Timothy C. Hain, MD. Page last modified: December 23, 2018
CNS sarcoidosis is a rare disorder in which noncaseating granulomas affect the brain. Only about 5% of patients with sarcoidosis have CNS lesions, but because the brain is a critical organ, CNS sarcoidosis causes a disproportionate amount of disability. Neurosarcoidosis was recently reviewed by a consortium that developed diagnostic criteria (see Stern et al, 2018).
The inner ear is seldom involved by sarcoidosis (about 50 cases had been described through 1990) According to Moine and Frachet (1990), deafness is fluctuant in 50% of all cases, bilateral, and most often associated with facial palsy and uveitis, the vestibular reflexes being reduced. It may be however, that we are just missing Sarcoid in the inner ear, as it is rare that anyone looks for it. Often, there is a search for Sarcoid in persons with bilateral vestibular loss.
Facial nerve palsy (e.g. Bell's palsy) is the most common manifestation. (Chen, R. C. and J. G. McLeod ; 1989;May M., Fria T, et al. ; 1981)).
Uveitis (inflammation of the iris) is possible. (Hybels, R. L. and D. H. Rice; 1976)
Vestibular involvement is rare but possible (e.g. von Brevern, M., T. Lempert, et al. (1997).
The author of this page has seen patients with pressure sensitivity accompanying neurosarcoidosis.
The cause of sarcoidosis is unknown, but it is generally treated with agents that reduce inflammation. Damage to the inner ear is thought to initially begin as a neuropathy, and then progress due to vascular damage (Babin and Liu, 1984; Moine and Frachet, 1990)
The pathologic hallmark of sarcoidosis is a noncaseating granulomatous inflammatory reaction. The granulomas may be at the surface of the brain, or within the brain where it can mimic a tumor (Stern et al, 2018). On biopsy, a fibrotic sarcoid lesion can look identical to a lesion from a chronic infection, and strong efforts should be made to exclude an infectious process. So in other words, pathology can be "compatable" with Sarcoid, but you still have to cross everything else off.
As mentioned above, this topic was recently reviewed by Stern et al, 2018. They offered the following staged criteria for neurosarcoidosis:
These are the tests that should be considered:
Ordinarily, an MRI of the brain or possibly other sites in the nervous system will be done, depending on the presentation.
Diagnosis is made through a combination of imaging studies showing enhancing lesions, sometimes involving the meninges, combined with other lesions in the body. A chest-Xray is the single most useful study. ACE levels may be elevated in the serum and IgG synthesis increased in the spinal fluid.
Most state that there MUST be a biopsy that documents noncaseating epitheliod cell granulomas. The lung is the most common site.
Chest imaging: "Abnormalities" are found in 90% of patients with sarcoidosis on CXR or CT scan of the chest. If mediastinal or hilar lymphadenopathy is found, Stern et al (2018) advises biopsy guided by ultrasound. One can search for extrapulmonary sarcoid using a whole-body FDG PET, which has higher spatial resolution than Gallium scanning (Stern et al, 2018).
CSF findings: According to Stern et al, CSF findings are not specific for sarcoid, but it helps to rule out infections and tumors. Pretty much anything goes here, and the CSF may be entirely normal in about 30% of patients. CSF pressure can be normal or elevated. There may be pleocytosis (57%), elevated protein(62%), low glucose, and oligoclonal bands (19%). The iGG index may be elevated (38%). Stern et al suggests getting viral PCR, seriologies (e.g. varicella zoster), checking for mycobacteria with PCR, stain and culture, as well as VDRL and Lyme disease.
ACE level: Regarding the ACE level, according to Stern et al, both the blood and CSF levels are insufficiently specific and sensitive to be of use. Serum lysozyme is also nonspecific and insentive.
Treament is difficult as in spite of corticosteroids and oral immunosuppresants, the disorder often progresses. Like many other CNS inflammatory disorders, it is thought that tumor necrosis factor -- TNF alpha, might play an important role.
TNF inhibitors including Infliximab have recentlhy been used with success (Morovan and Segal, 2009). Curiously, these drugs are also advocated in some types of autoimmune inner ear disease.