Case A 17 year old man presented with acute headache and bilateral abducens nerve palsies. CT scan revealed obstructive hydrocephalus caused by a third ventricular lesion. He was managed with a ventriculoperitoneal shunt and biopsies of the lesion were taken. Histologically, the lesion contained non-caseating epitheliod cell granulomas, suggestive of sarcoidosis. He was treated with high dose prednisolone and remained clinically well but follow up brain MRI revealed a significant increase in volume of the third ventricular lesion. Following unsuccessful investigations to find any evidence of systemic sarcoid, the patient underwent a second brain biopsy which confirmed the diagnosis of germinoma. Both the biopsies were done through a craniotomy and transcallosal dissection in order to have a good view of the abnormalities from within the ventricles and recover decent tissue samples that at least macroscopically were representative and large enough to try to prevent sampling error. The patient was then successfully treated with targeted radiotherapy, resulting in complete regression of the tumour.
Discussion Non-caseating granulomas are the characteristic histological finding in sarcoidosis but are not specific for the disease. The differential diagnosis for non-caseating granulomas is wide and includes Germinoma. Neurologists should be aware of the association between non-caseating granulomas and germinoma, and should always be considered when granulomas are seen in the pineal gland, posterior third ventricle, suprasellar region and midline lesions because patients with germinoma do well with radiotherapy. Early recognition and appropriate management is associated with survival rates over 90%.