ARCOIDOSIS is a systemic, idiopathic granulomatous disease that involves the CNS in approximately 5% of patients. 16,22,24,26 Of the patients with neurological involvement, most present with CNS or cranial nerve man- ifestations. Peripheral nervous system manifestations are seen only rarely in patients with sarcoidosis and are usual- ly encountered later in the course of the disease. In one clin- ical series of patients with neurosarcoidosis, only 10% of patients had primarily peripheral nerve or muscle lesions, whereas the majority (90%) had primarily CNS or cranial nerve involvement. 19 Most patients who have peripheral nerve or muscle lesions only display the peripheral signs or symptoms after first exhibiting CNS involvement. Confirming the diagnosis of sarcoidosis is often difficult. Although CNS sarcoidosis can be diagnosed using contrast- enhanced MR imaging, 25 the diagnosis of PNS sarcoido- sis is more difficult. With conventional imaging modalities such as MR imaging and computerized tomography scan- ning providing a limited spatial and contrast resolution of the PNS, suspected peripheral nerve disease may require surgical exploration without the aid of imaging. Recently, the development of high-resolution MR peripheral nerve imaging sequences has provided clinicians with improved resolution of peripheral nerve structures. 3,8,17 The treatment of sarcoidosis is also subject to some con- troversy. The rarity of this disease makes randomized tri- als difficult. Most patients are treated with a combination of steroid and immunosuppressant medications. Although many patients respond to these modalities, often they are unable to tolerate the side effects associated with these drugs or do not respond to them. To date there have been several case reports of patients with CNS sarcoidosis that is refractory to steroid therapy who have received local radia- tion therapy, with varying degrees of success. 1,5,6,12,18,20,21,27,29 We report on the case of a young woman whose initial presentation was a foot drop. A diagnosis of sciatic nerve sarcoidosis was made after using MR peripheral nerve im- aging to guide an intraoperative biopsy procedure. Al- though the patient was maintained on high-dose steroid drugs for 2 years, she exhibited early signs of bone necro- sis. Local radiation therapy was performed, resulting in im- provement in her symptoms. Case Report History and Examination. This 22-year-old woman pre- sented to her primary care physician with numbness and burning in the sole of her right foot. The sensory changes progressed over 8 months to include the dorsum of her right foot and her right anterior calf. She subsequently experi- enced an unsteady gait and was referred for neurological consultation. On physical examination, sensation below the J Neurosurg 100:956–959, 2004 956 Sciatic nerve sarcoidosis: utility of magnetic resonance peripheral nerve imaging and treatment with radiation therapy Case report ANDREW T. DAILEY , M.D., MATTHEW T. RONDINA, M.D., JEANNETTE J. TOWNSEND, M.D., DENNIS C. SHRIEVE, M.D., PH.D., J. RICHARD BARINGER, M.D., AND KEVIN R. MOORE, M.D. Department of Neurosurgery, University of Washington, Seattle, Washington; Departments of Internal Medicine, and Pathology, University of Utah School of Medicine; and Departments of Radiation-Oncology, Neurology, and Radiology, University of Utah Health Sciences Center, Salt Lake City, Utah √ Sarcoidosis may involve both the central and peripheral nervous system, although peripheral nerve manifestations are usually seen late in the disease. In this report, the authors describe a case of sarcoidosis in a 22-year-old woman who pre- sented with a foot drop. Although results of conventional lumbar magnetic resonance (MR) imaging were normal, MR peripheral nerve imaging of the thigh showed a mass in the sciatic nerve indicating tumor. An intraoperative biopsy sam- ple revealed noncaseating granulomas consistent with sarcoid. The patient was treated with steroid drugs to control the manifestations of her disease but exhibited early signs of femoral bone necrosis, which required discontinuation of the ste- roids. She was then treated with local radiation therapy. At her 2-year follow-up visit the patient demonstrated relief of her symptoms and improvement on MR peripheral nerve imaging. This case demonstrates that sarcoidosis may present with peripheral nerve manifestations. The appearance of a diffusely swollen nerve on MR imaging should prompt clinicians to include sarcoidosis in the differential diagnosis and plan surgery accordingly. Patients who are not responsive to or who are unable to tolerate medical therapy may be treated with radiation therapy. KEY WORDS • sarcoidosis • peripheral nerve • radiation therapy • magnetic resonance peripheral nerve imaging S J. Neurosurg. / Volume 100 / May, 2004 Abbreviations used in this paper: CNS = central nervous system; MR = magnetic resonance; PNS = peripheral nervous system.