Preoperative Tests

Nerve conduction and electromyography evaluations are not routinely undertaken in the management of peripheral nerve

Figure 74-2 Coronal T2- (A) and T1- (B) weighted gadolinium-enhanced magnetic resonance images of a lesion in the right buttock growing rapidly, producing severe neuropathic pain and progressive sciatic neuropathy, in a woman with neurofibromatosis 1. The tumor, which shows regions of signal inhomogeneity and enhancement, is located deep to the gluteal muscle mass adjacent to or involving the sciatic nerve.

Figure 74-2 Coronal T2- (A) and T1- (B) weighted gadolinium-enhanced magnetic resonance images of a lesion in the right buttock growing rapidly, producing severe neuropathic pain and progressive sciatic neuropathy, in a woman with neurofibromatosis 1. The tumor, which shows regions of signal inhomogeneity and enhancement, is located deep to the gluteal muscle mass adjacent to or involving the sciatic nerve.

tumors. The importance of the history and physical examination is further stressed because of the limitation of radiologic studies to always differentiate between a peripheral nerve tumor and other soft-tissue extremity masses. In addition, computed tomography (CT) or magnetic resonance imaging (MRI) cannot distinguish between the various subtypes of peripheral nerve tumors or reliably determine whether a lesion is benign or malignant.8,32,48,49 In general, MRI is the most useful and sensitive technique, often but not always revealing the nerve of origin (Figure 74-2). It is especially helpful in determining the relationship of the mass to adjacent anatomic structures that may be of relevance. Occasionally, remodeling of adjacent bone related to the slow progressive growth of the tumor, such as enlargement of neural foramina, can be better visualized on plain x-ray studies or CT scans, but MRI has become the investigation of choice. Ultrasound evaluation, because of its high degree of sensitivity, has an emerging role, but is still less often used.

The principal differential diagnoses of MPNST on imaging are soft tissue sarcoma, neurofibroma, and schwannoma. The rare lipomas and ganglion cysts that can mimic a peripheral nerve tumor are quite readily distinguished by their signal characteristics and association with a joint capsule, respectively, on MRI (see Chapter 73).

Whether a peripheral nerve tumor is a benign lesion or an MPNST cannot be definitely determined based on MRI or CT scan characteristics.8,32,48,49 A positive gallium scan was reported in one small series to be specific for these tumors, but follow-up studies involving larger numbers of cases are not available.32 Recent studies show positron-emission tomography (PET), particularly quantitative PET (high standard uptake values), appears to be a promising modality in distinguishing a region of sarcoma evolution in neurofibromas in the NF1 population.20 Regions of nonhomogeneous enhancement on CT or MRI, suggesting intratumoral necrosis or hemorrhage, may indicate a malignant aggressive neurogenic sarcoma, but such regions are also found in (especially larger) benign schwannomas and neu-rofibromas and in atypical (but not malignant) schwannomas. The suggestion of a malignant tumor originating from a peripheral nerve (MPNST) or secondary involvement of a nerve from an underlying primary neoplasm (e.g., Pancoast's tumor) comes from the history and general physical examination supported by other tests, such as chest x-ray (CXR) studies and CT. Rapid growth clinically or on follow-up MRI, increasing neurologic symptoms, or preexisting NF1 with a plexiform neurofibroma should lead to consideration of an MPNST. The evaluation for metastasis, which may include baseline blood tests, including liver function tests, CXR studies, and a bone scan with or without CT scans of the chest and abdomen, is important in the management of and less so for the diagnosis of MPNST. Because a majority of MPNSTs metastasize to the lungs, similar to other soft-tissue sarcomas, a CXR study, supplemented by CT of the chest if there are any suspicious lesions, is warranted in all cases. If a suspect lesion is identified in the lung, a needle biopsy should be performed to determine if metastasis has already occurred, because this will be a major factor toward determining the aggressiveness to be used in managing the primary tumor site. Of course, the presence of metastasis will be a major negative determinant of prognosis and requires the use of adjuvant irradiation and chemotherapy from the beginning. If a metastasis is identified in the chest or is suspected elsewhere from the general physical examination, further screening for metastasis with CT or MRI of the abdomen should be undertaken.

Peripheral Neuropathy Natural Treatment Options

Peripheral Neuropathy Natural Treatment Options

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