**1. Introduction**

Laser interstitial thermal therapy (LITT) has established itself as a new treatment modality in neurosurgery due to its minimally invasiveness nature, safety and efficacy. Nowadays, LITT has become a reality in the world of neuro-oncology [1–4], epilepsy surgery [5–7], and is also emerging as an attractive option in the fields of spine surgery [8–10] and chronic pain syn‐ dromes[10–12]. In neuro-oncology, LITT has emerged as an option for malignant gliomas, refractory brain metastatic disease and radiation necrosis. LITT is best suited, but not limited, for patients with tumors located in deep-seated, difficult-to-access areas that could develop significant postoperative neurological deficits and poor performance status with traditional microsurgical resection. It is a FDA-approved treatment option for intracranial lesions includ‐ ing recurrent glioblastomas [4]. Concerning brain metastatic disease, although stereotactic radiosurgery (SRS) has become the standard of care for most patients, the failure rate associat‐ ed with SRS is up to 23% [13–15]. Additionally, the potential risk of developing radiation necrosis following SRS can vary from 1.4 to 24% [16–18], and this complication can be refractory to standard therapeutic options like steroids and Bevacizumab. LITT has been effective in managing both radiosurgery-resistant brain metastasis [2, 3, 19–22] and radiation necrosis [3, 21–24].

The surgical applications of lasers are represented by three distinct functionalities of this technology: photocoagulation, photovaporization and photosensitization [25]. LITT is referred to the first one, photocoagulation, which implies tissue damage by thermal energy provided by a source of constant and continuous laser delivery to a planned target volume. It was first introduced in 1983 by Bown and colleagues [26], who used a neodymium-doped yttrium aluminum garnet (Nd:YAG) laser and achieved focal tissue coagulation in an experimental brain tumor model without tissue vaporization. Research using experimental animal models demonstrated the brain tissue changes in response to hyperthermia and confirmed that coagulation necrosis could result from the application of thermal energy to brain tissue [27– 30]. However, the inability to monitor and control the laser-induced thermal effects limited the widespread application of this technology. Recent advances in magnetic resonance (MR) thermography [31] allowed real-time image feedback of laser thermal energy delivery, making it possible to predict the thermal damage of a planned target in the brain.

In the present chapter, the authors describe the current applications of LITT in neuro-oncolo‐ gy, including malignant gliomas, brain metastatic disease and radiation necrosis together with the basic principles and technical nuances related to the surgical procedure and the current LITT systems available in clinical practice. We also touched upon other applications of LITT such as cancer-related refractory pain and epilepsy. Future directions are also discussed in this chapter.
