Gamma Knife Radiosurgery for Transmodiolar Schwannoma.

BACKGROUND: Rare and deep located tumors are surgical challenge with high morbidity. Minimal invasive techniques should be encouraged for a better outcome. Intralabyrinthine schwannoma (ILS) is a rare benign tumor that usually presents with hearing loss and tinnitus. Surgery is associated with high rate of facial paralysis and deafness. Radiosurgery is an option for tinnitus treatment, without the risk of facial paralysis. CASE DESCRIPTION: A young male patient presented with severe hearing loss and incapacitating tinnitus. Magnetic resonance revealed the presence of a small ILS. Radiosurgery was performed and obtained tinnitus control without complications and no further tumor growth. CONCLUSIONS: Tumor control and symptoms relief could be safely achieved through a precisely plan using Gamma Knife radiosurgery, decreasing morbidity. This is the first radiosurgical description for a transmodiolar schwannoma.

The role of diffusion tensor imaging tractography for Gamma Knife thalamotomy planning.

OBJECTIVE The role of tractography in Gamma Knife thalamotomy (GK-T) planning is still unclear. Pyramidal tractography might reduce the risk of radiation injury to the pyramidal tract and reduce motor complications. METHODS In this study, the ventralis intermedius nucleus (VIM) targets of 20 patients were bilaterally defined using Iplannet Stereotaxy Software, according to the anterior commissure-posterior commissure (AC-PC) line and considering the localization of the pyramidal tract. The 40 targets and tractography were transferred as objects to the GammaPlan Treatment Planning System (GP-TPS). New targets were defined, according to the AC-PC line in the functional targets section of the GP-TPS. The target offsets required to maintain the internal capsule (IC) constraint of < 15 Gy were evaluated. In addition, the strategies available in GP-TPS to maintain the minimum conventional VIM target dose at > 100 Gy were determined. RESULTS A difference was observed between the positions of both targets and the doses to the IC. The lateral (x) and the vertical (z) coordinates were adjusted 1.9 mm medially and 1.3 mm cranially, respectively. The targets defined considering the position of the pyramidal tract were more medial and superior, based on the constraint of 15 Gy touching the object representing the IC in the GP-TPS. The best strategy to meet the set constraints was 90° Gamma angle (GA) with automatic shaping of dose distribution; this was followed by 110° GA. The worst GA was 70°. Treatment time was substantially increased by the shaping strategy, approximately doubling delivery time. CONCLUSIONS Routine use of DTI pyramidal tractography might be important to fine-tune GK-T planning. DTI tractography, as well as anisotropy showing the VIM, promises to improve Gamma Knife functional procedures. They allow for a more objective definition of dose constraints to the IC and targeting. DTI pyramidal tractography introduced into the treatment planning may reduce the incidence of motor complications and improve efficacy. This needs to be validated in a large clinical series.

Granuloma de colesterol da ponta do rochedo. Relato de caso / Cholesterol granuloma of the petrous apex. Report of a case

Os autores relatam um caso de granuloma de colesterol da ponta do rochedo, em um paciente do sexo feminino, de 74 anos, que se apresentou clinicamente com alteração de nervos cranianos (V, VI, VIII). O diagnóstico foi feito pela ressonância magnética de encéfalo, que identificou lesão com hipersinal em T1 e em T2, sem realce após administração de contraste paramagnético endovenoso. A via subtemporal extradural permitiu acesso direto à ponta do rochedo, com exerése total da lesão. A paciente evoluiu satisfatoriamente no pós-operatório, com melhora da sintomatologia.