Clinical and radiographic characteristics of patients with non-functioning pituitary adenomas categorized according to their serum prolactin concentration: novel predictors of postoperative transient diabetes insipidus following surgery.

PURPOSE: Non-functioning pituitary adenomas (NFPAs) are often associated with hyperprolactinemia, which is known as the "stalk effect". However, the relationships between hyperprolactinemia and the radiographic characteristics of the tumor that affects the pituitary stalk have not been well characterized. We aimed to identify the differences in the clinical and radiographic characteristics of patients with NFPA, with and without hyperprolactinemia. METHODS: We enrolled 107 patients with NFPA and allocated them to hyperprolactinemia and non-hyperprolactinemia groups using two different cut-off values: (1) the upper limit of the normal reference range, adjusted for sex and menopausal status, and (2) the upper quartile across the cohort, and compared their clinical and radiographic characteristics. These analyses were conducted to clarify the relationship between the "stalk effect" and the postoperative change in antidiuretic hormone secretion. RESULTS: The specific radiographic characteristics of the patients included the presence of a cystic or hemorrhagic tumor and the presence of pituitary stalk deviation, which were more frequent in the patients with hyperprolactinemia. Interestingly, the incidence of postoperative transient diabetes insipidus was statistically significantly higher in the hyperprolactinemia group (≥40 ng/mL) and in the group with radiologic evidence of stalk deviation, which were shown to be independent risk factors on multivariate analysis. CONCLUSION: The presence of a "stalk effect" was associated with a higher risk of postoperative transient diabetes insipidus, reflecting perioperative pituitary stalk dysfunction following NFPA surgery, especially in patients with serum prolactin concentrations ≥40 ng/mL and radiologic evidence of stalk deviation.

Acquired Simple Bone Cyst Associated With Lumbar Spinal Canal Stenosis Progression: A Case Report.

A simple bone cyst (SBC) in the posterior lumbar bone structure is very rare. Here, we report a case of SBC at the L5 lumbar lamina with venous obstruction associated with ligamentum flavum thickening. A 59-year-old woman presented with intermittent claudication due to low back pain and bilateral sciatica. A lumbar MRI showed L4-5 lumbar spinal canal stenosis and a T2-weighted image hyperintense lesion in the L5 lamina. Imaging four years earlier showed no lesions in the L5 lamina. Her symptoms improved after lumbar decompression surgery. The L5 lamina lesion was SBC, leading to a diagnosis of venous infarction. The involvement of neovascularization in the mechanism of degenerative hypertrophy in the ligamentum flavum was suggested. In this case, increased venous perfusion and venous obstruction were involved in the formation of the bone cyst.

Endovascular Treatments for Aneurysms Involving a Major Branch.

Remarkable advances have been made in the endovascular treatment of intracranial cerebral aneurysms. These advances include various adjunctive techniques, increased indications for endovascular treatment, and improved treatment results. Furthermore, the number of cerebral aneurysm treatments using flow diverters (FDs) is expected to increase. However, the reported long-term rate of branch artery occlusion after FD treatment has been reported is 15.8%. Moreover, the complete aneurysm obliteration rate is low if normal branches arise from an aneurysm neck or dome. Flow diverter placement for ophthalmic artery, posterior communicating artery, and anterior choroidal artery aneurysms is often difficult because these normal branches often arise from the aneurysm neck or dome. Therefore, in many cases, coil embolization, which can occlude the aneurysm while preserving branch vessels, should be selected. Although not yet established, various adjunctive techniques and other endovascular treatments that can be performed safely have been reported. Treatment must be planned after understanding the advantages and disadvantages of each treatment method.

A Ruptured Aneurysm of the Transdural Anastomotic Artery Occurring at the Temporal Base in Moyamoya Disease: Case Report and Literature Review.

A 24-year-old woman with hemorrhagic onset moyamoya disease received bilateral indirect bypass surgery 11 years ago. She presented with a life-threatening atraumatic acute right subdural hematoma with temporal lobe intracerebral hemorrhage due to a transdural anastomosis (TDA) aneurysm rupture. We reviewed six cases of rare TDA aneurysms, all of which occurred around the temporal base. TDA aneurysms may occur near the main trunk of the middle meningeal artery (MMA) where hemodynamic stress is high. Therefore, we must pay attention to skull base aneurysms that form near the MMA; otherwise, the prognosis would be poor if such an aneurysm ruptured.

Persistent brain exposure to high sodium induces stroke onset by upregulation of cerebral microbleeds and oxidative stress in hypertensive rats.

High salt intake induces hypertension and enhances stroke onset. However, whether an increase in brain sodium exposure itself is harmful and has poor prognosis remains unknown. Therefore, we employed hypertensive rats that underwent intracerebroventricular (ICV) infusion of sodium for 28 days and evaluated stroke onset and related cytotoxic brain injuries. Forty-seven spontaneously hypertensive stroke-prone (SHRSP) and 39 normotensive rats (Wistar Kyoto rats [WKY]) underwent persistent ICV infusion of the following four solutions: artificial cerebrospinal fluid, 0.9%, 2.7%, and 9% saline for 28 days. We evaluated stroke onset and all-cause mortality between SHRSP and WKY at each ICV sodium concentration as the primary endpoints. Our secondary objective was to explore histological brain injuries associated with SHRSP induced by high sodium ICV. The results indicated that ICV infusion of 2.7% and 9% sodium showed a significant increase in stroke onset, decrease in body weight, and increase rate of brain water content in SHRSP compared to WKY. Increased blood pressure was not observed for ICV infusion of high sodium, while serum sodium concentration was significantly increased in SHRSP compared to WKY. Histological evaluations revealed that higher sodium infusion significantly increased the number of activated microglia, superoxide, neuronal cell loss, and microbleeds compared to WKY and SHRSP with 0.9% sodium. We conclude that persistent exposure to high sodium in the brain is one of the risk factors for stroke onset upregulating cerebral microbleeds and oxidative stress in hypertensive rats.

Intraventricular hemorrhage volume and younger age at surgery may be risk factors for postoperative hydrocephalus after hemispherotomy in children.

OBJECTIVE: Hemispherotomy is an effective treatment for intractable hemispheric epilepsy; however, hydrocephalus remains a common complication of the procedure. The causes of hydrocephalus following hemispherotomy have not been fully elucidated; therefore, the purpose of this study was to identify the risk factors associated with the condition. METHODS: The authors investigated the records of all patients aged < 18 years who underwent hemispherotomy at their institution between 2003 and 2020 and were monitored for hydrocephalus for at least 1 year after the procedure. To identify the risk factors for hydrocephalus, the following information about each patient was collected: sex, corrected age at surgery, body weight at surgery, previous intracranial surgery, etiology of epilepsy, results of PET for hypermetabolism, side of surgery, type of operation (vertical or horizontal approach), operation time, blood loss during surgery, use of intraventricular drainage, occurrence of intraventricular hemorrhage (IVH) on the 1st postoperative day, duration of postoperative fever of > 38°C, and maximum C-reactive protein level after the operation. Multivariate logistic regression analyses were performed. RESULTS: This study included 51 children who underwent hemispherotomies for drug-resistant epilepsy at our hospital. Seven patients (13.7%) experienced hydrocephalus and were treated with ventricular or subdural peritoneal shunts or fenestration. Multivariate logistic analysis using the Bayesian information criterion revealed that 3 factors were associated with the occurrence of hydrocephalus: age at surgery, postoperative IVH volume, and duration of postoperative fever of > 38°C. CONCLUSIONS: This study showed that younger age at surgery, postoperative IVH volume, and duration of postoperative fever of > 38°C might be risk factors for hydrocephalus after hemispherotomy. The risk of hydrocephalus should be considered in cases of early surgical indication in children. Intraoperative hemostasis and postoperative use of anti-inflammatory measures may reduce the risk of hydrocephalus.

Intractable hiccup caused by syrinx in Chiari type I malformation. Two cases report.

Background: Intractable hiccups (IH) due to syringomyelia or syringomyelia/syringobulbia associated with Chiari type I malformations (CMI) are extremely rare. Here, we present two patients who presented with IH; one had a CMI with syringomyelia/syringobulbia, and the other, with CMI and syringomyelia. Case Description: The first patient was an 18-year-old female who presented with IH attributed to a holocord syrinx and syringobulbia involving the right dorsolateral medulla. The second patient was a 22-year-old female with a C3-5 syringomyelia. Both patients successfully underwent foramen magnum decompressions that improved their symptoms, while subsequent magnetic resonance studies confirmed shrinkage of their syringobulbia/syringomyelia cavities. Conclusion: IH was due to cervical syringomyelia/syringobulbia in one patient and cervical syringomyelia in the other; both were successfully managed with foramen magnum decompressions.

Japanese nationwide questionnaire survey on delayed cerebral infarction due to vasospasm after subarachnoid hemorrhage.

Background and purpose: Various prophylactic drugs for cerebral vasospasm and delayed cerebral infarction (DCI) after subarachnoid hemorrhage (SAH) have been used in Japan. To investigate the treatment trends for cerebral vasospasm and frequency of DCI after SAH throughout Japan in 2021. Methods: In 2021 we conducted an anonymous questionnaire survey on management for preventing cerebral vasospasm after aneurysmal SAH, and the frequency of DCI. The questionnaire was emailed to 955 certified neurosurgeons at 553 hospitals in Japan. Of them, 162 hospitals (29% response rate) responded to the questionnaire. Of these, 158 were included in this study, while four hospitals that responded insufficiently were excluded. The efficacy of treatments for reducing DCI were examined through a logistic regression analysis. Results: Among 3,093 patients treated with aneurysmal SAH, 281 patients (9.1%) were diagnosed with DCI related to cerebral vasospasm. Coil embolization had significantly lower DCI frequency (6.9%), compared to microsurgical clipping (11.8%, odds ratio, 0.90; 95% confidential intervals, 0.84-0.96; P, 0.007). In addition, cilostazol administration was associated with significantly lower DCI frequency (0.48; 0.27-0.82; 0.026). The efficacy of cilostazol in reducing DCI remained unchanged after adjustment for covariates. The most effective combination of multiple prophylactic drugs in reducing DCI related to cerebral vasospasm was cilostazol, fasudil, and statin (0.38; 0.22-0.67; 0.005). Conclusions: This study elucidated the trends in prophylactic drugs to prevent cerebral vasospasm and frequency of DCI after aneurysmal SAH in Japan. Coil embolization and cilostazol administration showed effectiveness in reducing DCI related to cerebral vasospasm in 2021.

A case of a pilocytic astrocytoma with histological features of anaplasia and unprecedent genetic alterations.

We report a case of pediatric glioma with uncommon imaging, morphological, and genetic features. A one-year-old boy incidentally presented with a tumor in the fourth ventricle. The tumor was completely resected surgically and investigated pathologically. The mostly circumscribed tumor had piloid features but primitive and anaplastic histology, such as increasing cellularity and mitosis. The Ki-67 staining index was 25% at the hotspot. KIAA1549::BRAF fusion and KIAA1549 partial deletions were detected by direct PCR, supported by Sanger sequencing. To the best of our knowledge, this is the first report of a glioma with both deletion of KIAA1549 p.P1771_P1899 and fusion of KIAA1549::BRAF. The tumor could not be classified using DNA methylome analysis. The present tumor fell into the category of pilocytic astrocytoma with histological features of anaplasia (aPA). Further studies are needed to establish pediatric aPA.

Early recanalization and vasospasm after endovascular treatment in a case of ruptured vertebral artery dissecting aneurysm associated with COVID-19.

Background: The coronavirus disease 2019 (COVID-19) pandemic has caused significant structural changes in acute care hospitals. COVID-19-associated stroke has gained attention, with abnormal coagulation and vascular endothelial damage being recognized. While ischemic cases are commonly reported, hemorrhagic cases have also been reported. This report presents a case of ruptured vertebral artery dissection aneurysm associated with COVID-19, resulting in subarachnoid hemorrhage (SAH). The treatment course, challenges in managing cerebral vasospasm, and early recanalization achieved through endovascular therapy are described. Case Description: A 67-year-old male patient was brought to our hospital for emergency treatment of impaired consciousness that occurred while recovering from COVID-19. He underwent endovascular internal trapping using coils, and although the rupture did not recur, he required long-term tracheal management, which resulted in a cerebral infarction caused by cerebral vasospasm. In addition, early recanalization was seen, which required retreatment. Conclusion: This case highlights the challenges in managing COVID-19-associated SAH and emphasizes the need for infection control measures and proper postoperative care. Establishing protocols for detecting and managing cerebral vasospasm is essential.

Intratumoral thrombosis as a histological biomarker for predicting epidermal growth factor receptor alteration and poor prognosis in patients with glioblastomas.

PURPOSE: Intratumoral thrombosis is a specific finding in glioblastomas and considered the origin of palisading necrosis. Its distribution and contribution to the glioblastoma pathophysiology and systemic thrombosis are obscure, although deep vein thrombosis is a common complication in glioblastoma cases. METHODS: Clinicopathological and genetic analyses were performed on 97 glioblastoma tissue specimens to elucidate the role of thrombotic events and associated molecular abnormalities. RESULTS: Morphologically, intratumoral thrombosis was observed more frequently in vessels composed of single-layered CD34-positive endothelium and/or αSMA-positive pericytes in the tumor periphery, compared to microvascular proliferation with multi-channeled and pericyte-proliferating vessels in the tumor center. Intratumoral thrombosis was significantly correlated with the female sex, high preoperative D-dimer levels, and epidermal growth factor receptor (EGFR) amplification. The presence of one or more thrombi in 20 high-power fields was a predictive marker of EGFR amplification, with a sensitivity of 81.5% and specificity of 52.6%. RNA sequencing demonstrated that the group with many thrombi had higher EGFR gene expression levels than the group with few thrombi. The tumor cells invading along the vessels in the tumor periphery were positive for wild-type EGFR but negative for EGFRvIII, whereas the cells around the microvascular proliferation (MVP) in the tumor center were positive for both wild-type EGFR and EGFRvIII. Intratumoral thrombosis is an independent poor prognostic factor. CONCLUSIONS: Aberrant but exquisitely regulated EGFR can induce thrombosis in non-MVP vessels in the tumor invasion area and then promote palisading necrosis, followed by hypoxia, abnormal angiogenesis, and further tumor cell invasion.

Increased expression of leucine-rich α-2 glycoprotein 1 as a predictive biomarker of favorable progression-free survival in meningioma.

Most meningiomas, which are frequent central nervous system tumors, are classified as World Health Organization (WHO) grade 1 because of their slow-growing nature. However, the recurrence rate varies and is difficult to predict using conventional histopathological diagnoses. Leucine-rich α-2 glycoprotein 1 (LRG1) is involved in cell signal transduction, cell adhesion, and DNA repair and is a predictive biomarker in different malignant tumors; however, such a relationship has not been reported in meningiomas. We examined tissue microarrays of histological samples from 117 patients with grade 1 and 2 meningiomas and assessed their clinical and pathological features, including expression of LRG1 protein. LRG1-high meningiomas showed an increased number of vessels with CD3-positive cell infiltration (P = 0.0328) as well as higher CD105-positive vessels (P = 0.0084), as compared to LRG1-low cases. They also demonstrated better progression-free survival (hazard ratio [HR] 0.11, 95% confidence interval [CI] 0.016-0.841) compared to LRG1-low patients (P = 0.033). Moreover, multivariate analysis indicated that high LRG1 expression was an independent prognostic factor (HR, 0.13; 95% CI, 0.018-0.991; P = 0.049). LRG1 immunohistochemistry may be a convenient tool for estimating the prognosis of meningiomas in routine practice. Further studies are required to elucidate the key role of LRG1 in meningioma progression.

Visual-evoked potential predicts the efficacy of the optical canal decompression for traumatic optic nerve neuropathy showing blindness: A case report.

Background: The indication for surgical optic canal decompression (OCD) for traumatic optic neuropathy (TON) remains controversial because there is no reliable predictor of a good outcome. We report the case of a blind patient with TON whose remaining visual-evoked potential (VEP) suggested recovery potential of the injured optic nerve after OCD. Case Description: A 48-year-old man had fallen from a height of 7 m, striking his head. He immediately complained of right-eye blindness. He had no light perception and the direct light reflex disappeared from the right pupil, although there was no fracture or traumatic lesion on computed tomography and magnetic resonance imaging. Because the amplitude of the VEP with the right eye stimulation remained unchanged, we performed the right OCD. During surgical OCD, the amplitude and latency of VEP began to improve. Finally, the visual field improved in almost all directions, and eyesight improved to 0.2. Conclusion: The retained VEP activity in TON may suggest the recovery potential of the injured optic nerve, even in cases of blindness. It is possible that VEP is an indicator of aggressive treatment for TON such as OCD.

Visual Outcomes and Surgical Approach Selection Focusing on Active Optic Canal Decompression and Maximum Safe Resection for Suprasellar Meningiomas.

The goal of treating patients with suprasellar meningioma is improving or preserving visual function while achieving long-term tumor control. We retrospectively examined patient and tumor characteristics and surgical and visual outcomes in 30 patients with a suprasellar meningioma who underwent resection via an endoscopic endonasal (15 patients), sub-frontal (8 patients), or anterior interhemispheric (7 patients) approach. Approach selection was based on the presence of optic canal invasion, vascular encasement, and tumor extension. Optic canal decompression and exploration were performed as key surgical procedures. Simpson grade 1 to 3 resection was achieved in 80% of cases. Among the 26 patients with pre-existing visual dysfunction, vision at discharge improved in 18 patients (69.2%), remained unchanged in six (23.1%), and deteriorated in two (7.7%). Further gradual visual recovery and/or maintenance of useful vision were also observed during follow-up. We propose an algorithm for selecting the appropriate surgical approach to a suprasellar meningioma based on preoperative radiologic tumor characteristics. The algorithm focuses on effective optic canal decompression and maximum safe resection, possibly contributing to favorable visual outcomes.

[Monitoring for Spine and Spinal Cord Surgery].

Injuries of the spine and nerve root may occur during spine or spinal cord surgery, which can induce serious neurological deficits. Intraoperative monitoring plays important roles in monitoring the nerve function in various surgical manipulations, such as surgical positioning, mechanical compression, and tumor removal. This monitoring issues a warning to neuronal injuries at an early stage, and surgeons are able to prevent postoperative complications. The appropriate monitoring systems should be chosen with compatibility to the disease, surgical procedure, and lesion localization. The team should share the significance of monitoring and understand the timing of stimulation to perform a safe surgery. In this paper, we overview various intraoperative monitoring techniques and pitfalls in spine and spinal cord surgeries based on cases from our hospital.

Effects of Microvascular Decompression on Pain Relief and Quality of Life in Late Elderly Patients with Trigeminal Neuralgia.

Pharmacotherapy is frequently selected over surgical interventions for late elderly patients with trigeminal neuralgia (TN). However, medication may affect these patients' activities of daily living (ADL). Hence, we investigated the effect of the surgical treatment of TN on ADL in older patients. This study included 11 late elderly patients >75 years old and 26 nonlate elderly patients who underwent microvascular decompression (MVD) for TN at our hospital from June 2017 to August 2021. We evaluated pre- and postsurgical ADL using the Barthel Index (BI) score, side effects of antineuralgic drugs, the BNI pain intensity score, and perioperative medication. The BI score of late elderly patients significantly improved postoperatively, particularly in transfer (pre: 10.5; post: 13.2), mobility (pre: 10; post: 12.7), and feeding (pre: 5.9 points; post: 10 points). Additionally, antineuralgic drugs caused preoperative disturbances of transfer and mobility. Trends of a longer disease duration and frequent occurrence of side effects were observed in all patients in the elderly group, compared to only 9 out of 26 patients in the younger group (100% vs. 35%, p = 0.0002). In addition, drowsiness was observed more frequently in the late elderly group (73% vs. 23%, p = 0.0084). However, the change in scores indicating improvement after surgery was significantly greater in the late elderly group, although both pre- and postoperative scores were higher in the nonlate elderly group (11.4 ± 1.9 vs. 6.9 ± 0.7, p = 0.027). Surgical treatment can improve older patients' ADL because it relieves pain and facilitates discontinuation of antineuralgic drugs. Consequently, MVD can be positively recommended for older patients with TN if general anesthesia is acceptable.

Preoperative Novel Magnetic Resonance Fusion Imaging for Carotid Endarterectomy Patients with Contrast Contraindications: A Pilot Study.

OBJECTIVE: For carotid endarterectomy (CEA) patients with renal dysfunction and allergies to contrast media, we developed a preoperative novel method of noncontrast 3-dimensional magnetic resonance fusion imaging (NC-3DMRFI) which could describe well blood vessels, plaques, and bony structures even in surgical position. In this study, we examined the usefulness of this method. METHODS: We extracted noncontrast magnetic resonance images of bones, blood vessels, and plaques to create a 3-dimensionalusion image. An image acquired in the normal position and another in the surgical position during CEA were used to create a fusion image. We compared the fusion imaging results with the intraoperative findings of 6 patients with contrast contraindications received CEA. RESULTS: Preoperative NC-3DMRFI could clearly show the positions of the carotid bifurcation, the distal end of plaque, and the bony structure in 5 of the 6 cases. Intraoperative findings and preoperative fusion imaging results were comparable in all cases where fusion images could be created. The fusion imaging in the surgical position during CEA was useful for preoperative examination, and the surgical space could be secured in the case of a high cervical location. CONCLUSIONS: This pilot study showed our novel NC-3DMRFI method is useful for preoperative simulation in CEA, especially in patients with renal dysfunction and allergies to contrast media.

Bold-S Signs on Computed Tomography Angiography Are Sensitive Markers for Diagnosing Subcortical Hemorrhage Due to Dural Arteriovenous Fistulae on Emergent Admission.

An optimal treatment strategy for subcortical hematomas caused by dural arteriovenous fistulae (dAVF) is important because of the high rebleeding rate. However, it is very difficult to diagnose that on admission. Therefore, an early sensitive predictive marker for subcortical hemorrhage caused by dAVF is necessary, especially during the first contact on admission. S-shaped dilated vessels around the hematoma (bold-S sign) on computed tomography angiography (CTA) performed during admission could be one such marker. Herein, we evaluated the characteristics of these vessels. Among 273 patients with intracerebral hemorrhage between April 2012 and March 2020, 67 patients with subcortical hematomas who underwent CTA on admission without arteriovenous malformations were included. The patients in the dAVF group (n = 7) showed fewer disturbances in consciousness, milder neurological deficits, and more frequent seizures than patients without dAVF (without dAVF group, n = 60). All patients in the dAVF group had dilated S-shaped vessels (2.59 ± 0.27 mm) around the hematomas, and only 20% of the patients in the without dAVF group had these vessels (1.69 ± 0.22 mm). The ratio of the ipsilateral S-shaped/contralateral largest vessels was 1.80 ± 0.29 in the dAVF group and 1.07 ± 0.16 in the group without dAVF. We called the dilated S-shaped vessels the "bold-S sign," with a cutoff ratio of 1.5. Bold-S sign findings are novel and help in diagnosing subcortical hematomas caused by dAVF on admission.

Microscopic observation of morphological changes in cerebral arteries and veins in hyperacute phase after experimental subarachnoid hemorrhage: an in-vivo analysis.

This observational study examined morphological changes in superficial cerebral arteries and veins, which were correlated with increased intracranial pressure (ICP)-dependent and -independent hypoperfusion in hyperacute phase after subarachnoid hemorrhage (SAH). The prechiasmatic injection model was used, and 32 male Sprague-Dawley rats were divided into the sham-operated, saline-injected (V group, ICP increase), and arterial blood-injected (SAH group, subarachnoid blood and plus increase) groups. Morphological changes in cortical arteries and veins were observed through the cranial window with a microscope before and up to 10 min after the injection. At 24 h, the stenotic and obstructive cortical arteries and veins were counted. After 6 min, 60% of rats in the V group showed vasodilatation, whereas all rats in the SAH group demonstrated vasodilation and vasoconstriction (arterial instability) within 10 min. Similar acute venous congestive changes were observed within 10 min in the V and SAH groups. At 24 h, stenotic and obstructive arteries and veins were observed in the SAH group. Neurological deteriorations were observed at 1 h in the V and SAH groups, and at 23 h in the SAH group. The sham-operated group showed no evident vascular changes and neurological deterioration. The same phenomena, including arterial changes after 6 min and immediate venous changes in the V and SAH groups, may have resulted from ICP increase, whereas subarachnoid blood-related factors produced arterial instability within 5 min after blood injection. Subarachnoid blood plays a significant role in hyperacute SAH pathophysiology in addition to ICP increase.

Systemic inflammation caused by an intracranial mesenchymal tumor with a EWSR1::CREM fusion presenting associated with IL-6/STAT3 signaling.

Pediatric neoplastic diseases account for about 10% of cases of fever of unknown origin (FUO), and most neoplastic disease cases are leukemia, lymphoma, and neuroblastoma. Brain tumors are rarely reported as the cause of FUO, although craniopharyngioma, metastatic brain tumor, and Castleman's disease have been reported. We report a case of intracranial mesenchymal tumor (IMT) with a FET:CREB fusion gene, which had inflammatory phenotype without neurological signs. A 10-year-old girl was admitted with a 2-month history of intermittent fever and headache, whereas her past history as well as her family history lacked special events. Sepsis work-up showed no pathological organism, and empirical antibiotic therapy was not effective. Bone marrow examination showed a negative result. Cerebrospinal fluid examination showed elevated protein as well as cell counts, and head magnaetic resonance imaging showed a hypervascular mass lesion with contrast enhancement in the left cerebellar hemisphere. The patient underwent tumor excision, which made the intermittent fever disappear. Pathological examinations resembled those of classic angiomatoid fibrous histiocytoma (AFH), but the morphological features were distinct from the AFH myxoid variant; then we performed break-apart fluorescence in situ hybridization and confirmed the tumor harbored the rare EWSR1::CREM fusion gene (Ewing sarcoma breakpoint region 1 gene (EWSR1) and cAMP response element binding (CREB) family gene). Consequently, we diagnosed the condition as IMT with EWSR1::CREM fusion. Elevated serum concentration of interleukin 6 (IL-6) was normalized after tumor resection, which suggested the fever could be caused by tumor-derived IL-6. This is the first case of IMT with EWSR1::CREM fusion that showed paraneoplastic symptoms associated with the IL-6/signal transducer and activator of transcription 3 (STAT3) signaling pathway. Although brain tumors are rarely diagnosed as a responsible disease for FUO, they should be considered as a cause of unknown fever even in the absence of abnormal neurological findings.