May-June 2017
Peripheral Nervous System

Diffusivity Measurements Differentiate Benign from Malignant Lesions in Patients with Peripheral Neuropathy or Plexopathy

Yuh pic

Esther Yuh

In the multidisciplinary spine conference at our institution, mass-like lesions associated with peripheral nerves appear frequently on the case list. Whether lesions are incidentally discovered during the course of imaging for an unrelated indication or found during the work-up of mononeuropathy or plexopathy, a central clinical question is often whether to perform debulking or en bloc resection, percutaneous biopsy, chemotherapy or radiation, or serial imaging follow-up, based on the likely nature of the lesion.

Noting that other studies have demonstrated that diffusivity is inversely correlated with tumor cellularity and tumor grade in adult and pediatric brain tumors, head and neck masses, lymph nodes, and retroperitoneal soft-tissue masses,1-6 we sought to investigate this phenomenon in the context of mass-like or infiltrative lesions of the peripheral nerves. In our study, we included only MR neurograms that had been performed specifically for a clinical indication of peripheral mononeuropathy or brachial or lumbosacral plexopathy.

We found a statistically significant difference between ADC values of benign tumors (1.99 ± 0.60 x 10-3 mm2/sec), malignant tumors (0.69 ± 0.28 x 10-3 mm2/sec), and postradiation changes (2.37 ± 0.61 x 10-3 mm2/sec). Our results were consistent with a prior study7 of benign and malignant peripheral nerve tumors, in which tumor-like masses were found. In the current study, we extended the prior study’s scope by also examining infiltrative or mass-like postradiation changes of the peripheral nerves.

Mononeuropathies and plexopathies are most often due to trauma, nerve compression syndromes at characteristic anatomic locations, mass lesions, and postradiation changes. Unlike polyneuropathies, which are generally caused by systemic diseases and are diagnosed through clinical history, physical examination, laboratory studies, nerve conduction studies, and needle electromyography,8,9 mononeuropathies and plexopathies often require imaging for a definitive diagnosis. The pattern of diffusivity values that we and others have described within benign and malignant lesions may be helpful in determining whether to perform debulking or en bloc total resection and selecting patients for percutaneous tissue sampling and/or short-term clinical and imaging follow-up.

Subsequent to this study, we investigated the use of DTI to visualize nerve fibers and their spatial relationships to peripheral nerve tumors. Like the prior study, this investigation was driven and informed by interest from peripheral nerve surgeons at our institution. This study showed promising results for preoperative identification of nerve fiber location relative to the nerve tumor surface.10

References

  1. Nakayama T, Yoshimitsu K, Irie H, et al. Usefulness of the calculated apparent diffusion coefficient value in the differential diagnosis of retroperitoneal masses. J Magn Reson Imaging 2004:20:735–42, 10.1002/jmri.20149
  2. Thoeny HC, De Keyzer F, King AD. Diffusion-weighted MR imaging in the head and neck. Radiology 2012:263:19–32, 10.1148/radiol.11101821
  3. Abdel Razek AAK, Kandeel AY, Soliman N, et al. Role of diffusion-weighted echo-planar MR imaging in differentiation of residual or recurrent head and neck tumors and posttreatment changes. AJNR Am J Neuroradiol 2007:28:1146–52, 10.3174/ajnr.A0491
  4. Fornasa F, Nesoti MV, Bovo C, et al. Diffusion-weighted magnetic resonance imaging in the characterization of axillary lymph nodes in patients with breast cancer. J Magn Reson Imaging 2012:36:858–64, 10.1002/jmri.23706
  5. Yamasaki F, Kurisu K, Satoh K, et al. Apparent diffusion coefficient of human brain tumors at MR imaging. Radiology 2005:235:985–91, 10.1148/radiol.2353031338
  6. Kan P, Liu JK, Hedlund G, et al. The role of diffusion-weighted magnetic resonance imaging in pediatric brain tumors. Childs Nerv Syst 2006:22:1435–39, 10.1007/s00381-006-0229-x
  7. Chhabra A, Thakkar RS, Andreisek G, et al. Anatomic MR imaging and functional diffusion tensor imaging of peripheral nerve tumors and tumorlike conditions. AJNR Am J Neuroradiol 2013:34:802–07, 10.3174/ajnr.A3316
  8. Amato AA, Barohn RJ. Peripheral neuropathy. In: Longo DL, Fauci AS, Kasper DL, et al, eds. Harrison's principles of internal medicine. 18th ed. New York: McGraw-Hill; 2011:3448–72.
  9. England JD, Asbury AK. Peripheral neuropathy. Lancet 2004:363:2151–61, 10.1016/S0140-6736(04)16508-2
  10. Cage TA, Yuh EL, Hou SW, et al. Visualization of nerve fibers and their relationship to peripheral nerve tumors by diffusion tensor imaging. Neurosurg Focus 2015:39:E16, 10.3171/2015.6.FOCUS15235

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