Late complications of radiosurgery for cerebral arteriovenous malformations: report of 5 cases of chronic encapsulated intracerebral hematomas and review of the literature

Pericytes and vascular smooth muscle cells in central nervous system arteriovenous malformations

Previously considered passive support cells, mural cells-pericytes and vascular smooth muscle cells-have started to garner more attention in disease research, as more subclassifications, based on morphology, gene expression, and function, have been discovered. Central nervous system (CNS) arteriovenous malformations (AVMs) represent a neurovascular disorder in which mural cells have been shown to be affected, both in animal models and in human patients. To study consequences to mural cells in the context of AVMs, various animal models have been developed to mimic and predict human AVM pathologies. A key takeaway from recently published work is that AVMs and mural cells are heterogeneous in their molecular, cellular, and functional characteristics. In this review, we summarize the observed perturbations to mural cells in human CNS AVM samples and CNS AVM animal models, and we discuss various potential mechanisms relating mural cell pathologies to AVMs.

Frameless versus frame-based stereotactic radiosurgery for intracranial arteriovenous malformations: A propensity-matched analysis

Objective

The frameless linear accelerator (LINAC) based stereotactic radiosurgery (SRS) has been evolving with a reduction in patient discomfort. However, there was limited evidence comparing frame-based and frameless SRS for intracranial arteriovenous malformations (AVM). We aimed to compare the treatment outcomes between frame-based and frameless LINAC SRS.

Materials and Methods

This retrospective cohort compared the outcomes of frame-based LINAC SRS (1998-2009) with frameless LINAC SRS (2010-2020). The primary outcome was the obliteration rate. The other outcomes included the neurological, radiological, and functional outcomes after SRS. A matched cohort was identified by propensity scores for further comparisons.

Results

A total of 65 patients were included with a mean follow-up time of 13.2 years (158.5 months). There were 40 patients in the frame-based group and 25 patients in the frameless group. The overall obliteration rate was comparable (Frame-based 82.5% vs Frameless 80.0%, p = 0.310) and not significantly different over time (log-rank p = 0.536). The crude post-SRS hemorrhage rate was 1.5% and the incidence was 0.3 per 100 person-years. There were 67.7% of patients with AVM obliteration without new persistent neurological deficits at the last visit and 56.9% of patients with AVM obliteration without any deficits (transient or persistent) during the entire follow-up period. Four patients (8.0%) developed late onset persistent adverse radiation effects (more than 96 months after SRS) among 50 patients with more than 8-year surveillance. In the propensity-matched cohort of 42 patients, there was no significant difference in AVM obliteration (Frame-based vs Frameless, log-rank p = 0.984).

Conclusion

Frameless and frame-based LINAC SRS have comparable efficacy in intracranial AVM obliteration. A longer follow-up duration may further characterize the rate of late adverse radiation effects in frameless SRS.

Long-term follow-up of an overexposure radiation incident in a cohort treated with linear accelerator-based stereotactic radiosurgery for intracranial arteriovenous malformations

OBJECTIVE

Dosimetric radiosurgery incidents are rare and probably insufficiently reported in scientific publications. After a long follow-up (FU), the authors studied the outcomes of patients treated with overexposure radiation for arteriovenous malformation (AVM) administered via stereotactic radiosurgery (SRS) at their department.

METHODS

Between May 2006 and June 2007, 22 patients were treated for AVM with SRS. The mean (range) patient age was 43.5 (11.8-78) years. Previous treatments were embolization (n = 10), SRS (1), and surgery (1). The average (range) volume was 2.1 (0.2-6.4) cm3. The median prescribed minimal dose was 18.0 Gy. An initial error in the estimation of scatter factors led to overexposure to radiation. Due to this incident, the median delivered minimum dose was 25.0 Gy. All patients were prospectively followed with clinical examination and imaging.

RESULTS

The mean (range) clinical FU was 14.5 (12.0-15.2) years. AVM obliteration after SRS was completed in 90.9% of patients at a mean (range) of 39.4 (24.4-70.4) months. No patient had post-SRS AVM bleeding. Three patients (13.6%) had new permanent deficits due to radiation-induced changes (RICs). Obliteration without new deficits was achieved in 18 patients (81.8%). Two patients had new epilepsy that was probably due to RIC but well controlled. The median (range) MRI FU was 13.8 (2.5-14.9) years. During MRI FU, two RIC periods were observed: one classic period during the first 3 years showed T1-weighted annular irregular enhancement (13%), and the other period between 5 and 15 years after SRS showed the occurrence of cystic and hemorrhagic lesions (22.7%). There were no cases of radiation-induced tumor.

CONCLUSIONS

The present long-term report showed that this overexposure incident probably increased the AVM obliteration rate. This overexposure seems to have induced RIC and in particular a higher rate of cystic and hemorrhagic late lesions with nevertheless moderate clinical consequences. Long-term FU for AVM is mandatory due to the risk of late RIC.

Retiform endothelial hyperplasia mimicking cavernous malformation as a late complication of Gamma Knife radiosurgery

OBJECTIVE

Gamma Knife radiosurgery (GKRS) is a powerful tool for the management of arteriovenous malformations; however, newly formed mass lesions resembling cavernous malformations are a rare late complication of GKRS. In this retrospective study, the authors tried to clarify the unique histological features of these mass lesions.

METHODS

The authors retrospectively reviewed the clinical course of 889 patients who had undergone GKRS for arteriovenous malformations at their institute from 1991 to 2021. Among the 848 patients who had been followed up periodically with neuroradiological imaging, 37 developed a mass lesion mimicking a cavernous malformation and underwent surgical removal of the lesion. The median volume of the original nidus was 3.7 cm3 (range 0.07-30.5 cm3), and the median prescription dose was 21 Gy (range 12-25 Gy). The histological characteristics and radiological and clinical features of the 37 patients were investigated.

RESULTS

Histological examination showed an organized hematoma and a structure termed "retiform endothelial hyperplasia" (RFEH) consisting of endothelium forming multiple lumen-like vascular channels mimicking cavernous malformations but lacking the subendothelial connective tissue that forms the typical vascular wall structure found in cavernous angioma and capillary telangiectasia. RFEH was detected a median of 10.8 years (range 3.2-27.4 years) after GKRS. Neuroimaging showed hematoma surrounded by massive brain edema in all 37 patients. Symptoms caused by mass effect of the lesion and perifocal edema worsened relatively rapidly but completely disappeared after surgery. No recurrence or morbidity occurred after the surgery.

CONCLUSIONS

The delayed formation of RFEH that is mimicking a cavernous malformation neuroradiologically but is histologically distinct from a vascular malformation is a potential complication of GKRS. Its progressive clinical course suggests that surgical removal should be considered for symptomatic patients and/or patients with an apparent radiological mass sign.

Chronic Encapsulated Intracerebral Hematoma as an Occasional Finding in Sudden Cardiac Death

Chronic encapsulated intracerebral hematoma (CEIH) is a rare solid mass characterized by the presence of a fibrotic capsule that can present a variety of signs and symptoms due to the mass effect and hydrocephalus. It may be caused by post-traumatic or spontaneous bleeding as related to an adjacent aneurysm, angiomas or neoplasms. Differential diagnosis must be applied in order for it to mimic neoplasm or a vascular malformation. Several cases of CEIH have been reported but only a few of them have an intraventricular localization. A forensic autopsy of a 50-year-old male who died suddenly while driving is discussed. Gross analysis, histology and toxicology were performed and a CEIH of the right lateral ventricle was found in a case of acute coronary death.

Encapsulated Intracerebral Hematoma Presenting as Cerebral Abscess

Chronic encapsulated intracerebral hematoma is a rare pathology which may present after spontaneous intracerebral hemorrhage (ICH) or radiosurgery for arteriovenous malformations. A 66-year-old male presented with recent diagnosis of cerebrovascular accident (CVA) status post-treatment with tissue plasminogen activator and mechanical thrombectomy. His recent diagnoses included infective endocarditis, septic bacteremia, meningitis, and aspiration pneumonia. One month following his CVA, the patient presented with delayed altered mental status. In the setting of increasing lethargy, computed tomography and magnetic resonance imaging of the brain were performed, which suggested a brain abscess, septic emboli, and ventriculitis. The patient was taken to surgery emergently. Intraoperatively, the patient was found to have an encapsulated mass of liquid consistency. Tissue pathology demonstrated ischemic cortical tissue and hemorrhage. Multiple cultures were negative for growth. The patient was ultimately determined to have an encapsulated intracerebral hematoma. Encapsulated intracerebral hematoma should be a part of the differential diagnosis when presented with a brain abscess in the setting of a patient who is at risk of ICH.