Imaging Review of Paraneoplastic Neurologic Syndromes

Abstract

Paraneoplastic syndromes are systemic reactions to neoplasms mediated by immunologic or hormonal mechanisms. The most well-recognized paraneoplastic neurologic syndrome, both clinically and on imaging, is limbic encephalitis. However, numerous additional clinically described syndromes affect the brain, spinal cord, and peripheral nerves. Many of these syndromes can have imaging findings that, though less well described, are important in making the correct diagnosis. Moreover, imaging in these syndromes frequently mimics more common pathology, which can be a diagnostic challenge for radiologists. Our goal is to review the imaging findings of paraneoplastic neurologic syndromes, including less well-known entities and atypical presentations of common entities. Specifically, we discuss limbic encephalitis, paraneoplastic cerebellar degeneration, paraneoplastic brain stem encephalitis, cranial neuropathy, myelitis, and polyneuropathy. We also demonstrate common diagnostic pitfalls that can be encountered when imaging these patients. ABBREVIATIONS: ANNA ¼ antineuronal nuclear autoantibody; PNS ¼ paraneoplastic neurologic syndrome; PCD ¼ paraneoplastic cerebellar degeneration P araneoplastic syndromes (PNSs) result from systemic reactions to neoplasms, often mediated by immunologic or hormonal mechanisms. PNSs include limbic encephalitis, encephalomyelitis, paraneoplastic cerebellar degeneration (PCD), brain stem encephalitis, polyneuropathy, stiff-person syndrome, retinopathy, myasthenia gravis, Lambert-Eaton myasthenic syndrome, and enteric nervous system dysfunction (Fig 1). These syndromes are often associated with serum or CSF positivity of onconeuronal or neuronal cell surface antibodies. Onconeuronal antibodies are more directly associated with underlying neoplasms and cause neuronal dysfunction by recruitment of cytotoxic T cells. In contrast, neuronal cell surface antibodies are less commonly associated with an underlying neoplasm and mediate pathology by directly binding to neurons. PNSs can occur in the presence or absence of paraneoplastic antibodies and are ultimately a clinical diagnosis. Conversely, antibody-mediated neurologic syndromes can occur in the absence of malignancy, though these are separately classified. 1 PARANEOPLASTIC NEUROLOGIC SYNDROMES BY ANATOMIC LOCATION Brain: Limbic Encephalitis Limbic encephalitis refers to inflammatory changes involving the limbic system, which includes the hippocampus, amygdala, hypothalamus, and cingulate cortex. Symptoms include mood and

Paraneoplastic Cerebellar Degeneration Associated with Anti-Yo Antibodies Appearing as a Leptomeningeal Cerebellar Carcinomatosis at MRI: a Case Report

“…As such, until the positive response in the serum of anti-Yo aAb, we remained very doubtful about a PCD diagnosis. Indeed, brain MRI, in most cases, is normal or shows few abnormalities in T2-Flair weighted sequences at the onset of disease which is followed by atrophy in later stages, while post-contrast enhanced lesions are anecdotal [4][5]. At this point however, our reservations around the diagnosis were dissolved as we did not notice an unfavourable clinical course.…”

“…Contrast enhancement of the cerebellar cortex is very rare, having been described only in a patient with non-Hodgkin's lymphoma and PCD with anti-Tr antibodies [4]. More recently, a case of nasopharyngeal carcinoma-associated anti-Yo-PCD showed a transient diffuse leptomeningeal enhancement on MRI imaging [5]. We present an unusual case of PCD with enhancing cerebellar lesions, leading to a possible diagnosis of cerebral carcinomatosis.…”

Neurological manifestation of cancer – paraneoplastic syndromes

“…Prophylactic measures include routine medical check-ups (especially neurological and oncological), notably when the patient recognizes subtle changes in his or her own body. Treatment involves therapies to reduce or slow down SCLC [19][20][21][22] Anti-Hu [19][20][21][22] NMDAR anti-N-methyl-Daspartate [25,26] teratoma (in young women) and possibly others [25,26] behavioural changes, memory impairment, speech disorders, seizures and disturbance of consciousness [25,26]…”

“…Levels of white blood cell count, protein count and dooponic gamma immunoglobulin (IgG) synthesis are increased, but neuroimaging is usually normal. Late neuroimaging studies reveal signs of extensive cerebellar atrophy after months or years [19,20].…”

“…Isolated cerebellar syndrome usually occurs in patients with Hodgkin's lymphoma and Tr/DNER antibodies or Yo antibodies in case of ovarian or breast cancer. Patients with PCD, small-cell lung cancer (SCLC) and Hu antibodies often have additional symptoms of a more diffuse encephalomyelitis [20][21][22].…”