Neuroendoscopic options in the treatment of mesencephalic expanding cysts: Report of four cases and review of the literature

Objective Mesencephalic expanding cysts, also called lacunae, are rare intraparenchymal, multilobulated cavities of variable diameter mostly localized in the thalamo-mesencephalic region. In symptomatic cases, usually presenting with hydrocephalus or midbrain syndrome, surgical treatment is required and, considering their position, a minimally invasive approach should be preferred. Methods Four cases of expanding mesencephalic cysts endoscopically treated in three different Italian centers are described. Other possible causes of intracerebral cyst were excluded in all cases by complete neuroimaging and laboratory screening. All patients presented with signs and symptoms of midbrain compression and a slight to moderate ventricular dilation was present in three cases. Results All patients underwent endoscopic cyst fenestration into the ventricle, associated with endoscopic third-ventriculostomy (ETV) in two cases and with cyst wall biopsy in one case. One patient suffered from transient worsening of her hemiparesis due to intraoperative bleeding. All patients showed clinical improvement and a reduction in cyst size on follow-up magnetic resonance images (MRI). Conclusion Neuroendoscopy appears to be an effective, probably definitive surgical option in the treatment of symptomatic mesencephalic expanding cysts. Associating ETV with cyst fenestration seems to offer more complete treatment. Deep intracystic navigation and cyst wall biopsy should be avoided