Sarcoid: Neurosarcoidosis
Review of neurosarcoidosis. Prepare to succeed.
Show Notes/Study Guide:
Neurosarcoid: Neurosarcoid has been termed a “great mimicker” in the brain. The imaging appearances of neurosarcoid will commonly be nonspecific for sarcoid versus other entities so you need to remember differential diagnoses for various brain findings, many of the common hypothetical scenarios you may encounter on board exams are reviewed here. Remember that neurosarcoid can look like just about anything in the CNS. In general, if they show you a brain finding plus bilateral hilar/mediastinal lymphadenopathy sarcoid should be high on your differential on board exams.
Neurosarcoidosis of the brain:
What is the most common imaging manifestation of neurosarcoid in the CNS?
Probably multiple enhancing dural-based masses. Other common presentations include a thickened infundibular stalk, lesions (nodular and/or diffuse) along pial surface, cranial nerve
enlargement/enhancement, parenchymal masses.
What percentage of neurosarcoid patients will have an abnormal chest radiograph?
About 90% of neurosarcoid patients will have an abnormal chest radiograph at time of neurosarcoid presentation. On board exams if they show you a CNS finding plus an abnormal chest radiograph you need to consider sarcoidosis.
What percentage of patients with sarcoid will have symptomatic CNS involvement?
About 10% of sarcoid patients will have symptomatic CNS involvement. Up to perhaps 50% of all sarcoid patients will have CNS findings on autopsy.
What is the most affected cranial nerve in patients with neurosarcoidosis?
Facial nerve involvement is most common in patients with neurosarcoid. Bilateral facial nerve palsy should make you think of potential neurosarcoidosis, and this may happen in up to 1/3 of neurosarcoid patients.
Basilar meningitis on board exams should make you think of sarcoidosis versus what other entity?
Basilar meningitis should make you think of sarcoid versus tuberculosis. If you have basilar meningitis and hydrocephalus, think tuberculosis. Note that these entities can also cause secondary CNS vasculitis which would present on imaging with beading of the CNS vessels and possible focal vascular occlusion.
Sarcoid for the ABR Core Exam. Matt Covington, MD
Sarcoidosis can also present with diffuse dural enhancement. What are other differential considerations for diffuse dural enhancement?
Diffuse dural enhancement should make you think of intracranial hypotension (diffuse dural
enhancement, enlarged cavernous sinus, sagging brainstem), dural metastatic disease, post-operative state, sarcoidosis (typically somewhat nodular).
What are common entities you should consider when you see a thickened pituitary stalk on MRI?
Lymphocytic hypophysitis (idiopathic), eosinophilic granulomatosis, sarcoid, pituitary adenoma
What are common differential diagnoses for sellar/parasellar lesions you should remember for board exams?
A helpful mnemonic for sellar/parasellar lesions is “satchmoe”:
S-sarcoid, sellar tumor (adenomas)
A-aneurysm
T-teratoma or TB
C-craniopharyngioma, chordoma, cleft cyst (Rathke)
H-hypothalamic glioma, hamartoma of tuber cinereum
M-meningioma, metastasis
O-optic nerve glioma
E-eosinophilic granuloma, epidermoid/dermoid/teratoma
Sarcoid granulomas in the hypothalamus can cause diabetes insipidus. What are clinical manifestations of diabetes insipidus and what is the underlying mechanism of DI?
Classic symptoms of diabetes insipidus are polyuria and polydipsia due to resistance to or deficiency of antidiuretic hormone (ADH). With neurosarcoid this would be a central CNS process related to ADH deficiency rather than resistance which is due to peripheral causes (commonly chronic renal issues, pregnancy, lithium use)
Besides neurosarcoidosis what are other entities that can cause central diabetes insipidus?
Differential considerations for central DI include malignancy (craniopharyngioma and germinomas most common primary lesions, also metastatic disease), TB, LCH, trauma, neurosarcoid.
for the ABR Core Exam. Matt Covington, MD
Neurosarcoidosis is commonly treated with what therapy?
Corticosteroid therapy is a mainstay of neurosarcoid treatment. You may see decreased or resolved enhancement of CNS lesions following steroid treatment.
Neurosarcoidosis in the spine/spinal cord:
-Most common in elderly
-Most common in cervical or thoracic spinal cord
-Can look like just about anything—enhancement/enlargement of cord in any location
Neurosarcoidosis in head and neck:
-Sarcoid can involve basically any structure including eyes, ears, sinuses, airways, vessels, glands, etc.
What head and neck sites are most involved with sarcoid?
Orbital involvement probably most common. Most typically extra-ocular including optic nerve and/or lacrimal involvement, but ocular involvement/uveitis is also possible.
What is the panda sign?
Bilateral lacrimal, bilateral parotid, and physiologic nasopharyngeal uptake can show the “panda sign” on gallium 67 nuclear medicine imaging.
What are other differential considerations for the “panda sign”?
Besides sarcoidosis you should also think of Sjogren’s disease and lymphoma.
What are differential considerations for bilateral lacrimal gland enlargement?
Think Sjogren’s disease, sarcoid, lymphoma.
Sarcoid for the ABR Core Exam. Matt Covington, MD
Sarcoid involvement of the thyroid most commonly looks like what on imaging?
Thyroid enlargement with nonspecific thyroid nodules. May also have co-existent cervical
lymphadenopathy. Need biopsy to differentiate from other entities.
What is the top cause of calcified lymph nodes in the head and neck region?
The top cause is mycobacterium. Other common causes include sarcoid, treated lymphoma, metastases from various cancers including thyroid cancer.