Spontaneous Regression of Radiologically Diagnosed Epidermoid Cyst Originating from the Cerebellopontine Angle

Spontaneous regression of an epidermoid cyst in a pediatric patient-Case report and review of the literature

Epidermoid cysts are infrequent, benign, slow-growing, space-occupying lesions that account for 0.5-1.8% of primary intracranial tumors. We report the case of a 17-month-old child who presented in 2015 for one episode of pallor associated with hypotonia. Epilepsy was excluded and MRI was recommended. The MRI was performed and there were no focal parenchymal lesions, but it showed an extra-axial ovoid lesion with imaging characteristics consistent with epidermoid cyst. Follow-up MRI at one year was performed and it showed minimal increased in dimensions of the cyst, without changes into the signal of the lesion. Another MRI was performed 7 years after and it showed complete resolution of the cyst. Six months afterwards, another MRI was performed and it confirmed the complete regression of the cyst, without any extra-axial masses reported. The patient did not present any neurological anomalies. No follow-up MRI was recommended afterwards. Spontaneous regression of epidermoid cyst in pediatric population is an extremely rare event, but it should be taken into account when the patient shows no symptoms. This is the third case of spontaneous regression of an epidermoid cyst reported in pediatric patients, and the first one in the temporal region. Careful follow-up and watchful waiting could be an option to surgical treatment in epidermoid cysts.

The imaging dynamic changes in the malignant transformation of an epidermoid cyst: a case report and literature review

Malignant transformation of epidermoid cysts is a rare complication. Most of the previously reported cases have involved postoperative malignant transformations. We present a case of malignant transformation of a nonpostoperative epidermoid tumor into squamous cell carcinoma (SCC) that occurred in a 61-year-old Chinese woman. The patient's initial cranial MRI scan showed an epidermoid cyst with marginal enhancement in the pre-pontine cistern, and the lesion gradually enlarged after 10 months. A craniotomy was performed using to remove part of the tumor via the right retrosigmoid approach, and postoperative pathology confirmed that the transformation of the epidermoid cyst was malignant. Our case study suggests that the possibility of malignant transformation of epidermoid cyst should not be ignored on the basis of enhanced imaging features, regardless of whether they are nodular, annular, or patchy, as is the case for inflammation. Strict follow-up is required for early detection of malignant transformation to prompt correspondingly early clinical treatment.

A Computational Framework for Pre-Interventional Planning of Peripheral Arteriovenous Malformations

PURPOSE

Peripheral arteriovenous malformations (pAVMs) are congenital lesions characterised by abnormal high-flow, low-resistance vascular connections-the so-called nidus-between arteries and veins. The mainstay treatment typically involves the embolisation of the nidus, however the complexity of pAVMs often leads to uncertain outcomes. This study aims at developing a simple, yet effective computational framework to aid the clinical decision making around the treatment of pAVMs using routinely acquired clinical data.

METHODS

A computational model was developed to simulate the pre-, intra-, and post-intervention haemodynamics of a patient-specific pAVM. A porous medium of varying permeability was employed to simulate the sclerosant effect on the nidus haemodynamics. Results were compared against clinical data (digital subtraction angiography, DSA, images) and experimental flow-visualization results in a 3D-printed phantom of the same pAVM.

RESULTS

The computational model allowed the simulation of the pAVM haemodynamics and the sclerotherapy-induced changes at different interventional stages. The predicted inlet flow rates closely matched the DSA-derived data, although the post-intervention one was overestimated, probably due to vascular system adaptations not accounted for numerically. The nidus embolization was successfully captured by varying the nidus permeability and increasing its hydraulic resistance from 0.330 to 3970 mmHg s ml-1. The nidus flow rate decreased from 71% of the inlet flow rate pre-intervention to 1%: the flow completely bypassed the nidus post-intervention confirming the success of the procedure.

CONCLUSION

The study demonstrates that the haemodynamic effects of the embolisation procedure can be simulated from routinely acquired clinical data via a porous medium with varying permeability as evidenced by the good qualitative agreement between numerical predictions and both in vivo and in vitro data. It provides a fundamental building block towards a computational treatment-planning framework for AVM embolisation.