Regional Cerebral Blood Flow Abnormalities in Neurosyphilis: A Pilot SPECT Study

Meningovascular and parenchymal neurosyphilis showing more extensive inflammatory lesions on 18F-THK5351 PET than MRI

This manuscript complements the clinical course of the first case of neurosyphilis in our previous report (Kotani. et al. Clin Nuc Med 2024) which highlighted the utility of 18F-THK5351 positron emission tomography (PET), a marker of astrogliosis, to visualize neuroinflammation. The patient was a right-handed man in his early 60s who presented with a three-month history of forgetfulness and subsequent right hemiparesis. Neurological and neuropsychological examinations revealed the right pyramidal signs and impairments in attention, memory, executive function, visuospatial cognition, and verbal fluency. The patient was diagnosed with neurosyphilis based on positive tests for syphilis antibodies in the serum and cerebrospinal fluid (CSF) and elevated CSF cell and protein levels. MRI revealed multiple infarcted lesions that explained the pyramidal signs; however, the lesions responsible for cognitive impairment were not visualized. Two months after penicillin G treatment, the patient exhibited partial improvements in cognitive function, without obvious changes in MRI. To investigate the underlying neuroinflammation associated with astrogliosis, we performed PET imaging after treatment. 18F-THK5351 PET revealed increased uptake and 18F-fluorodeoxyglucose (FDG) PET showed decreased uptake in the left deep frontal white matter and thalamus. We believed that the right pyramidal signs were associated with infarctions contributed by meningovascular syphilis in addition to the arteriosclerosis, whereas cognitive impairment was associated with neuroinflammation due to parenchymal syphilis. Furthermore, the impairment of thalamocortical circuits may have compromised the widespread cortical excitability underlying cognitive impairments. This report highlights the utility of 18F-THK5351 PET imaging in understanding the pathogenesis of neurosyphilis, including cognitive impairment. Further longitudinal studies are required to elucidate the relationship between neuroinflammation and the clinical presentation of neurosyphilis.

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.

Selective attention function impairment in HIV-negative patients with early forms of neurosyphilis

BACKGROUND

The attentional network test (ANT) is widely used to evaluate the performance of three attentional networks: alerting, orienting and executive attention networks. This study aimed to investigate the characteristics of attention functions in HIV-negative patients with early forms of neurosyphilis (NS) and their correlation with abnormalities in brain magnetic resonance imaging (MRI).

METHODS

Thirty patients with early forms of NS, 31 patients with syphilis but without NS (Non-NS) and 35 healthy controls were recruited from an HIV-negative cohort between September 2020 and November 2022. The participants were evaluated with the ANT and the Mini-Mental State Examination (MMSE). Brain MRI was performed in NS and Non-NS patients.

RESULTS

No significant differences were observed in the MMSE scores among the three groups. However, patients with early forms of NS showed poorer performance in orienting and alerting functions than Non-NS group (F = 6.952, P = 0.011 and F = 8.794, P = 0.004, respectively); No significant difference was observed in executive function between the two groups (F = 0.001, P = 0.980). Multivariate analysis of variance using the Bonferroni post hoc test indicated that patients with NS exhibited less efficient orienting function (P = 0.023), and alerting function (P = 0.003) but not executive function (P = 0.99), compared to Non-NS patients. Additionally, a significant difference was found in orienting function between patients with NS and healthy controls (P < 0.001) compared to healthy controls. MRI scans revealed that the NS group had a higher prevalence of abnormalities in the frontal lobes and/or the temporoparietal junction compared to the Non-NS group (24/25 vs. 13/19, P = 0.032).

CONCLUSIONS

The orienting and alerting functions but not executive function were significantly less efficient in early forms of NS group than in the Non-NS group (P < 0.01). This indicates deficits in selective attention in patients with early forms of NS. Brain MRI scans revealed abnormalities in the frontal and/or parietal lobes, as well as the temporoparietal junction, suggesting potential neuropathological correlates of these attentional deficits.

Novel and characteristic radiological features of neurosyphilis: a case series

BACKGROUND

Treponema pallidum can invade the central nervous system (CNS) early in its infection, causing neurosyphilis. Neurosyphilis typically presents with meningovasculitis in the acute or subacute phase, while tabes dorsalis and dementia paralytica are classical conditions in the later stages. However, syphilis is often misdiagnosed as other conditions such as tumors or autoimmune diseases including vasculitis and encephalitis, which is why the condition is known as "The Great Mimicker." The increasing incidence of syphilis in recent years emphasizes the importance of early diagnosis and treatment; however, its multiple clinical manifestations impose diagnostic challenges for clinicians because it resembles other diseases. In this case series, we present the impressive manifestations of neurosyphilis through three unique radiological presentations.

CASE PRESENTATION

Case 1 details optic nerve involvement in an HIV-positive male, where MRI and fundoscopic findings confirmed syphilitic optic neuritis. Case 2 describes a patient in her pregnancy initially suspected of acoustic neuroma on MRI, later diagnosed with syphilitic gumma affecting the inner ear canal. Case 3 is a young male with clinical features mimicking temporal arteritis, ultimately identified as skull osteomyelitis secondarily causing inflammation of the musculus temporalis and meningitis.

CONCLUSIONS

These cases underscore the necessity of considering syphilis in differential diagnoses, given the diversity of its clinical presentations. Radiology plays an important role in avoiding unnecessary interventions. The increasing prevalence of recurrent syphilis imposes diagnostic challenges, emphasizing the importance of the early diagnosis and treatment of neurosyphilis by clinicians.

Aberrant gray matter structure in neurosyphilis without conventional MRI abnormality: a pilot study with voxel and surface-based morphology

Background

The underlying mechanism of neurosyphilis was not fully understood.

Purpose

To assess gray matter (GM) microstructure in patients with early-stage neurosyphilis without overt conventional magnetic resonance imaging (MRI) abnormality using voxel-based morphometry (VBM) and surface-based morphometry (SBM) analyses.

Material and Methods

Three-dimensional high-resolution T1-weighted imaging data from 19 individuals with neurosyphilis and 19 healthy controls were analyzed. A battery of neuropsychological tests was performed before each MRI examination. The differences of GM volume and cerebral cortical morphological data between the two groups were compared. The correlations between MRI metrics and neuropsychology/laboratory tests in the patient group were investigated.

Results

Regional decreased GM volumes in patients with neurosyphilis were found in the left frontal cortices (Rolandic operculum, middle frontal, and precentral) and bilateral temporal/occipital cortices (bilateral middle temporal, left lingual, and right middle occipital) ( P < 0.05, FDR correction). SBM analysis showed significant cortical thickness reduction in the right medial orbitofrontal lobe, and reduced gyrification index in the left insula in patients with neurosyphilis ( P < 0.05, FDR correction). Additionally, in the patient group, the GM volume in the middle frontal gyrus, the cortical thickness of right medial orbitofrontal lobe, and the gyrification index in the left insula were negatively correlated to the number connection test-A scores. The gyrification index was also negatively correlated to cerebrospinal fluid white blood cell count.

Conclusion

Early-stage neurosyphilis without conventional MRI abnormality presented regional GM volume reduction and cortical morphological changes, which might be related to cognitive impairment and intra-cranial infection. VBM and SBM analyses might be useful for understanding the underlying neural trait of neurosyphilis.