Benjamin M. Howe

Recurrent rectal cancer causing lumbosacral plexopathy with perineural spread to the spinal nerves and the sciatic nerve: an anatomic explanation.

Several groups have reported cases of rectal cancer with carcinomatous involvement of the lumbosacral plexus and sciatic, obturator, pudendal, or spinal nerves. To our best knowledge, clear examples of perineural tumor spread in rectal carcinoma have not yet been described. We retrospectively reviewed clinical data and imaging studies of three patients with primary or recurrent rectal cancer involving the lumbosacral plexus. Imaging studies included MRI and 18FDG PET/CT scans in all (n = 3) patients, histological samples were available in two (n = 2). Imaging studies demonstrated distinct features of tumor spread from the organ to the plexus and beyond in all cases (n = 3), histological specimens demonstrated perineural involvement thus supporting our theory (n = 2). We present these three cases of perineural tumor spread in rectal cancer as a proof of concept. We hypothesize that not only our cases, but other similar reported cases can be explained anatomically by extension of the rectal cancer to the inferior hypogastric plexus with perineural tumor spread to the lumbosacral plexus using the pelvic and sacral splanchnic nerves as conduits. Once the tumor reaches the lumbosacral plexus, it can continue to spread proximally or distally. We believe that perineural spread of colon cancer represents an important, under‐recognized mechanism of recurrence to neighboring major nerves in the pelvis. Clin. Anat. 28:136–143, 2015.

Perineural spread of cervical cancer to the sciatic nerve

In this report we present a patient with a recent diagnosis of cervical adenocarcinoma with progressive left lower extremity pain and weakness. MR imaging of the pelvis and subsequent FDG CT/PET were complementary in demonstrating abnormalities worrisome for perineural spread of malignancy, which was confirmed with an open fascicular biopsy of the sciatic nerve. We review the imaging and propose a mechanism of perineural spread to the sciatic nerve, which we believe is supported by the imaging in this case.

Current Concepts in MRI of Focal and Diffuse Malignancy of Bone Marrow

Bone marrow is a ubiquitous component of musculoskeletal imaging studies. The ability to identify and characterize pathology accurately in the bone marrow can be challenging given the broad spectrum of imaging features of normal bone marrow. Knowledge regarding the ability to differentiate normal from abnormal marrow has been enhanced with MR imaging with numerous techniques available to aid in distinguishing benign from malignant lesions in the bone marrow. T1-weighted fast spin echo (FSE) and fluid-sensitive sequences, fat-saturated T2-weighted FSE, and short tau inversion recovery provide valuable tools for the evaluation of a focal bone marrow lesion. Gadolinium enhancement, chemical shift, diffusion-weighted, and MR spectroscopy imaging are additional tools available for focal bone marrow lesion evaluation. Whole-body MRI and fluorodeoxyglucose positron emission tomography-computed tomography have evolved to be useful studies for staging and monitoring of therapeutic response in whole-body imaging. The relative advantages and disadvantages of the whole-body techniques are reviewed for metastases, myeloma, and lymphoma.

Recurrent prostatic adenocarcinoma with perineural spread to the lumbosacral plexus and sciatic nerve: comparing high resolution MRI with torso and endorectal coils and F-18 FDG and C-11 choline PET/CT

We present a patient with unexplained sciatica (radiating pain down the leg) found to have recurrent prostate adenocarcinoma within the sciatic nerve. High resolution MRI, especially use of an endorectal coil, improved visualization of the perineural spread of the disease. We believe that perineural spread resulting in sciatic symptoms in patients with known prostate adenocarcinoma may be an under-recognized phenomenon. The use of non-invasive modalities, high resolution endorectal coil MRI, and C-11 choline PET/CT can assist in the diagnosis of these patients.

Prostate cancer with perineural spread and dural extension causing bilateral lumbosacral plexopathy: case report

Perineural tumor spread in prostate cancer is emerging as a mechanism to explain select cases of neurological dysfunction and as a cause of morbidity and tumor recurrence. Perineural spread has been shown to extend from the prostate bed to the lumbosacral plexus and then distally to the sciatic nerve or proximally to the sacral and lumbar nerves and even intradurally. The authors present a case of a bilateral neoplastic lumbosacral plexopathy that can be explained anatomically as an extension of the same process: from one lumbosacral plexus to the contralateral one utilizing the dural sac as a bridge between the opposite sacral nerve roots. Their theory is supported by sequential progression of symptoms and findings on clinical examinations as well as high-resolution imaging (MRI and PET/CT scans). The neoplastic nature of the process was confirmed by a sciatic nerve fascicular biopsy. The authors believe that transmedian dural spread allows continuity of a neoplastic process from one side of the body to the other.

Deep ulnar intraneural ganglia in the palm.

BackgroundWhile extraneural ganglion cysts are common and well known, intraneural ganglia are rare and misunderstood.MaterialsWe describe a patient with an intraneural ganglion in an unusual location, the deep branch of the ulnar nerve in the palm. We confirmed a connection to the triquetral-hamate joint on preoperative high-resolution MRI and intraoperatively, and observed distal extension of the cyst, a variant pattern of propagation. We wondered if these intraneural cysts followed the principles of the unifying articular (synovial) theory rather than the de novo (degenerative) theory suggested by others. We reviewed patients with ulnar intraneural ganglia at the wrist for joint connections and the pattern of propagation.ResultsA total of 35 cases of ulnar intraneural ganglia at the wrist were identified, of which only 10 were joint connected. In 14 cases involving the deep ulnar branch, only 4 had joint connections. We hypothesized and proved that an unrecognized joint connection would be identified in the most recently reported case of a deep ulnar intraneural cyst in which a joint connection had not been identified. Propagation patterns supported descent in all cases involving the deep branch and proximal ascent in those of the main ulnar nerve (n = 18) or the dorsal cutaneous branch (n = 3). We believe that the orientation of the articular branches may play an important role in directionality in these intraneural cysts.ConclusionContrary to popular opinion, our analysis of the literature would suggest that intraneural ganglia at this rare site obey the common principles of the articular theory described at more common sites for intraneural ganglia.

Magnetic resonance imaging abnormalities of peripheral nerve and muscle are common in amyotrophic lateral sclerosis and share features with multifocal motor neuropathy.

Introduction: Magnetic resonance imaging (MRI) of peripheral nerve and muscle in patients with amyotrophic lateral sclerosis (ALS) may be performed to investigate alternative diagnoses, including multifocal motor neuropathy (MMN). MRI findings of peripheral nerve and muscle are not well described in these conditions, making interpretation of results difficult. Methods: We examined systematically the peripheral nerve and muscle MRI findings in patients with ALS (n = 60) and MMN (n = 8). Results: In patients with ALS and MMN, abnormal MRIs were common (85% and 75%, respectively), but did not correlate with disease severity. Peripheral nerve MRI abnormalities were similar in frequency (ALS 58%, MMN 63%), with most changes being of mild to moderate severity. Muscle MRI changes were more common in ALS (57% vs. 33%), and no muscle atrophy was seen in patients with MMN. Conclusion: MRI abnormalities of peripheral nerve and muscle in ALS and MMN are common and share some features. Muscle Nerve 52: 137–139, 2015

Perineural tumor spread of bladder cancer causing lumbosacral plexopathy: an anatomic explanation

We present two cases of biopsy-proven neoplastic lumbosacral plexopathy from perineural spread of bladder cancer: one patient presented with predominantly sciatic nerve involvement and the second predominantly with obturator nerve involvement. These two patterns of perineural spread from bladder cancer were supported by imaging in our cases and solidified by review of the literature. Based on the innervation of the bladder, we provide an anatomic explanation for this observation. To our best knowledge, such an anatomic, mechanistic basis for perineural tumor spread in bladder cancer has not yet been described.

Magnetic resonance imaging evidence for perineural spread of endometriosis to the lumbosacral plexus: report of 2 cases

Sciatic nerve endometriosis (EM) is a rare presentation of retroperitoneal EM. The authors present 2 cases of catamenial sciatica diagnosed as sciatic nerve EM. They propose that both cases can be explained by perineural spread of EM from the uterus to the sacral plexus along the pelvic autonomie nerves and then further distally to the sciatic nerve or proximally to the spinal nerves. This explanation is supported by MRI evidence in both cases. As a proof of concept, the authors retrieved and analyzed the original MRI studies of a case reported in the literature and found a similar pattern of spread. They believe that the imaging evidence of their institutional cases together with the outside case is a very compelling indication for perineural spread as a mechanism of EM of the nerve.

Malignant Involvement of the Peripheral Nervous System in Patients with Cancer: Multimodality Imaging and Pathologic Correlation

The clinical and imaging evaluation of peripheral neuropathies in patients with cancer is challenging. It is critically important to differentiate malignant invasion of the peripheral nervous system from nonmalignant causes, such as radiation-induced neuritis, neuropathy associated with chemotherapy, and inflammatory neuropathies. Contrast material-enhanced magnetic resonance (MR) imaging is the initial noninvasive test of choice; however, interpretation can be challenging when the anatomic features are distorted by prior surgery, radiation, or both. Fluorine 18 ((18)F)-fluorodeoxyglucose (FDG) positron emission tomography (PET)/computed tomography (CT) is an imaging adjunct to MR imaging that is particularly helpful for evaluating peripheral nerves because the metabolic activity depicted with (18)F-FDG PET/CT helps differentiate malignant from benign disease and assists in making certain management decisions. For example, sites of high (18)F-FDG activity in a peripheral nerve can be targeted to increase the diagnostic yield of a biopsy because malignant involvement of peripheral nerves can be patchy. Of note, (18)F-FDG PET/CT can show clinically unsuspected metastases elsewhere in the body. If cancer is found, (18)F-FDG PET/CT allows excellent assessment of treatment response. (18)F-FDG PET/CT is also useful in evaluating primary nerve sheath tumors in that such tumors with low metabolic activity on FDG PET/CT images are unlikely to be malignant, although the specificity is limited. It is essential to have a good understanding of the imaging characteristics of benign and malignant causes of peripheral neuropathy if (18)F-FDG PET/CT is to be used effectively for accurate diagnosis.