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Cryoablation of low-flow vascular malformations.

The diagnosis and management of vascular malformations is challenging due to lesion rarity, confusing nomenclature, and clinical symptom overlap in many cases (1, 2). Low-flow vascular malformations are the most common type of congenital vascular anomaly. Traditionally, low-flow vascular malformations include venous malformation (VM) and lymphatic malformation (LM) (2). However, the distinct entity of fibroadipose vascular anomaly (FAVA) was recently described by Alomari et al. (3). FAVA is a complex vascular malformation in the spectrum of low-flow malformations that typically presents with focal pain, discomfort, contractures, and phlebectasia. Imaging characteristics include a fibrofatty lesion overlying a VM usually located in the calf or forearm (3).

For the treatment of low-flow malformations, sclerotherapy has evolved as a primary treatment modality (4, 5). This is in particular true for VMs; however, other potential treatment options for FAVA include conservative management and surgical resection (6). Surgical resection has been found to be effective for focal lesions (7). However in the treatment of malformations, surgery may be associated with increased risk of bleeding or worsening of symptoms. Also surgery is associated with incomplete lesion resection and lesion recurrence (8). Alternative techniques such as radiofrequency ablation (9-11) and cryoablation (6, 12-14) have been proposed to treat low-flow malformations with promising results especially when the lesion is refractory to sclerotherapy.

There are a few published studies evaluating cryoablation as second-line therapy for the treatment of low-flow malformations (12, 13, 15). Percutaneous cryoablation has been used as second-line therapy with favorable results for the treatment of VMs (13, 15) and as a promising primary treatment for FAVA (6). However, previous studies in particular for VMs have not evaluated cryoablation as a primary treatment modality. The purpose of this study is to evaluate the safety and effectiveness of cryoablation of VM and FAVA either as a primary modality or as second-line treatment after sclerotherapy.

Methods

This retrospective review of all consecutive VM and FAVA patients that underwent cryoablation was approved by the Institutional Review Board (IRB #201806101) and conducted over a study period between 2014 and 2017. Informed consent was obtained from all patients/legal guardians prior to the procedure. Eleven patients (6 male, 5 female) with 14 lesions with a median age of 19 years (range 10-50 years) were included in this study. The median lesion volume was 10.8 cm3 (range, 1.8-55.6 cm3). Prior to the procedure, the lesion volumes were measured on magnetic resonance imaging (MRI) using the formula length x breadth x width x 0.5233. Patients were included if they had clinical history, physical exam findings, and MRI findings consistent with VM or FAVA. No patients were excluded from this study. Clinical records, pre-cryoablation procedures, cryoablation procedural details, preprocedural symptoms, clinical outcomes, and complications were evaluated.

Imaging findings

MRI features of VM typically include intermediate to decreased signal intensity on T1-weighted images and increased signal intensity on T2-weighted images. Heterogeneous signal may be observed in cases of associated thrombosis or hemorrhage. The presence of phleboliths are characteristic of VMs (16). On MRI, FAVA demonstrates high signal intensity due to the fibrofatty components on T1- and T2-weighted images. Fibro-fatty components may be present in the intrafascial, intramuscular, or subcutaneous layers. Both VM and FAVA enhance with contrast due to the venous components of the lesion (6).

Patient evaluation

Patients were evaluated in a multidisciplinary clinic prior to cryoablation. Cryoablation was offered as primary treatment if the patient experienced severe focal pain and had a localized low-flow malformation. Otherwise, patients were treated initially with sclerotherapy as primary treatment and once sclerotherapy did not provide symptomatic relief any longer, cryoablation was offered. If sclerotherapy was performed first, there was a minimum of 8 weeks before cryoablation was performed. Indications for cryoablation included pain and swelling. Symptoms, pre-cryoablation treatments, imaging, procedural reports, clinical outcomes and complications were investigated by reviewing the electronic medical record. Complications were classified according to SIR criteria (17).

Cryoablation technique

Prior to the procedure, patients were asked to point the area where they experienced symptoms. This area was evaluated with ultrasonography (US), and the skin was marked to denote the target area. All cases were performed on an outpatient basis under general anesthesia. If the lesion was determined to be in close proximity to a major motor nerve or at risk due to the intended ablation zone, continuous cutaneous neural monitoring or electromyography (EMG) was used intra-procedurally to avoid nerve injury. Surface electrode locations were chosen based on discussion by the interventional radiologist and the monitoring neurologist. Cryoablation was halted if there was a significant decrease in the amplitude of the compound motor action potential as determined by the neurologist.

The cryoablation probes were placed under the direction of US and/or computed tomography (CT) guidance. The goal of the cryoablation procedure was to create an ice ball large enough to cover the area underlying the malformation that was pre-procedurally marked on the skin. Therefore, the aim was to treat the symptomatic region and not necessarily the entire malformation. If there was less than 1 cm of subcutaneous tissue overlying the lesion, hydrodissection and/or warm compresses were used to avoid skin injury. Hydrodissection was performed under US-guidance by instilling saline through a 21-gauge needle to provide separation between the skin surface and the malformation (18). The Endocare PerCryo System (Endocare PerCryo System; Healthtronics) was used with Endocare Perc-17 or Perc-24 cryoprobes selected based on the reference chart provided by the vendor. Two 10-minute freeze cycles were used; however freeze times were adjusted (between 3-10 minutes) based on real-time monitoring of the ice ball growth to cover the lesion and avoid freezing of critical structures including the skin. Final active thaw was performed with helium before probe removal (13). Treatment effects including ice ball coverage were monitored under real-time US and CT. A CT was obtained every 5 minutes in cases where critical structures were located close to the lesion (19). Technical success was achieved if the cryoablation ice ball covered the region of the malformation that corresponded to the patient's symptoms. Patients were discharged at approximately 2-4 hours postprocedure with antiinflammatory and pain medication.

Postprocedure

Following cryoablation, patients were referred for physical therapy evaluation to improve strength, flexibility, and range of motion. Patients were followed up in clinic 1 month and 6 months after the procedure. After the 6-month clinic visit, patients were given the option to return to clinic at a year interval or as needed. Clinical success was defined at 1 month and 6 months after the procedure. At the time of the clinic visit the patient was asked to describe their residual symptoms and compare them to their presenting symptoms. Complete response was described if all preprocedural symptoms resolved. Partial response was considered if there were some residual symptoms that no longer required medications or interfered with activities. Clinical failure was considered if the cryoablation procedure did not improve the symptoms enough to avoid using medications or required additional procedures.

Results

Eleven patients with fourteen lesions underwent percutaneous cryoablation with or without prior sclerotherapy. Nine of the lesions were VMs and the remaining 5 were FAVAs. MRI was used to make all diagnoses of VM or FAVA in conjunction with clinical symptoms. A diagnosis of VM was made if there was intermediate-to-decreased signal intensity on T1-weighted images and increased signal on T2-weighted images. A diagnosis of FAVA was made if there was high signal on both T1- and T2-weighted images which are typically due to the fibrofatty components. Both lesions enhance with contrast due to the underlying venous component.

The median lesion diameter and volume was 4.4 cm (range, 2.0-10.9 cm) and 10.8 cm3 (range, 1.8-55.6 cm3), respectively. All malformations were intramuscular in location and involved the subcutaneous tissues. Four lesions were in the thigh, 3 in the calf, 2 in the foot, 3 in the arm, 1 in the torso, and 1 in the lumbar region.

All 11 patients with VM and FAVA presented with focal pain referable to the lesion. Out of 9 VM cases, 7 had prior sclerotherapy and 2 had primary cryoablation. All 7 VM patients that received sclerotherapy had recalcitrant pain despite treatment. Thus cryoablation was offered (Fig. 1). Of the 5 FAVA cases, 1 had prior sclerotherapy and the remaining four cases underwent primary cryoablation (Fig. 2). None of the lesions had prior intervention including intralesional steroid therapy or surgical resection.

The technical success rate was 100%. The median follow-up time postprocedure was 206 days (120-886 days). At 1-month follow-up, 13 of 14 lesions had a complete response and 1 had a partial response. At 6-month follow-up, 12 of 13 had a complete response and 1 had a partial response. One patient did not have a 6-month follow-up visit. Of the 9 patients in the VM cohort, 7 patients had a complete response. Both patients that were categorized as partial response had improved but continued to have residual pain on follow-up; however, they did not require additional treatments. Of the 5 patients in the FAVA cohort, 4 had complete response. One patient had a partial response with residual contracture; however, she did not require any medications or further treatment (Table). There was a total of 6 patients that were treated with cryoablation as a primary modality (2 VM, 4 FAVA). In this cohort, 5 of 6 patients had complete resolution of symptoms.

There were 3 minor complications following cryoablation as defined by SIR Criteria (14). Two skin blisters were observed, both of which resolved in less than 2 weeks with conservative management and did not leave any skin marks or scars. There was 1 case of transient numbness, which subsided with conservative management. Conservative management for this patient included stretching/strengthening exercises along with antiinflammatory medications to reduce soft tissue swelling. No motor or sensory nerve injuries were observed.

Discussion

In the present series of 11 patients with 14 vascular malformations, US and CT-guided cryoablation was feasible, safe, and provided complete symptomatic relief for most patients. Notably, cryoablation was used as a primary treatment modality in 6 patients with favorable result and a positive treatment result was observed in all lesions treated.

The treatment of vascular malformations has changed in the last few decades. Initially, surgery was the main modality; however, there have been significant morbidity and recurrence rates (20, 21). Percutaneous and endovascular treatments including sclerotherapy and embolization have now become the mainstay for the treatment of vascular malformations with improved outcomes, decreased complication rates, and less morbidity (2, 6, 22).

While the outcomes have improved over time, there is a subset of patients that has had multiple sclerotherapy sessions yet remain symptomatic and thus cryoablation appears to serve a role in treatment (15). More recently, FAVA has been recognized as a separate entity, which is within the spectrum of low-flow malformations (3). FAVAs do not appear to respond as well to sclerotherapy because solely treating the venous component of the malformation does seem to be as important as treating the fibroadipose element that causes contractures and pain. Previous studies have used cryoablation for the indication of neuropathic pain (23, 24). Cryoablation for FAVA appears efficacious in its ability to treat focal pain that results from the malformation (6).

In previous studies, second-line treatment was defined as a treatment regimen that is pursued when first-line therapy is not efficacious. Prior studies have evaluated the use of cryoablation for either the second-line treatment of various vascular anomalies (12), second-line therapy for VMs (13, 15), and FAVAs (6). A previous study by Thompson et al. (12) found cryoablation and laser ablation to be effective second-line treatments of vascular anomalies in eight patients. Cornelis et al. (15) found cryoablation to be a safe and effective second-line treatment option for VMs in a series of 24 patients.

The findings of this current study agree with previously published studies regarding the feasibility of cryoablation in the treatment of vascular malformations. However, in the current study, cryoablation was utilized with success as primary treatment modality in 6 patients: 2 with VMs and 4 with FAVAs. In the 6 patients where cryoablation was used as the primary modality, US and MRI showed a well-circumscribed focal lesion. Due to these imaging findings and the desire to optimize treatment cryoablation was utilized specifically for those lesions.

In this study there were no major complications and 3 minor complications. The complication rate in the current study compares to previously published studies which also report low complication rates (6, 15). The ice ball was continuously monitored with US along with preventative measures including hydrodissection and/or warm compresses on the skin. In the future these complications may be avoided by more aggressive hydrodissection or decreasing the size of the ice ball.

There are several limitations in this study. This is a retrospective review of a small cohort of patients with one patient having short-term follow-up of less than 6 months. In this study, the treatment for low-flow malformations was not standardized therefore some patients had sclerotherapy prior to cryoablation which may confound the results. The choice of sclerotherapy and/or cryoablation was performed on a case-by-case basis via a multidisciplinary vascular anomalies conference. Other limitations include the lack of standardized quantification of symptoms and a limited follow-up time period. A small number of lesions was evaluated which owes to the fact that VMs and FAVAs are rare. VMs may be diffuse, infiltrative, and involve the skin. In this study, only cases of localized VMs were treated. All FAVA and VMs selected to be treated were localized lesions in the muscle +/- the subcutaneous region.

In conclusion, percutaneous cryoablation appears to be safe and effective in the treatment of symptomatic low-flow vascular malformations either as a primary modality or secondary therapy in addition to sclerotherapy. Due to its underlying nature, vascular malformations are difficult to manage. Cryoablation provides an additional treatment option for patients due to its implications in improvement in quality of life and functionality.

Conflict of interest disclosure

The authors declared no conflicts of interest.

References

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(14.) Cornelis FH, Labreze C, Pinsolle V, et al. Percutaneous image-guided cryoablation as second-line therapy of soft-tissue venous vascular malformations of extremities: a prospective study of safety and 6-month efficacy. Cardiovasc Intervent Radiol 2017; 40:1358-1366. [CrossRef]

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Raja S. Ramaswamy [iD]

Tatulya Tiwari [iD]

Michael D. Darcy [iD]

Seung K. Kim [iD]

Olaguoke Akinwande [iD]

Niloy Dasgupta [iD]

Carlos J. Guevara [iD]

From the Department of Radiology (R.S.R. [??] ramaswamyr@wustl.edu, M.D.D., S.K.K., O.A., N.D.), Mallinckrodt Institute of Radiology, Washington University School of Medicine, St. Louis, Missouri, USA; Department of Radiology, Division of Endovascular Surgery and Interventional Radiology (T.T.), Lexington Veterans Affairs (VA) Medical Center, Lexington, Kentucky, USA; Department of Diagnostic and Interventional Radiology (C.J.G.), University of Texas Health Center, Houston, Texas, USA.

Received 27 June 2018; revision requested 16 July 2018; last revision received 29 October 2018; accepted 3 November 2018.

Published online 12 April 2019.

DOI 10.5152/dir.2019.18278

Main points

* For the treatment of low-flow malformations, sclerotherapy has evolved as a primary treatment modality. Other treatment options include conservative management and surgical resection.

* Prior literature indicates that percutaneous cryoablation has been used as second-line therapy with favorable results for the treatment of venous malformations (VM) and as a promising primary treatment for fibroadipose vascular anomaly (FAVA).

* The findings of this study indicate that percutaneous cryoablation appears to be safe and effective in the treatment of symptomatic low-flow vascular malformations either as a primary modality or secondary therapy in addition to sclerotherapy.
Table. Characteristics of study patients treated by cryoablation

Patient no  Age    Preprocedure symptoms  Malformation  Prior
            (yrs)                                       sclerotherapy

 1          29     Pain, swelling         VM            No
 2          10     Pain, contracture      FAVA          Yes
            11     Pain, contracture      FAVA          No
            12     Pain, contracture      FAVA          No
 3          17     Pain, swelling         FAVA          No
 4          12     Pain, contracture      FAVA          No
 5          41     Pain, swelling         VM            Yes
 6          14     Pain, tightness        VM            Yes
 7          49     Pain, tightness        VM            Yes
            50     Pain, swelling         VM            No
 8          41     Pain, tenderness       VM            Yes
 9          35     Pain, swelling         VM            Yes
10          21     Pain, swelling         VM            Yes
11          12     Pain, swelling         VM            Yes

Patient no  Lesion         Maximal         Volume        Number of
            location       dimension (cm)  ([cm.sup.3])  cryoprobes

 1          Thigh           9.0            52.75         3
 2          Foot            2.3             4.12         1
            Calf            5.9             9.15         2
            Foot            3.7             9.76         1
 3          Calf           10.9            55.59         1
 4          Calf            6.0            47.10         3
 5          Arm             3.3            10.64         1
 6          Thigh           2.0             6.91         1
 7          Back - Lumbar   3.6             7.23         1
            Torso           8.0            37.68         4
 8          Thigh           8.7            49.72         2
 9          Arm             5.0            45.79         2
10          Arm             3.4            10.96         1
11          Thigh           2.1             1.81         1

Patient no  Postprocedure         Complications
            symptoms

 1          Asymptomatic          None
 2          Asymptomatic          None
            Asymptomatic          None
            Residual contracture  Skin blister
 3          Asymptomatic          None
 4          Asymptomatic          Skin blister
 5          Residual              None
 6          Asymptomatic          None
 7          Asymptomatic          None
            Asymptomatic          None
 8          Residual pain         None
 9          Asymptomatic          None
10          Asymptomatic          Transient numbness
11          Asymptomatic          None

VM, venous malformation; FAVA, fibrovascular adipose vascular anomaly.
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Title Annotation:ORIGINAL ARTICLE
Author:Ramaswamy, Raja S.; Tiwari, Tatulya; Darcy, Michael D.; Kim, Seung K.; Akinwande, Olaguoke; Dasgupta
Publication:Diagnostic and Interventional Radiology
Date:May 1, 2019
Words:3473
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