WBC and CSF protein levels in NS patients. nCD64 index and NLR were independent factors influencing NS, especially ANS. Logistic regression models based on nCD64 index, NLR and serum TRUST titer exhibited better diagnostic performances to the currently used markers in NS diagnosis. Particularly, for NS patients with negative CSF TRUST, diagnostic performance of the combined nCD64 and NLR was obviously superior to CSF protein and CSF WBC.

CONCLUSIONS

Neutrophil-related indicators-nCD64 index and NLR have potential application value in the diagnosis of NS, especially for the CSF TRUST negative patients.

Analysis of Neurosyphilis Imaging Methods and Treatment: A Focused Review

Neurosyphilis, a severe complication of syphilis caused by Treponema pallidum, progresses through multiple stages, including asymptomatic, meningeal, meningovascular, and late parenchymal forms such as syphilitic paresis and tabes dorsalis. Neurosyphilis spreads through sexual contact and from mother to child. Symptoms of neurosyphilis include nausea, cranial nerve deficiencies, and seizures. Diagnosing this condition is particularly challenging due to its varied symptoms, which frequently overlap with other neurological disorders. Current diagnostic approaches primarily rely on cerebrospinal fluid (CSF) analysis and neuroimaging techniques like magnetic resonance imaging (MRI) and single-photon emission computed tomography (SPECT). The exploration of recent advances in neurosyphilis testing and the expanding role of imaging techniques in tracking treatment efficacy are seen. Penicillin G continues to be the primary treatment, with ceftriaxone serving as an alternative for patients with penicillin allergies. Even though ceftriaxone is less potent than penicillin G, it can still successfully eradicate neurosyphilis in patients. This review seeks to deepen the understanding of neurosyphilis pathophysiology, refine diagnostic accuracy, and inform evidence-based treatment approaches. This will ultimately contribute to improved patient outcomes.

Neurosyphilis complicated by anti-γ-aminobutyric acid-B receptor encephalitis: A case report

BACKGROUND

Syphilis is an infectious disease caused by Treponema pallidum that can invade the central nervous system, causing encephalitis. Few cases of anti-N-methyl-D-aspartate receptor autoimmune encephalitis (AE) secondary to neurosyphilis have been reported. We report a neurosyphilis patient with anti-γ-aminobutyric acid-B receptor (GABABR) AE.

CASE SUMMARY

A young man in his 30s who presented with acute epileptic status was admitted to a local hospital. He was diagnosed with neurosyphilis, according to serum and cerebrospinal fluid (CSF) tests for syphilis. After 14 d of antiepileptic treatment and anti-Treponema pallidum therapy with penicillin, epilepsy was controlled but serious cognitive impairment, behavioral, and serious psychiatric symptoms were observed. He was then transferred to our hospital. The Mini-Mental State Examination (MMSE) crude test results showed only 2 points. Cranial magnetic resonance imaging revealed significant cerebral atrophy and multiple fluid-attenuated inversion recovery high signals in the white matter surrounding both lateral ventricles, left amygdala and bilateral thalami. Anti-GABABR antibodies were discovered in CSF (1:3.2) and serum (1:100). The patient was diagnosed with neurosyphilis complicated by anti-GABABR AE, and received methylprednisolone and penicillin. Following treatment, his mental symptoms were alleviated. Cognitive impairment was significantly improved, with a MMSE of 8 points. Serum anti-GABABR antibody titer decreased to 1:32. The patient received methylprednisolone and penicillin after discharge. Three months later, the patient's condition was stable, but the serum anti-GABABR antibody titer was 1:100.

CONCLUSION

This patient with neurosyphilis combined with anti-GABABR encephalitis benefited from immunotherapy.

Neurosyphilis: insights into its pathogenesis, susceptibility, diagnosis, treatment, and prevention

Background and aim

Invasion of the central nervous system by Treponema pallidum can occur at any stage of syphilis. In the event that T. pallidum is not cleared promptly, certain individuals may experience progression to neurosyphilis, which manifests as cognitive and behavioral abnormalities, limb paralysis, and potentially fatal outcomes. Early identification or prevention of neurosyphilis is therefore crucial. The aim of this paper is to conduct a critical and narrative review of the latest information focusing exclusively to the pathogenesis and clinical management of neurosyphilis.

Methodology

To compile this review, we have conducted electronic literature searches from the PubMed database relating to neurosyphilis. Priority was given to studies published from the past 10 years (from 2013 to 2023) and other studies if they were of significant importance (from 1985 to 2012), including whole genome sequencing results, cell structure of T. pallidum, history of genotyping, and other related topics. These studies are classic or reflect a developmental process.

Results

Neurosyphilis has garnered global attention, yet susceptibility to and the pathogenesis of this condition remain under investigation. Cerebrospinal fluid examination plays an important role in the diagnosis of neurosyphilis, but lacks the gold standard. Intravenous aqueous crystalline penicillin G continues to be the recommended therapeutic approach for neurosyphilis. Considering its sustained prominence, it is imperative to develop novel public health tactics in order to manage the resurgence of neurosyphilis.

Conclusion

This review gives an updated narrative description of neurosyphilis with special emphasis on its pathogenesis, susceptibility, diagnosis, treatment, and prevention.

Neurosyphilis Presenting as Syndrome of Limbic Encephalitis Mimicking Herpes Simplex Virus Neuro-Infection Diagnosed Using CXCL13 Point-of-Care Assay—Case Report

The syndrome of limbic encephalitis is a severe clinical condition with heterogenous aetiopathogenesis. A common pathogen causing the infectious syndrome of limbic encephalitis is herpes simplex virus (HSV), but rare cases caused by Treponema pallidum have also been reported. We present the case of a 46-year-old man who presented with sudden onset of headaches, nausea, vomiting, and short-term loss of consciousness with clonic convulsions and subsequent disorientation and aphasia. Examination of the cerebrospinal fluid (CSF) revealed lymphocytic pleocytosis and magnetic resonance of the brain revealed bilateral temporal lesions. Clinical, radiologic, and biochemical examinations of CSF suggested encephalitis caused by HSV. However, the positivity of CXCL-13 chemokine in the CSF by a rapid point-of-care assay suggested active spirochetal infection and led to further serologic investigation. The definitive diagnosis of neuro-syphilis was concluded by positive intrathecal synthesis of immunoglobulins against Treponema pallidum. Penicillin therapy led to a rapid improvement, and the patient was discharged home after three weeks. Due to memory problems and irritability, after eighteen months, he came for a follow-up neurological and psychological examination. The psychological examination revealed a significant deficit in executive functions and behavioural changes. Neurosyphilis should be considered in the differential diagnosis of limbic encephalitis with lymphocytic pleocytosis in cerebrospinal fluid, and CXCL-13 may help to achieve diagnosis.

Imaging features of neurosyphilis

Syphilis is an infectious disease caused by the spirochete Treponema pallidum, subspecies pallidum. Although its incidence has declined after the widespread availability of penicillin, it has recently re-emerged, especially in men who have sex with men and in people living with human immunodeficiency virus (HIV). The neurological manifestations of syphilis, generally known as neurosyphilis, may appear at any time during the infection, including the initial years after the primary infection. Neurosyphilis can be asymptomatic, only with cerebrospinal fluid abnormalities, or symptomatic, characterized by several different clinical syndromes, such as meningitis, gumma, meningovascular, brain parenchyma involvement, meningomyelitis, tabes dorsalis, and peripheral nervous system involvement. However, these syndromes may simulate several other diseases, making the diagnosis often a challenge. In addition, syphilis can also be vertically transmitted from mother to child during pregnancy, leading to neurological manifestations. Neuroimaging is essential to demonstrate abnormal brain or spinal cord findings in patients with neurosyphilis, aiding in the diagnosis, treatment, and follow-up of these patients. This article aims to review the imaging features of neurosyphilis, including the early and late stages of the infection.

MRI of neurosyphilis with mesiotemporal lobe lesions of "knife-cut sign” on MRI: A case report and literature review

Neurosyphilis with mesiotemporal lobe lesions remains a difficult entity to diagnose, especially when it mimics herpes simplex encephalitis (HSE). Here, we report what appeared to be the first case of mesiotemporal imaging of neurosyphilis presenting as a "knife-cut" sign and mimicking HSE pathological hallmarks on imaging. The magnetic resonance imaging (MRI) changes in neurosyphilis and HSE were indistinguishable in the initial diagnosis because of the common involvement of the mesiotemporal lobe. Neurosyphilis was diagnostically confirmed by positive readings in the treponema pallidum hemagglutination assay (TPHA), rapid plasma reagin (RPR) and cerebrospinal fluid-polymerase chain reaction (CSF-PCR) tests for Treponema pallidum infection. Neurosyphilis and HSE had similar clinical features and signs on MRI, except the knife-cut sign which is a common diagnosis in HSE. Therefore, neurosyphilis with mesiotemporal changes and knife-cut signs on MRI should be evaluated in the differential diagnosis in all patients, as similar changes may also occur in HSE patients. The literature review of published articles between 1997 and 2020 was conducted to further validate our clinical observations and discuss diagnostic and treatment options for neurosyphilis with mesiotemporal lobe lesions.

68Ga-FAPI PET/CT Imaging of Intracranial Syphilitic Gumma: Comparison to 18F-FDG PET/CT

ABSTRACT

Intracranial syphilitic gumma is a rare neurological disease. We present 68Ga-DOTA-FAPI-04 and 18F-FDG PET/CT findings of intracranial syphilitic gumma in a 46-year-old man with HIV. In this case, 68Ga-DOTA-FAPI-04 PET/CT outperforms 18F-FDG in helping to visualizing syphilitic gumma. Syphilitic gumma can also cause increase FAPI activity. Our findings suggest the potential value of 68Ga-DOTA-FAPI-04 in the diagnosis of syphilis.

Alzheimer's Disease and Neurosyphilis: Meaningful Commonalities and Differences of Clinical Phenotype and Pathophysiological Biomarkers

BACKGROUND

Neurosyphilis-associated cognitive and behavioral impairment- historically coined as "general paralysis of the insane"- share clinical and neuroradiological features with the neurodegenerative disease spectrum, in particular Alzheimer's disease (AD). Anatomopathological similarities have been extensively documented, i.e., neuronal loss, fibrillary alterations, and local amyloid-β deposition. Consequently, accurate classification and timely differential diagnosis may be challenging.

OBJECTIVE

To describe clinical, bio-humoral, brain MRI, FDG-PET, and amyloid-PET features in cases of neurosyphilis with an AD-like phenotypical presentation, as well as clinical outcome in terms of response to antibiotic therapy.

METHODS

We selected the studies comparing patients with AD and with neurosyphilis associated cognitive impairment, to investigate candidate biomarkers classifying the two neurological diseases.

RESULTS

The neuropsychological phenotype of general paralysis, characterized by episodic memory impairment and executive disfunction, substantially mimics clinical AD features. Neuroimaging often shows diffuse or medial temporal cortical atrophy, thus contributing to a high rate of misdiagnosis. Cerebrospinal fluid (CSF)-based analysis may provide supportive diagnostic value, since increased proteins or cells are often found in neurosyphilis, while published data on pathophysiological AD candidate biomarkers are controversial. Finally, psychometric testing using cross-domain cognitive tests, may highlight a wider range of compromised functions in neurosyphilis, involving language, attention, executive function, and spatial ability, which are atypical for AD.

CONCLUSION

Neurosyphilis should be considered a potential etiological differential diagnosis of cognitive impairment whenever imaging, neuropsychological or CSF features are atypical for AD, in order to promptly start antibiotic therapy and delay or halt cognitive decline and disease progression.

Cerebrospinal Fluid Changes and Clinical Features of Neurosyphilis Compared with Latent Syphilis Infection in the Central Nervous System: A Cross-Sectional Study

Purpose

At present, there is no gold standard or unified standard for the diagnosis of neurosyphilis, and the rate of misdiagnosis is high. The diagnosis of neurosyphilis is still challenging. This study compared the clinical indicators between neurosyphilis and latent syphilis infection in the central nervous system. The purpose of this study was to provide evidence for the differential diagnosis and prognosis of patients with neurosyphilis and latent syphilis infection of the central nervous system.

Methods

The clinical data of 59 patients with neurosyphilis and 30 patients with latent syphilis infection in the nervous system from 2008 to 2021 were analyzed. The cerebrospinal fluid and serum biochemical markers were evaluated for all patients.

Results

CSF-nucleated cells, CSF-TRUST, CSF-totalprotein and CSF-IgG (P<0.001) were significantly different between neurosyphilis and latent syphilis infection in the central nervous system. CSF-TRUST titer was positively correlated with D-D concentration (r = 0.274, P < 0.05), sodion (r =0.251, P < 0.05), respectively. Glucose concentration is the most unreliable in the diagnosis of neurosyphilis (AUC=0.445, P=0.395), and TRUST combined with nucleated cells and total protein is the most accurate in the diagnosis of neurosyphilis (AUC=0.989, P<0.001).

Conclusion

The combination of TRUST, nucleated cell count and totalprotein detection in CSF can distinguish the patients with neurosyphilis and latent syphilis infection in the central nervous system, which has a significant diagnostic value.