Elsevier

World Neurosurgery

Volume 104, August 2017, Pages 192-196
World Neurosurgery

Technical Note
Lesion Optimization for Laser Ablation: Fluid Evacuation Prior to Laser-Induced Thermal Therapy

https://doi.org/10.1016/j.wneu.2017.04.167Get rights and content

Background

Magnetic resonance–guided laser-induced thermal therapy (MRgLITT) is a minimally invasive surgical procedure for ablating intracranial lesions. The presence of a fluid body can sequester thermal energy generated by the laser catheter, which compromises the performance of MRgLITT, resulting in suboptimal ablation of cystic lesions. We report our use of stereotactic fluid evacuation followed by MRgLITT in 2 patients with cystic brain tumors. This is the first report on lesion optimization by fluid aspiration before MRgLITT.

Methods

Two cystic tumors in 2 patients were treated. In 1 patient, an external ventricular drain was placed stereotactically to allow drainage of cystic fluid 1 day before laser ablation. In the second patient, a stereotactic biopsy needle was used to aspirate the cystic fluid immediately before laser ablation. The remaining solid portions of the both tumors were ablated using the Visualase system. Both patients were followed clinically and radiologically after the procedures.

Results

Stereotactic placement of an external ventricular drain and a biopsy needle both successfully resulted in fluid evacuation. MRgLITT was performed without any complications in both patients after fluid evacuation. Both patients demonstrated clinical and radiologic improvement after the procedure.

Conclusions

Cystic fluid evacuation is a promising strategy for optimizing intracranial cystic lesions for MRgLITT. This novel approach may broaden the utility of MRgLITT in the management of various technically demanding lesions.

Introduction

Magnetic resonance–guided laser-induced thermal therapy (MRgLITT) is a minimally invasive surgical procedure for the ablation of intracranial lesions. However, the presence of a fluid body can sequester thermal energy generated by the laser catheter.1, 2, 3, 4, 5 Two commercially available laser systems are widely used: the Visualase system (Medtronic, Minneapolis, Minnesota, USA) and the NeuroBlate System (Monteris Medical, Inc., Plymouth, Minnesota, USA). Typically, laser energy is delivered in a spherical fashion; however, the Monteris system offers a side-fire option as well.3, 6, 7 The resulting thermal coagulation causes denaturation of proteins and ultimately cell death.

Despite its diverse application for many neurosurgical conditions, MRgLITT is not without limitations.5 Prior studies have noted that the efficacy of MRgLITT is compromised in lesions with associated cystic components.2, 3, 8 The delivery of laser energy depends on many factors, including tissue composition, perfusion, and symmetry.1, 2 Prior studies have demonstrated that the presence of a fluid body can act as a heat sink to sequester thermal energy, compromising the extent of laser ablation.2, 3 This can result in asymmetric heat distribution and affect ablation outcomes. This situation presents a unique technical challenge that limits the application of MRgLITT in managing intracranial neoplasms with cystic components. Hence, if the fluid component can be removed or reduced before laser ablation, this may allow for more symmetric heat distribution and better treatment outcomes. In this study, we demonstrate our results of MRgLITT with preablation fluid evacuation. We describe 2 cases in which fluid evacuation was used for lesion optimization before ablation. A different approach was used in each case. Fluid evacuation before ablation could serve as a novel technical adjuvant to broaden the application and improve the efficacy of MRgLITT in the treatment of cystic lesions.

Section snippets

Case Histories

Patient A was a 64-year-old man with a known left posterior insular anaplastic astrocytoma who had completed radiation and chemotherapy. He was referred to our service because of radiologic progression of the cystic and contrast-enhancing components of the lesion (Figure 1A and B). Because of the size and location of the lesion, the patient was not a good candidate for open surgical resection. His reported deficits on admission were intermittent episodes of expressive aphasia, confusion,

Results

Patient A tolerated the procedure well and was extubated in stable condition. Postoperative MRI with contrast enhancement was performed 24 hours later (Figure 1E and F). At his 1-month postoperative evaluation, the patient continued to have mild expressive aphasia, but he did not experience any further episodes of seizures or confusion. MRI revealed a treatment-related cavity (Figure 1G and H). He was subsequently discharged to follow up as an outpatient.

Patient B tolerated the procedure very

Discussion

With advances in MRI and laser catheters, MRgLITT has become a useful and minimally invasive method for treating intracranial lesions.3, 4, 6, 8 Despite its promising applicability, prior studies have shown that lesions with fluid components are challenging to ablate in a standard and predictable fashion.1, 2, 9, 10 This is presumably due to sequestration of thermal energy by cystic fluid.2, 3, 10 Therefore, subtotal and suboptimal thermal ablation of these target lesions results.3 A method to

Conclusions

To our knowledge, this is the first study to explore the utility of MRgLITT in the treatment of cystic intracranial lesions. The favorable outcomes suggest that fluid aspiration may optimize intracranial cystic lesions for laser ablation. The evacuation of fluid prevents thermal energy sequestration and results in better ablation with MRgLITT. This technical adjuvant would allow the application of MRgLITT to a larger cohort of patients with surgically challenging cystic tumors.

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    Citation Excerpt :

    For the same reason, tumors with a cystic component compromise the efficacy of LITT.27,40,46 Work by Wong et al.46 suggests that fluid evacuation in cystic brain tumors may reinstate the usefulness of thermal ablation in pathologies that present with cystic fluid. Although LITT has demonstrated its ability to target tumors in traditionally difficult-to-reach areas,40,41 its use near highly eloquent structures must be carefully monitored as unintended thermal damage still may occur.5

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