Hypertrophic Pachymeningitis Mimicking Hemorrhage

A 54-year-old female patient presented to the neurology department with a 3-month history of persistent headache and visual decline, which had worsened over the past 3 days. Neurological examination indicated decreased visual acuity and reduced muscle strength in the right upper limb. Her routine laboratory tests showed an elevated neutrophil level: 6.87 × 109, C-reactive protein 68.48 mg/L, and antinuclear antibody (ANA) (+). Cerebrospinal fluid (CSF) examination showed an elevated protein level of 790 mg/L. Plain CT [Figure 1] revealed prominent high-density (CT value = 70 HU) areas within the cerebral falx and tentorium cerebelli, mimicking the radiological appearance of acute or subacute subdural hematoma. Given the rarity of subdural hematomas occurring simultaneously above and below the tentorium, the patient was referred for magnetic resonance imaging to further evaluate the condition. Cross-sectional MRI [Figure 2] showed thickening of meninges in the cerebral hemisphere and cerebellum, with isointensity in T1-weighted images and hypointensity in T2-weighted and Fluid-attenuated inversion recovery (FLAIR) images. The DWI sequence reveals no abnormal signal intensity in the region of the cerebral falx and tentorium cerebelli. The gadolinium enhanced T1-weighted images revealed enhancement of the thickened dura mater, with significant areas in the cerebral falx and tentorium cerebelli, which was similar to the “Eiffel Tower Night View Sign” in the coronal position.[1] The patient was administered a 10-day course of high-dose methylprednisolone pulses (1000 mg/day), after that clinical symptoms stabilized and no further deterioration was observed during follow-up.Figure 1: Axial non enhanced CT revealed hyperintense areas within the falx cerebri (b) and tentorium cerebelli (a) which appeared similar to hemorrhagic changesFigure 2: Axial MRI images showed thickening of meninges with isointensity in T1-weighted images (a) and hypointensity in T2-weighted images (b). The DWI sequence reveals no abnormal signal intensity (c). Gadolinium-enhanced T1-weighted axial (d, e) and coronal (f) images showed extensive meningeal thickening and enhancement dura mater, with significant areas in the cerebral falx and tentorium cerebelli, which was like the “Eiffel Tower Night View Sign” in the coronal positionHypertrophic pachymeningitis (HP) is a rare condition characterized by the thickening of the dura mater, which can occur due to a variety of underlying etiologies, including infections, autoimmune diseases, and malignancies. The pathophysiology of HP involves chronic inflammation leading to fibrosis of the dura mater, which can result in significant neurological deficits depending on the location and extent of the involvement. The epidemiology of HP is not well-defined, but it is often associated with systemic conditions such as granulomatosis with polyangiitis, tuberculosis, and IgG4-related disease, making its diagnosis particularly challenging in clinical practice.[2,3] Clinically, patients with HP may present with a range of symptoms, including headaches, neurological deficits, and signs of increased intracranial pressure. These symptoms can be nonspecific and may overlap with other neurological disorders, complicating the diagnostic process. In our case, non-contrast enhanced CT scans showed a diffuse, high-density lesion along the cerebral falx and tentorium cerebelli, mimicking a subdural hemorrhage. Contrast-enhanced MR images demonstrates the high-density lesion is thick and homogeneous enhancement of the dura mater. This appearance is believed to be associated with various pathological conditions, such as chronic inflammation characterized by lymphocytic infiltration, extensive fibrosis accompanied by plasma cell invasion, and scattered eosinophils.[4] A limitation of this report is the lack of SWI/GRE images, which may be crucial for differentiating hemorrhage from other conditions. Contrast-enhanced MRI is recognized as the most sensitive diagnostic imaging modality for detecting meningeal thickening and enhancement patterns that are characteristic of HP, particularly when differentiating it from subdural hemorrhage poses a diagnostic challenge. However, the differential diagnosis remains broad, encompassing infectious, inflammatory, and neoplastic processes, which necessitates a thorough evaluation to establish an accurate diagnosis. In this case, the imaging findings revealed significant meningeal enhancement, aligning with the classical presentations documented in existing literature.[4] The use of advanced imaging techniques, such as MRI with contrast, has proven crucial in identifying meningeal inflammation that might otherwise remain undetected. Declaration of patient consent The authors certify that they have obtained all appropriate patient consent forms. In the form the patient has given his consent for his images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed. Institutional review board Ethics committee of Hospital of Chengdu University of Traditional Chinese Medicine. Approval number: 2024KL-035. Approval date: Jan. 8, 2025. Financial support and sponsorship Nil. Conflicts of interest There are no conflicts of interest.