Neurosarcoidosis

Neurosarcoidosis (sometimes shortened to neurosarcoid) refers to sarcoidosis, a condition of unknown cause featuring granulomas in various tissues, involving the central nervous system (brain and spinal cord). It can have many manifestations, but abnormalities of the cranial nerves (a group of twelve nerves supplying the head and neck area) are the most common. It may develop acutely, subacutely, and chronically.

Approximately 5-10% of people with sarcoidosis of other organs (e.g. lung) develop central nervous system involvement. Only 1% of people with sarcoidosis will have neurosarcoidosis alone without involvement of any other organs. Diagnosis can be difficult, with no test apart from biopsy being completely reliable. Treatment is with immunosuppression. The first case of sarcoidosis involving the nervous system was reported in 1948.

The diagnosis of neurosarcoidosis often is difficult. Definitive diagnosis can only be made by biopsy (surgically removing a tissue sample). Because of the risks associated with brain biopsies, they are avoided as much as possible. Other investigations that may be performed in any of the symptoms mentioned above are computed tomography (CT) or magnetic resonance imaging (MRI) of the brain, lumbar puncture, electroencephalography (EEG) and evoked potential (EP) studies. If the diagnosis of sarcoidosis is suspected, typical X-ray or CT appearances of the chest may make the diagnosis more likely; elevations in angiotensin-converting enzyme and calcium in the blood, too, make sarcoidosis more likely. In the past, the Kveim test was used to diagnose sarcoidosis. This now obsolete test had a high (85%) sensitivity, but required spleen tissue of a known sarcoidosis patient, an extract of which was injected into the skin of a suspected case.

Only biopsy of suspicious lesions in the brain or elsewhere is considered useful for a definitive diagnosis of neurosarcoid. This would demonstrate granulomas (collections of inflammatory cells) rich in epithelioid cells and surrounded by other immune system cells (e.g. plasma cells, mast cells). Biopsy may be performed to distinguish mass lesions from tumours (e.g. gliomas).

MRI with gadolinium enhancement is the most useful neuroimaging test. This may show enhancement of the pia mater or white matter lesions that may resemble the lesions seen in multiple sclerosis.


Left image: MRI findings (T1-weighted images) in a patient with neurosacoidosis showing thickening of infundibulum and both optic nerves (white signal marked with yellow arrows; width 6 mm).
Right image: MRI brain with contrast showing near resolution of enhancement after treatment.Lumbar puncture may demonstrate raised protein level, pleiocytosis (i.e. increased presence of both lymphocytes and neutrophil granulocytes) and oligoclonal bands. Various other tests (e.g. ACE level in CSF) have little added value.

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