Primary Intracranial Solitary Fibrous Tumor

Primary Intracranial Solitary Fibrous Tumor

Intracranial solitary fibrous tumors (ISFTs) are rare mesenchymal neoplasms originating in the meninges and constitute a heterogeneous group of rare spindle-cell tumors that include benign and malignant neoplasms of which hemangiopericytoma is nowadays considered a cellular phenotypic variant. ISFT usually shows benign or indolent clinical behavior 1).

Primary Intracranial Solitary Fibrous Tumor (SFT) involving the central nervous system (CNS) was first reported in 1996 by Carneiro et al, who described 7 cases of meningeal SFT that could be distinguished from fibrous meningioma on morphologic and immunohistochemical grounds 2).

Since then, more than 60 cases of CNS SFT including the meninges and the spinal cord have been described in the pertinent literature.

For its rarity and resemblance to other more common brain tumors, such as meningioma and hemangiopericytomas, intracranial SFT (ISFT) is often poorly recognized and remains a diagnostic challenge.

Although there are no pathognomonic imaging findings, some imaging features, such as the “black-and-white mixed” pattern on T2-weighted images and marked heterogeneous enhancement, might be helpful in the diagnosis of intracranial solitary fibrous tumor

A 62-year-old man with headache and memory disturbance for 2 years. A, Noncontrast CT shows a heterogenous hyperattenuated multilobulated tumor in left middle cranial fossa. B, Contrast-enhanced CT, intense but inhomogeneous contrast enhancement is noted. C, T1-weighted axial MR image, a large lobulated mass is seen in the left paraclinoid portion to the tentorium. D, T2-weighted axial MR image reveals 2 different signal intensity portions of the mass, hyposignal intensity and hypersignal intensity to gray matter. E and F, Gadolinium-enhanced T1-weighted axial and coronal MR images show marked and heterogenous enhancement. The tumor is partially implanted on the surface of the tentorium (arrows). Memory disturbance might be because of the mass effect on the limbic system. G, Selective injection of the left internal carotid artery (capillary phase); the tumor is supplied at its periphery by pial branches. H, Selective injection of the left external carotid artery; there is tumor blushing with dysplastic dilation of the tumor vessels. There is no demonstrable significant arteriovenous shunt or early venous drainage. 3).

Case reports

Yamaguchi et al. reported a very rare case of intracranial SFT in a 55-year-old woman who presented with gait disturbance and numbness in bilateral upper limbs from three months prior to visiting the hospital. Head MRI revealed a homogeneously enhancing mass lesion located primarily in the fourth ventricle extending into the spinal canal and left foramen of Luschka, with a maximum diameter of 60 mm. Notably, this tumor presented spontaneous partial regression during waiting planned surgery without therapy, including chemotherapy and radiotherapy. This patient underwent a midline suboccipital craniotomy and resection of the tumor. Interestingly, there was no attachment to the dura mater of the posterior cranial fossa and the lesion was only attached to the dorsal part of the medulla oblongata.

Although the location of the SFT in the fourth ventricle is rare, SFT should be considered as one of the differential diagnosis of fourth ventricle tumors. In addition, this case indicates that SFT in the fourth ventricle may regress on occasion spontaneously without a precisely known cause for this spontaneous partial regression 4).

Torazawa et al., encountered a case of small solitary fibrous tumor in the optic canal causing rapid visual deterioration. The radiographic findings of pre-operative imaging studies were compatible with those of meningioma; however, unlike meningioma, bleeding from the tumor was very profuse during the operation. The endoscopic transnasal approach was effective for handling the highly vascularized tumor in this delicate region, and gross total removal was achieved with postoperative gradual improvement in his visual function. Nevertheless, the tumor recurred after six months, and re-resection was performed with using the same surgical corridor, followed by adjuvant radiotherapy.

Endoscopic transnasal surgery is a valuable option for aggressive lesions in the optic canal. Although the efficacy of radiotherapy for SFT remains controversial, it should be considered when the tumor shows progressive features 5).

A 63-year-old female patient who had confused mentality, without other neurological deficit. The brain MRI showed an ovoid mass in the right frontal lobe. The tumor was surgically removed grossly and totally, and the pathologic diagnosis was SFT. At 55 months after the surgery, the tumor recurred at the primary site and at an adjacent area. A second operation was thus done, and the tumor was again surgically removed grossly and totally. The pathologic diagnosis was the same as the previous, but the Ki-67 index was elevated. Ten months later, two small recurring tumors in the right frontal skull base were found in the follow-up MRI. It was decided that radiation therapy be done, and MRI was done again 3 months later. In the follow-up MRI, the size of the recurring mass was found to have decreased, and the patient did not manifest any significant symptom. Follow-up will again be done 18 months after the second surgery 6).



Aljohani HT, Chaussemy D, Proust F, Chibbaro S. Intracranial solitary fibrous tumor/hemangiopericytoma: Report of two cases and literature review. Int J Health Sci (Qassim). 2017 Jul-Sep;11(3):69-70. PubMed PMID: 28936155; PubMed Central PMCID: PMC5604277.

Carneiro SS, Scheithauer BW, Nascimento AG, Hirose T, Davis DH. Solitary fibrous tumor of the meninges: a lesion distinct from fibrous meningioma. A clinicopathologic and immunohistochemical study. Am J Clin Pathol. 1996 Aug;106(2):217-24. PubMed PMID: 8712177.

Weon YC, Kim EY, Kim HJ, Byun HS, Park K, Kim JH. Intracranial solitary fibrous tumors: imaging findings in 6 consecutive patients. AJNR Am J Neuroradiol. 2007 Sep;28(8):1466-9. PubMed PMID: 17846192.

Yamaguchi J, Motomura K, Ohka F, Aoki K, Tanahashi K, Hirano M, Nishikawa T, Shimizu H, Wakabayashi T, Natsume A. Spontaneous tumor regression of intracranial solitary fibrous tumor originating from the medulla oblongata: A case report and literature review. World Neurosurg. 2019 Jul 18. pii: S1878-8750(19)31958-8. doi: 10.1016/j.wneu.2019.07.052. [Epub ahead of print] PubMed PMID: 31326640.

Torazawa S, Shin M, Hasegawa H, Otani R, Ueki K, Saito N. Endoscopic transnasal resection of solitary fibrous tumor in the optic canal. World Neurosurg. 2018 May 16. pii: S1878-8750(18)31003-9. doi: 10.1016/j.wneu.2018.05.050. [Epub ahead of print] PubMed PMID: 29777894.

Kim JH, Yang KH, Yoon PH, Kie JH. Solitary Fibrous Tumor of Central Nervous System: A Case Report. Brain Tumor Res Treat. 2015 Oct;3(2):127-31. doi: 10.14791/btrt.2015.3.2.127. Epub 2015 Oct 30. PubMed PMID: 26605270; PubMed Central PMCID: PMC4656890.



For epilepsy, the AspireSR®, and SenTiva™ VNS therapy systems are the two most recently developed VNS devices 1).

VNS Therapy generator model, AspireSR®, was introduced and approved for CE Marking in February 2014. In enhancement of former models, the AspireSR has incorporated a cardiac-based seizure-detection (CBSD) algorithm that can detect ictal tachycardia and automatically trigger a defined auto-stimulation 2) 3).

The AspireSR® device operates as a closed-loop system, delivering an automatic stimulation in response to an ictal heart rate increase that serves as a predictor for an imminent seizure. VNS with AutoStim achieves maintenance of prior-established seizure control with markedly less energy consumption and can also improve seizure control as compared to the former stimulator model 4).

The vagal nerve stimulator AspireSR 106 is also a responsive device which, in addition to basal stimulation, is activated by tachycardia. Deep brain stimulation of the anterior nucleus of the thalamus is used in Europe for intractable epilepsy and yields similar response rates to RNS using duty cycle stimulation 5).

The purpose of Tzadok et al. was to assess the outcome of the AspireSR® in a patient population managed in a pediatric neurology unit.

The records of patients who underwent transplantation during 2015-2017 and are continuously followed in one pediatric-epilepsy clinic were retrospectively analyzed. Collected information included demographics, use of antiepileptic drugs and seizure type, frequency and duration before and after VNS implantation.

46 patients ages 5-31 years (mean 15.7 ± 5.8), mean age at implantation 14 ± 5.8 years, were included. 29 patients (63%) were new insertions and 17 of the patients (37%) underwent a VNS replacement to the AspireSR® model. The mean follow-up was 13 ± 7.5 months (range 2-29 months). The total cohort responder rate (patients with ≥a 50% reduction in seizure frequency compared to the pre-implantation period) was 60.9%. (62% in the new insertion group; while 59% in the replacement group had an additional benefit over their former VNS model, p = 0.981). Epilepsy etiology, age, age at implantation and type of seizures pre-implantation showed no correlation to response-rate. Five patients (10.9%) experienced complete seizure-freedom following implantation (4/5 in the “new insertion” group). Responses were reported at a median follow up of 5 ± 1.3 months post-implantation. 67.4% experienced shorter seizure duration post-implantation.

The results suggest that the AspireSR® device provides an early and meaningful benefit to drug-resistant epilepsy patients, which is relevant for both patients with new insertions and those with replacements of former VNS devices 6).

Data were collected retrospectively from patients with epilepsy who had VNS AspireSR® implanted over a three-year period between June 2014 and June 2017 by a single surgeon. Cases were divided into two cohorts, those in whom the VNS was a new insertion, and those in whom the VNS battery was changed from a previous model to AspireSR®. Within each group, the seizure burden was compared between the periods before and after the insertion of AspireSR®.

Fifty-one patients with a newly inserted AspireSR® VNS model had a significant reduction in seizure frequency (p < 0.001), with 59% (n = 30) reporting ≥50% reduction. Of the 62 patients who had an existing VNS, 53% (n = 33) reported ≥50% reduction in seizure burden when the original VNS was inserted. After the battery was changed to the AspireSR®, 71% (n = 44) reported a further reduction of ≥50% in their seizure burden. The size of this reduction was at least as large as that resulting from the insertion of their existing VNS in 98% (61/62) of patients.

The results suggest that approximately 70% of patients with existing VNS insertions could have significant additional benefit from cardiac based seizure detection and closed-loop stimulation from the AspireSR® device. For new insertions, the AspireSR® device has efficacy in 59% of patients. The ‘rule of thirds’ used in counseling patients may need to be modified accordingly 7).

Analysis of electro-encephalographic (EEG) signals has revealed that seizures are accompanied by spatial synchronization of EEG electrodes that may persist for several minutes after the seizure. A quantitative feature was obtained from EEG data around ictal events collected during a 3-5day epilepsy monitoring unit (EMU) visit prior to VNS implantation and following one month after VNS implant. This feature was obtained from 15 patients who underwent implantation of the closed-loop AspireSR® VNS Therapy System 8).

16 patients who underwent implantation of closed-loop VNS therapy system, namely AspireSR, we evaluated if automated delivery of VNS at the time of seizure onset reduces the severity of seizures by reducing EEG spatial synchronization as well as the duration and magnitude of heart rate increase. Unsupervised classification was subsequently applied to test the discriminative ability and validity of these features to measure responsiveness to VNS therapy.

Results of application of this methodology to compare 105 pre-VNS treatment and 107 post-VNS treatment seizures revealed that seizures that were acutely stimulated using VNS had a reduced ictal spread as well as reduced impact on cardiovascular function compared to the ones that occurred prior to any treatment. Furthermore, application of an unsupervised fuzzy-c-mean classifier to evaluate the ability of the combined EEG-ECG based features to classify pre and post-treatment seizures achieved a classification accuracy of 85.85%.

These results indicate the importance of timely delivery of VNS to reduce seizure severity and thus help achieve better seizure control for patients with epilepsy 9).

Patients (n=28) from the Seizure Detection and Automatic Magnet Mode Performance Study (E-36), a clinical trial of the AspireSR® VNS Therapy System® (NCT01325623), were monitored with ambulatory electrocardiograms (ECGs) ~2weeks before de novo VNS system implantation and following 2- to 4-week VNS titration during a protocol-specified 3- to 5-day epilepsy monitoring unit stay with concurrent EEG/ECG recordings. The TWA level was assessed interictally by the Modified Moving Average (MMA) method.

At preimplantation baseline, TWA was elevated above the 47-μV abnormality cutpoint in 23 (82%) patients with drug-resistant epilepsy. In 16 (70%) patients, TWA level was reduced during VNS treatment to <47μV, thereby converting positive TWA test results to negative. Peak TWA level in all 28 patients improved (group mean, 43%, from 72±4.3 to 41±2.3μV; p<0.0001). Vagus nerve stimulation was not associated with reduced heart rate (77±1.4 to 75±1.4beats/min; p=0.18). Heart rate variability was unchanged.

These findings suggest significant interictal cardiac electrical instability in this population of patients with drug-resistant epilepsy and suggest that VNS may be a novel approach to reducing risk 10).

El Tahry et al. reported the experience with three patients in assessing the functionality of ictal stimulation, illustrating the detection system in practice. Detection of ictal tachycardia and variable additional detections of physiological tachycardia depended on the individual seizure-detecting algorithm settings 11).

The E-37 protocol (NCT01846741) was a prospective, unblinded, U.S. multisite study of the AspireSR(®) in subjects with drug-resistant partial onset seizures and history of ictal tachycardia. VNS Normal and Magnet Modes stimulation were present at all times except during the EMU stay. Outpatient visits at 3, 6, and 12 months tracked seizure frequency, severity, quality of life, and adverse events.

Twenty implanted subjects (ages 21-69) experienced 89 seizures in the EMU. 28/38 (73.7%) of complex partial and secondarily generalized seizures exhibited ≥20% increase in heart rate change. 31/89 (34.8%) of seizures were treated by Automatic Stimulation on detection; 19/31 (61.3%) seizures ended during the stimulation with a median time from stimulation onset to seizure end of 35 sec. Mean duty cycle at six-months increased from 11% to 16%. At 12 months, quality of life and seizure severity scores improved, and responder rate was 50%. Common adverse events were dysphonia (n = 7), convulsion (n = 6), and oropharyngeal pain (n = 3). : The Model 106 performed as intended in the study population, was well tolerated and associated with clinical improvement from baseline. The study design did not allow determination of which factors were responsible for improvements 12).

The intraoperative handling was comparable and did not lead to a significant increase in operation time. In our 14 operations, we had no significant short-term complications. Due to its larger size, patients with the AspireSR had significantly larger skin incisions. For optimal heart rate detection, the AspireSR had to be placed significantly more medial in the décolleté area than the Demipulse. The preoperative testing is a unique addition to the implantation procedure of the AspireSR, which may provide minor difficulties, and for which we provide several recommendations and tips. The price of the device is higher than for all other models. : The new AspireSR generator offers a unique technical improvement over the previous Demipulse. Whether the highly interesting CBSD feature will provide an additional benefit for the patients, and will rectify the additional costs, respectively, cannot be answered in the short-term. The preoperative handling is straightforward, provided that certain recommendations are taken into consideration. The intraoperative handling is equivalent to former models-except for the placement of the generator, which might cause cosmetic issues and has to be discussed with the patient carefully. Schneider et al. recommended the consideration of the AspireSR in patients with documented ictal tachycardia to provide a substantial number of patients for later seizure outcome analysis 13).



Mertens A, Raedt R, Gadeyne S, Carrette E, Boon P, Vonck K. Recent advances in devices for vagus nerve stimulation. Expert Rev Med Devices. 2018 Aug;15(8):527-539. doi: 10.1080/17434440.2018.1507732. Epub 2018 Aug 17. Review. PubMed PMID: 30071175.

Schneider UC, Bohlmann K, Vajkoczy P, Straub HB. Implantation of a new Vagus Nerve Stimulation (VNS) Therapy® generator, AspireSR®: considerations and recommendations during implantation and replacement surgery–comparison to a traditional system. Acta Neurochir (Wien). 2015 Apr;157(4):721-8. doi: 10.1007/s00701-015-2362-3. Epub 2015 Feb 13. PubMed PMID: 25673257.

Yamamoto T, Inaji M, Maehara T, Kawai K, Doyle WK. [(3)New Therapeutic Modalities using Seizure Detection Devices for Medically Refractory Epilepsy:AspireSR and the RNS System]. No Shinkei Geka. 2018 Mar;46(3):247-262. doi: 10.11477/mf.1436203711. Japanese. PubMed PMID: 29567875.

Kulju T, Haapasalo J, Rainesalo S, Lehtimäki K, Peltola J. Autostimulation in Vagus Nerve Stimulator Treatment: Modulating Neuromodulation. Neuromodulation. 2019 Jul;22(5):630-637. doi: 10.1111/ner.12897. Epub 2018 Dec 14. PubMed PMID: 30549376.

Hartshorn A, Jobst B. Responsive brain stimulation in epilepsy. Ther Adv Chronic Dis. 2018 Jul;9(7):135-142. doi: 10.1177/2040622318774173. Epub 2018 May 7. Review. PubMed PMID: 29963302; PubMed Central PMCID: PMC6009082.

Tzadok M, Harush A, Nissenkorn A, Zauberman Y, Feldman Z, Ben-Zeev B. Clinical outcomes of closed-loop vagal nerve stimulation in patients with refractory epilepsy. Seizure. 2019 Jul 8;71:140-144. doi: 10.1016/j.seizure.2019.07.006. [Epub ahead of print] PubMed PMID: 31326720.

Hamilton P, Soryal I, Dhahri P, Wimalachandra W, Leat A, Hughes D, Toghill N, Hodson J, Sawlani V, Hayton T, Samarasekera S, Bagary M, McCorry D, Chelvarajah R. Clinical outcomes of VNS therapy with AspireSR(®) (including cardiac-based seizure detection) at a large complex epilepsy and surgery centre. Seizure. 2018 May;58:120-126. doi: 10.1016/j.seizure.2018.03.022. Epub 2018 Mar 28. PubMed PMID: 29702409.

Ravan M. Investigating the correlation between short-term effectiveness of VNS Therapy in reducing the severity of seizures and long-term responsiveness. Epilepsy Res. 2017 Jul;133:46-53. doi: 10.1016/j.eplepsyres.2017.04.008. Epub 2017 Apr 11. PubMed PMID: 28414968.

Ravan M, Sabesan S, D’Cruz O. On Quantitative Biomarkers of VNS Therapy Using EEG and ECG Signals. IEEE Trans Biomed Eng. 2017 Feb;64(2):419-428. doi: 10.1109/TBME.2016.2554559. PubMed PMID: 28113195.

Verrier RL, Nearing BD, Olin B, Boon P, Schachter SC. Baseline elevation and reduction in cardiac electrical instability assessed by quantitative T-wave alternans in patients with drug-resistant epilepsy treated with vagus nerve stimulation in the AspireSR E-36 trial. Epilepsy Behav. 2016 Sep;62:85-9. doi: 10.1016/j.yebeh.2016.06.016. Epub 2016 Jul 21. PubMed PMID: 27450311.

El Tahry R, Hirsch M, Van Rijckevorsel K, Santos SF, de Tourtchaninoff M, Rooijakkers H, Coenen V, Schulze-Bonhage A. Early experiences with tachycardia-triggered vagus nerve stimulation using the AspireSR stimulator. Epileptic Disord. 2016 Jun 1;18(2):155-62. doi: 10.1684/epd.2016.0831. PubMed PMID: 27248796.

Fisher RS, Afra P, Macken M, Minecan DN, Bagić A, Benbadis SR, Helmers SL, Sinha SR, Slater J, Treiman D, Begnaud J, Raman P, Najimipour B. Automatic Vagus Nerve Stimulation Triggered by Ictal Tachycardia: Clinical Outcomes and Device Performance–The U.S. E-37 Trial. Neuromodulation. 2016 Feb;19(2):188-95. doi: 10.1111/ner.12376. Epub 2015 Dec 13. PubMed PMID: 26663671; PubMed Central PMCID: PMC5064739.

Schneider UC, Bohlmann K, Vajkoczy P, Straub HB. Implantation of a new Vagus Nerve Stimulation (VNS) Therapy® generator, AspireSR®: considerations and recommendations during implantation and replacement surgery–comparison to a traditional system. Acta Neurochir (Wien). 2015 Apr;157(4):721-8. doi: 10.1007/s00701-015-2362-3. Epub 2015 Feb 13. PubMed PMID: 25673257.

Chiari type 1 deformity classification

Chiari type 1 deformity classification

Valentini et al. suggested to define an association of Chiari type 1 deformity plus untreated sagittal synostosis, a new subtype of complex CM1. For the high percentage of complications and multiple procedures needed to solve the CM1, they advise identifying by 3D-CT scan these children before performing craniovertebral decompression (CVD). They suggest also that if left untreated, sagittal synostosis may lead to the delayed occurrence of a challenging subset of CM1 1).

Chiari malformation Type 1.5 (CM 1.5) was defined as the association of Chiari malformation Type I (CM I) and brainstem herniation.

Although CM 1.5 patients presented with brainstem herniation and more severe tonsillar herniation, other clinical and imaging features and surgical outcomes were similar to CM I patients. Liu et al. think CM 1.5 is just a subtype of CM I, rather than a unique type of Chiari malformations 2).

Taylor et al. identify two subtypes, crowded and spacious, that can be distinguished by MRI appearance without volumetric analysis. Earlier age at surgery and the presence of syringomyelia are more common in the crowded subtype. The presence of the spacious subtype suggests that crowdedness alone cannot explain the pathogenesis of Chiari I malformation in many patients, supporting the need for further investigation 3).

see Pediatric Chiari type 1 deformity.

see Chiari type 1 deformity and syringomyelia.



Valentini LG, Saletti V, Erbetta A, Chiapparini L, Furlanetto M. Chiari 1 malformation and untreated sagittal synostosis: a new subset of complex Chiari? Childs Nerv Syst. 2019 Jul 21. doi: 10.1007/s00381-019-04283-0. [Epub ahead of print] PubMed PMID: 31327038.

Liu W, Wu H, Aikebaier Y, Wulabieke M, Paerhati R, Yang X. No significant difference between Chiari malformation type 1.5 and type I. Clin Neurol Neurosurg. 2017 Mar 30;157:34-39. doi: 10.1016/j.clineuro.2017.03.024. [Epub ahead of print] PubMed PMID: 28384597.

Taylor DG, Mastorakos P, Jane JA Jr, Oldfield EH. Two distinct populations of Chiari I malformation based on presence or absence of posterior fossa crowdedness on magnetic resonance imaging. J Neurosurg. 2017 Jun;126(6):1934-1940. doi: 10.3171/2016.6.JNS152998. Epub 2016 Sep 2. PubMed PMID: 27588590.
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