Endoscopic biopsy for the diagnosis of neurosarcoidosis at the fourth ventricle outlet with hydrocephalus

BACKGROUND Fourth ventricle mass lesion in neurosarcoidosis is very rare and difficult to be diagnosed pathologically. We report a rare case of progressive hydrocephalus associated with neurosarcoidosis mass lesion located at the fourth ventricle outlet and suprasellar region. CASE DESCRIPTION A 23-year-old man had a disturbance of consciousness and neck stiffness with fever. Magnetic resonance imaging revealed diffuse leptomeningeal enhancement, and the obstructive mass lesions at the outlet of the fourth ventricle. We performed an endoscopic biopsy of the enhanced lesion at the foramen Magendie, via foramen Monro and the aqueduct of the midbrain. Pathologically, the diagnosis of neurosarcoidosis was confirmed, and we started treatment with prednisolone. His neurological symptoms disappeared after ventriculo-peritoneal shunt and steroid therapy, and he was discharged without deficit 40 days after emergent admission. CONCLUSION Endoscopic procedure is less invasive and more effective for biopsy of neurosarcoidosis with hydrocephalus, even if the lesion is located at the fourth ventricle outlet.