Sarcoidosis is an inflammatory multisystem disorder of unknown etiology which may involve any part of the nervous system. The incidence of clinical involvement of the nervous system in a sarcoidosis population is estimated at approximately 5%.^1-5 As neurosarcoidosis may manifest in many different ways diagnosis may be complicated.^3,6-16 Any part of the nervous system can be attacked by sarcoidosis but cranial nerves, hypothalamus, and pituitary gland are more commonly involved.² One third of the neurosarcoidosis patients have multiple neurologic lesions. If neurological syndromes develop; in a patient with biopsy proven active systemic sarcoidosis, the diagnosis is usually easy. However, without biopsy evidence of sarcoidosis at other sites, nervous system sarcoidosis remains a difficult diagnosis.¹⁷ Neurological symptoms may also arise in patients with inactive sarcoidosis. In such situations neurosarcoidosis may occupy a high place in the list of differential diagnoses, but the histological evidence of granulomatous involvement of the neurological apparatus is still required in these cases.¹⁸ Neurosarcoidosis is rare; most papers report small numbers of patients or case reports and prospective studies on neurosarcoidosis are scarce.¹⁹ Consequently, evidence based recommendations are lacking.

Clinical features
Cranial neuropathy Cranial neuropathy is the most frequent neurological complication of sarcoidosis. 2 Cranial nerve palsy may be due to nerve granulomas, increased intracranial pressure or granulomatous basal meningitis. A peripheral seventh nerve palsy (Bell`s palsy) is the single most common cranial nerve lesion, 2 and is in fact the most frequent neurological manifestation of sarcoidosis overall. 20-25 Bilateral dysfunction occurs, both simultaneously and sequentially.  The optic nerve is the second most commonly affected cranial nerve. Read more

Epidemiology
Long-term clinical outcome of neurosarcoidosis has not been thoroughly evaluated. The low prevalence of the disease makes large, long-term follow-up studies difficult.  Furthermore, the natural history of the disease remains unclear because of therapeutic intervention. Read more

Differential diagnosis

Differential diagnosis of neurosarcoidosis is wide and includes multiple sclerosis, acute demyelinating encephalomyelitis (ADEM), infectious diseases (e.g. leprosy, tuberculosis, mycosis) other granulomatous diseases (e.g. Wegener`s granulomatosis, Churg Strauss syndrome, Lymphomatoid granulomatosis), tumors (e.g. neurolymphomas, gliomas, meningeomas), vasculopathies (vasculitis, Behçet disease), amyloidosis, and lymphocytic adenohypophysitis.

Ancillary investigations
Chest X-ray is abnormal in most of the patients with sarcoidosis and is the first sign that sarcoidosis is a possible cause of the neurological symptoms. However, in 10% of the sarcoidosis cases chest X-ray is normal. Additionally, serum ACE, gallium scan and bronchoalveolar lavage may be of help in supporting the diagnosis and establishing activity of the disease. 108 Whole body gallium scanning 109,110 or  FDG(fluorodeoxyglucose)-PETscanning 111 can be utilized in finding other suitable sites for biopsy. Read more

Therapy
Medication Therapeutical medical options for neurosarcoidosis are similar to that in sarcoidosis at other locations. 145 However, clear guidelines and indications as well as prospective controlled studies are not available in neurosarcoidosis and prospective multicenter studies are warranted. Corticosteroids represent the drugs of first choice. Usually an initial dose of 1 mg/kg/day suffice. In severe cases high doses of intravenously methylprednisolon may be used for a few days to obtain a high initial loading dose. Read more

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References
1. Luke RA, Stern BJ, Krumholz A, Johns CJ. Neurosarcoidosis: the long-term clinical course. Read more