Brachial Plexus Tumors Extending Into the Cervicothoracic Spine

Clinical Presentation and Imaging Findings

Initial symptoms depend on the level of the tumor, as well as the extent of motor deficit and spinal cord compression. Patients with high cervical lesions are more likely to present with sensory disturbances until the tumor is large enough to compress the spinal cord. Therefore large-diameter intraspinal tumors in the high cervical spine tend to be identified later than those in other areas. In cases of tumors of the thoracic spine, pain is the usual presenting complaint, although spinal cord compression can result in myelopathy. The extent of postoperative improvement of symptoms depends on several factors. Patients who have severe deficits preoperatively with myelopathy are less likely to improve. Patients with pain and paresthesia usually have pain relief after surgery and have a higher likelihood of improving after surgery. Some patients will experience a persistent or new sensory deficit, and in a minority of patients pain may worsen. Recurrence can occur in any patient, but the rate of recurrence in patients with neurofibromatosis type 2 (NF2) is higher, and repeated operations are complex. It is difficult to differentiate schwannomas from neurofibromas on the basis of imaging characteristics. Schwannomas are generally intradural and extramedullary. Only 15% are extradural or dumbbell shaped. They are generally small, but larger paraspinal extensions do occur. Most are in the thoracic region; they are equally distributed in the cervical and lumbar regions. Neurofibromas can be intradural extramedullary or paraspinal, and they can have different degrees of involvement of the spinal root, plexus, peripheral nerves, and end organs. They are usually associated with NF1 and tend to occur at the cervical level more often than the thoracic and lumbar levels. Their sizes vary, but these lesions are generally larger in the lumbar spine. Three types of neurofibromas are identified: localized, diffuse, and plexiform. Imaging characteristics are similar for schwannomas and neurofibromas. Bony findings may include a widened interpedicular distance, vertebral body erosion, or enlarged neural foramina. Myelography may reveal a block in cerebral spinal fluid flow. ^, Computed tomography (CT) often reveals well-marginated masses, and erosion and remodeling of adjacent bone. Cystic changes can appear, but rarely hemorrhaging or calcification. The best imaging modality for evaluation of these lesions is magnetic resonance imaging (MRI). On nonenhanced T1-weighted images, schwannomas usually appear isointense or hypointense relative to the spinal cord and nerve roots. On T2-weighted images, NSTs are usually hyperintense. Schwannomas, especially large ones, may show characteristic cystic changes with heterogeneity ( Fig. 50.2 ). The classic “target sign,” an enhancing rim with a central area of hypointensity, will occasionally be present. In postcontrast T1-weighted images, the lesions show intense enhancement, which may be uniform or heterogeneous, depending on the level of cystic changes. Most malignant paraspinal NSTs arise from plexiform neurofibromas. Approximately 5% of patients with NF1 develop malignant paraspinal NSTs. As opposed to other neurogenic tumors, characteristics that should raise the level of suspicion for malignancy include lesion size larger than 5 cm, enlarging tumors, ill-defined margins, invasion of fat planes, heterogeneity with central necrosis, intratumoral lobulation, and peritumoral edema. Additional MRI modalities such as diffusion-weighted imaging and apparent diffusion coefficient mapping are also being explored and show promise of further distinguishing malignant from benign NSTs.