Neuroradiology Case of the Week

Case 29

Brady Huang, Ramon R. de Guzman, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: A 36-year-old male who presented with convulsions. The patient’s history is notable for a diagnosis 6 months earlier of sarcoidosis with CNS involvement, presenting initially as a generalized seizure. CT and MRI of the head were requested to evaluate clinically worsening sarcoidosis.

Radiological Findings: CT demonstrates scattered areas of irregular enhancement throughout the gray and white matter bilaterally. There are areas of decreased attenuation surrounding these lesions, which represent vasogenic edema. The ventricles, sulci, and cisterns are within normal limits, and there is no intracranial hemorrhage, extraaxial fluid collection, mass effect, or midline shift (Figs. 1-2).
   On MR, there are multiple areas of high T2 signal in the subcortical white matter of both cerebral hemispheres (Fig. 3). The T1 contrast images show the same nodular and irregular lesions with increased signal intensity and surrounding areas of low signal intensity areas representing edema (Figs. 4-5).
   The chest radiograph is unremarkable as there is no evidence of hilar lymphadenopathy or infiltration of the lung fields typically seen with cases of sarcoidosis (Fig. 6).

Figure 1	Figure 2
Figure 3
Figure 4	Figure 5
Figure 6

Diagnosis: Neurosarcoidosis.

Discussion:
   Sarcoidosis is a multisystem granulomatous disease of unknown etiology, usually presenting with hilar adenopathy and pulmonary infiltration. This typical presentation is seen in about 90% of cases. Sarcoidosis can also present systemically, involving the skin, eye, lymph nodes, bones, and central nervous system. Histologically, the involved tissues classically show noncaseating granulomas composed of clustered epithelioid cells, often with giant or Langhans cells [1]. The diagnosis is one of exclusion as other diseases such as mycobacterial or fungal infections and berylliosis can also produce noncaseating granulomas [1]. The recommended clinical evaluation includes thorough history, physical exam, biopsy, chest radiography, pulmonary function testing, electrocardiography, ophthalmologic evaluation, and relevant biochemical laboratory tests [2].
   Neurosarcoidosis is rare and may present in the absence of systemic involvement [3]. Central nervous system involvement has been found in 5 to 16 percent of sarcoidosis cases at autopsy, however neurologic symptoms occur in about 3 to 9 percent of cases [4, 5, 6]. In those patients presenting with isolated neurologic symptoms, the most common manifestations appears to be optic or facial nerve disease. Additional manifestations include other cranial nerve palsies, spinal cord disease, brain-stem or cerebellar signs, hydrocephalus, myelopathy, meningitis, headache, seizures, hypothalamic and pituitary dysfunction, and cognitive decline [5, 7, 8]. Histopathologically, the CNS involvement is believed to be primarily leptomeningeal with inflammatory exudates extending from the subarachnoid space along the Virchow-Robin spaces into the brain parenchyma [5, 6, 9]. The Virchow-Robin spaces are relatively large at the base of the brain, which may correlate with the involvement of the basal leptomeninges, including the hypothalamus, pituitary, third ventricle, optic and other cranial nerves [5]. Parenchymal involvement of the brain occurs less frequently, but tends to occur in proximity to the surface of the brain, possibly by a similar mechanism [6]
   Radiologically, the granulomatous lesions are usually isointense relative to gray matter on T1 weighted images, and isointense to hyperintense on T2 weighted images. On CT, the mass lesions tend to appear hyperdense and enhance homogeneously. There may also be surrounding edema of the white matter. Contrast tends to enhance lesions of the meninges, hypothalamus, and periventricular areas [10]. NS may present as suprasellar masses with thickening of the infundibulum and optic chiasm [11]. Radiologically, intracranial sarcoidosis may mimic meningitis, meningiomas, lymphoma, and glioma [4, 10]. Spinal cord involvement is usually extramedullary and usually involves the cervical spine [12]. Since NS may mimic many other diseases, care must be taken to make the diagnosis of NS, and must be done so in the presence of other clinical information as stated above. In general, MRI has greater sensitivity than CT in revealing meningeal and diencephalic disease, however both are useful in delineating and localizing lesions [5, 10]. For detailed information on the differential for leptomeningeal, intraparenchymal, and cord involvement of sarcoidosis, please refer to the October 2002 case of the month.

References:

1. Cotran RS, Kumar V, Collins T. Robbins. Pathologic Basis of Disease, 6th Ed., W.B. Saunders Company, 1999. pp.734-735.
2. Newman LS, Rose CS, Maier LA. Sarcoidosis. N Engl J Med. 1997; 336:1224-34.
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5. Taveras JM. Neuroradiology, 3rd Ed. Williams & Wilkins. 1996. pp. 289-294.
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8. Greenberg JO. Neuroimaging. McGraw-Hill. 1999. pp.456-457.
9. Scott TF. Neurosarcoidosis: progress and clinical aspects. Neurology 1993; 43:8-12.
10. Zimmerman RA, Gibby WA, Carmody RF. Neuroimaging: Clinical& Physical Principles, 1st Ed., Springer Verlag Inc. 2000.
11. Christoforidis GA, Spickler EM, Recio MV, Mehta BM. MR of CNS sarcoidosis: correlation of imaging features to clinical symptoms and response to treatment. Am J Neuroradiol. 1999; 20:655-669.
12. Atlas SW. Magnetic Resonance Imaging of the Brain and Spine, 2nd Ed. Lippincott-Raven. 1996. pp.448-453.