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

Perineural Invasion and Spread in Common Abdominopelvic Diseases: Imaging Diagnosis and Clinical Significance

Malignancies and other diseases may spread by multiple pathways, including direct extension, hematogenous spread, or via lymphatic vessels. A less-well-understood route is the peripheral nervous system, which is known as perineural spread (PNS). In addition to accounting for pain and other neurologic symptoms, PNS affects both disease prognosis and management. Although PNS is commonly discussed in relation to head and neck tumors, there is emerging data regarding PNS in abdominopelvic malignancies and other conditions such as endometriosis. Due to improved contrast and spatial resolution, perineural invasion, a finding heretofore diagnosed only at pathologic examination, can be detected at CT, MRI, and PET/CT. PNS most commonly manifests as abnormal soft-tissue attenuation extending along neural structures, and diagnosis of it is aided by optimizing imaging parameters, understanding pertinent anatomy, and becoming familiar with the typical neural pathways of spread that largely depend on the disease type and location. In the abdomen, the celiac plexus is a central structure that innervates the major abdominal organs and is the principal route of PNS in patients with pancreatic and biliary carcinomas. In the pelvis, the lumbosacral plexus and inferior hypogastric plexus are the central structures and principal routes of PNS in patients with pelvic malignancies. Although the imaging findings of PNS may be subtle, a radiologic diagnosis can have a substantial effect on patient care. Knowledge of anatomy and known routes of PNS and optimizing imaging parameters is of utmost importance in providing key information for prognosis and treatment planning. © RSNA, 2023 Supplemental material and the slide presentation from the RSNA Annual Meeting are available for this article. Quiz questions for this article are available through the Online Learning Center.

Radiation-Induced Lumbosacral Plexopathy

Lumbosacral plexopathy (LSP) encompasses a group of disorders affecting post-ganglionic fibers derived from the L1-S4 roots. The differential diagnosis is challenging and includes other neuropathies of medullary, radicular, or peripheral origin. Defining the etiology is equally crucial, as LSP management relies on its cause. A thorough clinical history should address potential neoplastic disease (new-onset, progression, or relapse), diabetes mellitus, lumbar or pelvic trauma, and previous exposure to radiation. This is the case of a 78-year-old male, with a history of prostatic adenocarcinoma, treated with image-guided radiation therapy and hormone therapy five years before, with no evidence of relapse on follow-up. The patient presented with bilateral weakness, numbness, and paresthesia of lower limbs, gradually progressing over a three-month period, and followed by an acute worsening with inability to stand or walk. He also referred to distal mild edema, episodic hematuria, and urinary incontinence. Physical examination revealed paraparesis affecting proximal and distal leg muscles, along with bilateral hypoesthesia, impaired deep tendon reflexes, and proprioception below knee level. Pelvic, dorsal, and lumbosacral MRI excluded neoplastic lesions but identified somatic fracture of L5 without medullary or conus medullaris compromise. These findings did not explain the clinical picture. Further neurophysiologic studies characterized sensory-motor deficits as post-ganglionic, with specific spontaneous discharges of the muscle fibers, known as myokymia. These findings were consistent with radiation-induced LSP and were supported by MRI. Radiation-induced cystitis was also documented in pelvic MRI and urethral cystoscopy. This case highlights the clinical picture and differential diagnosis of radiation-induced LSP. Despite more typical symptoms and course, a neoplastic origin should always be carefully investigated and excluded. Radiation protocol should be carefully accessed, and its complications should not be overlooked, as they might cause severe morbidity.

Clinical Significance of Perineural Invasion by Prostate Cancer Detected on Needle Core Biopsy

OBJECTIVES

The clinical impact of the laterality of perineural invasion (PNI) by prostate cancer remains poorly understood. We herein compared radical prostatectomy (RP) findings and long-term oncologic outcomes in patients with prostate cancer with PNI in two prostate biopsy (PBx) sites.

METHODS

We retrospectively assessed 170 consecutive patients undergoing systematic sextant PBx where PNI had been detected in two of six PBx sites, followed by RP.

RESULTS

PNI occurred unilaterally in 140 (82.4%) cases and bilaterally in 30 (17.6%) cases. Compared with unilateral PNI, bilateral PNI was significantly associated with a higher number of cancer-positive sites and longer total tumor length on PBx. However, there were no significant differences in RP findings, including tumor grade/stage and tumor volume, between unilateral and bilateral PNI cohorts. Kaplan-Meier analysis revealed that patients with bilateral PNI had a significantly higher risk of disease progression after RP than those with unilateral PNI (P = .038). In multivariate analysis, bilateral PNI (vs unilateral PNI) showed significance for progression (hazard ratio, 2.281; P = .023).

CONCLUSIONS

In PBx specimens exhibiting PNI in two sextant sites, bilateral PNI was found to be associated with poorer prognosis as an independent predictor but not worse histopathologic features in RP specimens compared with unilateral PNI.

Lumbosacral plexopathy caused by the perineural spread of pelvic malignancies: clinical aspects and imaging patterns

BACKGROUND

Perineural spread (PNS) of tumors from pelvic malignancies is a rare phenomenon but constitutes an important differential diagnosis of lumbosacral plexopathy (LSP). Herein, we describe the clinical and imaging features of patients with LSP due to PNS of pelvic malignancies along with a literature review.

METHODS

We retrospectively reviewed 9 cases of LSP caused by PNS of pelvic malignancy between January 2006 and August 2021, and all clinical and imaging parameters were recorded in detail. Clinical symptoms and signs of patients were described and listed in the order in which they occurred. The results of imaging test were analyzed to describe specific findings in LSP caused by PNS.

RESULTS

This study enrolled nine adult patients (mean age, 50.1 years). Two cases initially presented as LSP and were later diagnosed with pelvic malignancy. Pain in the perianal or inguinal area preceded pain at the extremities in six patients. Neurogenic bladder or bowel symptoms developed in five patients. On the magnetic resonance imaging (MRI), the S1-S2 spinal nerve was most commonly involved, and S1 myotome weakness was more prominent in six patients than the other myotomes. One patient had an intradural extension. ¹⁸F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) and computed tomography (CT) showed abnormal signal intensity in six patients. No abnormality in ¹⁸F-FDG PET/CT was detected in the nervous structures in one patient. Only four patients survived until the last follow-up visit.

CONCLUSIONS

Though rare, physicians should always keep in mind the possibility of LSP due to the PNS in patients with pelvic malignancy. Thorough physical examination and history taking could provide clues for diagnosis. Pelvic MRI and ¹⁸F-FDG-PET/CT should be considered for patients with LSP to rule out neoplastic LSP.

Neoplastic nerve lesions

Though metastasis and malignant infiltration of the peripheral nervous system is relatively rare, physicians should have a familiarity with their presentations to allow for prompt diagnosis and initiation of treatment. This article will review the clinical presentations, diagnostic evaluation, and treatment of neoplastic involvement of the cranial nerves, nerve roots, peripheral nerves, and muscle. Due to the proximity of the neural structure traversing the skull base, metastasis to this region results in distinctive syndromes, most often associated with breast, lung, and prostate cancer. Metastatic involvement of the nerve roots is uncommon, apart from leptomeningeal carcinomatosis and bony metastasis with resultant nerve root damage, and is characterized by significant pain, weakness, and numbness of an extremity. Neoplasms may metastasize or infiltrate the brachial and lumbosacral plexuses resulting in progressive and painful sensory and motor deficits. Differentiating neoplastic involvement from radiation-induced injury is of paramount importance as it dictates treatment and prognosis. Neurolymphomatosis, due to malignant lymphocytic infiltration of the cranial nerves, nerve roots, plexuses, and peripheral nerves, deserves special attention given its myriad presentations, often mimicking acquired demyelinating neuropathies.

Atypical Metastases in the Abdomen and Pelvis From Biochemically Recurrent Prostate Cancer: 11C-Choline PET/CT Imaging With Multimodality Correlation

PET imaging with targeted radiotracers has become integral for mapping the location and burden of recurrent disease in patients with biochemical recurrence (BCR) of prostate cancer (PCa). PET with 11C-choline is part of the National Comprehensive Cancer Network and European Association of Urology guidelines for evaluation of BCR. With advances in PET technology, increasing use of targeted radiotracers, and improved survival of patients with BCR due to novel therapeutics, atypical sites of metastases are being increasingly encountered, challenging the conventional view that PCa rarely metastasizes beyond bones or lymph nodes. We describe such atypical metastases in the abdomen and pelvis on 11C-choline PET (including in the liver, pancreas, genital tract, urinary tract, peritoneum, and abdominal wall, as well as perineural spread), presenting multimodality imaging features and relevant imaging pitfalls. Given atypical metastases' inconsistent relationship with serum PSA and non-specific presenting symptoms, they are often first detected on imaging. Awareness of their imaging features is important as their detection impacts clinical management, patient counseling, prognosis, and clinical trial eligibility. Such awareness is particularly critical as the role of radiologists in the imaging and management of BCR will continue to increase given the expanding regulatory approvals of other targeted and theranostic radiotracers.

A novel mechanism for the formation and propagation of neural tumors and lesions through neural highways

By recognizing anatomic and radiologic patterns of rare and often misdiagnosed peripheral nerve tumors/lesions, we have defined mechanisms for the propagation of neural diseases. The novel concept of the nervous system serving as a complex system of "highways" driving the neural and perineural spread of these lesions is described in three examples: Intraneural dissection of joint fluid in intraneural ganglion cysts, perineural spread of cancer cells, and dissemination of unknown concentrations of neurotrophic/inhibitory factors for growth in hamartomas/choristomas of nerve. Further mapping of these pathways to identify the natural history of diseases, the spectrum of disease evolution, the role of genetic mutations, and how these neural pathways interface with the lymphatic, vascular, and cerebrospinal systems may lead to advances in targeted treatments.

Sacral plexus disorder caused by a wooden toothpick in the rectum

A 67-year-old man presented with a 2-month history of pain in his right buttock and lower limb. MRI depicted right L5/S1 lateral recess stenosis requiring surgical treatment; however, preoperative CT showed an approximately 7 cm long, thin, rod-shaped structure in the rectum, which was ultimately determined to be an accidentally ingested toothpick. It was removed surgically 6 days after diagnosis, because right leg pain worsened rapidly. The pain disappeared thereafter, and the symptoms have not recurred since. The pain might have been localised to the right buttock and posterior thigh in the early stages because the fine tip of the toothpick was positioned to the right of the anterior ramus of the S2 spinal nerve. Although sacral plexus disorder caused by a rectal foreign body is extremely rare, physicians should be mindful to avoid misdiagnosis.

Imaging of non-neurogenic peripheral nerve malignancy-a case series and systematic review

OBJECTIVE

To evaluate the frequency, clinico-pathologic and imaging features of malignant tumors in peripheral nerves which are of non-neurogenic origin (non-neurogenic peripheral nerve malignancy-PNM).

MATERIALS AND METHODS

We retrospectively reviewed our pathology database for malignant peripheral nerve tumors from 07/2014-07/2019 and performed a systematic review. Exclusion criteria were malignant peripheral nerve sheath tumor (MPNST). Clinico-pathologic and imaging features, apparent diffusion coefficient (ADC_min), and standard uptake values (SUV_max) are reported.

RESULTS

After exclusion of all neurogenic tumors (benign = 196, MPNST = 57), our search yielded 19 non-neurogenic PNMs (7%, n = 19/272), due to primary intraneural malignancy (16%, n = 3/19) and secondary perineural invasion from an adjacent malignancy (16%, n = 3/19) or metastatic disease (63%, n = 12/19). Non-neurogenic PNMs were located in the lumbosacral plexus/sciatic nerves (47%, n = 9/19), brachial plexus (32%, n = 6/19), femoral nerve (5%, n = 1/19), tibial nerve (5%, n = 1/19), ulnar nerve (5%, n = 1/19), and radial nerve (5%, n = 1/19). On MRI (n = 14/19), non-neurogenic PNM tended to be small (< 5 cm, n = 10/14), isointense to muscle on T1-W (n = 14/14), hyperintense on T2-WI (n = 12/14), with enhancement (n = 12/12), low ADC_min (0.5-0.7 × 10-3 mm²/s), and variable metabolic activity (SUV_max range 2.1-13.1). A target sign was absent (n = 14/14) and fascicular sign was rarely present (n = 3/14). Systematic review revealed 89 cases of non-neurogenic PNM.

CONCLUSION

Non-neurogenic PNMs account for 7% of PNT in our series and occur due to metastases and primary intraneural malignancy. Although non-neurogenic PNMs exhibit a non-specific MRI appearance, they lack typical signs of neurogenic tumors such as the target sign. Quantitative imaging features identified by DWI (low ADC) and F¹⁸-FDG PET/CT (high SUV) may be helpful clues to the diagnosis.

Circumdural extension of perineural spread leading to bilateral disease in neurolymphomatosis

INTRODUCTION

Patients with neurolymphomatosis (NL) often present with one primarily symptomatic limb but can be found to have bilateral upper or bilateral lower limb disease during workup. We sought to explain the finding of bilateral disease and understand if there was a connection to the initial, symptomatic side of disease.

METHODS

We reviewed imaging studies of patients with bilateral upper or bilateral lower limb disease from a previously published cohort from our institution, as well as more recent patients seen at our institution. We reviewed demographics (sex and age), clinical data (primary or secondary disease and biopsy-proven diagnosis), and imaging findings (primary involved nerve, contralateral nerve(s) affected, and location of circumdural extension).

RESULTS

We identified 8 cases with evidence of bilateral disease out of 22 cases of tumefactive NL. All eight cases were found to have circumdural extension of disease to the corresponding contralateral nerve.

CONCLUSION

We describe the pathomechanism of spread in our cases of bilateral upper or bilateral lower limb disease, where NL spreads along a dominant nerve toward the spinal canal and moves circumdurally to affect the corresponding contralateral nerve. We believe this information is useful to further understand the spread of NL, as well as offering important diagnostic and prognostic information for patients.

Mathematical model of perineural tumor spread: a pilot study

BACKGROUND

Perineural spread (PNS) of pelvic cancer along the lumbosacral plexus is an emerging explanation for neoplastic lumbosacral plexopathy (nLSP) and an underestimated source of patient morbidity and mortality. Despite the increased incidence of PNS, these patients are often times a clinical conundrum-to diagnose and to treat. Building on previous results in modeling glioblastoma multiforme (GBM), we present a mathematical model for predicting the course and extent of the PNS of recurrent tumors.

METHODS

We created three-dimensional models of perineurally spreading tumor along the lumbosacral plexus from consecutive magnetic resonance imaging scans of two patients (one each with prostate cancer and cervical cancer). We adapted and applied a previously reported mathematical model of GBM to progression of tumor growth along the nerves on an anatomical model obtained from a healthy subject.

RESULTS

We were able to successfully model and visualize perineurally spreading pelvic cancer in two patients; average growth rates were 60.7 mm/year for subject 1 and 129 mm/year for subject 2. The model correlated well with extent of PNS on MRI scans at given time points.

CONCLUSIONS

This is the first attempt to model perineural tumor spread and we believe that it provides a glimpse into the future of disease progression monitoring. Every tumor and every patient are different, and the possibility to report treatment response using a unified scale-as "days gained"-will be a necessity in the era of individualized medicine. We hope our work will serve as a springboard for future connections between mathematics and medicine.

Overview of metastatic disease of the central nervous system

In 2016, the American Society of Clinical Oncology reported that 1.7 million Americans were diagnosed with cancer; this number will rise to 2.3 million in the United States and 22 million worldwide in 2030. This rising need is being met by an explosion of new cancer therapies, including: immune checkpoint inhibitors, T-cell therapies, tumor vaccines, antiangiogenic therapies, and various targeted therapies. This armamentarium of targeted therapies has led to better systemic control of disease and longer patient overall survival (OS). The incidence of metastatic disease to the central nervous system (CNS) is rising as patients are living longer with these more effective systemic therapies. Prolonged OS allows increased time to develop CNS metastases. The CNS is also a sanctuary for metastatic tumor cells that are protected from full exposure to therapeutic concentrations of most anticancer agents by the blood-brain barrier, the tumor microenvironment, and immune system. In addition, CNS metastases often develop late in the course of the disease, so patients are frequently heavily pretreated, resulting in drug resistance. Although genomic profiling has led to more effective therapies for systemic disease, the same therapy may not be effective in treating CNS disease, not only due to failure of blood-brain barrier penetration, but from discordance between the molecular profile in systemic and CNS tumor.

Plexus and peripheral nerve metastasis

Cancer in the form of solid tumors, leukemia, and lymphoma can infiltrate and metastasize to the peripheral nervous system, including the cranial nerves, nerve roots, cervical, brachial and lumbosacral plexuses, and, rarely, the peripheral nerves. This review discusses the presentation, diagnostic evaluation, and treatment options for metastatic lesions to these components of the peripheral nervous system and is organized based on the anatomic distribution. As skull base metastases (also discussed in Chapter 14) result in cranial neuropathies, these will be covered in detail, as well as cancers that directly infiltrate the cranial nerves. Particular emphasis is placed on the clinical, imaging, and electrodiagnostic features that differentiate neoplastic plexopathies from radiation-induced plexopathies. Neurolymphomatosis, in which malignant lymphocytes invade the cranial nerves, nerve roots, brachial and lumbosacral plexuses, and peripheral nerves, is a rare manifestation of lymphoma and leukemia. Diagnoses of neurolymphomatosis are often missed or delayed given its varied presentations, resulting in poorer outcomes. Thus this disease will also be discussed in depth.

Neuromuscular complications in cancer

Cancer is becoming a treatable and even often curable disease. The neuromuscular system can be affected by direct tumor invasion or metastasis, neuroendocrine, metabolic, dysimmune/inflammatory, infections and toxic as well as paraneoplastic conditions. Due to the nature of cancer treatment, which frequently is based on a DNA damaging mechanism, treatment related toxic side effects are frequent and the correct identification of the causative mechanism is necessary to initiate the proper treatment. The peripheral nervous system is conventionally divided into nerve roots, the proximal nerves and plexus, the peripheral nerves (mono- and polyneuropathies), the site of neuromuscular transmission and muscle. This review is based on the anatomic distribution of the peripheral nervous system, divided into cranial nerves (CN), motor neuron (MND), nerve roots, plexus, peripheral nerve, the neuromuscular junction and muscle. The various etiologies of neuromuscular complications - neoplastic, surgical and mechanic, toxic, metabolic, endocrine, and paraneoplastic/immune - are discussed separately for each part of the peripheral nervous system.

Perineural spread in pelvic malignancies can be an alternate explanation for pelvic bony metastases rather than hematogenous spread. A report of two cases

We propose that pelvic malignancies can spread to bone and cause bony metastases using nerves as conduits. We reviewed two cases of pelvic malignancy with perineural spread of bladder cancer and prostate cancer. In a patient with prostate cancer, we identified six lesions that were positive on the (11)C-choline PET/CT scan and MRI; in a patient with bladder cancer, we identified two lesions positive on the (18)F-deoxy-glucose PET/CT scan and MRI. We carefully reviewed the imaging studies, and using established sclerotome maps we identified spinal nerves supplying each of eight pelvic bony lesions. All these spinal nerves showed evidence of tumor infiltration with extension toward the affected bones. We theorize that perineural tumor spread may serve as an additional mechanism of pelvic osseous metastases in pelvic malignancies.

Perineural spread of pelvic malignancies to the lumbosacral plexus and beyond: clinical and imaging patterns

OBJECT

Perineural spread along pelvic autonomie nerves has emerged as a logical, anatomical explanation for selected cases of neoplastic lumbosacral plexopathy (LSP) in patients with prostate, bladder, rectal, and cervical cancer. The authors wondered whether common radiological and clinical patterns shared by various types of pelvic cancer exist.

METHODS

The authors retrospectively reviewed their institutional series of 17 cases concluded as perineural tumor spread. All available history, physical examination, electrodiagnostic studies, biopsy data and imaging studies, evidence of other metastatic disease, and follow-up were recorded in detail. The series was divided into 2 groups: cases with neoplastic lumbosacral plexopathy confirmed by biopsy (Group A) and cases included based on imaging characteristics despite the lack of biopsy or negative biopsy results (Group B).

RESULTS

Group A comprised 10 patients (mean age 69 years); 9 patients were symptomatic and 1 was asymptomatic. The L5–S1 spinal nerves and sciatic nerve were most frequently involved. Three patients had intradural extension. Seven patients were alive at last follow-up. Group B consisted of 7 patients (mean age 64 years); 4 patients were symptomatic, 2 were asymptomatic, and 1 had only imaging available. The L5–S1 spinal nerves and the sciatic nerve were most frequently involved. No patients had intradural extension. Four patients were alive at last follow-up.

CONCLUSIONS

The authors provide a unifying theory to explain lumbosacral plexopathy in select cases of various pelvic neoplasms. The tumor cells can use splanchnic nerves as conduits and spread from the end organ to the lumbosacral plexus. Tumor can continue to spread along osseous and muscle nerve branches, resulting in muscle and bone “metastases.” Radiological studies show a reproducible, although nonspecific pattern, and the same applies to clinical presentation.

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.