Table 1 Possible phenotypic manifestation of NS and relative approximate frequency

Cranial neuropathy

 Optic nerve

 Facial nerve

 Vestibulocochlear nerve

50–75%

 7–35%

 11–25%

 3–17%

Granulomatous infiltration of cranial nerve nuclei or nerves can produce cranial neuropathy; a subacute and progressive course is typical, and a bilateral involvement is common. Heerfordt syndrome (parotitis, facial nerve palsy, low-grade fever, and anterior uveitis) is a rare manifestation

MRI often reveals leptomeningeal gadolinium enhancement nearby nerve emergency

Leptomeningitis (pachymeningitis)

10–20% (rare)

The involvement of most commonly leptomeninges, rarely pachymeninges, may determine a subacute meningitis syndrome that can persist, becoming a chronic meningitis

Radiologically, it is possible to observe lepto- or pachymeningeal gadolinium enhancement, which is often associated with a nodular component

Myelopathy

5–25%

The disease can affect the spinal cord via several mechanisms, including direct infiltration of spinal cord parenchyma, leptomeninges, or extraspinal tissue with compression of the spinal cord

Characteristic imaging findings include nodular and linear leptomeningeal contrast enhancement, eventually associated with intraparenchymal T2 hyperintensity. Longitudinally extensive myelitis (LETM; ≥ 3 segments) is relatively common

Parenchymal disease

 Mass lesion

 Encephalopathy

 > 50%

 5–10%

 5–10%

Intraparenchymal mass-like lesions develop in roughly 15% of cases and can produce seizures, focal deficit, and neuropsychiatric illness. MRI findings include T2 hyperintense and T1 isointense lesions that may or may not enhance

Nonspecific with matter T2/FLAIR hyperintense lesions without gadolinium enhancement are common and may be small and focal or larger, more diffuse lesions that resemble chronic vascular disease

Hydrocephalus

10%

Sellar disease

2–8%

Hypothalamic/pituitary involvement mostly determine anterior hypopituitarism (LH/FSH 89%, TSH 67%, GH 50%, and ACTH 49%), diabetes insipidus (65%), and hyperprolactinemia (49%)

MRI findings include thickening and contrast enhancement of the pituitary gland or stalk some

Peripheral neuropathy

2–86%

NS can be associated with both large and small fiber polyneuropathies or polyradiculoneuropathies with pure motor, sensory, or mixed sensorimotor features, including a Guillain–Barré-like syndrome. Symmetric chronic sensorimotor neuropathy with axonal features on electromyography (EMG) is the most common presentation. It also may be observed a mononeuritis multiplex with axonal features. Biopsy confirmation is required to support an eventual association of neuropathy with sarcoidosis is best

Vascular disease

Rare

Ischemic and hemorrhagic stroke rarely occur in patients with NS in case of small, medium, or large vessel vasculitis or phlebitis, a vascular compression from mass-like lesion (that can also determine venous sinus thrombosis)