Sarcoidosis is a chronic multisystemic disorder of unknown aetiology characterized by accumulation of epithelioid granulomas without caseation necrosis in affected organs. This disease is common among young adults between 20 and 40 years with a female predilection. Its prevalence is estimated between 8 and 10 per 100 000. Pulmonary involvement is the most frequent manifestation but the disease can actually affect any organ [1, 2]. The prevalence of clinical involvement of the nervous system is estimated to be about 5–15% [3, 4]. However, autopsy results suggest that a subclinical involvement may be present in up to 25% of patients . The prognosis of neurosarcoidosis is poor with mortality rates among 10% to 18% . Any part of the nervous system can be affected, but the most commonly involved structures are the cranial nerves, the hypothalamus and the pituitary gland. Sarcoid granulomas can also affect the meninges, the parenchyma of the brain, the brainstem, the subependymal layer of the ventricular system, the choroids plexuses, the peripheral nerves and the blood vessels supplying the nervous structures . Hypothalamo-pituitary (HP) manifestations are rare, occurring in <1% of all intrasellar lesions . Only a few studies have specifically described HP involvement. Diabetes insipidus (17–90%) has been considered the most frequently reported endocrine disorder .
Due to the potential of pachymeningeal, leptomeningeal and parenchymal involvement there is a wide spectrum of imaging characteristics. Neurosarcoidosis can manifest as focal dural masses or diffuse dural thickening, with low signal intensity on T2-weighted sequences and homogeneous enhancement on contrast enhanced T1-weighted sequences. Leptomeningeal involvement is the most typical manifestation of central nervous system disease, accounting for 40% of the cases. It is recognised as diffuse or nodular enhancement of the leptomeninges, spreading along the perivascular spaces and with a predilection for the basilar meninges. Hypothalamus and pituitary involvement pertains to the last category and shows as leptomeningeal thickening and enhancement around the hypothalamus and pituitary infundibulum. Hydrocephalus, cranial nerve involvement and enhancing parenchymal mass lesions are part of the spectrum of imaging of neurosarcoidosis. Generally, the features of the lesions are so atypical that without a known history of the systemic disease the differential diagnosis can be quite broad .