Novel MRI changes after gamma knife for hypothalamic hamartoma in a child.

neural tissue arising from the wall of the hypothalamus. Patients with HH can present with gelastic seizures, precocious puberty or both1. Seizures are usually progressive and accompanied by worsening behavioral problems and developmental delay1. Stereotactic radiosurgery (SRS) has been shown to be safe and effective, resulting in improvement in seizures and halting tumor progression. Gamma Knife (GK) radiosurgery in the treatment of hypothalamic hamartoma has reported Engel Class 1 seizure status of up to 60%, with improvement in behavioral status in some cases2. Post-treatment magnetic resonance (MR) imaging as reported in the literature has not demonstrated significant changes within the treated areas of a HH. The authors report the case of a four year-old boy with a symptomatic hypothalamic hamartoma treated with GK radiosurgery. Serial MR imaging after treatment revealed significant and progressive edema and swelling at the treatment site, with increased T2 signal change and gadolinium uptake lasting one year after treatment and eventually resolving spontaneously. Although not accompanied by clinical worsening, these changes have not been previously reported in SRS for HH.