Imaging Manifestations of Neurosarcoidosis

Core disease facts

• Systemic granulomatous disease → non-caseating granulomas
• CNS involvement in 5–25% (often presenting manifestation)
• Diagnosis often presumptive; biopsy not always feasible
• Imaging findings are protean → always in DDx with MS, TB, lymphoma

Brain parenchyma

• T2 hyperintense periventricular lesions → MS-mimic
• Enhancing mass-like lesions → can mimic tumor/lymphoma
• Often T2 dark mass lesions (helpful clue vs glioma/metastasis)
• No central necrosis usually
• Frequently coexists with leptomeningeal disease

Leptomeningeal disease (most classic)

• 40% cases
• Thickened enhancing leptomeninges (basal cistern preference)
• Nodular or diffuse; often extends along perivascular spaces
• Indistinguishable from TB or lymphoma leptomeningitis on imaging

Hypothalamus / pituitary / infundibulum

• Thickened enhancing stalk → DI or amenorrhea clinically
• DDx: LCH / hypophysitis / metastasis

Cranial nerves & orbit

• CN involvement = common
• VII most symptomatic; II most radiographically abnormal
• Optic nerve sheath involvement can mimic optic meningioma
• Orbital soft tissue involvement → pseudotumor-like

Hydrocephalus

• Communicating from CSF resorption failure
• Obstructive from granulomas/adhesions → trapped ventricle possible

Dura & skull

• Dural thickening / dural masses (T2 dark enhancement) → mimics meningioma/lymphoma
• Skull lesions = punched-out lytic (no sclerosis) with soft-tissue enhancement

Spine involvement

• Intramedullary lesions: T2 high, T1 low, patchy enhancement
• Often cervical/upper thoracic, fusiform swelling
• Leptomeningeal nodules along cord/roots common
• Dural-based masses rare but mimic meningioma/metastasis
• Vertebral lesions: lytic ± sclerotic mimics mets/myeloma

Treatment & prognosis

• Steroids first-line, methotrexate second-line
• Imaging response ≠ clinical response
• Frequent recurrence/progression → follow-up imaging mandatory

Radiology learning pearls

• Think neurosarcoid in: basal leptomeningeal enhancement + T2-dark enhancing masses + optic nerve or dural disease
• Always include with MS, TB, lymphoma in DDx of enhancing CNS inflammatory lesions
• Dural + leptomeningeal rarely coexist same region (arachnoid barrier clue)